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Sample records for cerevisiae strain engineered

  1. Strain engineering of Saccharomyces cerevisiae for enhanced xylose metabolism.

    Science.gov (United States)

    Kim, Soo Rin; Park, Yong-Cheol; Jin, Yong-Su; Seo, Jin-Ho

    2013-11-01

    Efficient and rapid fermentation of all sugars present in cellulosic hydrolysates is essential for economic conversion of renewable biomass into fuels and chemicals. Xylose is one of the most abundant sugars in cellulosic biomass but it cannot be utilized by wild type Saccharomyces cerevisiae, which has been used for industrial ethanol production. Therefore, numerous technologies for strain development have been employed to engineer S. cerevisiae capable of fermenting xylose rapidly and efficiently. These include i) optimization of xylose-assimilating pathways, ii) perturbation of gene targets for reconfiguring yeast metabolism, and iii) simultaneous co-fermentation of xylose and cellobiose. In addition, the genetic and physiological background of host strains is an important determinant to construct efficient and rapid xylose-fermenting S. cerevisiae. Vibrant and persistent researches in this field for the last two decades not only led to the development of engineered S. cerevisiae strains ready for industrial fermentation of cellulosic hydrolysates, but also deepened our understanding of operational principles underlying yeast metabolism. PMID:23524005

  2. Improved xylose and arabinose utilization by an industrial recombinant Saccharomyces cerevisiae strain using evolutionary engineering

    DEFF Research Database (Denmark)

    Sanchez, R.G.; Karhumaa, Kaisa; Fonseca, C.;

    2010-01-01

    Background: Cost-effective fermentation of lignocellulosic hydrolysate to ethanol by Saccharomyces cerevisiae requires efficient mixed sugar utilization. Notably, the rate and yield of xylose and arabinose co-fermentation to ethanol must be enhanced. Results: Evolutionary engineering was used...... to improve the simultaneous conversion of xylose and arabinose to ethanol in a recombinant industrial Saccharomyces cerevisiae strain carrying the heterologous genes for xylose and arabinose utilization pathways integrated in the genome. The evolved strain TMB3130 displayed an increased consumption rate...... of our knowledge, this is the first report that characterizes the molecular mechanisms for improved mixed-pentose utilization obtained by evolutionary engineering of a recombinant S. cerevisiae strain. Increased transport of pentoses and increased activities of xylose converting enzymes contributed...

  3. Improved xylose and arabinose utilization by an industrial recombinant Saccharomyces cerevisiae strain using evolutionary engineering

    Directory of Open Access Journals (Sweden)

    Almeida João RM

    2010-06-01

    Full Text Available Abstract Background Cost-effective fermentation of lignocellulosic hydrolysate to ethanol by Saccharomyces cerevisiae requires efficient mixed sugar utilization. Notably, the rate and yield of xylose and arabinose co-fermentation to ethanol must be enhanced. Results Evolutionary engineering was used to improve the simultaneous conversion of xylose and arabinose to ethanol in a recombinant industrial Saccharomyces cerevisiae strain carrying the heterologous genes for xylose and arabinose utilization pathways integrated in the genome. The evolved strain TMB3130 displayed an increased consumption rate of xylose and arabinose under aerobic and anaerobic conditions. Improved anaerobic ethanol production was achieved at the expense of xylitol and glycerol but arabinose was almost stoichiometrically converted to arabitol. Further characterization of the strain indicated that the selection pressure during prolonged continuous culture in xylose and arabinose medium resulted in the improved transport of xylose and arabinose as well as increased levels of the enzymes from the introduced fungal xylose pathway. No mutation was found in any of the genes from the pentose converting pathways. Conclusion To the best of our knowledge, this is the first report that characterizes the molecular mechanisms for improved mixed-pentose utilization obtained by evolutionary engineering of a recombinant S. cerevisiae strain. Increased transport of pentoses and increased activities of xylose converting enzymes contributed to the improved phenotype.

  4. Key Process Conditions for Production of C4 Dicarboxylic Acids in Bioreactor Batch Cultures of an Engineered Saccharomyces cerevisiae Strain

    NARCIS (Netherlands)

    Zelle, R.M.; De Hulster, E.; Kloezen, W.; Pronk, J.T.; Van Maris, A.J.A.

    2009-01-01

    A recent effort to improve malic acid production by Saccharomyces cerevisiae by means of metabolic engineering resulted in a strain that produced up to 59 g liter−1 of malate at a yield of 0.42 mol (mol glucose)−1 in calcium carbonate-buffered shake flask cultures. With shake flasks, process paramet

  5. Key Process Conditions for Production of C4 Dicarboxylic Acids in Bioreactor Batch Cultures of an Engineered Saccharomyces cerevisiae Strain

    NARCIS (Netherlands)

    Zelle, R.M.; De Hulster, E.; Kloezen, W.; Pronk, J.T.; Van Maris, A.J.A.

    2010-01-01

    A recent effort to improve malic acid production by Saccharomyces cerevisiae by means of metabolic engineering resulted in a strain that produced up to 59 g liter(-1) of malate at a yield of 0.42 mol (mol glucose)(-1) in calcium carbonate-buffered shake flask cultures. With shake flasks, process par

  6. Increased resveratrol production in wines using engineered wine strains Saccharomyces cerevisiae EC1118 and relaxed antibiotic or auxotrophic selection.

    Science.gov (United States)

    Sun, Ping; Liang, Jing-Long; Kang, Lin-Zhi; Huang, Xiao-Yan; Huang, Jia-Jun; Ye, Zhi-Wei; Guo, Li-Qiong; Lin, Jun-Fang

    2015-01-01

    Resveratrol is a polyphenolic compound with diverse beneficial effects on human health. Red wine is the major dietary source of resveratrol but the amount that people can obtain from wines is limited. To increase the resveratrol production in wines, two expression vectors carrying 4-coumarate: coenzyme A ligase gene (4CL) from Arabidopsis thaliana and resveratrol synthase gene (RS) from Vitis vinifera were transformed into industrial wine strain Saccharomyces cerevisiae EC1118. When cultured with 1 mM p-coumaric acid, the engineered strains grown with and without the addition of antibiotics produced 8.249 and 3.317 mg/L of trans-resveratrol in the culture broth, respectively. Resveratrol content of the wine fermented with engineered strains was twice higher than that of the control, indicating that our engineered strains could increase the production of resveratrol during wine fermentation.

  7. Engineering industrial Saccharomyces cerevisiae strains for xylose fermentation and comparison for switchgrass conversion

    Science.gov (United States)

    Saccharomyces physiology and fermentation related properties vary broadly among industrial strains. In this study, six industrial strains of varied genetic background were engineered to ferment xylose. Aerobic growth rates on xylose were 0.040 h**-1 to 0.167 h**-1. Fermentation of xylose, glucose/xy...

  8. Engineering and two-stage evolution of a lignocellulosic hydrolysate-tolerant Saccharomyces cerevisiae strain for anaerobic fermentation of xylose from AFEX pretreated corn stover.

    Directory of Open Access Journals (Sweden)

    Lucas S Parreiras

    Full Text Available The inability of the yeast Saccharomyces cerevisiae to ferment xylose effectively under anaerobic conditions is a major barrier to economical production of lignocellulosic biofuels. Although genetic approaches have enabled engineering of S. cerevisiae to convert xylose efficiently into ethanol in defined lab medium, few strains are able to ferment xylose from lignocellulosic hydrolysates in the absence of oxygen. This limited xylose conversion is believed to result from small molecules generated during biomass pretreatment and hydrolysis, which induce cellular stress and impair metabolism. Here, we describe the development of a xylose-fermenting S. cerevisiae strain with tolerance to a range of pretreated and hydrolyzed lignocellulose, including Ammonia Fiber Expansion (AFEX-pretreated corn stover hydrolysate (ACSH. We genetically engineered a hydrolysate-resistant yeast strain with bacterial xylose isomerase and then applied two separate stages of aerobic and anaerobic directed evolution. The emergent S. cerevisiae strain rapidly converted xylose from lab medium and ACSH to ethanol under strict anaerobic conditions. Metabolomic, genetic and biochemical analyses suggested that a missense mutation in GRE3, which was acquired during the anaerobic evolution, contributed toward improved xylose conversion by reducing intracellular production of xylitol, an inhibitor of xylose isomerase. These results validate our combinatorial approach, which utilized phenotypic strain selection, rational engineering and directed evolution for the generation of a robust S. cerevisiae strain with the ability to ferment xylose anaerobically from ACSH.

  9. Engineering and two-stage evolution of a lignocellulosic hydrolysate-tolerant Saccharomyces cerevisiae strain for anaerobic fermentation of xylose from AFEX pretreated corn stover.

    Science.gov (United States)

    Parreiras, Lucas S; Breuer, Rebecca J; Avanasi Narasimhan, Ragothaman; Higbee, Alan J; La Reau, Alex; Tremaine, Mary; Qin, Li; Willis, Laura B; Bice, Benjamin D; Bonfert, Brandi L; Pinhancos, Rebeca C; Balloon, Allison J; Uppugundla, Nirmal; Liu, Tongjun; Li, Chenlin; Tanjore, Deepti; Ong, Irene M; Li, Haibo; Pohlmann, Edward L; Serate, Jose; Withers, Sydnor T; Simmons, Blake A; Hodge, David B; Westphall, Michael S; Coon, Joshua J; Dale, Bruce E; Balan, Venkatesh; Keating, David H; Zhang, Yaoping; Landick, Robert; Gasch, Audrey P; Sato, Trey K

    2014-01-01

    The inability of the yeast Saccharomyces cerevisiae to ferment xylose effectively under anaerobic conditions is a major barrier to economical production of lignocellulosic biofuels. Although genetic approaches have enabled engineering of S. cerevisiae to convert xylose efficiently into ethanol in defined lab medium, few strains are able to ferment xylose from lignocellulosic hydrolysates in the absence of oxygen. This limited xylose conversion is believed to result from small molecules generated during biomass pretreatment and hydrolysis, which induce cellular stress and impair metabolism. Here, we describe the development of a xylose-fermenting S. cerevisiae strain with tolerance to a range of pretreated and hydrolyzed lignocellulose, including Ammonia Fiber Expansion (AFEX)-pretreated corn stover hydrolysate (ACSH). We genetically engineered a hydrolysate-resistant yeast strain with bacterial xylose isomerase and then applied two separate stages of aerobic and anaerobic directed evolution. The emergent S. cerevisiae strain rapidly converted xylose from lab medium and ACSH to ethanol under strict anaerobic conditions. Metabolomic, genetic and biochemical analyses suggested that a missense mutation in GRE3, which was acquired during the anaerobic evolution, contributed toward improved xylose conversion by reducing intracellular production of xylitol, an inhibitor of xylose isomerase. These results validate our combinatorial approach, which utilized phenotypic strain selection, rational engineering and directed evolution for the generation of a robust S. cerevisiae strain with the ability to ferment xylose anaerobically from ACSH. PMID:25222864

  10. Engineering and Two-Stage Evolution of a Lignocellulosic Hydrolysate-Tolerant Saccharomyces cerevisiae Strain for Anaerobic Fermentation of Xylose from AFEX Pretreated Corn Stover

    OpenAIRE

    Parreiras, Lucas S.; Rebecca J Breuer; Avanasi Narasimhan, Ragothaman; Alan J Higbee; La Reau, Alex; Tremaine, Mary; Qin, Li; Willis, Laura B.; Bice, Benjamin D.; Bonfert, Brandi L.; Pinhancos, Rebeca C.; Balloon, Allison J.; Uppugundla, Nirmal; Liu, Tongjun; Li, Chenlin

    2014-01-01

    The inability of the yeast Saccharomyces cerevisiae to ferment xylose effectively under anaerobic conditions is a major barrier to economical production of lignocellulosic biofuels. Although genetic approaches have enabled engineering of S. cerevisiae to convert xylose efficiently into ethanol in defined lab medium, few strains are able to ferment xylose from lignocellulosic hydrolysates in the absence of oxygen. This limited xylose conversion is believed to result from small molecules genera...

  11. Anaplerotic Role for Cytosolic Malic Enzyme in Engineered Saccharomyces cerevisiae Strains

    NARCIS (Netherlands)

    Zelle, R.M.; Harrison, J.C.; Pronk, J.T.; Van Maris, A.J.A.

    2010-01-01

    Malic enzyme catalyzes the reversible oxidative decarboxylation of malate to pyruvate and CO2. The Saccharomyces cerevisiae MAE1 gene encodes a mitochondrial malic enzyme whose proposed physiological roles are related to the oxidative, malate-decarboxylating reaction. Hitherto, the inability of pyru

  12. Genetic engineering of industrial Saccharomyces cerevisiae strains using a selection/counter-selection approach.

    Science.gov (United States)

    Kutyna, Dariusz R; Cordente, Antonio G; Varela, Cristian

    2014-01-01

    Gene modification of laboratory yeast strains is currently a very straightforward task thanks to the availability of the entire yeast genome sequence and the high frequency with which yeast can incorporate exogenous DNA into its genome. Unfortunately, laboratory strains do not perform well in industrial settings, indicating the need for strategies to modify industrial strains to enable strain development for industrial applications. Here we describe approaches we have used to genetically modify industrial strains used in winemaking.

  13. One-pot production of fructooligosaccharides by a Saccharomyces cerevisiae strain expressing an engineered invertase.

    Science.gov (United States)

    Marín-Navarro, Julia; Talens-Perales, David; Polaina, Julio

    2015-03-01

    We describe a simple, efficient process for the production of 6-kestose, a trisaccharide with well-documented prebiotic properties. A key factor is the use of a yeast transformant expressing an engineered version of Saccharomyces invertase with enhanced transfructosylating activity. When the yeast transformant was grown with 30 % sucrose as the carbon source, 6-kestose accumulated up to ca. 100 g/L in the culture medium. The 6-kestose yield was significantly enhanced (up to 200 g/L) using a two-stage process carried out in the same flask. In the first stage, the culture was grown in 30 % sucrose at physiological temperature (30 °C) to allow overexpression of the invertase. In the second stage, sucrose was added to the culture at high concentration (60 %) and the temperature shifted to 50 °C. In both cases, 6-kestose was synthesized with high specificity, representing more than 95 % of total FOS. PMID:25547837

  14. Improving the productivity of S-adenosyl-l-methionine by metabolic engineering in an industrial Saccharomyces cerevisiae strain.

    Science.gov (United States)

    Zhao, Weijun; Hang, Baojian; Zhu, Xiangcheng; Wang, Ri; Shen, Minjie; Huang, Lei; Xu, Zhinan

    2016-10-20

    S-Adenosyl-l-methionine (SAM) is an important metabolite having prominent roles in treating various diseases. In order to improve the production of SAM, the regulation of three metabolic pathways involved in SAM biosynthesis were investigated in an industrial yeast strain ZJU001. GLC3 encoded glycogen-branching enzyme (GBE), SPE2 encoded SAM decarboxylase, as well as ERG4 and ERG6 encoded key enzymes in ergosterol biosynthesis, were knocked out in ZJU001 accordingly. The results indicated that blocking of either glycogen pathway or SAM decarboxylation pathway could improve the SAM accumulation significantly in ZJU001, while single disruption of either ERG4 or ERG6 gene had no obvious effect on SAM production. Moreover, the double mutant ZJU001-GS with deletion of both GLC3 and SPE2 genes was also constructed, which showed further improvement of SAM accumulation. Finally, SAM2 was overexpressed in ZJU001-GS to give the best SAM-producing recombinant strain ZJU001-GS-SAM2, in which 12.47g/L SAM was produced by following our developed pseudo-exponential fed-batch cultivation strategy, about 81.0% increase comparing to its parent strain ZJU001. The present work laid a solid base for large-scale SAM production with the industrial Saccharomyces cerevisiae strain.

  15. Progress in Metabolic Engineering of Saccharomyces cerevisiae

    OpenAIRE

    Nevoigt, Elke

    2008-01-01

    Summary: The traditional use of the yeast Saccharomyces cerevisiae in alcoholic fermentation has, over time, resulted in substantial accumulated knowledge concerning genetics, physiology, and biochemistry as well as genetic engineering and fermentation technologies. S. cerevisiae has become a platform organism for developing metabolic engineering strategies, methods, and tools. The current review discusses the relevance of several engineering strategies, such as rational and inverse metabolic...

  16. Growth-rate dependency of de novo resveratrol production in chemostat cultures of an engineered Saccharomyces cerevisiae strain

    NARCIS (Netherlands)

    Vos, T.; De la Torre Cortes, P.; Van Gulik, W.M.; Pronk, J.T.; Daran-Lapujade, P.A.S.

    2015-01-01

    Introduction: Saccharomyces cerevisiae has become a popular host for production of non-native compounds. The metabolic pathways involved generally require a net input of energy. To maximize the ATP yield on sugar in S. cerevisiae, industrial cultivation is typically performed in aerobic, sugar-limit

  17. Engineering of a Nepetalactol-Producing Platform Strain of Saccharomyces cerevisiae for the Production of Plant Seco-Iridoids.

    Science.gov (United States)

    Campbell, Alex; Bauchart, Philippe; Gold, Nicholas D; Zhu, Yun; De Luca, Vincenzo; Martin, Vincent J J

    2016-05-20

    The monoterpene indole alkaloids (MIAs) are a valuable family of chemicals that include the anticancer drugs vinblastine and vincristine. These compounds are of global significance-appearing on the World Health Organization's list of model essential medicines-but remain exorbitantly priced due to low in planta levels. Chemical synthesis and genetic manipulation of MIA producing plants such as Catharanthus roseus have so far failed to find a solution to this problem. Synthetic biology holds a potential answer, by building the pathway into more tractable organisms such as Saccharomyces cerevisiae. Recent work has taken the first steps in this direction by producing small amounts of the intermediate strictosidine in yeast. In order to help improve on these titers, we aimed to optimize the early biosynthetic steps of the MIA pathway to the metabolite nepetalactol. We combined a number of strategies to create a base strain producing 11.4 mg/L of the precursor geraniol. We also show production of the critical intermediate 10-hydroxygeraniol and demonstrate nepetalactol production in vitro. Lastly we demonstrate that activity of the iridoid synthase toward the intermediates geraniol and 10-hydroxygeraniol results in the synthesis of the nonproductive intermediates citronellol and 10-hydroxycitronellol. This discovery has serious implications for the reconstruction of the MIA in heterologous organisms. PMID:26981892

  18. Engineering of a Nepetalactol-Producing Platform Strain of Saccharomyces cerevisiae for the Production of Plant Seco-Iridoids.

    Science.gov (United States)

    Campbell, Alex; Bauchart, Philippe; Gold, Nicholas D; Zhu, Yun; De Luca, Vincenzo; Martin, Vincent J J

    2016-05-20

    The monoterpene indole alkaloids (MIAs) are a valuable family of chemicals that include the anticancer drugs vinblastine and vincristine. These compounds are of global significance-appearing on the World Health Organization's list of model essential medicines-but remain exorbitantly priced due to low in planta levels. Chemical synthesis and genetic manipulation of MIA producing plants such as Catharanthus roseus have so far failed to find a solution to this problem. Synthetic biology holds a potential answer, by building the pathway into more tractable organisms such as Saccharomyces cerevisiae. Recent work has taken the first steps in this direction by producing small amounts of the intermediate strictosidine in yeast. In order to help improve on these titers, we aimed to optimize the early biosynthetic steps of the MIA pathway to the metabolite nepetalactol. We combined a number of strategies to create a base strain producing 11.4 mg/L of the precursor geraniol. We also show production of the critical intermediate 10-hydroxygeraniol and demonstrate nepetalactol production in vitro. Lastly we demonstrate that activity of the iridoid synthase toward the intermediates geraniol and 10-hydroxygeraniol results in the synthesis of the nonproductive intermediates citronellol and 10-hydroxycitronellol. This discovery has serious implications for the reconstruction of the MIA in heterologous organisms.

  19. Metabolic pathway engineering based on metabolomics confers acetic and formic acid tolerance to a recombinant xylose-fermenting strain of Saccharomyces cerevisiae

    Directory of Open Access Journals (Sweden)

    Ishii Jun

    2011-01-01

    Full Text Available Abstract Background The development of novel yeast strains with increased tolerance toward inhibitors in lignocellulosic hydrolysates is highly desirable for the production of bio-ethanol. Weak organic acids such as acetic and formic acids are necessarily released during the pretreatment (i.e. solubilization and hydrolysis of lignocelluloses, which negatively affect microbial growth and ethanol production. However, since the mode of toxicity is complicated, genetic engineering strategies addressing yeast tolerance to weak organic acids have been rare. Thus, enhanced basic research is expected to identify target genes for improved weak acid tolerance. Results In this study, the effect of acetic acid on xylose fermentation was analyzed by examining metabolite profiles in a recombinant xylose-fermenting strain of Saccharomyces cerevisiae. Metabolome analysis revealed that metabolites involved in the non-oxidative pentose phosphate pathway (PPP [e.g. sedoheptulose-7-phosphate, ribulose-5-phosphate, ribose-5-phosphate and erythrose-4-phosphate] were significantly accumulated by the addition of acetate, indicating the possibility that acetic acid slows down the flux of the pathway. Accordingly, a gene encoding a PPP-related enzyme, transaldolase or transketolase, was overexpressed in the xylose-fermenting yeast, which successfully conferred increased ethanol productivity in the presence of acetic and formic acid. Conclusions Our metabolomic approach revealed one of the molecular events underlying the response to acetic acid and focuses attention on the non-oxidative PPP as a target for metabolic engineering. An important challenge for metabolic engineering is identification of gene targets that have material importance. This study has demonstrated that metabolomics is a powerful tool to develop rational strategies to confer tolerance to stress through genetic engineering.

  20. Evolutionary engineering of Saccharomyces cerevisiae for efficient aerobic xylose consumption

    DEFF Research Database (Denmark)

    Scalcinati, Gionata; Otero, José Manuel; Van Vleet, Jennifer R. H.;

    2012-01-01

    Industrial biotechnology aims to develop robust microbial cell factories, such as Saccharomyces cerevisiae, to produce an array of added value chemicals presently dominated by petrochemical processes. Xylose is the second most abundant monosaccharide after glucose and the most prevalent pentose...... sugar found in lignocelluloses. Significant research efforts have focused on the metabolic engineering of S. cerevisiae for fast and efficient xylose utilization. This study aims to metabolically engineer S. cerevisiae, such that it can consume xylose as the exclusive substrate while maximizing carbon...... of this strain was employed to further elucidate the observed physiology confirms a strongly up-regulated glyoxylate pathway enabling respiratory metabolism. The resulting strain is a desirable platform for the industrial production of biomass-related products using xylose as a sole carbon source....

  1. A coniferyl aldehyde dehydrogenase gene from Pseudomonas sp. strain HR199 enhances the conversion of coniferyl aldehyde by Saccharomyces cerevisiae.

    Science.gov (United States)

    Adeboye, Peter Temitope; Olsson, Lisbeth; Bettiga, Maurizio

    2016-07-01

    The conversion of coniferyl aldehyde to cinnamic acids by Saccharomyces cerevisiae under aerobic growth conditions was previously observed. Bacteria such as Pseudomonas have been shown to harbor specialized enzymes for converting coniferyl aldehyde but no comparable enzymes have been identified in S. cerevisiae. CALDH from Pseudomonas was expressed in S. cerevisiae. An acetaldehyde dehydrogenase (Ald5) was also hypothesized to be actively involved in the conversion of coniferyl aldehyde under aerobic growth conditions in S. cerevisiae. In a second S. cerevisiae strain, the acetaldehyde dehydrogenase (ALD5) was deleted. A prototrophic control strain was also engineered. The engineered S. cerevisiae strains were cultivated in the presence of 1.1mM coniferyl aldehyde under aerobic condition in bioreactors. The results confirmed that expression of CALDH increased endogenous conversion of coniferyl aldehyde in S. cerevisiae and ALD5 is actively involved with the conversion of coniferyl aldehyde in S. cerevisiae. PMID:27070284

  2. Automated Yeast Transformation Protocol to Engineer S. cerevisiae Strains for Cellulosic Ethanol Production with Open Reading Frames that Express Proteins Binding to Xylose Isomerase Identified using Robotic Two-hybrid Screen

    Science.gov (United States)

    Commercialization of fuel ethanol production from lignocellulosic biomass has focused on engineering the glucose-fermenting industrial yeast Saccharomyces cerevisiae to utilize pentose sugars. Since S. cerevisiae naturally metabolizes xylulose, one approach involves introducing xylose isomerase (XI...

  3. Glycerol Overproduction by Engineered Saccharomyces cerevisiae Wine Yeast Strains Leads to Substantial Changes in By-Product Formation and to a Stimulation of Fermentation Rate in Stationary Phase

    OpenAIRE

    Remize, F.; Roustan, J. L.; Sablayrolles, J. M.; P. Barre; Dequin, S.

    1999-01-01

    Six commercial wine yeast strains and three nonindustrial strains (two laboratory strains and one haploid strain derived from a wine yeast strain) were engineered to produce large amounts of glycerol with a lower ethanol yield. Overexpression of the GPD1 gene, encoding a glycerol-3-phosphate dehydrogenase, resulted in a 1.5- to 2.5-fold increase in glycerol production and a slight decrease in ethanol formation under conditions simulating wine fermentation. All the strains overexpressing GPD1 ...

  4. Linking Genotype and Phenotype of Saccharomyces cerevisiae Strains Reveals Metabolic Engineering Targets and Leads to Triterpene Hyper-Producers

    DEFF Research Database (Denmark)

    Madsen, Karina Marie; Udatha, Gupta D. B. R. K.; Semba, Saori;

    2011-01-01

    S288C strain, we implemented a strategy for the construction of a beta-amyrin production platform. The genes Erg8, Erg9 and HFA1 contained non-silent SNPs that were computationally analyzed to evaluate the changes that cause in the respective protein structures. Subsequently, Erg8, Erg9 and HFA1...

  5. Aerobic physiology of redox-engineered Saccharomyces cerevisiae strains modified in the ammonium assimilation for increased NADPH availability

    DEFF Research Database (Denmark)

    Santos, Maria Margarida M. dos; Thygesen, G.; Kotter, P.;

    2003-01-01

    Recombinant strains altered in the ammonium assimilation pathways were constructed with the purpose of increasing NADPH availability. The NADPH-dependent glutamate dehydrogenase encoded by GDH1, which accounts for a major fraction of the NADPH consumption during growth on ammonium, was deleted, a...

  6. Fermentation of mixed glucose-xylose substrates by engineered strains of Saccharomyces cerevisiae: role of the coenzyme specificity of xylose reductase, and effect of glucose on xylose utilization

    Directory of Open Access Journals (Sweden)

    Klimacek Mario

    2010-03-01

    Full Text Available Abstract Background In spite of the substantial metabolic engineering effort previously devoted to the development of Saccharomyces cerevisiae strains capable of fermenting both the hexose and pentose sugars present in lignocellulose hydrolysates, the productivity of reported strains for conversion of the naturally most abundant pentose, xylose, is still a major issue of process efficiency. Protein engineering for targeted alteration of the nicotinamide cofactor specificity of enzymes catalyzing the first steps in the metabolic pathway for xylose was a successful approach of reducing xylitol by-product formation and improving ethanol yield from xylose. The previously reported yeast strain BP10001, which expresses heterologous xylose reductase from Candida tenuis in mutated (NADH-preferring form, stands for a series of other yeast strains designed with similar rational. Using 20 g/L xylose as sole source of carbon, BP10001 displayed a low specific uptake rate qxylose (g xylose/g dry cell weight/h of 0.08. The study presented herein was performed with the aim of analysing (external factors that limit qxylose of BP10001 under xylose-only and mixed glucose-xylose substrate conditions. We also carried out a comprehensive investigation on the currently unclear role of coenzyme utilization, NADPH compared to NADH, for xylose reduction during co-fermentation of glucose and xylose. Results BP10001 and BP000, expressing C. tenuis xylose reductase in NADPH-preferring wild-type form, were used. Glucose and xylose (each at 10 g/L were converted sequentially, the corresponding qsubstrate values being similar for each strain (glucose: 3.0; xylose: 0.05. The distribution of fermentation products from glucose was identical for both strains whereas when using xylose, BP10001 showed enhanced ethanol yield (BP10001 0.30 g/g; BP000 0.23 g/g and decreased yields of xylitol (BP10001 0.26 g/g; BP000 0.36 g/g and glycerol (BP10001 0.023 g/g; BP000 0.072 g/g as compared

  7. Heterologous expression of cellulase genes in natural Saccharomyces cerevisiae strains.

    Science.gov (United States)

    Davison, Steffi A; den Haan, Riaan; van Zyl, Willem Heber

    2016-09-01

    Enzyme cost is a major impediment to second-generation (2G) cellulosic ethanol production. One strategy to reduce enzyme cost is to engineer enzyme production capacity in a fermentative microorganism to enable consolidated bio-processing (CBP). Ideally, a strain with a high secretory phenotype, high fermentative capacity as well as an innate robustness to bioethanol-specific stressors, including tolerance to products formed during pre-treatment and fermentation of lignocellulosic substrates should be used. Saccharomyces cerevisiae is a robust fermentative yeast but has limitations as a potential CBP host, such as low heterologous protein secretion titers. In this study, we evaluated natural S. cerevisiae isolate strains for superior secretion activity and other industrially relevant characteristics needed during the process of lignocellulosic ethanol production. Individual cellulases namely Saccharomycopsis fibuligera Cel3A (β-glucosidase), Talaromyces emersonii Cel7A (cellobiohydrolase), and Trichoderma reesei Cel5A (endoglucanase) were utilized as reporter proteins. Natural strain YI13 was identified to have a high secretory phenotype, demonstrating a 3.7- and 3.5-fold higher Cel7A and Cel5A activity, respectively, compared to the reference strain S288c. YI13 also demonstrated other industrially relevant characteristics such as growth vigor, high ethanol titer, multi-tolerance to high temperatures (37 and 40 °C), ethanol (10 % w/v), and towards various concentrations of a cocktail of inhibitory compounds commonly found in lignocellulose hydrolysates. This study accentuates the value of natural S. cerevisiae isolate strains to serve as potential robust and highly productive chassis organisms for CBP strain development. PMID:27470141

  8. Direct ethanol production from hemicellulosic materials of rice straw by use of an engineered yeast strain codisplaying three types of hemicellulolytic enzymes on the surface of xylose-utilizing Saccharomyces cerevisiae cells.

    Science.gov (United States)

    Sakamoto, Takatoshi; Hasunuma, Tomohisa; Hori, Yoshimi; Yamada, Ryosuke; Kondo, Akihiko

    2012-04-30

    The cost of the lignocellulose-hydrolyzing enzymes used in the saccharification process of ethanol production from biomass accounts for a relatively high proportion of total processing costs. Cell surface engineering technology has facilitated a reduction in these costs by integrating saccharification and fermentation processes into a recombinant microbe strain expressing heterologous enzymes on the cell surface. We constructed a recombinant Saccharomyces cerevisiae that not only hydrolyzed hemicelluloses by codisplaying endoxylanase from Trichoderma reesei, β-xylosidase from Aspergillus oryzae, and β-glucosidase from Aspergillus aculeatus but that also assimilated xylose through the expression of xylose reductase and xylitol dehydrogenase from Pichia stipitis and xylulokinase from S. cerevisiae. The recombinant strain successfully produced ethanol from rice straw hydrolysate consisting of hemicellulosic material containing xylan, xylooligosaccharides, and cellooligosaccharides without requiring the addition of sugar-hydrolyzing enzymes or detoxication. The ethanol titer of the strain was 8.2g/l after 72h fermentation, which was approximately 2.5-fold higher than that of the control strain. The yield (grams of ethanol per gram of total sugars in rice straw hydrolysate consumed) was 0.41g/g, which corresponded to 82% of the theoretical yield. The cell surface-engineered strain was thus highly effective for consolidating the process of ethanol production from hemicellulosic materials.

  9. Lactose fermentation by engineered Saccharomyces cerevisiae capable of fermenting cellobiose.

    Science.gov (United States)

    Liu, Jing-Jing; Zhang, Guo-Chang; Oh, Eun Joong; Pathanibul, Panchalee; Turner, Timothy L; Jin, Yong-Su

    2016-09-20

    Lactose is an inevitable byproduct of the dairy industry. In addition to cheese manufacturing, the growing Greek yogurt industry generates excess acid whey, which contains lactose. Therefore, rapid and efficient conversion of lactose to fuels and chemicals would be useful for recycling the otherwise harmful acid whey. Saccharomyces cerevisiae, a popular metabolic engineering host, cannot natively utilize lactose. However, we discovered that an engineered S. cerevisiae strain (EJ2) capable of fermenting cellobiose can also ferment lactose. This finding suggests that a cellobiose transporter (CDT-1) can transport lactose and a β-glucosidase (GH1-1) can hydrolyze lactose by acting as a β-galactosidase. While the lactose fermentation by the EJ2 strain was much slower than the cellobiose fermentation, a faster lactose-fermenting strain (EJ2e8) was obtained through serial subcultures on lactose. The EJ2e8 strain fermented lactose with a consumption rate of 2.16g/Lh. The improved lactose fermentation by the EJ2e8 strain was due to the increased copy number of cdt-1 and gh1-1 genes. Looking ahead, the EJ2e8 strain could be exploited for the production of other non-ethanol fuels and chemicals from lactose through further metabolic engineering. PMID:27457698

  10. Overproduction of fatty acids in engineered Saccharomyces cerevisiae.

    Science.gov (United States)

    Li, Xiaowei; Guo, Daoyi; Cheng, Yongbo; Zhu, Fayin; Deng, Zixin; Liu, Tiangang

    2014-09-01

    The long hydrocarbon fatty acyl chain is energy rich, making it an ideal precursor for liquid transportation fuels and high-value oleo chemicals. As Saccharomyces cerevisiae has many advantages for industrial production compared to Escherichia coli. Here, we attempted to engineer Saccharomyces cerevisiae for overproduction of fatty acids. First, disruption of the beta-oxidation pathway, elimination of the acyl-CoA synthetases, overexpression of different thioesterases and acetyl-CoA carboxylase ACC1, and engineering the supply of precursor acetyl-CoA. The engineered strain XL122 produced more than 120 mg/L of fatty acids. In parallel, we inactivated ADH1, the dominant gene for ethanol production, to redirect the metabolic flux to fatty acids synthesis. The engineered strain DG005 produced about 140 mg/L fatty acids. Additionally, Acetyl-CoA carboxylase was identified as a critical bottleneck of fatty acids synthesis in S. cerevisiae with a cell-free system. However, overexpression of ACC1 has little effect on fatty acids biosynthesis. As it has been reported that phosphorylation of ACC1 may influent its activity, so phosphorylation sites of ACC1 were further identified. Although the regulatory mechanisms remain unclear, our results provide rationale for future studies to target this critical step. All these efforts, particularly the discovery of the limiting step are critical for developing a "cell factory" for the overproduction of fatty acids by using type I fatty acids synthase in yeast or other fungi. PMID:24752690

  11. Redox balancing in recombinant strains of Saccharomyces cerevisiae

    Energy Technology Data Exchange (ETDEWEB)

    Anderlund, M.

    1998-09-01

    In metabolically engineered Saccharomyces cerevisiae expressing Pichia stipitis XYL1 and XYL2 genes, encoding xylose reductase (XR) and xylitol dehydrogenase (XDH), respectively, xylitol is excreted as the major product during anaerobic xylose fermentation and only low yields of ethanol are produced. This has been interpreted as a result of the dual cofactor dependence of XR and the exclusive use of NAD{sup +} by XDH. The excretion of xylitol was completely stopped and the formation of glycerol and acetic acid were reduced in xylose utilising S. cerevisiae strains cultivated in oxygen-limited conditions by expressing lower levels of XR than of XDH. The expression level of XYL1 and XYL2 were controlled by changing the promoters and transcription directions of the genes. A new functional metabolic pathway was established when Thermus thermophilus xylA gene was expressed in S. cerevisiae. The recombinant strain was able to ferment xylose to ethanol when cultivated on a minimal medium containing xylose as only carbon source. In order to create a channeled metabolic transfer in the two first steps of the xylose metabolism, XYL1 and XYL2 were fused in-frame and expressed in S. cerevisiae. When the fusion protein, containing a linker of three amino acids, was co expressed together with native XR and XDH monomers, enzyme complexes consisting of chimeric and native subunits were formed. The total activity of these complexes exhibited 10 and 9 times higher XR and XDH activity, respectively, than the original conjugates, consisting of only chimeric subunits. This strain produced less xylitol and the xylitol yield was lower than with strains only expressing native XR and XDH monomers. In addition, more ethanol and less acetic acid were formed. A new gene encoding the cytoplasmic transhydrogenase from Azotobacter vinelandii was cloned. The enzyme showed high similarity to the family of pyridine nucleotide-disulphide oxidoreductase. To analyse the physiological effect of

  12. Isolation, identification and characterization of regional indigenous Saccharomyces cerevisiae strains

    Directory of Open Access Journals (Sweden)

    Hana Šuranská

    2016-03-01

    Full Text Available Abstract In the present work we isolated and identified various indigenous Saccharomyces cerevisiae strains and screened them for the selected oenological properties. These S. cerevisiae strains were isolated from berries and spontaneously fermented musts. The grape berries (Sauvignon blanc and Pinot noir were grown under the integrated and organic mode of farming in the South Moravia (Czech Republic wine region. Modern genotyping techniques such as PCR-fingerprinting and interdelta PCR typing were employed to differentiate among indigenous S. cerevisiae strains. This combination of the methods provides a rapid and relatively simple approach for identification of yeast of S. cerevisiae at strain level. In total, 120 isolates were identified and grouped by molecular approaches and 45 of the representative strains were tested for selected important oenological properties including ethanol, sulfur dioxide and osmotic stress tolerance, intensity of flocculation and desirable enzymatic activities. Their ability to produce and utilize acetic/malic acid was examined as well; in addition, H2S production as an undesirable property was screened. The oenological characteristics of indigenous isolates were compared to a commercially available S. cerevisiae BS6 strain, which is commonly used as the starter culture. Finally, some indigenous strains coming from organically treated grape berries were chosen for their promising oenological properties and these strains will be used as the starter culture, because application of a selected indigenous S. cerevisiae strain can enhance the regional character of the wines.

  13. Impact of systems biology on metabolic engineering of Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Nielsen, Jens; Jewett, Michael Christopher

    2008-01-01

    Saccharomyces cerevisiae is extremely well suited for this objective. As one of the most intensely studied eukaryotic model organisms, a rich density of knowledge detailing its genetics, biochemistry, physiology, and large-scale fermentation performance can be capitalized upon to enable a substantial increase...... in the industrial application of this yeast. Developments in genomics and high-throughput systems biology tools are enhancing one's ability to rapidly characterize cellular behaviour, which is valuable in the field of metabolic engineering where strain characterization is often the bottleneck in strain development...... programmes. Here, the impact of systems biology on metabolic engineering is reviewed and perspectives on the role of systems biology in the design of cell factories are given....

  14. Strain-engineered MOSFETs

    CERN Document Server

    Maiti, CK

    2012-01-01

    Currently strain engineering is the main technique used to enhance the performance of advanced silicon-based metal-oxide-semiconductor field-effect transistors (MOSFETs). Written from an engineering application standpoint, Strain-Engineered MOSFETs introduces promising strain techniques to fabricate strain-engineered MOSFETs and to methods to assess the applications of these techniques. The book provides the background and physical insight needed to understand new and future developments in the modeling and design of n- and p-MOSFETs at nanoscale. This book focuses on recent developments in st

  15. Natural and modified promoters for tailored metabolic engineering of the yeast Saccharomyces cerevisiae

    NARCIS (Netherlands)

    Hubmann, Georg; Thevelein, Johan M; Nevoigt, Elke

    2014-01-01

    The ease of highly sophisticated genetic manipulations in the yeast Saccharomyces cerevisiae has initiated numerous initiatives towards development of metabolically engineered strains for novel applications beyond its traditional use in brewing, baking, and wine making. In fact, baker's yeast has be

  16. Malic acid production by Saccharomyces cerevisiae: engineering of pyruvate carbosylation, oxaloacetate reduction and malate export

    NARCIS (Netherlands)

    Zelle, R.M.; Hulster, de E.; Winden, van W.A.; Waard, de P.; Dijkema, C.; Winkler, A.A.; Geertman, J.M.A.

    2008-01-01

    Malic acid is a potential biomass-derivable "building block" for chemical synthesis. Since wild-type Saccharomyces cerevisiae strains produce only low levels of malate, metabolic engineering is required to achieve efficient malate production with this yeast. A promising pathway for malate production

  17. Malic Acid Production by Saccharomyces cerevisiae: Engineering of Pyruvate Carboxylation, Oxaloacetate Reduction, and Malate Export

    NARCIS (Netherlands)

    Zelle, R.M.; De Hulster, E.; Van Winden, W.A.; De Waard, P.; Dijkema, C.; Winkler, A.A.; Geertman, J.M.; Van Dijken, J.P.; Pronk, J.T.; Van Maris, A.J.A.

    2008-01-01

    Malic acid is a potential biomass-derivable "building block" for chemical synthesis. Since wild-type Saccharomyces cerevisiae strains produce only low levels of malate, metabolic engineering is required to achieve efficient malate production with this yeast. A promising pathway for malate production

  18. Advances in metabolic engineering of yeast Saccharomyces cerevisiae for production of chemicals

    DEFF Research Database (Denmark)

    Borodina, Irina; Nielsen, Jens

    2014-01-01

    Yeast Saccharomyces cerevisiae is an important industrial host for production of enzymes, pharmaceutical and nutraceutical ingredients and recently also commodity chemicals and biofuels. Here, we review the advances in modeling and synthetic biology tools and how these tools can speed up the deve......Yeast Saccharomyces cerevisiae is an important industrial host for production of enzymes, pharmaceutical and nutraceutical ingredients and recently also commodity chemicals and biofuels. Here, we review the advances in modeling and synthetic biology tools and how these tools can speed up...... the development of yeast cell factories. We also present an overview of metabolic engineering strategies for developing yeast strains for production of polymer monomers: lactic, succinic, and cis,cis-muconic acids. S. cerevisiae has already firmly established itself as a cell factory in industrial biotechnology...... and the advances in yeast strain engineering will stimulate development of novel yeast-based processes for chemicals production....

  19. Multiplex metabolic pathway engineering using CRISPR/Cas9 in Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Jakociunas, Tadas; Bonde, Ida; Herrgard, Markus;

    2015-01-01

    CRISPR/Cas9 is a simple and efficient tool for targeted and marker-free genome engineering. Here, we report the development and successful application of a multiplex CRISPR/Cas9 system for genome engineering of up to 5 different genomic loci in one transformation step in baker's yeast Saccharomyces...... cerevisiae. To assess the specificity of the tool we employed genome re-sequencing to screen for off-target sites in all single knock-out strains targeted by different gRNAs. This extensive analysis identified no more genome variants in CRISPR/Cas9 engineered strains compared to wild-type reference strains...

  20. Evaluation of cytochrome P-450 concentration in Saccharomyces cerevisiae strains

    Directory of Open Access Journals (Sweden)

    Míriam Cristina Sakuragui Matuo

    2010-09-01

    Full Text Available Saccharomyces cerevisiae has been widely used in mutagenicity tests due to the presence of a cytochrome P-450 system, capable of metabolizing promutagens to active mutagens. There are a large number of S. cerevisiae strains with varying abilities to produce cytochrome P-450. However, strain selection and ideal cultivation conditions are not well defined. We compared cytochrome P-450 levels in four different S. cerevisiae strains and evaluated the cultivation conditions necessary to obtain the highest levels. The amount of cytochrome P-450 produced by each strain varied, as did the incubation time needed to reach the maximum level. The highest cytochrome P-450 concentrations were found in media containing fermentable sugars. The NCYC 240 strain produced the highest level of cytochrome P-450 when grown in the presence of 20 % (w/v glucose. The addition of ethanol to the media also increased cytochrome P-450 synthesis in this strain. These results indicate cultivation conditions must be specific and well-established for the strain selected in order to assure high cytochrome P-450 levels and reliable mutagenicity results.Linhagens de Saccharomyces cerevisiae tem sido amplamente empregadas em testes de mutagenicidade devido à presença de um sistema citocromo P-450 capaz de metabolizar substâncias pró-mutagênicas à sua forma ativa. Devido à grande variedade de linhagens de S. cerevisiae com diferentes capacidades de produção de citocromo P-450, torna-se necessária a seleção de cepas, bem como a definição das condições ideais de cultivo. Neste trabalho, foram comparados os níveis de citocromo P-450 em quatro diferentes linhagens de S. cerevisiae e avaliadas as condições de cultivo necessárias para obtenção de altas concentrações deste sistema enzimático. O maior nível enzimático foi encontrado na linhagem NCYC 240 em presença de 20 % de glicose (p/v. A adição de etanol ao meio de cultura também produziu um aumento na s

  1. Mead production: selection and characterization assays of Saccharomyces cerevisiae strains.

    Science.gov (United States)

    Pereira, Ana Paula; Dias, Teresa; Andrade, João; Ramalhosa, Elsa; Estevinho, Letícia M

    2009-08-01

    Mead is a traditional drink, which results from the alcoholic fermentation of diluted honey carried out by yeasts. However, when it is produced in a homemade way, mead producers find several problems, namely, the lack of uniformity in the final product, delayed and arrested fermentations, and the production of "off-flavours" by the yeasts. These problems are usually associated with the inability of yeast strains to respond and adapt to unfavourable and stressful growth conditions. The main objectives of this work were to evaluate the capacity of Saccharomyces cerevisiae strains, isolated from honey of the Trás-os-Montes (Northeast Portugal), to produce mead. Five strains from honey, as well as one laboratory strain and one commercial wine strain, were evaluated in terms of their fermentation performance under ethanol, sulphur dioxide and osmotic stress. All the strains showed similar behaviour in these conditions. Two yeasts strains isolated from honey and the commercial wine strain were further tested for mead production, using two different honey (a dark and a light honey), enriched with two supplements (one commercial and one developed by the research team), as fermentation media. The results obtained in this work show that S. cerevisiae strains isolated from honey, are appropriate for mead production. However it is of extreme importance to take into account the characteristics of the honey, and supplements used in the fermentation medium formulation, in order to achieve the best results in mead production. PMID:19481129

  2. CRISPR-Cas9 Genome Engineering in Saccharomyces cerevisiae Cells.

    Science.gov (United States)

    Ryan, Owen W; Poddar, Snigdha; Cate, Jamie H D

    2016-01-01

    This protocol describes a method for CRISPR-Cas9-mediated genome editing that results in scarless and marker-free integrations of DNA into Saccharomyces cerevisiae genomes. DNA integration results from cotransforming (1) a single plasmid (pCAS) that coexpresses the Cas9 endonuclease and a uniquely engineered single guide RNA (sgRNA) expression cassette and (2) a linear DNA molecule that is used to repair the chromosomal DNA damage by homology-directed repair. For target specificity, the pCAS plasmid requires only a single cloning modification: replacing the 20-bp guide RNA sequence within the sgRNA cassette. This CRISPR-Cas9 protocol includes methods for (1) cloning the unique target sequence into pCAS, (2) assembly of the double-stranded DNA repair oligonucleotides, and (3) cotransformation of pCAS and linear repair DNA into yeast cells. The protocol is technically facile and requires no special equipment. It can be used in any S. cerevisiae strain, including industrial polyploid isolates. Therefore, this CRISPR-Cas9-based DNA integration protocol is achievable by virtually any yeast genetics and molecular biology laboratory. PMID:27250940

  3. Divergence in wine characteristics produced by wild and domesticated strains of Saccharomyces cerevisiae

    OpenAIRE

    Katie E Hyma; Saerens, Sofie M; Verstrepen, Kevin J.; Justin C Fay

    2011-01-01

    The budding yeast Saccharomyces cerevisiae is the primary species used by wine makers to convert sugar into alcohol during wine fermentation. Saccharomyces cerevisiae is found in vineyards, but is also found in association with oak trees and other natural sources. Although wild strains of S. cerevisiae as well as other Saccharomyces species are also capable of wine fermentation, a genetically distinct group of S. cerevisiae strains is primarily used to produce wine, consistent with the idea t...

  4. EasyClone 2.0: expanded toolkit of integrative vectors for stable gene expression in industrial Saccharomyces cerevisiae strains.

    Science.gov (United States)

    Stovicek, Vratislav; Borja, Gheorghe M; Forster, Jochen; Borodina, Irina

    2015-11-01

    Saccharomyces cerevisiae is one of the key cell factories for production of chemicals and active pharmaceuticals. For large-scale fermentations, particularly in biorefinery applications, it is desirable to use stress-tolerant industrial strains. However, such strains are less amenable for metabolic engineering than the standard laboratory strains. To enable easy delivery and overexpression of genes in a wide range of industrial S. cerevisiae strains, we constructed a set of integrative vectors with long homology arms and dominant selection markers. The vectors integrate into previously validated chromosomal locations via double cross-over and result in homogenous stable expression of the integrated genes, as shown for several unrelated industrial strains. Cre-mediated marker rescue is possible for removing markers positioned on different chromosomes. To demonstrate the applicability of the presented vector set for metabolic engineering of industrial yeast, we constructed xylose-utilizing strains overexpressing xylose isomerase, xylose transporter and five genes of the pentose phosphate pathway.

  5. In vitro screening of probiotic properties of Saccharomyces cerevisiae var. boulardii and food-borne Saccharomyces cerevisiae strains

    DEFF Research Database (Denmark)

    van der Aa Kuhle, Alis; Skovgaard, Kerstin; Jespersen, Lene

    2005-01-01

    .6-16.8%) recorded for two isolates from blue veined cheeses. Merely 25% of the S. cerevisiae var. boulardii strains displayed good adhesive properties (16.2-28.0%). The expression of the proinflammatory cytokine IL-1α decreased strikingly in IPEC-J2 cells exposed to a Shiga-like toxin 2e producing Escherichia coli...... strain when the cells were pre- and coincubated with S. cerevisiae var. boulardii even though this yeast strain was low adhesive (5.4%), suggesting that adhesion is not a mandatory prerequisite for such a probiotic effect. A strain of S. cerevisiae isolated from West African sorghum beer exerted similar...... effects hence indicating that food-borne strains of S. cerevisiae may possess probiotic properties in spite of low adhesiveness. © 2004 Elsevier B.V. All rights reserved....

  6. Draft Genome Sequence of Saccharomyces cerevisiae IR-2, a Useful Industrial Strain for Highly Efficient Production of Bioethanol

    OpenAIRE

    Sahara, Takehiko; Fujimori, Kazuhiro E.; Nezuo, Maiko; Tsukahara, Masatoshi; Tochigi, Yuki; Ohgiya, Satoru; Kamagata, Yoichi

    2014-01-01

    We sequenced the genome of Saccharomyces cerevisiae IR-2, which is a diploid industrial strain with flocculation activity and the ability to efficiently produce bioethanol. The approximately 11.4-Mb draft genome information provides useful insights into metabolic engineering for the production of bioethanol from biomass.

  7. Dual utilization of NADPH and NADH cofactors enhances xylitol production in engineered Saccharomyces cerevisiae.

    Science.gov (United States)

    Jo, Jung-Hyun; Oh, Sun-Young; Lee, Hyeun-Soo; Park, Yong-Cheol; Seo, Jin-Ho

    2015-12-01

    Xylitol, a natural sweetener, can be produced by hydrogenation of xylose in hemicelluloses. In microbial processes, utilization of only NADPH cofactor limited commercialization of xylitol biosynthesis. To overcome this drawback, Saccharomyces cerevisiae D452-2 was engineered to express two types of xylose reductase (XR) with either NADPH-dependence or NADH-preference. Engineered S. cerevisiae DWM expressing both the XRs exhibited higher xylitol productivity than the yeast strain expressing NADPH-dependent XR only (DWW) in both batch and glucose-limited fed-batch cultures. Furthermore, the coexpression of S. cerevisiae ZWF1 and ACS1 genes in the DWM strain increased intracellular concentrations of NADPH and NADH and improved maximum xylitol productivity by 17%, relative to that for the DWM strain. Finally, the optimized fed-batch fermentation of S. cerevisiae DWM-ZWF1-ACS1 resulted in 196.2 g/L xylitol concentration, 4.27 g/L h productivity and almost the theoretical yield. Expression of the two types of XR utilizing both NADPH and NADH is a promising strategy to meet the industrial demands for microbial xylitol production. PMID:26470683

  8. High vanillin tolerance of an evolved Saccharomyces cerevisiae strain owing to its enhanced vanillin reduction and antioxidative capacity.

    Science.gov (United States)

    Shen, Yu; Li, Hongxing; Wang, Xinning; Zhang, Xiaoran; Hou, Jin; Wang, Linfeng; Gao, Nan; Bao, Xiaoming

    2014-11-01

    The phenolic compounds present in hydrolysates pose significant challenges for the sustainable lignocellulosic materials refining industry. Three Saccharomyces cerevisiae strains with high tolerance to lignocellulose hydrolysate were obtained through ethyl methanesulfonate mutation and adaptive evolution. Among them, strain EMV-8 exhibits specific tolerance to vanillin, a phenolic compound common in lignocellulose hydrolysate. The EMV-8 maintains a specific growth rate of 0.104 h(-1) in 2 g L(-1) vanillin, whereas the reference strain cannot grow. Physiological studies revealed that the vanillin reduction rate of EMV-8 is 1.92-fold higher than its parent strain, and the Trolox equivalent antioxidant capacity of EMV-8 is 15 % higher than its parent strain. Transcriptional analysis results confirmed an up-regulated oxidoreductase activity and antioxidant activity in this strain. Our results suggest that enhancing the antioxidant capacity and oxidoreductase activity could be a strategy to engineer S. cerevisiae for improved vanillin tolerance.

  9. Comparative proteomics analysis of engineered Saccharomyces cerevisiae with enhanced biofuel precursor production.

    Directory of Open Access Journals (Sweden)

    Xiaoling Tang

    Full Text Available The yeast Saccharomyces cerevisiae was metabolically modified for enhanced biofuel precursor production by knocking out genes encoding mitochondrial isocitrate dehydrogenase and over-expression of a heterologous ATP-citrate lyase. A comparative iTRAQ-coupled 2D LC-MS/MS analysis was performed to obtain a global overview of ubiquitous protein expression changes in S. cerevisiae engineered strains. More than 300 proteins were identified. Among these proteins, 37 were found differentially expressed in engineered strains and they were classified into specific categories based on their enzyme functions. Most of the proteins involved in glycolytic and pyruvate branch-point pathways were found to be up-regulated and the proteins involved in respiration and glyoxylate pathway were however found to be down-regulated in engineered strains. Moreover, the metabolic modification of S. cerevisiae cells resulted in a number of up-regulated proteins involved in stress response and differentially expressed proteins involved in amino acid metabolism and protein biosynthesis pathways. These LC-MS/MS based proteomics analysis results not only offered extensive information in identifying potential protein-protein interactions, signal pathways and ubiquitous cellular changes elicited by the engineered pathways, but also provided a meaningful biological information platform serving further modification of yeast cells for enhanced biofuel production.

  10. Development Of An Efficient Glycerol Utilizing Saccharomyces Cerevisiae Strain Via Adaptive Laboratory Evolution

    DEFF Research Database (Denmark)

    Strucko, Tomas; Zirngibl, Katharina; Tharwat Tolba Mohamed, Elsayed;

    2015-01-01

    that popular wild-type laboratory yeast strains, commonly applied in metabolic engineering studies, did not grow or grew very slowly in glycerol medium.In this work, an adaptive laboratory evolution approach to obtain S. cerevisiae strains with an improved ability to grow on glycerol was applied. A broad array...... catabolism in yeast. The knowledge acquired in this study may be further applied for rational S. cerevisiae strain improvement for using glycerol as a carbon source in industrial biotechnology processes. This work is a part of the DeYeastLibrary consortium financed by ERA-IB DeYeastLibrary - Designer yeast...... strain library optimized for metabolic engineering applications http://www.era-ib.net/deyeast-library...

  11. Direct mating between diploid sake strains of Saccharomyces cerevisiae.

    Science.gov (United States)

    Hashimoto, Shinji; Aritomi, Kazuo; Minohara, Takafumi; Nishizawa, Yoshinori; Hoshida, Hisashi; Kashiwagi, Susumu; Akada, Rinji

    2006-02-01

    Various auxotrophic mutants of diploid heterothallic Japanese sake strains of Saccharomyces cerevisiae were utilized for selecting mating-competent diploid isolates. The auxotrophic mutants were exposed to ultraviolet (UV) irradiation and crossed with laboratory haploid tester strains carrying complementary auxotrophic markers. Zygotes were then selected on minimal medium. Sake strains exhibiting a MATa or MATalpha mating type were easily obtained at high frequency without prior sporulation, suggesting that the UV irradiation induced homozygosity at the MAT locus. Flow cytometric analysis of a hybrid showed a twofold higher DNA content than the sake diploid parent, consistent with tetraploidy. By crossing strains of opposite mating type in all possible combinations, a number of hybrids were constructed. Hybrids formed in crosses between traditional sake strains and between a natural nonhaploid isolate and traditional sake strains displayed equivalent fermentation ability without any apparent defects and produced comparable or improved sake. Isolation of mating-competent auxotrophic mutants directly from industrial yeast strains allows crossbreeding to construct polyploids suitable for industrial use without dependence on sporulation.

  12. Nanofiltration concentration of extracellular glutathione produced by engineered Saccharomyces cerevisiae.

    Science.gov (United States)

    Sasaki, Kengo; Hara, Kiyotaka Y; Kawaguchi, Hideo; Sazuka, Takashi; Ogino, Chiaki; Kondo, Akihiko

    2016-01-01

    This study aimed to optimize extracellular glutathione production by a Saccharomyces cerevisiae engineered strain and to concentrate the extracellular glutathione by membrane separation processes, including ultrafiltration (UF) and nanofiltration (NF). Synthetic defined (SD) medium containing 20 g L(-1) glucose was fermented for 48 h; the fermentation liquid was passed through an UF membrane to remove macromolecules. Glutathione in this permeate was concentrated for 48 h to 545.1 ± 33.6 mg L(-1) using the NF membrane; this was a significantly higher concentration than that obtained with yeast extract peptone dextrose (YPD) medium following 96 h NF concentration (217.9 ± 57.4 mg L(-1)). This higher glutathione concentration results from lower cellular growth in SD medium (final OD600 = 6.9 ± 0.1) than in YPD medium (final OD600 = 11.0 ± 0.6) and thus higher production of extracellular glutathione (16.0 ± 1.3 compared to 9.2 ± 2.1 mg L(-1) in YPD medium, respectively). Similar fermentation and membrane processing of sweet sorghum juice containing 20 g L(-1) total sugars provided 240.3 ± 60.6 mg L(-1) glutathione. Increased extracellular production of glutathione by this engineered strain in SD medium and subsequent UF permeation and NF concentration in shortend time may help realize industrial recovery of extracellular glutathione.

  13. Nanofiltration concentration of extracellular glutathione produced by engineered Saccharomyces cerevisiae.

    Science.gov (United States)

    Sasaki, Kengo; Hara, Kiyotaka Y; Kawaguchi, Hideo; Sazuka, Takashi; Ogino, Chiaki; Kondo, Akihiko

    2016-01-01

    This study aimed to optimize extracellular glutathione production by a Saccharomyces cerevisiae engineered strain and to concentrate the extracellular glutathione by membrane separation processes, including ultrafiltration (UF) and nanofiltration (NF). Synthetic defined (SD) medium containing 20 g L(-1) glucose was fermented for 48 h; the fermentation liquid was passed through an UF membrane to remove macromolecules. Glutathione in this permeate was concentrated for 48 h to 545.1 ± 33.6 mg L(-1) using the NF membrane; this was a significantly higher concentration than that obtained with yeast extract peptone dextrose (YPD) medium following 96 h NF concentration (217.9 ± 57.4 mg L(-1)). This higher glutathione concentration results from lower cellular growth in SD medium (final OD600 = 6.9 ± 0.1) than in YPD medium (final OD600 = 11.0 ± 0.6) and thus higher production of extracellular glutathione (16.0 ± 1.3 compared to 9.2 ± 2.1 mg L(-1) in YPD medium, respectively). Similar fermentation and membrane processing of sweet sorghum juice containing 20 g L(-1) total sugars provided 240.3 ± 60.6 mg L(-1) glutathione. Increased extracellular production of glutathione by this engineered strain in SD medium and subsequent UF permeation and NF concentration in shortend time may help realize industrial recovery of extracellular glutathione. PMID:26105794

  14. Recycling carbon dioxide during xylose fermentation by engineered Saccharomyces cerevisiae

    Science.gov (United States)

    In this study, we introduced the ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) and phosphoribulokinase (PRK) into an engineered S. cerevisiae (SR8) harboring the XR/XDH pathway and up-regulated PPP 10, to enable CO2 recycling through a synthetic rPPP during xylose fermentation (Fig. 1). ...

  15. Co-utilization of L-arabinose and D-xylose by laboratory and industrial Saccharomyces cerevisiae strains

    Directory of Open Access Journals (Sweden)

    Boles Eckhard

    2006-04-01

    Full Text Available Abstract Background Fermentation of lignocellulosic biomass is an attractive alternative for the production of bioethanol. Traditionally, the yeast Saccharomyces cerevisiae is used in industrial ethanol fermentations. However, S. cerevisiae is naturally not able to ferment the pentose sugars D-xylose and L-arabinose, which are present in high amounts in lignocellulosic raw materials. Results We describe the engineering of laboratory and industrial S. cerevisiae strains to co-ferment the pentose sugars D-xylose and L-arabinose. Introduction of a fungal xylose and a bacterial arabinose pathway resulted in strains able to grow on both pentose sugars. Introduction of a xylose pathway into an arabinose-fermenting laboratory strain resulted in nearly complete conversion of arabinose into arabitol due to the L-arabinose reductase activity of the xylose reductase. The industrial strain displayed lower arabitol yield and increased ethanol yield from xylose and arabinose. Conclusion Our work demonstrates simultaneous co-utilization of xylose and arabinose in recombinant strains of S. cerevisiae. In addition, the co-utilization of arabinose together with xylose significantly reduced formation of the by-product xylitol, which contributed to improved ethanol production.

  16. Metabolic engineering of ammonium assimilation in xylose-fermenting Saccharomyes cerevisiae improves ethanol production

    DEFF Research Database (Denmark)

    Roca, Christophe Francois Aime; Nielsen, Jens; Olsson, Lisbeth

    2003-01-01

    Cofactor imbalance impedes xylose assimilation in Saccharomyces cerevisiae that has been metabolically engineered for xylose utilization. To improve cofactor use, we modified ammonia assimilation in recombinant S. cerevisiae by deleting GDH1, which encodes an NADPH-dependent glutamate dehydrogenase...

  17. Multiplex metabolic pathway engineering using CRISPR/Cas9 in Saccharomyces cerevisiae.

    Science.gov (United States)

    Jakočiūnas, Tadas; Bonde, Ida; Herrgård, Markus; Harrison, Scott J; Kristensen, Mette; Pedersen, Lasse E; Jensen, Michael K; Keasling, Jay D

    2015-03-01

    CRISPR/Cas9 is a simple and efficient tool for targeted and marker-free genome engineering. Here, we report the development and successful application of a multiplex CRISPR/Cas9 system for genome engineering of up to 5 different genomic loci in one transformation step in baker's yeast Saccharomyces cerevisiae. To assess the specificity of the tool we employed genome re-sequencing to screen for off-target sites in all single knock-out strains targeted by different gRNAs. This extensive analysis identified no more genome variants in CRISPR/Cas9 engineered strains compared to wild-type reference strains. We applied our genome engineering tool for an exploratory analysis of all possible single, double, triple, quadruple and quintuple gene disruption combinations to search for strains with high mevalonate production, a key intermediate for the industrially important isoprenoid biosynthesis pathway. Even though we did not overexpress any genes in the mevalonate pathway, this analysis identified strains with mevalonate titers greater than 41-fold compared to the wild-type strain. Our findings illustrate the applicability of this highly specific and efficient multiplex genome engineering approach to accelerate functional genomics and metabolic engineering efforts.

  18. Improvement of galactose uptake in Saccharomyces cerevisiae through overexpression of phosphoglucomutase: Example of transcript analysis as a tool in inverse metabolic engineering

    DEFF Research Database (Denmark)

    Bro, Christoffer; Knudsen, S.; Regenberg, Birgitte;

    2005-01-01

    Through genome-wide transcript analysis of a reference strain and two recombinant Saccharomyces cerevisiae strains with different rates of galactose uptake, we obtained information about the global transcriptional response to metabolic engineering of the GAL gene regulatory network. One of the re......Through genome-wide transcript analysis of a reference strain and two recombinant Saccharomyces cerevisiae strains with different rates of galactose uptake, we obtained information about the global transcriptional response to metabolic engineering of the GAL gene regulatory network. One...

  19. Metabolic engineering of Saccharomyces cerevisiae for production of carboxylic acids: current status and challenges.

    Science.gov (United States)

    Abbott, Derek A; Zelle, Rintze M; Pronk, Jack T; van Maris, Antonius J A

    2009-12-01

    To meet the demands of future generations for chemicals and energy and to reduce the environmental footprint of the chemical industry, alternatives for petrochemistry are required. Microbial conversion of renewable feedstocks has a huge potential for cleaner, sustainable industrial production of fuels and chemicals. Microbial production of organic acids is a promising approach for production of chemical building blocks that can replace their petrochemically derived equivalents. Although Saccharomyces cerevisiae does not naturally produce organic acids in large quantities, its robustness, pH tolerance, simple nutrient requirements and long history as an industrial workhorse make it an excellent candidate biocatalyst for such processes. Genetic engineering, along with evolution and selection, has been successfully used to divert carbon from ethanol, the natural endproduct of S. cerevisiae, to pyruvate. Further engineering, which included expression of heterologous enzymes and transporters, yielded strains capable of producing lactate and malate from pyruvate. Besides these metabolic engineering strategies, this review discusses the impact of transport and energetics as well as the tolerance towards these organic acids. In addition to recent progress in engineering S. cerevisiae for organic acid production, the key limitations and challenges are discussed in the context of sustainable industrial production of organic acids from renewable feedstocks. PMID:19566685

  20. Genome engineering in Saccharomyces cerevisiae using CRISPR-Cas systems

    OpenAIRE

    DiCarlo, James; Norville, Julie; Mali, Prashant; Rios Villanueva, Xavier; Aach, John Dennis; Church, George McDonald

    2013-01-01

    Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and CRISPR-associated (Cas) systems in bacteria and archaea use RNA-guided nuclease activity to provide adaptive immunity against invading foreign nucleic acids. Here, we report the use of type II bacterial CRISPR-Cas system in Saccharomyces cerevisiae for genome engineering. The CRISPR-Cas components, Cas9 gene and a designer genome targeting CRISPR guide RNA (gRNA), show robust and specific RNA-guided endonuclease activity a...

  1. Isobutanol production in engineered Saccharomyces cerevisiae by overexpression of 2-ketoisovalerate decarboxylase and valine biosynthetic enzymes.

    Science.gov (United States)

    Lee, Won-Heong; Seo, Seung-Oh; Bae, Yi-Hyun; Nan, Hong; Jin, Yong-Su; Seo, Jin-Ho

    2012-11-01

    Engineering of Saccharomyces cerevisiae to produce advanced biofuels such as isobutanol has received much attention because this yeast has a natural capacity to produce higher alcohols. In this study, construction of isobutanol production systems was attempted by overexpression of effective 2-keto acid decarboxylase (KDC) and combinatorial overexpression of valine biosynthetic enzymes in S. cerevisiae D452-2. Among the six putative KDC enzymes from various microorganisms, 2-ketoisovalerate decarboxylase (Kivd) from L. lactis subsp. lactis KACC 13877 was identified as the most suitable KDC for isobutanol production in the yeast. Isobutanol production by the engineered S. cerevisiae was assessed in micro-aerobic batch fermentations using glucose as a sole carbon source. 93 mg/L isobutanol was produced in the Kivd overexpressing strain, which corresponds to a fourfold improvement as compared with the control strain. Isobutanol production was further enhanced to 151 mg/L by additional overexpression of acetolactate synthase (Ilv2p), acetohydroxyacid reductoisomerase (Ilv5p), and dihydroxyacid dehydratase (Ilv3p) in the cytosol.

  2. [Invertase Overproduction May Provide for Inulin Fermentation by Selection Strains of Saccharomyces cerevisiae].

    Science.gov (United States)

    Naumov, G I; Naumova, E S

    2015-01-01

    In some recent publications, the ability of selection strains of Saccharomyces cerevisiae to ferment inulin was attributed to inulinase activity. The review summarizes the literature data indicating that overproduction of invertase, an enzyme common to S. cerevisiae, may be responsible for this phenomenon. PMID:26263621

  3. Stress Tolerance Variations in Saccharomyces cerevisiae Strains from Diverse Ecological Sources and Geographical Locations.

    Directory of Open Access Journals (Sweden)

    Yan-Lin Zheng

    Full Text Available The budding yeast Saccharomyces cerevisiae is a platform organism for bioethanol production from various feedstocks and robust strains are desirable for efficient fermentation because yeast cells inevitably encounter stressors during the process. Recently, diverse S. cerevisiae lineages were identified, which provided novel resources for understanding stress tolerance variations and related shaping factors in the yeast. This study characterized the tolerance of diverse S. cerevisiae strains to the stressors of high ethanol concentrations, temperature shocks, and osmotic stress. The results showed that the isolates from human-associated environments overall presented a higher level of stress tolerance compared with those from forests spared anthropogenic influences. Statistical analyses indicated that the variations of stress tolerance were significantly correlated with both ecological sources and geographical locations of the strains. This study provides guidelines for selection of robust S. cerevisiae strains for bioethanol production from nature.

  4. CRISPR–Cas system enables fast and simple genome editing of industrial Saccharomyces cerevisiae strains

    Directory of Open Access Journals (Sweden)

    Vratislav Stovicek

    2015-12-01

    Full Text Available There is a demand to develop 3rd generation biorefineries that integrate energy production with the production of higher value chemicals from renewable feedstocks. Here, robust and stress-tolerant industrial strains of Saccharomyces cerevisiae will be suitable production organisms. However, their genetic manipulation is challenging, as they are usually diploid or polyploid. Therefore, there is a need to develop more efficient genetic engineering tools. We applied a CRISPR–Cas9 system for genome editing of different industrial strains, and show simultaneous disruption of two alleles of a gene in several unrelated strains with the efficiency ranging between 65% and 78%. We also achieved simultaneous disruption and knock-in of a reporter gene, and demonstrate the applicability of the method by designing lactic acid-producing strains in a single transformation event, where insertion of a heterologous gene and disruption of two endogenous genes occurred simultaneously. Our study provides a foundation for efficient engineering of industrial yeast cell factories.

  5. Metabolic engineering of Saccharomyces cerevisiae for the production of n-butanol

    Directory of Open Access Journals (Sweden)

    Myers Samuel

    2008-12-01

    Full Text Available Abstract Background Increasing energy costs and environmental concerns have motivated engineering microbes for the production of "second generation" biofuels that have better properties than ethanol. Results and conclusion Saccharomyces cerevisiae was engineered with an n-butanol biosynthetic pathway, in which isozymes from a number of different organisms (S. cerevisiae, Escherichia coli, Clostridium beijerinckii, and Ralstonia eutropha were substituted for the Clostridial enzymes and their effect on n-butanol production was compared. By choosing the appropriate isozymes, we were able to improve production of n-butanol ten-fold to 2.5 mg/L. The most productive strains harbored the C. beijerinckii 3-hydroxybutyryl-CoA dehydrogenase, which uses NADH as a co-factor, rather than the R. eutropha isozyme, which uses NADPH, and the acetoacetyl-CoA transferase from S. cerevisiae or E. coli rather than that from R. eutropha. Surprisingly, expression of the genes encoding the butyryl-CoA dehydrogenase from C. beijerinckii (bcd and etfAB did not improve butanol production significantly as previously reported in E. coli. Using metabolite analysis, we were able to determine which steps in the n-butanol biosynthetic pathway were the most problematic and ripe for future improvement.

  6. Metabolic engineering of Saccharomyces cerevisiae for the production of n-butanol

    Energy Technology Data Exchange (ETDEWEB)

    Steen, EricJ.; Chan, Rossana; Prasad, Nilu; Myers, Samuel; Petzold, Christopher; Redding, Alyssa; Ouellet, Mario; Keasling, JayD.

    2008-11-25

    BackgroundIncreasing energy costs and environmental concerns have motivated engineering microbes for the production of ?second generation? biofuels that have better properties than ethanol.Results& ConclusionsSaccharomyces cerevisiae was engineered with an n-butanol biosynthetic pathway, in which isozymes from a number of different organisms (S. cerevisiae, Escherichia coli, Clostridium beijerinckii, and Ralstonia eutropha) were substituted for the Clostridial enzymes and their effect on n-butanol production was compared. By choosing the appropriate isozymes, we were able to improve production of n-butanol ten-fold to 2.5 mg/L. The most productive strains harbored the C. beijerinckii 3-hydroxybutyryl-CoA dehydrogenase, which uses NADH as a co-factor, rather than the R. eutropha isozyme, which uses NADPH, and the acetoacetyl-CoA transferase from S. cerevisiae or E. coli rather than that from R. eutropha. Surprisingly, expression of the genes encoding the butyryl-CoA dehydrogenase from C. beijerinckii (bcd and etfAB) did not improve butanol production significantly as previously reported in E. coli. Using metabolite analysis, we were able to determine which steps in the n-butanol biosynthetic pathway were the most problematic and ripe for future improvement.

  7. Efficient Bioethanol Production by a Recombinant Flocculent Saccharomyces cerevisiae Strain with a Genome-Integrated NADP+-Dependent Xylitol Dehydrogenase Gene▿

    Science.gov (United States)

    Matsushika, Akinori; Inoue, Hiroyuki; Watanabe, Seiya; Kodaki, Tsutomu; Makino, Keisuke; Sawayama, Shigeki

    2009-01-01

    The recombinant industrial Saccharomyces cerevisiae strain MA-R5 was engineered to express NADP+-dependent xylitol dehydrogenase using the flocculent yeast strain IR-2, which has high xylulose-fermenting ability, and both xylose consumption and ethanol production remarkably increased. Furthermore, the MA-R5 strain produced the highest ethanol yield (0.48 g/g) from nonsulfuric acid hydrolysate of wood chips. PMID:19329659

  8. Genome-wide transcriptional response of a Saccharomyces cerevisiae strain with an altered redox metabolism

    DEFF Research Database (Denmark)

    Bro, Christoffer; Regenberg, Birgitte; Nielsen, Jens

    2004-01-01

    The genome-wide transcriptional response of a Saccharomyces cerevisiae strain deleted in GDH1 that encodes a NADP(+)-dependent glutamate dehydrogenase was compared to a wild-type strain under anaerobic steady-state conditions. The GDH1-deleted strain has a significantly reduced NADPH requirement,...

  9. Lactic acid production from cellobiose and xylose by engineered Saccharomyces cerevisiae.

    Science.gov (United States)

    Turner, Timothy L; Zhang, Guo-Chang; Oh, Eun Joong; Subramaniam, Vijay; Adiputra, Andrew; Subramaniam, Vimal; Skory, Christopher D; Jang, Ji Yeon; Yu, Byung Jo; Park, In; Jin, Yong-Su

    2016-05-01

    Efficient and rapid production of value-added chemicals from lignocellulosic biomass is an important step toward a sustainable society. Lactic acid, used for synthesizing the bioplastic polylactide, has been produced by microbial fermentation using primarily glucose. Lignocellulosic hydrolysates contain high concentrations of cellobiose and xylose. Here, we constructed a recombinant Saccharomyces cerevisiae strain capable of fermenting cellobiose and xylose into lactic acid. Specifically, genes (cdt-1, gh1-1, XYL1, XYL2, XYL3, and ldhA) coding for cellobiose transporter, β-glucosidase, xylose reductase, xylitol dehydrogenase, xylulokinase, and lactate dehydrogenase were integrated into the S. cerevisiae chromosomes. The resulting strain produced lactic acid from cellobiose or xylose with high yields. When fermenting a cellulosic sugar mixture containing 10 g/L glucose, 40 g/L xylose, and 80 g/L cellobiose, the engineered strain produced 83 g/L of lactic acid with a yield of 0.66 g lactic acid/g sugar (66% theoretical maximum). This study demonstrates initial steps toward the feasibility of sustainable production of lactic acid from lignocellulosic sugars by engineered yeast. PMID:26524688

  10. Improvement of oxidative stress tolerance in Saccharomyces cerevisiae through global transcription machinery engineering.

    Science.gov (United States)

    Zhao, Hongwei; Li, Jingyuan; Han, Beizhong; Li, Xuan; Chen, Jingyu

    2014-05-01

    Excessive oxidative stress poses significant damage to yeast cells during fermentation process, and finally affects fermentation efficiency and the quality of products. In this paper, global transcription machinery engineering was employed to elicit Saccharomyces cerevisiae phenotypes of higher tolerance against oxidative stress caused by H2O2. Two strains from two plasmid-based mutagenesis libraries (Spt15 and Taf25), which exhibited significant increases in oxidative stress tolerance, were successfully isolated. At moderate H2O2 shock (≤3.5 mM), a positive correlation was found between the outperformance in cell growth of the oxidation-tolerate strains and H2O2 concentration. Several mutations were observed in the native transcription factors, which resulted in a different transcriptional profile compared with the control. Catalase and superoxide dismutase activities of the two mutants increased under H2O2 stress conditions. Fermentation experiments revealed that the mutant strain taf25-3 has a shorter lag phase compared to the control one, indicating that taf25-3 had improved adaptation ability to H2O2-induced oxidative stress and higher fermentation efficiency. Our study demonstrated that several amino acid substitutions in general transcription factors (Spt15 and Taf25) could modify the cellular oxidation defense systems and improve the anti-oxidation ability of S. cerevisiae. It could make the industrial ethanol fermentation more efficient and cost-effective by using the strain of higher stress tolerance. PMID:24633583

  11. Improved Acetic Acid Resistance in Saccharomyces cerevisiae by Overexpression of the WHI2 Gene Identified through Inverse Metabolic Engineering.

    Science.gov (United States)

    Chen, Yingying; Stabryla, Lisa; Wei, Na

    2016-01-29

    Development of acetic acid-resistant Saccharomyces cerevisiae is important for economically viable production of biofuels from lignocellulosic biomass, but the goal remains a critical challenge due to limited information on effective genetic perturbation targets for improving acetic acid resistance in the yeast. This study employed a genomic-library-based inverse metabolic engineering approach to successfully identify a novel gene target, WHI2 (encoding a cytoplasmatic globular scaffold protein), which elicited improved acetic acid resistance in S. cerevisiae. Overexpression of WHI2 significantly improved glucose and/or xylose fermentation under acetic acid stress in engineered yeast. The WHI2-overexpressing strain had 5-times-higher specific ethanol productivity than the control in glucose fermentation with acetic acid. Analysis of the expression of WHI2 gene products (including protein and transcript) determined that acetic acid induced endogenous expression of Whi2 in S. cerevisiae. Meanwhile, the whi2Δ mutant strain had substantially higher susceptibility to acetic acid than the wild type, suggesting the important role of Whi2 in the acetic acid response in S. cerevisiae. Additionally, overexpression of WHI2 and of a cognate phosphatase gene, PSR1, had a synergistic effect in improving acetic acid resistance, suggesting that Whi2 might function in combination with Psr1 to elicit the acetic acid resistance mechanism. These results improve our understanding of the yeast response to acetic acid stress and provide a new strategy to breed acetic acid-resistant yeast strains for renewable biofuel production.

  12. Genome-scale consequences of cofactor balancing in engineered pentose utilization pathways in Saccharomyces cerevisiae.

    Directory of Open Access Journals (Sweden)

    Amit Ghosh

    Full Text Available Biofuels derived from lignocellulosic biomass offer promising alternative renewable energy sources for transportation fuels. Significant effort has been made to engineer Saccharomyces cerevisiae to efficiently ferment pentose sugars such as D-xylose and L-arabinose into biofuels such as ethanol through heterologous expression of the fungal D-xylose and L-arabinose pathways. However, one of the major bottlenecks in these fungal pathways is that the cofactors are not balanced, which contributes to inefficient utilization of pentose sugars. We utilized a genome-scale model of S. cerevisiae to predict the maximal achievable growth rate for cofactor balanced and imbalanced D-xylose and L-arabinose utilization pathways. Dynamic flux balance analysis (DFBA was used to simulate batch fermentation of glucose, D-xylose, and L-arabinose. The dynamic models and experimental results are in good agreement for the wild type and for the engineered D-xylose utilization pathway. Cofactor balancing the engineered D-xylose and L-arabinose utilization pathways simulated an increase in ethanol batch production of 24.7% while simultaneously reducing the predicted substrate utilization time by 70%. Furthermore, the effects of cofactor balancing the engineered pentose utilization pathways were evaluated throughout the genome-scale metabolic network. This work not only provides new insights to the global network effects of cofactor balancing but also provides useful guidelines for engineering a recombinant yeast strain with cofactor balanced engineered pathways that efficiently co-utilizes pentose and hexose sugars for biofuels production. Experimental switching of cofactor usage in enzymes has been demonstrated, but is a time-consuming effort. Therefore, systems biology models that can predict the likely outcome of such strain engineering efforts are highly useful for motivating which efforts are likely to be worth the significant time investment.

  13. Diversity of Saccharomyces cerevisiae Strains Isolated from Two Italian Wine-Producing Regions.

    Science.gov (United States)

    Capece, Angela; Granchi, Lisa; Guerrini, Simona; Mangani, Silvia; Romaniello, Rossana; Vincenzini, Massimo; Romano, Patrizia

    2016-01-01

    Numerous studies, based on different molecular techniques analyzing DNA polymorphism, have provided evidence that indigenous Saccharomyces cerevisiae populations display biogeographic patterns. Since the differentiated populations of S. cerevisiae seem to be responsible for the regional identity of wine, the aim of this work was to assess a possible relationship between the diversity and the geographical origin of indigenous S. cerevisiae isolates from two different Italian wine-producing regions (Tuscany and Basilicata). For this purpose, sixty-three isolates from Aglianico del Vulture grape must (main cultivar in the Basilicata region) and from Sangiovese grape must (main cultivar in the Tuscany region) were characterized genotypically, by mitochondrial DNA restriction analysis and MSP-PCR by using (GTG)5 primers, and phenotypically, by determining technological properties and metabolic compounds of oenological interest after alcoholic fermentation. All the S. cerevisiae isolates from each region were inoculated both in must obtained from Aglianico grape and in must obtained from Sangiovese grape to carry out fermentations at laboratory-scale. Numerical analysis of DNA patterns resulting from both molecular methods and principal component analysis of phenotypic data demonstrated a high diversity among the S. cerevisiae strains. Moreover, a correlation between genotypic and phenotypic groups and geographical origin of the strains was found, supporting the concept that there can be a microbial aspect to terroir. Therefore, exploring the diversity of indigenous S. cerevisiae strains can allow developing tailored strategies to select wine yeast strains better adapted to each viticultural area. PMID:27446054

  14. Diversity of Saccharomyces cerevisiae Strains Isolated from Two Italian Wine-Producing Regions

    Science.gov (United States)

    Capece, Angela; Granchi, Lisa; Guerrini, Simona; Mangani, Silvia; Romaniello, Rossana; Vincenzini, Massimo; Romano, Patrizia

    2016-01-01

    Numerous studies, based on different molecular techniques analyzing DNA polymorphism, have provided evidence that indigenous Saccharomyces cerevisiae populations display biogeographic patterns. Since the differentiated populations of S. cerevisiae seem to be responsible for the regional identity of wine, the aim of this work was to assess a possible relationship between the diversity and the geographical origin of indigenous S. cerevisiae isolates from two different Italian wine-producing regions (Tuscany and Basilicata). For this purpose, sixty-three isolates from Aglianico del Vulture grape must (main cultivar in the Basilicata region) and from Sangiovese grape must (main cultivar in the Tuscany region) were characterized genotypically, by mitochondrial DNA restriction analysis and MSP-PCR by using (GTG)5 primers, and phenotypically, by determining technological properties and metabolic compounds of oenological interest after alcoholic fermentation. All the S. cerevisiae isolates from each region were inoculated both in must obtained from Aglianico grape and in must obtained from Sangiovese grape to carry out fermentations at laboratory-scale. Numerical analysis of DNA patterns resulting from both molecular methods and principal component analysis of phenotypic data demonstrated a high diversity among the S. cerevisiae strains. Moreover, a correlation between genotypic and phenotypic groups and geographical origin of the strains was found, supporting the concept that there can be a microbial aspect to terroir. Therefore, exploring the diversity of indigenous S. cerevisiae strains can allow developing tailored strategies to select wine yeast strains better adapted to each viticultural area. PMID:27446054

  15. Genome Sequence and Analysis of a Stress-Tolerant, Wild-Derived Strain of Saccharomyces cerevisiae Used in Biofuels Research.

    Science.gov (United States)

    McIlwain, Sean J; Peris, David; Sardi, Maria; Moskvin, Oleg V; Zhan, Fujie; Myers, Kevin S; Riley, Nicholas M; Buzzell, Alyssa; Parreiras, Lucas S; Ong, Irene M; Landick, Robert; Coon, Joshua J; Gasch, Audrey P; Sato, Trey K; Hittinger, Chris Todd

    2016-01-01

    The genome sequences of more than 100 strains of the yeast Saccharomyces cerevisiae have been published. Unfortunately, most of these genome assemblies contain dozens to hundreds of gaps at repetitive sequences, including transposable elements, tRNAs, and subtelomeric regions, which is where novel genes generally reside. Relatively few strains have been chosen for genome sequencing based on their biofuel production potential, leaving an additional knowledge gap. Here, we describe the nearly complete genome sequence of GLBRCY22-3 (Y22-3), a strain of S. cerevisiae derived from the stress-tolerant wild strain NRRL YB-210 and subsequently engineered for xylose metabolism. After benchmarking several genome assembly approaches, we developed a pipeline to integrate Pacific Biosciences (PacBio) and Illumina sequencing data and achieved one of the highest quality genome assemblies for any S. cerevisiae strain. Specifically, the contig N50 is 693 kbp, and the sequences of most chromosomes, the mitochondrial genome, and the 2-micron plasmid are complete. Our annotation predicts 92 genes that are not present in the reference genome of the laboratory strain S288c, over 70% of which were expressed. We predicted functions for 43 of these genes, 28 of which were previously uncharacterized and unnamed. Remarkably, many of these genes are predicted to be involved in stress tolerance and carbon metabolism and are shared with a Brazilian bioethanol production strain, even though the strains differ dramatically at most genetic loci. The Y22-3 genome sequence provides an exceptionally high-quality resource for basic and applied research in bioenergy and genetics. PMID:27172212

  16. Lactic acid production from xylose by engineered Saccharomyces cerevisiae without PDC or ADH deletion.

    Science.gov (United States)

    Turner, Timothy L; Zhang, Guo-Chang; Kim, Soo Rin; Subramaniam, Vijay; Steffen, David; Skory, Christopher D; Jang, Ji Yeon; Yu, Byung Jo; Jin, Yong-Su

    2015-10-01

    Production of lactic acid from renewable sugars has received growing attention as lactic acid can be used for making renewable and bio-based plastics. However, most prior studies have focused on production of lactic acid from glucose despite that cellulosic hydrolysates contain xylose as well as glucose. Microbial strains capable of fermenting both glucose and xylose into lactic acid are needed for sustainable and economic lactic acid production. In this study, we introduced a lactic acid-producing pathway into an engineered Saccharomyces cerevisiae capable of fermenting xylose. Specifically, ldhA from the fungi Rhizopus oryzae was overexpressed under the control of the PGK1 promoter through integration of the expression cassette in the chromosome. The resulting strain exhibited a high lactate dehydrogenase activity and produced lactic acid from glucose or xylose. Interestingly, we observed that the engineered strain exhibited substrate-dependent product formation. When the engineered yeast was cultured on glucose, the major fermentation product was ethanol while lactic acid was a minor product. In contrast, the engineered yeast produced lactic acid almost exclusively when cultured on xylose under oxygen-limited conditions. The yields of ethanol and lactic acid from glucose were 0.31 g ethanol/g glucose and 0.22 g lactic acid/g glucose, respectively. On xylose, the yields of ethanol and lactic acid were <0.01 g ethanol/g xylose and 0.69 g lactic acid/g xylose, respectively. These results demonstrate that lactic acid can be produced from xylose with a high yield by S. cerevisiae without deleting pyruvate decarboxylase, and the formation patterns of fermentations can be altered by substrates.

  17. Benchmarking two commonly used Saccharomyces cerevisiae strains for heterologous vanillin-β-glucoside production

    OpenAIRE

    Tomas Strucko; Olivera Magdenoska; Mortensen, Uffe H.

    2015-01-01

    The yeast Saccharomyces cerevisiae is a widely used eukaryotic model organism and a key cell factory for production of biofuels and wide range of chemicals. From the broad palette of available yeast strains, the most popular are those derived from laboratory strain S288c and the industrially relevant CEN.PK strain series. Importantly, in recent years these two strains have been subjected to comparative “-omics” analyzes pointing out significant genotypic and phenotypic differences. It is ther...

  18. Expression of protein engineered NADP{sup +}-dependent xylitol dehydrogenase increases ethanol production from xylose in recombinant Saccharomyces cerevisiae

    Energy Technology Data Exchange (ETDEWEB)

    Matsushika, Akinori; Inoue, Hiroyuki; Murakami, Katsuji; Takimura, Osamu; Sawayama, Shigeki [National Institute of Advanced Industrial Science and Technology, Hiroshima (Japan). Biomass Technology Research Center; Watanabe, Seiya; Kodaki, Tsutomu; Makino, Keisuke [Kyoto Univ. (Japan). Inst. of Advanced Energy

    2008-11-15

    A recombinant Saccharomyces cerevisiae strain transformed with xylose reductase (XR) and xylitol dehydrogenase (XDH) genes from Pichia stipitis has the ability to convert xylose to ethanol together with the unfavorable excretion of xylitol, which may be due to cofactor imbalance between NADPH-preferring XR and NAD{sup +}-dependent XDH. To reduce xylitol formation, we have already generated several XDH mutants with a reversal of coenzyme specificity toward NADP{sup +}. In this study, we constructed a set of recombinant S. cerevisiae strains with xylose-fermenting ability, including protein-engineered NADP{sup +}-dependent XDH-expressing strains. The most positive effect on xylose-to-ethanol fermentation was found by using a strain named MA-N5, constructed by chromosomal integration of the gene for NADP{sup +}-dependent XDH along with XR and endogenous xylulokinase genes. The MA-N5 strain had an increase in ethanol production and decrease in xylitol excretion compared with the reference strain expressing wild-type XDH when fermenting not only xylose but also mixed sugars containing glucose and xylose. Furthermore, the MA-N5 strain produced ethanol with a high yield of 0.49 g of ethanol/g of total consumed sugars in the nonsulfuric acid hydrolysate of wood chips. The results demonstrate that glucose and xylose present in the lignocellulosic hydrolysate can be efficiently fermented by this redox-engineered strain. (orig.)

  19. Engineering the fatty acid metabolic pathway in Saccharomyces cerevisiae for advanced biofuel production

    Directory of Open Access Journals (Sweden)

    Xiaoling Tang

    2015-12-01

    Full Text Available Fatty acid-derived fuels and chemicals have attracted a great deal of attention in recent decades, due to their following properties of high compatibility to gasoline-based fuels and existing infrastructure for their direct utilization, storage and distribution. The yeast Saccharomyces cerevisiae is the ideal biofuel producing candidate, based on the wealth of available genetic information and versatile tools designed to manipulate its metabolic pathways. Engineering the fatty acid metabolic pathways in S. cerevisiae is an effective strategy to increase its fatty acid biosynthesis and provide more pathway precursors for production of targeted products. This review summarizes the recent progress in metabolic engineering of yeast cells for fatty acids and fatty acid derivatives production, including the regulation of acetyl-CoA biosynthesis, NADPH production, fatty acid elongation, and the accumulation of activated precursors of fatty acids for converting enzymes. By introducing specific enzymes in the engineered strains, a powerful platform with a scalable, controllable and economic route for advanced biofuel production has been established.

  20. BIOSORPTION OF CHROMIUM (VI FROM INDUSTRIAL EFFLUENT BY WILD ANDMUTANT TYPE STRAIN OF SACCHAROMYCES CEREVISIAE AND ITS IMMOBILIZED FORM

    Directory of Open Access Journals (Sweden)

    K Selvam, K Arungandhi, B Vishnupriya, T Shanmuga priya and M Yamuna

    2013-01-01

    Full Text Available Biosorption of chromium was studied by wild type Saccharomyces cerevisiae strain, mutant strain, immobilized-wild type and mutant strain. Chromium absorption pattern was observed in all experimental conditions. Hexavalent chromium (VI was analyzed by diphenyl carbazide method, by oxidizing the trivalent chromium (III. The percentage efficiency of wild type S. cerevisiae and its mutant strain, immobilized-wild type and mutant strain were 94.8%, 98.7%, 97.4% and 100% respectively. S. cerevisiae mutant strain and their immobilized form was found to be effective in biosorption of chromium (VI than the wild type forms.

  1. BIOSORPTION OF CHROMIUM (VI) FROM INDUSTRIAL EFFLUENT BY WILD ANDMUTANT TYPE STRAIN OF SACCHAROMYCES CEREVISIAE AND ITS IMMOBILIZED FORM

    OpenAIRE

    K Selvam, K Arungandhi, B Vishnupriya, T Shanmuga priya and M Yamuna

    2013-01-01

    Biosorption of chromium was studied by wild type Saccharomyces cerevisiae strain, mutant strain, immobilized-wild type and mutant strain. Chromium absorption pattern was observed in all experimental conditions. Hexavalent chromium (VI) was analyzed by diphenyl carbazide method, by oxidizing the trivalent chromium (III). The percentage efficiency of wild type S. cerevisiae and its mutant strain, immobilized-wild type and mutant strain were 94.8%, 98.7%, 97.4% and 100% respectively. S. cerevisi...

  2. Improvement of oxidized glutathione fermentation by thiol redox metabolism engineering in Saccharomyces cerevisiae.

    Science.gov (United States)

    Hara, Kiyotaka Y; Aoki, Naoko; Kobayashi, Jyumpei; Kiriyama, Kentaro; Nishida, Keiji; Araki, Michihiro; Kondo, Akihiko

    2015-11-01

    Glutathione is a valuable tripeptide widely used in the pharmaceutical, food, and cosmetic industries. In industrial fermentation, glutathione is currently produced primarily using the yeast Saccharomyces cerevisiae. Intracellular glutathione exists in two forms; the majority is present as reduced glutathione (GSH) and a small amount is present as oxidized glutathione (GSSG). However, GSSG is more stable than GSH and is a more attractive form for the storage of glutathione extracted from yeast cells after fermentation. In this study, intracellular GSSG content was improved by engineering thiol oxidization metabolism in yeast. An engineered strain producing high amounts of glutathione from over-expression of glutathione synthases and lacking glutathione reductase was used as a platform strain. Additional over-expression of thiol oxidase (1.8.3.2) genes ERV1 or ERO1 increased the GSSG content by 2.9-fold and 2.0-fold, respectively, compared with the platform strain, without decreasing cell growth. However, over-expression of thiol oxidase gene ERV2 showed almost no effect on the GSSG content. Interestingly, ERO1 over-expression did not decrease the GSH content, raising the total glutathione content of the cell, but ERV1 over-expression decreased the GSH content, balancing the increase in the GSSG content. Furthermore, the increase in the GSSG content due to ERO1 over-expression was enhanced by additional over-expression of the gene encoding Pdi1, whose reduced form activates Ero1 in the endoplasmic reticulum. These results indicate that engineering the thiol redox metabolism of S. cerevisiae improves GSSG and is critical to increasing the total productivity and stability of glutathione.

  3. Metabolic engineering of Saccharomyces cerevisiae for production of butanol isomers.

    Science.gov (United States)

    Generoso, Wesley Cardoso; Schadeweg, Virginia; Oreb, Mislav; Boles, Eckhard

    2015-06-01

    Saccharomyces cerevisiae has decisive advantages in industrial processes due to its tolerance to alcohols and fermentation conditions. Butanol isomers are considered as suitable fuel substitutes and valuable biomass-derived chemical building blocks. Whereas high production was achieved with bacterial systems, metabolic engineering of yeast for butanol production is in the beginning. For isobutanol synthesis, combination of valine biosynthesis and degradation, and complete pathway re-localisation into cytosol or mitochondria gave promising results. However, competing pathways, co-factor imbalances and FeS cluster assembly are still major issues. 1-Butanol production via the Clostridium pathway seems to be limited by cytosolic acetyl-CoA, its central precursor. Endogenous 1-butanol pathways have been discovered via threonine or glycine catabolism. 2-Butanol production was established but was limited by B12-dependence.

  4. Metabolic engineering of a synergistic pathway for n-butanol production in Saccharomyces cerevisiae

    Science.gov (United States)

    Shi, Shuobo; Si, Tong; Liu, Zihe; Zhang, Hongfang; Ang, Ee Lui; Zhao, Huimin

    2016-01-01

    n-Butanol has several favourable properties as an advanced fuel or a platform chemical. Bio-based production of n-butanol is becoming increasingly important for sustainable chemical industry. Synthesis of n-butanol can be achieved via more than one metabolic pathway. Here we report the metabolic engineering of Saccharomyces cerevisiae to produce n-butanol through a synergistic pathway: the endogenous threonine pathway and the introduced citramalate pathway. Firstly, we characterized and optimized the endogenous threonine pathway; then, a citramalate synthase (CimA) mediated pathway was introduced to construct the synergistic pathway; next, the synergistic pathway was optimized by additional overexpression of relevant genes identified previously; meanwhile, the n-butanol production was also improved by overexpression of keto-acid decarboxylases (KDC) and alcohol dehydrogenase (ADH). After combining these strategies with co-expression of LEU1 (two copies), LEU4, LEU2 (two copies), LEU5, CimA, NFS1, ADH7 and ARO10*, we achieved an n-butanol production of 835 mg/L in the final engineered strain, which is almost 7-fold increase compared to the initial strain. Furthermore, the production showed a 3-fold of the highest titer ever reported in yeast. Therefore, the engineered yeast strain represents a promising alternative platform for n-butanol production. PMID:27161023

  5. Investigation of the dominance behavior of Saccharomyces cerevisiae strains during wine fermentation.

    Science.gov (United States)

    Perrone, Benedetta; Giacosa, Simone; Rolle, Luca; Cocolin, Luca; Rantsiou, Kalliopi

    2013-07-15

    During wine fermentation, different strains of Saccharomyces cerevisiae compete in the same fermenting must and dominance takes place when one strain overcomes all the others. The purpose of this study was to investigate this phenomenon by identifying S. cerevisiae strains endowed with this feature and to test them in laboratory fermentations. First, autochthonous S. cerevisiae from Nebbiolo fermentations were isolated, molecularly identified and characterized. Genetically diverse S. cerevisiae strains were subsequently subjected to physiological characterization and to micro-scale fermentation, the weight loss kinetics was measured and HPLC analysis was performed at the end of the fermentation. Then, the strains that presented good fermentation characteristics were chosen for further analysis and to determine the dominance feature. For this purpose, couples of strains were co-inoculated in Nebbiolo must and the fermentations were monitored by microbiological and chemical analysis. Two different inoculation approaches were used: co-fermentations in flasks with mixed cells and reactor co-fermentations, in which the cells from the two different strains were kept separate by means of a 0.45 μm filter membrane, which allowed the fermenting must to move freely between the two compartments. During the flask co-fermentations, a minisatellite PCR protocol was applied, in order to differentiate the two strains and determine which one was able to dominate. The protocol included a culture-dependent approach and an independent one. In the first case, DNA extraction was performed on all the colonies scraped off the plates after sampling. In the second case, DNA extraction was performed directly on the fermenting must. The strains that were able to dominate were tested against several S. cerevisiae in order to confirm this dominance behavior. Dominance was observed in the early stages of fermentation, as early as 3days. Combinations of dominant and not-dominant strains were

  6. Rational and evolutionary engineering approaches uncover a small set of genetic changes efficient for rapid xylose fermentation in Saccharomyces cerevisiae.

    Directory of Open Access Journals (Sweden)

    Soo Rin Kim

    Full Text Available Economic bioconversion of plant cell wall hydrolysates into fuels and chemicals has been hampered mainly due to the inability of microorganisms to efficiently co-ferment pentose and hexose sugars, especially glucose and xylose, which are the most abundant sugars in cellulosic hydrolysates. Saccharomyces cerevisiae cannot metabolize xylose due to a lack of xylose-metabolizing enzymes. We developed a rapid and efficient xylose-fermenting S. cerevisiae through rational and inverse metabolic engineering strategies, comprising the optimization of a heterologous xylose-assimilating pathway and evolutionary engineering. Strong and balanced expression levels of the XYL1, XYL2, and XYL3 genes constituting the xylose-assimilating pathway increased ethanol yields and the xylose consumption rates from a mixture of glucose and xylose with little xylitol accumulation. The engineered strain, however, still exhibited a long lag time when metabolizing xylose above 10 g/l as a sole carbon source, defined here as xylose toxicity. Through serial-subcultures on xylose, we isolated evolved strains which exhibited a shorter lag time and improved xylose-fermenting capabilities than the parental strain. Genome sequencing of the evolved strains revealed that mutations in PHO13 causing loss of the Pho13p function are associated with the improved phenotypes of the evolved strains. Crude extracts of a PHO13-overexpressing strain showed a higher phosphatase activity on xylulose-5-phosphate (X-5-P, suggesting that the dephosphorylation of X-5-P by Pho13p might generate a futile cycle with xylulokinase overexpression. While xylose consumption rates by the evolved strains improved substantially as compared to the parental strain, xylose metabolism was interrupted by accumulated acetate. Deletion of ALD6 coding for acetaldehyde dehydrogenase not only prevented acetate accumulation, but also enabled complete and efficient fermentation of xylose as well as a mixture of glucose and

  7. Genetic analysis of Saccharomyces cerevisiae strains isolated from Palm Wine in Eastern Nigeria. Comparison with other African strains.

    OpenAIRE

    Ezeronye, O.U.; Legras, Jean Luc

    2009-01-01

    Aims: To study the yeast diversity of Nigerian palm wines by comparison with other African strains. Methods and Results: Twenty-three Saccharomyces cerevisiae strains were obtained from palm wine samples collected at four locations in eastern Nigeria, and characterized using different molecular techniques: internal transcribed spacer restriction fragment length polymorphism and sequence analysis, pulsed field gel electrophoresis, inter delta typing and microsatellite multilocus analysis...

  8. Glucose and maltose metabolism in MIG1-disrupted and MAL-constitutive strains of Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Klein, Christopher; Olsson, Lisbeth; Rønnow, B;

    1997-01-01

    The alleviation of glucose control of maltose metabolism brought about by MIG1 disruption was compared to that by MAL overexpression in a haploid Saccharomyces cerevisiae strain. The sugar consumption profiles during cultivation of the wild type, single transformants and a double transformant in ...

  9. Physiological studies in aerobic batch cultivations of Saccharomyces cerevisiae strains harboring the MEL1 gene

    DEFF Research Database (Denmark)

    Østergaard, Simon; Roca, Christophe Francois Aime; Ronnow, B.;

    2000-01-01

    Physiological studies of Saccharomyces cerevisiae strains harboring the MEL1 gene were carried out in aerobic batch cultivations on glucose-galactose mixtures and on the disaccharide melibiose, which is hydrolyzed by the enzyme melibiase (Mel1, EC 3.2.1.22) into a glucose and a galactose moiety. ...

  10. The Interaction between Saccharomyces cerevisiae and Non-Saccharomyces Yeast during Alcoholic Fermentation is Species and Strain Specific

    Directory of Open Access Journals (Sweden)

    Chunxiao eWang

    2016-04-01

    Full Text Available The present study analyzes the lack of culturability of different non-Saccharomyces strains due to interaction with Saccharomyces cerevisiae during alcoholic fermentation. Interaction was followed in mixed fermentations with 1:1 inoculation of S. cerevisiae and ten non-Saccharomyces strains. Starmerella bacillaris and Torulaspora delbrueckii indicated longer coexistence in mixed fermentations compared with Hanseniaspora uvarum and Metschnikowia pulcherrima. Strain differences in culturability and nutrient consumption (glucose, alanine, ammonium, arginine or glutamine were found within each species in mixed fermentation with S. cerevisiae. The interaction was further analyzed using cell-free supernatant from S. cerevisiae and synthetic media mimicking both single fermentations with S. cerevisiae and using mixed fermentations with the corresponding non-Saccharomyces species. Cell-free S. cerevisiae supernatants induced faster culturability loss than synthetic media corresponding to the same fermentation stage. This demonstrated that some metabolites produced by S. cerevisiae played the main role in the decreased culturability of the other non-Saccharomyces yeasts. However, changes in the concentrations of main metabolites had also an effect. Culturability differences were observed among species and strains in culture assays and thus showed distinct tolerance to S. cerevisiae metabolites and fermentation environment. Viability kit and recovery analyses on non-culturable cells verified the existence of viable but not-culturable status. These findings are discussed in the context of interaction between non-Saccharomyces and S. cerevisiae.

  11. Selection of Indigenous Saccharomyces cerevisiae Strains from Kutjevo Wine Growing Area at the Laboratoy Scale

    Directory of Open Access Journals (Sweden)

    Sandi Orlić

    2005-09-01

    Full Text Available The use of selected yeasts for winemaking has clear advantages over traditional spontaneous fermentation. Selection of wine yeasts is usually carried out within the Saccharomyces cerevisiae species. Yeast strains produce different amount of secondary compounds that impart specific characteristics to the wines. This suggests that it is necessary to isolate naturally occuring autochthone strains, which exhibit a metabolic profile that corresponds to each wine. Twenty two strains of S.cerevisiae, isolated from the Kutjevo region (Gornji and Donji Hrnjevec, Mitrovac, Graševina grapes, were tested for: fermentation vigor, ethanol resistance, volatile acidity, H2S production and β-glucosidase, polygalacturonase, and killer activity. From the results of this investigation we are able to select two yeast strains (RO 1272 and RO 1284 for more detailed fermentation trials and possible use as a starter culture in production of typical wines.

  12. Producing human ceramide-NS by metabolic engineering using yeast Saccharomyces cerevisiae.

    Science.gov (United States)

    Murakami, Suguru; Shimamoto, Toshi; Nagano, Hideaki; Tsuruno, Masahiro; Okuhara, Hiroaki; Hatanaka, Haruyo; Tojo, Hiromasa; Kodama, Yukiko; Funato, Kouichi

    2015-01-01

    Ceramide is one of the most important intercellular components responsible for the barrier and moisture retention functions of the skin. Because of the risks involved with using products of animal origin and the low productivity of plants, the availability of ceramides is currently limited. In this study, we successfully developed a system that produces sphingosine-containing human ceramide-NS in the yeast Saccharomyces cerevisiae by eliminating the genes for yeast sphingolipid hydroxylases (encoded by SUR2 and SCS7) and introducing the gene for a human sphingolipid desaturase (encoded by DES1). The inactivation of the ceramidase gene YDC1, overexpression of the inositol phosphosphingolipid phospholipase C gene ISC1, and endoplasmic reticulum localization of the DES1 gene product resulted in enhanced production of ceramide-NS. The engineered yeast strains can serve as hosts not only for providing a sustainable source of ceramide-NS but also for developing further systems to produce sphingosine-containing sphingolipids.

  13. A set of haploid strains available for genetic studies of Saccharomyces cerevisiae flor yeasts.

    Science.gov (United States)

    Coi, Anna Lisa; Legras, Jean-Luc; Zara, Giacomo; Dequin, Sylvie; Budroni, Marilena

    2016-09-01

    Flor yeasts of Saccharomyces cerevisiae have been extensively studied for biofilm formation, however the lack of specific haploid model strains has limited the application of genetic approaches such as gene knockout, allelic replacement and Quantitative Trait Locus mapping for the deciphering of the molecular basis of velum formation under biological ageing. The aim of this work was to construct a set of flor isogenic haploid strains easy to manipulate genetically. The analysis of the allelic variations at 12 minisatellite loci of 174 Saccharomyces cerevisiae strains allowed identifying three flor parental strains with different phylogenic positions. These strains were characterized for sporulation efficiency, growth on galactose, adherence to polystyrene, agar invasion, growth on wine and ability to develop a biofilm. Interestingly, the inability to grow on galactose was found associated with a frameshift in GAL4 gene that seems peculiar of flor strains. From these wild flor strains, isogenic haploid strains were constructed by deleting HO gene with a loxP-KanMX-loxP cassette followed by the removal of the kanamycin cassette. Haploid strains obtained were characterized for their phenotypic and genetic properties and compared with the parental strains. Preliminary results showed that the haploid strains represent new tools for genetic studies and breeding programs on biofilm formation. PMID:27527101

  14. Research Progress of "Omics" Technologies and Its Application in Construction of Engineering Strain of Saccharomyces cerevisiae%酿酒酵母的"组学"技术研究进展及其在工程菌株构建中的应用

    Institute of Scientific and Technical Information of China (English)

    张晓阳; 李余动; 吴雪昌

    2011-01-01

    酿酒酵母是真核模式生物,已被广泛用于"组学"水平的研究."组学"技术主要由基因组学、转录组学、蛋白质组学及代谢组学构成.综述了酵母菌"组学"的研究进展,并论述了酵母菌"组学"技术在酵母菌菌株改造中的应用,包括酒类及生物燃料乙醇工业生产菌株的基因工程改造等.%The budding yeast, Saccharomyces cerevisiae, has been used as eukaryotic model organism in "ome" level research. "Omics" technologies were mainly composed of genomics,transcriptomics,proteomics and metabolomics. The recent advancements of "ome" level research in yeast were surveyed,then their application in strain improvement by genetic engineering was discussed,including the industrial yeast strains in bioethanol and winemaking processes.

  15. Social wasp intestines host the local phenotypic variability of Saccharomyces cerevisiae strains.

    Science.gov (United States)

    Dapporto, Leonardo; Stefanini, Irene; Rivero, Damariz; Polsinelli, Mario; Capretti, Paolo; De Marchi, Paolo; Viola, Roberto; Turillazzi, Stefano; Cavalieri, Duccio

    2016-07-01

    Nowadays, the presence of Saccharomyces cerevisiae has been assessed in both wild and human-related environments. Social wasps have been shown to maintain and vector S. cerevisiae among different environments. The availability of strains isolated from wasp intestines represents a striking opportunity to assess whether the strains found in wasp intestines are characterized by peculiar traits. We analysed strains isolated from the intestines of social wasps and compared them with strains isolated from other sources, all collected in a restricted geographic area. We evaluated the production of volatile metabolites during grape must fermentation, the resistance to different stresses and the ability to exploit various carbon sources. Wasp strains, in addition to representing a wide range of S. cerevisiae genotypes, also represent large part of the phenotypes characterizing the sympatric set of yeast strains; their higher production of acetic acid and ethyl acetate could reflect improved ability to attract insects. Our findings suggest that the relationship between yeasts and wasps should be preserved, to safeguard not only the natural variance of this microorganism but also the interests of wine-makers, who could take advantage from the exploitation of their phenotypic variability. Copyright © 2016 John Wiley & Sons, Ltd. PMID:27168222

  16. PHO13 deletion-induced transcriptional activation prevents sedoheptulose accumulation during xylose metabolism in engineered Saccharomyces cerevisiae.

    Science.gov (United States)

    Xu, Haiqing; Kim, Sooah; Sorek, Hagit; Lee, Youngsuk; Jeong, Deokyeol; Kim, Jungyeon; Oh, Eun Joong; Yun, Eun Ju; Wemmer, David E; Kim, Kyoung Heon; Kim, Soo Rin; Jin, Yong-Su

    2016-03-01

    The deletion of PHO13 (pho13Δ) in Saccharomyces cerevisiae, encoding a phosphatase enzyme of unknown specificity, results in the transcriptional activation of genes related to the pentose phosphate pathway (PPP) such as TAL1 encoding transaldolase. It has been also reported that the pho13Δ mutant of S. cerevisiae expressing a heterologous xylose pathway can metabolize xylose efficiently compared to its parental strain. However, the interaction between the pho13Δ-induced transcriptional changes and the phenotypes of xylose fermentation was not understood. Thus we investigated the global metabolic changes in response to pho13Δ when cells were exponentially growing on xylose. Among the 134 intracellular metabolites that we identified, the 98% reduction of sedoheptulose was found to be the most significant change in the pho13Δ mutant as compared to its parental strain. Because sedoheptulose-7-phosphate (S7P), a substrate of transaldolase, reduced significantly in the pho13Δ mutant as well, we hypothesized that limited transaldolase activity in the parental strain might cause dephosphorylation of S7P, leading to carbon loss and inefficient xylose metabolism. Mutants overexpressing TAL1 at different degrees were constructed, and their TAL1 expression levels and xylose consumption rates were positively correlated. Moreover, as TAL1 expression levels increased, intracellular sedoheptulose concentration dropped significantly. Therefore, we concluded that TAL1 upregulation, preventing the accumulation of sedoheptulose, is the most critical mechanism for the improved xylose metabolism by the pho13Δ mutant of engineered S. cerevisiae.

  17. Historical Evolution of Laboratory Strains of Saccharomyces cerevisiae.

    Science.gov (United States)

    Louis, Edward J

    2016-01-01

    Budding yeast strains used in the laboratory have had a checkered past. Historically, the choice of strain for any particular experiment depended on the suitability of the strain for the topic of study (e.g., cell cycle vs. meiosis). Many laboratory strains had poor fermentation properties and were not representative of the robust strains used for domestic purposes. Most strains were related to each other, but investigators usually had only vague notions about the extent of their relationships. Isogenicity was difficult to confirm before the advent of molecular genetic techniques. However, their ease of growth and manipulation in laboratory conditions made them "the model" model organism, and they still provided a great deal of fundamental knowledge. Indeed, more than one Nobel Prize has been won using them. Most of these strains continue to be powerful tools, and isogenic derivatives of many of them-including entire collections of deletions, overexpression constructs, and tagged gene products-are now available. Furthermore, many of these strains are now sequenced, providing intimate knowledge of their relationships. Recent collections, new isolates, and the creation of genetically tractable derivatives have expanded the available strains for experiments. But even still, these laboratory strains represent a small fraction of the diversity of yeast. The continued development of new laboratory strains will broaden the potential questions that can be posed. We are now poised to take advantage of this diversity, rather than viewing it as a detriment to controlled experiments. PMID:27371602

  18. Directed evolution of pyruvate decarboxylase-negative Saccharomyces cerevisiae, yielding a C2-independent, glucose-tolerant, and pyruvate-hyperproducing yeast

    NARCIS (Netherlands)

    A.J. van Maris; J.M. Geertman; A. Vermeulen; M.K. Groothuizen; A.A. Winkler; M.D. Piper; J.P. van Dijken; J.T. Pronk

    2004-01-01

    textabstractThe absence of alcoholic fermentation makes pyruvate decarboxylase-negative (Pdc(-)) strains of Saccharomyces cerevisiae an interesting platform for further metabolic engineering of central metabolism. However, Pdc(-) S. cerevisiae strains have two growth defects:

  19. An efficient xylose-fermenting recombinant Saccharomyces cerevisiae strain obtained through adaptive evolution and its global transcription profile

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Yu; Chen, Xiao; Peng, Bingyin; Chen, Liyuan; Hou, Jin; Bao, Xiaoming [Shandong Univ., Jinan (China). State Key Lab. of Microbial Technology

    2012-11-15

    Factors related to ethanol production from xylose in engineered Saccharomyces cerevisiae that contain an exogenous initial metabolic pathway are still to be elucidated. In the present study, a strain that expresses the xylose isomerase gene of Piromyces sp. Pi-xylA and overexpresses XKS1, RPE1, RKI1, TAL1, and TKL1, with deleted GRE3 and COX4 genes was constructed. The xylose utilization capacity of the respiratory deficiency strain was poor but improved via adaptive evolution in xylose. The {mu}{sub max} of the evolved strain in 20 gl{sup -1} xylose is 0.11 {+-} 0.00 h{sup -1}, and the evolved strain consumed 17.83 gl{sup -1} xylose within 72 h, with an ethanol yield of 0.43 gg{sup -1} total consumed sugars during glucose-xylose cofermentation. Global transcriptional changes and effect of several specific genes were studied. The result revealed that the increased xylose isomerase activity, the upregulation of enzymes involved in glycolysis and glutamate synthesis, and the downregulation of trehalose and glycogen synthesis, may have contributed to the improved xylose utilization of the strain. Furthermore, the deletion of PHO13 decreased the xylose growth in the respiration deficiency strain although deleting PHO13 can improve the xylose metabolism in other strains. (orig.)

  20. Comparison between two selected Saccharomyces cerevisiae strains as fermentation starters in the production of traditional cachaça

    Directory of Open Access Journals (Sweden)

    Fátima de Cássia Oliveira Gomes

    2009-04-01

    Full Text Available Two Saccharomyces cerevisiae strains were tested as the starter yeasts in a traditional cachaça distillery. The strains used were S. cerevisiae UFMG-A829, isolated from a cachaça fermentation process, and S. cerevisiae K1-V1116, obtained from the wine industry. The permanence of each strain in the fermentation must was determined by RAPD (Random Amplified Polymorphic DNA-PCR, with primer M13. Both yeast strains were prevalent in the vats for approximately 30 days. Indigenous non-Saccharomyces and indigenous S. cerevisiae strains were isolated in lower counts during the fermentation period. Indigenous S. cerevisiae strains were molecularly distinct when compared to the starter yeasts. The two yeasts appeared promising starter yeasts in the fermentation process to produce traditional cachaça.Duas linhagens de Saccharomyces cerevisiae foram testadas como iniciadoras em uma destilaria de cachaça. Foram utilizadas as linhagens de S. cerevisiae UFMG-A829, isolada de fermentação de cachaça, e S. cerevisiae K1-V1116, de origem vinícola. A permanência de cada linhagem durante a fermentação foi determinada por RAPD (Random Amplified Polymorphic DNA-PCR, utilizando o iniciador M13. As duas linhagens predominaram nas dornas de fermentação por aproximadamente 30 dias. Leveduras não-Saccharomyces e S. cerevisiae indígenas foram isoladas em menor proporção durante o experimento. As linhagens de S. cerevisiae indígenas apresentaram perfis moleculares distintos em relação às linhagens iniciadoras. As duas linhagens foram promissoras para serem utilizadas como iniciadoras do processo fermentativo para a produção da cachaça.

  1. Whole genome sequencing of Saccharomyces cerevisiae: from genotype to phenotype for improved metabolic engineering applications

    Directory of Open Access Journals (Sweden)

    Asadollahi Mohammad A

    2010-12-01

    Full Text Available Abstract Background The need for rapid and efficient microbial cell factory design and construction are possible through the enabling technology, metabolic engineering, which is now being facilitated by systems biology approaches. Metabolic engineering is often complimented by directed evolution, where selective pressure is applied to a partially genetically engineered strain to confer a desirable phenotype. The exact genetic modification or resulting genotype that leads to the improved phenotype is often not identified or understood to enable further metabolic engineering. Results In this work we performed whole genome high-throughput sequencing and annotation can be used to identify single nucleotide polymorphisms (SNPs between Saccharomyces cerevisiae strains S288c and CEN.PK113-7D. The yeast strain S288c was the first eukaryote sequenced, serving as the reference genome for the Saccharomyces Genome Database, while CEN.PK113-7D is a preferred laboratory strain for industrial biotechnology research. A total of 13,787 high-quality SNPs were detected between both strains (reference strain: S288c. Considering only metabolic genes (782 of 5,596 annotated genes, a total of 219 metabolism specific SNPs are distributed across 158 metabolic genes, with 85 of the SNPs being nonsynonymous (e.g., encoding amino acid modifications. Amongst metabolic SNPs detected, there was pathway enrichment in the galactose uptake pathway (GAL1, GAL10 and ergosterol biosynthetic pathway (ERG8, ERG9. Physiological characterization confirmed a strong deficiency in galactose uptake and metabolism in S288c compared to CEN.PK113-7D, and similarly, ergosterol content in CEN.PK113-7D was significantly higher in both glucose and galactose supplemented cultivations compared to S288c. Furthermore, DNA microarray profiling of S288c and CEN.PK113-7D in both glucose and galactose batch cultures did not provide a clear hypothesis for major phenotypes observed, suggesting that

  2. Ethanol production from lignocellulosic hydrolysates using engineered Saccharomyces cerevisiae harboring xylose isomerase-based pathway.

    Science.gov (United States)

    Ko, Ja Kyong; Um, Youngsoon; Woo, Han Min; Kim, Kyoung Heon; Lee, Sun-Mi

    2016-06-01

    The efficient co-fermentation of glucose and xylose is necessary for the economically feasible bioethanol production from lignocellulosic biomass. Even with xylose utilizing Saccharomyces cerevisiae, the efficiency of the lignocellulosic ethanol production remains suboptimal mainly due to the low conversion yield of xylose to ethanol. In this study, we evaluated the co-fermentation performances of SXA-R2P-E, a recently engineered isomerase-based xylose utilizing strain, in mixed sugars and in lignocellulosic hydrolysates. In a high-sugar fermentation with 70g/L of glucose and 40g/L of xylose, SXA-R2P-E produced 50g/L of ethanol with an yield of 0.43gethanol/gsugars at 72h. From dilute acid-pretreated hydrolysates of rice straw and hardwood (oak), the strain produced 18-21g/L of ethanol with among the highest yield of 0.43-0.46gethanol/gsugars ever reported. This study shows a highly promising potential of a xylose isomerase-expressing strain as an industrially relevant ethanol producer from lignocellulosic hydrolysates. PMID:26990396

  3. Selection of Saccharomyces cerevisiae strains for efficient very high gravity bio-ethanol fermentation processes

    OpenAIRE

    Pereira, Francisco B; Guimarães, Pedro M. R.; J. A. Teixeira; Domingues, Lucília

    2010-01-01

    Abstract An optimized very high gravity (VHG) glucose medium supplemented with low cost nutrient sources was used to evaluate bio-ethanol production by 11 Saccharomyces cerevisiae strains. The industrial strains PE-2 and CA1185 exhibited the best overall fermentation performance, producing an ethanol titre of 19.2% (v/v) corresponding to a batch productivity of 2.5 g l?1 h?1, while the best laboratory strain (CEN.PK 113-7D) produced 17.5% (v/v) ethanol with a productivity of 1.7 g ...

  4. Construction of Saccharomyces cerevisiae Strains Improved Stress Tolerance and Ethanol Fermentation Performance through Metabolic Engineering and Genome Recombination%代谢工程与全基因组重组构建酿酒酵母抗逆高产乙醇菌株

    Institute of Scientific and Technical Information of China (English)

    张晓阳; 杜风光; 池小琴; 王品美; 郑道琼; 吴雪昌

    2011-01-01

    Some environmental stresses. i. e. , high osmotic stress, fluctuating temperature and ethanol concentration, will greatly influence the viability and capability of the yeast S. cerevisiae strains during ethanol fermentation. In this study, we constructed a series of yeast strains with improved stress tolerances and ethanol fermentation performance through trehalose metabolism engineering combined with hybridization-based whole genome recombination. Firstly, two haploid strains , Z1 and Z2 isolated from the diploid strain 2d4, were engineered to enhance the intracellular trehalose by ( 1 ) overexpression of trehalose-6-phosphate synthase gene TPS1 (Z1ptps1 and Z2ptps1 ) , (2) deletion of acidic trehalase gene ATH1 (Z1Δath1 and Z2Δath1 ) , and (3)TPS1 overexpression combined with ATH1 deletion ( Z1pTΔA and Z2pTΔA ) . We then obtained four recombination strains (Z12, Z12ptps1 , Z12Δath1 and Z12pTΔA) through the hybridization of Z1 and Z2 , and their engineered strains. The results of high-gravity fermentation (270 g/L glucose) showed that TPS1 overexpression combined with ATH1 deletion had a distinct advantage in the improvement of stress tolerance over the single genetic manipulation. Compared to the original strain Zd4 and Z12, the strain Z12pTΔA ( the hybrid of Z1pTΔA and Z2pTΔA) improved the fermentation rate by 11.4% and ethanol yield by 7. 0% , while the strain Z12 without metabolic engineering only increased the main fermentation rate by 4. 8% and ethanol yield by 2. 8% . These improvements of fermentation performance consisted with their tolerances of the constructed strains under the conditions with osmotic pressure, high temperature and high concentration of ethanol. The combination of trehalose metabolic engineering and genome recombinant technology could effectively improve the stress tolerance and the ethanol fermentation performance of the industrial S. cerevisiae strains is demonstrated, and an innovative strategy for industrial yeast

  5. Draft Genome Sequence of Saccharomyces cerevisiae Strain NCIM3186 Used in the Production of Bioethanol from Sweet Sorghum

    OpenAIRE

    Sravanthi Goud, Burragoni; Ulaganathan, Kandasamy

    2015-01-01

    Here, we report the draft genome sequence of Saccharomyces cerevisiae strain NCIM3186 used in bioethanol production from sweet sorghum. The size of the genome is approximately 11.9 Mb and contains 5,347 protein-coding genes.

  6. Production of volatile and sulfur compounds by ten Saccharomyces cerevisiae strains inoculated in Trebbiano must

    Directory of Open Access Journals (Sweden)

    Francesca ePatrignani

    2016-03-01

    Full Text Available In wines, the presence of sulphur compounds is the resulting of several contributions among which yeast metabolism. The characterization of the starter Saccharomyces cerevisiae needs to be performed also taking into account this ability even if evaluated together with the overall metabolic profile. In this perspective, principal aim of this experimental research was the evaluation of the volatile profiles, throughout GC/MS technique coupled with solid phase micro extraction, of wines obtained throughout the fermentation of 10 strains of Saccharomyces cerevisiae. In addition, the production of sulphur compounds was further evaluated by using a gas-chromatograph coupled with a Flame Photometric Detector. Specifically, the ten strains were inoculated in Trebbiano musts and the fermentations were monitored for 19 days. In the produced wines, volatile and sulphur compounds as well as amino acid concentrations were investigated. Also the physico-chemical characteristics of the wines and their electronic nose profiles were evaluated.

  7. Production of Volatile and Sulfur Compounds by 10 Saccharomyces cerevisiae Strains Inoculated in Trebbiano Must.

    Science.gov (United States)

    Patrignani, Francesca; Chinnici, Fabio; Serrazanetti, Diana I; Vernocchi, Pamela; Ndagijimana, Maurice; Riponi, Claudio; Lanciotti, Rosalba

    2016-01-01

    In wines, the presence of sulfur compounds is the resulting of several contributions among which yeast metabolism. The characterization of the starter Saccharomyces cerevisiae needs to be performed also taking into account this ability even if evaluated together with the overall metabolic profile. In this perspective, principal aim of this experimental research was the evaluation of the volatile profiles, throughout GC/MS technique coupled with solid phase micro extraction, of wines obtained throughout the fermentation of 10 strains of S. cerevisiae. In addition, the production of sulfur compounds was further evaluated by using a gas-chromatograph coupled with a Flame Photometric Detector. Specifically, the 10 strains were inoculated in Trebbiano musts and the fermentations were monitored for 19 days. In the produced wines, volatile and sulfur compounds as well as amino acid concentrations were investigated. Also the physico-chemical characteristics of the wines and their electronic nose profiles were evaluated. PMID:26973621

  8. Genome Sequencing and Comparative Analysis of Saccharomyces cerevisiae Strains of the Peterhof Genetic Collection

    Science.gov (United States)

    Drozdova, Polina B.; Tarasov, Oleg V.; Matveenko, Andrew G.; Radchenko, Elina A.; Sopova, Julia V.; Polev, Dmitrii E.; Inge-Vechtomov, Sergey G.; Dobrynin, Pavel V.

    2016-01-01

    The Peterhof genetic collection of Saccharomyces cerevisiae strains (PGC) is a large laboratory stock that has accumulated several thousands of strains for over than half a century. It originated independently of other common laboratory stocks from a distillery lineage (race XII). Several PGC strains have been extensively used in certain fields of yeast research but their genomes have not been thoroughly explored yet. Here we employed whole genome sequencing to characterize five selected PGC strains including one of the closest to the progenitor, 15V-P4, and several strains that have been used to study translation termination and prions in yeast (25-25-2V-P3982, 1B-D1606, 74-D694, and 6P-33G-D373). The genetic distance between the PGC progenitor and S288C is comparable to that between two geographically isolated populations. The PGC seems to be closer to two bakery strains than to S288C-related laboratory stocks or European wine strains. In genomes of the PGC strains, we found several loci which are absent from the S288C genome; 15V-P4 harbors a rare combination of the gene cluster characteristic for wine strains and the RTM1 cluster. We closely examined known and previously uncharacterized gene variants of particular strains and were able to establish the molecular basis for known phenotypes including phenylalanine auxotrophy, clumping behavior and galactose utilization. Finally, we made sequencing data and results of the analysis available for the yeast community. Our data widen the knowledge about genetic variation between Saccharomyces cerevisiae strains and can form the basis for planning future work in PGC-related strains and with PGC-derived alleles. PMID:27152522

  9. Adaptation of a flocculent Saccharomyces cerevisiae strain to lignocellulosic inhibitors by cell recycle batch fermentation

    OpenAIRE

    Landaeta, R.; Aroca, G.; Acevedo, F.; J. A. Teixeira; Mussatto, Solange I.

    2013-01-01

    The ethanol production from lignocellulosic feedstocks is considered a promising strategy to increase global production of biofuels without impacting food supplies. However, some compounds released during the hydrolysis of lignocellulosic materials are toxic for the microbial metabolism, causing low ethanol yield and productivity during the fermentation. As an attempt to overcome this problem, the present study evaluated the adaptation of a flocculent strain of Saccharomyces cerevisiae (NRRL ...

  10. Improving Stress Tolerance in Industrial Saccharomyces cerevisiae Strains for Ethanol Production from Lignocellulosic Biomass

    OpenAIRE

    Wallace, Valeria

    2014-01-01

    The present work was aimed at developing industrial S. cerevisiae strains with improved tolerance to two types of stressors encountered during the fermentation of lignocellulosic biomass that affect ethanol yield and productivity, namely hydrolysate-derived inhibitors and high temperature, and at understanding the response of yeast and mechanisms of adaptation to such stressors. In one part of the study, key amino acid substitutions that were responsible for the acquired ability of a mutated ...

  11. Genome-wide analysis of nucleotide-level variation in commonly used Saccharomyces cerevisiae strains.

    Directory of Open Access Journals (Sweden)

    Joseph Schacherer

    Full Text Available Ten years have passed since the genome of Saccharomyces cerevisiae-more precisely, the S288c strain-was completely sequenced. However, experimental work in yeast is commonly performed using strains that are of unknown genetic relationship to S288c. Here, we characterized the nucleotide-level similarity between S288c and seven commonly used lab strains (A364A, W303, FL100, CEN.PK, summation 1278b, SK1 and BY4716 using 25mer oligonucleotide microarrays that provide complete and redundant coverage of the approximately 12 Mb Saccharomyces cerevisiae genome. Using these data, we assessed the frequency and distribution of nucleotide variation in comparison to the sequenced reference genome. These data allow us to infer the relationships between experimentally important strains of yeast and provide insight for experimental designs that are sensitive to sequence variation. We propose a rational approach for near complete sequencing of strains related to the reference using these data and directed re-sequencing. These data and new visualization tools are accessible online in a new resource: the Yeast SNPs Browser (YSB; http://gbrowse.princeton.edu/cgi-bin/gbrowse/yeast_strains_snps that is available to all researchers.

  12. Metabolic engineering of Saccharomyces cerevisiae for the production of 2-phenylethanol via Ehrlich pathway.

    Science.gov (United States)

    Kim, Bosu; Cho, Bo-Ram; Hahn, Ji-Sook

    2014-01-01

    2-Phenylethanol (2-PE), a fragrance compound with a rose-like odor, is widely used in perfumery and cosmetics. Here, we report the first metabolic engineering approach for 2-PE production in Saccharomyces cerevisiae. 2-PE can be produced from the catabolism of L-phenylalanine via Ehrlich pathway, consisting of transamination to phenylpyruvate by Aro9, decarboxylation to phenylacetaldehyde by Aro10, and reduction to 2-PE by alcohol dehydrogenases. We demonstrated that Ald3 is mainly responsible for phenylacetaldehyde oxidation, competing with 2-PE production. ALD3 deletion strain overexpressing ARO9 and ARO10 both by episomal overexpression and by induction of the endogenous genes through overexpression of Aro80 transcription factor, produced 4.8 g/L 2-PE in a medium containing 10 g/L L-phenylalanine as a sole nitrogen source. Considering the cytotoxicity of 2-PE, this production titer is almost the upper limit that can be reached in batch cultures, suggesting the great potential of this yeast strain for 2-PE production. 2-PE production was further increased by applying two-phase fermentation method with polypropylene glycol 1200 as an extractant, reaching 6.1 g/L 2-PE in organic phase with the molar yield of 82.5%, which is about ninefold increase compared with wild type. PMID:23836015

  13. Engineering the oxygen sensing regulation results in an enhanced recombinant human hemoglobin production by Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Martínez, José L.; Liu, Lifang; Petranovic, Dina;

    2015-01-01

    engineering also allowed the generation of different genetically modified organisms for the production of recombinant human hemoglobin. Several studies have showed very promising results using the bacterium Escherichia coli as a production platform, reporting hemoglobin titers above 5% of the total cell...... the generation of a set of plasmids to produce functional human hemoglobin in Saccharomyces cerevisiae, with final titers of active hemoglobin exceeding 4% of the total cell protein. In this study, we propose a strategy for further engineering S. cerevisiae by altering the oxygen sensing pathway by deleting...

  14. Improving biomass sugar utilization by engineered Saccharomyces cerevisiae

    Science.gov (United States)

    The efficient utilization of all available sugars in lignocellulosic biomass, which is more abundant than available commodity crops and starch, represents one of the most difficult technological challenges for the production of bioethanol. The well-studied yeast Saccharomyces cerevisiae has played a...

  15. Functional expression of xylose isomerase in flocculating industrial Saccharomyces cerevisiae strain for bioethanol production.

    Science.gov (United States)

    Li, Yun-Cheng; Li, Guo-Ying; Gou, Min; Xia, Zi-Yuan; Tang, Yue-Qin; Kida, Kenji

    2016-06-01

    Saccharomyces cerevisiae strains with xylose isomerase (XI) pathway were constructed using a flocculating industrial strain (YC-8) as the host. Both strains expressing wild-type xylA (coding XI) from the fungus Orpinomyces sp. and the bacterium Prevotella ruminicola, respectively, showed better growth ability and fermentation capacity when using xylose as the sole sugar than most of the reported strains expressing XI. Codon optimization of both XIs did not improve the xylose fermentation ability of the strains. Adaption significantly increased XI activity resulting in improved growth and fermentation. The strains expressing codon-optimized XI showed a higher increase in xylose consumption and ethanol production compared to strains expressing wild XI. Among all strains, the adapted strain YCPA2E expressing XI from P. ruminicola showed the best performance in the fermentation of xylose to ethanol. After 48 h of fermentation, YCPA2E assimilated 16.95 g/L xylose and produced 6.98 g/L ethanol. These results indicate that YC-8 is a suitable host strain for XI expression, especially for the codon-optimized XI originating from P. ruminicola. PMID:26645659

  16. Growth temperature exerts differential physiological and transcriptional responses in laboratory and wine strains of Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Pizarra, Francisco J.; Jewett, Michael Christopher; Nielsen, Jens;

    2008-01-01

    environmental conditions and the organoleptic properties that they confer to wine. Here, we used a two-factor design to study the responses of a standard laboratory strain, CEN.PK113-7D, and an industrial wine yeast strain, EC1118, to growth temperatures of 15 degrees C and 30 degrees C in nitrogen......Laboratory strains of Saccharomyces cerevisiae have been widely used as a model for studying eukaryotic cells and mapping the molecular mechanisms of many different human diseases. Industrial wine yeasts, on the other hand, have been selected on the basis of their adaptation to stringent......-limited, anaerobic, steady-state chemostat cultures. Physiological characterization revealed that the growth temperature strongly impacted the biomass yield of both strains. Moreover, we found that the wine yeast was better adapted to mobilizing resources for biomass production and that the laboratory yeast...

  17. A fast method to diagnose chromosome and plasmid loss in Saccharomyces cerevisiae strains.

    Science.gov (United States)

    Hegemann, J H; Klein, S; Heck, S; Güldener, U; Niedenthal, R K; Fleig, U

    1999-07-01

    We have developed a simple, fast and reliable method for the analysis of genetic stability in budding yeast strains. The assay relies on our previous finding that cells expressing the green fluorescent protein (GFP) can be detected and counted by flow cytometric analysis (FACS) (Niedenthal et al., 1996). Expression of a gfp-carrying CEN-plasmid in a wild-type strain resulted in the emission of strong fluorescence from 80% of the cell population. Strong fluorescence and presence of the plasmid, determined by the presence of the URA3 genetic marker, was strictly correlated. Expression of this plasmid in 266 yeast strains, each carrying a complete deletion of a novel, non-essential gene identified in the S. cerevisiae sequencing project, pinpointed 12 strains with an increased level of mitotic plasmid loss. Finally we have shown that measurement of mitotic loss of artificial chromosome fragments equipped with the gfp expression cassette can be performed quantitatively using FACS.

  18. Enhancing beta-carotene production in Saccharomyces cerevisiae by metabolic engineering.

    Science.gov (United States)

    Li, Qian; Sun, Zhiqiang; Li, Jing; Zhang, Yansheng

    2013-08-01

    Beta-carotene is known to exhibit a number of pharmacological and nutraceutical benefits to human health. Metabolic engineering of beta-carotene biosynthesis in Saccharomyces cerevisiae has been attracting the interest of many researchers. A previous work has shown that S. cerevisiae successfully integrated with phytoene synthase (crtYB) and phytoene desaturase (crtI) from Xanthophyllomyces dendrorhous could produce beta-carotene. In the present study, we achieved around 200% improvement in beta-carotene production in S. cerevisiae through specific site optimization of crtI and crtYB, in which five codons of crtI and eight codons of crtYB were rationally mutated. Furthermore, the effects of the truncated HMG-CoA reductase (tHMG1) from S. cerevisiae and HMG-CoA reductase (mva) from Staphylococcus aureus on the production of beta-carotene in S. cerevisiae were also evaluated. Our results indicated that mva from a prokaryotic organism might be more effective than tHMG1 for beta-carotene production in S. cerevisiae. PMID:23718229

  19. Synthesis of FAEEs from glycerol in engineered Saccharomyces cerevisiae using endogenously produced ethanol by heterologous expression of an unspecific bacterial acyltransferase.

    Science.gov (United States)

    Yu, Kyung Ok; Jung, Ju; Kim, Seung Wook; Park, Chul Hwan; Han, Sung Ok

    2012-01-01

    The high price of petroleum-based diesel fuel has led to the development of alternative fuels, such as ethanol. Saccharomyces cerevisiae was metabolically engineered to utilize glycerol as a substrate for ethanol production. For the synthesis of fatty acid ethyl esters (FAEEs) by engineered S. cerevisiae that utilize glycerol as substrate, heterologous expression of an unspecific acyltransferase from Acinetobacter baylyi with glycerol utilizing genes was established. As a result, the engineered YPH499 (pGcyaDak, pGupWs-DgaTCas) strain produced 0.24 g/L FAEEs using endogenous ethanol produced from glycerol. And this study also demonstrated the possibility of increasing FAEE production by enhancing ethanol production by minimizing the synthesis of glycerol. The overall FAEE production in strain YPH499 fps1Δ gpd2Δ (pGcyaDak, pGupWs-DgaTCas) was 2.1-fold more than in YPH499 (pGcyaDak, pGupWs-DgaTCas), with approximately 0.52 g/L FAEEs produced, while nearly 17 g/L of glycerol was consumed. These results clearly indicated that FAEEs were synthesized in engineered S. cerevisiae by esterifying exogenous fatty acids with endogenously produced ethanol from glycerol. This microbial system acts as a platform in applying metabolic engineering that allows the production of FAEEs from cheap and abundant substrates specifically glycerol through the use of endogenous bioethanol.

  20. Benchmarking two commonly used Saccharomyces cerevisiae strains for heterologous vanillin-β-glucoside production

    Directory of Open Access Journals (Sweden)

    Tomas Strucko

    2015-12-01

    Full Text Available The yeast Saccharomyces cerevisiae is a widely used eukaryotic model organism and a key cell factory for production of biofuels and wide range of chemicals. From the broad palette of available yeast strains, the most popular are those derived from laboratory strain S288c and the industrially relevant CEN.PK strain series. Importantly, in recent years these two strains have been subjected to comparative “-omics” analyzes pointing out significant genotypic and phenotypic differences. It is therefore possible that the two strains differ significantly with respect to their potential as cell factories for production of specific compounds. To examine this possibility, we have reconstructed a de novo vanillin-β-glucoside pathway in an identical manner in S288c and CEN.PK strains. Characterization of the two resulting strains in two standard conditions revealed that the S288c background strain produced up to 10-fold higher amounts of vanillin-β-glucoside compared to CEN.PK. This study demonstrates that yeast strain background may play a major role in the outcome of newly developed cell factories for production of a given product.

  1. Thermotolerant Kluyveromyces marxianus and Saccharomyces cerevisiae strains representing potentials for bioethanol production from Jerusalem artichoke by consolidated bioprocessing

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Nan [Agricultural Univ., Qingdao, SD (China). College of Animal Science and Technology; Chinese Academy of Sciences, Qingdao, SD (China). Key Lab. of Biofuels; Yuan, Bo; Wang, Shi-An; Li, Fu-Li [Chinese Academy of Sciences, Qingdao, SD (China). Key Lab. of Biofuels; Sun, Juan [Agricultural Univ., Qingdao, SD (China). College of Animal Science and Technology

    2012-09-15

    Thermotolerant inulin-utilizing yeast strains are desirable for ethanol production from Jerusalem artichoke tubers by consolidated bioprocessing (CBP). To obtain such strains, 21 naturally occurring yeast strains isolated by using an enrichment method and 65 previously isolated Saccharomyces cerevisiae strains were investigated in inulin utilization, extracellular inulinase activity, and ethanol fermentation from inulin and Jerusalem artichoke tuber flour at 40 C. The strains Kluyveromyces marxianus PT-1 (CGMCC AS2.4515) and S. cerevisiae JZ1C (CGMCC AS2.3878) presented the highest extracellular inulinase activity and ethanol yield in this study. The highest ethanol concentration in Jerusalem artichoke tuber flour fermentation (200 g L{sup -1}) at 40 C achieved by K. marxianus PT-1 and S. cerevisiae JZ1C was 73.6 and 65.2 g L{sup -1}, which corresponded to the theoretical ethanol yield of 90.0 and 79.7 %, respectively. In the range of 30 to 40 C, temperature did not have a significant effect on ethanol production for both strains. This study displayed the distinctive superiority of K. marxianus PT-1 and S. cerevisiae JZ1C in the thermotolerance and utilization of inulin-type oligosaccharides reserved in Jerusalem artichoke tubers. It is proposed that both K. marxianus and S. cerevisiae have considerable potential in ethanol production from Jerusalem artichoke tubers by a high temperature CBP. (orig.)

  2. Engineering piezoresistivity using biaxially strained silicon

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Richter, Jacob; Brandbyge, Mads;

    2008-01-01

    We calculate the shear piezocoefficient of p-type silicon with grown-in biaxial strain using a 66 k·p method. We find a significant increase in the value of the shear piezocoefficient for compressive grown-in biaxial strain, while tensile strain decreases the piezocoefficient. The dependence...... of the piezocoefficient on temperature and dopant density is altered qualitatively for strained silicon. In particular, we find that a vanishing temperature coefficient may result for silicon with grown-in biaxial tensile strain. These results suggest that strained silicon may be used to engineer the iezoresistivity...

  3. Engineering the pentose phosphate pathway of Saccharomyces cerevisiae for production of ethanol and xylitol

    OpenAIRE

    Toivari, Mervi

    2007-01-01

    The baker s yeast Saccharomyces cerevisiae has a long tradition in alcohol production from D-glucose of e.g. starch. However, without genetic modifications it is unable to utilise the 5-carbon sugars D-xylose and L arabinose present in plant biomass. In this study, one key metabolic step of the catabolic D-xylose pathway in recombinant D-xylose-utilising S. cerevisiae strains was studied. This step, carried out by xylulokinase (XK), was shown to be rate-limiting, because overexpression of the...

  4. Engineering of carbon catabolite repression in recombinant xylose fermenting Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Roca, Christophe Francois Aime; Haack, Martin Brian; Olsson, Lisbeth

    2004-01-01

    Two xylose-fermenting glucose-derepressed Saccharomyces cerevisiae strains were constructed in order to investigate the influence of carbon catabolite repression on xylose metabolism. S. cerevisiae CPB.CR2 (Deltamig1, XYL1, XYL2, XKS1) and CPB.MBH2 (Deltamig1, Deltamig2, XYL1, XYL2, XKS1) were...... of CPB.CR2, where the cells are assumed to grow under non-repressive conditions as they sense almost no glucose, invertase activity was lower during growth on xylose and glucose than on glucose only. The 3-fold reduction in invertase activity could only be attributed to the presence of xylose, suggesting...

  5. Genetic diversity and population structure of Saccharomyces cerevisiae strains isolated from different grape varieties and winemaking regions

    OpenAIRE

    Dorit Schuller; Filipa Cardoso; Susana Sousa; Paula Gomes; Gomes, Ana C.; Santos, Manuel A. S.; Margarida Casal

    2012-01-01

    We herein evaluate intraspecific genetic diversity of fermentative vineyard-associated S. cerevisiae strains and evaluate relationships between grape varieties and geographical location on populational structures. From the musts obtained from 288 grape samples, collected from two wine regions (16 vineyards, nine grape varieties), 94 spontaneous fermentations were concluded and 2820 yeast isolates were obtained that belonged mainly (92%) to the species S. cerevisiae. Isolates were classified i...

  6. Engineering Saccharomyces cerevisiae for consolidated bioprocessing in starch and biomass conversion

    Science.gov (United States)

    The conversion of starch or biomass to biofuel is a two-stage process involving enzymatic treatment, followed by yeast fermentation. An alternative route would be to consolidate the process by engineering Saccharomyces cerevisiae capable of both saccharification and fermentation. An approach was d...

  7. Raspberry wine fermentation with suspended and immobilized yeast cells of two strains of Saccharomyces cerevisiae.

    Science.gov (United States)

    Djordjević, Radovan; Gibson, Brian; Sandell, Mari; de Billerbeck, Gustavo M; Bugarski, Branko; Leskošek-Čukalović, Ida; Vunduk, Jovana; Nikićević, Ninoslav; Nedović, Viktor

    2015-01-01

    The objectives of this study were to assess the differences in fermentative behaviour of two different strains of Saccharomyces cerevisiae (EC1118 and RC212) and to determine the differences in composition and sensory properties of raspberry wines fermented with immobilized and suspended yeast cells of both strains at 15 °C. Analyses of aroma compounds, glycerol, acetic acid and ethanol, as well as the kinetics of fermentation and a sensory evaluation of the wines, were performed. All fermentations with immobilized yeast cells had a shorter lag phase and faster utilization of sugars and ethanol production than those fermented with suspended cells. Slower fermentation kinetics were observed in all the samples that were fermented with strain RC212 (suspended and immobilized) than in samples fermented with strain EC1118. Significantly higher amounts of acetic acid were detected in all samples fermented with strain RC212 than in those fermented with strain EC1118 (0.282 and 0.602 g/l, respectively). Slightly higher amounts of glycerol were observed in samples fermented with strain EC1118 than in those fermented with strain RC212.

  8. Strain engineering of graphene: a review

    Science.gov (United States)

    Si, Chen; Sun, Zhimei; Liu, Feng

    2016-02-01

    Graphene has intrigued the science community by many unique properties not found in conventional materials. In particular, it is the strongest two-dimensional material ever measured, being able to sustain reversible tensile elastic strain larger than 20%, which yields an interesting possibility to tune the properties of graphene by strain and thus opens a new field called ``straintronics''. In this article, the current progress in the strain engineering of graphene is reviewed. We first summarize the strain effects on the electronic structure and Raman spectra of graphene. We then highlight the electron-phonon coupling greatly enhanced by the biaxial strain and the strong pseudomagnetic field induced by the non-uniform strain with specific distribution. Finally, the potential application of strain-engineering in the self-assembly of foreign atoms on the graphene surface is also discussed. Given the short history of graphene straintronics research, the current progress has been notable, and many further advances in this field are expected.

  9. Comparative Study on Two Commercial Strains of Saccharomyces cerevisiae for Optimum Ethanol Production on Industrial Scale

    Directory of Open Access Journals (Sweden)

    K. Mukhtar

    2010-01-01

    Full Text Available Two commercial strains of Saccharomyces cerevisiae, Saf-Instant (Baker's yeast and Ethanol red (Mutant were compared for ethanol production during hot summer season, using molasses diluted up to 6-7∘ Brix containing 4%-5% sugars. The yeasts were then propagated in fermentation vessels to study the effects of yeast cell count and varying concentrations of Urea, DAP, inoculum size and Lactrol (Antibiotic. Continuous circulation of mash was maintained for 24 hours and after this fermenter was allowed to stay for a period of 16 hours to give time for maximum conversion of sugars into ethanol. Saccharomyces cerevisiae strain (Saf-instant with cell concentration of 400 millions/mL at molasses sugar level of 13%–15% (pH 4.6±0.2, Temp. 32∘C±1, inoculum size of 25% (v/v, urea concentration, 150 ppm, DAP, 53.4 ppm and Lactrol,150 ppm supported maximum ethanol production (8.8% with YP/S=250 L ethanol per tone molasses (96.5% yield, and had significantly lower concentrations of byproducts. By selecting higher ethanol yielding yeast strain and optimizing the fermentation parameters both yield and economics of the fermentation process can be improved.

  10. Study of Saccharomyces cerevisiae wine strains for breeding through fermentation efficiency and tetrad analysis.

    Science.gov (United States)

    Fernández-González, Mónica; Úbeda, Juan F; Briones, Ana I

    2015-03-01

    One of the issues that most concerns to both winemakers and producers of active dry yeasts is the stuck and sluggish fermentations of grape musts with high levels of sugar, reflecting the inability of inoculated yeast strain to complete the fermentation process. It is difficult to obtain a wine strain that possesses both adequate oenological and technological properties; thus, the correct approach to solving these problems is the application of breeding programs primarily focused on both properties. The first step toward this process is to characterize the phenotypic diversity between potential parental strains. In the present study, we have analyzed the fermentative behavior of 26 Saccharomyces cerevisiae wine strains in high-sugar conditions at 20 °C, using a range of tests, such as sporulation ability, spore viability, and tetrad analysis to determine the tolerance of these yeasts to several stress conditions. Most tested strains were homothallic and heterozygous for more than one character. Two auxotrophic derivatives with defects in amino acid or nucleic acid metabolism were obtained, and these strains could potentially be used for the development of hybridization techniques without using laboratory strains. PMID:25447272

  11. Xylose and xylose/glucose co-fermentation by recombinant Saccharomyces cerevisiae strains expressing individual hexose transporters.

    Science.gov (United States)

    Gonçalves, Davi L; Matsushika, Akinori; de Sales, Belisa B; Goshima, Tetsuya; Bon, Elba P S; Stambuk, Boris U

    2014-09-01

    Since the uptake of xylose is believed to be one of the rate-limiting steps for xylose ethanol fermentation by recombinant Saccharomyces cerevisiae strains, we transformed a hxt-null strain lacking the major hexose transporters (hxt1Δ-hxt7Δ and gal2Δ) with an integrative plasmid to overexpress the genes for xylose reductase (XYL1), xylitol dehydrogenase (XYL2) and xylulokinase (XKS1), and analyzed the impact that overexpression of the HXT1, HXT2, HXT5 or HXT7 permeases have in anaerobic batch fermentations using xylose, glucose, or xylose plus glucose as carbon sources. Our results revealed that the low-affinity HXT1 permease allowed the maximal consumption of sugars and ethanol production rates during xylose/glucose co-fermentations, but was incapable to allow xylose uptake when this sugar was the only carbon source. The moderately high-affinity HXT5 permease was a poor glucose transporter, and it also did not allow significant xylose uptake by the cells. The moderately high-affinity HXT2 permease allowed xylose uptake with the same rates as those observed during glucose consumption, even under co-fermentation conditions, but had the drawback of producing incomplete fermentations. Finally, the high-affinity HXT7 permease allowed efficient xylose fermentation, but during xylose/glucose co-fermentations this permease showed a clear preference for glucose. Thus, our results indicate that approaches to engineer S. cerevisiae HXT transporters to improve second generation bioethanol production need to consider the composition of the biomass sugar syrup, whereby the HXT1 transporter seems more suitable for hydrolysates containing xylose/glucose blends, whereas the HXT7 permease would be a better choice for xylose-enriched sugar streams.

  12. Engineering the Saccharomyces cerevisiae β-oxidation pathway to increase medium chain fatty acid production as potential biofuel.

    Directory of Open Access Journals (Sweden)

    Liwei Chen

    Full Text Available Fatty acid-derived biofuels and biochemicals can be produced in microbes using β-oxidation pathway engineering. In this study, the β-oxidation pathway of Saccharomyces cerevisiae was engineered to accumulate a higher ratio of medium chain fatty acids (MCFAs when cells were grown on fatty acid-rich feedstock. For this purpose, the haploid deletion strain Δpox1 was obtained, in which the sole acyl-CoA oxidase encoded by POX1 was deleted. Next, the POX2 gene from Yarrowia lipolytica, which encodes an acyl-CoA oxidase with a preference for long chain acyl-CoAs, was expressed in the Δpox1 strain. The resulting Δpox1 [pox2+] strain exhibited a growth defect because the β-oxidation pathway was blocked in peroxisomes. To unblock the β-oxidation pathway, the gene CROT, which encodes carnitine O-octanoyltransferase, was expressed in the Δpox1 [pox2+] strain to transport the accumulated medium chain acyl-coAs out of the peroxisomes. The obtained Δpox1 [pox2+, crot+] strain grew at a normal rate. The effect of these genetic modifications on fatty acid accumulation and profile was investigated when the strains were grown on oleic acids-containing medium. It was determined that the engineered strains Δpox1 [pox2+] and Δpox1 [pox2+, crot+] had increased fatty acid accumulation and an increased ratio of MCFAs. Compared to the wild-type (WT strain, the total fatty acid production of the strains Δpox1 [pox2+] and Δpox1 [pox2+, crot+] were increased 29.5% and 15.6%, respectively. The intracellular level of MCFAs in Δpox1 [pox2+] and Δpox1 [pox2+, crot+] increased 2.26- and 1.87-fold compared to the WT strain, respectively. In addition, MCFAs in the culture medium increased 3.29-fold and 3.34-fold compared to the WT strain. These results suggested that fatty acids with an increased MCFAs ratio accumulate in the engineered strains with a modified β-oxidation pathway. Our approach exhibits great potential for transforming low value fatty acid

  13. New integrative computational approaches unveil the Saccharomyces cerevisiae pheno-metabolomic fermentative profile and allow strain selection for winemaking.

    Science.gov (United States)

    Franco-Duarte, Ricardo; Umek, Lan; Mendes, Inês; Castro, Cristiana C; Fonseca, Nuno; Martins, Rosa; Silva-Ferreira, António C; Sampaio, Paula; Pais, Célia; Schuller, Dorit

    2016-11-15

    During must fermentation by Saccharomyces cerevisiae strains thousands of volatile aroma compounds are formed. The objective of the present work was to adapt computational approaches to analyze pheno-metabolomic diversity of a S. cerevisiae strain collection with different origins. Phenotypic and genetic characterization together with individual must fermentations were performed, and metabolites relevant to aromatic profiles were determined. Experimental results were projected onto a common coordinates system, revealing 17 statistical-relevant multi-dimensional modules, combining sets of most-correlated features of noteworthy biological importance. The present method allowed, as a breakthrough, to combine genetic, phenotypic and metabolomic data, which has not been possible so far due to difficulties in comparing different types of data. Therefore, the proposed computational approach revealed as successful to shed light into the holistic characterization of S. cerevisiae pheno-metabolome in must fermentative conditions. This will allow the identification of combined relevant features with application in selection of good winemaking strains. PMID:27283661

  14. Paclitaxel-induced microtubule stabilization causes mitotic block and apoptotic-like cell death in a paclitaxel-sensitive strain of Saccharomyces cerevisiae

    OpenAIRE

    Foland, Travis B.; Dentler, William L.; SUPRENANT, KATHY A.; Gupta, Mohan L.; Himes, Richard H.

    2005-01-01

    Wild-type Saccharomyces cerevisiae tubulin does not bind the anti-mitotic microtubule stabilizing agent paclitaxel. Previously, we introduced mutations into the S. cerevisiae gene for β-tubulin that imparted paclitaxel binding to the protein, but the mutant strain was not sensitive to paclitaxel and other microtubule-stabilizing agents, due to the multiple ABC transporters in the membranes of budding yeast. Here, we introduced the mutated β-tubulin gene into a S. cerevisiae strain with dimini...

  15. Impact of different spray-drying conditions on the viability of wine Saccharomyces cerevisiae strains.

    Science.gov (United States)

    Aponte, Maria; Troianiello, Gabriele Danilo; Di Capua, Marika; Romano, Raffaele; Blaiotta, Giuseppe

    2016-01-01

    Spray-drying (SD) is widely considered a suitable method to preserve microorganisms, but data regarding yeasts are still scanty. In this study, the effect of growing media, process variables and carriers over viability of a wild wine Saccharomyces (S.) cerevisiae LM52 was evaluated. For biomass production, the strain was grown (batch and fed-batch fermentation) in a synthetic, as well as in a beet sugar molasses based-medium. Drying of cells resuspended in several combinations of soluble starch and maltose was performed at different inlet and outlet temperatures. Under the best conditions-suspension in soluble starch plus maltose couplet to inlet and outlet temperatures of 110 and 55 °C, respectively-the loss of viability of S. cerevisiae LM52 was 0.8 ± 0.1 and 0.5 ± 0.2 Log c.f.u. g(-1) for synthetic and molasses-based medium, respectively. Similar results were obtained when S. cerevisiae strains Zymoflore F15 and EC1118, isolated from commercial active dry yeast (ADY), were tested. Moreover, powders retained a high vitality and showed good fermentation performances up to 6 month of storage, at both 4 and -20 °C. Finally, fermentation performances of different kinds of dried formulates (SD and ADY) compared with fresh cultures did not show significant differences. The procedure proposed allowed a small-scale production of yeast in continuous operation with relatively simple equipment, and may thus represent a rapid response-on-demand for the production of autochthonous yeasts for local wine-making. PMID:26712628

  16. Fermentation of xylose to produce ethanol by recombinant Saccharomyces cerevisiae strain containing XYLA and XKS1

    Institute of Scientific and Technical Information of China (English)

    LIU Xiaolin; JIANG Ning; HE Peng; LU Dajun; SHEN An

    2005-01-01

    Fermentation of the pentose sugar xylose to produce ethanol using lignocellulosic biomass would make bioethanol production economically more competitive. Saccharomyce cerevisise, an efficient ethanol producer, cannot utilize xylose because it lacks the ability to convert xylose to its isomer xylulose. In this study, XYLA gene encoding xylose isomerase (XI) from Thermoanaerobacter tengcongensis MB4T and XKS1 gene encoding xylulokinase (XK) from Pichia stipitis were cloned and functionally coexpressed in Saccharomyces cerevisiae EF-326 to construct a recombinant xylose-utilizing strain. The resulting strain S. cerevisiae EF 1014 not only grew on xylose as sole carbon source, but also produced ethanol under anaerobic conditions. Fermentations performed with different xylose concentrations at different temperatures demonstrated that the highest ethanol productivity was 0.11 g/g xylose when xylose concentration was provided at 50 g/L. Under this condition, 28.4% of xylose was consumed and 1.54 g/L xylitol was formed. An increasing fermentation temperature from 30℃ to 37℃ did not improve ethanol yield.

  17. Construction of novel Saccharomyces cerevisiae strains for bioethanol active dry yeast (ADY production.

    Directory of Open Access Journals (Sweden)

    Daoqiong Zheng

    Full Text Available The application of active dry yeast (ADY in bioethanol production simplifies operation processes and reduces the risk of bacterial contamination. In the present study, we constructed a novel ADY strain with improved stress tolerance and ethanol fermentation performances under stressful conditions. The industrial Saccharomyces cerevisiae strain ZTW1 showed excellent properties and thus subjected to a modified whole-genome shuffling (WGS process to improve its ethanol titer, proliferation capability, and multiple stress tolerance for ADY production. The best-performing mutant, Z3-86, was obtained after three rounds of WGS, producing 4.4% more ethanol and retaining 2.15-fold higher viability than ZTW1 after drying. Proteomics and physiological analyses indicated that the altered expression patterns of genes involved in protein metabolism, plasma membrane composition, trehalose metabolism, and oxidative responses contribute to the trait improvement of Z3-86. This work not only successfully developed a novel S. cerevisiae mutant for application in commercial bioethanol production, but also enriched the current understanding of how WGS improves the complex traits of microbes.

  18. Gene engineering in yeast for biodegradation: Immunological cross-reactivity among cytochrome p-450 system proteins of saccharomyces cerevisiae and candida tropicalis

    Energy Technology Data Exchange (ETDEWEB)

    Loper, J.C.; Chen, C.; Dey, C.R.

    1993-01-01

    Yeasts are eukaryotic microorganisms whose cytochrome P-450 monooxygenase systems may be amenable to genetic engineering for the hydroxylation and detoxication of polychlorinated aromatic hydrocarbons. The molecular genetic properties of strains of bakers yeast, Saccharomyces cerevisiae, and an n-alkane utilizing yeast, Candida tropicalis ATCC750 are examined. Standard methods were used to purify cytochrome P-450 and NADPH-cytochrome c (P-450) reductase proteins from cells cultured by semi-anaerobic glucose fermentation (S. cerevisiae, C. tropicalis) and by growth on tetradecane (C. tropicalis). Polyvalent antisera prepared in rabbits to some of these proteins were used in tests of immunological relatedness among the purified proteins using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and nitrocellulose filter immunoblots. The results provide evidence for gene relationships which should prove useful in gene isolation and subsequent engineering of P-450 enzyme systems in yeast.

  19. The Flo11p-deficient Saccharomyces cerevisiae strain background S288c can adhere to plastic surfaces

    DEFF Research Database (Denmark)

    Mortensen, Henrik Dam; Dupont, Kitt; Jespersen, Lene;

    2007-01-01

    The effects of four types of plastic surfaces and four pre-incubation media, containing high/low glucose and +/- amino acids, on adhesion of Saccharomyces cerevisiae BY4742 wild type and Deltaflo11 mutant (strain background S288c) were investigated. No difference in adhesive ability between the t...... and amino acid starvation induces other genes than FLO11 in S. cerevisiae S288c coding for hydrophobic cell surface constituents with adhesive properties to especially moderately hydrophobic plastic surfaces.......The effects of four types of plastic surfaces and four pre-incubation media, containing high/low glucose and +/- amino acids, on adhesion of Saccharomyces cerevisiae BY4742 wild type and Deltaflo11 mutant (strain background S288c) were investigated. No difference in adhesive ability between the two...... yeast strains was observed in any of our experiments, thus confirming that FLO11 is not operational in the S. cerevisiae S288c strain background. The adhesive abilities of both yeast strains depended on the plastic type and pre-incubation conditions. The poorest adhesion was observed on hydrophilic...

  20. Control of surface wettability via strain engineering

    Science.gov (United States)

    Xiong, Wei; Liu, Jefferson Zhe; Zhang, Zhi-Liang; Zhen, Quan-Shui

    2013-08-01

    Reversible control of surface wettability has wide applications in lab-on-chip systems, tunable optical lenses, and microfluidic tools. Using a graphene sheet as a sample material and molecular dynamic simulations, we demonstrate that strain engineering can serve as an effective way to control the surface wettability. The contact angles θ of water droplets on a graphene vary from 72.5° to 106° under biaxial strains ranging from -10% to 10% that are applied on the graphene layer. For an intrinsic hydrophilic surface (at zero strain), the variation of θ upon the applied strains is more sensitive, i.e., from 0° to 74.8°. Overall the cosines of the contact angles exhibit a linear relation with respect to the strains. In light of the inherent dependence of the contact angle on liquid-solid interfacial energy, we develop an analytic model to show the cos θ as a linear function of the adsorption energy E ads of a single water molecule over the substrate surface. This model agrees with our molecular dynamic results very well. Together with the linear dependence of E ads on biaxial strains, we can thus understand the effect of strains on the surface wettability. Thanks to the ease of reversibly applying mechanical strains in micro/nano-electromechanical systems, we believe that strain engineering can be a promising means to achieve the reversibly control of surface wettability.

  1. Deletion of FPS1, Encoding Aquaglyceroporin Fps1p, Improves Xylose Fermentation by Engineered Saccharomyces cerevisiae

    OpenAIRE

    Wei, Na; Xu, Haiqing; Kim, Soo Rin; Jin, Yong-Su

    2013-01-01

    Accumulation of xylitol in xylose fermentation with engineered Saccharomyces cerevisiae presents a major problem that hampers economically feasible production of biofuels from cellulosic plant biomass. In particular, substantial production of xylitol due to unbalanced redox cofactor usage by xylose reductase (XR) and xylitol dehydrogenase (XDH) leads to low yields of ethanol. While previous research focused on manipulating intracellular enzymatic reactions to improve xylose metabolism, this s...

  2. Production of fructanase by a wild strain of Saccharomyces cerevisiae on tequila agave fructan.

    Science.gov (United States)

    Corona-González, R I; Pelayo-Ortiz, C; Jacques, G; Guatemala, G; Arriola, E; Arias, J A; Toriz, G

    2015-01-01

    A new wild strain of Saccharomyces cerevisiae (CF3) isolated from tequila must was evaluated for production of fructanase on Agave tequilana Weber fructan (FT). Fructanase activity (F) was assessed by a 3(3) factorial design (substrate, temperature and pH). High enzymatic activity (31.1 U/ml) was found at 30 °C, pH 5, using FT (10 g/l) as substrate. The effect of initial substrate concentration on F (FT0, 5.7-66 g/l) was studied and it was found that F was highest (44.8 U/ml) at FT0 25 g/l. A 2(2) factorial experimental design with five central points was utilized to study the effect of stirring and aeration on fructanase activity; stirring exhibited a stronger effect on F. The ratio fructanase to invertase (F/S) was 0.57, which confirms that the enzymes are fructanase. Crude fructanase reached high substrate hydrolysis (48 wt%) in 10 h. It is shown that S. cerevisiae CF3 was able to produce large amounts of fructanase by growing it on fructan from A. tequilana.

  3. Production of fructanase by a wild strain of Saccharomyces cerevisiae on tequila agave fructan.

    Science.gov (United States)

    Corona-González, R I; Pelayo-Ortiz, C; Jacques, G; Guatemala, G; Arriola, E; Arias, J A; Toriz, G

    2015-01-01

    A new wild strain of Saccharomyces cerevisiae (CF3) isolated from tequila must was evaluated for production of fructanase on Agave tequilana Weber fructan (FT). Fructanase activity (F) was assessed by a 3(3) factorial design (substrate, temperature and pH). High enzymatic activity (31.1 U/ml) was found at 30 °C, pH 5, using FT (10 g/l) as substrate. The effect of initial substrate concentration on F (FT0, 5.7-66 g/l) was studied and it was found that F was highest (44.8 U/ml) at FT0 25 g/l. A 2(2) factorial experimental design with five central points was utilized to study the effect of stirring and aeration on fructanase activity; stirring exhibited a stronger effect on F. The ratio fructanase to invertase (F/S) was 0.57, which confirms that the enzymes are fructanase. Crude fructanase reached high substrate hydrolysis (48 wt%) in 10 h. It is shown that S. cerevisiae CF3 was able to produce large amounts of fructanase by growing it on fructan from A. tequilana. PMID:25432071

  4. BioREFINE-2G project – Engineering of industrial yeast strains for production of dicarboxylic acids from side and waste streams

    DEFF Research Database (Denmark)

    Stovicek, Vratislav; Chen, Xiao; Borodina, Irina;

    2014-01-01

    compounds can be polymerised to biodegradable polymersthat can find application as plastics, coatings or adhesives. To reach the goals, the identification of relevant metabolic routes, strain engineering and the development of a toolbox for manipulation of industrial S. cerevisiae strains are required. Here......, we present advanced genetic engineering tools applicable for generally hardly amenable strains with industrial background. This involves tools forstable heterologous gene (over-)expression and a strategy for fast performance of gene disruption inmultiple ploidy strains. The use of the developed...... toolbox in metabolic engineering of various industrial yeast strains will be demonstrated....

  5. IMPROVEMENT OF BORASSUS AKEASSII WINES QUALITY BY CONTROLLED FERMENTATION USING SACCHAROMYCES CEREVISIAE STRAINS

    Directory of Open Access Journals (Sweden)

    TAPSOBA François

    2016-06-01

    Full Text Available Palm wine produced traditionally and consumed by many people around the world and specifically in Burkina Faso posed health risks because of questionable quality of wine produced by mix culture fermentation and the use of antiseptics for the stabilization. In order to improve its quality, Saccharomyces cerevisiae strains isolated from Borassus akeassii wines and identified by amplification and RFLP analysis of the 5-8S-ITS region were used for in vitro fermentation of unfermented palm sap. The physicochemical characteristics of the sap were measured before and after fermentation process by High-Performance Liquid Chromatography (HPLC and the microbiological quality were also performed. HPLC analysis showed that glucose and fructose concentration in palm sap were 37.0 and 27.6 g/L respectively, ethanol content was ranged between 2.76 and 5.31 % (g/mL for controlled fermentation and 2.20 % (g/mL for spontaneous fermentation. Lactic and acetic acids were ranged between 0.1 and 0.3 g/L and 1.5 and 1.6 g/L for controlled fermentation versus 2.5 and 3.1 g/L and the spontaneous fermentation respectively. Coliforms and Staphylococcus aureus were detected only in the unfermented palm sap and the wine fermented spontaneously. Principal component analysis showed a good separation between spontaneous and controlled fermentation. Sterilization and controlled fermentation of the unfermented sap with palm wine Saccharomyces cerevisiae strains led to the improvement of palm wine quality.

  6. Genome sequencing and comparative analysis of Saccharomyces cerevisiae strain YJM789.

    Science.gov (United States)

    Wei, Wu; McCusker, John H; Hyman, Richard W; Jones, Ted; Ning, Ye; Cao, Zhiwei; Gu, Zhenglong; Bruno, Dan; Miranda, Molly; Nguyen, Michelle; Wilhelmy, Julie; Komp, Caridad; Tamse, Raquel; Wang, Xiaojing; Jia, Peilin; Luedi, Philippe; Oefner, Peter J; David, Lior; Dietrich, Fred S; Li, Yixue; Davis, Ronald W; Steinmetz, Lars M

    2007-07-31

    We sequenced the genome of Saccharomyces cerevisiae strain YJM789, which was derived from a yeast isolated from the lung of an AIDS patient with pneumonia. The strain is used for studies of fungal infections and quantitative genetics because of its extensive phenotypic differences to the laboratory reference strain, including growth at high temperature and deadly virulence in mouse models. Here we show that the approximately 12-Mb genome of YJM789 contains approximately 60,000 SNPs and approximately 6,000 indels with respect to the reference S288c genome, leading to protein polymorphisms with a few known cases of phenotypic changes. Several ORFs are found to be unique to YJM789, some of which might have been acquired through horizontal transfer. Localized regions of high polymorphism density are scattered over the genome, in some cases spanning multiple ORFs and in others concentrated within single genes. The sequence of YJM789 contains clues to pathogenicity and spurs the development of more powerful approaches to dissecting the genetic basis of complex hereditary traits.

  7. Biodiversity of autolytic ability in flocculent Saccharomyces cerevisiae strains suitable for traditional sparkling wine fermentation.

    Science.gov (United States)

    Perpetuini, Giorgia; Di Gianvito, Paola; Arfelli, Giuseppe; Schirone, Maria; Corsetti, Aldo; Tofalo, Rosanna; Suzzi, Giovanna

    2016-07-01

    Yeasts involved in secondary fermentation of traditional sparkling wines should show specific characteristics, such as flocculation capacity and autolysis. Recently it has been postulated that autophagy may contribute to the outcome of autolysis. In this study, 28 flocculent wine Saccahromyces cerevisiae strains characterized by different flocculation degrees were studied for their autolytic and autophagic activities. Autolysis was monitored in synthetic medium through the determination of amino acid nitrogen and total proteins released. At the same time, novel primer sets were developed to determine the expression of the genes ATG1, ATG17 and ATG29. Twelve strains were selected on the basis of their autolytic rate and ATG gene expressions in synthetic medium and were inoculated in a base wine. After 30, 60 and 180 days the autolytic process and ATG gene expressions were evaluated. The obtained data showed that autolysis and ATG gene expressions differed among strains and were independent of the degree of flocculation. This biodiversity could be exploited to select new starter stains to improve sparkling wine production. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26804203

  8. Expression variability of co-regulated genes differentiates Saccharomyces cerevisiae strains

    Directory of Open Access Journals (Sweden)

    Schuller Dorit

    2011-04-01

    Full Text Available Abstract Background Saccharomyces cerevisiae (Baker's yeast is found in diverse ecological niches and is characterized by high adaptive potential under challenging environments. In spite of recent advances on the study of yeast genome diversity, little is known about the underlying gene expression plasticity. In order to shed new light onto this biological question, we have compared transcriptome profiles of five environmental isolates, clinical and laboratorial strains at different time points of fermentation in synthetic must medium, during exponential and stationary growth phases. Results Our data unveiled diversity in both intensity and timing of gene expression. Genes involved in glucose metabolism and in the stress response elicited during fermentation were among the most variable. This gene expression diversity increased at the onset of stationary phase (diauxic shift. Environmental isolates showed lower average transcript abundance of genes involved in the stress response, assimilation of nitrogen and vitamins, and sulphur metabolism, than other strains. Nitrogen metabolism genes showed significant variation in expression among the environmental isolates. Conclusions Wild type yeast strains respond differentially to the stress imposed by nutrient depletion, ethanol accumulation and cell density increase, during fermentation of glucose in synthetic must medium. Our results support previous data showing that gene expression variability is a source of phenotypic diversity among closely related organisms.

  9. A Saccharomyces cerevisiae Wine Strain Inhibits Growth and Decreases Ochratoxin A Biosynthesis by Aspergillus carbonarius and Aspergillus ochraceus

    Directory of Open Access Journals (Sweden)

    Marilena Budroni

    2012-12-01

    Full Text Available The aim of this study was to select wine yeast strains as biocontrol agents against fungal contaminants responsible for the accumulation of ochratoxin A (OTA in grape and wine and to dissect the mechanism of OTA detoxification by a Saccharomyces cerevisiae strain (DISAABA1182, which had previously been reported to reduce OTA in a synthetic must. All of the yeast strains tested displayed an ability to inhibit the growth of Aspergillus carbonarius both in vivo and in vitro and addition of culture filtrates from the tested isolates led to complete inhibition of OTA production. S. cerevisiae DISAABA1182 was selected and further tested for its capacity to inhibit OTA production and pks (polyketide synthase transcription in A. carbonarius and Aspergillus ochraceus in vitro. In order to dissect the mechanism of OTA detoxification, each of these two fungi was co-cultured with living yeast cells exposed to yeast crude or to autoclaved supernatant: S. cerevisiae DISAABA1182 was found to inhibit mycelial growth and OTA production in both Aspergilli when co-cultured in the OTA-inducing YES medium. Moreover, a decrease in pks transcription was observed in the presence of living cells of S. cerevisiae DISAABA1182 or its supernatant, while no effects were observed on transcription of either of the constitutively expressed calmodulin and β-tubulin genes. This suggests that transcriptional regulation of OTA biosynthetic genes takes place during the interaction between DISAABA1182 and OTA-producing Aspergilli.

  10. Xylose fermentation efficiency and inhibitor tolerance of the recombinant industrial Saccharomyces cerevisiae strain NAPX37.

    Science.gov (United States)

    Li, Yun-Cheng; Mitsumasu, Kanako; Gou, Zi-Xi; Gou, Min; Tang, Yue-Qin; Li, Guo-Ying; Wu, Xiao-Lei; Akamatsu, Takashi; Taguchi, Hisataka; Kida, Kenji

    2016-02-01

    Industrial yeast strains with good xylose fermentation ability and inhibitor tolerance are important for economical lignocellulosic bioethanol production. The flocculating industrial Saccharomyces cerevisiae strain NAPX37, harboring the xylose reductase-xylitol dehydrogenase (XR-XDH)-based xylose metabolic pathway, displayed efficient xylose fermentation during batch and continuous fermentation. During batch fermentation, the xylose consumption rates at the first 36 h were similar (1.37 g/L/h) when the initial xylose concentrations were 50 and 75 g/L, indicating that xylose fermentation was not inhibited even when the xylose concentration was as high as 75 g/L. The presence of glucose, at concentrations of up to 25 g/L, did not affect xylose consumption rate at the first 36 h. Strain NAPX37 showed stable xylose fermentation capacity during continuous ethanol fermentation using xylose as the sole sugar, for almost 1 year. Fermentation remained stable at a dilution rate of 0.05/h, even though the xylose concentration in the feed was as high as 100 g/L. Aeration rate, xylose concentration, and MgSO4 concentration were found to affect xylose consumption and ethanol yield. When the xylose concentration in the feed was 75 g/L, a high xylose consumption rate of 6.62 g/L/h and an ethanol yield of 0.394 were achieved under an aeration rate of 0.1 vvm, dilution rate of 0.1/h, and 5 mM MgSO4. In addition, strain NAPX37 exhibited good tolerance to inhibitors such as weak acids, furans, and phenolics during xylose fermentation. These findings indicate that strain NAPX37 is a promising candidate for application in the industrial production of lignocellulosic bioethanol. PMID:26603762

  11. Adjustment of Trehalose Metabolism in Wine Saccharomyces cerevisiae Strains To Modify Ethanol Yields

    Science.gov (United States)

    Rossouw, D.; Heyns, E. H.; Setati, M. E.; Bosch, S.

    2013-01-01

    The ability of Saccharomyces cerevisiae to efficiently produce high levels of ethanol through glycolysis has been the focus of much scientific and industrial activity. Despite the accumulated knowledge regarding glycolysis, the modification of flux through this pathway to modify ethanol yields has proved difficult. Here, we report on the systematic screening of 66 strains with deletion mutations of genes encoding enzymes involved in central carbohydrate metabolism for altered ethanol yields. Five of these strains showing the most prominent changes in carbon flux were selected for further investigation. The genes were representative of trehalose biosynthesis (TPS1, encoding trehalose-6-phosphate synthase), central glycolysis (TDH3, encoding glyceraldehyde-3-phosphate dehydrogenase), the oxidative pentose phosphate pathway (ZWF1, encoding glucose-6-phosphate dehydrogenase), and the tricarboxylic acid (TCA) cycle (ACO1 and ACO2, encoding aconitase isoforms 1 and 2). Two strains exhibited lower ethanol yields than the wild type (tps1Δ and tdh3Δ), while the remaining three showed higher ethanol yields. To validate these findings in an industrial yeast strain, the TPS1 gene was selected as a good candidate for genetic modification to alter flux to ethanol during alcoholic fermentation in wine. Using low-strength promoters active at different stages of fermentation, the expression of the TPS1 gene was slightly upregulated, resulting in a decrease in ethanol production and an increase in trehalose biosynthesis during fermentation. Thus, the mutant screening approach was successful in terms of identifying target genes for genetic modification in commercial yeast strains with the aim of producing lower-ethanol wines. PMID:23793638

  12. High ethanol fermentation performance of the dry dilute acid pretreated corn stover by an evolutionarily adapted Saccharomyces cerevisiae strain.

    Science.gov (United States)

    Qureshi, Abdul Sattar; Zhang, Jian; Bao, Jie

    2015-01-01

    Ethanol fermentation was investigated at the high solids content of the dry dilute sulfuric acid pretreated corn stover feedstock using an evolutionary adapted Saccharomyces cerevisiae DQ1 strain. The evolutionary adaptation was conducted by successively transferring the S. cerevisiae DQ1 cells into the inhibitors containing corn stover hydrolysate every 12h and finally a stable yeast strain was obtained after 65 days' continuous adaptation. The ethanol fermentation performance using the adapted strain was significantly improved with the high ethanol titer of 71.40 g/L and the high yield of 80.34% in the simultaneous saccharification and fermentation (SSF) at 30% solids content. No wastewater was generated from pretreatment to fermentation steps. The results were compared with the published cellulosic ethanol fermentation cases, and the obvious advantages of the present work were demonstrated not only at the high ethanol titer and yield, but also the significant reduction of wastewater generation and potential cost reduction.

  13. Transcriptomics in human blood incubation reveals the importance of oxidative stress response in Saccharomyces cerevisiae clinical strains

    Directory of Open Access Journals (Sweden)

    Llopis Silvia

    2012-08-01

    Full Text Available Abstract Background In recent years an increasing number of yeast infections in humans have been related to certain clinical isolates of Saccharomyces cerevisiae. Some clinical strains showed in vivo and in vitro virulence traits and were able to cause death in mice whereas other clinical strains were avirulent. Results In this work, we studied the transcriptional profiles of two S. cerevisiae clinical strains showing virulent traits and two control non-virulent strains during a blood incubation model and detected a specific transcriptional response of clinical strains. This response involves an mRNA levels increase of amino acid biosynthesis genes and especially oxidative stress related genes. We observed that the clinical strains were more resistant to reactive oxygen species in vitro. In addition, blood survival of clinical isolates was high, reaching similar levels to pathogenic Candida albicans strain. Furthermore, a virulent strain mutant in the transcription factor Yap1p, unable to grow in oxidative stress conditions, presented decreased survival levels in human blood compared with the wild type or YAP1 reconstituted strain. Conclusions Our data suggest that this enhanced oxidative stress response in virulent clinical isolates, presumably induced in response to oxidative burst from host defense cells, is important to increase survival in human blood and can help to infect and even produce death in mice models.

  14. Engineering of chromosomal wax ester synthase integrated Saccharomyces cerevisiae mutants for improved biosynthesis of fatty acid ethyl esters.

    Science.gov (United States)

    Shi, Shuobo; Valle-Rodríguez, Juan Octavio; Siewers, Verena; Nielsen, Jens

    2014-09-01

    In recent years, significant advances have been made to engineer robust microbes for overproducing biochemical products from renewable resources. These accomplishments have to a large extend been based on plasmid based methods. However, plasmid maintenance may cause a metabolic burden on the host cell and plasmid-based overexpression of genes can result in genetically unstable strains, which contributes to loss in productivity. Here, a chromosome engineering method based on delta integration was applied in Saccharomyces cerevisiae for the production of fatty acid ethyl esters (FAEEs), which can be directly used as biodiesel and would be a possible substitute for conventional petroleum-based diesel. An integration construct was designed and integrated into chromosomal delta sequences by repetitive transformation, which resulted in 1-6 copies of the integration construct per genome. The corresponding FAEE production increased up to 34 mg/L, which is an about sixfold increase compared to the equivalent plasmid-based producer. The integrated cassette in the yeast genome was stably maintained in nonselective medium after deletion of RAD52 which is essential for efficient homologous recombination. To obtain a further increase of FAEE production, genes encoding endogenous acyl-CoA binding protein (ACB1) and a bacterial NADP(+)-dependent glyceraldehyde-3-phosphate dehydrogenase (gapN) were overexpressed in the final integration strain, which resulted in another 40% percent increase in FAEE production. Our integration strategy enables easy engineering of strains with adjustable gene copy numbers integrated into the genome and this allows for an easy evaluation of the effect of the gene copy number on pathway flux. It therefore represents a valuable tool for introducing and expressing a heterologous pathway in yeast. PMID:24752598

  15. Saccharomyces cerevisiae BY4741 and W303-1A laboratory strains differ in salt tolerance.

    Science.gov (United States)

    Petrezselyova, Silvia; Zahradka, Jaromir; Sychrova, Hana

    2010-01-01

    Saccharomyces cerevisiae yeast cells serve as a model to elucidate the bases of salt tolerance and potassium homeostasis regulation in eukaryotic cells. In this study, we show that two widely used laboratory strains, BY4741 and W303-1A, differ not only in cell size and volume but also in their relative plasma-membrane potential (estimated with a potentiometric fluorescent dye diS-C3(3) and as Hygromycin B sensitivity) and tolerance to alkali-metal cations. W303-1A cells and their mutant derivatives lacking either uptake (trk1 trk2) or efflux (nha1) systems for alkali-metal cations are more tolerant to toxic sodium and lithium cations but also more sensitive to higher external concentrations of potassium than BY4741 cells and their mutants. Moreover, our results suggest that though the two strains do not differ in the total potassium content, the regulation of intracellular potassium homeostasis is probably not the same in BY4741 and W303-1A cells.

  16. CRISPR–Cas system enables fast and simple genome editing of industrial Saccharomyces cerevisiae strains

    DEFF Research Database (Denmark)

    Stovicek, Vratislav; Borodina, Irina; Förster, Jochen

    2015-01-01

    , their genetic manipulation is challenging, as they are usually diploid or polyploid. Therefore, there is a need to develop more efficient genetic engineering tools. We applied a CRISPR–Cas9 system for genome editing of different industrial strains, and show simultaneous disruption of two alleles of a gene...

  17. Ethanol from lignocellulose - Fermentation inhibitors, detoxification and genetic engineering of Saccharomyces cerevisiae for enhanced resistance

    Energy Technology Data Exchange (ETDEWEB)

    Larsson, Simona

    2000-07-01

    Ethanol can be produced from lignocellulose by first hydrolysing the material to sugars, and then fermenting the hydrolysate with the yeast Saccharomyces cerevisiae. Hydrolysis using dilute sulphuric acid has advantages over other methods, however, compounds which inhibit fermentation are generated during this kind of hydrolysis. The inhibitory effect of aliphatic acids, furans, and phenolic compounds was investigated. The generation of inhibitors during hydrolysis was studied using Norway spruce as raw material. It was concluded that the decrease in the fermentability coincided with increasing harshness of the hydrolysis conditions. The decrease in fermentability was not correlated solely to the content of aliphatic acids or furan derivatives. To increase the fermentability, detoxification is often employed. Twelve detoxification methods were compared with respect to the chemical composition of the hydrolysate and the fermentability after treatment. The most efficient detoxification methods were anion-exchange at pH 10.0, overliming and enzymatic detoxification with the phenol-oxidase laccase. Detailed analyses of ion exchange revealed that anion exchange and unspecific hydrophobic interactions greatly contributed to the detoxification effect, while cation exchange did not. The comparison of detoxification methods also showed that phenolic compounds are very important fermentation inhibitors, as their selective removal with laccase had a major positive effect on the fermentability. Selected compounds; aliphatic acids, furans and phenolic compounds, were characterised with respect to their inhibitory effect on ethanolic fermentation by S. cerevisiae. When aliphatic acids or furans were compared, the inhibitory effects were found to be in the same range, but the phenolic compounds displayed widely different inhibitory effects. The possibility of genetically engineering S. cerevisiae to achieve increased inhibitor resistance was explored by heterologous expression of

  18. De novo production of the flavonoid naringenin in engineered Saccharomyces cerevisiae

    Science.gov (United States)

    2012-01-01

    Background Flavonoids comprise a large family of secondary plant metabolic intermediates that exhibit a wide variety of antioxidant and human health-related properties. Plant production of flavonoids is limited by the low productivity and the complexity of the recovered flavonoids. Thus to overcome these limitations, metabolic engineering of specific pathway in microbial systems have been envisaged to produce high quantity of a single molecules. Result Saccharomyces cerevisiae was engineered to produce the key intermediate flavonoid, naringenin, solely from glucose. For this, specific naringenin biosynthesis genes from Arabidopsis thaliana were selected by comparative expression profiling and introduced in S. cerevisiae. The sole expression of these A. thaliana genes yielded low extracellular naringenin concentrations (Synthesis of aromatic amino acids was deregulated by alleviating feedback inhibition of 3-deoxy-d-arabinose-heptulosonate-7-phosphate synthase (Aro3, Aro4) and byproduct formation was reduced by eliminating phenylpyruvate decarboxylase (Aro10, Pdc5, Pdc6). Together with an increased copy number of the chalcone synthase gene and expression of a heterologous tyrosine ammonia lyase, these modifications resulted in a 40-fold increase of extracellular naringenin titers (to approximately 200 μM) in glucose-grown shake-flask cultures. In aerated, pH controlled batch reactors, extracellular naringenin concentrations of over 400 μM were reached. Conclusion The results reported in this study demonstrate that S. cerevisiae is capable of de novo production of naringenin by coexpressing the naringenin production genes from A. thaliana and optimization of the flux towards the naringenin pathway. The engineered yeast naringenin production host provides a metabolic chassis for production of a wide range of flavonoids and exploration of their biological functions. PMID:23216753

  19. Model-guided identification of gene deletion targets for metabolic engineering in Saccharomyces cerevisiae.

    Science.gov (United States)

    Brochado, Ana Rita; Patil, Kiran Raosaheb

    2014-01-01

    Identification of metabolic engineering strategies for rerouting intracellular fluxes towards a desired product is often a challenging task owing to the topological and regulatory complexity of metabolic networks. Genome-scale metabolic models help tackling this complexity through systematic consideration of mass balance and reaction directionality constraints over the entire network. Here, we describe how genome-scale metabolic models can be used for identifying gene deletion targets leading to increased production of the desired product. Vanillin production in Saccharomyces cerevisiae is used as a case study throughout this chapter. PMID:24744040

  20. Creation of an ethanol-tolerant Saccharomyces cerevisiae strain by 266 nm laser radiation and repetitive cultivation.

    Science.gov (United States)

    Zhang, Min; Zhu, Rongrong; Zhang, Minfeng; Wang, Shilong

    2014-11-01

    Laser radiation is an efficient approach for rapid improvement of industrial microbial phenotypes. To improve ethanol tolerance in Saccharomyces cerevisiae strains, a 266 nm laser radiation with the use of repetitive cultivation was explored in this work. After irradiated by 266 nm laser radiation and repetitive cultivation, a genetically stable SM4 strain was obtained. The SM4 strain could grow on YPD plate with extra 15% (v/v) ethanol. Moreover, the ethanol production performance of SM4 strain was 29.25% more than that of the wild type strain when they were cultivated in 5% (v/v) ethanol fermentation medium for 72 h. The DNA mutation was the possible characters for the phenotype of SM4 strain. Overall, the 266 nm laser radiation and repetitive cultivation approach might be a novel and useful for breeding fermentation microorganisms.

  1. Diversity of Saccharomyces cerevisiae strains isolated from Borassus akeassii palm wines from Burkina Faso in comparison to other African beverages.

    Science.gov (United States)

    Tapsoba, François; Legras, Jean-Luc; Savadogo, Aly; Dequin, Sylvie; Traore, Alfred Sababenedyo

    2015-10-15

    In South-West of Burkina Faso, palm wine is produced by spontaneous fermentation of the sap from a specific palm tree Borassus akeassii and plays an important role in people's lives. Saccharomyces cerevisiae is the main agent of this alcoholic fermentation but little is known about the diversity of the isolates from palm. In this work, 39 Saccharomyces cerevisiae strains were isolated from palm wine samples collected from 14 sites in Burkina Faso, as well as 7 isolates obtained from sorghum beer (Dolo) from 3 distant sites. Their diversity was analyzed at 12 microsatellite loci, and compared to the genotypes obtained for other African yeast populations isolated from Cocoa hulks from Ghana, sorghum beer from Ivory Coast, palm wine from Djibouti Republic, and to our database of strains from miscellaneous origins (bread, beer, wine, sake, oaks…). The ploidy of these strains has been assessed as well by flow cytometry. Our results show that B. akeassii palm wine contains a specific yeast population of diploid strains, different from Dolo produced in the same area and from other palm wine strains from Ivory Coast, Nigeria, or Djibouti Republic. In contrast, Dolo strains appeared as a group of related and mainly tetraploid strains despite being isolated from different countries. PMID:26202324

  2. Isolation and characterization of Saccharomyces cerevisiae strains of winery interest Isolamento e caracterização de cepas de Saccharomyces cerevisiae de interesse em produção de vinho

    Directory of Open Access Journals (Sweden)

    Thais M. Guimarães

    2006-03-01

    Full Text Available Despite the availability of several Saccharomyces cerevisiae commercial strains intended for wine production, strains isolated from winery regions are usually more adapted to their own climatic conditions, grapes and also partially responsible for particular characteristics that frequently identify specific wines and regions. Thus the microbiota of an important winery region (Colombo was studied in order to isolate and characterize S. cerevisiae strains that could be used on wine production. From 61 yeasts isolated, 14 were identified as S. cerevisiae. Some of them showed fermentative characteristics even better than commercial strains indicating that they could be applied on wine production in order to increase the quality and assure the particular wine characteristics of that region.

  3. Systems biology approaches for the design of novel Saccharomyces cerevisiae winemaking strains for enhanced flavour compounds synthesis

    OpenAIRE

    Mendes, Inês Isabel Moreira Moutinho Vieira

    2015-01-01

    Tese de Doutoramento em Biologia Ambiental e Molecular Wine flavour and aroma are the result of yeast metabolism and must compounds interactions. During must fermentation thousands of volatile aroma compounds are formed, with higher alcohols, acetate esters and ethyl esters being the main aromatic compounds contributing to a floral and fruity aroma. The action of yeast, in particular of Saccharomyces cerevisiae strains, on the must components will build the architecture of t...

  4. New promoters for strain engineering of Penicillium chrysogenum.

    Science.gov (United States)

    Polli, Fabiola; Meijrink, Ben; Bovenberg, Roel A L; Driessen, Arnold J M

    2016-04-01

    Filamentous fungi such as Aspergillus and Penicillium are widely used as hosts for the industrial products such as proteins and secondary metabolites. Although filamentous fungi are versatile in recognizing transcriptional and translational elements present in genes from other filamentous fungal species, only few promoters have been applied and compared in performance so far in Penicillium chrysogenum. Therefore, a set of homologous and heterologous promoters were tested in a reporter system to obtain a set of potential different strengths. Through in vivo homologous recombination in Saccharomyces cerevisiae, twelve Aspergillus niger and P. chrysogenum promoter-reporter pathways were constructed that drive the expression of green fluorescent protein while concurrent expression of the red fluorescent protein was used as an internal standard and placed under control of the PcPAF promoter. The pathways were integrated into the genome of P. chrysogenum and tested using the BioLector system for fermentation. Reporter gene expression was monitored during growth and classified according to promoter strength and expression profile. A set of novel promoters was obtained that can be used to tune the expression of target genes in future strain engineering programs. PMID:26701309

  5. Cell surface engineering of Saccharomyces cerevisiae combined with membrane separation technology for xylitol production from rice straw hydrolysate.

    Science.gov (United States)

    Guirimand, Gregory; Sasaki, Kengo; Inokuma, Kentaro; Bamba, Takahiro; Hasunuma, Tomohisa; Kondo, Akihiko

    2016-04-01

    Xylitol, a value-added polyol deriving from D-xylose, is widely used in both the food and pharmaceutical industries. Despite extensive studies aiming to streamline the production of xylitol, the manufacturing cost of this product remains high while demand is constantly growing worldwide. Biotechnological production of xylitol from lignocellulosic waste may constitute an advantageous and sustainable option to address this issue. However, to date, there have been few reports of biomass conversion to xylitol. In the present study, xylitol was directly produced from rice straw hydrolysate using a recombinant Saccharomyces cerevisiae YPH499 strain expressing cytosolic xylose reductase (XR), along with β-glucosidase (BGL), xylosidase (XYL), and xylanase (XYN) enzymes (co-)displayed on the cell surface; xylitol production by this strain did not require addition of any commercial enzymes. All of these enzymes contributed to the consolidated bioprocessing (CBP) of the lignocellulosic hydrolysate to xylitol to produce 5.8 g/L xylitol with 79.5 % of theoretical yield from xylose contained in the biomass. Furthermore, nanofiltration of the rice straw hydrolysate provided removal of fermentation inhibitors while simultaneously increasing sugar concentrations, facilitating high concentration xylitol production (37.9 g/L) in the CBP. This study is the first report (to our knowledge) of the combination of cell surface engineering approach and membrane separation technology for xylitol production, which could be extended to further industrial applications. PMID:26631184

  6. Increasing galactose consumption by Saccharomyces cerevisiae through metabolic engineering of the GAL gene regulatory network

    DEFF Research Database (Denmark)

    Østergaard, Simon; Olsson, Lisbeth; Johnston, M.;

    2000-01-01

    by eliminating three known negative regulators of the GAL system: Gale, Gal80, and Mig1. This led to a 41% increase in flux through the galactose utilization pathway compared with the wild-type strain. This is of significant interest within the field of biotechnology since galactose is present in many industrial...... in the pathway, and ultimately, increasing metabolic flux through the pathway of interest, By manipulating the GAL gene regulatory network of Saccharomyces cerevisiae, which is a tightly regulated system, we produced prototroph mutant strains, which increased the flux through the galactose utilization pathway...... media. The improved galactose consumption of the gal mutants did not favor biomass formation, but rather caused excessive respiro-fermentative metabolism, with the ethanol production rate increasing linearly with glycolytic flux....

  7. Metabolic engineering of strains: from industrial-scale to lab-scale chemical production.

    Science.gov (United States)

    Sun, Jie; Alper, Hal S

    2015-03-01

    A plethora of successful metabolic engineering case studies have been published over the past several decades. Here, we highlight a collection of microbially produced chemicals using a historical framework, starting with titers ranging from industrial scale (more than 50 g/L), to medium-scale (5-50 g/L), and lab-scale (0-5 g/L). Although engineered Escherichia coli and Saccharomyces cerevisiae emerge as prominent hosts in the literature as a result of well-developed genetic engineering tools, several novel native-producing strains are gaining attention. This review catalogs the current progress of metabolic engineering towards production of compounds such as acids, alcohols, amino acids, natural organic compounds, and others.

  8. Physicochemical characterization of pomegranate wines fermented with three different Saccharomyces cerevisiae yeast strains.

    Science.gov (United States)

    Berenguer, María; Vegara, Salud; Barrajón, Enrique; Saura, Domingo; Valero, Manuel; Martí, Nuria

    2016-01-01

    Three commercial Saccharomyces cerevisiae yeast strains: Viniferm Revelación, Viniferm SV and Viniferm PDM were evaluated for the production of pomegranate wine from a juice coupage of the two well-known varieties Mollar and Wonderfull. Further malolactic fermentation was carried out spontaneously. The same fermentation patterns were observed for pH, titratable acidity, density, sugar consumption, and ethanol and glycerol production. Glucose was exhausted while fructose residues remained at the end of alcoholic fermentation. A high ethanol concentration (10.91 ± 0.27% v/v) in combination with 1.49 g/L glycerol was achieved. Citric acid concentration increased rapidly a 31.7%, malic acid disappeared as result of malolactic fermentation and the lactic acid levels reached values between 0.40 and 0.96 g/L. The analysis of CIEa parameter and total anthocyanin content highlights a lower degradation of monomeric anthocyanins during winemaking with Viniferm PDM yeast. The resulting wine retains a 34.5% of total anthocyanin content of pomegranate juice blend.

  9. Heterologous Expression of Amylase Gene from Saccharomycopsis fibuligera in an Industrial Strain of Saccharomyces cerevisiae

    Institute of Scientific and Technical Information of China (English)

    LIU Zeng-ran; ZHANG Guang-yi; LONG Zhang-fu; LIU Shi-gui

    2005-01-01

    An α-amylase encoding gene was amplified by polymerase chain reaction from Saccharomycopsis fibuligera and inserted into a shuttle vector YEp352,together with the yeast phosphoglycerate kinase 1 promoter and α-factor signal gene. The recombinant expression plasmid pLA8α was transformed into an industrial strain of Saccharomyces cerevisiae Sc-11. The activity of the α-amylase produced by the transformant Sc-11-pLA8α was 6.3 U/mL and the starch utilization rate in YPS medium was 42 %. The purified amylase was analyzed by SDS-PAGE,showing a molecular weight of 55×103 protein band. Furthermore, the residual sugar, ethanol and some volatile compounds in the fermented worts under simulating brewing conditions were determined by chromatographic analyses. The fermentation characteristics of Sc-11-pLA8α were similar to that of Sc-11 and only minor changes in the concentration of flavor compounds could be observed.

  10. De novo sequencing, assembly and analysis of the genome of the laboratory strain Saccharomyces cerevisiae CEN.PK113-7D, a model for modern industrial biotechnology

    Directory of Open Access Journals (Sweden)

    Nijkamp Jurgen F

    2012-03-01

    Full Text Available Abstract Saccharomyces cerevisiae CEN.PK 113-7D is widely used for metabolic engineering and systems biology research in industry and academia. We sequenced, assembled, annotated and analyzed its genome. Single-nucleotide variations (SNV, insertions/deletions (indels and differences in genome organization compared to the reference strain S. cerevisiae S288C were analyzed. In addition to a few large deletions and duplications, nearly 3000 indels were identified in the CEN.PK113-7D genome relative to S288C. These differences were overrepresented in genes whose functions are related to transcriptional regulation and chromatin remodelling. Some of these variations were caused by unstable tandem repeats, suggesting an innate evolvability of the corresponding genes. Besides a previously characterized mutation in adenylate cyclase, the CEN.PK113-7D genome sequence revealed a significant enrichment of non-synonymous mutations in genes encoding for components of the cAMP signalling pathway. Some phenotypic characteristics of the CEN.PK113-7D strains were explained by the presence of additional specific metabolic genes relative to S288C. In particular, the presence of the BIO1 and BIO6 genes correlated with a biotin prototrophy of CEN.PK113-7D. Furthermore, the copy number, chromosomal location and sequences of the MAL loci were resolved. The assembled sequence reveals that CEN.PK113-7D has a mosaic genome that combines characteristics of laboratory strains and wild-industrial strains.

  11. The level of glucose-6-phosphate dehydrogenase activity strongly influences xylose fermentation and inhibitor sensitivity in recombinant Saccharomyces cerevisiae strains

    DEFF Research Database (Denmark)

    Jeppsson, M.; Johansson, B.; Jensen, Peter Ruhdal;

    2003-01-01

    Disruption of the ZWF1 gene encoding glucose-6-phosphate dehydrogenase (G6PDH) has been shown to reduce the xylitol yield and the xylose consumption in the xylose-utilizing recombinant Saccharomyces cerevisiae strain TMB3255. In the present investigation we have studied the influence of different...... consumption, respectively, compared with the ZWF1-disrupted strain. Both strains exhibited decreased xylitol yields (0.13 and 0.19 g/g xylose) and enhanced ethanol yields (0.36 and 0.34 g/g xylose) compared with the control strain TMB3001 (0.29 g xylitol/g xylose, 0.31 g ethanol/g xylose). Cytoplasmic...... transhydrogenase (TH) from Azotobacter vinelandii has previously been shown to transfer NADPH and NAD(+) into NADP(+) and NADH, and TH-overproduction resulted in lower xylitol yield and enhanced glycerol yield during xylose utilization. Strains with low G6PDH-activity grew slower in a lignocellulose hydrolysate...

  12. Engineering the oxygen sensing regulation results in an enhanced recombinant human hemoglobin production by Saccharomyces cerevisiae.

    Science.gov (United States)

    Martínez, José L; Liu, Lifang; Petranovic, Dina; Nielsen, Jens

    2015-01-01

    Efficient production of appropriate oxygen carriers for transfusions (blood substitutes or artificial blood) has been pursued for many decades, and to date several strategies have been used, from synthetic polymers to cell-free hemoglobin carriers. The recent advances in the field of metabolic engineering also allowed the generation of different genetically modified organisms for the production of recombinant human hemoglobin. Several studies have showed very promising results using the bacterium Escherichia coli as a production platform, reporting hemoglobin titers above 5% of the total cell protein content. However, there are still certain limitations regarding the protein stability and functionality of the recombinant hemoglobin produced in bacterial systems. In order to overcome these limitations, yeast systems have been proposed as the eukaryal alternative. We recently reported the generation of a set of plasmids to produce functional human hemoglobin in Saccharomyces cerevisiae, with final titers of active hemoglobin exceeding 4% of the total cell protein. In this study, we propose a strategy for further engineering S. cerevisiae by altering the oxygen sensing pathway by deleting the transcription factor HAP1, which resulted in an increase of the final recombinant active hemoglobin titer exceeding 7% of the total cellular protein.

  13. Metabolic engineering of Saccharomyces cerevisiae microbial cell factories for succinic acid production

    DEFF Research Database (Denmark)

    Otero, José Manuel; Olsson, Lisbeth; Nielsen, Jens

    2007-01-01

    deletions and over-expression, mutants that overproduce succinic acid have been engineered and thoroughly characterised. Metabolic engineering approaches developed promise to have broad applicability to industrial biotechnology platforms, as well as enhancing fundamental understanding of central carbon...... products is 18, 14, 54, and 9 C-mol/C-mol-glucose, respectively, with biotechnology production is C4 organic acids, encompassing fumaric, malic, and succinic acid. Succinic acid is a key building block molecule...... of systems biology tools to drive C6 carbon flux to succinic acid by enhancement of the two native pathways for succinic acid production: the TCA and glyoxylate cycles. S. cerevisiae does not naturally accumulate succinic acid; however, through the use of in silico metabolic predictions guiding targeted gene...

  14. Whole Genome Comparison Reveals High Levels of Inbreeding and Strain Redundancy Across the Spectrum of Commercial Wine Strains of Saccharomyces cerevisiae

    Directory of Open Access Journals (Sweden)

    Anthony R. Borneman

    2016-04-01

    Full Text Available Humans have been consuming wines for more than 7000 yr . For most of this time, fermentations were presumably performed by strains of Saccharomyces cerevisiae that naturally found their way into the fermenting must . In contrast, most commercial wines are now produced by inoculation with pure yeast monocultures, ensuring consistent, reliable and reproducible fermentations, and there are now hundreds of these yeast starter cultures commercially available. In order to thoroughly investigate the genetic diversity that has been captured by over 50 yr of commercial wine yeast development and domestication, whole genome sequencing has been performed on 212 strains of S. cerevisiae, including 119 commercial wine and brewing starter strains, and wine isolates from across seven decades. Comparative genomic analysis indicates that, despite their large numbers, commercial strains, and wine strains in general, are extremely similar genetically, possessing all of the hallmarks of a population bottle-neck, and high levels of inbreeding. In addition, many commercial strains from multiple suppliers are nearly genetically identical, suggesting that the limits of effective genetic variation within this genetically narrow group may be approaching saturation.

  15. Whole Genome Comparison Reveals High Levels of Inbreeding and Strain Redundancy Across the Spectrum of Commercial Wine Strains of Saccharomyces cerevisiae.

    Science.gov (United States)

    Borneman, Anthony R; Forgan, Angus H; Kolouchova, Radka; Fraser, James A; Schmidt, Simon A

    2016-01-01

    Humans have been consuming wines for more than 7000 yr . For most of this time, fermentations were presumably performed by strains of Saccharomyces cerevisiae that naturally found their way into the fermenting must . In contrast, most commercial wines are now produced by inoculation with pure yeast monocultures, ensuring consistent, reliable and reproducible fermentations, and there are now hundreds of these yeast starter cultures commercially available. In order to thoroughly investigate the genetic diversity that has been captured by over 50 yr of commercial wine yeast development and domestication, whole genome sequencing has been performed on 212 strains of S. cerevisiae, including 119 commercial wine and brewing starter strains, and wine isolates from across seven decades. Comparative genomic analysis indicates that, despite their large numbers, commercial strains, and wine strains in general, are extremely similar genetically, possessing all of the hallmarks of a population bottle-neck, and high levels of inbreeding. In addition, many commercial strains from multiple suppliers are nearly genetically identical, suggesting that the limits of effective genetic variation within this genetically narrow group may be approaching saturation. PMID:26869621

  16. Whole Genome Comparison Reveals High Levels of Inbreeding and Strain Redundancy Across the Spectrum of Commercial Wine Strains of Saccharomyces cerevisiae

    Science.gov (United States)

    Borneman, Anthony R.; Forgan, Angus H.; Kolouchova, Radka; Fraser, James A.; Schmidt, Simon A.

    2016-01-01

    Humans have been consuming wines for more than 7000 yr . For most of this time, fermentations were presumably performed by strains of Saccharomyces cerevisiae that naturally found their way into the fermenting must . In contrast, most commercial wines are now produced by inoculation with pure yeast monocultures, ensuring consistent, reliable and reproducible fermentations, and there are now hundreds of these yeast starter cultures commercially available. In order to thoroughly investigate the genetic diversity that has been captured by over 50 yr of commercial wine yeast development and domestication, whole genome sequencing has been performed on 212 strains of S. cerevisiae, including 119 commercial wine and brewing starter strains, and wine isolates from across seven decades. Comparative genomic analysis indicates that, despite their large numbers, commercial strains, and wine strains in general, are extremely similar genetically, possessing all of the hallmarks of a population bottle-neck, and high levels of inbreeding. In addition, many commercial strains from multiple suppliers are nearly genetically identical, suggesting that the limits of effective genetic variation within this genetically narrow group may be approaching saturation. PMID:26869621

  17. Production of 3-hydroxypropionic acid from glucose and xylose by metabolically engineered Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Kildegaard, Kanchana Rueksomtawin; Wang, Zheng; Chen, Yun;

    2015-01-01

    biomass into the products of interest. We engineered Saccharomyces cerevisiae for production of 3-hydroxypropionic acid (3HP), a potential building block for acrylates, from glucose and xylose. We introduced the 3HP biosynthetic pathways via malonyl-CoA or β-alanine intermediates into a xylose...

  18. Production of 3-hydroxypropionic acid from glucose and xylose by metabolically engineered Saccharomyces cerevisiae

    Directory of Open Access Journals (Sweden)

    Kanchana R. Kildegaard

    2015-12-01

    Full Text Available Biomass, the most abundant carbon source on the planet, may in the future become the primary feedstock for production of fuels and chemicals, replacing fossil feedstocks. This will, however, require development of cell factories that can convert both C6 and C5 sugars present in lignocellulosic biomass into the products of interest. We engineered Saccharomyces cerevisiae for production of 3-hydroxypropionic acid (3HP, a potential building block for acrylates, from glucose and xylose. We introduced the 3HP biosynthetic pathways via malonyl-CoA or β-alanine intermediates into a xylose-consuming yeast. Using controlled fed-batch cultivation, we obtained 7.37±0.17 g 3HP L−1 in 120 hours with an overall yield of 29±1% Cmol 3HP Cmol−1 xylose. This study is the first demonstration of the potential of using S. cerevisiae for production of 3HP from the biomass sugar xylose.

  19. Comparing the xylose reductase/xylitol dehydrogenase and xylose isomerase pathways in arabinose and xylose fermenting Saccharomyces cerevisiae strains

    Science.gov (United States)

    Bettiga, Maurizio; Hahn-Hägerdal, Bärbel; Gorwa-Grauslund, Marie F

    2008-01-01

    Background Ethanolic fermentation of lignocellulosic biomass is a sustainable option for the production of bioethanol. This process would greatly benefit from recombinant Saccharomyces cerevisiae strains also able to ferment, besides the hexose sugar fraction, the pentose sugars, arabinose and xylose. Different pathways can be introduced in S. cerevisiae to provide arabinose and xylose utilisation. In this study, the bacterial arabinose isomerase pathway was combined with two different xylose utilisation pathways: the xylose reductase/xylitol dehydrogenase and xylose isomerase pathways, respectively, in genetically identical strains. The strains were compared with respect to aerobic growth in arabinose and xylose batch culture and in anaerobic batch fermentation of a mixture of glucose, arabinose and xylose. Results The specific aerobic arabinose growth rate was identical, 0.03 h-1, for the xylose reductase/xylitol dehydrogenase and xylose isomerase strain. The xylose reductase/xylitol dehydrogenase strain displayed higher aerobic growth rate on xylose, 0.14 h-1, and higher specific xylose consumption rate in anaerobic batch fermentation, 0.09 g (g cells)-1 h-1 than the xylose isomerase strain, which only reached 0.03 h-1 and 0.02 g (g cells)-1h-1, respectively. Whereas the xylose reductase/xylitol dehydrogenase strain produced higher ethanol yield on total sugars, 0.23 g g-1 compared with 0.18 g g-1 for the xylose isomerase strain, the xylose isomerase strain achieved higher ethanol yield on consumed sugars, 0.41 g g-1 compared with 0.32 g g-1 for the xylose reductase/xylitol dehydrogenase strain. Anaerobic fermentation of a mixture of glucose, arabinose and xylose resulted in higher final ethanol concentration, 14.7 g l-1 for the xylose reductase/xylitol dehydrogenase strain compared with 11.8 g l-1 for the xylose isomerase strain, and in higher specific ethanol productivity, 0.024 g (g cells)-1 h-1 compared with 0.01 g (g cells)-1 h-1 for the xylose reductase

  20. Comparing the xylose reductase/xylitol dehydrogenase and xylose isomerase pathways in arabinose and xylose fermenting Saccharomyces cerevisiae strains

    Directory of Open Access Journals (Sweden)

    Hahn-Hägerdal Bärbel

    2008-10-01

    Full Text Available Abstract Background Ethanolic fermentation of lignocellulosic biomass is a sustainable option for the production of bioethanol. This process would greatly benefit from recombinant Saccharomyces cerevisiae strains also able to ferment, besides the hexose sugar fraction, the pentose sugars, arabinose and xylose. Different pathways can be introduced in S. cerevisiae to provide arabinose and xylose utilisation. In this study, the bacterial arabinose isomerase pathway was combined with two different xylose utilisation pathways: the xylose reductase/xylitol dehydrogenase and xylose isomerase pathways, respectively, in genetically identical strains. The strains were compared with respect to aerobic growth in arabinose and xylose batch culture and in anaerobic batch fermentation of a mixture of glucose, arabinose and xylose. Results The specific aerobic arabinose growth rate was identical, 0.03 h-1, for the xylose reductase/xylitol dehydrogenase and xylose isomerase strain. The xylose reductase/xylitol dehydrogenase strain displayed higher aerobic growth rate on xylose, 0.14 h-1, and higher specific xylose consumption rate in anaerobic batch fermentation, 0.09 g (g cells-1 h-1 than the xylose isomerase strain, which only reached 0.03 h-1 and 0.02 g (g cells-1h-1, respectively. Whereas the xylose reductase/xylitol dehydrogenase strain produced higher ethanol yield on total sugars, 0.23 g g-1 compared with 0.18 g g-1 for the xylose isomerase strain, the xylose isomerase strain achieved higher ethanol yield on consumed sugars, 0.41 g g-1 compared with 0.32 g g-1 for the xylose reductase/xylitol dehydrogenase strain. Anaerobic fermentation of a mixture of glucose, arabinose and xylose resulted in higher final ethanol concentration, 14.7 g l-1 for the xylose reductase/xylitol dehydrogenase strain compared with 11.8 g l-1 for the xylose isomerase strain, and in higher specific ethanol productivity, 0.024 g (g cells-1 h-1 compared with 0.01 g (g cells-1 h-1

  1. Engineering Saccharomyces cerevisiae for direct conversion of raw, uncooked or granular starch to ethanol.

    Science.gov (United States)

    Görgens, Johann F; Bressler, David C; van Rensburg, Eugéne

    2015-01-01

    The production of raw starch-degrading amylases by recombinant Saccharomyces cerevisiae provides opportunities for the direct hydrolysis and fermentation of raw starch to ethanol without cooking or exogenous enzyme addition. Such a consolidated bioprocess (CBP) for raw starch fermentation will substantially reduce costs associated with energy usage and commercial granular starch hydrolyzing (GSH) enzymes. The core purpose of this review is to provide comprehensive insight into the physiological impact of recombinant amylase production on the ethanol-producing yeast. Key production parameters, based on outcomes from modifications to the yeast genome and levels of amylase production, were compared to key benchmark data. In turn, these outcomes are of significance from a process point of view to highlight shortcomings in the current state of the art of raw starch fermentation yeast compared to a set of industrial standards. Therefore, this study provides an integrated critical assessment of physiology, genetics and process aspects of recombinant raw starch fermenting yeast in relation to presently used technology. Various approaches to strain development were compared on a common basis of quantitative performance measures, including the extent of hydrolysis, fermentation-hydrolysis yield and productivity. Key findings showed that levels of α-amylase required for raw starch hydrolysis far exceeded enzyme levels for soluble starch hydrolysis, pointing to a pre-requisite for excess α-amylase compared to glucoamylase for efficient raw starch hydrolysis. However, the physiological limitations of amylase production by yeast, requiring high biomass concentrations and long cultivation periods for sufficient enzyme accumulation under anaerobic conditions, remained a substantial challenge. Accordingly, the fermentation performance of the recombinant S. cerevisiae strains reviewed in this study could not match the performance of conventional starch fermentation processes

  2. EDITORIAL: Excelling under strain: band engineering in nanomaterials Excelling under strain: band engineering in nanomaterials

    Science.gov (United States)

    Demming, Anna

    2013-08-01

    A little stress or strain has been known to improve the performance of athletes, actors and of course nanomaterials alike. In fact strain in silicon is now a major engineering tool for improving the performance of devices, and is ubiquitously used in device design and fabrication. Strain engineering alters a material's band structure, a model of electron behaviour that describes how as atoms come together in a solid, their discrete electron orbitals overlap to ultimately give rise to bands of allowed energy levels. In a strained crystal lattice of silicon or silicon germanium the distance between atoms in the lattice is greater than usual and the bands of allowed energy levels change. This July marks 100 years since Bohr submitted his paper 'On the constitution of atoms and molecules' [1] where he describes the structure of the atom in terms of discrete allowed energy levels. The paper was a seminal contribution to the development of quantum mechanics and laid the initial theoretical precepts for band gap engineering in devices. In this issue Nrauda and a collaboration of researchers in Europe and Australia study the growth of defect-free SiGe islands on pre-patterned silicon [2]. They analyse the strain in the islands and determine at what point lattice dislocations set in with a view to informing implementation of strain engineering in devices. The effects of strain on band structure in silicon and germanium were already studied and reported in the 1950s [3, 4]. Since then the increasing focus on nanoscale materials and the hunger for control of electronic properties has prompted further study of strain effects. The increased surface area to volume ratio in nanostructures changes the strain behaviour with respect to bulk materials, and this can also be exploited for handling and fine tuning strain to manipulate material properties. It is perhaps no surprise that graphene, one of the most high-profile materials in current nanotechnology research, has attracted

  3. De novo production of resveratrol from glucose or ethanol by engineered Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Li, Mingji; Kildegaard, Kanchana Rueksomtawin; Chen, Yun;

    2015-01-01

    Resveratrol is a natural antioxidant compound, used as food supplement and cosmetic ingredient. Microbial production of resveratrol has until now been achieved by supplementation of expensive substrates, p-coumaric acid or aromatic amino acids. Here we engineered the yeast Saccharomyces cerevisiae...... to produce resveratrol directly from glucose or ethanol via tyrosine intermediate. First we introduced the biosynthetic pathway, consisting of tyrosine ammonia-lyase from Herpetosiphon aurantiacus, 4-coumaryl-CoA ligase from Arabidopsis thaliana and resveratrol synthase from Vitis vinifera, and obtained 2.......73±0.05 mg L−1 resveratrol from glucose. Then we over-expressed feedback-insensitive alleles of ARO4 encoding 3-deoxy-D-arabino-heptulosonate-7-phosphate and ARO7 encoding chorismate mutase, resulting in production of 4.85±0.31 mg L−1 resveratrol from glucose as the sole carbon source. Next we improved...

  4. Development of flocculent Saccharomyces cerevisiae strain GYK-10 for the selective fermentation of glucose/fructose in sugar mills.

    Science.gov (United States)

    Kato, Taku; Ohara, Satoshi; Fukushima, Yasuhiro; Sugimoto, Akira; Masuda, Takayuki; Yasuhara, Takaomi; Yamagishi, Hiromi

    2016-07-01

    Advances in glucose/fructose-selective ethanol production have successfully enhanced raw sugar extraction from sugarcane juice by converting inhibitory substances (i.e., glucose/fructose) into ethanol, which is removed by subsequent operations in cane sugar mills. However, the commercial implementation of this breakthrough process in existing cane sugar mills requires a yeast strain that (i) can be used in food production processes, (ii) exhibits stable saccharometabolic selectivity, and (iii) can be easily separated from the saccharide solution. In this study, we developed a suitable saccharometabolism-selective and flocculent strain, Saccharomyces cerevisiae GYK-10. We obtained a suitable yeast strain for selective fermentation in cane sugar mills using a yeast mating system. First, we crossed a haploid strain defective in sucrose utilization with a flocculent haploid strain. Next, we performed tetrad dissection of the resultant hybrid diploid strain and selected GYK-10 from various segregants by investigating the sucrose assimilation and flocculation capacity phenotypes. Ten consecutive fermentation tests of the GYK-10 strain using a bench-scale fermentor confirmed its suitability for the implementation of practical selective fermentation in a commercial sugar mill. The strain exhibited complete saccharometabolic selectivity and sustained flocculation, where it maintained a high ethanol yield and conversion rate throughout the test. PMID:26811219

  5. Genome Sequences of Industrially Relevant Saccharomyces cerevisiae Strain M3707, Isolated from a Sample of Distillers Yeast and Four Haploid Derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Steven D.; Klingeman, Dawn M.; Johnson, Courtney M.; Clum, Alicia; Aerts, Andrea; Salamov, Asaf; Sharma, Aditi; Zane, Matthew; Barry, Kerrie; Grigoriev, Igor V.; Davison, Brian H.; Lynd, Lee R.; Gilna, Paul; Hau, Heidi; Hogsett, David A.; Froehlich, Allan C.

    2013-04-19

    Saccharomyces cerevisiae strain M3707 was isolated from a sample of commercial distillers yeast, and its genome sequence together with the genome sequences for the four derived haploid strains M3836, M3837, M3838, and M3839 has been determined. Yeasts have potential for consolidated bioprocessing (CBP) for biofuel production, and access to these genome sequences will facilitate their development.

  6. Expression of the bacterial recA gene impairs genetic recombination and sporulation in a Saccharomyces cerevisiae diploid strain

    Directory of Open Access Journals (Sweden)

    Marcos Antonio de Morais Junior

    2003-01-01

    Full Text Available The Escherichia coli RecA protein (RecAp has been demonstrated to induce mutagenesis in yeast cells, although there is still little information on the role of the RecAp in yeast recombination events. We evaluated spontaneous and induced general recombination in vegetative and meiotic cells of the XS2316 strain of the yeast Saccharomyces cerevisiae bearing the recA gene. We found that RecAp decreased reciprocal recombination, gene conversion and intrachromosomal recombination and promoted an increase in error-prone processes in both vegetative and meiotic cells, while its negative effect on meiotic recombination blocked ascospore formation.

  7. High Level Ethanol from Sugar Cane Molasses by a New Thermotolerant Saccharomyces cerevisiae Strain in Industrial Scale

    OpenAIRE

    Fadel, M.; Abeer A. Keera; Mouafi, Foukia E.; Tarek Kahil

    2013-01-01

    A new local strain of S. cerevisiae F-514, for ethanol production during hot summer season, using Egyptian sugar cane molasses was applied in Egyptian distillery factory. The inouluum was propagated through 300 L, 3 m3, and 12 m3 fermenters charged with diluted sugar cane molasses containing 4%-5% sugars. The yeast was applied in fermentation vessels 65 m3 working volume to study the varying concentrations of urea, DAP, orthophosphoric acid (OPA), and its combinations as well as magnesium sul...

  8. The effect of hexose ratios on metabolite production in Saccharomyces cerevisiae strains obtained from the spontaneous fermentation of mezcal.

    Science.gov (United States)

    Oliva Hernández, Amanda A; Taillandier, Patricia; Reséndez Pérez, Diana; Narváez Zapata, José A; Larralde Corona, Claudia Patricia

    2013-04-01

    Mezcal from Tamaulipas (México) is produced by spontaneous alcoholic fermentation using Agave spp. musts, which are rich in fructose. In this study eight Saccharomyces cerevisiae isolates obtained at the final stage of fermentation from a traditional mezcal winery were analysed in three semi-synthetic media. Medium M1 had a sugar content of 100 g l(-1) and a glucose/fructose (G/F) of 9:1. Medium M2 had a sugar content of 100 g l(-1) and a G/F of 1:9. Medium M3 had a sugar content of 200 g l(-1) and a G/F of 1:1. In the three types of media tested, the highest ethanol yield was obtained from the glucophilic strain LCBG-3Y5, while strain LCBG-3Y8 was highly resistant to ethanol and the most fructophilic of the mezcal strains. Strain LCBG-3Y5 produced more glycerol (4.4 g l(-1)) and acetic acid (1 g l(-1)) in M2 than in M1 (1.7 and 0.5 g l(-1), respectively), and the ethanol yields were higher for all strains in M1 except for LCBG-3Y5, -3Y8 and the Fermichamp strain. In medium M3, only the Fermichamp strain was able to fully consume the 100 g of fructose l(-1) but left a residual 32 g of glucose l(-1). Regarding the hexose transporters, a high number of amino acid polymorphisms were found in the Hxt1p sequences. Strain LCBG-3Y8 exhibited eight unique amino acid changes, followed by the Fermichamp strain with three changes. In Hxt3p, we observed nine amino acid polymorphisms unique for the Fermichamp strain and five unique changes for the mezcal strains.

  9. Combined metabolic engineering of precursor and co-factor supply to increase α-santalene production by Saccharomyces cerevisiae

    Directory of Open Access Journals (Sweden)

    Scalcinati Gionata

    2012-08-01

    Full Text Available Abstract Background Sesquiterpenes are a class of natural products with a diverse range of attractive industrial proprieties. Due to economic difficulties of sesquiterpene production via extraction from plants or chemical synthesis there is interest in developing alternative and cost efficient bioprocesses. The hydrocarbon α-santalene is a precursor of sesquiterpenes with relevant commercial applications. Here, we construct an efficient Saccharomyces cerevisiae cell factory for α-santalene production. Results A multistep metabolic engineering strategy targeted to increase precursor and cofactor supply was employed to manipulate the yeast metabolic network in order to redirect carbon toward the desired product. To do so, genetic modifications were introduced acting to optimize the farnesyl diphosphate branch point, modulate the mevalonate pathway, modify the ammonium assimilation pathway and enhance the activity of a transcriptional activator. The approach employed resulted in an overall α-santalene yield of a 0.0052 Cmmol (Cmmol glucose-1 corresponding to a 4-fold improvement over the reference strain. This strategy, combined with a specifically developed continuous fermentation process, led to a final α-santalene productivity of 0.036 Cmmol (g biomass-1 h-1. Conclusions The results reported in this work illustrate how the combination of a metabolic engineering strategy with fermentation technology optimization can be used to obtain significant amounts of the high-value sesquiterpene α-santalene. This represents a starting point toward the construction of a yeast “sesquiterpene factory” and for the development of an economically viable bio-based process that has the potential to replace the current production methods.

  10. Efficient fermentation of xylose to ethanol at high formic acid concentrations by metabolically engineered Saccharomyces cerevisiae

    Energy Technology Data Exchange (ETDEWEB)

    Hasunuma, Tomohisa; Yoshimura, Kazuya; Matsuda, Fumio [Kobe Univ., Hyogo (Japan). Organization of Advanced Science and Technology; Sung, Kyung-mo; Sanda, Tomoya; Kondo, Akihiko [Kobe Univ., Hyogo (Japan). Dept. of Chemical Science and Engineering

    2011-05-15

    Recombinant yeast strains highly tolerant to formic acid during xylose fermentation were constructed. Microarray analysis of xylose-fermenting Saccharomyces cerevisiae strain overexpressing endogenous xylulokinase in addition to xylose reductase and xylitol dehydrogenase from Pichia stipitis revealed that upregulation of formate dehydrogenase genes (FDH1 and FDH2) was one of the most prominent transcriptional events against excess formic acid. The quantification of formic acid in medium indicated that the innate activity of FDH was too weak to detoxify formic acid. To reinforce the capability for formic acid breakdown, the FDH1 gene was additionally overexpressed in the xylose-metabolizing recombinant yeast. This modification allowed the yeast to rapidly decompose excess formic acid. The yield and final ethanol concentration in the presence of 20 mM formic acid is as essentially same as that of control. The fermentation profile also indicated that the production of xylitol and glycerol, major by-products in xylose fermentation, was not affected by the upregulation of FDH activity. (orig.)

  11. Construction of recombinant industrial Saccharomyces cerevisiae strain with bglS gene insertion into PEP4 locus by homologous recombination

    Institute of Scientific and Technical Information of China (English)

    Qiang ZHANG; Qi-he CHEN; Ming-liang FU; Jin-ling WANG; Hong-bo ZHANG; Guo-qing HE

    2008-01-01

    The bglS gene encoding endo-1,3-1,4-β-glucanase from Bacillus subtilis was cloned and sequenced in this study. The bglS expression cassette, including PGK1 promoter, bglS gene fused to the signal sequence of the yeast mating pheromone α-factor (MFals), and ADH1 terminator with G418-resistance as the selected marker, was constructed. Then one of the PEP4 allele of Saccharomyces cerevisiae WZ65 strain was replaced by bglS expression cassette using chromosomal integration of polymerase chain reaction (PCR)-mediated homologous recombination, and the bglS gene was expressed simultaneously. The recombinant strain S. cerevisiae (SC-βG) was preliminarily screened by the clearing hydrolysis zone formed after the barley β-glucan was hydrolyzed in the plate and no proteinase A (PrA) activity was measured in fermenting liquor. The results of PCR analysis ofgenome DNA showed that one of the PEP4 allele had been replaced and bglS gene had been inserted into the locus of PEP4 gene in recombinant strains. Different endo-1,3-1,4-β-glucanase assay methods showed that the recombinant strain SC-βG had high endo-1,3-1,4-β-glucanase expression level with the maximum of 69.3 U/(h-ml) after 60 h of incubation. Meanwhile, the Congo Red method was suitable for the determination of endo-1,3-1,4-β-glucanase activity during the actual brewing process. The current research implies that the constructed yeast strain could be utilized to improve the industrial brewing property of beer.

  12. Comparative study of Saccharomyces cerevisiae wine strains to identify potential marker genes correlated to desiccation stress tolerance.

    Science.gov (United States)

    Capece, Angela; Votta, Sonia; Guaragnella, Nicoletta; Zambuto, Marianna; Romaniello, Rossana; Romano, Patrizia

    2016-05-01

    The most diffused formulation of starter for winemaking is active dry yeast (ADY). ADYs production process is essentially characterized by air-drying stress, a combination of several stresses, including thermal, hyperosmotic and oxidative and cell capacity to counteract such multiple stresses will determine its survival. The molecular mechanisms underlying cell stress response to desiccation have been mostly studied in laboratory and commercial yeast strains, but a growing interest is currently developing for indigenous yeast strains which represent a valuable and alternative source of genetic and molecular biodiversity to be exploited. In this work, a comparative study of different Saccharomyces cerevisiae indigenous wine strains, previously selected for their technological traits, has been carried out to identify potentially relevant genes involved in desiccation stress tolerance. Cell viability was evaluated along desiccation treatment and gene expression was analyzed by real-time PCR before and during the stress. Our data show that the observed differences in individual strain sensitivity to desiccation stress could be associated to specific gene expression over time. In particular, either the basal or the stress-induced mRNA levels of certain genes, such as HSP12, SSA3, TPS1, TPS2, CTT1 and SOD1, result tightly correlated to the strain survival advantage. This study provides a reliable and sensitive method to predict desiccation stress tolerance of indigenous wine yeast strains which could be preliminary to biotechnological applications. PMID:26882930

  13. Nuclear and mitochondrial genome instability induced by senna (Cassia angustifolia Vahl.) aqueous extract in Saccharomyces cerevisiae strains.

    Science.gov (United States)

    Silva, C R; Caldeira-de-Araújo, A; Leitão, A C; Pádula, M

    2014-11-27

    Cassia angustifolia Vahl. (senna) is commonly used in self-medication and is frequently used to treat intestine constipation. A previous study involving bacteria and plasmid DNA suggested the possible toxicity of the aqueous extract of senna (SAE). The aim of this study was to extend the knowledge concerning SAE genotoxicity mechanisms because of its widespread use and its risks to human health. We investigated the impact of SAE on nuclear DNA and on the stability of mitochondrial DNA in Saccharomyces cerevisiae (wt, ogg1, msh6, and ogg1msh6) strains, monitoring the formation of petite mutants. Our results demonstrated that SAE specifically increased Can(R) mutagenesis only in the msh6 mutant, supporting the view that SAE can induce misincorporation errors in DNA. We observed a significant increase in the frequency of petite colonies in all studied strains. Our data indicate that SAE has genotoxic activity towards both mitochondrial and nuclear DNA.

  14. Disruption of seven hypothetical aryl alcohol dehydrogenase genes from Saccharomyces cerevisiae and construction of a multiple knock-out strain.

    Science.gov (United States)

    Delneri, D; Gardner, D C; Bruschi, C V; Oliver, S G

    1999-11-01

    By in silicio analysis, we have discovered that there are seven open reading frames (ORFs) in Saccharomyces cerevisiae whose protein products show a high degree of amino acid sequence similarity to the aryl alcohol dehydrogenase (AAD) of the lignin-degrading fungus Phanerochaete chrysosporium. Yeast cultures grown to stationary phase display a significant aryl alcohol dehydrogenase activity by degrading aromatic aldehydes to the corresponding alcohols. To study the biochemical and the biological role of each of the AAD genes, a series of mutant strains carrying deletion of one or more of the AAD-coding sequences was constructed by PCR-mediated gene replacement, using the readily selectable marker kanMX. The correct targeting of the PCR-generated disruption cassette into the genomic locus was verified by analytical PCR and by pulse-field gel electrophoresis (PFGE) followed by Southern blot analysis. Double, triple and quadruple mutant strains were obtained by classical genetic methods, while the construction of the quintuple, sextuple and septuple mutants was achieved by using the marker URA3 from Kluyveromyces lactis, HIS3 from Schizosaccharomyces pombe and TRP1 from S. cerevisiae. None of the knock-out strains revealed any mutant phenotype when tested for the degradation of aromatic aldehydes using both spectrophotometry and high performance liquid chromatography (HPLC). Specific tests for changes in the ergosterol and phospholipids profiles did not reveal any mutant phenotype and mating and sporulation efficiencies were not affected in the septuple deletant. Compared to the wild-type strain, the septuple deletant showed an increased resistance to the anisaldehyde, but there is a possibility that the nutritional markers used for gene replacement are causing this effect.

  15. Zearalenone and Its Derivatives α-Zearalenol and β-Zearalenol Decontamination by Saccharomyces cerevisiae Strains Isolated from Bovine Forage

    Science.gov (United States)

    Keller, Luiz; Abrunhosa, Luís; Keller, Kelly; Rosa, Carlos Alberto; Cavaglieri, Lilia; Venâncio, Armando

    2015-01-01

    Zearalenone (ZEA) and its derivatives are mycotoxins with estrogenic effects on mammals. The biotransformation for ZEA in animals involves the formation of two major metabolites, α- and β-zearalenol (α-ZOL and β-ZOL), which are subsequently conjugated with glucuronic acid. The capability of Saccharomyces cerevisiae strains isolated from silage to eliminate ZEA and its derivatives α-ZOL and β-ZOL was investigated as, also, the mechanisms involved. Strains were grown on Yeast Extract-Peptone-Dextrose medium supplemented with the mycotoxins and their elimination from medium was quantified over time by HPLC-FL. A significant effect on the concentration of ZEA was observed, as all the tested strains were able to eliminate more than 90% of the mycotoxin from the culture medium in two days. The observed elimination was mainly due to ZEA biotransformation into β-ZOL (53%) and α-ZOL (8%) rather than to its adsorption to yeast cells walls. Further, the biotransformation of α-ZOL was not observed but a small amount of β-ZOL (6%) disappeared from culture medium. ZEA biotransformation by yeasts may not be regarded as a full detoxification process because both main end-products are still estrogenic. Nonetheless, it was observed that the biotransformation favors the formation of β-ZOL which is less estrogenic than ZEA and α-ZOL. This metabolic effect is only possible if active strains are used as feed additives and may play a role in the detoxification performance of products with viable S. cerevisiae cells. PMID:26308051

  16. Zearalenone and Its Derivatives α-Zearalenol and β-Zearalenol Decontamination by Saccharomyces cerevisiae Strains Isolated from Bovine Forage

    Directory of Open Access Journals (Sweden)

    Luiz Keller

    2015-08-01

    Full Text Available Zearalenone (ZEA and its derivatives are mycotoxins with estrogenic effects on mammals. The biotransformation for ZEA in animals involves the formation of two major metabolites, α- and β-zearalenol (α-ZOL and β-ZOL, which are subsequently conjugated with glucuronic acid. The capability of Saccharomyces cerevisiae strains isolated from silage to eliminate ZEA and its derivatives α-ZOL and β-ZOL was investigated as, also, the mechanisms involved. Strains were grown on Yeast Extract-Peptone-Dextrose medium supplemented with the mycotoxins and their elimination from medium was quantified over time by HPLC-FL. A significant effect on the concentration of ZEA was observed, as all the tested strains were able to eliminate more than 90% of the mycotoxin from the culture medium in two days. The observed elimination was mainly due to ZEA biotransformation into β-ZOL (53% and α-ZOL (8% rather than to its adsorption to yeast cells walls. Further, the biotransformation of α-ZOL was not observed but a small amount of β-ZOL (6% disappeared from culture medium. ZEA biotransformation by yeasts may not be regarded as a full detoxification process because both main end-products are still estrogenic. Nonetheless, it was observed that the biotransformation favors the formation of β-ZOL which is less estrogenic than ZEA and α-ZOL. This metabolic effect is only possible if active strains are used as feed additives and may play a role in the detoxification performance of products with viable S. cerevisiae cells.

  17. Differing effects of 2 active dried yeast (Saccharomyces cerevisiae) strains on ruminal acidosis and methane production in nonlactating dairy cows.

    Science.gov (United States)

    Chung, Y-H; Walker, N D; McGinn, S M; Beauchemin, K A

    2011-05-01

    Fifteen ruminally cannulated, nonlactating Holstein cows were used to measure the effects of 2 strains of Saccharomyces cerevisiae, fed as active dried yeasts, on ruminal pH and fermentation and enteric methane (CH(4)) emissions. Nonlactating cows were blocked by total duration (h) that their ruminal pH was below 5.8 during a 6-d pre-experimental period. Within each block, cows were randomly assigned to control (no yeast), yeast strain 1 (Levucell SC), or yeast strain 2 (a novel strain selected for enhanced in vitro fiber degradation), with both strains (Lallemand Animal Nutrition, Montréal, QC, Canada) providing 1 × 10(10) cfu/head per day. Cows were fed once daily a total mixed ration consisting of a 50:50 forage to concentrate ratio (dry matter basis). The yeast strains were dosed via the rumen cannula daily at the time of feeding. During the 35-d experiment, ruminal pH was measured continuously for 7 d (d 22 to 28) by using an indwelling system, and CH(4) gas was measured for 4 d (d 32 to 35) using the sulfur hexafluoride tracer gas technique (with halters and yokes). Rumen contents were sampled on 2 d (d 22 and 26) at 0, 3, and 6h after feeding. Dry matter intake, body weight, and apparent total-tract digestibility of nutrients were not affected by yeast feeding. Strain 2 decreased the average daily minimum (5.35 vs. 5.65 or 5.66), mean (5.98 vs. 6.24 or 6.34), and maximum ruminal pH (6.71 vs. 6.86 or 6.86), and prolonged the time that ruminal pH was below 5.8 (7.5 vs. 3.3 or 1.0 h/d) compared with the control or strain 1, respectively. The molar percentage of acetate was lower and that of propionate was greater in the ruminal fluid of cows receiving strain 2 compared with cows receiving no yeast or strain 1. Enteric CH(4) production adjusted for intake of dry matter or gross energy, however, did not differ between either yeast strain compared with the control but it tended to be reduced by 10% when strain 2 was compared with strain 1. The study shows that

  18. Magneto-strain-driven quantum engine on a graphene flake

    OpenAIRE

    Peña, Francisco J.; Muñoz, Enrique

    2015-01-01

    We propose a novel conceptual design for a graphene-based quantum engine, driven by a superposition of mechanical strain and an external magnetic field. Engineering of strain in a nanoscale graphene flake creates a gauge field with an associated uniform pseudo-magnetic field. The strain-induced pseudo-magnetic field can be combined with a real magnetic field, leading to the emergence of discrete relativistic Landau levels within the single-particle picture. The inter-level distance and hence ...

  19. A strain of Saccharomyces cerevisiae evolved for fermentation of lignocellulosic biomass displays improved growth and fermentative ability in high solids concentrations and in the presence of inhibitory compounds

    Directory of Open Access Journals (Sweden)

    Hawkins Gary M

    2011-11-01

    Full Text Available Abstract Background Softwoods are the dominant source of lignocellulosic biomass in the northern hemisphere, and have been investigated worldwide as a renewable substrate for cellulosic ethanol production. One challenge to using softwoods, which is particularly acute with pine, is that the pretreatment process produces inhibitory compounds detrimental to the growth and metabolic activity of fermenting organisms. To overcome the challenge of bioconversion in the presence of inhibitory compounds, especially at high solids loading, a strain of Saccharomyces cerevisiae was subjected to evolutionary engineering and adaptation for fermentation of pretreated pine wood (Pinus taeda. Results An industrial strain of Saccharomyces, XR122N, was evolved using pretreated pine; the resulting daughter strain, AJP50, produced ethanol much more rapidly than its parent in fermentations of pretreated pine. Adaptation, by preculturing of the industrial yeast XR122N and the evolved strains in 7% dry weight per volume (w/v pretreated pine solids prior to inoculation into higher solids concentrations, improved fermentation performance of all strains compared with direct inoculation into high solids. Growth comparisons between XR122N and AJP50 in model hydrolysate media containing inhibitory compounds found in pretreated biomass showed that AJP50 exited lag phase faster under all conditions tested. This was due, in part, to the ability of AJP50 to rapidly convert furfural and hydroxymethylfurfural to their less toxic alcohol derivatives, and to recover from reactive oxygen species damage more quickly than XR122N. Under industrially relevant conditions of 17.5% w/v pretreated pine solids loading, additional evolutionary engineering was required to decrease the pronounced lag phase. Using a combination of adaptation by inoculation first into a solids loading of 7% w/v for 24 hours, followed by a 10% v/v inoculum (approximately equivalent to 1 g/L dry cell weight into 17

  20. YeastFab: the design and construction of standard biological parts for metabolic engineering in Saccharomyces cerevisiae

    OpenAIRE

    Guo, Yakun; Dong, Junkai; Zhou, Tong; Auxillos, Jamie; Li, Tianyi; Zhang, Weimin; Wang, LiHui; Shen, Yue; Luo, Yisha; Zheng, Yijing; Lin, Jiwei; Chen, Guo-Qiang; Wu, Qingyu; Cai, Yizhi; Dai, Junbiao

    2015-01-01

    It is a routine task in metabolic engineering to introduce multicomponent pathways into a heterologous host for production of metabolites. However, this process sometimes may take weeks to months due to the lack of standardized genetic tools. Here, we present a method for the design and construction of biological parts based on the native genes and regulatory elements in Saccharomyces cerevisiae. We have developed highly efficient protocols (termed YeastFab Assembly) to synthesize these genet...

  1. Determining the fate of fluorescent quantum dots on surface of engineered budding S. cerevisiae cell molecular landscape

    OpenAIRE

    Chouhan, Raghuraj Singh; Qureshi, Anjum; Kolkar Mohammed, Javed Hussain Niazi

    2015-01-01

    In this study, we surface engineered living S. cerevisiae cells by decorating quantum dots (QDs) and traced the fate of QDs on molecular landscape of single mother cell through several generation times (progeny cells). The fate of QDs on cell-surface was tracked through the cellular division events using confocal microscopy and fluorescence emission profiles. The extent of cell-surface QDs distribution among the offspring was determined as the mother cell divides into daughter cells. Fluoresc...

  2. Enhanced isoprene biosynthesis in Saccharomyces cerevisiae by engineering of the native acetyl-CoA and mevalonic acid pathways with a push-pull-restrain strategy.

    Science.gov (United States)

    Lv, Xiaomei; Xie, Wenping; Lu, Wenqiang; Guo, Fei; Gu, Jiali; Yu, Hongwei; Ye, Lidan

    2014-09-30

    To explore the capacity of isoprene production in Saccharomyces cerevisiae, a rational push-pull-restrain strategy was proposed to engineer the mevalonic acid (MVA) and acetyl-CoA pathways. The strategy can be decomposed into the up-regulation of precursor supply in the acetyl-CoA module and the MVA pathway (push-strategy), increase of the isoprene branch flux (pull-strategy), and down-regulation of the competing pathway (restrain-strategy). Furthermore, to reduce the production cost arising from galactose addition and meanwhile maintain the high expression of Gal promoters, the galactose regulatory network was modulated by Gal80p deletion. Finally, the engineered strain YXM10-ispS-ispS could accumulate up to 37 mg/L isoprene (about 782-fold increase compared to the parental strain) under aerobic conditions with glycerol-sucrose as carbon source. In this way, a new potential platform for isoprene production was established via metabolic engineering of the yeast native pathways.

  3. Vanadium pentoxide effects on stress responses in wine Saccharomyces cerevisiae strain UE-ME3.

    Science.gov (United States)

    Rosado, Tânia; Conim, Ana; Alves-Pereira, Isabel; Ferreira, Rui

    2009-11-01

    Vanadium pentoxide mainly used as catalyst in sulphuric acid, maleic anhydride and ceramics industry, is a pollutant watering redistributed around the environment. Research on biological influence of vanadium pentoxide has gained major importance because it exerts toxic effects on a wide variety of biological systems. In this work we intent to evaluate the effects of vanadium pentoxide ranging from 0 to 2 mM in culture media on a wine wild-type Saccharomyces cerevisiae from Alentejo region of Portugal. Our results show that 2.0 mM vanadium pentoxide in culture medium induced a significant increase of malonaldehyde level and Glutathione peroxidase activity, a slightly increase of Catalase A activity as well as a decrease of wet weight and mitochondrial NADH cit c reductase of S. cerevisiae UE-ME(3). Also our results show that cycloheximide prevent cell death when cells grows 30 min in presence of 1.5 mM of vanadium pentoxide.

  4. Ribozyme-based aminoglycoside switches of gene expression engineered by genetic selection in S. cerevisiae.

    Science.gov (United States)

    Klauser, Benedikt; Atanasov, Janina; Siewert, Lena K; Hartig, Jörg S

    2015-05-15

    Systems for conditional gene expression are powerful tools in basic research as well as in biotechnology. For future applications, it is of great importance to engineer orthogonal genetic switches that function reliably in diverse contexts. RNA-based switches have the advantage that effector molecules interact immediately with regulatory modules inserted into the target RNAs, getting rid of the need of transcription factors usually mediating genetic control. Artificial riboswitches are characterized by their simplicity and small size accompanied by a high degree of modularity. We have recently reported a series of hammerhead ribozyme-based artificial riboswitches that allow for post-transcriptional regulation of gene expression via switching mRNA, tRNA, or rRNA functions. A more widespread application was so far hampered by moderate switching performances and a limited set of effector molecules available. Here, we report the re-engineering of hammerhead ribozymes in order to respond efficiently to aminoglycoside antibiotics. We first established an in vivo selection protocol in Saccharomyces cerevisiae that enabled us to search large sequence spaces for optimized switches. We then envisioned and characterized a novel strategy of attaching the aptamer to the ribozyme catalytic core, increasing the design options for rendering the ribozyme ligand-dependent. These innovations enabled the development of neomycin-dependent RNA modules that switch gene expression up to 25-fold. The presented aminoglycoside-responsive riboswitches belong to the best-performing RNA-based genetic regulators reported so far. The developed in vivo selection protocol should allow for sampling of large sequence spaces for engineering of further optimized riboswitches. PMID:24871672

  5. Transcription activator-like effector nucleases mediated metabolic engineering for enhanced fatty acids production in Saccharomyces cerevisiae

    KAUST Repository

    Aouida, Mustapha

    2015-04-01

    Targeted engineering of microbial genomes holds much promise for diverse biotechnological applications. Transcription activator-like effector nucleases (TALENs) and clustered regularly interspaced short palindromic repeats/Cas9 systems are capable of efficiently editing microbial genomes, including that of Saccharomyces cerevisiae. Here, we demonstrate the use of TALENs to edit the genome of S.cerevisiae with the aim of inducing the overproduction of fatty acids. Heterodimeric TALENs were designed to simultaneously edit the FAA1 and FAA4 genes encoding acyl-CoA synthetases in S.cerevisiae. Functional yeast double knockouts generated using these TALENs over-produce large amounts of free fatty acids into the cell. This study demonstrates the use of TALENs for targeted engineering of yeast and demonstrates that this technology can be used to stimulate the enhanced production of free fatty acids, which are potential substrates for biofuel production. This proof-of-principle study extends the utility of TALENs as excellent genome editing tools and highlights their potential use for metabolic engineering of yeast and other organisms, such as microalgae and plants, for biofuel production. © 2015 The Society for Biotechnology, Japan.

  6. Production of Volatile and Sulfur Compounds by 10 Saccharomyces cerevisiae Strains Inoculated in Trebbiano Must

    OpenAIRE

    Patrignani, Francesca; Chinnici, Fabio; Serrazanetti, Diana I.; Vernocchi, Pamela; Ndagijimana, Maurice; Riponi, Claudio; Lanciotti, Rosalba

    2016-01-01

    In wines, the presence of sulfur compounds is the resulting of several contributions among which yeast metabolism. The characterization of the starter Saccharomyces cerevisiae needs to be performed also taking into account this ability even if evaluated together with the overall metabolic profile. In this perspective, principal aim of this experimental research was the evaluation of the volatile profiles, throughout GC/MS technique coupled with solid phase micro extraction, of wines obtained ...

  7. Enhancing sesquiterpene production in Saccharomyces cerevisiae through in silico driven metabolic engineering

    DEFF Research Database (Denmark)

    Asadollahi, Mohammadali; Maury, Jerome; Patil, Kiran Raosaheb;

    2009-01-01

    A genome-scale metabolic model was used to identify new target genes for enhanced biosynthesis of sesquiterpenes in the yeast Saccharomyces cerevisiae. The effect of gene deletions on the flux distributions in the metabolic model of S. cerevisiae was assessed using OptGene as the modeling framewo...

  8. Enhanced expression of genes involved in initial xylose metabolism and the oxidative pentose phosphate pathway in the improved xylose-utilizing Saccharomyces cerevisiae through evolutionary engineering.

    Science.gov (United States)

    Zha, Jian; Shen, Minghua; Hu, Menglong; Song, Hao; Yuan, Yingjin

    2014-01-01

    Fermentation of xylose in lignocellulosic hydrolysates by Saccharomyces cerevisiae has been achieved through heterologous expression of the xylose reductase (XR)-xylitol dehydrogenase (XDH) pathway. However, the fermentation efficiency is far from the requirement for industrial application due to high yield of the byproduct xylitol, low ethanol yield, and low xylose consumption rate. Through evolutionary engineering, an improved xylose-utilizing strain SyBE005 was obtained with 78.3 % lower xylitol production and a 2.6-fold higher specific ethanol production rate than those of the parent strain SyBE004, which expressed an engineered NADP(+)-preferring XDH. The transcriptional differences between SyBE005 and SyBE004 were investigated by quantitative RT-PCR. Genes including XYL1, XYL2, and XKS1 in the initial xylose metabolic pathway showed the highest up-regulation in SyBE005. The increased expression of XYL1 and XYL2 correlated with enhanced enzymatic activities of XR and XDH. In addition, the expression level of ZWF1 in the oxidative pentose phosphate pathway increased significantly in SyBE005, indicating an elevated demand for NADPH from XR. Genes involved in the TCA cycle (LAT1, CIT1, CIT2, KGD1, KGD, SDH2) and gluconeogenesis (ICL1, PYC1) were also up-regulated in SyBE005. Genomic analysis revealed that point mutations in transcriptional regulators CYC8 and PHD1 might be responsible for the altered expression. In addition, a mutation (Y89S) in ZWF1 was identified which might improve NADPH production in SyBE005. Our results suggest that increasing the expression of XYL1, XYL2, XKS1, and enhancing NADPH supply are promising strategies to improve xylose fermentation in recombinant S. cerevisiae.

  9. Evolutionary engineering of Saccharomyces cerevisiae for enhanced tolerance to hydrolysates of lignocellulosic biomass.

    Science.gov (United States)

    Almario, María P; Reyes, Luis H; Kao, Katy C

    2013-10-01

    Lignocellulosic biomass has become an important feedstock to mitigate current ethical and economical concerns related to the bio-based production of fuels and chemicals. During the pre-treatment and hydrolysis of the lignocellulosic biomass, a complex mixture of sugars and inhibitors are formed. The inhibitors interfere with microbial growth and product yields. This study uses an adaptive laboratory evolution method called visualizing evolution in real-time (VERT) to uncover the molecular mechanisms associated with tolerance to hydrolysates of lignocellulosic biomass in Saccharomyces cerevisiae. VERT enables a more rational scheme for isolating adaptive mutants for characterization and molecular analyses. Subsequent growth kinetic analyses of the mutants in individual and combinations of common inhibitors present in hydrolysates (acetic acid, furfural, and hydroxymethylfurfural) showed differential levels of resistance to different inhibitors, with enhanced growth rates up to 57%, 12%, 22%, and 24% in hydrolysates, acetic acid, HMF and furfural, respectively. Interestingly, some of the adaptive mutants exhibited reduced fitness in the presence of individual inhibitors, but showed enhanced fitness in the presence of combinations of inhibitors compared to the parental strains. Transcriptomic analysis revealed different mechanisms for resistance to hydrolysates and a potential cross adaptation between oxidative stress and hydrolysates tolerance in several of the mutants. PMID:23613173

  10. Co-fermentation of xylose and cellobiose by an engineered Saccharomyces cerevisiae.

    Science.gov (United States)

    Aeling, Kimberly A; Salmon, Kirsty A; Laplaza, José M; Li, Ling; Headman, Jennifer R; Hutagalung, Alex H; Picataggio, Stephen

    2012-11-01

    We have integrated and coordinately expressed in Saccharomyces cerevisiae a xylose isomerase and cellobiose phosphorylase from Ruminococcus flavefaciens that enables fermentation of glucose, xylose, and cellobiose under completely anaerobic conditions. The native xylose isomerase was active in cell-free extracts from yeast transformants containing a single integrated copy of the gene. We improved the activity of the enzyme and its affinity for xylose by modifications to the 5'-end of the gene, site-directed mutagenesis, and codon optimization. The improved enzyme, designated RfCO*, demonstrated a 4.8-fold increase in activity compared to the native xylose isomerase, with a K(m) for xylose of 66.7 mM and a specific activity of 1.41 μmol/min/mg. In comparison, the native xylose isomerase was found to have a K(m) for xylose of 117.1 mM and a specific activity of 0.29 μmol/min/mg. The coordinate over-expression of RfCO* along with cellobiose phosphorylase, cellobiose transporters, the endogenous genes GAL2 and XKS1, and disruption of the native PHO13 and GRE3 genes allowed the fermentation of glucose, xylose, and cellobiose under completely anaerobic conditions. Interestingly, this strain was unable to utilize xylose or cellobiose as a sole carbon source for growth under anaerobic conditions, thus minimizing yield loss to biomass formation and maximizing ethanol yield during their fermentation. PMID:22911235

  11. Optimization of CDT-1 and XYL1 expression for balanced co-production of ethanol and xylitol from cellobiose and xylose by engineered Saccharomyces cerevisiae.

    Directory of Open Access Journals (Sweden)

    Jian Zha

    Full Text Available Production of ethanol and xylitol from lignocellulosic hydrolysates is an alternative to the traditional production of ethanol in utilizing biomass. However, the conversion efficiency of xylose to xylitol is restricted by glucose repression, causing a low xylitol titer. To this end, we cloned genes CDT-1 (encoding a cellodextrin transporter and gh1-1 (encoding an intracellular β-glucosidase from Neurospora crassa and XYL1 (encoding a xylose reductase that converts xylose into xylitol from Scheffersomyces stipitis into Saccharomyces cerevisiae, enabling simultaneous production of ethanol and xylitol from a mixture of cellobiose and xylose (main components of lignocellulosic hydrolysates. We further optimized the expression levels of CDT-1 and XYL1 by manipulating their promoters and copy-numbers, and constructed an engineered S. cerevisiae strain (carrying one copy of PGK1p-CDT1 and two copies of TDH3p-XYL1, which showed an 85.7% increase in xylitol production from the mixture of cellobiose and xylose than that from the mixture of glucose and xylose. Thus, we achieved a balanced co-fermentation of cellobiose (0.165 g/L/h and xylose (0.162 g/L/h at similar rates to co-produce ethanol (0.36 g/g and xylitol (1.00 g/g.

  12. Strain Engineering of Transition Metal Dichalcogenides

    Science.gov (United States)

    Dadgar, Ali; Pasupathy, Abhay; Herman, Irving; Wang, Dennis; Kang, Kyungnam; Yang, Eui-Hyeok

    The application of strain to materials can cause changes to bandwidth, effective masses, degeneracies and even structural phases. In the case of the transition metal dichalcogenide (TMD) semiconductors, small strain (around 1 percent) is expected to change band gaps and mobilities, while larger strains are expected to cause phase changes from the triangular 2H phase to orthorhombic 1T' phases. We will describe experimental techniques to apply small and large (around 10 percent) strains to one or few layer samples of the TMD semiconductors, and describe the effect of the strain using optical (Raman, photoluminescence) and cryogenic transport techniques.

  13. Production of Rebaudioside A from Stevioside Catalyzed by the Engineered Saccharomyces cerevisiae.

    Science.gov (United States)

    Li, Yan; Li, Yangyang; Wang, Yu; Chen, Liangliang; Yan, Ming; Chen, Kequan; Xu, Lin; Ouyang, Pingkai

    2016-04-01

    Rebaudioside A has superior taste quality among the steviol glycosides extracted from Stevia rebaudiana leaves. Given its high purity as a general-purpose sweetener, rebaudioside A has received significant attention and has been widely applied in food and beverages in recent decades. Stevioside is one of the major steviol glycosides and can be converted to rebaudioside A by the uridine-diphosphate dependent glucosyltransferase UGT76G1 in S. rebaudiana. To explore the applicability of and limits in producing rebaudioside A from stevioside through whole-cell biocatalysis, the engineered Saccharomyces cerevisiae expressing UGT76G1, using a newly constructed constitutive expression vector, was used as the whole-cell biocatalyst. Citrate was added to the reaction mixture to allow metabolic regulation when glucose was fed to provide the activated sugar donor UDP-glucose for glycosylation of stevioside in vivo. In an evaluation of the whole-cell reaction parameters involving cell permeability, temperature, pH, citrate and Mg(2+) concentrations, and glucose feeding, production of 1160.5 mg/L rebaudioside A from 2 g/L stevioside was achieved after 48 h without supplementation of extracellular UDP-glucose. PMID:26733458

  14. Transcriptomes of a xylose-utilizing industrial flocculating Saccharomyces cerevisiae strain cultured in media containing different sugar sources.

    Science.gov (United States)

    Zeng, Wei-Yi; Tang, Yue-Qin; Gou, Min; Xia, Zi-Yuan; Kida, Kenji

    2016-12-01

    Lignocellulosic hydrolysates used for bioethanol production contain a mixture of sugars, with xylose being the second most abundant after glucose. Since xylose is not a natural substrate for Saccharomyces cerevisiae, recombinant S. cerevisiae strongly prefers glucose over xylose, and the fermentation rate and ethanol yield with xylose are both lower than those with glucose. To determine the molecular basis for glucose and xylose fermentation, we used microarrays to investigate the transcriptional difference of a xylose-utilizing industrial strain cultured in both single sugar media and a mixed sugar medium of glucose and xylose. The transcriptomes were nearly identical between glucose metabolizing cells in the glucose alone medium and those in the glucose fermentation phase in the mixed-sugar medium. Whereas the transcriptomes highly differed between the xylose metabolizing cells in the xylose alone medium and those in the xylose fermentation phase in the mixed sugar medium, and the differences mainly involved sulfur metabolism. When the transcriptional profiles were compared between glucose fermentation state and xylose fermentation state, we found the expression patterns of hexose transporters and glucose signaling pathway differed in response to different sugar sources, and the expression levels of the genes involved in gluconeogenesis, the glyoxylate and tricarboxylic acid cycles and respiration increased with xylose, indicating that the xylose-metabolizing cells had high requirements for maintenance energy and lacked the carbon catabolite repression capability. The effect of carbon catabolite repression by glucose lasted after glucose depletion for specific genes to different extents.

  15. Transcriptomes of a xylose-utilizing industrial flocculating Saccharomyces cerevisiae strain cultured in media containing different sugar sources.

    Science.gov (United States)

    Zeng, Wei-Yi; Tang, Yue-Qin; Gou, Min; Xia, Zi-Yuan; Kida, Kenji

    2016-12-01

    Lignocellulosic hydrolysates used for bioethanol production contain a mixture of sugars, with xylose being the second most abundant after glucose. Since xylose is not a natural substrate for Saccharomyces cerevisiae, recombinant S. cerevisiae strongly prefers glucose over xylose, and the fermentation rate and ethanol yield with xylose are both lower than those with glucose. To determine the molecular basis for glucose and xylose fermentation, we used microarrays to investigate the transcriptional difference of a xylose-utilizing industrial strain cultured in both single sugar media and a mixed sugar medium of glucose and xylose. The transcriptomes were nearly identical between glucose metabolizing cells in the glucose alone medium and those in the glucose fermentation phase in the mixed-sugar medium. Whereas the transcriptomes highly differed between the xylose metabolizing cells in the xylose alone medium and those in the xylose fermentation phase in the mixed sugar medium, and the differences mainly involved sulfur metabolism. When the transcriptional profiles were compared between glucose fermentation state and xylose fermentation state, we found the expression patterns of hexose transporters and glucose signaling pathway differed in response to different sugar sources, and the expression levels of the genes involved in gluconeogenesis, the glyoxylate and tricarboxylic acid cycles and respiration increased with xylose, indicating that the xylose-metabolizing cells had high requirements for maintenance energy and lacked the carbon catabolite repression capability. The effect of carbon catabolite repression by glucose lasted after glucose depletion for specific genes to different extents. PMID:27485516

  16. Growth of catalase A and catalase T deficient mutant strains of Saccharomyces cerevisiae on ethanol and oleic acid : Growth profiles and catalase activities in relation to microbody proliferation

    NARCIS (Netherlands)

    Klei, Ida J. van der; Rytka, Joanna; Kunau, Wolf H.; Veenhuis, Marten

    1990-01-01

    The parental strain (A+T+) of Saccharomyces cerevisiae and mutants, deficient in catalase T (A+T-), catalase A (A-T+) or both catalases (A-T-), grew on ethanol and oleic acid with comparable doubling times. Specific activities of catalase were low in glucose- and ethanol-grown cells. In the two olei

  17. Saccharomyces cerevisiae CCMI 885 secretes peptides that inhibit the growth of some non-Saccharomyces wine-related strains

    DEFF Research Database (Denmark)

    Albergaria, Helena; Francisco, Diana; Gori, Klaus;

    2010-01-01

    The nature of the toxic compounds produced by Saccharomyces cerevisiae CCMI 885 that induce the earlydeath of Hanseniaspora guilliermondii during mixed fermentations, as well as their ability to inhibit the growth of other non-Saccharomyces wine-related strains, was investigated. The killing effe...

  18. Improved Production of a Heterologous Amylase in Saccharomyces cerevisiae by Inverse Metabolic Engineering

    DEFF Research Database (Denmark)

    Liu, Zihe; Liu, Lifang; Osterlund, Tobias;

    2014-01-01

    engineering to identify novel targets for improving protein secretion. Screening that combined UV-random mutagenesis and selection for growth on starch was performed to find mutant strains producing heterologous amylase 5-fold above the level produced by the reference strain. Genomic mutations that could...... be associated with higher amylase secretion were identified through whole-genome sequencing. Several single-point mutations, including an S196I point mutation in the VTA1 gene coding for a protein involved in vacuolar sorting, were evaluated by introducing these to the starting strain. By applying...... this modification alone, the amylase secretion could be improved by 35%. As a complement to the identification of genomic variants, transcriptome analysis was also performed in order to understand on a global level the transcriptional changes associated with the improved amylase production caused by UV mutagenesis....

  19. [Effect of radio-frequency electromagnetic radiation on physiological features of Saccharomyces cerevisiae strain UCM Y-517].

    Science.gov (United States)

    Voĭchuk, S I; Podgorskiĭ, V S; Gromozova, E N

    2004-01-01

    Effect of electromagnetic radiation (40.68 MHz) on growth characteristics of Saccharomyces cerevisiae strain UCM Y-517 has been studied. Reliable increase of the specific growth rate (by 7-15%) and change of duration of growth phases as a result of irradiation of yeast population has been shown. The EMR effect has been found to depend on physiological state of the irradiated cells and composition of the irradiation performance medium: reliable effects were found only for the cells preliminarily grown on the dense nutrition medium in the late phase of delayed growth or on achieving the stationary growth phase. The role of radiation term and power as well as of temperature factor in EMR effect on the cells is discussed. It has been noted that the dependence of specific growth rate of yeast on the initial density of cells population acquire the nonlinear character as affected by EMR of radiofrequency range.

  20. Mitotic chromosome loss in a radiation-sensitive strain of the yeast Saccharomyces cerevisiae

    Energy Technology Data Exchange (ETDEWEB)

    Mortimer, R.K.; Contopoulou, R.; Schild, D.

    1981-09-01

    Cells of Saccharomyces cerevisiae with mutations in the RAD52 gene have previously been shown to be defective in meiotic and mitotic recombination, in sporulation, and in repair of radiation-induced damage to DNA. In this study we show that diploid cells homozygous for rad52 lose chromosomes at high frequencies and that these frequencies of loss can be increased dramatically by exposure of these cells to x-rays. Genetic analyses of survivors of x-ray treatment demonstrate that chromosome loss events result in the conversion of diploid cells to cells with near haploid chromosome numbers.

  1. Acetic acid inhibits nutrient uptake in Saccharomyces cerevisiae: auxotrophy confounds the use of yeast deletion libraries for strain improvement.

    Science.gov (United States)

    Ding, Jun; Bierma, Jan; Smith, Mark R; Poliner, Eric; Wolfe, Carole; Hadduck, Alex N; Zara, Severino; Jirikovic, Mallori; van Zee, Kari; Penner, Michael H; Patton-Vogt, Jana; Bakalinsky, Alan T

    2013-08-01

    Acetic acid inhibition of yeast fermentation has a negative impact in several industrial processes. As an initial step in the construction of a Saccharomyces cerevisiae strain with increased tolerance for acetic acid, mutations conferring resistance were identified by screening a library of deletion mutants in a multiply auxotrophic genetic background. Of the 23 identified mutations, 11 were then introduced into a prototrophic laboratory strain for further evaluation. Because none of the 11 mutations was found to increase resistance in the prototrophic strain, potential interference by the auxotrophic mutations themselves was investigated. Mutants carrying single auxotrophic mutations were constructed and found to be more sensitive to growth inhibition by acetic acid than an otherwise isogenic prototrophic strain. At a concentration of 80 mM acetic acid at pH 4.8, the initial uptake of uracil, leucine, lysine, histidine, tryptophan, phosphate, and glucose was lower in the prototrophic strain than in a non-acetic acid-treated control. These findings are consistent with two mechanisms by which nutrient uptake may be inhibited. Intracellular adenosine triphosphate (ATP) levels were severely decreased upon acetic acid treatment, which likely slowed ATP-dependent proton symport, the major form of transport in yeast for nutrients other than glucose. In addition, the expression of genes encoding some nutrient transporters was repressed by acetic acid, including HXT1 and HXT3 that encode glucose transporters that operate by facilitated diffusion. These results illustrate how commonly used genetic markers in yeast deletion libraries complicate the effort to isolate strains with increased acetic acid resistance.

  2. High Level Ethanol from Sugar Cane Molasses by a New Thermotolerant Saccharomyces cerevisiae Strain in Industrial Scale.

    Science.gov (United States)

    Fadel, M; Keera, Abeer A; Mouafi, Foukia E; Kahil, Tarek

    2013-01-01

    A new local strain of S. cerevisiae F-514, for ethanol production during hot summer season, using Egyptian sugar cane molasses was applied in Egyptian distillery factory. The inouluum was propagated through 300 L, 3 m(3), and 12 m(3) fermenters charged with diluted sugar cane molasses containing 4%-5% sugars. The yeast was applied in fermentation vessels 65 m(3) working volume to study the varying concentrations of urea, DAP, orthophosphoric acid (OPA), and its combinations as well as magnesium sulfate and inoculum size. The fermenter was allowed to stay for a period of 20 hours to give time for maximum conversion of sugars into ethanol. S. cerevisiae F-514 at molasses sugar level of 18% (w/v), inoculum size of 20% (v/v) cell concentration of 3.0 × 10(8)/mL, and combinations of urea, diammonium phosphate (DAP), orthophosphoric acid (OPA), and magnesium sulfate at amounts of 20, 10, 5, and 10 kg/65 m(3) working volume fermenters, respectively, supported maximum ethanol production (9.8%, v/v), fermentation efficiency (FE) 88.1%, and remaining sugars (RS) 1.22%. The fermentation resulted 13.4 g dry yeast/L contained 34.6% crude protein and 8.2% ash. By selecting higher ethanol yielding yeast strain and optimizing, the fermentation parameters both yield and economics of the fermentation process can be improved. PMID:24363937

  3. Growth of catalase A and catalase T deficient mutant strains of Saccharomyces cerevisiae on ethanol and oleic acid: Growth profiles and catalase activities in relation to microbody proliferation

    OpenAIRE

    van der Klei, Ida J.; Rytka, Joanna; Kunau, Wolf H.; Veenhuis, Marten

    1990-01-01

    The parental strain (A+T+) of Saccharomyces cerevisiae and mutants, deficient in catalase T (A+T-), catalase A (A-T+) or both catalases (A-T-), grew on ethanol and oleic acid with comparable doubling times. Specific activities of catalase were low in glucose- and ethanol-grown cells. In the two oleic acid-grown A+-strains (A+T+ and A+T-) high catalase activities were found; catalase activity invariably remained low in the A-T+ strain and was never detected in the A-T- strain. The levels of β-...

  4. De novo sequencing, assembly and analysis of the genome of the laboratory strain Saccharomyces cerevisiae CEN.PK113-7D, a model for modern industrial biotechnology

    NARCIS (Netherlands)

    Nijkamp, J.F.; Broek, van den M.; Datema, E.; Kok, de S.; Bosman, L.; Luttik, M.A.; Daran-Lapujade, P.; Vongsangnak, W.; Nielsen, J.; Heijne, W.H.M.; Klaassen, P.; Paddon, C.J.; Platt, D.; Kotter, P.; Ham, van R.C.H.J.; Reinders, M.J.T.; Pronk, J.T.; Ridder, de D.; Daran, J.M.

    2012-01-01

    Saccharomyces cerevisiae CEN.PK 113-7D is widely used for metabolic engineering and systems biology research in industry and academia. We sequenced, assembled, annotated and analyzed its genome. Single-nucleotide variations (SNV), insertions/deletions (indels) and differences in genome organization

  5. Novel starters for old processes: use of Saccharomyces cerevisiae strains isolated from artisanal sourdough for craft beer production at a brewery scale.

    Science.gov (United States)

    Marongiu, Antonella; Zara, Giacomo; Legras, Jean-Luc; Del Caro, Alessandra; Mascia, Ilaria; Fadda, Costantino; Budroni, Marilena

    2015-01-01

    The deliberate inoculation of yeast strains isolated from food matrices such as wine or bread, could allow the transfer of novel properties to beer. In this work, the feasibility of the use of baker's yeast strains as starters for craft beer production has been evaluated at laboratory and brewery scale. Nine out of 12 Saccharomyces cerevisiae strains isolated from artisanal sourdoughs metabolized 2 % maltose, glucose and trehalose and showed growth rates and cell populations higher than those of the brewer's strain Safbrew-S33. Analysis of allelic variation at 12 microsatellite loci clustered seven baker's strains and Safbrew-S33 in the main group of bread isolates. Chemical analyses of beers produced at a brewery scale showed significant differences among the beers produced with the baker's strain S38 or Safbrew-S33, while no significant differences were observed when S38 or the brewer's strain Safbrew-F2 was used for re-fermentation. The sensory profile of beers obtained with S38 or the brewer's yeasts did not show significant differences, thus suggesting that baker's strains of S. cerevisiae could represent a reservoir of biodiversity for the selection of starter strains for craft beer production. PMID:25387611

  6. Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Bojsen, Rasmus K; Andersen, Kaj Scherz; Regenberg, Birgitte

    2012-01-01

    to produce an ECM and respond to quorum sensing, and multi-cellular aggregates have lowered susceptibility to antifungals. Adhesion is mediated by a family of cell surface proteins of which Flo11 has been shown to be essential for biofilm development. FLO11 expression is regulated via a number of regulatory...... pathways including the protein kinase A and a mitogen-activated protein kinase pathway. Advanced genetic tools and resources have been developed for S. cerevisiae including a deletion mutant-strain collection in a biofilm-forming strain background and GFP-fusion protein collections. Furthermore, S...

  7. Benchmarking two commonly used Saccharomyces cerevisiae strains for heterologous vanillin-β-glucoside production

    DEFF Research Database (Denmark)

    Strucko, Tomas; Magdenoska, Olivera; Mortensen, Uffe Hasbro

    2015-01-01

    factories for production of specific compounds. To examine this possibility, we have reconstructed a de novo vanillin-β-glucoside pathway in an identical manner in S288c and CEN.PK strains. Characterization of the two resulting strains in two standard conditions revealed that the S288c background strain...... produced up to 10-fold higher amounts of vanillin-β-glucoside compared to CEN.PK. This study demonstrates that yeast strain background may play a major role in the outcome of newly developed cell factories for production of a given product....

  8. Whole Genome Analysis of 132 Clinical Saccharomyces cerevisiae Strains Reveals Extensive Ploidy Variation

    Science.gov (United States)

    Zhu, Yuan O.; Sherlock, Gavin; Petrov, Dmitri A.

    2016-01-01

    Budding yeast has undergone several independent transitions from commercial to clinical lifestyles. The frequency of such transitions suggests that clinical yeast strains are derived from environmentally available yeast populations, including commercial sources. However, despite their important role in adaptive evolution, the prevalence of polyploidy and aneuploidy has not been extensively analyzed in clinical strains. In this study, we have looked for patterns governing the transition to clinical invasion in the largest screen of clinical yeast isolates to date. In particular, we have focused on the hypothesis that ploidy changes have influenced adaptive processes. We sequenced 144 yeast strains, 132 of which are clinical isolates. We found pervasive large-scale genomic variation in both overall ploidy (34% of strains identified as 3n/4n) and individual chromosomal copy numbers (36% of strains identified as aneuploid). We also found evidence for the highly dynamic nature of yeast genomes, with 35 strains showing partial chromosomal copy number changes and eight strains showing multiple independent chromosomal events. Intriguingly, a lineage identified to be baker’s/commercial derived with a unique damaging mutation in NDC80 was particularly prone to polyploidy, with 83% of its members being triploid or tetraploid. Polyploidy was in turn associated with a >2× increase in aneuploidy rates as compared to other lineages. This dataset provides a rich source of information on the genomics of clinical yeast strains and highlights the potential importance of large-scale genomic copy variation in yeast adaptation. PMID:27317778

  9. Nanoscale strain engineering of graphene and graphene-based devices

    Science.gov (United States)

    Yeh, N.-C.; Hsu, C.-C.; Teague, M. L.; Wang, J.-Q.; Boyd, D. A.; Chen, C.-C.

    2016-06-01

    Structural distortions in nano-materials can induce dramatic changes in their electronic properties. This situation is well manifested in graphene, a two-dimensional honeycomb structure of carbon atoms with only one atomic layer thickness. In particular, strained graphene can result in both charging effects and pseudo-magnetic fields, so that controlled strain on a perfect graphene lattice can be tailored to yield desirable electronic properties. Here, we describe the theoretical foundation for strain-engineering of the electronic properties of graphene, and then provide experimental evidence for strain-induced pseudo-magnetic fields and charging effects in monolayer graphene. We further demonstrate the feasibility of nano-scale strain engineering for graphene-based devices by means of theoretical simulations and nano-fabrication technology.

  10. Nanoscale strain engineering of graphene and graphene-based devices

    Institute of Scientific and Technical Information of China (English)

    N-C Yeh; C-C Hsu; M L Teague; J-Q Wang; D A Boyd; C-C Chen

    2016-01-01

    Structural distortions in nano-materials can induce dramatic changes in their electronic properties. This situation is well manifested in graphene, a two-dimensional honeycomb structure of carbon atoms with only one atomic layer thickness. In particular, strained graphene can result in both charging effects and pseudo-magnetic fields, so that controlled strain on a perfect graphene lattice can be tailored to yield desirable electronic properties. Here, we describe the theoretical foundation for strain-engineering of the electronic properties of graphene, and then provide experimental evidence for strain-induced pseudo-magnetic fields and charging effects in monolayer graphene. We further demonstrate the feasibility of nano-scale strain engineering for graphene-based devices by means of theoretical simula-tions and nano-fabrication technology.

  11. Using mixed inocula of Saccharomyces cerevisiae killer strains to improve the quality of traditional sparkling-wine.

    Science.gov (United States)

    Velázquez, Rocío; Zamora, Emiliano; Álvarez, Manuel; Álvarez, María L; Ramírez, Manuel

    2016-10-01

    The quality of traditional sparkling-wine depends on the aging process in the presence of dead yeast cells. These cells undergo a slow autolysis process thereby releasing some compounds, mostly colloidal polymers such as polysaccharides and mannoproteins, which influence the wine's foam properties and mouthfeel. Saccharomyces cerevisiae killer yeasts were tested to increase cell death and autolysis during mixed-yeast-inoculated second fermentation and aging. These yeasts killed sensitive strains in killer plate assays done under conditions of low pH and temperature similar to those used in sparkling-wine making, although some strains showed a different killer behaviour during the second fermentation. The fast killer effect improved the foam quality and mouthfeel of the mixed-inoculated wines, while the slow killer effect gave small improvements over single-inoculated wines. The effect was faster under high-pressure than under low-pressure conditions. Wine quality improvement did not correlate with the polysaccharide, protein, mannan, or aromatic compound concentrations, suggesting that the mouthfeel and foaming quality of sparkling wine are very complex properties influenced by other wine compounds and their interactions, as well as probably by the specific chemical composition of a given wine. PMID:27375256

  12. Evaluation of different Saccharomyces cerevisiae strains on the profile of volatile compounds and polyphenols in cherry wines.

    Science.gov (United States)

    Sun, Shu Yang; Jiang, Wen Guang; Zhao, Yu Ping

    2011-07-15

    Tart cherries of 'Early Richmond', widely grown in Shandong (China), were fermented with six different Saccharomyces cerevisiae strains (BM4×4, RA17, RC212, D254, D21 and GRE) to elucidate their influence on the production of volatiles and polyphenols. Acetic acid and 3-methylbutanol were found in the highest concentrations among all identified volatiles with all six yeast strains, followed by 2-methylpropanol and ethyl lactate. RA17 and GRE cherry wines were characterised by a higher amount of esters and acids. D254 wine contained a higher concentration of alcohols. With respect to polyphenols, five phenolic acids and four anthocyanins were identified among all tested samples, with chlorogenic and neochlorogenic acids, cyanidin 3-glucosylrutinoside and cyanidin 3-rutinoside being the major compounds. When using principal component analysis to classify the cherry wines according to the volatiles and polyphenols, they were divided into three groups: (1) RA17 and GRE, (2) RC212 and D254 and (3) BM4×4 and D21. PMID:23140699

  13. Consolidated bioprocessing of transgenic switchgrass by an engineered and evolved Clostridium thermocellum strain

    Energy Technology Data Exchange (ETDEWEB)

    Yee, Kelsey L [ORNL; Rodriguez Jr, Miguel [ORNL; Thompson, Olivia A [ORNL; Fu, Chunxiang [Noble Foundation; Wang, Zeng-Yu [Noble Foundation; Davison, Brian H [ORNL; Mielenz, Jonathan R [ORNL

    2014-01-01

    Background: Switchgrass is an abundant and dedicated bioenergy feedstock however its inherent recalcitrance is one of the economic hurdles for producing biofuels. The down-regulation of the caffeic acid O-methyl transferase (COMT) gene in the lignin pathway of switchgrass reduced lignin content and S/G ratio, and the transgenic lines showed improved fermentation yield with S. cerevisiae and C. thermocellum (ATCC 27405) in comparison to the wild-type switchgrass. Results: Here we examine the fermentation potential of the COMT transgenic switchgrass and its wild-type line, with an engineered and evolved Clostridium thermocellum (M1570) strain. The fermentation of the transgenic switchgrass had superior conversion relative to the control line with an increase of 20% and ethanol was the primary metabolite accounting for 90% of the total metabolites measured by HPLC. Conclusions: The down-regulation of the COMT gene in switchgrass reduced recalcitrance and improved microbial bioconversion yield. Moreover, these results showed ethanol as the main fermentation metabolite produced by an engineered and evolved C. thermocellum strain grown on a transgenic switchgrass.

  14. Comparative transcriptomic analysis reveals similarities and dissimilarities in Saccharomyces cerevisiae wine strains response to nitrogen availability.

    Directory of Open Access Journals (Sweden)

    Catarina Barbosa

    Full Text Available Nitrogen levels in grape-juices are of major importance in winemaking ensuring adequate yeast growth and fermentation performance. Here we used a comparative transcriptome analysis to uncover wine yeasts responses to nitrogen availability during fermentation. Gene expression was assessed in three genetically and phenotypically divergent commercial wine strains (CEG, VL1 and QA23, under low (67 mg/L and high nitrogen (670 mg/L regimes, at three time points during fermentation (12 h, 24 h and 96 h. Two-way ANOVA analysis of each fermentation condition led to the identification of genes whose expression was dependent on strain, fermentation stage and on the interaction of both factors. The high fermenter yeast strain QA23 was more clearly distinct from the other two strains, by differential expression of genes involved in flocculation, mitochondrial functions, energy generation and protein folding and stabilization. For all strains, higher transcriptional variability due to fermentation stage was seen in the high nitrogen fermentations. A positive correlation between maximum fermentation rate and the expression of genes involved in stress response was observed. The finding of common genes correlated with both fermentation activity and nitrogen up-take underlies the role of nitrogen on yeast fermentative fitness. The comparative analysis of genes differentially expressed between both fermentation conditions at 12 h, where the main difference was the level of nitrogen available, showed the highest variability amongst strains revealing strain-specific responses. Nevertheless, we were able to identify a small set of genes whose expression profiles can quantitatively assess the common response of the yeast strains to varying nitrogen conditions. The use of three contrasting yeast strains in gene expression analysis prompts the identification of more reliable, accurate and reproducible biomarkers that will facilitate the diagnosis of deficiency of this

  15. Protein design in systems metabolic engineering for industrial strain development.

    Science.gov (United States)

    Chen, Zhen; Zeng, An-Ping

    2013-05-01

    Accelerating the process of industrial bacterial host strain development, aimed at increasing productivity, generating new bio-products or utilizing alternative feedstocks, requires the integration of complementary approaches to manipulate cellular metabolism and regulatory networks. Systems metabolic engineering extends the concept of classical metabolic engineering to the systems level by incorporating the techniques used in systems biology and synthetic biology, and offers a framework for the development of the next generation of industrial strains. As one of the most useful tools of systems metabolic engineering, protein design allows us to design and optimize cellular metabolism at a molecular level. Here, we review the current strategies of protein design for engineering cellular synthetic pathways, metabolic control systems and signaling pathways, and highlight the challenges of this subfield within the context of systems metabolic engineering.

  16. An evaluation of cellulose saccharification and fermentation with an engineered Saccharomyces cerevisiae capable of cellobiose and xylose utilization.

    Science.gov (United States)

    Fox, Jerome M; Levine, Seth E; Blanch, Harvey W; Clark, Douglas S

    2012-03-01

    Commercial-scale cellulosic ethanol production has been hindered by high costs associated with cellulose-to-glucose conversion and hexose and pentose co-fermentation. Simultaneous saccharification and fermentation (SSF) with a yeast strain capable of xylose and cellobiose co-utilization has been proposed as a possible avenue to reduce these costs. The recently developed DA24-16 strain of Saccharomyces cerevisiae incorporates a xylose assimilation pathway and a cellodextrin transporter (CDT) that permit rapid growth on xylose and cellobiose. In the current work, a mechanistic kinetic model of cellulase-catalyzed hydrolysis of cellulose was combined with a multi-substrate model of microbial growth to investigate the ability of DA24-16 and improved cellobiose-consuming strains to obviate the need for exogenously added β-glucosidase and to assess the impact of cellobiose utilization on SSF and separate hydrolysis and fermentation (SHF). Results indicate that improved CDT-containing strains capable of growing on cellobiose as rapidly as on glucose produced ethanol nearly as rapidly as non-CDT-containing yeast supplemented with β-glucosidase. In producing 75 g/L ethanol, SSF with any strain did not result in shorter residence times than SHF with a 12 h saccharification step. Strains with improved cellobiose utilization are therefore unlikely to allow higher titers to be reached more quickly in SSF than in SHF. PMID:22228702

  17. Study on the development of high yielding alcohol resistant strain of Saccharomyces cerevisiae and the Influence of Magnetic field on Saccharomyces cerevisiae Inoculum for the production of Alcohol and Vinegar from apple juice.

    Directory of Open Access Journals (Sweden)

    Rabiul Haque

    2014-12-01

    Full Text Available Natural vinegar is one of the fermented products which has some potentiality with respect to a nutraceutical standpoint. The present study is an optimization of the fermentation conditions for apple juice vinegar production from aple juice wine, this biochemical process being aided by Acetobacter aceti.We have studied on the development of high yielding alcohol resistant strain of Saccharomyces cerevisiae for the production of alcohol. Overflow metabolism is an undesirable characteristic of aerobic cultures of Saccharomyces cerevisiae during biomassdirected processes. It results from elevated apple juice containing sugar consumption rates that cause a high substrate conversion to ethanol and other bi-products, severely affecting cell physiology, bioprocess performance, and biomass yields. Fed-batch culture, where sucrose consumption rates are controlled by the external addition of sugar aiming at its low concentrations in the fermentor, is the classical bioprocessing alternative to prevent sugar fermentation by yeasts. However, fed-batch fermentations present drawbacks that could be overcome by simpler batch cultures at relatively high initial sugar concentrations From the results it is clear that strain T2. which has been exposed to 15% alcohol for 18 hrs is the high yielding strain, as it gives 16% alcohol after distillation. We also find that as the exposure is increased, that is, with increasing exposure to 20% alcohol for 5 hrs, 18 hrs, and 20 hrs, the production of alcohol decreases. Saccharomyces cerevisiae yeast cells strain T2. which has been exposed to 15% alcohol for 18 hrs were exposed to a homogenous static magnetic field of 125 mT for periods of 24, 48 or 72 hours and then used as inoculum for the alcoholic fermentation. The exposure to the magnetic field improved the fermentation process kinetics. Biomass and ethanol yields of fermentations inoculated with treated inoculum were higher than those in the control fermentation, which

  18. Strain Engineering to Modify the Electrochemistry of Energy Storage Electrodes

    Science.gov (United States)

    Muralidharan, Nitin; Carter, Rachel; Oakes, Landon; Cohn, Adam P.; Pint, Cary L.

    2016-06-01

    Strain engineering has been a critical aspect of device design in semiconductor manufacturing for the past decade, but remains relatively unexplored for other applications, such as energy storage. Using mechanical strain as an input parameter to modulate electrochemical potentials of metal oxides opens new opportunities intersecting fields of electrochemistry and mechanics. Here we demonstrate that less than 0.1% strain on a Ni-Ti-O based metal-oxide formed on superelastic shape memory NiTi alloys leads to anodic and cathodic peak potential shifts by up to ~30 mV in an electrochemical cell. Moreover, using the superelastic properties of NiTi to enable strain recovery also recovers the electrochemical potential of the metal oxide, providing mechanistic evidence of strain-modified electrochemistry. These results indicate that mechanical energy can be coupled with electrochemical systems to efficiently design and optimize a new class of strain-modulated energy storage materials.

  19. Enological characterization of Spanish Saccharomyces kudriavzevii strains, one of the closest relatives to parental strains of winemaking and brewing Saccharomyces cerevisiae × S. kudriavzevii hybrids.

    Science.gov (United States)

    Peris, D; Pérez-Través, L; Belloch, C; Querol, A

    2016-02-01

    Wine fermentation and innovation have focused mostly on Saccharomyces cerevisiae strains. However, recent studies have shown that other Saccharomyces species can also be involved in wine fermentation or are useful for wine bouquet, such as Saccharomyces uvarum and Saccharomyces paradoxus. Many interspecies hybrids have also been isolated from wine fermentation, such as S. cerevisiae × Saccharomyces kudriavzevii hybrids. In this study, we explored the genetic diversity and fermentation performance of Spanish S. kudriavzevii strains, which we compared to other S. kudriavzevii strains. Fermentations of red and white grape musts were performed, and the phenotypic differences between Spanish S. kudriavzevii strains under different temperature conditions were examined. An ANOVA analysis suggested striking similarity between strains for glycerol and ethanol production, although a high diversity of aromatic profiles among fermentations was found. The sources of these phenotypic differences are not well understood and require further investigation. Although the Spanish S. kudriavzevii strains showed desirable properties, particularly must fermentations, the quality of their wines was no better than those produced with a commercial S. cerevisiae. We suggest hybridization or directed evolution as methods to improve and innovate wine.

  20. Strain-dependent occurrence of functional GTP:AMP phosphotransferase (AK3) in Saccharomyces cerevisiae.

    Science.gov (United States)

    Schricker, R; Magdolen, V; Strobel, G; Bogengruber, E; Breitenbach, M; Bandlow, W

    1995-12-29

    The gene for yeast GTP:AMP phosphotransferase (PAK3) was found to encode a nonfunctional protein in 10 laboratory strains and one brewers' strain. The protein product showed high similarity to vertebrate AK3 and was located exclusively in the mitochondrial matrix. The deduced amino acid sequence revealed a protein that was shorter at the carboxyl terminus than all other known adenylate kinases. Introduction of a +1 frameshift into the 3'-terminal region of the gene extended homology of the deduced amino acid sequence to other members of the adenylate kinase family including vertebrate AK3. Frameshift mutations obtained after in vitro and in vivo mutagenesis were capable of complementing the adk1 temperature-conditional deficiency in Escherichia coli, indicating that the frameshift led to the expression of a protein that could phosphorylate AMP. Some yeasts, however, including strain D273-10B, two wine yeasts, and two more distantly related yeast genera, harbored an active allele, named AKY3, which contained a +1 frameshift close to the carboxyl terminus as compared with the laboratory strains. The encoded protein exhibited GTP:AMP and ITP:AMP phosphotransferase activities but did not accept ATP as phosphate donor. Although single copy in the haploid genome, disruption of the AKY3 allele displayed no phenotype, excluding the possibility that laboratory and brewers' strains had collected second site suppressors. It must be concluded that yeast mitochondria can completely dispense with GTP:AMP phosphotransferase activity.

  1. Different response to acetic acid stress in Saccharomyces cerevisiae wild-type and l-ascorbic acid-producing strains.

    Science.gov (United States)

    Martani, Francesca; Fossati, Tiziana; Posteri, Riccardo; Signori, Lorenzo; Porro, Danilo; Branduardi, Paola

    2013-09-01

    Biotechnological processes are of increasing significance for industrial production of fine and bulk chemicals, including biofuels. Unfortunately, under operative conditions microorganisms meet multiple stresses, such as non-optimal pH, temperature, oxygenation and osmotic stress. Moreover, they have to face inhibitory compounds released during the pretreatment of lignocellulosic biomasses, which constitute the preferential substrate for second-generation processes. Inhibitors include furan derivatives, phenolic compounds and weak organic acids, among which acetic acid is one of the most abundant and detrimental for cells. They impair cellular metabolism and growth, reducing the productivity of the process: therefore, the development of robust cell factories with improved production rates and resistance is of crucial importance. Here we show that a yeast strain engineered to endogenously produce vitamin C exhibits an increased tolerance compared to the parental strain when exposed to acetic acid at moderately toxic concentrations, measured as viability on plates. Starting from this evidence, we investigated more deeply: (a) the nature and levels of reactive oxygen species (ROS); (b) the activation of enzymes that act directly as detoxifiers of reactive oxygen species, such as superoxide dismutase (SOD) and catalase, in parental and engineered strains during acetic acid stress. The data indicate that the engineered strain can better recover from stress by limiting ROS accumulation, independently from SOD activation. The engineered yeast can be proposed as a model for further investigating direct and indirect mechanism(s) by which an antioxidant can rescue cells from organic acid damage; moreover, these studies will possibly provide additional targets for further strain improvements.

  2. Different response to acetic acid stress in Saccharomyces cerevisiae wild-type and l-ascorbic acid-producing strains.

    Science.gov (United States)

    Martani, Francesca; Fossati, Tiziana; Posteri, Riccardo; Signori, Lorenzo; Porro, Danilo; Branduardi, Paola

    2013-09-01

    Biotechnological processes are of increasing significance for industrial production of fine and bulk chemicals, including biofuels. Unfortunately, under operative conditions microorganisms meet multiple stresses, such as non-optimal pH, temperature, oxygenation and osmotic stress. Moreover, they have to face inhibitory compounds released during the pretreatment of lignocellulosic biomasses, which constitute the preferential substrate for second-generation processes. Inhibitors include furan derivatives, phenolic compounds and weak organic acids, among which acetic acid is one of the most abundant and detrimental for cells. They impair cellular metabolism and growth, reducing the productivity of the process: therefore, the development of robust cell factories with improved production rates and resistance is of crucial importance. Here we show that a yeast strain engineered to endogenously produce vitamin C exhibits an increased tolerance compared to the parental strain when exposed to acetic acid at moderately toxic concentrations, measured as viability on plates. Starting from this evidence, we investigated more deeply: (a) the nature and levels of reactive oxygen species (ROS); (b) the activation of enzymes that act directly as detoxifiers of reactive oxygen species, such as superoxide dismutase (SOD) and catalase, in parental and engineered strains during acetic acid stress. The data indicate that the engineered strain can better recover from stress by limiting ROS accumulation, independently from SOD activation. The engineered yeast can be proposed as a model for further investigating direct and indirect mechanism(s) by which an antioxidant can rescue cells from organic acid damage; moreover, these studies will possibly provide additional targets for further strain improvements. PMID:23847041

  3. Strain engineering in semiconducting two-dimensional crystals

    International Nuclear Information System (INIS)

    One of the fascinating properties of the new families of two-dimensional crystals is their high stretchability and the possibility to use external strain to manipulate, in a controlled manner, their optical and electronic properties. Strain engineering, understood as the field that study how the physical properties of materials can be tuned by controlling the elastic strain fields applied to it, has a perfect platform for its implementation in the atomically thin semiconducting materials. The object of this review is to give an overview of the recent progress to control the optical and electronics properties of 2D crystals, by means of strain engineering. We will concentrate on semiconducting layered materials, with especial emphasis in transition metal dichalcogenides (MoS2, WS2, MoSe2 and WSe2). The effect of strain in other atomically thin materials like black phosphorus, silicene, etc, is also considered. The benefits of strain engineering in 2D crystals for applications in nanoelectronics and optoelectronics will be revised, and the open problems in the field will be discussed. (topical review)

  4. Field performance of a genetically engineered strain of pink bollworm.

    Directory of Open Access Journals (Sweden)

    Gregory S Simmons

    Full Text Available Pest insects harm crops, livestock and human health, either directly or by acting as vectors of disease. The Sterile Insect Technique (SIT--mass-release of sterile insects to mate with, and thereby control, their wild counterparts--has been used successfully for decades to control several pest species, including pink bollworm, a lepidopteran pest of cotton. Although it has been suggested that genetic engineering of pest insects provides potential improvements, there is uncertainty regarding its impact on their field performance. Discrimination between released and wild moths caught in monitoring traps is essential for estimating wild population levels. To address concerns about the reliability of current marking methods, we developed a genetically engineered strain of pink bollworm with a heritable fluorescent marker, to improve discrimination of sterile from wild moths. Here, we report the results of field trials showing that this engineered strain performed well under field conditions. Our data show that attributes critical to SIT in the field--ability to find a mate and to initiate copulation, as well as dispersal and persistence in the release area--were comparable between the genetically engineered strain and a standard strain. To our knowledge, these represent the first open-field experiments with a genetically engineered insect. The results described here provide encouragement for the genetic control of insect pests.

  5. Ultrafast strain engineering in complex oxide heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Popovich, Paul; Caviglia, Andrea; Hu, Wanzheng; Bromberger, Hubertus; Singla, Rashmi; Mitrano, Matteo; Hoffmann, Matthias C.; Kaiser, Stefan; Foerst, Michael [Max-Planck Research Group for Structural Dynamics - Center for Free Electron Laser Science, University of Hamburg (Germany); Scherwitzl, Raoul; Zubko, Pavlo; Gariglio, Sergio; Triscone, Jean-Marc [Departement de Physique de la Matiere Condensee, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneve 4, Geneva (Switzerland); Cavalleri, Andrea [Max-Planck Research Group for Structural Dynamics - Center for Free Electron Laser Science, University of Hamburg (Germany); Department of Physics, Clarendon Laboratory, University of Oxford (United Kingdom)

    2012-07-01

    The mechanical coupling between the substrate and the thin film is expected to be effective on the ultrafast timescale, and could be exploited for the dynamic control of materials properties. Here, we demonstrate that a large-amplitude mid-infrared field, made resonant with a stretching mode of the substrate, can switch the electronic properties of a thin film across an interface. Exploiting dynamic strain propagation between different components of a heterostructure, insulating antiferromagnetic NdNiO{sub 3} is driven through a prompt, five-order-of-magnitude increase of the electrical conductivity, with resonant frequency and susceptibility that is controlled by choice of the substrate material. Vibrational phase control, extended here to a wide class of heterostructures and interfaces, may be conductive to new strategies for electronic phase control at THz repetition rates.

  6. The fraction of cells that resume growth after acetic acid addition is a strain-dependent parameter of acetic acid tolerance in Saccharomyces cerevisiae.

    Science.gov (United States)

    Swinnen, Steve; Fernández-Niño, Miguel; González-Ramos, Daniel; van Maris, Antonius J A; Nevoigt, Elke

    2014-06-01

    High acetic acid tolerance of Saccharomyces cerevisiae is a relevant phenotype in industrial biotechnology when using lignocellulosic hydrolysates as feedstock. A screening of 38 S. cerevisiae strains for tolerance to acetic acid revealed considerable differences, particularly with regard to the duration of the latency phase. To understand how this phenotype is quantitatively manifested, four strains exhibiting significant differences were studied in more detail. Our data show that the duration of the latency phase is primarily determined by the fraction of cells within the population that resume growth. Only this fraction contributed to the exponential growth observed after the latency phase, while all other cells persisted in a viable but non-proliferating state. A remarkable variation in the size of the fraction was observed among the tested strains differing by several orders of magnitude. In fact, only 11 out of 10(7)  cells of the industrial bioethanol production strain Ethanol Red resumed growth after exposure to 157 mM acetic acid at pH 4.5, while this fraction was 3.6 × 10(6) (out of 10(7)  cells) in the highly acetic acid tolerant isolate ATCC 96581. These strain-specific differences are genetically determined and represent a valuable starting point to identify genetic targets for future strain improvement.

  7. Proteins involved in wine aroma compounds metabolism by a Saccharomyces cerevisiae flor-velum yeast strain grown in two conditions.

    Science.gov (United States)

    Moreno-García, Jaime; García-Martínez, Teresa; Millán, M Carmen; Mauricio, Juan Carlos; Moreno, Juan

    2015-10-01

    A proteomic and exometabolomic study was conducted on Saccharomyces cerevisiae flor yeast strain growing under biofilm formation condition (BFC) with ethanol and glycerol as carbon sources and results were compared with those obtained under no biofilm formation condition (NBFC) containing glucose as carbon source. By using modern techniques, OFFGEL fractionator and LTQ-Orbitrap for proteome and SBSE-TD-GC-MS for metabolite analysis, we quantified 84 proteins including 33 directly involved in the metabolism of glycerol, ethanol and 17 aroma compounds. Contents in acetaldehyde, acetic acid, decanoic acid, 1,1-diethoxyethane, benzaldehyde and 2-phenethyl acetate, changed above their odor thresholds under BFC, and those of decanoic acid, ethyl octanoate, ethyl decanoate and isoamyl acetate under NBFC. Of the twenty proteins involved in the metabolism of ethanol, acetaldehyde, acetoin, 2,3-butanediol, 1,1-diethoxyethane, benzaldehyde, organic acids and ethyl esters, only Adh2p, Ald4p, Cys4p, Fas3p, Met2p and Plb1p were detected under BFC and as many Acs2p, Ald3p, Cem1p, Ilv2p, Ilv6p and Pox1p, only under NBFC. Of the eight proteins involved in glycerol metabolism, Gut2p was detected only under BFC while Pgs1p and Rhr2p were under NBFC. Finally, of the five proteins involved in the metabolism of higher alcohols, Thi3p was present under BFC, and Aro8p and Bat2p were under NBFC. PMID:26187821

  8. Proteins involved in wine aroma compounds metabolism by a Saccharomyces cerevisiae flor-velum yeast strain grown in two conditions.

    Science.gov (United States)

    Moreno-García, Jaime; García-Martínez, Teresa; Millán, M Carmen; Mauricio, Juan Carlos; Moreno, Juan

    2015-10-01

    A proteomic and exometabolomic study was conducted on Saccharomyces cerevisiae flor yeast strain growing under biofilm formation condition (BFC) with ethanol and glycerol as carbon sources and results were compared with those obtained under no biofilm formation condition (NBFC) containing glucose as carbon source. By using modern techniques, OFFGEL fractionator and LTQ-Orbitrap for proteome and SBSE-TD-GC-MS for metabolite analysis, we quantified 84 proteins including 33 directly involved in the metabolism of glycerol, ethanol and 17 aroma compounds. Contents in acetaldehyde, acetic acid, decanoic acid, 1,1-diethoxyethane, benzaldehyde and 2-phenethyl acetate, changed above their odor thresholds under BFC, and those of decanoic acid, ethyl octanoate, ethyl decanoate and isoamyl acetate under NBFC. Of the twenty proteins involved in the metabolism of ethanol, acetaldehyde, acetoin, 2,3-butanediol, 1,1-diethoxyethane, benzaldehyde, organic acids and ethyl esters, only Adh2p, Ald4p, Cys4p, Fas3p, Met2p and Plb1p were detected under BFC and as many Acs2p, Ald3p, Cem1p, Ilv2p, Ilv6p and Pox1p, only under NBFC. Of the eight proteins involved in glycerol metabolism, Gut2p was detected only under BFC while Pgs1p and Rhr2p were under NBFC. Finally, of the five proteins involved in the metabolism of higher alcohols, Thi3p was present under BFC, and Aro8p and Bat2p were under NBFC.

  9. Strain engineered barium strontium titanate for tunable thin film resonators

    Energy Technology Data Exchange (ETDEWEB)

    Khassaf, H.; Khakpash, N. [Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Sun, F. [Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States); Sbrockey, N. M.; Tompa, G. S. [Structured Materials Industries, Inc., Piscataway, New Jersey 08854 (United States); Kalkur, T. S. [Department of Electrical and Computer Engineering, University of Colorado at Colorado Springs, Colorado Springs, Colorado 80918 (United States); Alpay, S. P., E-mail: p.alpay@ims.uconn.edu [Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States)

    2014-05-19

    Piezoelectric properties of epitaxial (001) barium strontium titanate (BST) films are computed as functions of composition, misfit strain, and temperature using a non-linear thermodynamic model. Results show that through adjusting in-plane strains, a highly adaptive rhombohedral ferroelectric phase can be stabilized at room temperature with outstanding piezoelectric response exceeding those of lead based piezoceramics. Furthermore, by adjusting the composition and the in-plane misfit, an electrically tunable piezoelectric response can be obtained in the paraelectric state. These findings indicate that strain engineered BST films can be utilized in the development of electrically tunable and switchable surface and bulk acoustic wave resonators.

  10. Strain engineering of magnetic state in vacancy-doped phosphorene

    Science.gov (United States)

    Ren, Jie; Zhang, Chunxiao; Li, Jin; Guo, Zhixin; Xiao, Huaping; Zhong, Jianxin

    2016-09-01

    Inducing and manipulating the magnetism in two-dimensional materials play an important role for the development of the next-generation spintronics. In this letter, the effects of the biaxial strain on magnetic properties of vacancy-doped phosphorene are investigated using first-principles calculation. We find although only SV956 doping induces magnetism for unstrained phosphorene, the biaxial strain induces nonzero magnetic moment for SV5566 and DVa doped phosphorene. The biaxial strain also modulates the magnetic state for SV956, SV5566 and DVa doped phosphorene. The local magnetic moment derives from the spin polarization of the dangling bonds near the vacancy. The biaxial strain influences the local bonding configuration near the vacancy which determines the presence of dangling bonds, and then modulates the magnetic state. Our findings promise the synergistic effect of strain engineering and vacancy decoration is an effective method for the operation of phosphorene-based spintronic devices.

  11. Engineering of core Pentose Metabolism in Saccharomyces cerevisiae for Bio-ethanol Production

    OpenAIRE

    Pereira, Filipa Alexandra Barroso

    2013-01-01

    Tese de Doutoramento em Ciências (Especialidade em Biologia) Renewable fuels that do not contribute to atmospheric carbon dioxide have gained increased attention due to peak oil and the possibility of carbon dioxide induced climate change. Bioethanol is the currently largest biofuel in terms of annual production and is mainly produce by fermentation of hexose sugars in sucrose or starch from sugarcane or corn by the yeast Saccharomyces cerevisiae. Second generation biofuel is ...

  12. Engineering cytosolic acetyl-coenzyme A supply in Saccharomyces cerevisiae: Pathway stoichiometry, free-energy conservation and redox-cofactor balancing

    NARCIS (Netherlands)

    Van Rossum, H.M.; Kozak, B.U.; Pronk, J.T.; Van Maris, A.J.A.

    2016-01-01

    Saccharomyces cerevisiae is an important industrial cell factory and an attractive experimental model for evaluating novel metabolic engineering strategies. Many current and potential products of this yeast require acetyl coenzyme A (acetyl-CoA) as a precursor and pathways towards these products are

  13. Enhanced 3-sulfanylhexan-1-ol production in sequential mixed fermentation with Torulaspora delbrueckii/Saccharomyces cerevisiae reveals a situation of synergistic interaction between two industrial strains

    Directory of Open Access Journals (Sweden)

    Philippe eRenault

    2016-03-01

    Full Text Available The aim of this work was to study the volatile thiol productions of 2 industrial strains of Torulaspora delbrueckii and Saccharomyces cerevisiae during alcoholic fermentation (AF of Sauvignon Blanc must. In order to evaluate the influence of the inoculation procedure, sequential and simultaneous mixed cultures were carried out and compared to pure cultures of T. delbrueckii and S. cerevisiae. The results confirmed the inability of T. delbrueckii to release 4-methyl-4-sulfanylpentan-2-one (4MSP and its low capacity to produce 3-sulfanylhexyl acetate (3SHA, as already reported in previous studies. A synergistic interaction was observed between the two species, resulting in higher levels of 3SH (3-sulfanylhexan-1-ol and its acetate when S. cerevisiae was inoculated 24 hours after T. delbrueckii, compared to the pure cultures. To elucidate the nature of the interactions between these 2 species, the yeast population kinetics were examined and monitored, as well as the production of 3SH, its acetate and their related non-odorous precursors: Glut-3SH (glutathionylated conjugate precursor and Cys-3SH (cysteinylated conjugate precursor. For the first time, it was suggested that, unlike, S. cerevisiae, which is able to metabolize the two precursor forms, T. delbrueckii was only able to metabolize the glutathionylated precursor. Consequently, the presence of T. delbrueckii during mixed fermentation led to an increase in Glut-3SH degradation and Cys-3SH production. This overproduction was dependent on the T. delbrueckii biomass. In sequential culture, thus favouring T. delbrueckii development, the higher availability of Cys-3SH throughout AF (alcoholic fermentation resulted in more abundant 3SH and 3SHA production by S. cerevisiae

  14. An event-specific method for the detection and quantification of ML01, a genetically modified Saccharomyces cerevisiae wine strain, using quantitative PCR.

    Science.gov (United States)

    Vaudano, Enrico; Costantini, Antonella; Garcia-Moruno, Emilia

    2016-10-01

    The availability of genetically modified (GM) yeasts for winemaking and, in particular, transgenic strains based on the integration of genetic constructs deriving from other organisms into the genome of Saccharomyces cerevisiae, has been a reality for several years. Despite this, their use is only authorized in a few countries and limited to two strains: ML01, able to convert malic acid into lactic acid during alcoholic fermentation, and ECMo01 suitable for reducing the risk of carbamate production. In this work we propose a quali-quantitative culture-independent method for the detection of GM yeast ML01 in commercial preparations of ADY (Active Dry Yeast) consisting of efficient extraction of DNA and qPCR (quantitative PCR) analysis based on event-specific assay targeting MLC (malolactic cassette), and a taxon-specific S. cerevisiae assay detecting the MRP2 gene. The ADY DNA extraction methodology has been shown to provide good purity DNA suitable for subsequent qPCR. The MLC and MRP2 qPCR assay showed characteristics of specificity, dynamic range, limit of quantification (LOQ) limit of detection (LOD), precision and trueness, which were fully compliant with international reference guidelines. The method has been shown to reliably detect 0.005% (mass/mass) of GM ML01 S. cerevisiae in commercial preparations of ADY. PMID:27367966

  15. Alcoholic chestnut fermentation in mixed culture. Compatibility criteria between Aspergillus oryzae and Saccharomyces cerevisiae strains.

    Science.gov (United States)

    Murado, Miguel Anxo; Pastrana, Lorenzo; Vázquez, José Antonio; Mirón, Jesús; González, María Pilar

    2008-10-01

    The main objective of the present work consisted in the transfer to the case of the chestnut of a rice fermentative process that carried out to the Japanese traditional way to lead to an alcoholic bagasse, the moromi, capable of obtaining distilled. This way, selection assays of amylolitic Aspergillus oryzae strains and studies of compatibility between microfungi and yeast were carried out. These mixed cultivations were performed operating in batch submerged culture. Later on, using solid state system (chestnut, microfungi, yeast), a fermentative fed-batch process (koji, moto, moromi) was defined. By means of this approach a yield of 70% was reached in the conversion of total carbohydrates in ethanol. Also, the time required by the traditional operation was reduced in half. PMID:18289846

  16. Constraint-based strain design using continuous modifications (CosMos) of flux bounds finds new strategies for metabolic engineering.

    Science.gov (United States)

    Cotten, Cameron; Reed, Jennifer L

    2013-05-01

    In recent years, a growing number of metabolic engineering strain design techniques have employed constraint-based modeling to determine metabolic and regulatory network changes which are needed to improve chemical production. These methods use systems-level analysis of metabolism to help guide experimental efforts by identifying deletions, additions, downregulations, and upregulations of metabolic genes that will increase biological production of a desired metabolic product. In this work, we propose a new strain design method with continuous modifications (CosMos) that provides strategies for deletions, downregulations, and upregulations of fluxes that will lead to the production of the desired products. The method is conceptually simple and easy to implement, and can provide additional strategies over current approaches. We found that the method was able to find strain design strategies that required fewer modifications and had larger predicted yields than strategies from previous methods in example and genome-scale networks. Using CosMos, we identified modification strategies for producing a variety of metabolic products, compared strategies derived from Escherichia coli and Saccharomyces cerevisiae metabolic models, and examined how imperfect implementation may affect experimental outcomes. This study gives a powerful and flexible technique for strain engineering and examines some of the unexpected outcomes that may arise when strategies are implemented experimentally.

  17. Engineering related neutron diffraction measurements probing strains, texture and microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Clausen, Bjorn [Los Alamos National Laboratory; Brown, Donald W [Los Alamos National Laboratory; Tome, Carlos N [Los Alamos National Laboratory; Balogh, Levente [Los Alamos National Laboratory; Vogel, Sven C [Los Alamos National Laboratory

    2010-01-01

    Neutron diffraction has been used for engineering applications for nearly three decades. The basis of the technique is powder diffraction following Bragg's Law. From the measured diffraction patterns information about internal, or residual, strain can be deduced from the peak positions, texture information can be extracted from the peak intensities, and finally the peak widths can provide information about the microstructure, e.g. dislocation densities and grain sizes. The strains are measured directly from changes in lattice parameters, however, in many cases it is non-trivial to determine macroscopic values of stress or strain from the measured data. The effects of intergranular strains must be considered, and combining the neutron diffraction measurements with polycrystal deformation modeling has proven invaluable in determining the overall stress and strain values of interest in designing and dimensioning engineering components. Furthelmore, the combined use of measurements and modeling has provided a tool for elucidating basic material properties, such as critical resolved shear stresses for the active deformation modes and their evolution as a function of applied deformation.

  18. Origin of co-expression patterns in E. coli and S. cerevisiae emerging from reverse engineering algorithms.

    Directory of Open Access Journals (Sweden)

    Mattia Zampieri

    Full Text Available BACKGROUND: The concept of reverse engineering a gene network, i.e., of inferring a genome-wide graph of putative gene-gene interactions from compendia of high throughput microarray data has been extensively used in the last few years to deduce/integrate/validate various types of "physical" networks of interactions among genes or gene products. RESULTS: This paper gives a comprehensive overview of which of these networks emerge significantly when reverse engineering large collections of gene expression data for two model organisms, E. coli and S. cerevisiae, without any prior information. For the first organism the pattern of co-expression is shown to reflect in fine detail both the operonal structure of the DNA and the regulatory effects exerted by the gene products when co-participating in a protein complex. For the second organism we find that direct transcriptional control (e.g., transcription factor-binding site interactions has little statistical significance in comparison to the other regulatory mechanisms (such as co-sharing a protein complex, co-localization on a metabolic pathway or compartment, which are however resolved at a lower level of detail than in E. coli. CONCLUSION: The gene co-expression patterns deduced from compendia of profiling experiments tend to unveil functional categories that are mainly associated to stable bindings rather than transient interactions. The inference power of this systematic analysis is substantially reduced when passing from E. coli to S. cerevisiae. This extensive analysis provides a way to describe the different complexity between the two organisms and discusses the critical limitations affecting this type of methodologies.

  19. Saccharomyces cerevisiae strain improvement using selection, mutation, and adaptation for the resistance to lignocellulose-derived fermentation inhibitor for ethanol production.

    Science.gov (United States)

    Jang, Youri; Lim, Younghoon; Kim, Keun

    2014-05-01

    Twenty-five Saccharomyces cerevisiae strains were screened for the highest sugar tolerance, ethanol-tolerance, ethanol production, and inhibitor resistance, and S. cerevisiae KL5 was selected as the best strain. Inhibitor cocktail (100%) was composed of 75 mM formic acid, 75 mM acetic acid, 30 mM furfural, 30 mM hydroxymethyl furfural (HMF), and 2.7 mM vanillin. The cells of strain KL5 were treated with γ-irradiation, and among the survivals, KL5- G2 with improved inhibitor resistance and the highest ethanol yield in the presence of inhibitor cocktail was selected. The KL5-G2 strain was adapted to inhibitor cocktail by sequential transfer of cultures to a minimal YNB medium containing increasing concentrations of inhibitor cocktail. After 10 times of adaptation, most of the isolated colonies could grow in YNB with 80% inhibitor cocktail, whereas the parental KL5 strain could not grow at all. Among the various adapted strains, the best strain (KL5-G2-A9) producing the highest ethanol yield in the presence of inhibitor cocktail was selected. In a complex YP medium containing 60% inhibitor cocktail and 5% glucose, the theoretical yield and productivity (at 48 h) of KL5- G2-A9 were 81.3% and 0.304 g/l/h, respectively, whereas those of KL5 were 20.8% and 0.072 g/l/h, respectively. KL5-G2-A9 reduced the concentrations of HMF, furfural, and vanillin in the medium in much faster rates than KL5. PMID:24608567

  20. High temperature strain gage technology for gas turbine engines

    Science.gov (United States)

    Fichtel, Edward J.; McDaniel, Amos D.

    1994-08-01

    This report summarizes the results of a six month study that addressed specific issues to transfer the Pd-13Cr static strain sensor to a gas turbine engine environment. The application issues that were addressed include: (1) evaluation of a miniature, variable potentiometer for use as the ballast resistor, in conjunction with a conventional strain gage signal conditioning unit; (2) evaluation of a metal sheathed, platinum conductor leadwire assembly for use with the three-wire sensor; and (3) subjecting the sensor to dynamic strain cyclic testing to determine fatigue characteristics. Results indicate a useful static strain gage system at all temperature levels up to 1350 F. The fatigue characteristics also appear to be very promising, indicating a potential use in dynamic strain measurement applications. The procedure, set-up, and data for all tests are presented in this report. This report also discusses the specific strain gage installation technique for the Pd-13Cr gage because of its potential impact on the quality of the output data.

  1. The effects of dietary administration with chemical treated Saccharomyces cerevisiae strain YG3-1 on the growth of aquatic invertebrates in Artemia

    Institute of Scientific and Technical Information of China (English)

    Behnam Shekarchi; Ali Nekuiefard; Ramin Manaffar

    2016-01-01

    Objective: To investigate the biological effects of β-glucans in cell wall of new identified strain Saccharomyces cerevisiae strain YG3-1 on the growth of aquatic invertebrates, in Artemia as model organism. Methods: All yeasts used in the present study were isolated from Rainbow trout intestine and then cultured in yeast extract-peptone-glycerol medium. Activation of β-glucan in yeasts was performed by chemical treatment with 2-mercaptoethanol (2ME) (3.5% v/v). Then nauplii and larvae individuals of Artemia urmiana and Artemia franciscana (two different species of Artemia as test organisms) were fed with 2ME-treated yeasts during the culture. At the end of experiment, after feeding individual length (total length and growth rate) in adult individuals of Artemia was measured. Results: Following this administration, growth in both species of Artemia was improved (P Conclusions: This study suggested that 2ME-treated Saccharomyces cerevisiae strain YG3-1 yeasts can be used for enhancing the growth of other aquatic invertebrates like shrimps as probiotic supplement and growth promoter.

  2. The effects of dietary administration with chemical treated Saccharomyces cerevisiae strain YG3-1 on the growth of aquatic invertebrates in Artemia

    Directory of Open Access Journals (Sweden)

    Behnam Shekarchi

    2016-02-01

    Full Text Available Objective: To investigate the biological effects of β-glucans in cell wall of new identified strain Saccharomyces cerevisiae strain YG3-1 on the growth of aquatic invertebrates, in Artemia as model organism. Methods: All yeasts used in the present study were isolated from Rainbow trout intestine and then cultured in yeast extract-peptone-glycerol medium. Activation of β-glucan in yeasts was performed by chemical treatment with 2-mercaptoethanol (2ME (3.5% v/v. Then nauplii and larvae individuals of Artemia urmiana and Artemia franciscana (two different species of Artemia as test organisms were fed with 2ME-treated yeasts during the culture. At the end of experiment, after feeding individual length (total length and growth rate in adult individuals of Artemia was measured. Results: Following this administration, growth in both species of Artemia was improved (P < 0.05. So, the results showed that Artemia urmiana adults individuals that fed with 2MEtreated yeasts had the highest growth and total length. These results were confirmed with growth measurement in adult individuals of Artemia. Conclusions: This study suggested that 2ME-treated Saccharomyces cerevisiae strain YG3-1 yeasts can be used for enhancing the growth of other aquatic invertebrates like shrimps as probiotic supplement and growth promoter.

  3. Whole genome sequencing of Saccharomyces cerevisiae: from genotype to phenotype for improved metabolic engineering applications

    DEFF Research Database (Denmark)

    Otero, José Manuel; Vongsangnak, Wanwipa; Asadollahi, Mohammadali;

    2010-01-01

    BACKGROUND: The need for rapid and efficient microbial cell factory design and construction are possible through the enabling technology, metabolic engineering, which is now being facilitated by systems biology approaches. Metabolic engineering is often complimented by directed evolution, where...

  4. Differential Azole Antifungal Efficacies Contrasted Using a Saccharomyces cerevisiae Strain Humanized for Sterol 14α-Demethylase at the Homologous Locus▿

    OpenAIRE

    Parker, J. E.; Merkamm, M.; Manning, N J; Pompon, D; Kelly, S. L.; Kelly, D. E.

    2008-01-01

    Inhibition of sterol-14α-demethylase, a cytochrome P450 (CYP51, Erg11p), is the mode of action of azole antifungal drugs, and with high frequencies of fungal infections new agents are required. New drugs that target fungal CYP51 should not inhibit human CYP51, although selective inhibitors of the human target are also of interest as anticholesterol agents. A strain of Saccharomyces cerevisiae that was humanized with respect to the amino acids encoded at the CYP51 (ERG11) yeast locus (BY4741:h...

  5. Changes and roles of membrane compositions in the adaptation of Saccharomyces cerevisiae to ethanol.

    Science.gov (United States)

    Wang, Yanfeng; Zhang, Shuxian; Liu, Huaqing; Zhang, Lei; Yi, Chenfeng; Li, Hao

    2015-12-01

    Bioethanol fermentation by Saccharomyces cerevisiae is often stressed by the accumulation of ethanol. Cell membrane is the first assaulting target of ethanol. Ethanol-adapted S. cerevisiae strains provide opportunity to shed light on membrane functions in the ethanol tolerance. This study aimed at clarifying the roles of cell membrane in the ethanol tolerance of S. cerevisiae through comparing membrane components between S. cerevisiae parental strain and ethanol-adapted strains. A directed evolutionary engineering was performed to obtain the ethanol-adapted S. cerevisiae strains. The parental, ethanol-adapted M5 and M10 strains were selected to be compared the percentage of viable cells after exposing to ethanol stress and cell membrane compositions (i.e., ergosterol, trehalose, and fatty acids). Compared with the parental strain, M5 or M10 strain had higher survival rate in the presence of 10% v/v ethanol. Compared with that in the parental strain, contents of trehalose, ergosterol, and fatty acids increased about 15.7, 12.1, and 29.3%, respectively, in M5 strain, and about 47.5, 107.8, and 61.5%, respectively, in M10 strain. Moreover, expression differences of genes involved in fatty acids metabolisms among the parental, M5 and M10 strains were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR), and results demonstrated that M5 or M10 strain had higher expression of ACC1 and OLE1 than the parental strain. These results indicated that although being exposed to step-wise increased ethanol, S. cerevisiae cells might remodel membrane components or structure to adapt to the ethanol stress.

  6. Anaerobic and sequential aerobic production of high-titer ethanol and single cell protein from NaOH-pretreated corn stover by a genome shuffling-modified Saccharomyces cerevisiae strain.

    Science.gov (United States)

    Ren, Xueliang; Wang, Juncong; Yu, Hui; Peng, Chunlan; Hu, Jinlong; Ruan, Zhiyong; Zhao, Shumiao; Liang, Yunxiang; Peng, Nan

    2016-10-01

    In this study, a Saccharomyces cerevisiae recombinant strain 14 was constructed through genome shuffling method by transferring the whole genomic DNA of Candida intermedia strain 23 into a thermo-tolerant S. cerevisiae strain. The recombinant strain 14 combined the good natures of both parent strains that efficiently produced ethanol from glucose and single cell protein from xylose with 54.6% crude protein and all essential amino acids except cysteine at 35°C. Importantly, the recombinant strain 14 produced 64.07g/L ethanol from 25%(w/v) NaOH-pretreated and washed corn stover with the ethanol yield of 0.26g/g total stover by fed-batch simultaneous saccharification and fermentation and produced 66.50g/L dry cell mass subsequently from the residual hydrolysate and ethanol. Therefore, this study represents a feasible method to comprehensively utilize hexose and pentose in lignocellulosic materials. PMID:27416512

  7. Strain engineered high reflectivity DBRs in the deep UV

    Science.gov (United States)

    Franke, A.; Hoffmann, M. P.; Hernandez-Balderrama, L.; Kaess, F.; Bryan, I.; Washiyama, S.; Bobea, M.; Tweedie, J.; Kirste, R.; Gerhold, M.; Collazo, R.; Sitar, Z.

    2016-02-01

    The maximum achievable reflectivity of current III-nitride Bragg reflectors in the UV-C spectral range is limited due to plastic relaxation of thick multilayer structures. Cracking due to a large mismatch of the thermal expansion and lattice constants between AlxGa1-xN/AlyGa1-yN alloys of different composition and the substrate at the heterointerface is the common failure mode. Strain engineering and strain relaxation concepts by the growth on a strain reduced Al0.85Ga0.15N template and the implementation of low temperature interlayers is demonstrated. A significant enhancement of the maximum reflectivity above 97% at a resonance wavelength of 270 nm due to an increase of the critical thickness of our AlN/Al0.65Ga0.35N DBRs to 1.45 μm (25.5 pairs) prove their potential. By comparing the growth of identical Bragg reflectors on different pseudo-templates, the accumulated mismatch strain energy in the DBR, not the dislocation density provided by the template/substrate, was identified to limit the critical thickness. To further enhance the reflectivity low temperature interlays were implemented into the DBR to partially relief the misfit strain. Relaxation is enabled by the nucleation of small surface domains facilitating misfit dislocation injection and glide. Detailed structural and optical investigations will be conducted to prove the influence of the LT-AlN interlayers on the strain state, structural integrity and reflectivity properties. Coherent growth and no structural and optical degradation of the Bragg mirror properties was observed proving the fully applicability of the relaxation concept to fabricate thick high reflectivity DBR and vertical cavity laser structures.

  8. Crystallization engineering as a route to epitaxial strain control

    Energy Technology Data Exchange (ETDEWEB)

    Akbashev, Andrew R.; Plokhikh, Aleksandr V.; Barbash, Dmitri [Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States); Lofland, Samuel E. [Department of Physics, Rowan University, Glassboro, New Jersey 08028 (United States); Spanier, Jonathan E., E-mail: spanier@drexel.edu [Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States); Department of Physics, Drexel University, Philadelphia, Pennsylvania 19104 (United States)

    2015-10-01

    The controlled synthesis of epitaxial thin films offers opportunities for tuning their functional properties via enabling or suppressing strain relaxation. Examining differences in the epitaxial crystallization of amorphous oxide films, we report on an alternate, low-temperature route for strain engineering. Thin films of amorphous Bi–Fe–O were grown on (001)SrTiO{sub 3} and (001)LaAlO{sub 3} substrates via atomic layer deposition. In situ X-ray diffraction and X-ray photoelectron spectroscopy studies of the crystallization of the amorphous films into the epitaxial (001)BiFeO{sub 3} phase reveal distinct evolution profiles of crystallinity with temperature. While growth on (001)SrTiO{sub 3} results in a coherently strained film, the same films obtained on (001)LaAlO{sub 3} showed an unstrained, dislocation-rich interface, with an even lower temperature onset of the perovskite phase crystallization than in the case of (001)SrTiO{sub 3}. Our results demonstrate how the strain control in an epitaxial film can be accomplished via its crystallization from the amorphous state.

  9. Crystallization engineering as a route to epitaxial strain control

    Directory of Open Access Journals (Sweden)

    Andrew R. Akbashev

    2015-10-01

    Full Text Available The controlled synthesis of epitaxial thin films offers opportunities for tuning their functional properties via enabling or suppressing strain relaxation. Examining differences in the epitaxial crystallization of amorphous oxide films, we report on an alternate, low-temperature route for strain engineering. Thin films of amorphous Bi–Fe–O were grown on (001SrTiO3 and (001LaAlO3 substrates via atomic layer deposition. In situ X-ray diffraction and X-ray photoelectron spectroscopy studies of the crystallization of the amorphous films into the epitaxial (001BiFeO3 phase reveal distinct evolution profiles of crystallinity with temperature. While growth on (001SrTiO3 results in a coherently strained film, the same films obtained on (001LaAlO3 showed an unstrained, dislocation-rich interface, with an even lower temperature onset of the perovskite phase crystallization than in the case of (001SrTiO3. Our results demonstrate how the strain control in an epitaxial film can be accomplished via its crystallization from the amorphous state.

  10. Engineering Saccharomyces cerevisiae to produce odd chain-length fatty alcohols.

    Science.gov (United States)

    Jin, Zhu; Wong, Adison; Foo, Jee Loon; Ng, Joey; Cao, Ying-Xiu; Chang, Matthew Wook; Yuan, Ying-Jin

    2016-04-01

    Fatty aldehydes and alcohols are valuable precursors used in the industrial manufacturing of a myriad of specialty products. Herein, we demonstrate the de novo production of odd chain-length fatty aldehydes and fatty alcohols in Saccharomyces cerevisiae by expressing a novel biosynthetic pathway involving cytosolic thioesterase, rice α-dioxygenase and endogenous aldehyde reductases. We attained production titers of ∼20 mg/l fatty aldehydes and ∼20 mg/l fatty alcohols in shake flask cultures after 48 and 60 h respectively without extensive fine-tuning of metabolic fluxes. In contrast to prior studies which relied on bi-functional fatty acyl-CoA reductase to produce even chain-length fatty alcohols, our biosynthetic route exploits α-oxidation reaction to produce odd chain-length fatty aldehyde intermediates without using NAD(P)H cofactor, thereby conserving cellular resource during the overall synthesis of odd chain-length fatty alcohols. The biosynthetic pathway presented in this study has the potential to enable sustainable and efficient synthesis of fatty acid-derived chemicals from processed biomass. PMID:26461930

  11. Bio-Engineering High Performance Microbial Strains for MEOR

    Energy Technology Data Exchange (ETDEWEB)

    Xiangdong Fang; Qinghong Wang; Patrick Shuler

    2007-12-30

    The main objectives of this three-year research project are: (1) to employ the latest advances in genetics and bioengineering, especially Directed Protein Evolution technology, to improve the effectiveness of the microbial enhanced oil recovery (MEOR) process. (2) to improve the surfactant activity and the thermal stability of bio-surfactant systems for MEOR; and (3) to develop improved laboratory methods and tools that screen quickly candidate bio-systems for EOR. Biosurfactants have been receiving increasing attention as Enhanced Oil Recovery (EOR) agents because of their unique properties (i.e., mild production conditions, lower toxicity, and higher biodegradability) compared to their synthetic chemical counterparts. Rhamnolipid as a potent natural biosurfactant has a wide range of potential applications, including EOR and bioremediation. During the three-year of the project period, we have successfully cloned the genes involved in the rhamnolipid bio-synthesis. And by using the Transposon containing Rhamnosyltransferase gene rhlAB, we engineered the new mutant strains P. aeruginosa PEER02 and E. coli TnERAB so they can produce rhamnolipid biosurfactans. We were able to produce rhamnolipds in both P. aeroginosa PAO1-RhlA- strain and P. fluorescens ATCC15453 strain, with the increase of 55 to 175 fold in rhamnolipid production comparing with wild type bacteria strain. We have also completed the first round direct evolution studies using Error-prone PCR technique and have constructed the library of RhlAB-containing Transposon to express mutant gene in heterologous hosts. Several methods, such as colorimetric agar plate assay, colorimetric spectrophotometer assay, bioactive assay and oil spreading assay have been established to detect and screen rhamnolipid production. Our engineered P. aeruginosa PEER02 strain can produce rhamnolipids with different carbon sources as substrate. Interfacial tension analysis (IFT) showed that different rhamnolipids from different

  12. Strain-engineered manufacturing of freeform carbon nanotube microstructures

    Science.gov (United States)

    de Volder, M.; Park, S.; Tawfick, S.; Hart, A. J.

    2014-07-01

    The skins of many plants and animals have intricate microscale surface features that give rise to properties such as directed water repellency and adhesion, camouflage, and resistance to fouling. However, engineered mimicry of these designs has been restrained by the limited capabilities of top-down fabrication processes. Here we demonstrate a new technique for scalable manufacturing of freeform microstructures via strain-engineered growth of aligned carbon nanotubes (CNTs). Offset patterning of the CNT growth catalyst is used to locally modulate the CNT growth rate. This causes the CNTs to collectively bend during growth, with exceptional uniformity over large areas. The final shape of the curved CNT microstructures can be designed via finite element modeling, and compound catalyst shapes produce microstructures with multidirectional curvature and unusual self-organized patterns. Conformal coating of the CNTs enables tuning of the mechanical properties independently from the microstructure geometry, representing a versatile principle for design and manufacturing of complex microstructured surfaces.

  13. Enhancement of Farnesyl Diphosphate Pool as Direct Precursor of Sesquiterpenes Through Metabolic Engineering of the Mevalonate Pathway in Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Asadollahi, Mohammadali; Maury, Jerome; Schalk, M.;

    2010-01-01

    , resulted in higher production of cubebol, a plant originating sesquiterpene, and increased squalene accumulation. Down-regulation of ERG9 by replacing its native promoter with the regulatable MET3 promoter, enhanced cubebol titers but simultaneous overexpression of tHMG1 and repression of ERG9 did not...... further improve cubebol production. Furtheremore, the concentrations of squalene and ergosterol were measured in the engineered strains. Unexpectedly, significant accumulation of squalene and restoring the ergosterol biosynthesis were observed in the ERG9 repressed strains transformed with the plasmids...

  14. An engineered cryptic Hxt11 sugar transporter facilitates glucose-xylose co-consumption in Saccharomyces cerevisiae

    NARCIS (Netherlands)

    Shin, Hyun Yong; Nijland, Jeroen G; de Waal, Paul P; de Jong, René M; Klaassen, Paul; Driessen, Arnold J M

    2015-01-01

    BACKGROUND: The yeast Saccharomyces cerevisiae is unable to ferment pentose sugars like d-xylose. Through the introduction of the respective metabolic pathway, S. cerevisiae is able to ferment xylose but first utilizes d-glucose before the d-xylose can be transported and metabolized. Low affinity d-

  15. Mutation Breeding of Salt-tolerant and Ethanol-producing Strain S. cerevisiae H058 by Low-energy Ion Implantation

    Directory of Open Access Journals (Sweden)

    Shoubao Yan

    2014-07-01

    Full Text Available To obtain an industrial strain with high ethanol fermentation efficiency under salted conditions, the wild strain H058 of Saccharomyces cerevisiae was mutated by means of nitrogen ions implantation. Mutagenic effects of strain H058 by low energy N+ ion implantation were studied. A similar “saddle shape” survival curve due to ion beam irradiation appeared again in this study. By repeated screening, a high salt-tolerant and ethanol-producing strain M158 was obtained. Results showed that in medium contained 0, 1.5, 3.0, 4.5, 6.0% NaCl, M158 produced maximal ethanol of 98.3, 97.2, 96.4, 95.6 and 78.3 g/L at 54, 54, 54 and 72 h, respectively. However, the original strain H058 maximal ethanol of 95.2, 90.9, 84.8, 79.4 and 67.5 g/L at 60, 60, 66 and 72 h, respectively. In addition, the ethanol yield (g/g in all of the NaCl concentrations for M158 is 0.492, 0.486, 0.482, 0.48 and 0.392 g/g, respectively, which were higher than those (0.476, 0.455, 0.424, 0.397 and 0.338 g/g, respectively of the original strain H058. The higher production and shorter fermentation period suggest that strain M158 is a good salt-tolerant and ethanol-producing strain.

  16. Increasing cell biomass in Saccharomyces cerevisiae increases recombinant protein yield: the use of a respiratory strain as a microbial cell factory

    Directory of Open Access Journals (Sweden)

    Hedfalk Kristina

    2010-06-01

    Full Text Available Abstract Background Recombinant protein production is universally employed as a solution to obtain the milligram to gram quantities of a given protein required for applications as diverse as structural genomics and biopharmaceutical manufacture. Yeast is a well-established recombinant host cell for these purposes. In this study we wanted to investigate whether our respiratory Saccharomyces cerevisiae strain, TM6*, could be used to enhance the productivity of recombinant proteins over that obtained from corresponding wild type, respiro-fermentative strains when cultured under the same laboratory conditions. Results Here we demonstrate at least a doubling in productivity over wild-type strains for three recombinant membrane proteins and one recombinant soluble protein produced in TM6* cells. In all cases, this was attributed to the improved biomass properties of the strain. The yield profile across the growth curve was also more stable than in a wild-type strain, and was not further improved by lowering culture temperatures. This has the added benefit that improved yields can be attained rapidly at the yeast's optimal growth conditions. Importantly, improved productivity could not be reproduced in wild-type strains by culturing them under glucose fed-batch conditions: despite having achieved very similar biomass yields to those achieved by TM6* cultures, the total volumetric yields were not concomitantly increased. Furthermore, the productivity of TM6* was unaffected by growing cultures in the presence of ethanol. These findings support the unique properties of TM6* as a microbial cell factory. Conclusions The accumulation of biomass in yeast cell factories is not necessarily correlated with a proportional increase in the functional yield of the recombinant protein being produced. The respiratory S. cerevisiae strain reported here is therefore a useful addition to the matrix of production hosts currently available as its improved biomass

  17. Identification of yeasts isolated from raffia wine (Raphia hookeri) produced in Côte d'Ivoire and genotyping of Saccharomyces cerevisiae strains by PCR inter-delta.

    Science.gov (United States)

    Tra Bi, Charles Y; N'guessan, Florent K; Kouakou, Clémentine A; Jacques, Noemie; Casaregola, Serge; Djè, Marcellin K

    2016-08-01

    Raffia wine is a traditional alcoholic beverage produced in several African countries where it plays a significant role in traditional customs and population diet. Alcoholic fermentation of this beverage is ensured by a complex natural yeast flora which plays a decisive role in the quality of the final product. This present study aims to evaluate the distribution and the diversity of the yeast strains isolated in raffia wine from four sampling areas (Abengourou, Alépé, Grand-Lahou and Adzopé) in Côte d'Ivoire. Based on the D1/D2 domain of the LSU rDNA sequence analysis, nine species belonging to six genera were distinguished. With a percentage of 69.5 % out of 171 yeast isolates, Saccharomyces cerevisiae was the predominant species in the raffia wine, followed by Kodamaea ohmeri (20.4 %). The other species isolated were Candida haemulonii (4.1 %), Candida phangngensis (1.8 %), Pichia kudriavzevii (1.2 %), Hanseniaspora jakobsenii (1.2 %), Candida silvae (0.6 %), Hanseniaspora guilliermondii (0.6 %) and Meyerozyma caribbica (0.6 %). The molecular characterization of S. cerevisiae isolates at the strain level using the PCR-interdelta method revealed the presence of 21 profiles (named I to XXI) within 115 isolates. Only four profiles (I, III, V and XI) were shared by the four areas under study. Phenotypic characterization of K. ohmeri strains showed two subgroups for sugar fermentation and no diversity for the nitrogen compound assimilations and the growth at different temperatures. PMID:27339306

  18. Metabolic opportunities offered by wild-type and engineered Saccharomyces cerevisiae strains for biofuels production

    OpenAIRE

    Rossi,, A.

    2011-01-01

    Human society has always been dependent on biomass-derived carbonand energy for nutrition and survival. Recently, we have also become dependent on petroleum-derived carbon and energy for commodity chemicals and fuels. However, the nonrenewable nature of petroleum stands in stark contrast to the renewable carbon and energy present in biomass. Thus, there is an increasing demand to develop and implement strategies for production of commodity chemicals and fuels from biomass instead of petroleum...

  19. Fermentation performance of engineered and evolved xylose-fermenting Saccharomyces cerevisiae strains

    DEFF Research Database (Denmark)

    Sonderegger, M.; Jeppsson, M.; Larsson, C.;

    2004-01-01

    Lignocellulose hydrolysate is an abundant substrate for bioethanol production. The ideal microorganism for such a fermentation process should combine rapid and efficient conversion of the available carbon sources to ethanol with high tolerance to ethanol and to inhibitory components in the hydrol...

  20. Metabolic engineering of free-energy (ATP) conserving reactions in Saccharomyces cerevisiae

    NARCIS (Netherlands)

    De Kok, S.

    2012-01-01

    Metabolic engineering – the improvement of cellular activities by manipulation of enzymatic, transport and regulatory functions of the cell – has enabled the industrial production of a wide variety of biological molecules from renewable resources. Microbial production of fuels and chemicals thereby

  1. Engineering precursor supply in Saccharomyces cerevisiae: new strategies for cytosolic acetyl-CoA formation

    NARCIS (Netherlands)

    Kozak, B.U.

    2015-01-01

    Metabolic engineering – the improvement and addition, by genetic modification, of industrially relevant properties of microorganisms with respect to catalysis, transport and regulatory functions – is a well-established method for development of more cost-effective and ‘green’ industrial processes. R

  2. Evaluation of microbial qPCR workflows using engineered Saccharomyces cerevisiae

    Directory of Open Access Journals (Sweden)

    S.M. Da Silva

    2016-03-01

    Significance and impact of the study: The engineered yeast has potential to support measurement assurance for the analytical process of qPCR, encompassing the method, equipment, and operator, to increase confidence in results and better inform decision-making in areas of applied microbiology. This material can also support process assessment for other DNA-based detection technologies.

  3. Metabolic Engineering of Saccharomyces cerevisiae for Conversion of d-Glucose to Xylitol and Other Five-Carbon Sugars and Sugar Alcohols▿

    Science.gov (United States)

    Toivari, Mervi H.; Ruohonen, Laura; Miasnikov, Andrei N.; Richard, Peter; Penttilä, Merja

    2007-01-01

    Recombinant Saccharomyces cerevisiae strains that produce the sugar alcohols xylitol and ribitol and the pentose sugar d-ribose from d-glucose in a single fermentation step are described. A transketolase-deficient S. cerevisiae strain accumulated d-xylulose 5-phosphate intracellularly and released ribitol and pentose sugars (d-ribose, d-ribulose, and d-xylulose) into the growth medium. Expression of the xylitol dehydrogenase-encoding gene XYL2 of Pichia stipitis in the transketolase-deficient strain resulted in an 8.5-fold enhancement of the total amount of the excreted sugar alcohols ribitol and xylitol. The additional introduction of the 2-deoxy-glucose 6-phosphate phosphatase-encoding gene DOG1 into the transketolase-deficient strain expressing the XYL2 gene resulted in a further 1.6-fold increase in ribitol production. Finally, deletion of the endogenous xylulokinase-encoding gene XKS1 was necessary to increase the amount of xylitol to 50% of the 5-carbon sugar alcohols excreted. PMID:17630301

  4. Systematic strain construction and process development: Xylitol production by Saccharomyces cerevisiae expressing Candida tenuis xylose reductase in wild-type or mutant form.

    Science.gov (United States)

    Pratter, S M; Eixelsberger, T; Nidetzky, B

    2015-12-01

    A novel Saccharomyces cerevisiae whole-cell biocatalyst for xylitol production based on Candida tenuis xylose reductase (CtXR) is presented. Six recombinant strains expressing wild-type CtXR or an NADH-specific mutant were constructed and evaluated regarding effects of expression mode, promoter strength, biocatalyst concentration and medium composition. Intracellular XR activities ranged from 0.09 U mgProt(-1) to 1.05 U mgProt(-1) but did not correlate with the strains' xylitol productivities, indicating that other factors limited xylose conversion in the high-activity strains. The CtXR mutant decreased the biocatalyst's performance, suggesting use of the NADPH-preferring wild-type enzyme when (semi-)aerobic conditions are applied. In a bioreactor process, the best-performing strain converted 40 g L(-1) xylose with an initial productivity of 1.16 g L(-1)h(-1) and a xylitol yield of 100%. The obtained results underline the potential of CtXR wild-type for xylose reduction and point out parameters to improve "green" xylitol production. PMID:26452180

  5. Directed evolution of a cellobiose utilization pathway in Saccharomyces cerevisiae by simultaneously engineering multiple proteins

    OpenAIRE

    Eriksen, Dawn T.; Hsieh, Pei Chiun Helen; Lynn, Patrick; Zhao, Huimin

    2013-01-01

    Background The optimization of metabolic pathways is critical for efficient and economical production of biofuels and specialty chemicals. One such significant pathway is the cellobiose utilization pathway, identified as a promising route in biomass utilization. Here we describe the optimization of cellobiose consumption and ethanol productivity by simultaneously engineering both proteins of the pathway, the β-glucosidase (gh1-1) and the cellodextrin transporter (cdt-1), in an example of path...

  6. Coordinated transcription factor and promoter engineering to establish strong expression elements in Saccharomyces cerevisiae.

    Science.gov (United States)

    Leavitt, John M; Tong, Alice; Tong, Joyce; Pattie, Jonathan; Alper, Hal S

    2016-07-01

    Gene expression requires the coordination of trans-acting factors and cis-DNA elements to initiate transcription. Here we present a coordinated approach that combines cis-acting element engineering with mutant trans-acting factors to engineer yeast promoters. Specifically, we first construct a hybrid promoter based on the ARO9 upstream region that exhibits high constitutive and inducible expression with respect to exogenous tryptophan. Next, we perform protein engineering to identify a mutant Aro80p that affords both high constitutive expression while retaining inducible traits. We then use this mutant trans-acting factor to drive expression and generate ultra-strong promoters with transcriptional output roughly 2 fold higher than TDH3 (GPD), one of the strongest promoters to-date. Finally, we used this element to construct a modular expression system capable of staged outputs resulting in a system with nearly 6-fold, 12-fold and 15-fold expression relative to the off-state. This work further highlights the potential of using endogenous transcription factors (including mutant factors) along with hybrid promoters to expand the yeast synthetic biology toolbox. PMID:27152757

  7. Switching the mode of sucrose utilization by Saccharomyces cerevisiae

    Directory of Open Access Journals (Sweden)

    Miletti Luiz C

    2008-02-01

    Full Text Available Abstract Background Overflow metabolism is an undesirable characteristic of aerobic cultures of Saccharomyces cerevisiae during biomass-directed processes. It results from elevated sugar consumption rates that cause a high substrate conversion to ethanol and other bi-products, severely affecting cell physiology, bioprocess performance, and biomass yields. Fed-batch culture, where sucrose consumption rates are controlled by the external addition of sugar aiming at its low concentrations in the fermentor, is the classical bioprocessing alternative to prevent sugar fermentation by yeasts. However, fed-batch fermentations present drawbacks that could be overcome by simpler batch cultures at relatively high (e.g. 20 g/L initial sugar concentrations. In this study, a S. cerevisiae strain lacking invertase activity was engineered to transport sucrose into the cells through a low-affinity and low-capacity sucrose-H+ symport activity, and the growth kinetics and biomass yields on sucrose analyzed using simple batch cultures. Results We have deleted from the genome of a S. cerevisiae strain lacking invertase the high-affinity sucrose-H+ symporter encoded by the AGT1 gene. This strain could still grow efficiently on sucrose due to a low-affinity and low-capacity sucrose-H+ symport activity mediated by the MALx1 maltose permeases, and its further intracellular hydrolysis by cytoplasmic maltases. Although sucrose consumption by this engineered yeast strain was slower than with the parental yeast strain, the cells grew efficiently on sucrose due to an increased respiration of the carbon source. Consequently, this engineered yeast strain produced less ethanol and 1.5 to 2 times more biomass when cultivated in simple batch mode using 20 g/L sucrose as the carbon source. Conclusion Higher cell densities during batch cultures on 20 g/L sucrose were achieved by using a S. cerevisiae strain engineered in the sucrose uptake system. Such result was accomplished by

  8. Construction of an environmental safe Bacillus thuringiensis engineered strain against Coleoptera.

    Science.gov (United States)

    Yu, Yajun; Yuan, Yihui; Gao, Meiying

    2016-05-01

    Cloning of new toxic genes from Bacillus thuringiensis (Bt) and construction of Bt engineered strains are two key strategies for bio-control of coleopteran pests in agriculture and forestry. In this study, we cloned a new cry3Aa-type gene, cry3Aa8, from wild Bt strain YC-03 against coleopteran, and constructed a Bt engineered strain, ACE-38, containing insecticidal protein-encoding gene cry3Aa8. The engineered strain, with almost four times of Cry3Aa yield compared with strain YC-03, was an antibiotic marker-free strain. Though no selective pressure was presented in the medium, cry3Aa8 in the engineered strain ACE-38 remained stable. The yield of Cry3Aa by strain ACE-38 reached 2.09 mg/ml in the optimized fermentation medium. The activity of strain ACE-38 against Plagiodera versicolora was tested, and the LC50 of ACE-38 cultures in the optimized fermentation medium was 1.13 μl/ml. Strain ACE-38 is a non-antibiotic Bt engineered strain with high Chrysomelidae toxicity and exhibits good fermentation property. The modified indigenous site-specific recombination system constructed in this study might be useful for the construction of Bt engineered strains containing genes that cannot be expressed in the indigenous site-specific recombination system using plasmid pBMB1205R. PMID:26767987

  9. Construction of an environmental safe Bacillus thuringiensis engineered strain against Coleoptera.

    Science.gov (United States)

    Yu, Yajun; Yuan, Yihui; Gao, Meiying

    2016-05-01

    Cloning of new toxic genes from Bacillus thuringiensis (Bt) and construction of Bt engineered strains are two key strategies for bio-control of coleopteran pests in agriculture and forestry. In this study, we cloned a new cry3Aa-type gene, cry3Aa8, from wild Bt strain YC-03 against coleopteran, and constructed a Bt engineered strain, ACE-38, containing insecticidal protein-encoding gene cry3Aa8. The engineered strain, with almost four times of Cry3Aa yield compared with strain YC-03, was an antibiotic marker-free strain. Though no selective pressure was presented in the medium, cry3Aa8 in the engineered strain ACE-38 remained stable. The yield of Cry3Aa by strain ACE-38 reached 2.09 mg/ml in the optimized fermentation medium. The activity of strain ACE-38 against Plagiodera versicolora was tested, and the LC50 of ACE-38 cultures in the optimized fermentation medium was 1.13 μl/ml. Strain ACE-38 is a non-antibiotic Bt engineered strain with high Chrysomelidae toxicity and exhibits good fermentation property. The modified indigenous site-specific recombination system constructed in this study might be useful for the construction of Bt engineered strains containing genes that cannot be expressed in the indigenous site-specific recombination system using plasmid pBMB1205R.

  10. Osmotolerance and leavening ability in sweet and frozen sweet dough. Comparative analysis between Torulaspora delbrueckii and Saccharomyces cerevisiae baker's yeast strains.

    Science.gov (United States)

    Hernandez-Lopez, M J; Prieto, J A; Randez-Gil, F

    2003-01-01

    The response of Saccharomyces cerevisiae and freeze-tolerant Torulaspora delbrueckii strains to osmotic stress and their CO2 production capacity in sweet and frozen-sweet dough has been examined. T. delbrueckii strains, IGC5321 and IGC5323 showed higher leavening ability than Saccharomyces, specially after exposure to hyperosmotic stress of bread dough containing 20% sucrose and 2% salt added. In addition, Torulaspora and especially T. delbrueckii IGC5321 exhibited no loss of CO2 production capacity during freeze-thaw stress. Overall, these results appeared to indicate that Torulaspora cells are more tolerant than Saccharomyces to osmotic stress of bread dough. This trait correlated with a low invertase activity, a slow rate of trehalose mobilisation and the ability to respond rapidly to osmotic stress. Growth behaviour on high osmotic synthetic media was also examined. Cells of the IGC5321 strain showed intrinsic osmotolerance and ion toxicity resistance. However, T. delbrueckii IGC5323 exhibited a clear phenotype of osmosensitivity. Hence, this characteristic may not be essential or the only determinant for leavening ability in salted high-sugar dough. PMID:14533716

  11. A shuttle vector series for precise genetic engineering of Saccharomyces cerevisiae.

    Science.gov (United States)

    Gnügge, Robert; Liphardt, Thomas; Rudolf, Fabian

    2016-03-01

    Shuttle vectors allow for an efficient transfer of recombinant DNA into yeast cells and are widely used in fundamental research and biotechnology. While available shuttle vectors are applicable in many experimental settings, their use in quantitative biology is hampered by insufficient copy number control. Moreover, they often have practical constraints, such as limited modularity and few unique restriction sites. We constructed the pRG shuttle vector series, consisting of single- and multi-copy integrative, centromeric and episomal plasmids with marker genes for the selection in all commonly used auxotrophic yeast strains. The vectors feature a modular design and a large number of unique restriction sites, enabling an efficient exchange of every vector part and expansion of the series. Integration into the host genome is achieved using a double-crossover recombination mechanism, resulting in stable single- and multi-copy modifications. As centromeric and episomal plasmids give rise to a heterogeneous cell population, an analysis of their copy number distribution and loss behaviour was performed. Overall, the shuttle vector series supports the efficient cloning of genes and their maintenance in yeast cells with improved copy number control. PMID:26647923

  12. [Surface display of phytase on Saccharomyces cerevisiae for efficient bioethanol production from corn starch].

    Science.gov (United States)

    Xiao, Yan; Chen, Xianzhong; Shen, Wei; Yang, Haiquan; Fan, You

    2015-12-01

    Production of bioethanol using starch as raw material has become a very prominent technology. However, phytate in the raw material not only decreases ethanol production efficiency, but also increases phosphorus discharge. In this study, to decrease phytate content in an ethanol fermentationprocess, Saccharomyces cerevisiae was engineered forheterologous expression of phytase on the cell surface. The phy gene encoding phytase gene was fused with the C-terminal-half region of α-agglutinin and then inserted downstream of the secretion signal gene, to produce a yeast surface-display expression vector pMGK-AG-phy, which was then transformed into S. cerevisiae. The recombinant yeast strain, PHY, successfully displayed phytase on the surface of cells producing 6.4 U/g wet cells and its properties were further characterized. The growthrate and ethanol production of the PHY strain were faster than the parent S. cerevisiae strain in the fermentation medium by simultaneous saccharification and fermentation. Moreover, the phytate concentration decreased by 91% in dry vinasse compared to the control. In summary, we constructed recombinant S. cerevisiae strain displaying phytase on the cell surface, which could effectively reduce the content of phytate, improve the utilization value of vinasse and reduce the discharge of phosphorus. The strain reported here represents a useful novel engineering platform for developing an environment-friendly system for bioethanol production from a corn substrate. PMID:27093833

  13. A novel wild-type Saccharomyces cerevisiae strain TSH1 in scaling-up of solid-state fermentation of ethanol from sweet sorghum stalks.

    Directory of Open Access Journals (Sweden)

    Ran Du

    Full Text Available The rising demand for bioethanol, the most common alternative to petroleum-derived fuel used worldwide, has encouraged a feedstock shift to non-food crops to reduce the competition for resources between food and energy production. Sweet sorghum has become one of the most promising non-food energy crops because of its high output and strong adaptive ability. However, the means by which sweet sorghum stalks can be cost-effectively utilized for ethanol fermentation in large-scale industrial production and commercialization remains unclear. In this study, we identified a novel Saccharomyces cerevisiae strain, TSH1, from the soil in which sweet sorghum stalks were stored. This strain exhibited excellent ethanol fermentative capacity and ability to withstand stressful solid-state fermentation conditions. Furthermore, we gradually scaled up from a 500-mL flask to a 127-m3 rotary-drum fermenter and eventually constructed a 550-m3 rotary-drum fermentation system to establish an efficient industrial fermentation platform based on TSH1. The batch fermentations were completed in less than 20 hours, with up to 96 tons of crushed sweet sorghum stalks in the 550-m3 fermenter reaching 88% of relative theoretical ethanol yield (RTEY. These results collectively demonstrate that ethanol solid-state fermentation technology can be a highly efficient and low-cost solution for utilizing sweet sorghum, providing a feasible and economical means of developing non-food bioethanol.

  14. Engineering strategy of yeast metabolism for higher alcohol production

    Directory of Open Access Journals (Sweden)

    Shimizu Hiroshi

    2011-09-01

    Full Text Available Abstract Background While Saccharomyces cerevisiae is a promising host for cost-effective biorefinary processes due to its tolerance to various stresses during fermentation, the metabolically engineered S. cerevisiae strains exhibited rather limited production of higher alcohols than that of Escherichia coli. Since the structure of the central metabolism of S. cerevisiae is distinct from that of E. coli, there might be a problem in the structure of the central metabolism of S. cerevisiae. In this study, the potential production of higher alcohols by S. cerevisiae is compared to that of E. coli by employing metabolic simulation techniques. Based on the simulation results, novel metabolic engineering strategies for improving higher alcohol production by S. cerevisiae were investigated by in silico modifications of the metabolic models of S. cerevisiae. Results The metabolic simulations confirmed that the high production of butanols and propanols by the metabolically engineered E. coli strains is derived from the flexible behavior of their central metabolism. Reducing this flexibility by gene deletion is an effective strategy to restrict the metabolic states for producing target alcohols. In contrast, the lower yield using S. cerevisiae originates from the structurally limited flexibility of its central metabolism in which gene deletions severely reduced cell growth. Conclusions The metabolic simulation demonstrated that the poor productivity of S. cerevisiae was improved by the introduction of E. coli genes to compensate the structural difference. This suggested that gene supplementation is a promising strategy for the metabolic engineering of S. cerevisiae to produce higher alcohols which should be the next challenge for the synthetic bioengineering of S. cerevisiae for the efficient production of higher alcohols.

  15. Engineering strategy of yeast metabolism for higher alcohol production

    Science.gov (United States)

    2011-01-01

    Background While Saccharomyces cerevisiae is a promising host for cost-effective biorefinary processes due to its tolerance to various stresses during fermentation, the metabolically engineered S. cerevisiae strains exhibited rather limited production of higher alcohols than that of Escherichia coli. Since the structure of the central metabolism of S. cerevisiae is distinct from that of E. coli, there might be a problem in the structure of the central metabolism of S. cerevisiae. In this study, the potential production of higher alcohols by S. cerevisiae is compared to that of E. coli by employing metabolic simulation techniques. Based on the simulation results, novel metabolic engineering strategies for improving higher alcohol production by S. cerevisiae were investigated by in silico modifications of the metabolic models of S. cerevisiae. Results The metabolic simulations confirmed that the high production of butanols and propanols by the metabolically engineered E. coli strains is derived from the flexible behavior of their central metabolism. Reducing this flexibility by gene deletion is an effective strategy to restrict the metabolic states for producing target alcohols. In contrast, the lower yield using S. cerevisiae originates from the structurally limited flexibility of its central metabolism in which gene deletions severely reduced cell growth. Conclusions The metabolic simulation demonstrated that the poor productivity of S. cerevisiae was improved by the introduction of E. coli genes to compensate the structural difference. This suggested that gene supplementation is a promising strategy for the metabolic engineering of S. cerevisiae to produce higher alcohols which should be the next challenge for the synthetic bioengineering of S. cerevisiae for the efficient production of higher alcohols. PMID:21902829

  16. Analysis of the secondary compounds produced by Saccharomyces cerevisiae and wild yeast strains during the production of "cachaça" Análise dos componentes secundários produzidos por Saccharomyces cerevisiae e leveduras selvagens durante a produção de cachaça

    Directory of Open Access Journals (Sweden)

    Maria Cecília Fachine Dato

    2005-03-01

    Full Text Available The aim of this study is to compare the composition of "cachaças" produced in 10 fermentation cycles by Saccharomyces cerevisiae (Sc and wild yeast strains [Pichia silvicola (Ps, Pichia anomala 1 (Pa1, Pichia anomala 2 (Pa2 and Dekkera bruxelensis (Db], isolated from distilleries in Jaboticabal - SP, Brazil. The secondary components of the heart fraction were determined by gas chromatography. The levels of secondary components were influenced by the wine pH, which varied among yeast strains. S. cerevisiae showed slightly more secondary components, whereas wild strains produced more higher alcohols. Wild yeast strains were shown to be adequate for the production of a high quality "cachaça".O presente trabalho visou estabelecer uma comparação entre composição de cachaças produzidas por Saccharomyces cerevisiae (Sc e estirpes de leveduras selvagens [Pichia silvicola (Ps, Pichia anomala 1 (Pa1, Pichia anomala 2 (Pa2 e Dekkera bruxelensis (Db], isoladas em destilarias da região de Jaboticabal-SP. Os componentes secundários da fração denominada coração foram determinados por cromatografia gasosa. Os níveis dos componentes secundários foram influenciados pelo pH dos respectivos vinhos, os quais dependem da estirpe de levedura empregada no processo fermentativo. A Saccharomyces cerevisiae apresentou valores ligeiramente superiores de componentes secundários, enquanto as estirpes selvagens produziram maiores teores de álcoois superiores. As estirpes selvagens de leveduras mostraram-se adequadas para obtenção de uma cachaça de boa qualidade.

  17. Transcriptome analysis of a respiratory Saccharomyces cerevisiae strain suggests the expression of its phenotype is glucose insensitive and predominantly controlled by Hap4, Cat8 and Mig1

    Directory of Open Access Journals (Sweden)

    Bonander Nicklas

    2008-07-01

    Full Text Available Abstract Background We previously described the first respiratory Saccharomyces cerevisiae strain, KOY.TM6*P, by integrating the gene encoding a chimeric hexose transporter, Tm6*, into the genome of an hxt null yeast. Subsequently we transferred this respiratory phenotype in the presence of up to 50 g/L glucose to a yeast strain, V5 hxt1-7Δ, in which only HXT1-7 had been deleted. In this study, we compared the transcriptome of the resultant strain, V5.TM6*P, with that of its wild-type parent, V5, at different glucose concentrations. Results cDNA array analyses revealed that alterations in gene expression that occur when transitioning from a respiro-fermentative (V5 to a respiratory (V5.TM6*P strain, are very similar to those in cells undergoing a diauxic shift. We also undertook an analysis of transcription factor binding sites in our dataset by examining previously-published biological data for Hap4 (in complex with Hap2, 3, 5, Cat8 and Mig1, and used this in combination with verified binding consensus sequences to identify genes likely to be regulated by one or more of these. Of the induced genes in our dataset, 77% had binding sites for the Hap complex, with 72% having at least two. In addition, 13% were found to have a binding site for Cat8 and 21% had a binding site for Mig1. Unexpectedly, both the up- and down-regulation of many of the genes in our dataset had a clear glucose dependence in the parent V5 strain that was not present in V5.TM6*P. This indicates that the relief of glucose repression is already operable at much higher glucose concentrations than is widely accepted and suggests that glucose sensing might occur inside the cell. Conclusion Our dataset gives a remarkably complete view of the involvement of genes in the TCA cycle, glyoxylate cycle and respiratory chain in the expression of the phenotype of V5.TM6*P. Furthermore, 88% of the transcriptional response of the induced genes in our dataset can be related to the potential

  18. A simple and effective method for construction of Escherichia coli strains proficient for genome engineering.

    Directory of Open Access Journals (Sweden)

    Young Shin Ryu

    Full Text Available Multiplex genome engineering is a standalone recombineering tool for large-scale programming and accelerated evolution of cells. However, this advanced genome engineering technique has been limited to use in selected bacterial strains. We developed a simple and effective strain-independent method for effective genome engineering in Escherichia coli. The method involves introducing a suicide plasmid carrying the λ Red recombination system into the mutS gene. The suicide plasmid can be excised from the chromosome via selection in the absence of antibiotics, thus allowing transient inactivation of the mismatch repair system during genome engineering. In addition, we developed another suicide plasmid that enables integration of large DNA fragments into the lacZ genomic locus. These features enable this system to be applied in the exploitation of the benefits of genome engineering in synthetic biology, as well as the metabolic engineering of different strains of E. coli.

  19. Strain engineering of diamond silicon vacancy centers in MEMS cantilevers

    Science.gov (United States)

    Meesala, Srujan; Sohn, Young-Ik; Atikian, Haig; Holzgrafe, Jeffrey; Zhang, Mian; Burek, Michael; Loncar, Marko

    2016-05-01

    The silicon vacancy (SiV) center in diamond has recently attracted attention as a solid state quantum emitter due to its attractive optical properties. We fabricate diamond MEMS cantilevers, and use electrostatic actuation to apply controlled strain fields to single SiV centers implanted in these devices. The strain response of the four electronic transitions of the SiV at 737 nm is measured via cryogenic (4 K) photoluminescence excitation. We demonstrate over 300 GHz of tuning for the mean transition frequency between the ground and excited states, and over 100 GHz of tuning for the orbital splittings within the ground and excited states. The interaction Hamiltonian for strain fields is inferred, and large strain susceptibilities of the order 1 PHz/strain are measured. We discuss prospects to utilize our device to reduce phonon-induced decoherence in SiV spin qubits, and to exploit the large strain susceptibilities for hybrid quantum systems based on nanomechanical resonators.

  20. Conclusion on the peer review of the pesticide risk assessment of the active substance cerevisane (cell walls of Saccharomyces cerevisiae strain LAS117

    Directory of Open Access Journals (Sweden)

    European Food Safety Authority

    2014-06-01

    Full Text Available The conclusions of the European Food Safety Authority (EFSA following the peer review of the initial risk assessments carried out by the competent authority of the rapporteur Member State France for the pesticide active substance cerevisane (cell walls of Saccharomyces cerevisiae strain LAS117, and the assessment of the proposal for inclusion of the substance in Annex IV of Regulation (EC No 396/2005, are reported. The context of the peer review was that required by Regulation (EC No 1107/2009 of the European Parliament and of the Council. The conclusions were reached on the basis of the evaluation of the representative uses of the active substance as a systemic resistance inducer against fungi and bacteria in lettuce and other salad crops. The reliable endpoints concluded as being appropriate for use in regulatory risk assessment, derived from the available studies and literature in the dossier peer reviewed, are presented. Missing information identified as being required by the regulatory framework is listed. No concerns are identified.

  1. Identification and classification of genes required for tolerance to freeze-thaw stress revealed by genome-wide screening of Saccharomyces cerevisiae deletion strains.

    Science.gov (United States)

    Ando, Akira; Nakamura, Toshihide; Murata, Yoshinori; Takagi, Hiroshi; Shima, Jun

    2007-03-01

    Yeasts used in bread making are exposed to freeze-thaw stress during frozen-dough baking. To clarify the genes required for freeze-thaw tolerance, genome-wide screening was performed using the complete deletion strain collection of diploid Saccharomyces cerevisiae. The screening identified 58 gene deletions that conferred freeze-thaw sensitivity. These genes were then classified based on their cellular function and on the localization of their products. The results showed that the genes required for freeze-thaw tolerance were frequently involved in vacuole functions and cell wall biogenesis. The highest numbers of gene products were components of vacuolar H(+)-ATPase. Next, the cross-sensitivity of the freeze-thaw-sensitive mutants to oxidative stress and to cell wall stress was studied; both of these are environmental stresses closely related to freeze-thaw stress. The results showed that defects in the functions of vacuolar H(+)-ATPase conferred sensitivity to oxidative stress and to cell wall stress. In contrast, defects in gene products involved in cell wall assembly conferred sensitivity to cell wall stress but not to oxidative stress. Our results suggest the presence of at least two different mechanisms of freeze-thaw injury: oxidative stress generated during the freeze-thaw process, and defects in cell wall assembly. PMID:16989656

  2. Strain engineering of WS2, WSe2, and WTe2

    KAUST Repository

    Amin, Bin

    2014-01-01

    We perform first-principles calculations to investigate the structural, electronic, and vibrational properties of WS2, WSe2, and WTe2 monolayers, taking into account the strong spin orbit coupling. A transition from a direct to an indirect band gap is achieved for compressive strain of 1% for WS2, 1.5% for WSe2, and 2% for WTe 2, while the nature of the band gap remains direct in the case of tensile strain. The size of the band gap passes through a maximum under compressive strain and decreases monotonically under tensile strain. A strong spin splitting is found for the valence band in all three compounds, which is further enhanced by tensile strain. The mobility of the electrons grows along the series WS2 < WSe2 < WTe2. This journal is © the Partner Organisations 2014.

  3. Effect of Agave tequilana juice on cell wall polysaccharides of three Saccharomyces cerevisiae strains from different origins.

    Science.gov (United States)

    Aguilar-Uscanga, Blanca; Arrizon, Javier; Ramirez, Jesús; Solis-Pacheco, Josué

    2007-02-01

    In this study, a characterization of cell wall polysaccharide composition of three yeasts involved in the production of agave distilled beverages was performed. The three yeast strains were isolated from different media (tequila, mezcal and bakery) and were evaluated for the beta(1,3)-glucanase lytic activity and the beta-glucan/ mannan ratio during the fermentation of Agave tequilana juice and in YPD media (control). Fermentations were performed in shake flasks with 30 g l(-1) sugar concentration of A. tequilana juice and with the control YPD using 30 g l(-1) of glucose. The three yeasts strains showed different levels of beta-glucan and mannan when they were grown in A. tequilana juice in comparison to the YPD media. The maximum rate of cell wall lyses was 50% lower in fermentations with A. tequilana juice for yeasts isolated from tequila and mezcal than compared to the bakery yeast.

  4. Effect of Engineering Character on Stress-Strain Relationship in Post-Peak Area

    Institute of Scientific and Technical Information of China (English)

    TANG Lei; KE Min-yong; YAN Jian-hua

    2003-01-01

    Constitutive experiments are the base of all rock mechanics works. The effect of engineering character on constitutive law is a new problem of rock mechanics. The results of series specimens based on the uniaxial and plane strain compression experiments were presented and discussed. It is found that engineering or experiment character has obvious effects on stress-strain relationship and especially on mechanic parameters in post-peak area. And the law of size effect of softening materials was also discussed.

  5. Efeitos do cádmio sobre o crescimento das leveduras Saccharomyces cerevisiae PE-2 e Saccharomyces cerevisiae IZ-1904, e a capacidade da vinhaça em atenuar a toxicidade Effect of cadmium on the growth of two Saccharomyces cerevisiae strains, and the vinasse capacity to atenuate the toxicity

    Directory of Open Access Journals (Sweden)

    Samuel Mariano-da-Silva

    2004-03-01

    , minimizando os efeitos deletérios do metal.The present study was carried out in order to evaluate the capability of different cadmium concentration (0; 0,05, 0,10 and 0,50mM to affect the growth of two S. cerevisiae strains (PE-2 and IZ-1904 in YED (yeast extract 1% and dextrose 2% medium, and to evaluate the three vinasse concentration capability (0,15 and 30% to attenuate the two cadmium concentration toxicity (0,1 and 0,5mM, using S. cerevisiae PE-2 strain in YED medium. In the first assay, the medium was inoculated in aseptic conditions with 1mL of 1% yeast suspension (PE-2 or IZ-1904 and incubated at 30ºC, 70 RPM for 18 hours. During anaerobic growth (0, 2, 4, 6, 8, 10, 12, 14, 16 and 18 hours, portions of cell suspension were taken out and biomass concentration was determined. At the end of fermentation, yeast viability, budding rate and bacterial contamination were determined. Both, initial and final trehalose, was measured. In the second assay, the medium was inoculated in aseptic conditions with 2mL of 1% PE-2 suspension and incubated at 30ºC, 120 rpm for 18 hours. During the anaerobic growth (0, 2, 4, 6, 8, 10, 12,14, 16 and 18 hours portions of cell suspension were taken out and biomass concentration was determined. At the end of fermentation, alcohol production, yeast viability, budding rate and bacterial contamination were determined. Both, initial and final trehalose, was measured. The increase of cadmium levels showed a reduction on yeast growth and cell viability. Vinasse showed low toxicity, but protected yeast cells very effectively against the toxic effects of cadmium.

  6. Overexpression of a homogeneous oligosaccharide with 13C labeling by genetically engineered yeast strain.

    Science.gov (United States)

    Kamiya, Yukiko; Yamamoto, Sayoko; Chiba, Yasunori; Jigami, Yoshifumi; Kato, Koichi

    2011-08-01

    This report describes a novel method for overexpression of (13)C-labeled oligosaccharides using genetically engineered Saccharomyces cerevisiae cells, in which a homogeneous high-mannose-type oligosaccharide accumulates because of deletions of genes encoding three enzymes involved in the processing pathway of asparagine-linked oligosaccharides in the Golgi complex. Using uniformly (13)C-labeled glucose as the sole carbon source in the culture medium of these engineered yeast cells, high yields of the isotopically labeled Man(8)GlcNAc(2) oligosaccharide could be successfully harvested from glycoprotein extracts of the cells. Furthermore, (13)C labeling at selected positions of the sugar residues in the oligosaccharide could be achieved using a site-specific (13)C-enriched glucose as the metabolic precursor, facilitating NMR spectral assignments. The (13)C-labeling method presented provides the technical basis for NMR analyses of structures, dynamics, and interactions of larger, branched oligosaccharides.

  7. Protein engineering of cyclodextrin glycosyltransferase from Bacillus circulans strain 251

    NARCIS (Netherlands)

    Penninga, Dirk

    1996-01-01

    An enormous diversity of molecular functions in living organisms is carried out by proteins. Our studies have focussed on the functional analysis of a starch-converting enzyme, cyclodextrin glycosyltransferase (CGTase) from Bacillus circulans strain 251. Zie: Summary

  8. Effects on Anthocyanin Composition in Red Wines Fermented by Different Saccharomyces cerevisiae Strains%不同酿酒酵母发酵对红葡萄酒中花色苷组成的影响

    Institute of Scientific and Technical Information of China (English)

    李双石; 苏宁; 吴志明; 李淳; 兰蓉

    2012-01-01

    To explore wild yeast resources in China, the anthocyanin composition and content in the red wines fermented by different Saccharomyces cerevisiae strains were compared. Two different Saccharomyces cerevisiae strains (indigenous Saccharomyces cerevisiae strain Y17, commercial active dry yeast F15) were separately used in red wines production. The anthocyanin components in wines were studied by high performance liquid chromatography-mass spec- trometry (HPLC-MS). The results showed that the diversities of anthocyanins in the wines fermented by different yeast strains were similar, but the contents of different anthocyanins in the wines were quite different. The indigenous yeast strain Y17 produced wines with higher concentrations of anthocyanins.%比较了不同酿酒酵母菌株发酵对红葡萄酒中花色苷组分的影响,为本土酵母的开发应用提供依据。采用本土自筛酿酒酵母菌株Y17和进口商业酵母菌株F15分别酿造干红葡萄酒,并利用高效液相色谱-质谱联用技术(HPLC-MS)对葡萄酒中的花色苷成分进行检测。结果表明,不同酵母发酵葡萄酒中的花色苷成分种类大体相同,但各种花色苷的含量具有较大差别,本土酵母菌株Y17在发酵生产高花色苷含量葡萄酒方面具有优势。

  9. Nanoscale strain engineering of graphene and graphene-based devices

    OpenAIRE

    Yeh, N. -C.; Hsu, C.-C.; Teague, M. L.; Wang, J.-Q.; Boyd, D A; Chen, C.-C.

    2016-01-01

    Structural distortions in nano-materials can induce dramatic changes in their electronic properties. This situation is well manifested in graphene, a two-dimensional honeycomb structure of carbon atoms with only one atomic layer thickness. In particular, strained graphene can result in both charging effects and pseudo-magnetic fields, so that controlled strain on a perfect graphene lattice can be tailored to yield desirable electronic properties. Here, we describe the theoretical foundation f...

  10. Strain engineering the work function in monolayer metal dichalcogenides

    International Nuclear Information System (INIS)

    We use first-principles density functional theory to investigate the effect of both tensile and compressive strain on the work functions of various metal dichalcogenide monolayers. We find that for all six species considered, including MoS2, WS2, SnS2, VS2, MoSe2 and MoTe2, that compressive strain of up to 10% decreases the work function continuously by as much as 1.0 eV. Large enough tensile strain is also found to decrease the work function, although in some cases we observe an increase in the work function for intermediate values of tensile strain. This work function modulation is attributed to a weakening of the chalcogenide-metal bonds and an increase in total energy of each system as a function of strain. Values of strain which bring the metal atoms closer together lead to an increase in electrostatic potential energy, which in turn results in an increase in the vacuum potential level. The net effect on the work function can be explained in terms of the balance between the increases in the vacuum potential levels and Fermi energy. (paper)

  11. Strain engineering the work function in monolayer metal dichalcogenides

    Science.gov (United States)

    Lanzillo, Nicholas A.; Simbeck, Adam J.; Nayak, Saroj K.

    2015-05-01

    We use first-principles density functional theory to investigate the effect of both tensile and compressive strain on the work functions of various metal dichalcogenide monolayers. We find that for all six species considered, including MoS2, WS2, SnS2, VS2, MoSe2 and MoTe2, that compressive strain of up to 10% decreases the work function continuously by as much as 1.0 eV. Large enough tensile strain is also found to decrease the work function, although in some cases we observe an increase in the work function for intermediate values of tensile strain. This work function modulation is attributed to a weakening of the chalcogenide-metal bonds and an increase in total energy of each system as a function of strain. Values of strain which bring the metal atoms closer together lead to an increase in electrostatic potential energy, which in turn results in an increase in the vacuum potential level. The net effect on the work function can be explained in terms of the balance between the increases in the vacuum potential levels and Fermi energy.

  12. Adenine auxotrophy--be aware: some effects of adenine auxotrophy in Saccharomyces cerevisiae strain W303-1A.

    Science.gov (United States)

    Kokina, Agnese; Kibilds, Juris; Liepins, Janis

    2014-08-01

    Adenine auxotrophy is a commonly used genetic marker in haploid yeast strains. Strain W303-1A, which carries the ade2-1 mutation, is widely used in physiological and genetic research. Yeast extract-based rich medium contains a low level of adenine, so that adenine is often depleted before glucose. This could affect the cell physiology of adenine auxotrophs grown in rich medium. The aim of our study was to assess the effects of adenine auxotrophy on cell morphology and stress physiology. Our results show that adenine depletion halts cell division, but that culture optical density continues to increase due to cell swelling. Accumulation of trehalose and a coincident 10-fold increase in desiccation stress tolerance is observed in adenine auxotrophs after adenine depletion, when compared to prototrophs. Under adenine starvation, long-term survival of W303-1A is lower than during carbon starvation, but higher than during leucine starvation. We observed drastic adenine-dependent changes in cell stress physiology, suggesting that results may be biased when adenine auxotrophs are grown in rich media without adenine supplementation.

  13. Sensitivities to monochromatic 254-nm and 365-nm radiation of closely related strains of Saccharomyces cerevisiae with differing repair capabilities

    International Nuclear Information System (INIS)

    Sensitivity to monochromatic 254- and 365-nm radiation was compared in closely related yeast strains with defects in one or more of the excision-repair (rad1), error-prone repair (rad18), or recombinational-repair (rad51) pathways. At 254 nm, mutants defective in a single repair pathway exhibited slight to moderate UV sensitivity;,those defective in two separate pathways were somewhat more UV sensitive, while triple mutants defective in all three pathways exhibited extreme UV sensitivity with a lethal event corresponding to 0.05 J m-2. Repair defects also rendered mutants sensitive to 365-nm radiation: strains with single defects exhibited slight sensitivity, mutants with two defective pathways were more sensitive, and triple mutants exhibited maximal sensitivity with a lethal event corresponding to 2.4 x 104 J m-2. Evidence for dimer involvement in the yeast mutant was obtained by demonstrating that lethality at both 254 and 365 nm was photoreactivated by light at 405 nm. (author)

  14. Efficient construction of homozygous diploid strains identifies genes required for the hyper-filamentous phenotype in Saccharomyces cerevisiae.

    Directory of Open Access Journals (Sweden)

    Kentaro Furukawa

    Full Text Available Yeast cells undergo diploid-specific developments such as spore formation via meiosis and pseudohyphal development under certain nutrient-limited conditions. Studies on these aspects require homozygous diploid mutants, which are generally constructed by crossing strains of opposite mating-type with the same genetic mutation. So far, there has been no direct way to generate and select diploids from haploid cells. Here, we developed a method for efficient construction of homozygous diploids using a PGAL1-HO gene (galactose-inducible mating-type switch and a PSTE18-URA3 gene (counter selection marker for diploids. Diploids are generated by transient induction of the HO endonuclease, which is followed by mating of part of the haploid population. Since the STE18 promoter is repressed in diploids, diploids carrying PSTE18-URA3 can be selected on 5-fluoroorotic acid (5-FOA plates where the uracil prototrophic haploids cannot grow. To demonstrate that this method is useful for genetic studies, we screened suppressor mutations of the complex colony morphology, strong agar invasion and/or hyper-filamentous growth caused by lack of the Hog1 MAPK in the diploid Σ1278b strain background. Following this approach, we identified 49 suppressor mutations. Those include well-known positive regulator genes for filamentous growth signaling pathways, genes involved in mitochondrial function, DNA damage checkpoint, chromatin remodeling, and cell cycle, and also previously uncharacterized genes. Our results indicate that combinatorial use of the PGAL1-HO and PSTE18-URA3 genes is suitable to efficiently construct and select diploids and that this approach is useful for genetic studies especially when combined with large-scale screening.

  15. Performance of the auxotrophic Saccharomyces cerevisiae BY4741 as host for the production of IL-1β in aerated fed-batch reactor: role of ACA supplementation, strain viability, and maintenance energy

    Directory of Open Access Journals (Sweden)

    Zueco Jesus

    2009-12-01

    Full Text Available Abstract Background Saccharomyces cerevisiae BY4741 is an auxotrophic commonly used strain. In this work it has been used as host for the expression and secretion of human interleukin-1β (IL1β, using the cell wall protein Pir4 as fusion partner. To achieve high cell density and, consequently, high product yield, BY4741 [PIR4-IL1β] was cultured in an aerated fed-batch reactor, using a defined mineral medium supplemented with casamino acids as ACA (auxotrophy-complementing amino acid source. Also the S. cerevisiae mutant BY4741 Δyca1 [PIR4-IL1β], carrying the deletion of the YCA1 gene coding for a caspase-like protein involved in the apoptotic response, was cultured in aerated fed-batch reactor and compared to the parental strain, to test the effect of this mutation on strain robustness. Viability of the producer strains was examined during the runs and a mathematical model, which took into consideration the viable biomass present in the reactor and the glucose consumption for both growth and maintenance, was developed to describe and explain the time-course evolution of the process for both, the BY4741 parental and the BY4741 Δyca1 mutant strain. Results Our results show that the concentrations of ACA in the feeding solution, corresponding to those routinely used in the literature, are limiting for the growth of S. cerevisiae BY4741 [PIR4-IL1β] in fed-batch reactor. Even in the presence of a proper ACA supplementation, S. cerevisiae BY4741 [PIR4-IL1β] did not achieve a high cell density. The Δyca1 deletion did not have a beneficial effect on the overall performance of the strain, but it had a clear effect on its viability, which was not impaired during fed-batch operations, as shown by the kd value (0.0045 h-1, negligible if compared to that of the parental strain (0.028 h-1. However, independently of their robustness, both the parental and the Δyca1 mutant ceased to grow early during fed-batch runs, both strains using most of the

  16. Modulation of Chaperone Gene Expression in Mutagenized Saccharomyces cerevisiae Strains Developed for Recombinant Human Albumin Production Results in Increased Production of Multiple Heterologous Proteins▿

    OpenAIRE

    Payne, T.; Finnis, C.; Evans, L R; Mead, D. J.; Avery, S V; Archer, D. B.; Sleep, D.

    2008-01-01

    The yeast Saccharomyces cerevisiae has been successfully established as a commercially viable system for the production of recombinant proteins. Manipulation of chaperone gene expression has been utilized extensively to increase recombinant protein production from S. cerevisiae, focusing predominantly on the products of the protein disulfide isomerase gene PDI1 and the hsp70 gene KAR2. Here we show that the expression of the genes SIL1, LHS1, JEM1, and SCJ1, all of which are involved in regul...

  17. EasyClone: method for iterative chromosomal integration of multiple genes in Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Jensen, Niels Bjerg; Strucko, Tomas; Kildegaard, Kanchana Rueksomtawin;

    2014-01-01

    Development of strains for efficient production of chemicals and pharmaceuticals requires multiple rounds of genetic engineering. In this study, we describe construction and characterization of EasyClone vector set for baker's yeast Saccharomyces cerevisiae, which enables simultaneous expression...... in the chromosome and show unchanged expression levels. Hence, this system is suitable for metabolic engineering in yeast where multiple rounds of gene introduction and marker recycling can be carried out....

  18. Bulk segregant analysis by high-throughput sequencing reveals a novel xylose utilization gene from Saccharomyces cerevisiae.

    Directory of Open Access Journals (Sweden)

    Jared W Wenger

    2010-05-01

    Full Text Available Fermentation of xylose is a fundamental requirement for the efficient production of ethanol from lignocellulosic biomass sources. Although they aggressively ferment hexoses, it has long been thought that native Saccharomyces cerevisiae strains cannot grow fermentatively or non-fermentatively on xylose. Population surveys have uncovered a few naturally occurring strains that are weakly xylose-positive, and some S. cerevisiae have been genetically engineered to ferment xylose, but no strain, either natural or engineered, has yet been reported to ferment xylose as efficiently as glucose. Here, we used a medium-throughput screen to identify Saccharomyces strains that can increase in optical density when xylose is presented as the sole carbon source. We identified 38 strains that have this xylose utilization phenotype, including strains of S. cerevisiae, other sensu stricto members, and hybrids between them. All the S. cerevisiae xylose-utilizing strains we identified are wine yeasts, and for those that could produce meiotic progeny, the xylose phenotype segregates as a single gene trait. We mapped this gene by Bulk Segregant Analysis (BSA using tiling microarrays and high-throughput sequencing. The gene is a putative xylitol dehydrogenase, which we name XDH1, and is located in the subtelomeric region of the right end of chromosome XV in a region not present in the S288c reference genome. We further characterized the xylose phenotype by performing gene expression microarrays and by genetically dissecting the endogenous Saccharomyces xylose pathway. We have demonstrated that natural S. cerevisiae yeasts are capable of utilizing xylose as the sole carbon source, characterized the genetic basis for this trait as well as the endogenous xylose utilization pathway, and demonstrated the feasibility of BSA using high-throughput sequencing.

  19. Straining mode-dependent collagen remodeling in engineered cardiovascular tissue

    NARCIS (Netherlands)

    Rubbens, M.P.; Mol, A.; Marion, M.H. van; Hanemaaijer, R.; Bank, R.A.; Baaijens, F.P.T.; Bouten, C.V.C.

    2009-01-01

    Similar to native cardiovascular tissues, the mechanical properties of engineered cardiovascular constructs depend on the composition and quality of the extracellular matrix, which is a net result of matrix remodeling processes within the tissue. To improve tissue remodeling, and hence tissue mechan

  20. Engineering the strain in graphene layers with Au decoration

    Energy Technology Data Exchange (ETDEWEB)

    Pannu, Compesh, E-mail: compesh@gmail.com; Singh, Udai B.; Kumar, Sunil; Tripathi, A.; Kabiraj, D.; Avasthi, D.K., E-mail: dka4444@gmail.com

    2014-07-01

    Graphene sheets decorated with Au nanodots are synthesized by deposition of Au of three different thicknesses and subsequent annealing at 400 °C. Different thicknesses of Au film for the formation of Au nanodots on graphene are measured using Rutherford backscattering spectrometry and morphology is studied using scanning electron microscopy. Raman spectroscopy indicates 3–6-fold increase in I{sub D}/I{sub G} ratio depending on the content of Au deposited on graphene. The increase in disorder in Au decorated graphene layers is explained on the basis of interaction of Au atoms with Π bonds of graphene. The splitting and blueshift in G band signifies compressive strain in Au deposited graphene. X-ray diffraction studies using synchrotron radiation source confirm compressive strain in graphene, which increases with increase of Au film thickness.

  1. Strain engineered nanomembranes as anodes for lithium ion batteries

    OpenAIRE

    Deng, Junwen

    2015-01-01

    Lithium ion batteries (LIBs) have attracted considerable interest due to their wide range of applications, such as portable electronics, electric vehicles (EVs) and aerospace applications. Particularly, the emergence of a variety of nanostructured materials has driven the development of LIBs towards the next generation, which is featured with high specific energy and large power density. Herein, rolled-up nanotechnology is introduced for the design of strain-released materials as anodes of...

  2. Saccharomyces cerevisiae engineered for xylose metabolism requires gluconeogenesis and the oxidative branch of the pentose phosphate pathway for aerobic xylose assimilation

    Science.gov (United States)

    Saccharomyces strains engineered to ferment xylose using Scheffersomyces stipitis xylose reductase (XR) and xylitol dehydrogenase (XDH) genes appear to be limited by metabolic imbalances due to differing cofactor specificities of XR and XDH. The S. stipitis XR, which uses nicotinamide adenine dinucl...

  3. Cystathionine accumulation in Saccharomyces cerevisiae.

    OpenAIRE

    Ono, B; Suruga, T; Yamamoto, M.; Yamamoto, S.; Murata, K; Kimura, A; Shinoda, S; Ohmori, S.

    1984-01-01

    A cysteine-dependent strain of Saccharomyces cerevisiae and its prototrophic revertants accumulated cystathionine in cells. The cystathionine accumulation was caused by a single mutation having a high incidence of gene conversion. The mutation was designated cys3 and was shown to cause loss of gamma-cystathionase activity. Cysteine dependence of the initial strain was determined by two linked and interacting mutations, cys3 and cys1 . Since cys1 mutations cause a loss of serine acetyltransfer...

  4. Investigating xylose metabolism in recombinant Saccharomyces cerevisiae via 13C metabolic flux analysis

    OpenAIRE

    Feng, Xueyang; Zhao, Huimin

    2013-01-01

    Background To engineer Saccharomyces cerevisiae for efficient xylose utilization, a fungal pathway consisting of xylose reductase, xylitol dehydrogenase, and xylulose kinase is often introduced to the host strain. Despite extensive in vitro studies on the xylose pathway, the intracellular metabolism rewiring in response to the heterologous xylose pathway remains largely unknown. In this study, we applied 13C metabolic flux analysis and stoichiometric modeling to systemically investigate the f...

  5. Tunable gaps and enhanced mobilities in strain-engineered silicane

    International Nuclear Information System (INIS)

    The recent demonstration of single-atom thick, sp3-hybridized group 14 analogues of graphene enables the creation of materials with electronic structures that are manipulated by the nature of the covalently bound substituents above and below the sheet. These analogues can be electronically derived from isolated (111) layers of the bulk diamond lattice. Here, we perform systematic Density Functional Theory calculations to understand how the band dispersions, effective masses, and band gaps change as the bulk silicon (111) layers are continuously separated from each other until they are electronically isolated, and then passivated with hydrogen. High-level calculations based on HSE06 hybrid functionals were performed on each endpoint to compare directly with experimental values. We find that the change in the electronic structure due to variations in the Si-H bond length, Si-Si-Si bond angle, and most significantly the Si-Si bond length can tune the nature of the band gap from indirect to direct with dramatic effects on the transport properties. First-principles calculations of the phonon-limited electron mobility predict a value of 464 cm2/Vs for relaxed indirect band gap Si-H monolayers at room temperature. However, for 1.6% tensile strain, the band gap becomes direct, which increases the mobility significantly (8 551 cm2/Vs at 4% tensile strain). In total, this analysis of Si-based monolayers suggests that strain can change the nature of the band gap from indirect to direct and increase the electron mobility more than 18-fold

  6. Tunable gaps and enhanced mobilities in strain-engineered silicane

    Energy Technology Data Exchange (ETDEWEB)

    Restrepo, Oscar D.; Mishra, Rohan; Windl, Wolfgang, E-mail: windl@matsceng.ohio-state.edu [Department of Materials Science and Engineering, the Ohio State University, Columbus, Ohio 43210 (United States); Goldberger, Joshua E. [Department of Chemistry and Biochemistry, the Ohio State University, Columbus, Ohio 43210 (United States)

    2014-01-21

    The recent demonstration of single-atom thick, sp{sup 3}-hybridized group 14 analogues of graphene enables the creation of materials with electronic structures that are manipulated by the nature of the covalently bound substituents above and below the sheet. These analogues can be electronically derived from isolated (111) layers of the bulk diamond lattice. Here, we perform systematic Density Functional Theory calculations to understand how the band dispersions, effective masses, and band gaps change as the bulk silicon (111) layers are continuously separated from each other until they are electronically isolated, and then passivated with hydrogen. High-level calculations based on HSE06 hybrid functionals were performed on each endpoint to compare directly with experimental values. We find that the change in the electronic structure due to variations in the Si-H bond length, Si-Si-Si bond angle, and most significantly the Si-Si bond length can tune the nature of the band gap from indirect to direct with dramatic effects on the transport properties. First-principles calculations of the phonon-limited electron mobility predict a value of 464 cm{sup 2}/Vs for relaxed indirect band gap Si-H monolayers at room temperature. However, for 1.6% tensile strain, the band gap becomes direct, which increases the mobility significantly (8 551 cm{sup 2}/Vs at 4% tensile strain). In total, this analysis of Si-based monolayers suggests that strain can change the nature of the band gap from indirect to direct and increase the electron mobility more than 18-fold.

  7. Application of fiber optic distributed sensor for strain measurement in civil engineering

    Science.gov (United States)

    Kurashima, Toshio; Usu, Tomonori; Tanaka, Kuniaki; Nobiki, Atsushi; Sato, Masashi; Nakai, Kenji

    1997-11-01

    We report on civil engineering applications of a fiber optic distributed strain sensor. It consists of a sensing fiber and a high performance optical time domain reflectometer (OTDR), for measuring both strain and optical loss distribution along optical fibers by accessing only one end of the fiber. The OTDR can measure distributed strain with an accuracy of better than +/- 60 X 10-6 and a high spatial resolution of up to 1 m over a 10 km long fiber. In model experiments using the OTDR, we measured the strain changes in fibers attached to the surface of a concrete test beam. The performance of the fiber strain sensor was tested by measuring the strain distribution in optical fibers and comparing the results with resistance strain gage measurements for several loads. We found that the two sets of results were similar, and in addition, we demonstrated experimentally that the sensor was able to measure an induced strain change of less than 100 by 10-6, which is nearly the elastic limit of the concrete material. These results show the potential of the OTDR to extend the application of monitoring systems to such areas as large building diagnostics for civil engineering.

  8. Strain- and twist-engineered optical absorption of few-layer black phosphorus

    Science.gov (United States)

    Jia, Qian; Kong, XiangHua; Qiao, JingSi; Ji, Wei

    2016-09-01

    Density functional and many-body perturbation theories calculations were carried out to investigate fundamental and optical bandgap, exciton binding energy and optical absorption property of normal and strain- and twist-engineered few-layer black phosphorus (BP). We found that the fundamental bandgaps of few layer BP can be engineered by layer stacking and in-plane strain, with linear relationships to their associated exciton binding energies. The strain-dependent optical absorption behaviors are also anisotropic that the position of the first absorption peak monotonically blue-shifts as the strain applies to either direction for incident light polarized along the armchair direction, but this is not the case for that along the zigzag direction. Given those striking properties, we proposed two prototype devices for building potentially more balanced light absorbers and light filter passes, which promotes further applications and investigations of BP in nanoelectronics and optoelectronics.

  9. Impact of strain engineering on nanoscale strained InGaAs MOSFET devices.

    Science.gov (United States)

    Lee, Chang-Chun; Chang, Shu-Tong; Sun, P-H; Huang, C-X

    2011-07-01

    The strain distributions in the In(0.53)Ga(0.47)As channel regions of the In(0.4)Ga(0.6)As source/drain (S/D) with various lengths and widths were studied via 3D process simulations. The resulting mobility improvement was analyzed. The tensile strain along the transport direction was found to dominate the mobility improvement. The strain along the vertical direction perpendicular to the gate oxide was found to affect the mobility the least, while the strain along the width direction was slightly degraded. The impact of the channel width and length on the performance improvement, such as on the mobility gain, was analyzed via TCAD simulations. The novelty of this paper stems from its study of the impact of the channel width and length on the performance of InGaAs NMOSFETs, such as on their mobility gain, and from its exploration of physical insights for scaling the future III-V MOS devices. PMID:22121581

  10. Tuning Optical Conductivity of Large-Scale CVD Graphene by Strain Engineering

    OpenAIRE

    Ni, Guang-Xin; Yang, Hong-Zhi; Ji, Wei; Baeck, Seung-Jae; Toh, Chee-Tat; Ahn, Jong-Hyun; Pereira, Vitor M.; Özyilmaz, Barbaros

    2013-01-01

    Strain engineering has been recently recognized as an effective way to tailor the electrical properties of graphene. In the optical domain, effects such as strain-induced anisotropic absorption add an appealing functionality to graphene, opening the prospect for atomically thin optical elements. Indeed, graphene is currently one of the notable players in the intense drive towards bendable, thin, and portable electronic displays, where its intrinsically metallic, optically transparent, and mec...

  11. Biosynthesis of poly(3-hydroxypropionate) from glycerol using engineered Klebsiella pneumoniae strain without vitamin B12

    OpenAIRE

    Feng, Xinjun; Xian, Mo; Liu, Wei; Xu, Chao; Zhang, Haibo; Zhao, Guang

    2015-01-01

    Poly(3-hydroxypropionate) (P3HP) is a biodegradable and biocompatible thermoplastic. Previous studies demonstrated that engineered Escherichia coli strains can produce P3HP with supplementation of expensive vitamin B12. The present study examined the production of P3HP from glycerol in the recombinant Klebsiella pneumoniae strain, which naturally synthesizes vitamin B12. The genes glycerol dehydratase and its reactivation factor (dhaB123, gdrA, and gdrB from K. pneumoniae), aldehyde dehydroge...

  12. Strain engineering on structures and properties in ferroelectric thin films with perovskite structures

    Directory of Open Access Journals (Sweden)

    TANG Yanxue

    2015-08-01

    Full Text Available Ferroelectric thin films possess ferroelectric,piezoelectric,pyroelectric and photovoltaic properties,which have bright prospect for transducers,actuators,sensors,energy harvesting and solar cells.The properties of ferroelectric films are closely related to their strain due to films constrained by substrates.Therefore,the key to improve the properties of ferroelectric films is how to use substrates to regulate and control their strain,and then regulate their polarized state.This paper review the research progress of regulating the properties of ferroelectric films with perovskite structure by strain engineering and the problems needed to be resolved.

  13. Controlling thermal and electrical properties of graphene by strain-engineering its flexural phonons

    Science.gov (United States)

    Conley, Hiram; Nicholl, Ryan; Bolotin, Kirill

    2014-03-01

    We explore the effects of flexural phonons on the thermal and electrical properties of graphene. To control the amplitude of flexural phonons, we developed a technique to engineer uniform mechanical strain between 0 and 1% in suspended graphene. We determine the level of strain, thermal conductivity and carrier mobility of graphene through a combination of mechanical resonance and electrical transport measurements. Depending on strain, we find significant changes in the thermal expansion coefficient, thermal conductivity, and carrier mobility of suspended graphene. These changes are consistent with the expected contribution of flexural phonons.

  14. 微波诱变选育低产高级醇啤酒酵母菌株%Breeding of A Low-Yield of Higher Alcohols Saccharomyces Cerevisiae Strain by Microwave-Induced Mution

    Institute of Scientific and Technical Information of China (English)

    朱莉娜; 程殿林; 尹明浩; 王亚楠; 李静欣

    2011-01-01

    Higher alcohols is the by-product in the beer yeast fermentation process of normal metabolism, and the discretion of higher alcohols content has an important impact on beer flavor. In order to properly reduce beer higher alcohols and improve beer flavor, this experiment uses microwave mutation on saccha-romyces cerevisiae for a low-yield of higher alcohols strains. Saccharomyces cerevisiae strain CF - 1 was used as original strain for microwave-induced mutation and a low-yield of higher alcohols mutant strains were obtained through repeated selections. After genetic experiment of stability fermentation,it founds no fluctation of the yield of higher alcohols. Besides,the basic property of the mutant straiins has not changed greatly and they are the new strains of low-yield of higher alcohols.%高级醇是啤酒发酵过程中酵母正常代谢的副产物,高级醇质量分数的高低对啤酒风味有重要影响.为了适当地降低啤酒中高级醇的产量,改善啤酒的风味,采用微波诱变技术对啤酒酵母进行诱变.对出发菌株CF-1进行诱变处理,通过不同鉴别培养基进行反复筛选,得到高级醇产量低的目标菌株7种,经过遗传稳定性实验后进行发酵实验.实验结果表明,高级醇产量没有明显波动,且发现在基础性能测试中无较大差异,是适量低产高级醇啤酒酵母的新菌株.

  15. Engineering expression of the heavy metal transporter MerC in Saccharomyces cerevisiae for increased cadmium accumulation

    Energy Technology Data Exchange (ETDEWEB)

    Kiyono, Masako; Miyahara, Kiyomi; Sone, Yuka; Nakamura, Ryosuke; Sakabe, Kou [Kitasato Univ., Tokyo (Japan). Dept. of Public Health and Molecular Toxicology; Pan-Hou, Hidemitsu [Setsunan Univ., Osaka (Japan). Faculty of Pharmaceutical Sciences; Uraguchi, Shimpei [Tokyo Univ. (Japan). Biotechnology Research Center

    2010-03-15

    The merC gene from the Tn21-encoded mer operon has potential uses as a molecular tool for bioremediation. It was overexpressed as the fusion proteins MerC-Sso1p or MerC-Vam3p in Saccharomyces cerevisiae. Green fluorescent protein (GFP)-MerC-Sso1p fusion proteins located primarily in the plasma membrane, although some protein was detected in the endoplasmic reticulum. In contrast, GFP-MerC-Vam3p was expressed in the vacuolar membranes. These results suggest that yeast Sso1p and Vam3p are essential for targeting molecules to the plasma and vacuolar membranes, respectively. Significantly more cadmium ions were accumulated by yeast cells expressing MerC-Sso1p than with MerC-Vam3p or control cells. These results suggest that expression of MerC in the plasma membrane may be a particularly promising strategy for improving accumulation of cadmium in yeast. (orig.)

  16. Quantitative trait analysis of yeast biodiversity yields novel gene tools for metabolic engineering

    NARCIS (Netherlands)

    Hubmann, Georg; Foulquié-Moreno, Maria R.; Nevoigt, Elke; Duitama, Jorge; Meurens, Nicolas; Pais, Thiago M.; Mathé, Lotte; Saerens, Sofie; Nguyen, Huyen Thi Thanh; Swinnen, Steve; Verstrepen, Kevin J.; Concilio, Luigi; de Troostembergh, Jean-Claude; Thevelein, Johan M.

    2013-01-01

    Engineering of metabolic pathways by genetic modification has been restricted largely to enzyme-encoding structural genes. The product yield of such pathways is a quantitative genetic trait. Out of 52 Saccharomyces cerevisiae strains phenotyped in small-scale fermentations, we identified strain CBS6

  17. The combination of glycerol metabolic engineering and drug resistance marker-aided genome shuffling to improve very-high-gravity fermentation performances of industrial Saccharomyces cerevisiae.

    Science.gov (United States)

    Wang, Pin-Mei; Zheng, Dao-Qiong; Liu, Tian-Zhe; Tao, Xiang-Lin; Feng, Ming-Guang; Min, Hang; Jiang, Xin-Hang; Wu, Xue-Chang

    2012-03-01

    A challenge associated with the ethanol productivity under very-high-gravity (VHG) conditions, optimizing multi-traits (i.e. byproduct formation and stress tolerance) of industrial yeast strains, is overcome by a combination of metabolic engineering and genome shuffling. First, industrial strain Y12 was deleted with a glycerol exporter Fps1p and hetero-expressed with glyceraldehydes-3-phosphate dehydrogenase, resulting in the modified strain YFG12 with lower glycerol yield. Second, YFG12 was subjected to three rounds of drug resistance marker-aided genome shuffling to increase its ethanol tolerance, and the best shuffled strain TS5 was obtained. Compared with wild strain Y12, shuffled strain TS5 not only decreased glycerol formation by 14.8%, but also increased fermentation rate and ethanol yield by 3.7% and 7.6%, respectively. Moreover, the system of genetic modification and Cre/loxP in aid of three different drug-resistance markers presented in the study significantly improved breeding efficiency and will facilitate the application of breeding technologies in prototrophic industrial microorganisms.

  18. Characterizing Strain Variation in Engineered E. coli Using a Multi-Omics-Based Workflow.

    Science.gov (United States)

    Brunk, Elizabeth; George, Kevin W; Alonso-Gutierrez, Jorge; Thompson, Mitchell; Baidoo, Edward; Wang, George; Petzold, Christopher J; McCloskey, Douglas; Monk, Jonathan; Yang, Laurence; O'Brien, Edward J; Batth, Tanveer S; Martin, Hector Garcia; Feist, Adam; Adams, Paul D; Keasling, Jay D; Palsson, Bernhard O; Lee, Taek Soon

    2016-05-25

    Understanding the complex interactions that occur between heterologous and native biochemical pathways represents a major challenge in metabolic engineering and synthetic biology. We present a workflow that integrates metabolomics, proteomics, and genome-scale models of Escherichia coli metabolism to study the effects of introducing a heterologous pathway into a microbial host. This workflow incorporates complementary approaches from computational systems biology, metabolic engineering, and synthetic biology; provides molecular insight into how the host organism microenvironment changes due to pathway engineering; and demonstrates how biological mechanisms underlying strain variation can be exploited as an engineering strategy to increase product yield. As a proof of concept, we present the analysis of eight engineered strains producing three biofuels: isopentenol, limonene, and bisabolene. Application of this workflow identified the roles of candidate genes, pathways, and biochemical reactions in observed experimental phenomena and facilitated the construction of a mutant strain with improved productivity. The contributed workflow is available as an open-source tool in the form of iPython notebooks. PMID:27211860

  19. Comparisons of radiosensitivity and damage repair potential between mutants from the Saccharomyces cerevisiae strain of yeast and laboratory-bred wild yeasts with particular attention being given to giant cell formation after X-radiation. Strahlenempfindlichkeit und Erholungsvermoegen von Mutanten der Hefe Saccharomyces cerevisiae im Vergleich zu Wildtyphefen unter Beruecksichtigung der Riesenzellbildung nach Roentgenbestrahlung

    Energy Technology Data Exchange (ETDEWEB)

    Heinen, A.

    1988-06-01

    Yeast cells were exposed to X-rays at dose levels up to 10 kGy to induce damage to the DNA and investigate its effects on cellular growth patterns. For this purpose, comparisons were carried out between one diploid strain and six haploid strains of the Saccharomyces uvarum and Saccharomyces cerevisiae species, which permitted the individual recovery and damage repair pathways to be described in more detail. The laboratory-bred wild strains ATCC 9080, 211 and 706 were judged to have unimpaired repair mechanisms as compared to the auxotrophs, which fact was evident from the higher radiosensitivity of the latter. A further parameter in this evaluation of growth behaviours was giant cell formation. The results here provided evidence in confirmation of deviations between wild strains and mutants. Even though the ceiling values for the formation of giant cells were similarly high in all strains, impairments of cell division and initial development were observed for the mutants already at considerably lower dose levels. (orig./MG).

  20. Mechanical Self-Assembly of a Strain-Engineered Flexible Layer: Wrinkling, Rolling, and Twisting

    Science.gov (United States)

    Chen, Zi; Huang, Gaoshan; Trase, Ian; Han, Xiaomin; Mei, Yongfeng

    2016-01-01

    Self-shaping of curved structures, especially those involving flexible thin layers, is attracting increasing attention because of their broad potential applications in, e.g., nanoelectromechanical andmicroelectromechanical systems, sensors, artificial skins, stretchable electronics, robotics, and drug delivery. Here, we provide an overview of recent experimental, theoretical, and computational studies on the mechanical self-assembly of strain-engineered thin layers, with an emphasis on systems in which the competition between bending and stretching energy gives rise to a variety of deformations, such as wrinkling, rolling, and twisting. We address the principle of mechanical instabilities, which is often manifested in wrinkling or multistability of strain-engineered thin layers. The principles of shape selection and transition in helical ribbons are also systematically examined. We hope that a more comprehensive understanding of the mechanical principles underlying these rich phenomena can foster the development of techniques for manufacturing functional three-dimensional structures on demand for a broad spectrum of engineering applications.

  1. L-Histidine Inhibits Biofilm Formation and FLO11-Associated Phenotypes in Saccharomyces cerevisiae Flor Yeasts

    OpenAIRE

    Marc Bou Zeidan; Giacomo Zara; Carlo Viti; Francesca Decorosi; Ilaria Mannazzu; Marilena Budroni; Luciana Giovannetti; Severino Zara

    2014-01-01

    Flor yeasts of Saccharomyces cerevisiae have an innate diversity of Flo11p which codes for a highly hydrophobic and anionic cell-wall glycoprotein with a fundamental role in biofilm formation. In this study, 380 nitrogen compounds were administered to three S. cerevisiae flor strains handling Flo11p alleles with different expression levels. S. cerevisiae strain S288c was used as the reference strain as it cannot produce Flo11p. The flor strains generally metabolized amino acids and dipeptides...

  2. Effects of spaceflight on polysaccharides of Saccharomyces cerevisiae cell wall.

    Science.gov (United States)

    Liu, Hong-Zhi; Wang, Qiang; Liu, Xiao-Yong; Tan, Sze-Sze

    2008-12-01

    Freeze-dried samples of four Saccharomyces cerevisiae strains, namely, FL01, FL03, 2.0016, and 2.1424, were subjected to spaceflight. After the satellite's landing on Earth, the samples were recovered and changes in yeast cell wall were analyzed. Spaceflight strains of all S. cerevisiae strains showed significant changes in cell wall thickness (P growth curve analysis showed spaceflight S. cerevisiae 2.0016 had a faster growth rate, shorter lag phase periods, higher final biomass, and higher content of beta-glucan. Genetic stability analysis showed that prolonged subculturing of spaceflight strain S. cerevisiae 2.0016 did not lead to the appearance of variants, indicating that the genetic stability of S. cerevisiae 2.0016 mutant could be sufficient for its exploitation of beta-glucan production. PMID:18797865

  3. Strain-engineered diffusive atomic switching in two-dimensional crystals

    Science.gov (United States)

    Kalikka, Janne; Zhou, Xilin; Dilcher, Eric; Wall, Simon; Li, Ju; Simpson, Robert E.

    2016-06-01

    Strain engineering is an emerging route for tuning the bandgap, carrier mobility, chemical reactivity and diffusivity of materials. Here we show how strain can be used to control atomic diffusion in van der Waals heterostructures of two-dimensional (2D) crystals. We use strain to increase the diffusivity of Ge and Te atoms that are confined to 5 Å thick 2D planes within an Sb2Te3-GeTe van der Waals superlattice. The number of quintuple Sb2Te3 2D crystal layers dictates the strain in the GeTe layers and consequently its diffusive atomic disordering. By identifying four critical rules for the superlattice configuration we lay the foundation for a generalizable approach to the design of switchable van der Waals heterostructures. As Sb2Te3-GeTe is a topological insulator, we envision these rules enabling methods to control spin and topological properties of materials in reversible and energy efficient ways.

  4. Cell Surface Display of Four Types of Solanum nigrum Metallothionein on Saccharomyces cerevisiae for Biosorption of Cadmium.

    Science.gov (United States)

    Wei, Qinguo; Zhang, Honghai; Guo, Dongge; Ma, Shisheng

    2016-05-28

    We displayed four types of Solanum nigrum metallothionein (SMT) for the first time on the surface of Saccharomyces cerevisiae using an α-agglutinin-based display system. The SMT genes were amplified by RT-PCR. The plasmid pYES2 was used to construct the expression vector. Transformed yeast strains were confirmed by PCR amplification and custom sequencing. Surface-expressed metallothioneins were indirectly indicated by the enhanced cadmium sorption capacity. Flame atomic absorption spectrophotometry was used to examine the concentration of Cd(2+) in this study. The transformed yeast strains showed much higher resistance ability to Cd(2+) compared with the control. Strikingly, their Cd(2+) accumulation was almost twice as much as that of the wild-type yeast cells. Furthermore, surface-engineered yeast strains could effectively adsorb ultra-trace cadmium and accumulate Cd(2+) under a wide range of pH levels, from 3 to 7, without disturbing the Cu(2+) and Hg(2+). Four types of surfaceengineered Saccharomyces cerevisiae strains were constructed and they could be used to purify Cd(2+)-contaminated water and adsorb ultra-trace cadmium effectively. The surface-engineered Saccharomyces cerevisiae strains would be useful tools for the bioremediation and biosorption of environmental cadmium contaminants. PMID:26838339

  5. Electrostatic actuated strain engineering in monolithically integrated VLS grown silicon nanowires

    Science.gov (United States)

    Wagesreither, Stefan; Bertagnolli, Emmerich; Kawase, Shinya; Isono, Yoshitada; Lugstein, Alois

    2014-11-01

    In this paper we demonstrate the fabrication and application of an electrostatic actuated tensile straining test (EATEST) device enabling strain engineering in individual suspended nanowires (NWs). Contrary to previously reported approaches, this special setup guarantees the application of pure uniaxial tensile strain with no shear component of the stress while e.g. simultaneously measuring the resistance change of the NW. To demonstrate the potential of this approach we investigated the piezoresistivity of about 3 μm long and 100 nm thick SiNWs but in the same way one can think about the application of such a device on other geometries, other materials beyond Si as well as the use of other characterization techniques beyond electrical measurements. Therefore single-crystal SiNWs were monolithically integrated in a comb drive actuated MEMS device based on a silicon-on-insulator (SOI) wafer using the vapor-liquid-solid (VLS) growth technique. Strain values were verified by a precise measurement of the NW elongation with scanning electron microscopy (SEM). Further we employed confocal μ-Raman microscopy for in situ, high spatial resolution measurements of the strain in individual SiNWs during electrical characterization. A giant piezoresistive effect was observed, resulting in a fivefold increase in conductivity for 3% uniaxially strained SiNWs. As the EATEST approach can be easily integrated into an existing Si technology platform this architecture may pave the way toward a new generation of nonconventional devices by leveraging the strain degree of freedom.

  6. Improving Engineered Escherichia coli strains for High-level Biosynthesis of Isobutyrate

    Directory of Open Access Journals (Sweden)

    Mingyong Xiong

    2015-05-01

    Full Text Available Isobutyrate is an important platform chemical with various industrial applications. Previously, a synthetic metabolic pathway was constructed in E. coli to produce isobutyrate from glucose. However, isobutanol was found to be a major byproduct. Herein, gene knockouts and enzyme overexpressions were performed to optimize further the engineered E. coli strain. Besides yqhD, the knockouts of three genes eutG, yiaY and ygjB increased isobutyrate production in shake flasks. Furthermore, the introduction of an additional padA on a medium copy number plasmid under the constitutive promoter significantly reduced isobutanol formation. The IBA15-2C strain (BW25113, DyqhD, DygjB; carrying two copies of padA produced 39.2% more isobutyrate (0.39 g/glucose yield, 80% of the theoretical maximum yield than IBA1-1C strain (BW25113, DyqhD; carrying one copy of padA. A scale-up process was also investigated for IBA15-2C strain to optimize the conditions for the production of isobutyrate in the fermentor. With Ca(OH2 as the base for pH control and 10% dissolved oxygen level, IBA15-2C strain produced 90 g/L isobutyrate after 144 h. This study has engineered E. coli to achieve biosynthesis of a nonnative compound with the highest titer and opened up the possibility of the industrial production of isobutyrate.

  7. Electrically integrated SU-8 clamped graphene drum resonators for strain engineering

    Science.gov (United States)

    Lee, Sunwoo; Chen, Changyao; Deshpande, Vikram V.; Lee, Gwan-Hyoung; Lee, Ilkyu; Lekas, Michael; Gondarenko, Alexander; Yu, Young-Jun; Shepard, Kenneth; Kim, Philip; Hone, James

    2013-04-01

    Graphene mechanical resonators are the ultimate two-dimensional nanoelectromechanical systems (NEMS) with applications in sensing and signal processing. While initial devices have shown promising results, an ideal graphene NEMS resonator should be strain engineered, clamped at the edge without trapping gas underneath, and electrically integratable. In this Letter, we demonstrate fabrication and direct electrical measurement of circular SU-8 polymer-clamped chemical vapor deposition graphene drum resonators. The clamping increases device yield and responsivity, while providing a cleaner resonance spectrum from eliminated edge modes. Furthermore, the clamping induces a large strain in the resonator, increasing its resonant frequency.

  8. Engineering single-valley forward transport in strained graphene by magnetic-electric modulation

    Science.gov (United States)

    Wang, Yu

    2013-08-01

    Based on the distinct response of valley transport in graphene under the uniform strain, magnetic barrier, and electrostatic barrier manipulation, completely single-valley forward transport has been theoretically demonstrated by aligning deliberately the field profile of magnetic barrier and strain field. Further imposing electrostatic engineering, the receiving single-valley transport can be flexibly tuned to adapt much realistic field modulation, improve its ability to resist the temperature-induced thermal smooth, and even turn on or off this single-valley transport mode, displaying the appealing features for valleytronic device application.

  9. A vaccine grade of yeast Saccharomyces cerevisiae expressing mammalian myostatin

    Directory of Open Access Journals (Sweden)

    Zhang Tingting

    2012-12-01

    Full Text Available Abstract Background Yeast Saccharomyces cerevisiae is a widely-used system for protein expression. We previously showed that heat-killed whole recombinant yeast vaccine expressing mammalian myostatin can modulate myostatin function in mice, resulting in increase of body weight and muscle composition in these animals. Foreign DNA introduced into yeast cells can be lost soon unless cells are continuously cultured in selection media, which usually contain antibiotics. For cost and safety concerns, it is essential to optimize conditions to produce quality food and pharmaceutical products. Results We developed a simple but effective method to engineer a yeast strain stably expressing mammalian myostatin. This method utilized high-copy-number integration of myostatin gene into the ribosomal DNA of Saccharomyces cerevisiae. In the final step, antibiotic selection marker was removed using the Cre-LoxP system to minimize any possible side-effects for animals. The resulting yeast strain can be maintained in rich culture media and stably express mammalian myostatin for two years. Oral administration of the recombinant yeast was able to induce immune response to myostatin and modulated the body weight of mice. Conclusions Establishment of such yeast strain is a step further toward transformation of yeast cells into edible vaccine to improve meat production in farm animals and treat human muscle-wasting diseases in the future.

  10. Lycotoxin-1 insecticidal peptide optimized by amino acid scanning mutagenesis and expressed as a coproduct in an ethanologenic Saccharomyces cerevisiae strain.

    Science.gov (United States)

    Hughes, Stephen R; Dowd, Patrick F; Hector, Ronald E; Panavas, Tadas; Sterner, David E; Qureshi, Nasib; Bischoff, Kenneth M; Bang, Sookie S; Mertens, Jeffrey A; Johnson, Eric T; Li, Xin-Liang; Jackson, John S; Caughey, Robert J; Riedmuller, Steven B; Bartolett, Scott; Liu, Siqing; Rich, Joseph O; Farrelly, Philip J; Butt, Tauseef R; Labaer, Joshua; Cotta, Michael A

    2008-09-01

    New methods of safe biological pest control are required as a result of evolution of insect resistance to current biopesticides. Yeast strains being developed for conversion of cellulosic biomass to ethanol are potential host systems for expression of commercially valuable peptides, such as bioinsecticides, to increase the cost-effectiveness of the process. Spider venom is one of many potential sources of novel insect-specific peptide toxins. Libraries of mutants of the small amphipathic peptide lycotoxin-1 from the wolf spider were produced in high throughput using an automated integrated plasmid-based functional proteomic platform and screened for ability to kill fall armyworms, a significant cause of damage to corn (maize) and other crops in the United States. Using amino acid scanning mutagenesis (AASM) we generated a library of mutagenized lycotoxin-1 open reading frames (ORF) in a novel small ubiquitin-like modifier (SUMO) yeast expression system. The SUMO technology enhanced expression and improved generation of active lycotoxins. The mutants were engineered to be expressed at high level inside the yeast and ingested by the insect before being cleaved to the active form (so-called Trojan horse strategy). These yeast strains expressing mutant toxin ORFs were also carrying the xylose isomerase (XI) gene and were capable of aerobic growth on xylose. Yeast cultures expressing the peptide toxins were prepared and fed to armyworm larvae to identify the mutant toxins with greatest lethality. The most lethal mutations appeared to increase the ability of the toxin alpha-helix to interact with insect cell membranes or to increase its pore-forming ability, leading to cell lysis. The toxin peptides have potential as value-added coproducts to increase the cost-effectiveness of fuel ethanol bioproduction.

  11. Combining Protein and Strain Engineering for the Production of Glyco-Engineered Horseradish Peroxidase C1A in Pichia pastoris

    Directory of Open Access Journals (Sweden)

    Simona Capone

    2015-09-01

    Full Text Available Horseradish peroxidase (HRP, conjugated to antibodies and lectins, is widely used in medical diagnostics. Since recombinant production of the enzyme is difficult, HRP isolated from plant is used for these applications. Production in the yeast Pichia pastoris (P. pastoris, the most promising recombinant production platform to date, causes hyperglycosylation of HRP, which in turn complicates conjugation to antibodies and lectins. In this study we combined protein and strain engineering to obtain an active and stable HRP variant with reduced surface glycosylation. We combined four mutations, each being beneficial for either catalytic activity or thermal stability, and expressed this enzyme variant as well as the unmutated wildtype enzyme in both a P. pastoris benchmark strain and a strain where the native α-1,6-mannosyltransferase (OCH1 was knocked out. Considering productivity in the bioreactor as well as enzyme activity and thermal stability, the mutated HRP variant produced in the P. pastoris benchmark strain turned out to be interesting for medical diagnostics. This variant shows considerable catalytic activity and thermal stability and is less glycosylated, which might allow more controlled and efficient conjugation to antibodies and lectins.

  12. Hybrid orientation technology and strain engineering for ultra-high speed MOSFETs

    Indian Academy of Sciences (India)

    T K Maiti; C K Maiti

    2012-10-01

    We report here RF MOSFET performance in sub-45-nm hybrid orientation CMOS technology. Based on the combination of hybrid orientation technology (HOT) and process-induced local strain engineering,MOSFET RF performance is investigated using CAD (TCAD) technology. Transistor optimization on (100) substrate via silicon nitride (Si3N4) cap layer thickness for -MOSFETs, Ge mole fraction optimization for -MOSFETs on (110) substrates and channel length scaling have resulted in record RF performance, viz. the cut-off frequency, T.

  13. Recovery of succinic acid produced by fermentation of a metabolically engineered Mannheimia succiniciproducens strain.

    Science.gov (United States)

    Song, Hyohak; Huh, Yun Suk; Lee, Sang Yup; Hong, Won Hi; Hong, Yeon Ki

    2007-12-01

    There have recently been much advances in the production of succinic acid, an important four-carbon dicarboxylic acid for many industrial applications, by fermentation of several natural and engineered bacterial strains. Mannheimia succiniciproducens MBEL55E isolated from bovine rumen is able to produce succinic acid with high efficiency, but also produces acetic, formic and lactic acids just like other anaerobic succinic acid producers. We recently reported the development of an engineered M. succiniciproducens LPK7 strain which produces succinic acid as a major fermentation product while producing much reduced by-products. Having an improved succinic acid producer developed, it is equally important to develop a cost-effective downstream process for the recovery of succinic acid. In this paper, we report the development of a simpler and more efficient method for the recovery of succinic acid. For the recovery of succinic acid from the fermentation broth of LPK7 strain, a simple process composed of a single reactive extraction, vacuum distillation, and crystallization yielded highly purified succinic acid (greater than 99.5% purity, wt%) with a high yield of 67.05wt%. When the same recovery process or even multiple reactive extraction steps were applied to the fermentation broth of MBEL55E, lower purity and yield of succinic acid were obtained. These results suggest that succinic acid can be purified in a cost-effective manner by using the fermentation broth of engineered LPK7 strain, showing the importance of integrating the strain development, fermentation and downstream process for optimizing the whole processes for succinic acid production. PMID:17765349

  14. Room Temperature Semiconductor-Metal Transition of MoTe2 Thin Films Engineered by Strain.

    Science.gov (United States)

    Song, Seunghyun; Keum, Dong Hoon; Cho, Suyeon; Perello, David; Kim, Yunseok; Lee, Young Hee

    2016-01-13

    We demonstrate a room temperature semiconductor-metal transition in thin film MoTe2 engineered by strain. Reduction of the 2H-1T' phase transition temperature of MoTe2 to room temperature was realized by introducing a tensile strain of 0.2%. The observed first-order SM transition improved conductance ∼10 000 times and was made possible by an unusually large temperature-stress coefficient, which results from a large volume change and small latent heat. The demonstrated strain-modulation of the phase transition temperature is expected to be compatible with other TMDs enabling the 2D electronics utilizing polymorphism of TMDs along with the established materials. PMID:26713902

  15. Metabolic engineering of Corynebacterium glutamicum strain ATCC13032 to produce L-methionine.

    Science.gov (United States)

    Qin, Tianyu; Hu, Xiaoqing; Hu, Jinyu; Wang, Xiaoyuan

    2015-01-01

    L-Methionine-producing strain QW102/pJYW-4-hom(m) -lysC(m) -brnFE was developed from Corynebacterium glutamicum strain ATCC13032, using metabolic engineering strategies. These strategies involved (i) deletion of the gene thrB encoding homoserine kinase to increase the precursor supply, (ii) deletion of the gene mcbR encoding the regulator McbR to release the transcriptional repression to various genes in the l-methionine biosynthetic pathway, (iii) overexpression of the gene lysC(m) encoding feedback-resistant aspartate kinase and the gene hom(m) encoding feedback-resistant homoserine dehydrogenase to further increase the precursor supply, and (iv) overexpression of the gene cluster brnF and brnE encoding the export protein complex BrnFE to increase extracellular l-methionine concentration. QW102/pJYW-4-hom(m) -lysC(m) -brnFE produced 42.2 mM (6.3 g/L) l-methionine after 64-H fed-batch fermentation. These results suggest that l-methionine-producing strains can be developed from wild-type C. glutamicum strains by rationally metabolic engineering.

  16. Monolithically Integrated Microelectromechanical Systems for On-Chip Strain Engineering of Quantum Dots.

    Science.gov (United States)

    Zhang, Yang; Chen, Yan; Mietschke, Michael; Zhang, Long; Yuan, Feifei; Abel, Stefan; Hühne, Ruben; Nielsch, Kornelius; Fompeyrine, Jean; Ding, Fei; Schmidt, Oliver G

    2016-09-14

    Elastic strain fields based on single crystal piezoelectric elements represent an effective way for engineering the quantum dot (QD) emission with unrivaled precision and technological relevance. However, pioneering researches in this direction were mainly based on bulk piezoelectric substrates, which prevent the development of chip-scale devices. Here, we present a monolithically integrated Microelectromechanical systems (MEMS) device with great potential for on-chip quantum photonic applications. High-quality epitaxial PMN-PT thin films have been grown on SrTiO3 buffered Si and show excellent piezoelectric responses. Dense arrays of MEMS with small footprints are then fabricated based on these films, forming an on-chip strain tuning platform. After transferring the QD-containing nanomembranes onto these MEMS, the nonclassical emissions (e.g., single photons) from single QDs can be engineered by the strain fields. We envision that the strain tunable QD sources on the individually addressable and monolithically integrated MEMS pave the way toward complex quantum photonic applications on chip. PMID:27574953

  17. Synthesis and accumulation of aromatic aldehydes in an engineered strain of Escherichia coli.

    Science.gov (United States)

    Kunjapur, Aditya M; Tarasova, Yekaterina; Prather, Kristala L J

    2014-08-20

    Aromatic aldehydes are useful in numerous applications, especially as flavors, fragrances, and pharmaceutical precursors. However, microbial synthesis of aldehydes is hindered by rapid, endogenous, and redundant conversion of aldehydes to their corresponding alcohols. We report the construction of an Escherichia coli K-12 MG1655 strain with reduced aromatic aldehyde reduction (RARE) that serves as a platform for aromatic aldehyde biosynthesis. Six genes with reported activity on the model substrate benzaldehyde were rationally targeted for deletion: three genes that encode aldo-keto reductases and three genes that encode alcohol dehydrogenases. Upon expression of a recombinant carboxylic acid reductase in the RARE strain and addition of benzoate during growth, benzaldehyde remained in the culture after 24 h, with less than 12% conversion of benzaldehyde to benzyl alcohol. Although individual overexpression results demonstrated that all six genes could contribute to benzaldehyde reduction in vivo, additional experiments featuring subset deletion strains revealed that two of the gene deletions were dispensable under the conditions tested. The engineered strain was next investigated for the production of vanillin from vanillate and succeeded in preventing formation of the byproduct vanillyl alcohol. A pathway for the biosynthesis of vanillin directly from glucose was introduced and resulted in a 55-fold improvement in vanillin titer when using the RARE strain versus the wild-type strain. Finally, synthesis of the chiral pharmaceutical intermediate L-phenylacetylcarbinol (L-PAC) was demonstrated from benzaldehyde and glucose upon expression of a recombinant mutant pyruvate decarboxylase in the RARE strain. Beyond allowing accumulation of aromatic aldehydes as end products in E. coli, the RARE strain expands the classes of chemicals that can be produced microbially via aldehyde intermediates. PMID:25076127

  18. Tuning the optical, magnetic, and electrical properties of ReSe2 by nanoscale strain engineering.

    Science.gov (United States)

    Yang, Shengxue; Wang, Cong; Sahin, Hasan; Chen, Hui; Li, Yan; Li, Shu-Shen; Suslu, Aslihan; Peeters, Francois M; Liu, Qian; Li, Jingbo; Tongay, Sefaattin

    2015-03-11

    Creating materials with ultimate control over their physical properties is vital for a wide range of applications. From a traditional materials design perspective, this task often requires precise control over the atomic composition and structure. However, owing to their mechanical properties, low-dimensional layered materials can actually withstand a significant amount of strain and thus sustain elastic deformations before fracture. This, in return, presents a unique technique for tuning their physical properties by "strain engineering". Here, we find that local strain induced on ReSe2, a new member of the transition metal dichalcogenides family, greatly changes its magnetic, optical, and electrical properties. Local strain induced by generation of wrinkle (1) modulates the optical gap as evidenced by red-shifted photoluminescence peak, (2) enhances light emission, (3) induces magnetism, and (4) modulates the electrical properties. The results not only allow us to create materials with vastly different properties at the nanoscale, but also enable a wide range of applications based on 2D materials, including strain sensors, stretchable electrodes, flexible field-effect transistors, artificial-muscle actuators, solar cells, and other spintronic, electromechanical, piezoelectric, photonic devices.

  19. An internal deletion in MTH1 enables growth on glucose of pyruvate-decarboxylase negative, non-fermentative Saccharomyces cerevisiae

    Directory of Open Access Journals (Sweden)

    Oud Bart

    2012-09-01

    Full Text Available Abstract Background Pyruvate-decarboxylase negative (Pdc- strains of Saccharomyces cerevisiae combine the robustness and high glycolytic capacity of this yeast with the absence of alcoholic fermentation. This makes Pdc-S. cerevisiae an interesting platform for efficient conversion of glucose towards pyruvate-derived products without formation of ethanol as a by-product. However, Pdc- strains cannot grow on high glucose concentrations and require C2-compounds (ethanol or acetate for growth under conditions with low glucose concentrations, which hitherto has limited application in industry. Results Genetic analysis of a Pdc- strain previously evolved to overcome these deficiencies revealed a 225bp in-frame internal deletion in MTH1, encoding a transcriptional regulator involved in glucose sensing. This internal deletion contains a phosphorylation site required for degradation, thereby hypothetically resulting in increased stability of the protein. Reverse engineering of this alternative MTH1 allele into a non-evolved Pdc- strain enabled growth on 20 g l-1 glucose and 0.3% (v/v ethanol at a maximum specific growth rate (0.24 h-1 similar to that of the evolved Pdc- strain (0.23 h-1. Furthermore, the reverse engineered Pdc- strain grew on glucose as sole carbon source, albeit at a lower specific growth rate (0.10 h-1 than the evolved strain (0.20 h-1. The observation that overexpression of the wild-type MTH1 allele also restored growth of Pdc-S. cerevisiae on glucose is consistent with the hypothesis that the internal deletion results in decreased degradation of Mth1. Reduced degradation of Mth1 has been shown to result in deregulation of hexose transport. In Pdc- strains, reduced glucose uptake may prevent intracellular accumulation of pyruvate and/or redox problems, while release of glucose repression due to the MTH1 internal deletion may contribute to alleviation of the C2-compound auxotrophy. Conclusions In this study we have discovered and

  20. [Construction and evaluation of an engineered bacterial strain for producing lipopeptide under anoxic conditions].

    Science.gov (United States)

    Liang, Xiao-long; Zhao, Feng; Shi, Rong-jiu; Ban, Yun-he; Zhou, Ji-dong; Han, Si-qin; Zhang, Ying

    2015-08-01

    Biosurfactant-facilitated oil recovery is one of the most important aspects of microbial enhanced oil recovery (MEOR). However, the biosurfactant production by biosurfactant-producing microorganisms, most of which are aerobes, is severely suppressed due to the in-situ anoxic conditions within oil reservoirs. In this research, we successfully engineered a strain JD-3, which could grow rapidly and produce lipopeptide under anoxic conditions, by protoplast confusion using a Bacillus amyloliquefaciens strain BQ-2 which produces biosurfactant aerobically, and a facultative anaerobic Pseudomonas stutzeri strain DQ-1 as parent strains. The alignment of 16S rDNA sequence (99% similarity) and comparisons of cell colony morphology showed that fusant JD-3 was closer to the parental strain B. amyloliquefaciens BQ-2. The surface tension of culture broth of fusant JD-3, after 36-hour cultivation under anaerobic conditions, decreased from initially 63.0 to 32.5 mN · m(-1). The results of thin layer chromatography and infrared spectrum analysis demonstrated that the biosurfactant produced by JD-3 was lipopeptide. The surface-active lipopeptide had a low critical micelle concentration (CMC) of 90 mg · L(-1) and presented a good ability to emulsify various hydrocarbons such as crude oil, liquid paraffin, and kerosene. Strain JD-3 could utilize peptone as nitrogen source and sucrose, glucose, glycerin or other common organics as carbon sources for anaerobic lipopeptide synthesis. The subculture of fusant JD-3 showed a stable lipopeptide-producing ability even after ten serial passages. All these results indicated that fusant JD-3 holds a great potential to microbially enhance oil recovery under anoxic conditions. PMID:26685621

  1. Evaluation results of the 700 deg C Chinese strain gauges. [for gas turbine engine

    Science.gov (United States)

    Hobart, H. F.

    1985-01-01

    Gauges fabricated from specially developed Fe-Cr-Al-V-Ti-Y alloy wire in the Republic of China were evaluated for use in static strain measurement of hot gas turbine engines. Gauge factor variation with temperature, apparent strain, and drift were included. Results of gauge factor versus temperature tests show gauge factor decreasing with increasing temperature. The average slope is -3-1/2 percent/100 K, with an uncertainty band of + or - 8 percent. Values of room temperature gauge factor for the Chinese and Kanthal A-1 gauges averaged 2.73 and 2.12, respectively. The room temperature gauge factor of the Chinese gauges was specified to be 2.62. The apparent strain data for both the Chinese alloy and Kanthal A-1 showed large cycle to cycle nonrepeatability. All apparent strain curves had a similar S-shape, first going negative and then rising to positive value with increasing temperatures. The mean curve for the Chinese gauges between room temperature and 100 K had a total apparent strain of 1500 microstrain. The equivalent value for Kanthal A-1 was about 9000 microstrain. Drift tests at 950 K for 50 hr show an average drift rate of about -9 microstrain/hr. Short-term (1 hr) rates are higher, averaging about -40 microstrain for the first hour. In the temperature range 700 to 870 K, however, short-term drift rates can be as high as 1700 microstrain for the first hour. Therefore, static strain measurements in this temperature range should be avoided.

  2. Xylose Fermentation by Saccharomyces cerevisiae: Challenges and Prospects

    Directory of Open Access Journals (Sweden)

    Danuza Nogueira Moysés

    2016-02-01

    Full Text Available Many years have passed since the first genetically modified Saccharomyces cerevisiae strains capable of fermenting xylose were obtained with the promise of an environmentally sustainable solution for the conversion of the abundant lignocellulosic biomass to ethanol. Several challenges emerged from these first experiences, most of them related to solving redox imbalances, discovering new pathways for xylose utilization, modulation of the expression of genes of the non-oxidative pentose phosphate pathway, and reduction of xylitol formation. Strategies on evolutionary engineering were used to improve fermentation kinetics, but the resulting strains were still far from industrial application. Lignocellulosic hydrolysates proved to have different inhibitors derived from lignin and sugar degradation, along with significant amounts of acetic acid, intrinsically related with biomass deconstruction. This, associated with pH, temperature, high ethanol, and other stress fluctuations presented on large scale fermentations led the search for yeasts with more robust backgrounds, like industrial strains, as engineering targets. Some promising yeasts were obtained both from studies of stress tolerance genes and adaptation on hydrolysates. Since fermentation times on mixed-substrate hydrolysates were still not cost-effective, the more selective search for new or engineered sugar transporters for xylose are still the focus of many recent studies. These challenges, as well as under-appreciated process strategies, will be discussed in this review.

  3. Xylose Fermentation by Saccharomyces cerevisiae: Challenges and Prospects.

    Science.gov (United States)

    Moysés, Danuza Nogueira; Reis, Viviane Castelo Branco; de Almeida, João Ricardo Moreira; de Moraes, Lidia Maria Pepe; Torres, Fernando Araripe Gonçalves

    2016-01-01

    Many years have passed since the first genetically modified Saccharomyces cerevisiae strains capable of fermenting xylose were obtained with the promise of an environmentally sustainable solution for the conversion of the abundant lignocellulosic biomass to ethanol. Several challenges emerged from these first experiences, most of them related to solving redox imbalances, discovering new pathways for xylose utilization, modulation of the expression of genes of the non-oxidative pentose phosphate pathway, and reduction of xylitol formation. Strategies on evolutionary engineering were used to improve fermentation kinetics, but the resulting strains were still far from industrial application. Lignocellulosic hydrolysates proved to have different inhibitors derived from lignin and sugar degradation, along with significant amounts of acetic acid, intrinsically related with biomass deconstruction. This, associated with pH, temperature, high ethanol, and other stress fluctuations presented on large scale fermentations led the search for yeasts with more robust backgrounds, like industrial strains, as engineering targets. Some promising yeasts were obtained both from studies of stress tolerance genes and adaptation on hydrolysates. Since fermentation times on mixed-substrate hydrolysates were still not cost-effective, the more selective search for new or engineered sugar transporters for xylose are still the focus of many recent studies. These challenges, as well as under-appreciated process strategies, will be discussed in this review. PMID:26927067

  4. High level secretion of cellobiohydrolases by Saccharomyces cerevisiae

    Directory of Open Access Journals (Sweden)

    Ahlgren Simon

    2011-09-01

    Full Text Available Abstract Background The main technological impediment to widespread utilization of lignocellulose for the production of fuels and chemicals is the lack of low-cost technologies to overcome its recalcitrance. Organisms that hydrolyze lignocellulose and produce a valuable product such as ethanol at a high rate and titer could significantly reduce the costs of biomass conversion technologies, and will allow separate conversion steps to be combined in a consolidated bioprocess (CBP. Development of Saccharomyces cerevisiae for CBP requires the high level secretion of cellulases, particularly cellobiohydrolases. Results We expressed various cellobiohydrolases to identify enzymes that were efficiently secreted by S. cerevisiae. For enhanced cellulose hydrolysis, we engineered bimodular derivatives of a well secreted enzyme that naturally lacks the carbohydrate-binding module, and constructed strains expressing combinations of cbh1 and cbh2 genes. Though there was significant variability in the enzyme levels produced, up to approximately 0.3 g/L CBH1 and approximately 1 g/L CBH2 could be produced in high cell density fermentations. Furthermore, we could show activation of the unfolded protein response as a result of cellobiohydrolase production. Finally, we report fermentation of microcrystalline cellulose (Avicel™ to ethanol by CBH-producing S. cerevisiae strains with the addition of beta-glucosidase. Conclusions Gene or protein specific features and compatibility with the host are important for efficient cellobiohydrolase secretion in yeast. The present work demonstrated that production of both CBH1 and CBH2 could be improved to levels where the barrier to CBH sufficiency in the hydrolysis of cellulose was overcome.

  5. Metabolic engineering of a reduced-genome strain of Escherichia coli for L-threonine production

    Directory of Open Access Journals (Sweden)

    Yoon Byoung

    2009-01-01

    Full Text Available Abstract Background Deletion of large blocks of nonessential genes that are not needed for metabolic pathways of interest can reduce the production of unwanted by-products, increase genome stability, and streamline metabolism without physiological compromise. Researchers have recently constructed a reduced-genome Escherichia coli strain MDS42 that lacks 14.3% of its chromosome. Results Here we describe the reengineering of the MDS42 genome to increase the production of the essential amino acid L-threonine. To this end, we over-expressed a feedback-resistant threonine operon (thrA*BC, deleted the genes that encode threonine dehydrogenase (tdh and threonine transporters (tdcC and sstT, and introduced a mutant threonine exporter (rhtA23 in MDS42. The resulting strain, MDS-205, shows an ~83% increase in L-threonine production when cells are grown by flask fermentation, compared to a wild-type E. coli strain MG1655 engineered with the same threonine-specific modifications described above. And transcriptional analysis revealed the effect of the deletion of non-essential genes on the central metabolism and threonine pathways in MDS-205. Conclusion This result demonstrates that the elimination of genes unnecessary for cell growth can increase the productivity of an industrial strain, most likely by reducing the metabolic burden and improving the metabolic efficiency of cells.

  6. Strain-engineered diffusive atomic switching in two-dimensional crystals

    Science.gov (United States)

    Kalikka, Janne; Zhou, Xilin; Dilcher, Eric; Wall, Simon; Li, Ju; Simpson, Robert E.

    2016-01-01

    Strain engineering is an emerging route for tuning the bandgap, carrier mobility, chemical reactivity and diffusivity of materials. Here we show how strain can be used to control atomic diffusion in van der Waals heterostructures of two-dimensional (2D) crystals. We use strain to increase the diffusivity of Ge and Te atoms that are confined to 5 Å thick 2D planes within an Sb2Te3–GeTe van der Waals superlattice. The number of quintuple Sb2Te3 2D crystal layers dictates the strain in the GeTe layers and consequently its diffusive atomic disordering. By identifying four critical rules for the superlattice configuration we lay the foundation for a generalizable approach to the design of switchable van der Waals heterostructures. As Sb2Te3–GeTe is a topological insulator, we envision these rules enabling methods to control spin and topological properties of materials in reversible and energy efficient ways. PMID:27329563

  7. Exopolysaccharide production by a genetically engineered Enterobacter cloacae strain for microbial enhanced oil recovery.

    Science.gov (United States)

    Sun, Shanshan; Zhang, Zhongzhi; Luo, Yijing; Zhong, Weizhang; Xiao, Meng; Yi, Wenjing; Yu, Li; Fu, Pengcheng

    2011-05-01

    Microbial enhanced oil recovery (MEOR) is a petroleum biotechnology for manipulating function and/or structure of microbial environments existing in oil reservoirs for prolonged exploitation of the largest source of energy. In this study, an Enterobacter cloacae which is capable of producing water-insoluble biopolymers at 37°C and a thermophilic Geobacillus strain were used to construct an engineered strain for exopolysaccharide production at higher temperature. The resultant transformants, GW3-3.0, could produce exopolysaccharide up to 8.83 g l(-1) in molasses medium at 54°C. This elevated temperature was within the same temperature range as that for many oil reservoirs. The transformants had stable genetic phenotype which was genetically fingerprinted by RAPD analysis. Core flooding experiments were carried out to ensure effective controlled profile for the simulation of oil recovery. The results have demonstrated that this approach has a promising application potential in MEOR. PMID:21444201

  8. Overexpressing enzymes of the Ehrlich pathway and deleting genes of the competing pathway in Saccharomyces cerevisiae for increasing 2-phenylethanol production from glucose.

    Science.gov (United States)

    Shen, Li; Nishimura, Yuya; Matsuda, Fumio; Ishii, Jun; Kondo, Akihiko

    2016-07-01

    2-Phenylethanol (2-PE) is a higher aromatic alcohol that is used in the cosmetics and food industries. The budding yeast Saccharomyces cerevisiae is considered to be a suitable host for the industrial production of higher alcohols, including 2-PE. To produce 2-PE from glucose in S. cerevisiae, we searched for suitable 2-keto acid decarboxylase (KDC) and alcohol dehydrogenase (ADH) enzymes of the Ehrlich pathway for overexpression in strain YPH499, and found that overexpression of the ARO10 and/or ADH1 genes increased 2-PE production from glucose. Further, we screened ten BY4741 single-deletion mutants of genes involved in the competing pathways for 2-PE production, and found that strains aro8Δ and aat2Δ displayed increased 2-PE production. Based on these results, we engineered a BY4741 strain that overexpressed ARO10 and contained an aro8Δ deletion, and demonstrated that the strain produced 96 mg/L 2-PE from glucose as the sole carbon source. As this engineered S. cerevisiae strain showed a significant increase in 2-PE production from glucose without the addition of an intermediate carbon substrate, it is a promising candidate for the large-scale production of 2-PE. PMID:26975754

  9. Systems biology and pathway engineering enable Saccharomyces cerevisiae to utilize C-5 and C-6 sugars simultaneously for cellulosic ethanol production

    Science.gov (United States)

    Saccharomyces cerevisiae is a traditional industrial workhorse for ethanol production. However, conventional ethanologenic yeast is superior in fermentation of hexose sugars (C-6) such as glucose but unable to utilize pentose sugars (C-5) such as xylose richly embedded in lignocellulosic biomass. In...

  10. Engineering of a plasmid-free Escherichia coli strain for improved in vivo biosynthesis of astaxanthin

    Directory of Open Access Journals (Sweden)

    Steuer Kristin

    2011-04-01

    Full Text Available Abstract Background The xanthophyll astaxanthin is a high-value compound with applications in the nutraceutical, cosmetic, food, and animal feed industries. Besides chemical synthesis and extraction from naturally producing organisms like Haematococcus pluvialis, heterologous biosynthesis in non-carotenogenic microorganisms like Escherichia coli, is a promising alternative for sustainable production of natural astaxanthin. Recent achievements in the metabolic engineering of E. coli strains have led to a significant increase in the productivity of carotenoids like lycopene or β-carotene by increasing the metabolic flux towards the isoprenoid precursors. For the heterologous biosynthesis of astaxanthin in E. coli, however, the conversion of β-carotene to astaxanthin is obviously the most critical step towards an efficient biosynthesis of astaxanthin. Results Here we report the construction of the first plasmid-free E. coli strain that produces astaxanthin as the sole carotenoid compound with a yield of 1.4 mg/g cdw (E. coli BW-ASTA. This engineered E. coli strain harbors xanthophyll biosynthetic genes from Pantoea ananatis and Nostoc punctiforme as individual expression cassettes on the chromosome and is based on a β-carotene-producing strain (E. coli BW-CARO recently developed in our lab. E. coli BW-CARO has an enhanced biosynthesis of the isoprenoid precursor isopentenyl diphosphate (IPP and produces β-carotene in a concentration of 6.2 mg/g cdw. The expression of crtEBIY along with the β-carotene-ketolase gene crtW148 (NpF4798 and the β-carotene-hydroxylase gene (crtZ under controlled expression conditions in E. coli BW-ASTA directed the pathway exclusively towards the desired product astaxanthin (1.4 mg/g cdw. Conclusions By using the λ-Red recombineering technique, genes encoding for the astaxanthin biosynthesis pathway were stably integrated into the chromosome of E. coli. The expression levels of chromosomal integrated recombinant

  11. Strain engineering of selective chemical adsorption on monolayer MoS2

    Science.gov (United States)

    Kou, Liangzhi; Du, Aijun; Chen, Changfeng; Frauenheim, Thomas

    2014-04-01

    Nanomaterials are prone to influence by chemical adsorption because of their large surface to volume ratios. This enables sensitive detection of adsorbed chemical species which, in turn, can tune the properties of the host material. Recent studies discovered that single and multi-layer molybdenum disulfide (MoS2) films are ultra-sensitive to several important environmental molecules. Here we report new findings from ab inito calculations that reveal substantially enhanced adsorption of NO and NH3 on strained monolayer MoS2 with significant impact on the properties of the adsorbates and the MoS2 layer. The magnetic moment of adsorbed NO can be tuned between 0 and 1 μB strain also induces an electronic phase transition between the half-metal and the metal. Adsorption of NH3 weakens the MoS2 layer considerably, which explains the large discrepancy between the experimentally measured strength and breaking strain of MoS2 films and previous theoretical predictions. On the other hand, adsorption of NO2, CO, and CO2 is insensitive to the strain conditions in the MoS2 layer. This contrasting behavior allows sensitive strain engineering of selective chemical adsorption on MoS2 with effective tuning of mechanical, electronic, and magnetic properties. These results suggest new design strategies for constructing MoS2-based ultrahigh-sensitivity nanoscale sensors and electromechanical devices.Nanomaterials are prone to influence by chemical adsorption because of their large surface to volume ratios. This enables sensitive detection of adsorbed chemical species which, in turn, can tune the properties of the host material. Recent studies discovered that single and multi-layer molybdenum disulfide (MoS2) films are ultra-sensitive to several important environmental molecules. Here we report new findings from ab inito calculations that reveal substantially enhanced adsorption of NO and NH3 on strained monolayer MoS2 with significant impact on the properties of the adsorbates and the

  12. MoS2/MX2 heterobilayers: bandgap engineering via tensile strain or external electrical field

    Science.gov (United States)

    Lu, Ning; Guo, Hongyan; Li, Lei; Dai, Jun; Wang, Lu; Mei, Wai-Ning; Wu, Xiaojun; Zeng, Xiao Cheng

    2014-02-01

    We have performed a comprehensive first-principles study of the electronic and magnetic properties of two-dimensional (2D) transition-metal dichalcogenide (TMD) heterobilayers MX2/MoS2 (M = Mo, Cr, W, Fe, V; X = S, Se). For M = Mo, Cr, W; X = S, Se, all heterobilayers show semiconducting characteristics with an indirect bandgap with the exception of the WSe2/MoS2 heterobilayer which retains the direct-bandgap character of the constituent monolayer. For M = Fe, V; X = S, Se, the MX2/MoS2 heterobilayers exhibit metallic characters. Particular attention of this study has been focused on engineering the bandgap of the TMD heterobilayer materials via application of either a tensile strain or an external electric field. We find that with increasing either the biaxial or uniaxial tensile strain, the MX2/MoS2 (M = Mo, Cr, W; X = S, Se) heterobilayers can undergo a semiconductor-to-metal transition. For the WSe2/MoS2 heterobilayer, a direct-to-indirect bandgap transition may occur beyond a critical biaxial or uniaxial strain. For M (=Fe, V) and X (=S, Se), the magnetic moments of both metal and chalcogen atoms are enhanced when the MX2/MoS2 heterobilayers are under a biaxial tensile strain. Moreover, the bandgap of MX2/MoS2 (M = Mo, Cr, W; X = S, Se) heterobilayers can be reduced by the vertical electric field. For two heterobilayers MSe2/MoS2 (M = Mo, Cr), PBE calculations suggest that the indirect-to-direct bandgap transition may occur under an external electric field. The transition is attributed to the enhanced spontaneous polarization. The tunable bandgaps in general and possible indirect-direct bandgap transitions due to tensile strain or external electric field make the TMD heterobilayer materials a viable candidate for optoelectronic applications.We have performed a comprehensive first-principles study of the electronic and magnetic properties of two-dimensional (2D) transition-metal dichalcogenide (TMD) heterobilayers MX2/MoS2 (M = Mo, Cr, W, Fe, V; X = S, Se). For

  13. Engineered measles virus Edmonston strain used as a novel oncolytic viral system against human hepatoblastoma

    International Nuclear Information System (INIS)

    Hepatoblastoma (HB) is the most common primary, malignant pediatric liver tumor in children. The treatment results for affected children have markedly improved in recent decades. However, the prognosis for high-risk patients who have extrahepatic extensions, invasion of the large hepatic veins, distant metastases and very high alpha-fetoprotein (AFP) serum levels remains poor. There is an urgent need for the development of novel therapeutic approaches. An attenuated strain of measles virus, derived from the Edmonston vaccine lineage, was genetically engineered to produce carcinoembryonic antigen (CEA). We investigated the antitumor potential of this novel viral agent against human HB both in vitro and in vivo. Infection of the Hep2G and HUH6 HB cell lines, at multiplicities of infection (MOIs) ranging from 0.01 to 1, resulted in a significant cytopathic effect consisting of extensive syncytia formation and massive cell death at 72–96 h after infection. Both of the HB lines overexpressed the measles virus receptor CD46 and supported robust viral replication, which correlated with CEA production. The efficacy of this approach in vivo was examined in murine Hep2G xenograft models. Flow cytometry assays indicated an apoptotic mechanism of cell death. Intratumoral administration of MV-CEA resulted in statistically significant delay of tumor growth and prolongation of survival. The engineered measles virus Edmonston strain MV-CEA has potent therapeutic efficacy against HB cell lines and xenografts. Trackable measles virus derivatives merit further exploration in HB treatment

  14. 利用原生质体融合技术构建梨酒酵母工程菌%Study on construction of yeast engineering strain for pear wine by protoplast fusion method

    Institute of Scientific and Technical Information of China (English)

    张大为; 张洁; 洪磊东; 金磊; 高健; 梁芳

    2013-01-01

    The yeast engineering strain was structured by the protoplast fusion technology. Saccharomyces cerevisiae YDJ05 and Issatchenkia orientalis YS03 were used as the fusion parents X and Y.A arginine nutrition unfairness strain was selected by EMS mutagenesis from parents strains Y.The strains X and Y were dealt with the snail enzyme liquid in 35℃ for 100min.The best protoplast formation rate and regeneration rate were 93.6% ,94.2% and 27.8% ,31.6%,Inactivate strains of the parents of X with heating them in 14mialn the circumstance with PEG as promotion melting agent DJ01~ DJ06 six strains fusant were gotten, one of them DJ02 with the best alcohol producting rate and aroma producting rate were reached to 9.87% and 0.37g/L.%以菌株酿酒酵母Saccharomyces cerevisiae YDJ05及产香酵母Issatchenkia orientalis YS03为融合亲本X和Y,通过原生质体融合技术构建适合梨酒酿造的酵母工程菌,研究结果表明:利用EMS诱变亲本菌株Y,得到了一株精氨酸营养缺陷型菌株,亲本菌株X和Y采用蜗牛酶液在35℃下处理100min,得到菌株X、Y的原生质体融合率分别为93.6%、94.2%,再生率分别为27.8%、31.6%.以加热的方式灭活亲本菌株X,灭活时间为14min.在以PEG为促融剂的条件下对两株菌进行原生质体融合,经过优选得到融合子D J02,其产酒精率、产香率等指标最优,分别达到了9.87%、0.37g/L.

  15. Controlling the thermal conductance of graphene/h -BN lateral interface with strain and structure engineering

    Science.gov (United States)

    Ong, Zhun-Yong; Zhang, Gang; Zhang, Yong-Wei

    2016-02-01

    Although phonon-mediated thermal conduction in pristine graphene and hexagonal boron nitride is well understood, less is known about phonon transport in single-sheet graphene-hexagonal boron nitride (Gr /h -BN ) lateral heterostructures, where the thermal resistance of the interfaces plays an important role in the overall thermal conductivity. We apply the newly developed extended atomistic Green's function method to analyze with detail the effect of strain and structure engineering on the thermal conductance Gint of the Gr /h -BN interface. Our calculations show that longitudinal tensile strain leads to significant Gint enhancement (up to 25 % at 300 K) primarily through the improved alignment of the flexural acoustic phonon bands, despite the reduction in the longitudinal acoustic (LA) and transverse acoustic phonon velocities. In addition, we find that alternating C-N zigzag bonds along the zigzag interface lead to a greater Gint than C-B bonds through more effective transmission of high-frequency LA and transverse optical phonons, especially at high strain levels. We also demonstrate how the interfacial structure dramatically affects the orientation of the transmitted optical phonons, a phenomenon that is neither seen for acoustic phonons nor predictable from conventional acoustic wave scattering theory. Insights from our paper can provide the basis for manipulating the interfacial thermal conductance in other two-dimensional heterostructures.

  16. Strong Modulation of Optical Properties in Black Phosphorus through Strain-Engineered Rippling.

    Science.gov (United States)

    Quereda, Jorge; San-Jose, Pablo; Parente, Vincenzo; Vaquero-Garzon, Luis; Molina-Mendoza, Aday J; Agraït, Nicolás; Rubio-Bollinger, Gabino; Guinea, Francisco; Roldán, Rafael; Castellanos-Gomez, Andres

    2016-05-11

    Controlling the bandgap through local-strain engineering is an exciting avenue for tailoring optoelectronic materials. Two-dimensional crystals are particularly suited for this purpose because they can withstand unprecedented nonhomogeneous deformations before rupture; one can literally bend them and fold them up almost like a piece of paper. Here, we study multilayer black phosphorus sheets subjected to periodic stress to modulate their optoelectronic properties. We find a remarkable shift of the optical absorption band-edge of up to ∼0.7 eV between the regions under tensile and compressive stress, greatly exceeding the strain tunability reported for transition metal dichalcogenides. This observation is supported by theoretical models that also predict that this periodic stress modulation can yield to quantum confinement of carriers at low temperatures. The possibility of generating large strain-induced variations in the local density of charge carriers opens the door for a variety of applications including photovoltaics, quantum optics, and two-dimensional optoelectronic devices. PMID:27042865

  17. Wrinkling instability in nanoparticle-supported graphene: implications for strain engineering

    Science.gov (United States)

    Cullen, William; Yamamoto, Mahito; Pierre-Louis, Olivier; Huang, Jia; Fuhrer, Michael; Einstein, Theodore

    2013-03-01

    We have carried out a systematic study of the wrinkling instability of graphene membranes supported on SiO2 substrates with randomly placed silica nanoparticles. At small nanoparticle density, monolayer graphene adheres to the substrate and is highly conformal over the nanoparticles. With increasing nanoparticle density, and decreasing nanoparticle separation to ~100 nm, graphene's elastic response dominates substrate adhesion, and elastic stretching energy is reduced by the formation of wrinkles which connect protrusions. Above a critical nanoparticle density, the wrinkles form a percolating network through the sample. As the graphene membrane is made thicker, delamination from the substrate is observed. Since the wrinkling instability acts to remove inhomogeneous in-plane elastic strains through out-of-plane buckling, our results can be used to place limits on the possible in-plane strain magnitudes that may be created in graphene to realized strain-engineered electronic structures.[2] Supported by the UMD NSF-MRSEC under Grant No. DMR 05-20471, the US ONR MURI and UMD CNAM.

  18. Genomic landscapes of endogenous retroviruses unveil intricate genetics of conventional and genetically-engineered laboratory mouse strains.

    Science.gov (United States)

    Lee, Kang-Hoon; Lim, Debora; Chiu, Sophia; Greenhalgh, David; Cho, Kiho

    2016-04-01

    Laboratory strains of mice, both conventional and genetically engineered, have been introduced as critical components of a broad range of studies investigating normal and disease biology. Currently, the genetic identity of laboratory mice is primarily confirmed by surveying polymorphisms in selected sets of "conventional" genes and/or microsatellites in the absence of a single completely sequenced mouse genome. First, we examined variations in the genomic landscapes of transposable repetitive elements, named the TREome, in conventional and genetically engineered mouse strains using murine leukemia virus-type endogenous retroviruses (MLV-ERVs) as a probe. A survey of the genomes from 56 conventional strains revealed strain-specific TREome landscapes, and certain families (e.g., C57BL) of strains were discernible with defined patterns. Interestingly, the TREome landscapes of C3H/HeJ (toll-like receptor-4 [TLR4] mutant) inbred mice were different from its control C3H/HeOuJ (TLR4 wild-type) strain. In addition, a CD14 knock-out strain had a distinct TREome landscape compared to its control/backcross C57BL/6J strain. Second, an examination of superantigen (SAg, a "TREome gene") coding sequences of mouse mammary tumor virus-type ERVs in the genomes of the 46 conventional strains revealed a high diversity, suggesting a potential role of SAgs in strain-specific immune phenotypes. The findings from this study indicate that unexplored and intricate genomic variations exist in laboratory mouse strains, both conventional and genetically engineered. The TREome-based high-resolution genetics surveillance system for laboratory mice would contribute to efficient study design with quality control and accurate data interpretation. This genetics system can be easily adapted to other species ranging from plants to humans.

  19. Genetically engineered immunomodulatory Streptococcus thermophilus strains producing antioxidant enzymes exhibit enhanced anti-inflammatory activities.

    Science.gov (United States)

    Del Carmen, Silvina; de Moreno de LeBlanc, Alejandra; Martin, Rebeca; Chain, Florian; Langella, Philippe; Bermúdez-Humarán, Luis G; LeBlanc, Jean Guy

    2014-02-01

    The aims of this study were to develop strains of lactic acid bacteria (LAB) having both immunomodulatory and antioxidant properties and to evaluate their anti-inflammatory effects both in vitro, in different cellular models, and in vivo, in a mouse model of colitis. Different Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus strains were cocultured with primary cultures of mononuclear cells. Analysis of the pro- and anti-inflammatory cytokines secreted by these cells after coincubation with candidate bacteria revealed that L. delbrueckii subsp. bulgaricus CRL 864 and S. thermophilus CRL 807 display the highest anti-inflammatory profiles in vitro. Moreover, these results were confirmed in vivo by the determination of the cytokine profiles in large intestine samples of mice fed with these strains. S. thermophilus CRL 807 was then transformed with two different plasmids harboring the genes encoding catalase (CAT) or superoxide dismutase (SOD) antioxidant enzymes, and the anti-inflammatory effects of recombinant streptococci were evaluated in a mouse model of colitis induced by trinitrobenzenesulfonic acid (TNBS). Our results showed a decrease in weight loss, lower liver microbial translocation, lower macroscopic and microscopic damage scores, and modulation of the cytokine production in the large intestines of mice treated with either CAT- or SOD-producing streptococci compared to those in mice treated with the wild-type strain or control mice without any treatment. Furthermore, the greatest anti-inflammatory activity was observed in mice receiving a mixture of both CAT- and SOD-producing streptococci. The addition of L. delbrueckii subsp. bulgaricus CRL 864 to this mixture did not improve their beneficial effects. These findings show that genetically engineering a candidate bacterium (e.g., S. thermophilus CRL 807) with intrinsic immunomodulatory properties by introducing a gene expressing an antioxidant enzyme enhances its anti

  20. Metabolic transcription analysis of engineered Escherichia coli strains that overproduce L-phenylalanine

    Directory of Open Access Journals (Sweden)

    Gosset Guillermo

    2007-09-01

    Full Text Available Abstract Background The rational design of L-phenylalanine (L-Phe overproducing microorganisms has been successfully achieved by combining different genetic strategies such as inactivation of the phosphoenolpyruvate: phosphotransferase transport system (PTS and overexpression of key genes (DAHP synthase, transketolase and chorismate mutase-prephenate dehydratase, reaching yields of 0.33 (g-Phe/g-Glc, which correspond to 60% of theoretical maximum. Although genetic modifications introduced into the cell for the generation of overproducing organisms are specifically targeted to a particular pathway, these can trigger unexpected transcriptional responses of several genes. In the current work, metabolic transcription analysis (MTA of both L-Phe overproducing and non-engineered strains using Real-Time PCR was performed, allowing the detection of transcriptional responses to PTS deletion and plasmid presence of genes related to central carbon metabolism. This MTA included 86 genes encoding enzymes of glycolysis, gluconeogenesis, pentoses phosphate, tricarboxylic acid cycle, fermentative and aromatic amino acid pathways. In addition, 30 genes encoding regulatory proteins and transporters for aromatic compounds and carbohydrates were also analyzed. Results MTA revealed that a set of genes encoding carbohydrate transporters (galP, mglB, gluconeogenic (ppsA, pckA and fermentative enzymes (ldhA were significantly induced, while some others were down-regulated such as ppc, pflB, pta and ackA, as a consequence of PTS inactivation. One of the most relevant findings was the coordinated up-regulation of several genes that are exclusively gluconeogenic (fbp, ppsA, pckA, maeB, sfcA, and glyoxylate shunt in the best PTS- L-Phe overproducing strain (PB12-ev2. Furthermore, it was noticeable that most of the TCA genes showed a strong up-regulation in the presence of multicopy plasmids by an unknown mechanism. A group of genes exhibited transcriptional responses to

  1. Display of phytase on the cell surface of Saccharomyces cerevisiae to degrade phytate phosphorus and improve bioethanol production.

    Science.gov (United States)

    Chen, Xianzhong; Xiao, Yan; Shen, Wei; Govender, Algasan; Zhang, Liang; Fan, You; Wang, Zhengxiang

    2016-03-01

    Currently, development of biofuels as an alternative fuel has gained much attention due to resource and environmental challenges. Bioethanol is one of most important and dominant biofuels, and production using corn or cassava as raw materials has become a prominent technology. However, phytate contained in the raw material not only decreases the efficiency of ethanol production, but also leads to an increase in the discharge of phosphorus, thus impacting on the environment. In this study, to decrease phytate and its phosphorus content in an ethanol fermentation process, Saccharomyces cerevisiae was engineered through a surface-displaying system utilizing the C-terminal half of the yeast α-agglutinin protein. The recombinant yeast strain, PHY, was constructed by successfully displaying phytase on the surface of cells, and enzyme activity reached 6.4 U/g wet biomass weight. Ethanol productions using various strains were compared, and the results demonstrated that the specific growth rate and average fermentation rate of the PHY strain were higher 20 and 18 %, respectively, compared to the control strain S. cerevisiae CICIMY0086, in a 5-L bioreactor process by simultaneous saccharification and fermentation. More importantly, the phytate phosphorus concentration decreased by 89.8 % and free phosphorus concentration increased by 142.9 % in dry vinasse compared to the control in a 5-L bioreactor. In summary, we constructed a recombinant S. cerevisiae strain displaying phytase on the cell surface, which could improve ethanol production performance and effectively reduce the discharge of phosphorus. The strain reported here represents a useful novel engineering platform for developing an environment-friendly system for bioethanol production from a corn substrate. PMID:26610799

  2. Strain-induced band-gap engineering of graphene monoxide and its effect on graphene

    Science.gov (United States)

    Pu, H. H.; Rhim, S. H.; Hirschmugl, C. J.; Gajdardziska-Josifovska, M.; Weinert, M.; Chen, J. H.

    2013-02-01

    Using first-principles calculations we demonstrate the feasibility of band-gap engineering in two-dimensional crystalline graphene monoxide (GMO), a recently reported graphene-based material with a 1:1 carbon/oxygen ratio. The band gap of GMO, which can be switched between direct and indirect, is tunable over a large range (0-1.35 eV) for accessible strains. Electron and hole transport occurs predominantly along the zigzag and armchair directions (armchair for both) when GMO is a direct- (indirect-) gap semiconductor. A band gap of ˜0.5 eV is also induced in graphene at the K' points for GMO/graphene hybrid systems.

  3. Band gap engineering in polymers through chemical doping and applied mechanical strain.

    Science.gov (United States)

    Lanzillo, Nicholas A; Breneman, Curt M

    2016-08-17

    We report simulations based on density functional theory and many-body perturbation theory exploring the band gaps of common crystalline polymers including polyethylene, polypropylene and polystyrene. Our reported band gaps of 8.6 eV for single-chain polyethylene and 9.1 eV for bulk crystalline polyethylene are in excellent agreement with experiment. The effects of chemical doping along the polymer backbone and side-groups are explored, and the use mechanical strain as a means to modify the band gaps of these polymers over a range of several eV while leaving the dielectric constant unchanged is discussed. This work highlights some of the opportunities available to engineer the electronic properties of polymers with wide-reaching implications for polymeric dielectric materials used for capacitive energy storage. PMID:27324304

  4. Strain-Engineered Low-Density InAs Bilayer Quantum Dots for Single Photon Emission

    Institute of Scientific and Technical Information of China (English)

    LI Zhan-Guo; LIU Guo-Jun; LI Lin; FENG Ming; LI Mei; LU Peng; ZOU Yong-Gang; LI Lian-He; GAO Xin

    2010-01-01

    @@ We investigate the growth of strain-engineered low-density InAs bilayer quantum dots(BQDs)on GaAs bymolecular beam epitaxy.Owing to increasing dot size and In composition of the upper QDs,low-density BQDs in a GaAs matrix with an emission wavelength up to 1.4 μm at room temperature are achieved.Such a wavelength is larger than that of conventional QDs in a GaAs matrix(generally of about 1.3 μm).The optical properties of the BQDs are sensitive to annealing temperature used after spacer layer growth.Significant decrease of integrated PL intensity is observed as the annealing temperature increases.At IO K,single photon emission from the BQDs with wavelength around 1.3μm is observed.

  5. Strain-Engineered Low-Density InAs Bilayer Quantum Dots for Single Photon Emission

    International Nuclear Information System (INIS)

    We investigate the growth of strain-engineered low-density InAs bilayer quantum dots (BQDs) on GaAs by molecular beam epitaxy. Owing to increasing dot size and In composition of the upper QDs, low-density BQDs in a GaAs matrix with an emission wavelength up to 1.4 μm at room temperature are achieved. Such a wavelength is larger than that of conventional QDs in a GaAs matrix (generally of about 1.3 μm). The optical properties of the BQDs are sensitive to annealing temperature used after spacer layer growth. Significant decrease of integrated PL intensity is observed as the annealing temperature increases. At 10K, single photon emission from the BQDs with wavelength around 1.3 μm is observed. (condensed matter: structure, mechanical and thermal properties)

  6. Band gap engineering in polymers through chemical doping and applied mechanical strain

    Science.gov (United States)

    Lanzillo, Nicholas A.; Breneman, Curt M.

    2016-08-01

    We report simulations based on density functional theory and many-body perturbation theory exploring the band gaps of common crystalline polymers including polyethylene, polypropylene and polystyrene. Our reported band gaps of 8.6 eV for single-chain polyethylene and 9.1 eV for bulk crystalline polyethylene are in excellent agreement with experiment. The effects of chemical doping along the polymer backbone and side-groups are explored, and the use mechanical strain as a means to modify the band gaps of these polymers over a range of several eV while leaving the dielectric constant unchanged is discussed. This work highlights some of the opportunities available to engineer the electronic properties of polymers with wide-reaching implications for polymeric dielectric materials used for capacitive energy storage.

  7. Hydrogen production and metabolic flux analysis of metabolically engineered Escherichia coli strains

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seohyoung; Seol, Eunhee; Park, Sunghoon [Department of Chemical and Biochemical Engineering, Pusan National University, Busan 609-735 (Korea); Oh, You-Kwan [Bioenergy Research Center, Korea Institute of Energy Research, Daejeon 305-543 (Korea); Wang, G.Y. [Department of Oceanography, University of Hawaii at Manoa Honolulu, HI 96822 (United States)

    2009-09-15

    Escherichia coli can produce H{sub 2} from glucose via formate hydrogen lyase (FHL). In order to improve the H{sub 2} production rate and yield, metabolically engineered E. coli strains, which included pathway alterations in their H{sub 2} production and central carbon metabolism, were developed and characterized by batch experiments and metabolic flux analysis. Deletion of hycA, a negative regulator for FHL, resulted in twofold increase of FHL activity. Deletion of two uptake hydrogenases (1 (hya) and hydrogenase 2 (hyb)) increased H{sub 2} production yield from 1.20 mol/mol glucose to 1.48 mol/mol glucose. Deletion of lactate dehydrogenase (ldhA) and fumarate reductase (frdAB) further improved the H{sub 2} yield; 1.80 mol/mol glucose under high H{sub 2} pressure or 2.11 mol/mol glucose under reduced H{sub 2} pressure. Several batch experiments at varying concentrations of glucose (2.5-10 g/L) and yeast extract (0.3 or 3.0 g/L) were conducted for the strain containing all these genetic alternations, and their carbon and energy balances were analyzed. The metabolic flux analysis revealed that deletion of ldhA and frdAB directed most of the carbons from glucose to the glycolytic pathway leading to H{sub 2} production by FHL, not to the pentose phosphate pathway. (author)

  8. Engineering control of bacterial cellulose production using a genetic toolkit and a new cellulose-producing strain

    OpenAIRE

    Florea, Michael; Hagemann, Henrik; Santosa, Gabriella; Abbott, James; Micklem, Chris N.; Spencer-Milnes, Xenia; de Arroyo Garcia, Laura; Paschou, Despoina; Lazenbatt, Christopher; Kong, Deze; Chughtai, Haroon; Jensen, Kirsten; Freemont, Paul S.; Kitney, Richard; Reeve, Benjamin

    2016-01-01

    Bacterial cellulose is a remarkable material that is malleable, biocompatible, and over 10-times stronger than plant-based cellulose. It is currently used to create materials for tissue engineering, medicine, defense, electronics, acoustics, and fabrics. We describe here a bacterial strain that is readily amenable to genetic engineering and produces high quantities of bacterial cellulose in low-cost media. To reprogram this organism for biotechnology applications, we created a set of genetic ...

  9. Characterization of global yeast quantitative proteome data generated from the wild-type and glucose repression Saccharomyces cerevisiae strains: The comparison of two quantitative methods

    DEFF Research Database (Denmark)

    Usaite, Renata; Wohlschlegel, James; Venable, John D.;

    2008-01-01

    The quantitative proteomic analysis of complex protein mixtures is emerging as a technically challenging but viable systems-level approach for studying cellular function. This study presents a large-scale comparative analysis of protein abundances from yeast protein lysates derived from both wild......-type yeast and yeast strains lacking key components of the Snf1 kinase complex. Four different strains were grown under well-controlled chemostat conditions. Multidimensional protein identification technology followed by quantitation using either spectral counting or stable isotope labeling approaches...... labeling strategy. The stable isotope labeling based quantitative approach was found to be highly reproducible among biological replicates when complex protein mixtures containing small expression changes were analyzed. Where poor correlation between stable isotope labeling and spectral counting was found...

  10. Comparison of SHF and SSF processes from steam-exploded wheat straw for ethanol production by xylose-fermenting and robust glucose-fermenting Saccharomyces cerevisiae strains

    DEFF Research Database (Denmark)

    Tomas Pejo, Elia; Oliva, Jose M.; Ballesteros, Mercedes;

    2008-01-01

    amounts of pentoses. Red Star is a robust hexose-fermenting strain used for industrial fuel ethanol fermentations and it was used for comparative purposes. The highest ethanol concentration, 23.7 g/L, was reached using the whole slurry (10%, w/v) and the recombinant strain (F12) in an SSF process......, it showed an ethanol yield on consumed sugars of 0.43 g/g and a volumetric ethanol productivity of 0.7 g/Lh for the first 3 h. Ethanol concentrations obtained in SSF processes were in all cases higher than those from SHF at the same conditions. Furthermore, using the whole slurry, final ethanol...... concentration was improved in all tests due to the increase of potential fermentable sugars in the fermentation broth. Inhibitory compounds present in the pretreated wheat straw caused a significantly negative effect on the fermentation rate. However, it was found that the inhibitors furfural and HMF were...

  11. 高产酿酒酵母SCY6生长与发酵条件的优化%Optimization of Growth and Fermentation Conditions for High Ethanol-Producing Saccharomyces cerevisiae Strain SCY6

    Institute of Scientific and Technical Information of China (English)

    顾华祥; 宋晨; 李迅

    2012-01-01

    采用高产酿酒酵母(Saccharomyces cerevisiae)SCY6发酵葡萄糖产乙醇,设计单因素试验考察该酵母菌株适宜的生长条件,采用正交试验优化酵母发酵产乙醇的条件.结果表明,该酵母菌株的最适生长温度和pH分别为28℃、5.0,培养基中葡萄糖质量分数为15%时其生长状态较好.正交试验结果表明,最适合该酿酒酵母发酵产乙醇的条件为玉米浆和(NH4)2SO4作为氮源,用量分别为20 g/L和2 g/L,接种量为4%,pH 5.0.在此条件下进行发酵,发酵液中乙醇体积分数可达7.77%,葡萄糖转化率达83.82%.%The high ethanol-producing Saccharomyces cerevisiae strain SCY6 was used to ferment glucose to ethanol. Single factor tests were conducted to optimize the cultivation conditions; while orthogonal design was adopted to optimize ethanol fermentation conditions. The results showed that the optimum temperature and pH for yeast growth was 28℃ and 5.0, respectively. The yeast grew well when mass ratio of glucose in YPD medium was 15%. The result of orthogonal test showed that the optimal ethanol fermentation conditions were, 2 g/L (NH4)2SO4 and 20g/L corn syrup as N source; inoculation dose, 4% volume fraction; and pH 5.0. The yield of ethanol reached 7.77%; and the conversion rate of glucose was 83.82% under these conditions.

  12. Industrial systems biology of Saccharomyces cerevisiae enables novel succinic acid cell factory.

    Directory of Open Access Journals (Sweden)

    José Manuel Otero

    Full Text Available Saccharomyces cerevisiae is the most well characterized eukaryote, the preferred microbial cell factory for the largest industrial biotechnology product (bioethanol, and a robust commerically compatible scaffold to be exploitted for diverse chemical production. Succinic acid is a highly sought after added-value chemical for which there is no native pre-disposition for production and accmulation in S. cerevisiae. The genome-scale metabolic network reconstruction of S. cerevisiae enabled in silico gene deletion predictions using an evolutionary programming method to couple biomass and succinate production. Glycine and serine, both essential amino acids required for biomass formation, are formed from both glycolytic and TCA cycle intermediates. Succinate formation results from the isocitrate lyase catalyzed conversion of isocitrate, and from the α-keto-glutarate dehydrogenase catalyzed conversion of α-keto-glutarate. Succinate is subsequently depleted by the succinate dehydrogenase complex. The metabolic engineering strategy identified included deletion of the primary succinate consuming reaction, Sdh3p, and interruption of glycolysis derived serine by deletion of 3-phosphoglycerate dehydrogenase, Ser3p/Ser33p. Pursuing these targets, a multi-gene deletion strain was constructed, and directed evolution with selection used to identify a succinate producing mutant. Physiological characterization coupled with integrated data analysis of transcriptome data in the metabolically engineered strain were used to identify 2(nd-round metabolic engineering targets. The resulting strain represents a 30-fold improvement in succinate titer, and a 43-fold improvement in succinate yield on biomass, with only a 2.8-fold decrease in the specific growth rate compared to the reference strain. Intuitive genetic targets for either over-expression or interruption of succinate producing or consuming pathways, respectively, do not lead to increased succinate. Rather, we

  13. Predictive Synthesis of Freeform Carbon Nanotube Microarchitectures by Strain-Engineered Chemical Vapor Deposition.

    Science.gov (United States)

    Park, Sei Jin; Zhao, Hangbo; Kim, Sanha; De Volder, Michael; John Hart, A

    2016-08-01

    High-throughput fabrication of microstructured surfaces with multi-directional, re-entrant, or otherwise curved features is becoming increasingly important for applications such as phase change heat transfer, adhesive gripping, and control of electromagnetic waves. Toward this goal, curved microstructures of aligned carbon nanotubes (CNTs) can be fabricated by engineered variation of the CNT growth rate within each microstructure, for example by patterning of the CNT growth catalyst partially upon a layer which retards the CNT growth rate. This study develops a finite-element simulation framework for predictive synthesis of complex CNT microarchitectures by this strain-engineered growth process. The simulation is informed by parametric measurements of the CNT growth kinetics, and the anisotropic mechanical properties of the CNTs, and predicts the shape of CNT microstructures with impressive fidelity. Moreover, the simulation calculates the internal stress distribution that results from extreme deformation of the CNT structures during growth, and shows that delamination of the interface between the differentially growing segments occurs at a critical shear stress. Guided by these insights, experiments are performed to study the time- and geometry-depended stress development, and it is demonstrated that corrugating the interface between the segments of each microstructure mitigates the interface failure. This study presents a methodology for 3D microstructure design based on "pixels" that prescribe directionality to the resulting microstructure, and show that this framework enables the predictive synthesis of more complex architectures including twisted and truss-like forms.

  14. Converting Carbon Dioxide to Butyrate with an Engineered Strain of Clostridium ljungdahlii

    Energy Technology Data Exchange (ETDEWEB)

    Ueki, T; Nevin, KP; Woodard, TL; Lovley, DR

    2014-08-26

    Microbial conversion of carbon dioxide to organic commodities via syngas metabolism or microbial electrosynthesis is an attractive option for production of renewable biocommodities. The recent development of an initial genetic toolbox for the acetogen Clostridium ljungdahlii has suggested that C. ljungdahlii may be an effective chassis for such conversions. This possibility was evaluated by engineering a strain to produce butyrate, a valuable commodity that is not a natural product of C. ljungdahlii metabolism. Heterologous genes required for butyrate production from acetyl-coenzyme A (CoA) were identified and introduced initially on plasmids and in subsequent strain designs integrated into the C. ljungdahlii chromosome. Iterative strain designs involved increasing translation of a key enzyme by modifying a ribosome binding site, inactivating the gene encoding the first step in the conversion of acetyl-CoA to acetate, disrupting the gene which encodes the primary bifunctional aldehyde/alcohol dehydrogenase for ethanol production, and interrupting the gene for a CoA transferase that potentially represented an alternative route for the production of acetate. These modifications yielded a strain in which ca. 50 or 70% of the carbon and electron flow was diverted to the production of butyrate with H-2 or CO as the electron donor, respectively. These results demonstrate the possibility of producing high-value commodities from carbon dioxide with C. ljungdahlii as the catalyst. IMPORTANCE The development of a microbial chassis for efficient conversion of carbon dioxide directly to desired organic products would greatly advance the environmentally sustainable production of biofuels and other commodities. Clostridium ljungdahlii is an effective catalyst for microbial electrosynthesis, a technology in which electricity generated with renewable technologies, such as solar or wind, powers the conversion of carbon dioxide and water to organic products. Other electron donors

  15. L-Histidine inhibits biofilm formation and FLO11- associated phenotypes in Saccharomyces cerevisiae flor yeasts

    OpenAIRE

    Bou Zeidan, Marc; Zara, Giacomo; Viti, Carlo; Decorosi, Francesca; Mannazzu, Ilaria Maria; Budroni, Marilena; Giovannetti, Luciana; Zara, Severino

    2014-01-01

    Flor yeasts of Saccharomyces cerevisiae have an innate diversity of FLO11 which codes for a highly hydrophobic and anionic cell-wall glycoprotein with a fundamental role in biofilm formation. In this study, 380 nitrogen compounds were administered to three S. cerevisiae flor strains handling FLO11 alleles with different expression levels. S. cerevisiae strain S288c was used as the reference strain as it cannot produce FLO11p. The flor strains generally metabolized amino acids and dipeptides a...

  16. TOTAL ANTIOXIDANT ACTIVITY OF YEAST SACCHAROMYCES CEREVISIAE

    Directory of Open Access Journals (Sweden)

    Blažena Lavová

    2013-02-01

    Full Text Available Antioxidants are health beneficial compounds that can protect cells and macromolecules (e.g. fats, lipids, proteins and DNA from the damage of reactive oxygen species (ROS. Sacchamomyces cerevisiae are know as organisms with very important antioxidative enzyme systems such as superoxide dismutase or catalase. The total antioxidant activity (mmol Trolox equivalent – TE.g-1 d.w. of Saccharomyces cerevisiae was measured by 2,2´-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid during the yeast cultivation. It was found that the total antioxidant activity was the highest (1.08 mmol TE.g-1 d.w. in the strain Kolín after 32 hours of cultivation and the lowest (0.26 mmol TE.g-1 d.w. in the strain Gyöng after 12 hours of cultivation.

  17. Construction and evaluation of an exopolysaccharide-producing engineered bacterial strain by protoplast fusion for microbial enhanced oil recovery.

    Science.gov (United States)

    Sun, Shanshan; Luo, Yijing; Cao, Siyuan; Li, Wenhong; Zhang, Zhongzhi; Jiang, Lingxi; Dong, Hanping; Yu, Li; Wu, Wei-Min

    2013-09-01

    Enterobacter cloacae strain JD, which produces water-insoluble biopolymers at optimal temperature of 30°C, and a thermophilic Geobacillus strain were used to construct an engineered strain for exopolysaccharide production at high temperatures by protoplast fusion. The obtained fusant strain ZR3 produced exopolysaccharides at up to 45°C with optimal growth temperature at 35°C. The fusant produced exopolysaccharides of approximately 7.5 g/L or more at pH between 7.0 and 9.0. The feasibility of the enhancement of crude oil recovery with the fusant was tested in a sand-packed column at 40°C. The results demonstrated that bioaugmentation of the fusant was promising approach for MEOR. Mass growth of the fusant was confirmed in fermentor tests. PMID:23856587

  18. Isolation of the catalase T structural gene of Saccharomyces cerevisiae by functional complementation.

    OpenAIRE

    Spevak, W; Fessl, F; Rytka, J; Traczyk, A; Skoneczny, M; Ruis, H

    1983-01-01

    The catalase T structural gene of Saccharomyces cerevisiae was cloned by functional complementation of a mutation causing specific lack of the enzyme (cttl). Catalase T-deficient mutants were obtained by UV mutagenesis of an S. cerevisiae strain bearing the cas1 mutation, which causes insensitivity of catalase T to glucose repression. Since the second catalase protein of S. cerevisiae, catalase A, is completely repressed on 10% glucose, catalase T-deficient mutant colonies could be detected u...

  19. Surface display of malolactic enzyme from Oenococcus oeni on Saccharomyces cerevisiae.

    Science.gov (United States)

    Zhang, Xiuyan; Hou, Xiaoyan; Liang, Fang; Chen, Fusheng; Wang, Xiaohong

    2013-04-01

    In order to display malolactic enzyme (MLE) on the cell surface of Saccharomyces cerevisiae, a yeast cell surface display plasmid pADH1-AGG was constructed by fusing the α-factor signal encoding sequence (267 bp) and the C-terminal half of α-agglutinin encoding sequence (1,645 bp) into the plasmid pADH1. The pADH1-AGG could successfully express and anchor the enhanced green fluorescent protein (EGFP) onto the yeast cell surface when the EGFP was used to verify its function. Then the pADH1-MLE was constructed by inserting the MLE encoding sequence (1,600 bp) into the pADH1-AGG and introduced into S. cerevisiae cells. The positive strain carrying pADH1-MLE was confirmed by use of the 6× His monoclonal antibody and fluorescein isothiocyanate-conjugated goat anti-mouse IgG. All results indicated that the MLE was displayed successfully on the cell surface of positive transformant. The MLE activity of genetically engineered yeast strain could turn 21.11 % L-malate into lactic acid after 12 h reaction with L-malate. The constructed yeast strain might be used to conduct malolactic fermentation (MLF) in wine to solve the important issues of sluggish MLF, microbial spoilage, and adverse metabolic substances produced by the lactic acid bacteria. PMID:23446978

  20. Phosphate transport and sensing in Saccharomyces cerevisiae.

    OpenAIRE

    Wykoff, D D; O'Shea, E K

    2001-01-01

    Cellular metabolism depends on the appropriate concentration of intracellular inorganic phosphate; however, little is known about how phosphate concentrations are sensed. The similarity of Pho84p, a high-affinity phosphate transporter in Saccharomyces cerevisiae, to the glucose sensors Snf3p and Rgt2p has led to the hypothesis that Pho84p is an inorganic phosphate sensor. Furthermore, pho84Delta strains have defects in phosphate signaling; they constitutively express PHO5, a phosphate starvat...

  1. Phenotypical signs and chemical composition of Saccharomyces cerevisiae – mannoprotein producers

    Directory of Open Access Journals (Sweden)

    Agafia USATII

    2012-11-01

    Full Text Available Phenotypical signs and chemical composition of Saccharomyces cerevisiae CNMN-Y-18 and Saccharomyces cerevisiae CNMN-Y-19 yeast strains are described in this article. The presence of protein complexes with high content of irreplaceable amino acids and antioxidant enzymes, as well as polysaccharides with predominance of mannoproteins allow to recommend these yeast strains for the utilization in biotechnology. Results are of interest for the standard description of yeast strains offered as object for industrial appointment.

  2. Selection of indigenous Saccharomyces cerevisiae strains in Tianjin and their oenological characterization of low-alcohol white wine%本土酿酒酵母的筛选及其低醇葡萄酒特性研究

    Institute of Scientific and Technical Information of China (English)

    崔艳; 吕文; 王伟; 蒋珍珍; 刘金福

    2011-01-01

    以天津宝坻产区的三种葡萄为原料,分别从自然发酵的葡萄汁中筛选出340株酵母菌,经生理生化,产酸、酯、尿酶、H2S,发酵能力测定及26SrRNA测序,确定4株为酿酒酵母,用于贵人香低醇白葡萄酒的酿造。以商用酵母为对照,定量分析了不同酵母所酿酒中的香气成分、氨基甲酸乙酯含量,并进行了理化指标和感官测定,发现酵母C508和G611酿造的低醇酒具有更独特的香气特点,氨基甲酸乙酯的含量较低,微生物稳定性较高,更适合低醇酒的酿造。%In order to identify the Saccharomyces spp.associated with spontaneous fermentation of three different grape varieties(Italian Riesling,Muscat and Cabernet Sauvignon grapes)from Tianjin Baodi wine region and to evaluate the micro-fermentation performance of low-alcohol white wine.The indigeous yeast flora isolated during fermentation was studied and analyzed.Firstly,yeasts were identified to genus level by growth on WL nutrient agar and the tests of assimilation carbon and nitrogen source and so on.Later,formation of amyloid,acids,esters,H2S and urease and fermentation power were studied.Three hundred and forty strains were isolated,four of which were identified as Saccharomyces cerevisiae by PCR of D1/D2 regions of the 26S rRNA gene and tested as starters in low-alcohol white wine fermentations for their satisfactory oenological properties.The quality of the produced wines was evaluated after determination of their physical-chemical parameters,volatile compounds and ethyl carbamate produced in wine fermentation.The results showed the potential of employing indigenous yeast strains for the production low-alcohol white wine with improved stability,a richer aromatic bouquet,less ethyl carbamate concentration.

  3. Band gap tuning of epitaxial SrTiO{sub 3-δ}/Si(001) thin films through strain engineering

    Energy Technology Data Exchange (ETDEWEB)

    Cottier, Ryan J.; Steinle, Nathan A.; Currie, Daniel A.; Theodoropoulou, Nikoleta, E-mail: ntheo@txstate.edu [Physics Department, Texas State University, San Marcos, Texas 78666 (United States)

    2015-11-30

    We investigate the effect of strain and oxygen vacancies (V{sub O}) on the crystal and optical properties of oxygen deficient, ultra-thin (4–30 nm) films of SrTiO{sub 3-δ} (STO) grown heteroepitaxially on p-Si(001) substrates by molecular beam epitaxy. We demonstrate that STO band gap tuning can be achieved through strain engineering and show that the energy shift of the direct energy gap transition of SrTiO{sub 3-δ}/Si films has a quantifiable dimensional and doping dependence that correlates well with the changes in crystal structure.

  4. Functional co-operation between the nuclei of Saccharomyces cerevisiae and mitochondria from other yeast species

    DEFF Research Database (Denmark)

    Spirek, M.; Horvath, A.; Piskur, Jure;

    2000-01-01

    We elaborated a simple method that allows the transfer of mitochondria from collection yeasts to Saccharomyces cerevisiae. Protoplasts prepared from different yeasts were fused to the protoplasts of the ade2-1, ura3-52, kar1-1, rho (0) strain of S. cerevisiae and were selected for respiring cybrids...

  5. Multiple gene mediated aldehyde reduction is a mechanism of in situ detoxification of furfural and 5-hydroxymethylfurfural by Saccharomyces cerevisiae

    Science.gov (United States)

    Furfural and HMF (5-hydroxymethylfurfural) are representative inhibitors to ethanologenic yeast generated from biomass pretreatment using dilute acid hydrolysis. Few yeast strains tolerant to inhibitors are available. We have developed tolerant strains of Saccharomyces cerevisiae with enhanced bio...

  6. Adaption of Saccharomyces cerevisiae expressing a heterologous protein

    DEFF Research Database (Denmark)

    Krogh, Astrid Mørkeberg; Beck, Vibe; Højlund Christensen, Lars;

    2008-01-01

    Production of the heterologous protein, bovine aprotinin, in Saccharomyces cerevisiae was shown to affect the metabolism of the host cell to various extent depending on the strain genotype. Strains with different genotypes, industrial and laboroatory, respectively, were investigated. The maximal ...... result of the adaptation. Determination of the level of mRNA encoding aprotinin and the plasmid copy number pointed to different mechanisms responsible for the decline in aprotinin yield in the different strains. (C) 2008 Elsevier B.V. All rights reserved....

  7. Advances in metabolic pathway and strain engineering paving the way for sustainable production of chemical building blocks

    DEFF Research Database (Denmark)

    Chen, Yun; Nielsen, Jens

    2013-01-01

    Bio-based production of chemical building blocks from renewable resources is an attractive alternative to petroleum-based platform chemicals. Metabolic pathway and strain engineering is the key element in constructing robust microbial chemical factories within the constraints of cost effective pr...... developments contribute to the development of novel cell factories for the production of the building block chemicals: adipic acid, succinic acid and 3-hydroxypropionic acid....

  8. Engineering Cofactor Preference of Ketone Reducing Biocatalysts: A Mutagenesis Study on a γ-Diketone Reductase from the Yeast Saccharomyces cerevisiae Serving as an Example

    Directory of Open Access Journals (Sweden)

    Michael Katzberg

    2010-04-01

    Full Text Available The synthesis of pharmaceuticals and catalysts more and more relies on enantiopure chiral building blocks. These can be produced in an environmentally benign and efficient way via bioreduction of prochiral ketones catalyzed by dehydrogenases. A productive source of these biocatalysts is the yeast Saccharomyces cerevisiae, whose genome also encodes a reductase catalyzing the sequential reduction of the γ-diketone 2,5-hexanedione furnishing the diol (2S,5S-hexanediol and the γ-hydroxyketone (5S-hydroxy-2-hexanone in high enantio- as well as diastereoselectivity (ee and de >99.5%. This enzyme prefers NADPH as the hydrogen donating cofactor. As NADH is more stable and cheaper than NADPH it would be more effective if NADH could be used in cell-free bioreduction systems. To achieve this, the cofactor binding site of the dehydrogenase was altered by site-directed mutagenesis. The results show that the rational approach based on a homology model of the enzyme allowed us to generate a mutant enzyme having a relaxed cofactor preference and thus is able to use both NADPH and NADH. Results obtained from other mutants are discussed and point towards the limits of rationally designed mutants.

  9. Expression of native and mutant extracellular lipases fromYarrowia lipolytica in Saccharomyces cerevisiae

    OpenAIRE

    Darvishi, Farshad

    2012-01-01

    Summary Saccharomyces cerevisiae cannot produce extracellular lipase and utilize low‐cost lipid substrates. This study aimed to express extracellular lipase from Yarrowia lipolytica in S. cerevisiae, construct recombinant oily substrate consumer strains, and compare the roles of native and mutant Y. lipolytica extracellular lipases in S. cerevisiae. The LIP2 gene of Y. lipolytica DSM3286 and its mutant Y. lipolytica U6 were isolated and cloned by expression vector in S. cerevisiae. New recomb...

  10. Strain properties analysis and wireless collection system of PVDF for structural local health monitoring of civil engineering structures

    Science.gov (United States)

    Yu, Yan; Wang, Yang; Dong, Weijie; Jin, Yajing; Ou, Jinping

    2009-07-01

    For large civil engineering structures and base establishments, for example, bridges, super-high buildings, long-span space structures, offshore platforms and pipe systems of water & gas supply, their lives are up to a few decades or centuries. Damaged by environmental loads, fatigue effects, corrosion effects and material aging, these structures experience inevitably such side effects as damage accumulation, resistance reduction and even accidents. The traditional civil structure is a kind of passive one, whose performance and status are unpredictable to a great extent, but the informatics' introduction breaks a new path to obtain the status of the structure, thus it is an important research direction to evaluate and improve reliability of civil structures by the use of monitoring and health diagnosis technique, and this also assures the security of service for civil engineering structures. Smart material structure, originated from the aerospace sector, has been a research hotspot in civil engineering, medicine, shipping, and so on. For structural health monitoring of civil engineering, the research about high-performance sensing unit of smart material structure is very important, and this will possibly push further the development and application of monitoring and health diagnosis techniques. At present, piezoelectric materials are one of the most widely used sensing materials among the research of smart material structures. As one of the piezoelectric materials, PVDF(Polyvinylidene Fluoride)film is widely considered for the advantages of low cost, good mechanical ability, high sensibility, the ability of being easily placed and resistance of corrosion. However, only a few studies exit about building a mature monitoring system using PVDF. In this paper, for the sake of using PVDF for sensing unit for structural local monitoring of civil engineering, the strain sensing properties of PVDF are studied in detail. Firstly, the operating mechanism of PVDF is analyzed

  11. Metabolic engineering of microbial competitive advantage for industrial fermentation processes.

    Science.gov (United States)

    Shaw, A Joe; Lam, Felix H; Hamilton, Maureen; Consiglio, Andrew; MacEwen, Kyle; Brevnova, Elena E; Greenhagen, Emily; LaTouf, W Greg; South, Colin R; van Dijken, Hans; Stephanopoulos, Gregory

    2016-08-01

    Microbial contamination is an obstacle to widespread production of advanced biofuels and chemicals. Current practices such as process sterilization or antibiotic dosage carry excess costs or encourage the development of antibiotic resistance. We engineered Escherichia coli to assimilate melamine, a xenobiotic compound containing nitrogen. After adaptive laboratory evolution to improve pathway efficiency, the engineered strain rapidly outcompeted a control strain when melamine was supplied as the nitrogen source. We additionally engineered the yeasts Saccharomyces cerevisiae and Yarrowia lipolytica to assimilate nitrogen from cyanamide and phosphorus from potassium phosphite, and they outcompeted contaminating strains in several low-cost feedstocks. Supplying essential growth nutrients through xenobiotic or ecologically rare chemicals provides microbial competitive advantage with minimal external risks, given that engineered biocatalysts only have improved fitness within the customized fermentation environment.

  12. Metabolic engineering of microbial competitive advantage for industrial fermentation processes.

    Science.gov (United States)

    Shaw, A Joe; Lam, Felix H; Hamilton, Maureen; Consiglio, Andrew; MacEwen, Kyle; Brevnova, Elena E; Greenhagen, Emily; LaTouf, W Greg; South, Colin R; van Dijken, Hans; Stephanopoulos, Gregory

    2016-08-01

    Microbial contamination is an obstacle to widespread production of advanced biofuels and chemicals. Current practices such as process sterilization or antibiotic dosage carry excess costs or encourage the development of antibiotic resistance. We engineered Escherichia coli to assimilate melamine, a xenobiotic compound containing nitrogen. After adaptive laboratory evolution to improve pathway efficiency, the engineered strain rapidly outcompeted a control strain when melamine was supplied as the nitrogen source. We additionally engineered the yeasts Saccharomyces cerevisiae and Yarrowia lipolytica to assimilate nitrogen from cyanamide and phosphorus from potassium phosphite, and they outcompeted contaminating strains in several low-cost feedstocks. Supplying essential growth nutrients through xenobiotic or ecologically rare chemicals provides microbial competitive advantage with minimal external risks, given that engineered biocatalysts only have improved fitness within the customized fermentation environment. PMID:27493184

  13. Genetic engineering of baker's and wine yeasts using formaldehyde hyperresistance-mediating plasmids

    Directory of Open Access Journals (Sweden)

    M. Schmidt

    1997-12-01

    Full Text Available Yeast multi-copy vectors carrying the formaldehyde-resistance marker gene SFA have proved to be a valuable tool for research on industrially used strains of Saccharomyces cerevisiae. The genetics of these strains is often poorly understood, and for various reasons it is not possible to simply subject these strains to protocols of genetic engineering that have been established for laboratory strains of S. cerevisiae. We tested our vectors and protocols using 10 randomly picked baker's and wine yeasts all of which could be transformed by a simple protocol with vectors conferring hyperresistance to formaldehyde. The application of formaldehyde as a selecting agent also offers the advantage of its biodegradation to CO2 during fermentation, i.e., the selecting agent will be consumed and therefore its removal during down-stream processing is not necessary. Thus, this vector provides an expression system which is simple to apply and inexpensive to use

  14. Construction of engineering Trichoderma strains and their characteristics against tomato gray mold

    Institute of Scientific and Technical Information of China (English)

    LIU Xian; ZHUANG Jing-hua; GAO Zeng-gui; YANG Chang-cheng; CHEN Jie

    2004-01-01

    @@ The transformed Trichoderma strains Ttrm31, Ttrm34 and Ttrm55 were obtained from Trichoderma wild strain T21 mutated by REMI technique for more effective biocontrol of tomato gray mold (Botrytis cinerea) with Trichoderma agent. Those transformants appeared much better in biocontrol activity in vitro or in vivo against tomato gray mold were better than that of wild strain T21. The main results were as follow:

  15. Saccharomyces cerevisiae metabolism in ecological context

    Science.gov (United States)

    Jouhten, Paula; Ponomarova, Olga; Gonzalez, Ramon; Patil, Kiran R.

    2016-01-01

    The architecture and regulation of Saccharomyces cerevisiae metabolic network are among the best studied owing to its widespread use in both basic research and industry. Yet, several recent studies have revealed notable limitations in explaining genotype–metabolic phenotype relations in this yeast, especially when concerning multiple genetic/environmental perturbations. Apparently unexpected genotype–phenotype relations may originate in the evolutionarily shaped cellular operating principles being hidden in common laboratory conditions. Predecessors of laboratory S. cerevisiae strains, the wild and the domesticated yeasts, have been evolutionarily shaped by highly variable environments, very distinct from laboratory conditions, and most interestingly by social life within microbial communities. Here we present a brief review of the genotypic and phenotypic peculiarities of S. cerevisiae in the context of its social lifestyle beyond laboratory environments. Accounting for this ecological context and the origin of the laboratory strains in experimental design and data analysis would be essential in improving the understanding of genotype–environment–phenotype relationships. PMID:27634775

  16. Roles of human sulfotransferases in genotoxicity of carcinogens using genetically engineered umu test strains.

    Science.gov (United States)

    Oda, Yoshimitsu; Zhang, Yu; Buchinger, Sebastian; Reifferscheid, Georg; Yang, Min

    2012-03-01

    Human sulfotransferase (SULT) 1A1, 1A2, and 1A3 cDNA genes were subcloned separately into the pTrc99A(KM) vector. The generated plasmids were introduced into the Salmonella typhimurium O-acetyltransferase-deficient strain NM6000 (TA1538/1,8-DNP/pSK1002), resulting in the new strains NM7001, NM7002, and NM7003. We compared the sensitivities of these three strains with the parental strain NM7000 against 51 chemicals including aromatic amines, nitroarenes, alkenylbenzenes, estrogens-like chemicals, and other compounds with and without S9 mix by making use of the umu test system that is based on the bacterial SOS induction. 2-Amino-6-methyl-dipyrido[1,2-α:3',2'-d]imidazole, 3-methoxy-4-aminoazobenzene, 3-nitrobenzanthrone, 5-nitroacenaphthene, and 3,9-dinitrofluoranthene caused high genotoxicity in the NM7001 strain. The genotoxic effects of 2-aminofluorene, 2-acetylaminofluorene, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, 2-nitrofluorene, 1-nitropyrene, and 2-nitropropane were stronger in the NM7002 strain compared with the NM7001 and NM7003 strains. Among the tested benzylic and allylic compounds, 1-hydroxymethylpyrene was detected in the NM7001 strain with the highest sensitivity. Estragole and 1'-hydroxysafrole exhibited strong genotoxicity in the NM7003 strain. The estrogen-like chemicals such as bisphenol A, genistein, p,n-nonylphenol, and 4-hydroxytamoxifen were not detected as genotoxins in any strain used. Collectively, the present results suggest that the generated test strains are valuable tools in order to elucidate the role of SULT enzymes in the bioactivation of chemicals to environmental carcinogens. PMID:22072630

  17. High-level production of animal-free recombinant transferrin from saccharomyces cerevisiae

    Directory of Open Access Journals (Sweden)

    Goldenberg Hans

    2010-11-01

    Full Text Available Abstract Background Animal-free recombinant proteins provide a safe and effective alternative to tissue or serum-derived products for both therapeutic and biomanufacturing applications. While recombinant insulin and albumin already exist to replace their human counterparts in cell culture media, until recently there has been no equivalent for serum transferrin. Results The first microbial system for the high-level secretion of a recombinant transferrin (rTf has been developed from Saccharomyces cerevisiae strains originally engineered for the commercial production of recombinant human albumin (Novozymes' Recombumin® USP-NF and albumin fusion proteins (Novozymes' albufuse®. A full-length non-N-linked glycosylated rTf was secreted at levels around ten-fold higher than from commonly used laboratory strains. Modification of the yeast 2 μm-based expression vector to allow overexpression of the ER chaperone, protein disulphide isomerase, further increased the secretion of rTf approximately twelve-fold in high cell density fermentation. The rTf produced was functionally equivalent to plasma-derived transferrin. Conclusions A Saccharomyces cerevisiae expression system has enabled the cGMP manufacture of an animal-free rTf for industrial cell culture application without the risk of prion and viral contamination, and provides a high-quality platform for the development of transferrin-based therapeutics.

  18. Co-fermentation of cellulose/xylan using engineered industrial yeast strain OC-2 displaying both β-glucosidase and β-xylosidase.

    Science.gov (United States)

    Saitoh, Satoshi; Tanaka, Tsutomu; Kondo, Akihiko

    2011-09-01

    We constructed a recombinant industrial Saccharomyces cerevisiae yeast strain OC2-AXYL2-ABGL2-Xyl2 by inserting two copies of the β-glucosidase (BGL) and β-xylosidase (XYL) genes, and a gene cassette for xylose assimilation in the genome of yeast strain OC-2HUT. Both BGL and XYL were expressed on the yeast cell surface with high enzyme activities. Using OC2-AXYL2-ABGL2-Xyl2, we performed ethanol fermentation from a mixture of powdered cellulose (KC-flock) and Birchwood xylan, with the additional supplementation of a 30-g/l Trichoderma reesei cellulase complex mixture. The ethanol yield (gram per gram of added cellulases) of the strain OC2-AXYL2-ABGL2-Xyl2 increased approximately 2.5-fold compared to that of strain OC2-Xyl2, which lacked β-glucosidase and β-xylosidase activities. Notably, the concentration of additional T. reesei cellulase was reduced from 30 to 24 g/l without affecting ethanol production. The BGL- and XYL-displaying industrial yeast of the strain OC2-AXYL2-ABGL2-Xyl2 represents a promising yeast for reducing cellulase consumption of ethanol fermentation from lignocellulosic biomass by compensating for the inherent weak BGL and XYL activities of T. reesei cellulase complexes. PMID:21643701

  19. Flux Balance Analysis Inspired Bioprocess Upgrading for Lycopene Production by a Metabolically Engineered Strain of Yarrowia lipolytica

    Directory of Open Access Journals (Sweden)

    Komi Nambou

    2015-12-01

    Full Text Available Genome-scale metabolic models embody a significant advantage of systems biology since their applications as metabolic flux simulation models enable predictions for the production of industrially-interesting metabolites. The biotechnological production of lycopene from Yarrowia lipolytica is an emerging scope that has not been fully scrutinized, especially for what concerns cultivation conditions of newly generated engineered strains. In this study, by combining flux balance analysis (FBA and Plackett-Burman design, we screened chemicals for lycopene production from a metabolically engineered strain of Y. lipolytica. Lycopene concentrations of 126 and 242 mg/L were achieved correspondingly from the FBA-independent and the FBA-assisted designed media in fed-batch cultivation mode. Transcriptional studies revealed upregulations of heterologous genes in media designed according to FBA, thus implying the efficiency of model predictions. Our study will potentially support upgraded lycopene and other terpenoids production from existing or prospect bioengineered strains of Y. lipolytica and/or closely related yeast species.

  20. Involvement of heme biosynthesis in control of sterol uptake by Saccharomyces cerevisiae.

    OpenAIRE

    Lewis, T A; Taylor, F R; Parks, L W

    1985-01-01

    Wild-type Saccharomyces cerevisiae do not accumulate exogenous sterols under aerobic conditions, and a mutant allele conferring sterol auxotrophy (erg7) could be isolated only in strains with a heme deficiency. delta-Aminolevulinic acid (ALA) fed to a hem1 (ALA synthetase-) erg7 (2,3-oxidosqualene cyclase-) sterol-auxotrophic strain of S. cerevisiae inhibited sterol uptake, and growth was negatively affected when intracellular sterol was depleted. The inhibition of sterol uptake (and growth o...

  1. Ferromagnetic (Ga,Mn)As layers and nanostructures: control of magnetic anisotropy by strain engineering

    Energy Technology Data Exchange (ETDEWEB)

    Wenisch, Jan

    2008-07-01

    This work studies the fundamental connection between lattice strain and magnetic anisotropy in the ferromagnetic semiconductor (Ga,Mn)As. The first chapters provide a general introduction into the material system and a detailed description of the growth process by molecular beam epitaxy. A finite element simulation formalism is developed to model the strain distribution in (Ga,Mn)As nanostructures is introduced and its predictions verified by high-resolution X-ray diffraction methods. The influence of lattice strain on the magnetic anisotropy is explained by an magnetostatic model. A possible device application is described in the closing chapter. (orig.)

  2. [Construction of the flavinogenic yeast Candida famata strains with high riboflavin kinase activity using gene engineering].

    Science.gov (United States)

    Ishchuk, O P; Iatsyshyn, V Iu; Dmytruk, K V; Voronovs'kyĭ, A Ia; Fedorovych, D V; Sybirnyĭ, A A

    2006-01-01

    The recombinant strains of the flavinogenic yeast Candida famata, which contain the DNA fragment consisting of the FMN1 gene (encoding the riboflavin kinase, enzyme that converts riboflavin to flavinmononucleotide) driven by the strong promoters (the regulated RIB1 or constitutive TEF1 promoter) were isolated. Riboflavin kinase activity in the isolated transformants was tested. The 6-8-fold increase of the riboflavin kinase activity was shown in the recombinant strains containing the integrated Debaryomyces hansenii FMN1 gene under the strong constitutive TEF1 promoter. The recombinant strains can be used for the following construction of flavinmononucleotide overproducers. PMID:17290783

  3. Dynamic control of gene expression in Saccharomyces cerevisiae engineered for the production of plant sesquitepene α-santalene in a fed-batch mode

    DEFF Research Database (Denmark)

    Scalcinati, Gionata; Knuf, Christoph; Partow, Siavash;

    2012-01-01

    -santalene, the precursor of a commercially interesting compound, was constructed through a rationally designed metabolic engineering approach. Optimal sesquiterpene production was obtained by modulating the expression of one of the key metabolic steps of the mevalonate (MVA) pathway, squalene synthase (Erg9). To couple...

  4. Nano-scale strain engineering of graphene and graphene-based devices

    OpenAIRE

    Yeh, N. -C.; Hsu, C.-C.; Teague, M. L.; Wang, J.-Q.; Boyd, D A; Chen, C.-C.

    2015-01-01

    Structural distortions in nano-materials can induce dramatic changes in their electronic properties. This situation is well manifested in graphene, a two-dimensional honeycomb structure of carbon atoms with only one atomic layer thickness. In particular, strained graphene can result in both charging effects and pseudo-magnetic fields, so that controlled strain on a perfect graphene lattice can be tailored to yield desirable electronic properties. Here we describe the theoretical foundation fo...

  5. Genetically Engineered Immunomodulatory Streptococcus thermophilus Strains Producing Antioxidant Enzymes Exhibit Enhanced Anti-Inflammatory Activities

    OpenAIRE

    del Carmen, Silvina; de Moreno de LeBlanc, Alejandra; Martin, Rebeca; Chain, Florian; Langella, Philippe; Bermúdez-Humarán, Luis G; LeBlanc, Jean Guy

    2014-01-01

    The aims of this study were to develop strains of lactic acid bacteria (LAB) having both immunomodulatory and antioxidant properties and to evaluate their anti-inflammatory effects both in vitro, in different cellular models, and in vivo, in a mouse model of colitis. Different Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus strains were cocultured with primary cultures of mononuclear cells. Analysis of the pro- and anti-inflammatory cytokines secreted by these cells...

  6. Carrier Mobility Enhancement of Tensile Strained Si and SiGe Nanowires via Surface Defect Engineering.

    Science.gov (United States)

    Ma, J W; Lee, W J; Bae, J M; Jeong, K S; Oh, S H; Kim, J H; Kim, S-H; Seo, J-H; Ahn, J-P; Kim, H; Cho, M-H

    2015-11-11

    Changes in the carrier mobility of tensile strained Si and SiGe nanowires (NWs) were examined using an electrical push-to-pull device (E-PTP, Hysitron). The changes were found to be closely related to the chemical structure at the surface, likely defect states. As tensile strain is increased, the resistivity of SiGe NWs deceases in a linear manner. However, the corresponding values for Si NWs increased with increasing tensile strain, which is closely related to broken bonds induced by defects at the NW surface. Broken bonds at the surface, which communicate with the defect state of Si are critically altered when Ge is incorporated in Si NW. In addition, the number of defects could be significantly decreased in Si NWs by incorporating a surface passivated Al2O3 layer, which removes broken bonds, resulting in a proportional decrease in the resistivity of Si NWs with increasing strain. Moreover, the presence of a passivation layer dramatically increases the extent of fracture strain in NWs, and a significant enhancement in mobility of about 2.6 times was observed for a tensile strain of 5.7%.

  7. Strain-engineering the anisotropic electrical conductance in ReS2 monolayer

    Science.gov (United States)

    Yu, Sheng; Zhu, Hao; Eshun, Kwesi; Shi, Chen; Zeng, Min; Li, Qiliang

    2016-05-01

    Rhenium disulfide (ReS2) is a semiconducting layered transition metal dichalcogenide that exhibits a stable distorted 1 T (Re in octahedral coordination) phase. The reduced symmetry in ReS2 leads to in-plane anisotropy in various material properties. In this work, we performed a comprehensive first-principle computational study of strain effect on the anisotropic mechanical and electronic properties of ReS2 monolayers. We found that the anisotropic ratio in electron mobility along two principle axes is 2.36 while the ratio in hole mobility reaches 7.76. The study of strain applied along different directions shows that the elastic modulus is largest for out-of-plane direction, and the strain along a-direction induces indirect bandgap while strain along b- or c-direction does not. In addition, the carrier mobility can be significantly improved by the c-direction tensile strain. This study indicates that the ReS2 monolayer has promising applications in nanoscale strain sensor and conductance-switch FETs.

  8. Isolation of peroxisome-deficient mutants of Saccharomyces cerevisiae

    NARCIS (Netherlands)

    Erdmann, Ralf; Veenhuis, Marten; Mertens, Daphne; Kunau, Wolf-H.

    1989-01-01

    Two mutants of Saccharomyces cerevisiae affected in peroxisomal assembly (pas mutants) have been isolated and characterized. Each strain contains a single mutation that results in (i) the inability to grow on oleic acid, (ii) accumulation of peroxisomal matrix enzymes in the cytosol, and (iii) absen

  9. Increasing anaerobic acetate consumption and ethanol yields in Saccharomyces cerevisiae with NADPH-specific alcohol dehydrogenase.

    Science.gov (United States)

    Henningsen, Brooks M; Hon, Shuen; Covalla, Sean F; Sonu, Carolina; Argyros, D Aaron; Barrett, Trisha F; Wiswall, Erin; Froehlich, Allan C; Zelle, Rintze M

    2015-12-01

    Saccharomyces cerevisiae has recently been engineered to use acetate, a primary inhibitor in lignocellulosic hydrolysates, as a cosubstrate during anaerobic ethanolic fermentation. However, the original metabolic pathway devised to convert acetate to ethanol uses NADH-specific acetylating acetaldehyde dehydrogenase and alcohol dehydrogenase and quickly becomes constrained by limited NADH availability, even when glycerol formation is abolished. We present alcohol dehydrogenase as a novel target for anaerobic redox engineering of S. cerevisiae. Introduction of an NADPH-specific alcohol dehydrogenase (NADPH-ADH) not only reduces the NADH demand of the acetate-to-ethanol pathway but also allows the cell to effectively exchange NADPH for NADH during sugar fermentation. Unlike NADH, NADPH can be freely generated under anoxic conditions, via the oxidative pentose phosphate pathway. We show that an industrial bioethanol strain engineered with the original pathway (expressing acetylating acetaldehyde dehydrogenase from Bifidobacterium adolescentis and with deletions of glycerol-3-phosphate dehydrogenase genes GPD1 and GPD2) consumed 1.9 g liter(-1) acetate during fermentation of 114 g liter(-1) glucose. Combined with a decrease in glycerol production from 4.0 to 0.1 g liter(-1), this increased the ethanol yield by 4% over that for the wild type. We provide evidence that acetate consumption in this strain is indeed limited by NADH availability. By introducing an NADPH-ADH from Entamoeba histolytica and with overexpression of ACS2 and ZWF1, we increased acetate consumption to 5.3 g liter(-1) and raised the ethanol yield to 7% above the wild-type level.

  10. Deletion of the Saccharomyces cerevisiae ARO8 gene, encoding an aromatic amino acid transaminase, enhances phenylethanol production from glucose.

    Science.gov (United States)

    Romagnoli, Gabriele; Knijnenburg, Theo A; Liti, Gianni; Louis, Edward J; Pronk, Jack T; Daran, Jean-Marc

    2015-01-01

    Phenylethanol has a characteristic rose-like aroma that makes it a popular ingredient in foods, beverages and cosmetics. Microbial production of phenylethanol currently relies on whole-cell bioconversion of phenylalanine with yeasts that harbour an Ehrlich pathway for phenylalanine catabolism. Complete biosynthesis of phenylethanol from a cheap carbon source, such as glucose, provides an economically attractive alternative for phenylalanine bioconversion. In this study, synthetic genetic array (SGA) screening was applied to identify genes involved in regulation of phenylethanol synthesis in Saccharomyces cerevisiae. The screen focused on transcriptional regulation of ARO10, which encodes the major decarboxylase involved in conversion of phenylpyruvate to phenylethanol. A deletion in ARO8, which encodes an aromatic amino acid transaminase, was found to underlie the transcriptional upregulation of ARO10 during growth, with ammonium sulphate as the sole nitrogen source. Physiological characterization revealed that the aro8Δ mutation led to substantial changes in the absolute and relative intracellular concentrations of amino acids. Moreover, deletion of ARO8 led to de novo production of phenylethanol during growth on a glucose synthetic medium with ammonium as the sole nitrogen source. The aro8Δ mutation also stimulated phenylethanol production when combined with other, previously documented, mutations that deregulate aromatic amino acid biosynthesis in S. cerevisiae. The resulting engineered S. cerevisiae strain produced >3 mm phenylethanol from glucose during growth on a simple synthetic medium. The strong impact of a transaminase deletion on intracellular amino acid concentrations opens new possibilities for yeast-based production of amino acid-derived products.

  11. Interfacially engineered oxygen octahedral rotations and their impact on strain relief in coherently grown SrRu O3 films

    Science.gov (United States)

    Kan, Daisuke; Wakabayashi, Yusuke; Tajiri, Hiroo; Shimakawa, Yuichi

    2016-07-01

    We report synchrotron x-ray diffraction investigations of interfacially engineered oxygen octahedral rotations and their impact on strain relief in perovskite SrRu O3 films. We show that octahedral rotations with distinct patterns and magnitudes can be accommodated into coherently grown films. The SrRu O3 film grown directly on the GdSc O3 substrate has the Ru O6 octahedral rotation with the a-b+c- pattern in the Glazer notation and the rotation angles of αrot=6.6 ±0 .2∘ , βrot=5.5 ±0 .2∘ , and γrot=3.6 ±0 .2∘ . On the other hand, when a 1-nm-thick BaTi O3 layer without Ti O6 rotations is inserted between the SrRu O3 and GdSc O3 , the SrRu O3 has the Ru O6 rotation with a-b0c+ , and αrot=5.6 ±0 .8∘ and γrot=3.6 ±0 .8∘ . These results indicate that there are some degrees of freedom in the octahedral rotations accommodated in SrRu O3 depending on the interface structure and that the γrot rotations play the important roles in the film's structural properties when the rotation about the [010] pc axis is blocked. We also found that the strain relief in the film is influenced by the interfacially engineered octahedral rotations. The interfacial BaTi O3 layer results in the in-plane periodic lattice modulation in the t-SRO film, allowing for the anisotropic relief of the substrate-induced strain. The results highlight the importance of the interface structure as a factor, determining not only octahedral rotations in coherently grown SRO films but also the strain reliefs in them.

  12. Multiplex engineering of industrial yeast genomes using CRISPRm.

    Science.gov (United States)

    Ryan, Owen W; Cate, Jamie H D

    2014-01-01

    Global demand has driven the use of industrial strains of the yeast Saccharomyces cerevisiae for large-scale production of biofuels and renewable chemicals. However, the genetic basis of desired domestication traits is poorly understood because robust genetic tools do not exist for industrial hosts. We present an efficient, marker-free, high-throughput, and multiplexed genome editing platform for industrial strains of S. cerevisiae that uses plasmid-based expression of the CRISPR/Cas9 endonuclease and multiple ribozyme-protected single guide RNAs. With this multiplex CRISPR (CRISPRm) system, it is possible to integrate DNA libraries into the chromosome for evolution experiments, and to engineer multiple loci simultaneously. The CRISPRm tools should therefore find use in many higher-order synthetic biology applications to accelerate improvements in industrial microorganisms.

  13. Advances in metabolic pathway and strain engineering paving the way for sustainable production of chemical building blocks.

    Science.gov (United States)

    Chen, Yun; Nielsen, Jens

    2013-12-01

    Bio-based production of chemical building blocks from renewable resources is an attractive alternative to petroleum-based platform chemicals. Metabolic pathway and strain engineering is the key element in constructing robust microbial chemical factories within the constraints of cost effective production. Here we discuss how the development of computational algorithms, novel modules and methods, omics-based techniques combined with modeling refinement are enabling reduction in development time and thus advance the field of industrial biotechnology. We further discuss how recent technological developments contribute to the development of novel cell factories for the production of the building block chemicals: adipic acid, succinic acid and 3-hydroxypropionic acid.

  14. Engineering control of bacterial cellulose production using a genetic toolkit and a new cellulose-producing strain.

    Science.gov (United States)

    Florea, Michael; Hagemann, Henrik; Santosa, Gabriella; Abbott, James; Micklem, Chris N; Spencer-Milnes, Xenia; de Arroyo Garcia, Laura; Paschou, Despoina; Lazenbatt, Christopher; Kong, Deze; Chughtai, Haroon; Jensen, Kirsten; Freemont, Paul S; Kitney, Richard; Reeve, Benjamin; Ellis, Tom

    2016-06-14

    Bacterial cellulose is a strong and ultrapure form of cellulose produced naturally by several species of the Acetobacteraceae Its high strength, purity, and biocompatibility make it of great interest to materials science; however, precise control of its biosynthesis has remained a challenge for biotechnology. Here we isolate a strain of Komagataeibacter rhaeticus (K. rhaeticus iGEM) that can produce cellulose at high yields, grow in low-nitrogen conditions, and is highly resistant to toxic chemicals. We achieved external control over its bacterial cellulose production through development of a modular genetic toolkit that enables rational reprogramming of the cell. To further its use as an organism for biotechnology, we sequenced its genome and demonstrate genetic circuits that enable functionalization and patterning of heterologous gene expression within the cellulose matrix. This work lays the foundations for using genetic engineering to produce cellulose-based materials, with numerous applications in basic science, materials engineering, and biotechnology.

  15. Engineering control of bacterial cellulose production using a genetic toolkit and a new cellulose-producing strain

    Science.gov (United States)

    Florea, Michael; Hagemann, Henrik; Santosa, Gabriella; Micklem, Chris N.; Spencer-Milnes, Xenia; de Arroyo Garcia, Laura; Paschou, Despoina; Lazenbatt, Christopher; Kong, Deze; Chughtai, Haroon; Jensen, Kirsten; Freemont, Paul S.; Kitney, Richard; Reeve, Benjamin; Ellis, Tom

    2016-01-01

    Bacterial cellulose is a strong and ultrapure form of cellulose produced naturally by several species of the Acetobacteraceae. Its high strength, purity, and biocompatibility make it of great interest to materials science; however, precise control of its biosynthesis has remained a challenge for biotechnology. Here we isolate a strain of Komagataeibacter rhaeticus (K. rhaeticus iGEM) that can produce cellulose at high yields, grow in low-nitrogen conditions, and is highly resistant to toxic chemicals. We achieved external control over its bacterial cellulose production through development of a modular genetic toolkit that enables rational reprogramming of the cell. To further its use as an organism for biotechnology, we sequenced its genome and demonstrate genetic circuits that enable functionalization and patterning of heterologous gene expression within the cellulose matrix. This work lays the foundations for using genetic engineering to produce cellulose-based materials, with numerous applications in basic science, materials engineering, and biotechnology. PMID:27247386

  16. Engineering control of bacterial cellulose production using a genetic toolkit and a new cellulose-producing strain.

    Science.gov (United States)

    Florea, Michael; Hagemann, Henrik; Santosa, Gabriella; Abbott, James; Micklem, Chris N; Spencer-Milnes, Xenia; de Arroyo Garcia, Laura; Paschou, Despoina; Lazenbatt, Christopher; Kong, Deze; Chughtai, Haroon; Jensen, Kirsten; Freemont, Paul S; Kitney, Richard; Reeve, Benjamin; Ellis, Tom

    2016-06-14

    Bacterial cellulose is a strong and ultrapure form of cellulose produced naturally by several species of the Acetobacteraceae Its high strength, purity, and biocompatibility make it of great interest to materials science; however, precise control of its biosynthesis has remained a challenge for biotechnology. Here we isolate a strain of Komagataeibacter rhaeticus (K. rhaeticus iGEM) that can produce cellulose at high yields, grow in low-nitrogen conditions, and is highly resistant to toxic chemicals. We achieved external control over its bacterial cellulose production through development of a modular genetic toolkit that enables rational reprogramming of the cell. To further its use as an organism for biotechnology, we sequenced its genome and demonstrate genetic circuits that enable functionalization and patterning of heterologous gene expression within the cellulose matrix. This work lays the foundations for using genetic engineering to produce cellulose-based materials, with numerous applications in basic science, materials engineering, and biotechnology. PMID:27247386

  17. Strain-Engineering the Gauge Potential of Dirac fermions in PECVD-grown Graphene

    Science.gov (United States)

    Hsu, Chen-Chih; Teague, Marcus; Wang, Jaiqing; Yeh, Nai-Chang

    Non-trivial strain can induce pseudo-magnetic fields in graphene so that the electronic properties of Dirac fermions can be tuned by controlling the strain on graphene. Here we employ nearly strain-free single-domain PECVD-graphene1 to induce controlled strain by placing graphene on nanostructured substrates. Strain-induced gauge potentials and pseudo-magnetic fields can be manifested by the local tunneling conductance peaks at quantized energies.2,3 Additionally, pseudo-magnetic field-induced local spontaneous time-reversal symmetry breaking can be revealed by spatially alternating presence and absence of the zero mode in the tunneling conductance spectra.2,3 We also employ molecular dynamics simulations to determine the spatial distribution of the pseudo-magnetic field for a given nanostructure. We find that a tetrahedron-like nanostructure can be an effective ``valley splitter'' to separate the trajectories of Dirac fermions of opposite pseudo-spins. Proper design and arrangement of several valley filters can function as a ``valley propagator'' to guide valley-polarized currents. We plan to verify the valley Hall effect associated with a valley splitter and to assess the feasibility of realistic valleytronic applications.

  18. Lung stress, strain, and energy load: engineering concepts to understand the mechanism of ventilator-induced lung injury (VILI).

    Science.gov (United States)

    Nieman, Gary F; Satalin, Joshua; Andrews, Penny; Habashi, Nader M; Gatto, Louis A

    2016-12-01

    It was recently shown that acute respiratory distress syndrome (ARDS) mortality has not been reduced in over 15 years and remains ~40 %, even with protective low tidal volume (LVt) ventilation. Thus, there is a critical need to develop novel ventilation strategies that will protect the lung and reduce ARDS mortality. Protti et al. have begun to analyze the impact of mechanical ventilation on lung tissue using engineering methods in normal pigs ventilated for 54 h. They used these methods to assess the impact of a mechanical breath on dynamic and static global lung strain and energy load. Strain is the change in lung volume in response to an applied stress (i.e., Tidal Volume-Vt). This study has yielded a number of exciting new concepts including the following: (1) Individual mechanical breath parameters (e.g., Vt or Plateau Pressure) are not directly correlated with VILI but rather any combination of parameters that subject the lung to excessive dynamic strain and energy/power load will cause VILI; (2) all strain is not equal; dynamic strain resulting in a dynamic energy load (i.e., kinetic energy) is more damaging to lung tissue than static strain and energy load (i.e., potential energy); and (3) a critical consideration is not just the size of the Vt but the size of the lung that is being ventilated by this Vt. This key concept merits attention since our current protective ventilation strategies are fixated on the priority of keeping the Vt low. If the lung is fully inflated, a large Vt is not necessarily injurious. In conclusion, using engineering concepts to analyze the impact of the mechanical breath on the lung is a novel new approach to investigate VILI mechanisms and to help design the optimally protective breath. Data generated using these methods have challenged some of the current dogma surrounding the mechanisms of VILI and of the components in the mechanical breath necessary for lung protection. PMID:27316442

  19. Characterizing Strain Variation in Engineered E. coli Using a Multi-Omics-Based Workflow

    DEFF Research Database (Denmark)

    Brunk, Elizabeth; George, Kevin W.; Alonso-Gutierrez, Jorge;

    2016-01-01

    Understanding the complex interactions that occur between heterologous and native biochemical pathways represents a major challenge in metabolic engineering and synthetic biology. We present a workflow that integrates metabolomics, proteomics, and genome-scale models of Escherichia coli metabolism...... to study the effects of introducing a heterologous pathway into a microbial host. This workflow incorporates complementary approaches from computational systems biology, metabolic engineering, and synthetic biology; provides molecular insight into how the host organism microenvironment changes due...

  20. Improvement of Ethanol Production in Saccharomyces cerevisiae by High-Efficient Disruption of the ADH2 Gene Using a Novel Recombinant TALEN Vector

    Science.gov (United States)

    Ye, Wei; Zhang, Weimin; Liu, Taomei; Tan, Guohui; Li, Haohua; Huang, Zilei

    2016-01-01

    Bioethanol is becoming increasingly important in energy supply and economic development. However, the low yield of bioethanol and the insufficiency of high-efficient genetic manipulation approaches limit its application. In this study, a novel transcription activator-like effector nuclease (TALEN) vector containing the left and right arms of TALEN was electroporated into Saccharomyces cerevisiae strain As2.4 to sequence the alcohol dehydrogenase gene ADH2 and the hygromycin-resistant gene hyg. Western blot analysis using anti-FLAG monoclonal antibody proved the successful expression of TALE proteins in As2.4 strains. qPCR and sequencing demonstrated the accurate knockout of the 17 bp target gene with 80% efficiency. The TALEN vector and ADH2 PCR product were electroporated into ΔADH2 to complement the ADH2 gene (ADH2+ As2.4). LC–MS and GC were employed to detect ethanol yields in the native As2.4, ΔADH2 As2.4, and ADH2+ As2.4 strains. Results showed that ethanol production was improved by 52.4 ± 5.3% through the disruption of ADH2 in As2.4. The bioethanol yield of ADH2+ As2.4 was nearly the same as that of native As2.4. This study is the first to report on the disruption of a target gene in S. cerevisiae by employing Fast TALEN technology to improve bioethanol yield. This work provides a novel approach for the disruption of a target gene in S. cerevisiae with high efficiency and specificity, thereby promoting the improvement of bioethanol production in S. cerevisiae by metabolic engineering. PMID:27462304

  1. Improvement of Ethanol Production in Saccharomyces cerevisiae by High-Efficient Disruption of the ADH2 Gene Using a Novel Recombinant TALEN Vector.

    Science.gov (United States)

    Ye, Wei; Zhang, Weimin; Liu, Taomei; Tan, Guohui; Li, Haohua; Huang, Zilei

    2016-01-01

    Bioethanol is becoming increasingly important in energy supply and economic development. However, the low yield of bioethanol and the insufficiency of high-efficient genetic manipulation approaches limit its application. In this study, a novel transcription activator-like effector nuclease (TALEN) vector containing the left and right arms of TALEN was electroporated into Saccharomyces cerevisiae strain As2.4 to sequence the alcohol dehydrogenase gene ADH2 and the hygromycin-resistant gene hyg. Western blot analysis using anti-FLAG monoclonal antibody proved the successful expression of TALE proteins in As2.4 strains. qPCR and sequencing demonstrated the accurate knockout of the 17 bp target gene with 80% efficiency. The TALEN vector and ADH2 PCR product were electroporated into ΔADH2 to complement the ADH2 gene (ADH2 (+) As2.4). LC-MS and GC were employed to detect ethanol yields in the native As2.4, ΔADH2 As2.4, and ADH2 (+) As2.4 strains. Results showed that ethanol production was improved by 52.4 ± 5.3% through the disruption of ADH2 in As2.4. The bioethanol yield of ADH2 (+) As2.4 was nearly the same as that of native As2.4. This study is the first to report on the disruption of a target gene in S. cerevisiae by employing Fast TALEN technology to improve bioethanol yield. This work provides a novel approach for the disruption of a target gene in S. cerevisiae with high efficiency and specificity, thereby promoting the improvement of bioethanol production in S. cerevisiae by metabolic engineering. PMID:27462304

  2. Expression of dehydrin gene from Arctic Cerastium arcticum increases abiotic stress tolerance and enhances the fermentation capacity of a genetically engineered Saccharomyces cerevisiae laboratory strain.

    Science.gov (United States)

    Kim, Il-Sup; Kim, Hyun-Young; Kim, Young-Saeng; Choi, Han-Gu; Kang, Sung-Ho; Yoon, Ho-Sung

    2013-10-01

    We investigated Arctic plants to determine if they have a specific mechanism enabling them to adapt to extreme environments because they are subject to such conditions throughout their life cycles. Among the cell defense systems of the Arctic mouse-ear chickweed Cerastium arcticum, we identified a stress-responsive dehydrin gene CaDHN that belongs to the SK5 subclass and contains conserved regions with one S segment at the N-terminus and five K segments from the N-terminus to the C-terminus. To investigate the molecular properties of CaDHN, the yeast Saccharomyces was transformed with CaDHN. CaDHN-expressing transgenic yeast (TG) cells recovered more rapidly from challenge with exogenous stimuli, including oxidants (hydrogen peroxide, menadione, and tert-butyl hydroperoxide), high salinity, freezing and thawing, and metal (Zn(2+)), than wild-type (WT) cells. TG cells were sensitive to copper, cobalt, and sodium dodecyl sulfate. In addition, the cell survival of TG cells was higher than that of WT cells when cells at the mid-log and stationary stages were exposed to increased ethanol concentrations. There was a significant difference in cultures that have an ethanol content >16 %. During glucose-based batch fermentation at generally used (30 °C) and low (18 °C) temperatures, TG cells produced a higher alcohol concentration through improved cell survival. Specifically, the final alcohol concentrations were 13.3 and 13.2 % in TG cells during fermentation at 30 and 18 °C, respectively, whereas they were 10.2 and 9.4 %, respectively, in WT cells under the same fermentation conditions. An in vitro assay revealed that purified CaDHN acted as a reactive oxygen species scavenger by neutralizing H2O2 and a chaperone by preventing high temperature-mediated catalase inactivation. Taken together, our results show that CaDHN expression in transgenic yeast confers tolerance to various abiotic stresses by improving redox homeostasis and enhances fermentation capacity, especially at low temperatures (18 °C). PMID:23377791

  3. Mead production: selection and characterization assays of Saccharomyces cerevisiae

    OpenAIRE

    de Pereira, Ana Paula; Dias, Teresa; Andrade, João Verdial; Ramalhosa, Elsa; Mendes-Ferreira, Ana; Mendes-Faia, Arlete; Leticia M. Estevinho

    2009-01-01

    Mead is a traditional alcoholic drink which results from the fermentation of diluted honey. Yeasts used in mead production are, usually, wine Saccharomyces cerevisiae strains. Most of these yeasts are not adapted to the conditions of mead production namely, high sugar levels, low pH values and reduced nitrogen concentrations. The inability of yeast strains to respond and adapt to unfavorable stressful growth conditions, leads to several problems, such as lack of uniformity of the final ...

  4. Strain engineering the magnetic states of vacancy-doped monolayer MoSe2

    International Nuclear Information System (INIS)

    Highlights: • The effects of vacancy defects and biaxial strain on the magnetic property of MoSe2 were investigated. • VSe, VSe2 and VMoSe3 vacancy doped MoSe2 monolayer are nonmagnetic, while VMoSe6 vacancy geometry shows magnetic moment. • The combined vacancy doping and tensile strain can effectively tune the magnetism in MoSe2 monolayer. - Abstract: The effect of vacancy defect and strain on the magnetic property of monolayer MoSe2 was investigated by the first-principles calculation. Firstly, the most stable structure of monolayer MoSe2 and four kinds of vacancy, VSe, VSe2, VMoSe3 and VMoSe6 geometries were systematically studied. Our calculations show that 1H-MoSe2, as well as VSe, VSe2 and VMoSe3 vacancy doped MoSe2 monolayer are nonmagnetic, while VMoSe6 vacancy geometry shows magnetism and the magnetic moment mainly comes from the six Mo atoms around the vacancy although it is most difficult to form. Meanwhile, our calculations indicate that MoSe2 monolayer under tensile strain ranging from 0% to 10% does not show any magnetism. However, it is found that the combined tensile strain and VSe, or VSe2 and VMoSe3 vacancy indeed induce magnetism in MoSe2 monolayer by breaking the Mo–Mo metallic bonds. As for VMoSe6 vacancy geometry, the vacancy induced magnetic moment decrease under the imposed tensile strain

  5. Strain-Engineering the Anisotropic Electrical Conductance of Few-Layer Black Phosphorus

    Science.gov (United States)

    Fei, Ruixiang; Yang, Li

    2014-05-01

    Newly fabricated monolayer phosphorene and its few-layer structures are expected to be promising for electronic and optical applications because of their finite direct band gaps and sizable but anisotropic electronic mobility. By first-principles simulations, we show that this unique anisotropic conductance can be controlled by using simple strain conditions. With the appropriate biaxial or uniaxial strain, we can rotate the preferred conducting direction by 90 degrees. This will be of useful for exploring quantum Hall effects, and exotic electronic and mechanical applications based on phosphorene.

  6. Heterooligomeric phosphoribosyl diphosphate synthase of Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Hove-Jensen, Bjarne

    2004-01-01

    The yeast Saccharomyces cerevisiae contains five phosphoribosyl diphosphate (PRPP) synthase-homologous genes (PRS1-5), which specify PRPP synthase subunits 1-5. Expression of the five S. cerevisiae PRS genes individually in an Escherichia coli PRPP-less strain (Deltaprs) showed that a single PRS...... gene product had no PRPP synthase activity. In contrast, expression of five pairwise combinations of PRS genes resulted in the formation of active PRPP synthase. These combinations were PRS1 PRS2, PRS1 PRS3, and PRS1 PRS4, as well as PRS5 PRS2 and PRS5 PRS4. None of the remaining five possible pairwise...... combinations of PRS genes appeared to produce active enzyme. Extract of an E. coli strain containing a plasmid-borne PRS1 gene and a chromosome-borne PRS3 gene contained detectable PRPP synthase activity, whereas extracts of strains containing PRS1 PRS2, PRS1 PRS4, PRS5 PRS2, or PRS5 PRS4 contained...

  7. Engineering and systems level analysis of Saccharomyces cerevisiae for production of 3 hydroxypropionic acid via malonyl CoA reductase dependent pathway

    DEFF Research Database (Denmark)

    Kildegaard, Kanchana Rueksomtawin; Jensen, Niels Bjerg; Schneider, Konstantin;

    2016-01-01

    In the future, oil- and gas-derived polymers may be replaced with bio-based polymers, produced from renewable feedstocks using engineered cell factories. Acrylic acid and acrylic esters with an estimated world annual production of approximately 6 million tons by 2017 can be derived from 3-hydroxy......-hydroxypropionic acid (3HP), which can be produced by microbial fermentation. For an economically viable process 3HP must be produced at high titer, rate and yield and preferably at low pH to minimize downstream processing costs....

  8. In Vitro Fermentation Characteristics and Rumen Microbial Population of Diet Supplemented with Saccharomyces cerevisiae and Rumen Microbe Probiotics

    Directory of Open Access Journals (Sweden)

    L. Riyanti

    2016-04-01

    Full Text Available The objective of this study was to select three strains of probiotic Saccharomyces cerevisiae and to evaluate the effect of S. cerevisiae and rumen bacteria isolate (MR4 supplementation and their combination on rumen fermentability and rumen microbial population. Experiment 1 was designed in a 4 x 5 factorial randomized block design with 3 replications. The first factor was S. cerevisiae strain consisted of control treatment (without S. cerevisiae supplementation, NBRC 10217, NRRL Y 567 and NRRL 12618, and the second factor was incubation time consisted of 0, 1, 2, 3, and 4 h. Ration was basal ration for feedlot with forage to concentrate ratio (F:C= 60:40. Dosage of each treatment with S. cerevisiae was 5 x 1010 cfu/kg ration. Experiment 2 was designed in randomized block design with 4 treatments: P0= basal ration of feedlot; P1= P0 + S. cerevisiae; P2= P0 + MR4 isolate (5 x 107 cfu/kg ration; P3= P0 + S. cerevisiae and MR4 isolate. The result of experiment 1 showed that supplementation of S. cerevisiae NRRL 12618 had the highest S. cerevisiae population and increased rumen bacterial population. This strain was selected as probiotic in experiment 2. The result from experiment 2 showed that probiotic supplementation stabilized rumen pH and produced the highest NH3 concentration (P<0.05 and bacterial population (P<0.05. As compared with control, all treatments reduced protozoa population (P<0.05. Combination of S. cerevisiae and MR4 probiotics produced the highest total volatile fatty acids (VFA and isovalerate (P<0.05. It was concluded that strain S. cerevisiae NRRL 12618 had potential as probiotic yeast. Supplementation with this strain increased fermentability, rumen isoacid and decreased A:P ratio. Those abilities could be improved with MR4 rumen isolate probiotic.

  9. Improved growth and ethanol fermentation of Saccharomyces cerevisiae in the presence of acetic acid by overexpression of SET5 and PPR1.

    Science.gov (United States)

    Zhang, Ming-Ming; Zhao, Xin-Qing; Cheng, Cheng; Bai, Feng-Wu

    2015-12-01

    To better understand the contribution of zinc-finger proteins to environmental stress tolerance, particularly inhibition from acetic acid, which is a potent inhibitor for cellulosic ethanol production by microbial fermentations, SET5 and PPR1 were overexpressed in Saccharomyces cerevisiae BY4741. With 5 g/L acetic acid addition, engineered strains BY4741/SET5 and BY4741/PPR1 showed improved growth and enhanced ethanol fermentation performance compared to that with the control strain. Similar results were also observed in ethanol production using corn stover hydrolysate. Further studies indicated that SET5 and PPR1 overexpression in S. cerevisiae significantly improved activities of antioxidant enzymes and ATP generation in the presence of acetic acid, and consequently decreased intracellular accumulation of reactive oxygen species (50.9 and 45.7%, respectively). These results revealed the novel functions of SET5 and PPR1 for the improvement of yeast acetic acid tolerance, and also implicated the involvement of these proteins in oxidative stress defense and energy metabolism in S. cerevisiae. This work also demonstrated that overexpression of SET5 and PPR1 would be a feasible strategy to increase cellulosic ethanol production efficiency.

  10. Accumulation of gold using Baker's yeast, Saccharomyces cerevisiae

    International Nuclear Information System (INIS)

    Authors have reported preconcentration of 152Eu, a long-lived fission product, by yeast cells, Saccharomyces cerevisiae. Gold being a precious metal is used in electroplating, hydrogenation catalyst, etc. Heterogeneous composition of samples and low concentration offers renewed interest in its selective extraction of gold using various extractants. Gold can be recovered from different solutions using various chemical reagents like amines, organophosphorus compounds, and extractants containing sulphur as donor atom, etc. In the present work, two different strains of baker's yeast, Saccharomyces cerevisiae have been used to study the preconcentration of gold at various experimental conditions

  11. Directed Evolution towards Increased Isoprenoid Production in Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Carlsen, Simon; Nielsen, Michael Lynge; Kielland-Brandt, Morten;

    diversity. The most common way of producing these compounds is by organic synthesis. Organic synthesis does however have several disadvantages for production of secondary metabolites such as low yields due to the complex structures, which makes this way of production economically unfeasible. Microbial...... for discovering new genetic perturbations, which would results in and increased production of isoprenoids by S. cerevisiae has been very limited. This project is focus on creating diversity within a lycopene producing S. cerevisiae strain by construction of gDNA-, cDNA-, and transposon-libraries. The diversified...

  12. Growth of non-Saccharomyces yeasts affects nutrient availability for Saccharomyces cerevisiae during wine fermentation.

    Science.gov (United States)

    Medina, Karina; Boido, Eduardo; Dellacassa, Eduardo; Carrau, Francisco

    2012-07-01

    Yeast produces numerous secondary metabolites during fermentation that impact final wine quality. Although it is widely recognized that growth of diverse non-Saccharomyces (NS) yeast can positively affect flavor complexity during Saccharomyces cerevisiae wine fermentation, the inability to control spontaneous or co-fermentation processes by NS yeast has restricted their use in winemaking. We selected two NS yeasts from our Uruguayan native collection to study NS-S. cerevisiae interactions during wine fermentation. The selected strains of Hanseniaspora vineae and Metschnikowia pulcherrima had different yeast assimilable nitrogen consumption profiles and had different effects on S. cerevisiae fermentation and growth kinetics. Studies in which we varied inoculum size and using either simultaneous or sequential inoculation of NS yeast and S. cerevisiae suggested that competition for nutrients had a significant effect on fermentation kinetics. Sluggish fermentations were more pronounced when S. cerevisiae was inoculated 24h after the initial stage of fermentation with a NS strain compared to co-inoculation. Monitoring strain populations using differential WL nutrient agar medium and fermentation kinetics of mixed cultures allowed for a better understanding of strain interactions and nutrient addition effects. Limitation of nutrient availability for S. cerevisiae was shown to result in stuck fermentations as well as to reduce sensory desirability of the resulting wine. Addition of diammonium phosphate (DAP) and a vitamin mix to a defined medium allowed for a comparison of nutrient competition between strains. Addition of DAP and the vitamin mix was most effective in preventing stuck fermentations. PMID:22687186

  13. Measurements of Creep Internal Stress Based on Constant Strain Rate and Its Application to Engineering

    Institute of Scientific and Technical Information of China (English)

    TAO Wen-liang; WEI Tao

    2006-01-01

    This research is carried out on the basis of Constant Strain Rate(CSR) to measure creep internal stress. Measurements of creep internal stress are conducted on the material test machine by using the CSR method. A mathematical model of creep internal stress is also proposed and its application is presented in this paper.

  14. Capturing of the monoterpene olefin limonene produced in Saccharomyces cerevisiae.

    Science.gov (United States)

    Jongedijk, Esmer; Cankar, Katarina; Ranzijn, Jorn; van der Krol, Sander; Bouwmeester, Harro; Beekwilder, Jules

    2015-01-01

    Monoterpene olefins such as limonene are plant compounds with applications as flavouring and fragrance agents, as solvents and potentially also in polymer and fuel chemistry. We engineered baker's yeast Saccharomyces cerevisiae to express a (-)-limonene synthase from Perilla frutescens and a (+)-limonene synthase from Citrus limon. Both proteins were expressed either with their native plastid targeting signal or in a truncated form in which the plastidial sorting signal was removed. The yeast host strain for expression was AE9 K197G, which expresses a mutant Erg20 enzyme. This enzyme catalyses the formation of geranyl diphosphate, which is the precursor for monoterpenes. Several methods were tested to capture limonene produced by the yeast. Extraction from the culture medium by pentane, or by the addition of CaCl2 followed by solid-phase micro-extraction, did not lead to detectable limonene, indicating that limonene is rapidly lost from the culture medium. Volatile terpenes such as limonene may also be trapped in a dodecane phase added to the medium during fermentation. This method resulted in recovery of 0.028 mg/l (+)-limonene and 0.060 mg/l (-)-limonene in strains using the truncated Citrus and Perilla synthases, respectively. Trapping the headspace during culture of the limonene synthase-expressing strains resulted in higher titres, at 0.12 mg/l (+)-limonene and 0.49 mg/l (-)-limonene. These results show that the volatile properties of the olefins produced require specific methods for efficient recovery of these molecules from biotechnological production systems.

  15. Simultaneous saccharification and co-fermentation of aqueous ammonia pretreated corn stover with an engineered Saccharomyces cerevisiae SyBE005.

    Science.gov (United States)

    Zhu, Jia-Qing; Qin, Lei; Li, Bing-Zhi; Yuan, Ying-Jin

    2014-10-01

    Co-fermentation of glucose and xylose from lignocelluloses is an efficient approach to increasing ethanol production. Simultaneous saccharification and co-fermentation (SSCF) of corn stover pretreated with aqueous ammonia was performed using engineered yeast with xylose utilization pathway. Thus far, the effect of the several key factors on SSCF was investigated, including temperature, inoculation size, pre-hydrolysis and pH. Ethanol concentration was achieved to 36.5 g/L during SSCF process with 6% glucan loading. The addition of Tween 20 reduced enzyme loading, i.e., from 15 to 7.5 FPU/gglucan with the same final ethanol concentration. The ethanol concentration was achieved to 70.1g/L at 12% glucan loading. Yeast feeding, combined with substrate and enzyme feeding, was proved to be an efficient approach for SSCF with high solid loading. PMID:25016219

  16. Escherichia coli W as a new platform strain for the enhanced production of L-valine by systems metabolic engineering.

    Science.gov (United States)

    Park, Jin Hwan; Jang, Yu-Sin; Lee, Jeong Wook; Lee, Sang Yup

    2011-05-01

    A less frequently employed Escherichia coli strain W, yet possessing useful metabolic characteristics such as less acetic acid production and high L-valine tolerance, was metabolically engineered for the production of L-valine. The ilvA gene was deleted to make more pyruvate, a key precursor for L-valine, available for enhanced L-valine biosynthesis. The lacI gene was deleted to allow constitutive expression of genes under the tac or trc promoter. The ilvBN(mut) genes encoding feedback-resistant acetohydroxy acid synthase (AHAS) I and the L-valine biosynthetic ilvCED genes encoding acetohydroxy acid isomeroreductase, dihydroxy acid dehydratase, and branched chain amino acid aminotransferase, respectively, were amplified by plasmid-based overexpression. The global regulator Lrp and L-valine exporter YgaZH were also amplified by plasmid-based overexpression. The engineered E. coli W (ΔlacI ΔilvA) strain overexpressing the ilvBN(mut) , ilvCED, ygaZH, and lrp genes was able to produce an impressively high concentration of 60.7 g/L L-valine by fed-batch culture in 29.5 h, resulting in a high volumetric productivity of 2.06 g/L/h. The most notable finding is that there was no other byproduct produced during L-valine production. The results obtained in this study suggest that E. coli W can be a good alternative to Corynebacterium glutamicum and E. coli K-12, which have so far been the most efficient L-valine producer. Furthermore, it is expected that various bioproducts including other amino acids might be more efficiently produced by this revisited platform strain of E. coli.

  17. CRISPR-PCS: a powerful new approach to inducing multiple chromosome splitting in Saccharomyces cerevisiae

    Science.gov (United States)

    Sasano, Yu; Nagasawa, Koki; Kaboli, Saeed; Sugiyama, Minetaka; Harashima, Satoshi

    2016-01-01

    PCR-mediated chromosome splitting (PCS) was developed in the yeast Saccharomyces cerevisiae. It is based on homologous recombination and enables division of a chromosome at any point to form two derived and functional chromosomes. However, because of low homologous recombination activity, PCS is limited to a single site at a time, which makes the splitting of multiple loci laborious and time-consuming. Here we have developed a highly efficient and versatile chromosome engineering technology named CRISPR-PCS that integrates PCS with the novel genome editing CRISPR/Cas9 system. This integration allows PCS to utilize induced double strand breaks to activate homologous recombination. CRISPR-PCS enhances the efficiency of chromosome splitting approximately 200-fold and enables generation of simultaneous multiple chromosome splits. We propose that CRISPR-PCS will be a powerful tool for breeding novel yeast strains with desirable traits for specific industrial applications and for investigating genome function. PMID:27530680

  18. Electrochemical Probing of in Vivo 5-Hydroxymethyl Furfural Reduction in Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Kostesha, Natalie; Almeida, J.R.M.; Heiskanen, Arto;

    2009-01-01

    In this work, mediated amperometry was used to evaluate whether differences in intracellular nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) level could be observed between a genetically modified Saccharomyces cerevisiae strain, engineered for NADPH dependent 5-hydroxymethyl-2-furaldehyde...... amperometric signal during real-time monitoring of the concentration dependent HMF reduction in living cells could be translated into the cellular enzyme kinetic parameters: K-M,cell(app), V-MAX, k(cat,cell), and k(cat,cell)/K-M,cell(app). The results indicated that the overexpression of the ADH6 gene gave...... a 68% decrease in K-M,cell(app), and 42% increase in V-MAX, resulting in a 4-fold increase in k(cat,cell)/K-M,cell(app). These results demonstrate that the mediated amperometric method is useful for monitoring the short-term dynamics of NAD(P)H variations and determining cellular enzyme kinetic...

  19. Essential validation methods for E. coli strains created by chromosome engineering

    NARCIS (Netherlands)

    Krishnan, S.T.; Moolman, M.C.; Van Laar, T.; Meyer, A.S.; Dekker, N.H.

    2015-01-01

    Background Chromosome engineering encompasses a collection of homologous recombination-based techniques that are employed to modify the genome of a model organism in a controlled fashion. Such techniques are widely used in both fundamental and industrial research to introduce multiple insertions in

  20. Postgrowth intermixing of strain engineered InAs/GaAs quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Nasr, O.; Hadj Alouane, M.H. [Université de Monastir, Laboratoire de Micro-Optoélectronique et Nanostructures, Faculté des Sciences, Avenue de l’environnement, 5019 Monastir (Tunisia); Ilahi, B., E-mail: bouraoui.ilahi@gmail.com [Université de Monastir, Laboratoire de Micro-Optoélectronique et Nanostructures, Faculté des Sciences, Avenue de l’environnement, 5019 Monastir (Tunisia); Department of Physics and Astronomy, College of Sciences, King Saud University, 11451 Riyadh (Saudi Arabia); Salem, B. [Laboratoire des Technologies de la Microélectronique (LTM)–UMR 5129 CNRS-UJF, CEA Grenoble, 17 Rue des Martyrs, F-38054 Grenoble (France); Sfaxi, L.; Maaref, H. [Université de Monastir, Laboratoire de Micro-Optoélectronique et Nanostructures, Faculté des Sciences, Avenue de l’environnement, 5019 Monastir (Tunisia)

    2014-12-05

    Highlights: • The InAs QDs in a pure GaAs matrix are more sensitive to the RTA temperature allowing the highest emission energy blueshift. • Reducing of the intermixing degree by using DWELL structure. • In segregation and accumulation in the InGaAs underlying layer alter the structural and morphological properties of the QDs. • The intermixing is found to be partially prohibited for QDs grown on InGaAs strain reducing layer. - Abstract: This paper reports on the evolution of InAs/GaAs quantum dots’ (QDs) intermixing process depending on the QD position with respect to the InGaAs strain reducing layer. The postgrowth intermixing has been ensured by rapid thermal annealing (RTA) at different temperatures and the processed samples were investigated by photoluminescence (PL) spectroscopy. The reference sample, containing InAs QDs in pure GaAs matrix, demonstrates the highest intermixing degree with an emission energy blueshift up to 300 meV. The reduction of the strain around the QDs for dot-in-well (DWELL) structure has been found to slightly reduces the intermixing degree leading to less emission energy blue shift. However, for the QDs with InGaAs underlying layer, a relative prohibition of the intermixing has been found to occur testifying the existing of thermally stable extended defects.

  1. Creation of High-Yield Polyhydroxyalkanoates Engineered Strains by Low Energy Ion Implantation

    Institute of Scientific and Technical Information of China (English)

    QIAN Shiquan; CHENG Ying; ZHU Suwen; CHENG Beijiu

    2008-01-01

    Polyhydroxyalkanoates (PHAs), as a candidate for biodegradable plastic materials, can be synthesized by numerous microorganisms. However, as its production cost is high in comparison with those of chemically synthesized plastics, a lot of research has been focused on the efficient production of PHAs using different methods. In the present study, the mutation effects of PHAs production in strain pCB4 were investigated with implantation of low energy ions. It was found that under the implantation conditions of 7.8×1014 N+/cm2 at 10 keV, a high-yield PHAs strain with high genetic stability was generated from many mutants. After optimizing its fermentation conditions, the biomass, PHAs concentration and PHAs content of pCBH4reached 2.26 g/L, 1.81 g/L, and 80.08% respectively, whereas its wild type controls were about 1.24 g/L, 0.61 g/L, and 49.20%. Moreover, the main constituent of PHAs was identified as poly-3-hydroxybutyrates (PHB) in the mutant stain and the yield of this compound was increased up to 41.33% in contrast to that of 27.78% in the wild type strain.

  2. Creation of High-Yield Polyhydroxyalkanoates Engineered Strains by Low Energy Ion Implantation

    Science.gov (United States)

    Qian, Shiquan; Cheng, Ying; Zhu, Suwen; Cheng, Beijiu

    2008-12-01

    Polyhydroxyalkanoates (PHAs), as a candidate for biodegradable plastic materials, can be synthesized by numerous microorganisms. However, as its production cost is high in comparison with those of chemically synthesized plastics, a lot of research has been focused on the efficient production of PHAs using different methods. In the present study, the mutation effects of PHAs production in strain pCB4 were investigated with implantation of low energy ions. It was found that under the implantation conditions of 7.8 × 1014 N+/cm2 at 10 keV, a high-yield PHAs strain with high genetic stability was generated from many mutants. After optimizing its fermentation conditions, the biomass, PHAs concentration and PHAs content of pCBH4 reached 2.26 g/L, 1.81 g/L, and 80.08% respectively, whereas its wild type controls were about 1.24 g/L, 0.61 g/L, and 49.20%. Moreover, the main constituent of PHAs was identified as poly-3-hydroxybutyrates (PHB) in the mutant stain and the yield of this compound was increased up to 41.33% in contrast to that of 27.78% in the wild type strain.

  3. Reconstruction of the carnitine biosynthesis pathway from Neurospora crassa in the yeast Saccharomyces cerevisiae.

    Science.gov (United States)

    Franken, Jaco; Burger, Anita; Swiegers, Jan H; Bauer, Florian F

    2015-08-01

    Industrial synthesis of L-carnitine is currently performed by whole-cell biotransformation of industrial waste products, mostly D-carnitine and cronobetaine, through specific bacterial species. No comparable system has been established using eukaryotic microorganisms, even though there is a significant and growing international demand for either the pure compound or carnitine-enriched consumables. In eukaryotes, including the fungus Neurospora crassa, L-carnitine is biosynthesized through a four-step metabolic conversion of trimethyllysine to L-carnitine. In contrast, the industrial yeast, Saccharomyces cerevisiae lacks the enzymes of the eukaryotic biosynthesis pathway and is unable to synthesize carnitine. This study describes the cloning of all four of the N. crassa carnitine biosynthesis genes and the reconstruction of the entire pathway in S. cerevisiae. The engineered yeast strains were able to catalyze the synthesis of L-carnitine, which was quantified using hydrophilic interaction liquid chromatography electrospray ionization mass spectrometry (HILIC-ESI-MS) analyses, from trimethyllysine. Furthermore, the yeast threonine aldolase Gly1p was shown to effectively catalyze the second step of the pathway, fulfilling the role of a serine hydroxymethyltransferase. The analyses also identified yeast enzymes that interact with the introduced pathway, including Can1p, which was identified as the yeast transporter for trimethyllysine, and the two yeast serine hydroxymethyltransferases, Shm1p and Shm2p. Together, this study opens the possibility of using an engineered, carnitine-producing yeast in various industrial applications while providing insight into possible future strategies aimed at tailoring the production capacity of such strains.

  4. Applied systems biology - vanillin production in Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Strucko, Tomas; Eriksen, Jens Christian; Nielsen, J.;

    2012-01-01

    Vanillin is the most important aroma compound based on market value, and natural vanillin is extracted from the cured seed pods of the Vanilla orchid. Most of the world’s vanillin, however, is obtained by chemical synthesis from petrochemicals or wood pulp lignins. As an alternative, de novo...... biosynthesis of vanillin in baker’s yeast Saccharomyces cerevisiae was recently demonstrated by successfully introducing the metabolic pathway for vanillin production in yeast. Nevertheless, the amount of vanillin produced in this S. cerevisiae strain is insufficient for commercial production and improvements...... need to be done. We have introduced the genes necessary for vanillin production in an identical manner in two different yeast strains S288c and CEN.PK,where comprehensive – omics datasets are available, hence, allowing vanillin production in the two strain backgrounds to be evaluated and compared...

  5. Biosynthesis of levan, a bacterial extracellular polysaccharide, in the yeast Saccharomyces cerevisiae.

    Science.gov (United States)

    Franken, Jaco; Brandt, Bianca A; Tai, Siew L; Bauer, Florian F

    2013-01-01

    Levans are fructose polymers synthesized by a broad range of micro-organisms and a limited number of plant species as non-structural storage carbohydrates. In microbes, these polymers contribute to the formation of the extracellular polysaccharide (EPS) matrix and play a role in microbial biofilm formation. Levans belong to a larger group of commercially important polymers, referred to as fructans, which are used as a source of prebiotic fibre. For levan, specifically, this market remains untapped, since no viable production strategy has been established. Synthesis of levan is catalysed by a group of enzymes, referred to as levansucrases, using sucrose as substrate. Heterologous expression of levansucrases has been notoriously difficult to achieve in Saccharomyces cerevisiae. As a strategy, this study used an invertase (Δsuc2) null mutant and two separate, engineered, sucrose accumulating yeast strains as hosts for the expression of the levansucrase M1FT, previously cloned from Leuconostoc mesenteroides. Intracellular sucrose accumulation was achieved either by expression of a sucrose synthase (Susy) from potato or the spinach sucrose transporter (SUT). The data indicate that in both Δsuc2 and the sucrose accumulating strains, the M1FT was able to catalyse fructose polymerisation. In the absence of the predicted M1FT secretion signal, intracellular levan accumulation was significantly enhanced for both sucrose accumulation strains, when grown on minimal media. Interestingly, co-expression of M1FT and SUT resulted in hyper-production and extracellular build-up of levan when grown in rich medium containing sucrose. This study presents the first report of levan production in S. cerevisiae and opens potential avenues for the production of levan using this well established industrial microbe. Furthermore, the work provides interesting perspectives when considering the heterologous expression of sugar polymerizing enzymes in yeast. PMID:24147008

  6. Biosynthesis of levan, a bacterial extracellular polysaccharide, in the yeast Saccharomyces cerevisiae.

    Directory of Open Access Journals (Sweden)

    Jaco Franken

    Full Text Available Levans are fructose polymers synthesized by a broad range of micro-organisms and a limited number of plant species as non-structural storage carbohydrates. In microbes, these polymers contribute to the formation of the extracellular polysaccharide (EPS matrix and play a role in microbial biofilm formation. Levans belong to a larger group of commercially important polymers, referred to as fructans, which are used as a source of prebiotic fibre. For levan, specifically, this market remains untapped, since no viable production strategy has been established. Synthesis of levan is catalysed by a group of enzymes, referred to as levansucrases, using sucrose as substrate. Heterologous expression of levansucrases has been notoriously difficult to achieve in Saccharomyces cerevisiae. As a strategy, this study used an invertase (Δsuc2 null mutant and two separate, engineered, sucrose accumulating yeast strains as hosts for the expression of the levansucrase M1FT, previously cloned from Leuconostoc mesenteroides. Intracellular sucrose accumulation was achieved either by expression of a sucrose synthase (Susy from potato or the spinach sucrose transporter (SUT. The data indicate that in both Δsuc2 and the sucrose accumulating strains, the M1FT was able to catalyse fructose polymerisation. In the absence of the predicted M1FT secretion signal, intracellular levan accumulation was significantly enhanced for both sucrose accumulation strains, when grown on minimal media. Interestingly, co-expression of M1FT and SUT resulted in hyper-production and extracellular build-up of levan when grown in rich medium containing sucrose. This study presents the first report of levan production in S. cerevisiae and opens potential avenues for the production of levan using this well established industrial microbe. Furthermore, the work provides interesting perspectives when considering the heterologous expression of sugar polymerizing enzymes in yeast.

  7. Lipopeptide Antibiotics Produced by the Engineered Strain Bacillus subtilis GEB3 and Detection of Its Bioactivity

    Institute of Scientific and Technical Information of China (English)

    GAO Xue-wen; YAO Shi-yi; Huong Pham; Joachim Vater; WANG Jin-sheng

    2004-01-01

    MALDI-TOF-MS technology was used for identification of lipopeptide antibiotics produced by GEB3 strain,a derivative of Bacillus subtilis 168 which was transformed by lpaB3gene.The result showed GEB3 only produced lipopeptide antibiotic surfactin.The analysis by LC-MS demonstrated that GEB3 produced standard surfactin isoforms with side chain lengths of 13,14 and 15 carbon atoms.The bioactivity detection of surfactin indicated that the surfactin produced by GEB3 had inhibition effect on plant pathogens Rhizoctonia solani and Pyricularia oryzae.

  8. Process engineering and scale-up of autotrophic Clostridium strain P11 syngas fermentation

    Science.gov (United States)

    Kundiyana, Dimple Kumar Aiyanna

    Scope and Method of Study. Biomass gasification followed by fermentation of syngas to ethanol is a potential process to produce bioenergy. The process is currently being researched under laboratory- and pilot-scale in an effort to optimize the process conditions and make the process feasible for commercial production of ethanol and other biofuels such as butanol and propanol. The broad research objectives for the research were to improve ethanol yields during syngas fermentation and to design a economical fermentation process. The research included four statistically designed experimental studies in serum bottles, bench-scale and pilot-scale fermentors to screen alternate fermentation media components, to determine the effect of process parameters such as pH, temperature and buffer on syngas fermentation, to determine the effect of key limiting nutrients of the acetyl-CoA pathway in a continuous series reactor design, and to scale-up the syngas fermentation in a 100-L pilot scale fermentor. Findings and Conclusions. The first experimental study identified cotton seed extract (CSE) as a feasible medium for Clostridium strain P11 fermentation. The study showed that CSE at 0.5 g L-1 can potentially replace all the standard Clostridium strain P11 fermentation media components while using a media buffer did not significantly improve the ethanol production when used in fermentation with CSE. Scale-up of the CSE fermentation in 2-L and 5-L stirred tank fermentors showed 25% increase in ethanol yield. The second experimental study showed that syngas fermentation at 32°C without buffer was associated with higher ethanol concentration and reduced lag time in switching to solventogenesis. Conducting fermentation at 40°C or by lowering incubation pH to 5.0 resulted in reduced cell growth and no production of ethanol or acetic acid. The third experiment studied the effect of three limiting nutrients, calcium pantothenate, vitamin B12 and CoCl2 on syngas fermentation. Results

  9. Response of Saccharomyces cerevisiae to cadmium stress

    Energy Technology Data Exchange (ETDEWEB)

    Moreira, Luciana Mara Costa; Ribeiro, Frederico Haddad; Neves, Maria Jose [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil). Lab. de Radiobiologia], e-mail: luamatu@uol.com.br; Porto, Barbara Abranches Araujo; Amaral, Angela M.; Menezes, Maria Angela B.C. [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Lab. de Ativacao Neutronica], e-mail: menezes@cdtn.br; Rosa, Carlos Augusto [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Microbiologia], e-mail: carlrosa@icb.ufmg

    2009-07-01

    The intensification of industrial activity has been greatly contributing with the increase of heavy metals in the environment. Among these heavy metals, cadmium becomes a serious pervasive environmental pollutant. The cadmium is a heavy metal with no biological function, very toxic and carcinogenic at low concentrations. The toxicity of cadmium and several other metals can be mainly attributed to the multiplicity of coordination complexes and clusters that they can form. Some aspects of the cellular response to cadmium were extensively investigated in the yeast Saccharomyces cerevisiae. The primary site of interaction between many toxic metals and microbial cells is the plasma membrane. Plasma-membrane permeabilisation has been reported in a variety of microorganisms following cadmium exposure, and is considered one mechanism of cadmium toxicity in the yeast. In this work, using the yeast strain S. cerevisiae W303-WT, we have investigated the relationships between Cd uptake and release of cellular metal ions (K{sup +} and Na{sup +}) using neutron activation technique. The neutron activation was an easy, rapid and suitable technique for doing these metal determinations on yeast cells; was observed the change in morphology of the strains during the process of Cd accumulation, these alterations were observed by Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) during incorporation of cadmium. (author)

  10. Studying the Vibrostressed State of the Elements of Gas Turbine Engine Using a High Temperature Film-Type Resistance Strain Gauge

    OpenAIRE

    ГУСЕВ Ю.А.; Кахраи, Камбиз; Прочан, Г. А.; ЯКОВЛЕВ Ю.А.

    2015-01-01

    The conditions under which the vibrostressed state of the turbine blades of gas turbine engine (GTE) is investigated using the resistance strain gauge have been given. The consideration was given to resistance strain gauge with the film sensitive platinum and metal ceramic-based elements and the substrate-type isolator made of high temperature cement of a phosphate hardening and the methods of the investigation of the vibrodeformations of GTE elements including their application. The vibratio...

  11. The crack tip opening displacement and J integral under strain control and fully plastic conditions estimated by the engineering treatment model for plane stress tension

    Energy Technology Data Exchange (ETDEWEB)

    Schwalbe, K.H. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Materialforschung

    1995-12-31

    The Engineering Treatment Model (ETM) relates the crack tip opening displacement (CTOD) and the J integral with the applied load or applied strain using a geometry independent, master-curve-type, equation. In the present paper, CTOD and J were examined as a function of the applied strain by means of comparing ETM predictions with earlier experimental and numerical results. A comparison was also made with a theoretical solution by Shih and Hutchinson. It was concluded that the ETM provides useful engineering approximations. (orig.)

  12. Heterologous expression of MlcE in Saccharomyces cerevisiae provides resistance to natural and semi-synthetic statins

    Directory of Open Access Journals (Sweden)

    Ana Ley

    2015-12-01

    Full Text Available Statins are inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase, the key enzyme in cholesterol biosynthesis. Their extensive use in treatment and prevention of cardiovascular diseases placed statins among the best selling drugs. Construction of Saccharomyces cerevisiae cell factory for the production of high concentrations of natural statins will require establishment of a non-destructive self-resistance mechanism to overcome the undesirable growth inhibition effects of statins. To establish active export of statins from yeast, and thereby detoxification, we integrated a putative efflux pump-encoding gene mlcE from the mevastatin-producing Penicillium citrinum into the S. cerevisiae genome. The resulting strain showed increased resistance to both natural statins (mevastatin and lovastatin and semi-synthetic statin (simvastatin when compared to the wild type strain. Expression of RFP-tagged mlcE showed that MlcE is localized to the yeast plasma and vacuolar membranes. We provide a possible engineering strategy for improvement of future yeast based production of natural and semi-synthetic statins.

  13. Field longevity of a fluorescent protein marker in an engineered strain of the pink bollworm, Pectinophora gossypiella (Saunders.

    Directory of Open Access Journals (Sweden)

    Michelle Walters

    Full Text Available The cotton pest, pink bollworm (Pectinophora gossypiella (Saunders, is a significant pest in most cotton-growing areas around the world. In southwestern USA and northern Mexico, pink bollworm is the target of the sterile insect technique (SIT, which relies on the mass-release of sterile pink bollworm adults to over-flood the wild population and thereby reduce it over time. Sterile moths reared for release are currently marked with a dye provided in their larval diet. There are concerns, however, that this marker fails from time to time, leading to sterile moths being misidentified in monitoring traps as wild moths. This can lead to expensive reactionary releases of sterile moths. We have developed a genetically marked strain that is engineered to express a fluorescent protein, DsRed2, which is easily screened under a specialised microscope. In order to test this marker under field conditions, we placed wild-type and genetically marked moths on traps and placed them in field cages. The moths were then screened, in a double-blind fashion, for DsRed2 fluorescence at regular intervals to determine marker reliability over time. The marker was shown to be robust in very high temperatures and generally proved reliable for a week or longer. More importantly, genotyping of moths on traps by PCR screening of the moths was 100% correct. Our findings indicate that this strain--and fluorescent protein markers in general--could make a valuable contribution to SIT.

  14. Conversion of orange peel to L-galactonic acid in a consolidated process using engineered strains of Aspergillus niger

    Science.gov (United States)

    2014-01-01

    Citrus processing waste is a leftover from the citrus processing industry and is available in large amounts. Typically, this waste is dried to produce animal feed, but sometimes it is just dumped. Its main component is the peel, which consists mostly of pectin, with D-galacturonic acid as the main monomer. Aspergillus niger is a filamentous fungus that efficiently produces pectinases for the hydrolysis of pectin and uses the resulting D-galacturonic acid and most of the other components of citrus peel for growth. We used engineered A. niger strains that were not able to catabolise D-galacturonic acid, but instead converted it to L-galactonic acid. These strains also produced pectinases for the hydrolysis of pectin and were used for the conversion of pectin in orange peel to L-galactonic acid in a consolidated process. The D-galacturonic acid in the orange peel was converted to L-galactonic acid with a yield close to 90%. Submerged and solid-state fermentation processes were compared. PMID:24949267

  15. Caffeic acid production enhancement by engineering a phenylalanine over-producing Escherichia coli strain.

    Science.gov (United States)

    Huang, Qin; Lin, Yuheng; Yan, Yajun

    2013-12-01

    Caffeic acid is a plant-specific phenylpropanoic acid with multiple health-improving effects reported, and its therapeutic derivatives have also been studied throughout the last decade. To meet its market need and achieve high-level production, microbial production of caffeic acid approaches have been developed in metabolically engineered Escherichia coli. In our previous work, we have established the first artificial pathway that realized de novo production of caffeic acid using E. coli endogenous 4-hydroxyphenylacetate 3-hydroxylase (4HP3H). In this work, we exploited the catalytic potential of 4HPA3H in the whole-cell bioconversion study and produced 3.82 g/L (461.12 mg/L/OD) caffeic acid from p-coumaric acid, a direct precursor. We further engineered a phenylalanine over-producer into a tyrosine over-producer and then introduced the artificial pathway. After adjusting the expression strategy and optimizing the inoculants timing, de novo production of caffeic acid reached 766.68 mg/L. Both results from the direct precursor and simple carbon sources represent the highest titers of caffeic acid from microbial production so far.

  16. Manipulation of magnetic phase separation and orbital occupancy in manganites by strain engineering and electric field

    Science.gov (United States)

    Cui, Bin; Song, Cheng; Pan, Feng; Key Laboratory of Advanced Materials (MOE) Team

    2015-03-01

    The modification of electronic phases in correlated oxides is one of the core issues of condensed matter. We report the reversible control of ferromagnetic phase transition in manganite films by ionic liquid gating, replicating the La1-xSrxMnO3 (LSMO) phase diagram. The formation and annihilation of an insulating and magnetically hard phase in the soft magnetic matrix, which randomly nucleates and grows across the film, is directly observed under different gate voltages (VG) . The realization of reversible metal-insulator transition in colossal magnetoresistance materials can lead to the development of four-state memories. The orbital occupancy and magnetic anisotropy of LSMO films are manipulated by VG in a reversible and quantitative manner. Positive and negative VG increases and reduces the occupancy of the orbital and magnetic anisotropy that were initially favored by strain (irrespective of tensile and compressive), respectively. This finding fills in the blank of electrical manipulation of four degrees of freedom in correlated system.

  17. 酿酒酵母乙醇耐受性的研究进展%Advances in Research on Ethanol Tolerance of Saccharomyces cerevisiae

    Institute of Scientific and Technical Information of China (English)

    刘石雪; 王乔平; 唐丽薇; 严金平; 伊日布斯

    2013-01-01

    生物乙醇作为一种可再生的清洁能源,正在引起人们的广泛关注.酿酒酵母是乙醇生产中最常用的发酵菌株,但是乙醇耐受性往往成为限制酿酒酵母菌乙醇产量的重要因素.选育耐受高浓度乙醇的酵母菌株对于提高乙醇产率具有重要意义.然而传统的菌株改良方法具有育种周期长,突变方向不定等缺点.主要综述了近年来国内外对酿酒酵母菌耐受乙醇的分子生物学机理方面的研究成果,进而总结了提高酿酒酵母乙醇耐受性的基因工程、代谢工程.%Bioethanol as a renewable clean energy is causing widespread concern.Saccharomyces cerevisiae is the most commonly strains in the production of ethanol,but ethanol tolerance often become the most important factors that limit the Saccharomyces cerevisiae ethanol production.Improvement of ethanol tolerance of yeast cells is beneficial for ethanol production.However,traditional breeding methods have many shortcomings,such as long breeding cycle,variable mutation direction and so on.Recent research results about S.cerevisiae molecular mechanisms of tolerance to ethanol were reviewed,and the genetic engineering,metabolic engineering to improve S.cerevisiae ethanol tolerance was summarized.

  18. Organizational stress and individual strain: A social-psychological study of risk factors in coronary heart disease among administrators, engineers, and scientists

    Science.gov (United States)

    Caplan, R. D.

    1971-01-01

    It is hypothesized that organizational stresses, such as high quantitative work load, responsibility for persons, poor relations with role senders, and contact with alien organizational territories, may be associated with high levels of psychological and physiological strain which are risk factors in coronary heart disease. It is further hypothesized that persons with coronary-prone Type A personality characteristics are most likely to exhibit strain under conditions of organizational stress. Measures of these stresses, personality traits, and strains were obtained from 205 male NASA administrators, engineers, and scientists. Type A personality measures included sense of time urgency, persistence, involved striving, leadership, and preference for competitive and environmentally overburdening situations.

  19. Metabolic engineering and classic selection of the yeast Candida famata (Candida flareri) for construction of strains with enhanced riboflavin production.

    Science.gov (United States)

    Dmytruk, Kostyantyn V; Yatsyshyn, Valentyna Y; Sybirna, Natalia O; Fedorovych, Daria V; Sibirny, Andriy A

    2011-01-01

    Currently, the mutant of the flavinogenic yeast Candida famata dep8 isolated by classic mutagenesis and selection is used for industrial riboflavin production. Here we report on construction of a riboflavin overproducing strain of C. famata using a combination of random mutagenesis based on the selection of mutants resistant to different antimetabolites as well as rational approaches of metabolic engineering. The conventional mutagenesis involved consecutive selection for resistance to riboflavin structural analog 7-methyl-8-trifluoromethyl-10-(1'-d-ribityl)isoalloxazine), 8-azaguanine, 6-azauracil, 2-diazo-5-oxo-L-norleucine and guanosine as well as screening for yellow colonies at high pH. The metabolic engineering approaches involved introduction of additional copies of transcription factor SEF1 and IMH3 (coding for IMP dehydrogenase) orthologs from Debaryomyces hansenii, and the homologous genes RIB1 and RIB7, encoding GTP cyclohydrolase II and riboflavin synthetase, the first and the last enzymes of riboflavin biosynthesis pathway, respectively. Overexpression of the aforementioned genes in riboflavin overproducer AF-4 obtained by classical selection resulted in a 4.1-fold increase in riboflavin production in shake-flask experiments. D. hansenii IMH3 and modified ARO4 genes conferring resistance to mycophenolic acid and fluorophenylalanine, respectively, were successfully used as new dominant selection markers for C. famata. PMID:21040798

  20. Role of Nitrogen and Carbon Transport, Regulation, and Metabolism Genes for Saccharomyces cerevisiae Survival In Vivo†

    OpenAIRE

    Joanne M Kingsbury; Goldstein, Alan L.; McCusker, John H.

    2006-01-01

    Saccharomyces cerevisiae is both an emerging opportunistic pathogen and a close relative of pathogenic Candida species. To better understand the ecology of fungal infection, we investigated the importance of pathways involved in uptake, metabolism, and biosynthesis of nitrogen and carbon compounds for survival of a clinical S. cerevisiae strain in a murine host. Potential nitrogen sources in vivo include ammonium, urea, and amino acids, while potential carbon sources include glucose, lactate,...

  1. Biodiversity of a Natural Population of Saccharomyces cerevisiae and Hanseniaspora uvarum from Aglianico del Vulture

    OpenAIRE

    Paraggio, Margherita

    2004-01-01

    A total of 140 strains of Saccharomyces cerevisiae and Hanseniaspora uvarum, isolated from grapes and musts in the Basilicata region in Italy, were differentiated on the basis of fermentation behaviour and production of secondary compounds in Aglianico del Vulture must. A significant natural biodiversity of the strains was determined. In particular, within each species, the strains were differentiated for the fermentative activity and for the production of secondary compounds. Great strain va...

  2. Nanoscale Control of Phase Variants in Strain-Engineered BiFeO3

    Energy Technology Data Exchange (ETDEWEB)

    Vasudevan, Rama K [ORNL; Li, J. Y. [University of Washington, Seattle; Liu, Y. Y. [University of Washington, Seattle; Liang, W. -I. [National Chiao Tung University, Hsinchu, Taiwan; Kumar, Amit [ORNL; Jesse, Stephen [ORNL; Chen, Y. -C. [National Cheng Kung University, Tainan, Taiwan; Chu, Y.-H. [National Chiao Tung University, Hsinchu, Taiwan; Nagarajan, Valanoor [University of New South Wales; Kalinin, Sergei V [ORNL

    2011-01-01

    Development of magnetoelectric, electromechanical, and photovoltaic devices based on mixed-phase rhombohedral tetragonal (R-T) BiFeO3 (BFO) systems is possible only if the control of the engineered R phase variants is realized. Accordingly, we explore the mechanism of a bias induced phase transformation in this system. Single point spectroscopy demonstrates that the T->R transition is activated at lower voltages compared to T->T polarization switching. With phase field modeling, the transition is shown to be electrically driven. We further demonstrate that symmetry of formed R-phase rosettes can be broken by a proximal probe motion, allowing controlled creation of R variants with defined orientation. This approach opens a pathway to designing next-generation magnetoelectronic and data storage devices in the nanoscale.

  3. Sucrose and Saccharomyces cerevisiae: a relationship most sweet.

    Science.gov (United States)

    Marques, Wesley Leoricy; Raghavendran, Vijayendran; Stambuk, Boris Ugarte; Gombert, Andreas Karoly

    2016-02-01

    Sucrose is an abundant, readily available and inexpensive substrate for industrial biotechnology processes and its use is demonstrated with much success in the production of fuel ethanol in Brazil. Saccharomyces cerevisiae, which naturally evolved to efficiently consume sugars such as sucrose, is one of the most important cell factories due to its robustness, stress tolerance, genetic accessibility, simple nutrient requirements and long history as an industrial workhorse. This minireview is focused on sucrose metabolism in S. cerevisiae, a rather unexplored subject in the scientific literature. An analysis of sucrose availability in nature and yeast sugar metabolism was performed, in order to understand the molecular background that makes S. cerevisiae consume this sugar efficiently. A historical overview on the use of sucrose and S. cerevisiae by humans is also presented considering sugarcane and sugarbeet as the main sources of this carbohydrate. Physiological aspects of sucrose consumption are compared with those concerning other economically relevant sugars. Also, metabolic engineering efforts to alter sucrose catabolism are presented in a chronological manner. In spite of its extensive use in yeast-based industries, a lot of basic and applied research on sucrose metabolism is imperative, mainly in fields such as genetics, physiology and metabolic engineering.

  4. Mapping of Mechanical Strains and Stresses around Quiescent Engineered Three-Dimensional Epithelial Tissues

    Science.gov (United States)

    Gjorevski, Nikolce; Nelson, Celeste M.

    2012-01-01

    Understanding how physical signals guide biological processes requires qualitative and quantitative knowledge of the mechanical forces generated and sensed by cells in a physiologically realistic three-dimensional (3D) context. Here, we used computational modeling and engineered epithelial tissues of precise geometry to define the experimental parameters that are required to measure directly the mechanical stress profile of 3D tissues embedded within native type I collagen. We found that to calculate the stresses accurately in these settings, we had to account for mechanical heterogeneities within the matrix, which we visualized and quantified using confocal reflectance and atomic force microscopy. Using this technique, we were able to obtain traction forces at the epithelium-matrix interface, and to resolve and quantify patterns of mechanical stress throughout the surrounding matrix. We discovered that whereas single cells generate tension by contracting and pulling on the matrix, the contraction of multicellular tissues can also push against the matrix, causing emergent compression. Furthermore, tissue geometry defines the spatial distribution of mechanical stress across the epithelium, which communicates mechanically over distances spanning hundreds of micrometers. Spatially resolved mechanical maps can provide insight into the types and magnitudes of physical parameters that are sensed and interpreted by multicellular tissues during normal and pathological processes. PMID:22828342

  5. Theoretical and experimental stress-strain analysis of machining gas turbine engine parts, which made of the high energy structural efficiency alloys

    Directory of Open Access Journals (Sweden)

    V. V. Postnov,

    2014-07-01

    Full Text Available Methods to improve accuracy of the gas turbine engine (GTE blades machining by analyzing the stress-strain state were reviewed. The new method to compensate for machining error was proposed. The model of parameters that affect cutting mode and the radial component of cutting force during milling was developed.

  6. Improved production of medium-chain-length Polyhydroxyalkanotes in glucose-based fed-batch cultivations of metabolically engineered Pseudomonas putida strains

    NARCIS (Netherlands)

    Poblete-Castro, I.; Rodriguez, A.L.; Lam, M.C.; Kessler, W.

    2014-01-01

    One of the major challenges in metabolic engineering for enhanced synthesis of value-added chemicals is to design and develop new strains which can be translated into well-controlled fermentation processes using bioreactors. The aim of this study was to assess the influence of various fed-batch stra

  7. Fungal genomics beyond Saccharomyces cerevisiae?

    DEFF Research Database (Denmark)

    Hofmann, Gerald; Mcintyre, Mhairi; Nielsen, Jens

    2003-01-01

    Fungi are used extensively in both fundamental research and industrial applications. Saccharomyces cerevisiae has been the model organism for fungal research for many years, particularly in functional genomics. However, considering the diversity within the fungal kingdom, it is obvious that the a......Fungi are used extensively in both fundamental research and industrial applications. Saccharomyces cerevisiae has been the model organism for fungal research for many years, particularly in functional genomics. However, considering the diversity within the fungal kingdom, it is obvious...

  8. EasyClone-MarkerFree: A vector toolkit for marker-less integration of genes into Saccharomyces cerevisiae via CRISPR-Cas9.

    Science.gov (United States)

    Jessop-Fabre, Mathew M; Jakočiūnas, Tadas; Stovicek, Vratislav; Dai, Zongjie; Jensen, Michael K; Keasling, Jay D; Borodina, Irina

    2016-08-01

    Saccharomyces cerevisiae is an established industrial host for production of recombinant proteins, fuels and chemicals. To enable stable integration of multiple marker-free overexpression cassettes in the genome of S. cerevisiae, we have developed a vector toolkit EasyClone-MarkerFree. The integration of linearized expression cassettes into defined genomic loci is facilitated by CRISPR/Cas9. Cas9 is recruited to the chromosomal location by specific guide RNAs (gRNAs) expressed from a set of gRNA helper vectors. Using our genome engineering vector suite, single and triple insertions are obtained with 90-100% and 60-70% targeting efficiency, respectively. We demonstrate application of the vector toolkit by constructing a haploid laboratory strain (CEN.PK113-7D) and a diploid industrial strain (Ethanol Red) for production of 3-hydroxypropionic acid, where we tested three different acetyl-CoA supply strategies, requiring overexpression of three to six genes each. Among the tested strategies was a bacterial cytosolic pyruvate dehydrogenase complex, which was integrated into the genome in a single transformation. The publicly available EasyClone-MarkerFree vector suite allows for facile and highly standardized genome engineering, and should be of particular interest to researchers working on yeast chassis with limited markers available. PMID:27166612

  9. Alternative reactions at the interface of glycolysis and citric acid cycle in Saccharomyces cerevisiae.

    Science.gov (United States)

    van Rossum, Harmen M; Kozak, Barbara U; Niemeijer, Matthijs S; Duine, Hendrik J; Luttik, Marijke A H; Boer, Viktor M; Kötter, Peter; Daran, Jean-Marc G; van Maris, Antonius J A; Pronk, Jack T

    2016-05-01

    Pyruvate and acetyl-coenzyme A, located at the interface between glycolysis and TCA cycle, are important intermediates in yeast metabolism and key precursors for industrially relevant products. Rational engineering of their supply requires knowledge of compensatory reactions that replace predominant pathways when these are inactivated. This study investigates effects of individual and combined mutations that inactivate the mitochondrial pyruvate-dehydrogenase (PDH) complex, extramitochondrial citrate synthase (Cit2) and mitochondrial CoA-transferase (Ach1) in Saccharomyces cerevisiae. Additionally, strains with a constitutively expressed carnitine shuttle were constructed and analyzed. A predominant role of the PDH complex in linking glycolysis and TCA cycle in glucose-grown batch cultures could be functionally replaced by the combined activity of the cytosolic PDH bypass and Cit2. Strongly impaired growth and a high incidence of respiratory deficiency in pda1Δ ach1Δ strains showed that synthesis of intramitochondrial acetyl-CoA as a metabolic precursor requires activity of either the PDH complex or Ach1. Constitutive overexpression of AGP2, HNM1, YAT2, YAT1, CRC1 and CAT2 enabled the carnitine shuttle to efficiently link glycolysis and TCA cycle in l-carnitine-supplemented, glucose-grown batch cultures. Strains in which all known reactions at the glycolysis-TCA cycle interface were inactivated still grew slowly on glucose, indicating additional flexibility at this key metabolic junction.

  10. Shuttle mutagenesis: a method of transposon mutagenesis for Saccharomyces cerevisiae.

    OpenAIRE

    Seifert, H S; Chen, E Y; So, M; Heffron, F

    1986-01-01

    We have extended the method of transposon mutagenesis to the eukaryote, Saccharomyces cerevisiae. A bacterial transposon containing a selectable yeast gene can be transposed into a cloned fragment of yeast DNA in Escherichia coli, and the transposon insertion can be returned to the yeast genome by homologous recombination. Initially, the cloned yeast DNA fragment to be mutagenized was transformed into an E. coli strain containing an F factor derivative carrying the transposable element. The c...

  11. Phenotypic landscape of Saccharomyces cerevisiae during wine fermentation: evidence for origin-dependent metabolic traits.

    Directory of Open Access Journals (Sweden)

    Carole Camarasa

    Full Text Available The species Saccharomyces cerevisiae includes natural strains, clinical isolates, and a large number of strains used in human activities. The aim of this work was to investigate how the adaptation to a broad range of ecological niches may have selectively shaped the yeast metabolic network to generate specific phenotypes. Using 72 S. cerevisiae strains collected from various sources, we provide, for the first time, a population-scale picture of the fermentative metabolic traits found in the S. cerevisiae species under wine making conditions. Considerable phenotypic variation was found suggesting that this yeast employs diverse metabolic strategies to face environmental constraints. Several groups of strains can be distinguished from the entire population on the basis of specific traits. Strains accustomed to growing in the presence of high sugar concentrations, such as wine yeasts and strains obtained from fruits, were able to achieve fermentation, whereas natural yeasts isolated from "poor-sugar" environments, such as oak trees or plants, were not. Commercial wine yeasts clearly appeared as a subset of vineyard isolates, and were mainly differentiated by their fermentative performances as well as their low acetate production. Overall, the emergence of the origin-dependent properties of the strains provides evidence for a phenotypic evolution driven by environmental constraints and/or human selection within S. cerevisiae.

  12. Strain engineering to control the magnetic and magnetotransport properties of La0.67Sr0.33MnO3 thin films

    Energy Technology Data Exchange (ETDEWEB)

    Yang, F.; Kemik, N.; Biegalski, M.D.; Christen, H.M.; Arenholz, E.; Takamura, Y.

    2010-06-15

    This work studies the control of the magnetic and magnetotransport properties of La{sub 0.67}Sr{sub 0.33}MnO{sub 3} thin films through strain engineering. The strain state is characterized by the tetragonal distortion (c/a ratio), which can be varied continuously between a compressive strain of 1.005 to a tensile strain of 0.952 by changing the type of substrate, the growth rate, and the presence of an underlying La{sub 0.67}Sr{sub 0.33}FeO{sub 3} buffer layer. Increasing tensile tetragonal distortion of the La{sub 0.67}Sr{sub 0.33}MnO{sub 3} thin film decreases the saturation magnetization, changes the temperature dependence of the resistivity and magnetoresistance, and increases the resistivity by several orders of magnitude.

  13. Enhanced arsenic accumulation in Saccharomyces cerevisiae overexpressing transporters Fps1p or Hxt7p.

    Science.gov (United States)

    Shah, Dhawal; Shen, Michael W Y; Chen, Wilfred; Da Silva, Nancy A

    2010-10-01

    Arsenic contamination of ground water affects the health of millions of people worldwide. Bioremediation has the potential to lower contaminant levels in cases where physical methods are either ineffective or cost prohibitive. The yeast Saccharomyces cerevisiae was engineered for enhanced arsenite accumulation by overexpression of transporters responsible for the influx of the contaminant. The transporter genes FPS1 and HXT7 were cloned under the control of the late-phase ADH2-promoter. This allowed for protein production at high biomass levels without the addition of inducer. Following the transfer of stationary phase cells to buffer, the engineered strains were capable of 3-4-fold greater arsenic uptake as compared to control cells. Further, at trace levels of the metalloid, the cells overexpressing the Fps1p transporter removed ca. 40% more arsenite from the extracellular medium than the controls. Arsenic uptake was also evaluated in cells overexpressing the transporters coupled with high-level production of cytosolic As sequestors (phytochelatins or bacterial ArsRp) to act as an intracellular sink. This led to an up to 4-fold increase in As accumulation in the resting cell culture as compared to native cells. The results demonstrate important steps needed to engineer a yeast biosorbent with enhanced accumulation capabilities for this metalloid.

  14. Engineering the polar magneto-optical Kerr effect in strongly strained L10-MnAl films

    Science.gov (United States)

    Zhu, Lijun; Brandt, Liane; Zhao, Jianhua

    2016-10-01

    We report the engineering of the polar magnetooptical (MO) Kerr effect in perpendicularly magnetized L10-MnAl epitaxial films with remarkably tuned magnetization, strain, and structural disorder by varying substrate temperature (T s) during molecular-beam epitaxy growth. The Kerr rotation was enhanced by a factor of up to 5 with T s increasing from 150 to 350 °C as a direct consequence of the improvement of the magnetization. A similar remarkable tuning effect was also observed on the Kerr ellipticity and the magnitude of the complex Kerr angle, while the phase of the complex Kerr angle appears to be independent of the magnetization. The combination of the good semiconductor compatibility, the moderate coercivity of 0.3-8.2 kOe, the tunable polar MO Kerr effect of up to ~0.034°, and giant spin precession frequencies of up to ~180 GHz makes L10-MnAl films a very interesting MO material. Our results give insights into both the microscopic mechanisms of the MO Kerr effect in L10-MnAl alloys and their scientific and technological application potential in the emerging spintronics and ultrafast MO modulators.

  15. Reversible and Nonvolatile Modulations of Magnetization Switching Characteristic and Domain Configuration in L10-FePt Films via Nonelectrically Controlled Strain Engineering.

    Science.gov (United States)

    Feng, Chun; Zhao, Jiancheng; Yang, Feng; Hao, Shijie; Gong, Kui; Hu, Di; Cao, Yi; Jiang, Xumin; Wang, Zhongqiang; Chen, Lei; Li, Sirui; Sun, Li; Cui, Lishan; Yu, Guanghua

    2016-03-23

    Reversible and nonvolatile modulation of magnetization switching characteristic in ferromagnetic materials is crucial in developing spintronic devices with low power consumption. It is recently discovered that strain engineering can be an active and effective approach in tuning the magnetic/transport properties of thin films. The primary method in strain modulation is via the converse piezoelectric effect of ferroelectrics, which is usually volatile due to the reliance of the required electric field. Also the maximum amount of deformation in ferroelectrics is usually limited to be less than 1%, and the corresponding magnetoelastic strain energy introduced to ferromagnetic films is on the order of 10(4) J/m(3), not enough to overcome magnetocrystalline anisotropy energy (Ku) in many materials. Different from using conventional strain inducing substrates, this paper reports on the significantly large, reversible, and nonvolatile lattice strain in the L10-FePt films (up to 2.18%) using nonelectrically controlled shape memory alloy substrates. Introduced lattice strain can be large enough to effectively affect domain structure and magnetic reversal in FePt. A noticeable decrease of coercivity field by 80% is observed. Moreover, the coercivity field tunability using such substrates is nonvolatile at room temperature and is also reversible due to the characteristics of the shape memory effect. This finding provides an efficient avenue for developing strain assisted spintronic devices such as logic memory device, magnetoresistive random-access memory, and memristor. PMID:26939773

  16. An improved method of xylose utilization by recombinant Saccharomyces cerevisiae.

    Science.gov (United States)

    Ma, Tien-Yang; Lin, Ting-Hsiang; Hsu, Teng-Chieh; Huang, Chiung-Fang; Guo, Gia-Luen; Hwang, Wen-Song

    2012-10-01

    The aim of this study was to develop a method to optimize expression levels of xylose-metabolizing enzymes to improve xylose utilization capacity of Saccharomyces cerevisiae. A xylose-utilizing recombinant S. cerevisiae strain YY2KL, able to express nicotinamide adenine dinucleotide phosphate, reduced (NADPH)-dependent xylose reductase (XR), nicotinamide adenine dinucleotide (NAD(+))-dependent xylitol dehydrogenase (XDH), and xylulokinase (XK), showed a low ethanol yield and sugar consumption rate. To optimize xylose utilization by YY2KL, a recombinant expression plasmid containing the XR gene was transformed and integrated into the aur1 site of YY2KL. Two recombinant expression plasmids containing an nicotinamide adenine dinucleotide phosphate (NADP(+))-dependent XDH mutant and XK genes were dually transformed and integrated into the 5S ribosomal DNA (rDNA) sites of YY2KL. This procedure allowed systematic construction of an S. cerevisiae library with different ratios of genes for xylose-metabolizing enzymes, and well-grown colonies with different xylose fermentation capacities could be further selected in yeast protein extract (YPX) medium (1 % yeast extract, 2 % peptone, and 2 % xylose). We successfully isolated a recombinant strain with a superior xylose fermentation capacity and designated it as strain YY5A. The xylose consumption rate for strain YY5A was estimated to be 2.32 g/gDCW/h (g xylose/g dry cell weight/h), which was 2.34 times higher than that for the parent strain YY2KL (0.99 g/gDCW/h). The ethanol yield was also enhanced 1.83 times by this novel method. Optimal ratio and expression levels of xylose-metabolizing enzymes are important for efficient conversion of xylose to ethanol. This study provides a novel method that allows rapid and effective selection of ratio-optimized xylose-utilizing yeast strains. This method may be applicable to other multienzyme systems in yeast.

  17. The study of the influence of temperature and initial glucose concentration on the fermentation process in the presence of Saccharomyces cerevisiae yeast strain immobilized on starch gels by reversed-flow gas chromatography.

    Science.gov (United States)

    Lainioti, G Ch; Kapolos, J; Koliadima, A; Karaiskakis, G

    2012-01-01

    The technique of reversed-flow gas chromatography (RFGC) was employed for the determination of the alcoholic fermentation phases and of kinetic parameters for free and immobilized cell systems, at different initial glucose concentrations and temperature values. In addition to this, due to its considerable advantages over other techniques, RFGC was used for the characterization of a new biocatalyst, yeast cells immobilized on starch gel, and especially wheat starch gel. Immobilization of wine yeast Saccharomyces cerevisiae AXAZ-1 was accomplished on wheat and corn starch gels in order to prepare new biocatalysts with great interest for the fermentation industry. The RFGC led with great accuracy, resulting from a literature review, to the determination of reaction rate constants and activation energies at each phase of the fermentation processes. A maximum value of rate constants was observed at initial glucose concentration of 205 g/L, where a higher number of yeast cells was observed. The increase of glucose concentrations had a negative influence on the growth of AXAZ-1 cells and rate constants were decreased. The decrease of fermentation temperature caused a substantial reduction in the viability of immobilized cells as well as in rate constant values. Activation energies of corn starch gel presented lower values than those of wheat starch gel. However, the two supports showed higher catalytic efficiency than free cell systems, proving that starch gels may act as a promoter of the catalytic activity of the yeast cells involved in the fermentation process.

  18. Evaluation of stress tolerance and fermentative behavior of indigenous Saccharomyces cerevisiae

    OpenAIRE

    Cíntia Lacerda Ramos; Whasley Ferreira Duarte; Ana Luiza Freire; Disney Ribeiro Dias; Elis Cristina Araújo Eleutherio; Rosane Freitas Schwan

    2013-01-01

    Sixty six indigenous Saccharomyces cerevisiae strains were evaluated in stressful conditions (temperature, osmolarity, sulphite and ethanol tolerance) and also ability to flocculate. Eighteen strains showed tolerant characteristics to these stressful conditions, growing at 42 °C, in 0.04% sulphite, 1 mol L−1 NaCl and 12% ethanol. No flocculent characteristics were observed. These strains were evaluated according to their fermentative performance in sugar cane juice. The conversion factors of ...

  19. The role of cytoplasmic catalase in dehydration tolerance of Saccharomyces cerevisiae

    OpenAIRE

    França, Mauro Braga; Panek, Anita Dolly; Eleutherio, Elis Cristina Araujo

    2005-01-01

    In this study, we investigated the role played by cytoplasmic catalase (Ctt1) in resistance against water loss using the yeast Saccharomyces cerevisiae as eukaryotic cell model. Comparing a mutant possessing a specific lesion in CTT1 with its parental strain, it was observed that both control and ctt1 strains exhibited increased levels of lipid peroxidation after dehydration, suggesting that catalase does not protect membranes during drying. Although the ctt1 strain has only 1 catalase isofor...

  20. Mixing of vineyard and oak-tree ecotypes of Saccharomyces cerevisiae in North American vineyards.

    Science.gov (United States)

    Hyma, Katie E; Fay, Justin C

    2013-06-01

    Humans have had a significant impact on the distribution and abundance of Saccharomyces cerevisiae through its widespread use in beer, bread and wine production. Yet, similar to other Saccharomyces species, S. cerevisiae has also been isolated from habitats unrelated to fermentations. Strains of S. cerevisiae isolated from grapes, wine must and vineyards worldwide are genetically differentiated from strains isolated from oak-tree bark, exudate and associated soil in North America. However, the causes and consequences of this differentiation have not yet been resolved. Historical differentiation of these two groups may have been influenced by geographic, ecological or human-associated barriers to gene flow. Here, we make use of the relatively recent establishment of vineyards across North America to identify and characterize any active barriers to gene flow between these two groups. We examined S. cerevisiae strains isolated from grapes and oak trees within three North American vineyards and compared them to those isolated from oak trees outside of vineyards. Within vineyards, we found evidence of migration between grapes and oak trees and potential gene flow between the divergent oak-tree and vineyard groups. Yet, we found no vineyard genotypes on oak trees outside of vineyards. In contrast, Saccharomyces paradoxus isolated from the same sources showed population structure characterized by isolation by distance. The apparent absence of ecological or genetic barriers between sympatric vineyard and oak-tree populations of S. cerevisiae implies that vineyards play an important role in the mixing between these two groups.