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Sample records for diffusion-controlled enzymatic reactions

  1. Diffusion-controlled reactions modeling in Geant4-DNA

    Energy Technology Data Exchange (ETDEWEB)

    Karamitros, M., E-mail: matkara@gmail.com [CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan (France); CNRS, INCIA, UMR 5287, F-33400 Talence (France); Luan, S. [University of New Mexico, Department of Computer Science, Albuquerque, NM (United States); Bernal, M.A. [Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, SP (Brazil); Allison, J. [Geant4 Associates International Ltd (United Kingdom); Baldacchino, G. [CEA Saclay, IRAMIS, LIDYL, Radiation Physical Chemistry Group, F-91191 Gif sur Yvette Cedex (France); CNRS, UMR3299, SIS2M, F-91191 Gif sur Yvette Cedex (France); Davidkova, M. [Nuclear Physics Institute of the ASCR, Prague (Czech Republic); Francis, Z. [Saint Joseph University, Faculty of Sciences, Department of Physics, Mkalles, Beirut (Lebanon); Friedland, W. [Helmholtz Zentrum München, German Research Center for Environmental Health, Institute of Radiation Protection, Ingolstädter Landstr. 1, 85764 Neuherberg (Germany); Ivantchenko, V. [Ecoanalytica, 119899 Moscow (Russian Federation); Geant4 Associates International Ltd (United Kingdom); Ivantchenko, A. [Geant4 Associates International Ltd (United Kingdom); Mantero, A. [SwHaRD s.r.l., via Buccari 9, 16153 Genova (Italy); Nieminem, P.; Santin, G. [ESA-ESTEC, 2200 AG Noordwijk (Netherlands); Tran, H.N. [Division of Nuclear Physics and Faculty of Applied Sciences, Ton Duc Thang University, Tan Phong Ward, District 7, Ho Chi Minh City (Viet Nam); Stepan, V. [CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan (France); Nuclear Physics Institute of the ASCR, Prague (Czech Republic); Incerti, S., E-mail: incerti@cenbg.in2p3.fr [CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan (France)

    2014-10-01

    Context Under irradiation, a biological system undergoes a cascade of chemical reactions that can lead to an alteration of its normal operation. There are different types of radiation and many competing reactions. As a result the kinetics of chemical species is extremely complex. The simulation becomes then a powerful tool which, by describing the basic principles of chemical reactions, can reveal the dynamics of the macroscopic system. To understand the dynamics of biological systems under radiation, since the 80s there have been on-going efforts carried out by several research groups to establish a mechanistic model that consists in describing all the physical, chemical and biological phenomena following the irradiation of single cells. This approach is generally divided into a succession of stages that follow each other in time: (1) the physical stage, where the ionizing particles interact directly with the biological material; (2) the physico-chemical stage, where the targeted molecules release their energy by dissociating, creating new chemical species; (3) the chemical stage, where the new chemical species interact with each other or with the biomolecules; (4) the biological stage, where the repairing mechanisms of the cell come into play. This article focuses on the modeling of the chemical stage. Method This article presents a general method of speeding-up chemical reaction simulations in fluids based on the Smoluchowski equation and Monte-Carlo methods, where all molecules are explicitly simulated and the solvent is treated as a continuum. The model describes diffusion-controlled reactions. This method has been implemented in Geant4-DNA. The keys to the new algorithm include: (1) the combination of a method to compute time steps dynamically with a Brownian bridge process to account for chemical reactions, which avoids costly fixed time step simulations; (2) a k–d tree data structure for quickly locating, for a given molecule, its closest reactants. The

  2. Kinetics of diffusion-controlled and ballistically-controlled reactions

    International Nuclear Information System (INIS)

    Redner, S.

    1995-01-01

    The kinetics of diffusion-controlled two-species annihilation, A+B → O and single-species ballistically-controlled annihilation, A+A → O are investigated. For two-species annihilation, we describe the basic mechanism that leads to the formation of a coarsening mosaic of A- and B-domains. The implications of this picture on the distribution of reactants is discussed. For ballistic annihilation, dimensional analysis shows that the concentration and rms velocity decay as c∼t -α and v∼t -β , respectively, with α+β = 1 in any spatial dimension. Analysis of the Boltzmann equation for the evolution of the velocity distribution yields accurate predictions for the kinetics. New phenomena associated with discrete initial velocity distributions and with mixed ballistic and diffusive reactant motion are also discussed. (author)

  3. Internal Diffusion-Controlled Enzyme Reaction: The Acetylcholinesterase Kinetics.

    Science.gov (United States)

    Lee, Sangyun; Kim, Ji-Hyun; Lee, Sangyoub

    2012-02-14

    Acetylcholinesterase is an enzyme with a very high turnover rate; it quenches the neurotransmitter, acetylcholine, at the synapse. We have investigated the kinetics of the enzyme reaction by calculating the diffusion rate of the substrate molecule along an active site channel inside the enzyme from atomic-level molecular dynamics simulations. In contrast to the previous works, we have found that the internal substrate diffusion is the determinant of the acetylcholinesterase kinetics in the low substrate concentration limit. Our estimate of the overall bimolecular reaction rate constant for the enzyme is in good agreement with the experimental data. In addition, the present calculation provides a reasonable explanation for the effects of the ionic strength of solution and the mutation of surface residues of the enzyme. The study suggests that internal diffusion of the substrate could be a key factor in understanding the kinetics of enzymes of similar characteristics.

  4. Reaction-diffusion controlled growth of complex structures

    Science.gov (United States)

    Noorduin, Willem; Mahadevan, L.; Aizenberg, Joanna

    2013-03-01

    Understanding how the emergence of complex forms and shapes in biominerals came about is both of fundamental and practical interest. Although biomineralization processes and organization strategies to give higher order architectures have been studied extensively, synthetic approaches to mimic these self-assembled structures are highly complex and have been difficult to emulate, let alone replicate. The emergence of solution patterns has been found in reaction-diffusion systems such as Turing patterns and the BZ reaction. Intrigued by this spontaneous formation of complexity we explored if similar processes can lead to patterns in the solid state. We here identify a reaction-diffusion system in which the shape of the solidified products is a direct readout of the environmental conditions. Based on insights in the underlying mechanism, we developed a toolbox of engineering strategies to deterministically sculpt patterns and shapes, and combine different morphologies to create a landscape of hierarchical multi scale-complex tectonic architectures with unprecedented levels of complexity. These findings may hold profound implications for understanding, mimicking and ultimately expanding upon nature's morphogenesis strategies, allowing the synthesis of advanced highly complex microscale materials and devices. WLN acknowledges the Netherlands Organization for Scientific Research for financial support

  5. A Networks Approach to Modeling Enzymatic Reactions.

    Science.gov (United States)

    Imhof, P

    2016-01-01

    Modeling enzymatic reactions is a demanding task due to the complexity of the system, the many degrees of freedom involved and the complex, chemical, and conformational transitions associated with the reaction. Consequently, enzymatic reactions are not determined by precisely one reaction pathway. Hence, it is beneficial to obtain a comprehensive picture of possible reaction paths and competing mechanisms. By combining individually generated intermediate states and chemical transition steps a network of such pathways can be constructed. Transition networks are a discretized representation of a potential energy landscape consisting of a multitude of reaction pathways connecting the end states of the reaction. The graph structure of the network allows an easy identification of the energetically most favorable pathways as well as a number of alternative routes. © 2016 Elsevier Inc. All rights reserved.

  6. Diffusion-controlled reaction. V. Effect of concentration-dependent diffusion coefficient on reaction rate in graft polymerization

    International Nuclear Information System (INIS)

    Imre, K.; Odian, G.

    1979-01-01

    The effect of diffusion on radiation-initiated graft polymerization has been studied with emphasis on the single- and two-penetrant cases. When the physical properties of the penetrants are similar, the two-penetrant problems can be reduced to the single-penetrant problem by redefining the characteristic parameters of the system. The diffusion-free graft polymerization rate is assumed to be proportional to the upsilon power of the monomer concentration respectively, and, in which the proportionality constant a = k/sub p/R/sub i//sup w//k/sub t//sup z/, where k/sub p/ and k/sub t/ are the propagation and termination rate constants, respectively, and R/sub i/ is the initiation rate. The values of upsilon, w, and z depend on the particular reaction system. The results of earlier work were generalized by allowing a non-Fickian diffusion rate which predicts an essentially exponential dependence on the monomer concentration of the diffusion coefficient, D = D 0 [exp(deltaC/M)], where M is the saturation concentration. A reaction system is characterized by the three dimensionless parameters, upsilon, delta, and A = (L/2)[aM/sup (upsilon--1)//D 0 ]/sup 1/2/, where L is the polymer film thickness. Graft polymerization tends to become diffusion controlled as A increases. Larger values of delta and ν cause a reaction system to behave closer to the diffusion-free regime. Transition from diffusion-free to diffusion-controlled reaction involves changes in the dependence of the reaction rate on film thickness, initiation rate, and monomer concentration. Although the diffusion-free rate is w order in initiation rate, upsilon order in monomer, and independent of film thickness, the diffusion-controlled rate is w/2 order in initiator rate and inverse first-order in film thickness. Dependence of the diffusion-controlled rate on monomer is dependent in a complex manner on the diffusional characteristics of the reaction system. 11 figures, 4 tables

  7. Multi-scale modeling of diffusion-controlled reactions in polymers: renormalisation of reactivity parameters.

    Science.gov (United States)

    Everaers, Ralf; Rosa, Angelo

    2012-01-07

    The quantitative description of polymeric systems requires hierarchical modeling schemes, which bridge the gap between the atomic scale, relevant to chemical or biomolecular reactions, and the macromolecular scale, where the longest relaxation modes occur. Here, we use the formalism for diffusion-controlled reactions in polymers developed by Wilemski, Fixman, and Doi to discuss the renormalisation of the reactivity parameters in polymer models with varying spatial resolution. In particular, we show that the adjustments are independent of chain length. As a consequence, it is possible to match reactions times between descriptions with different resolution for relatively short reference chains and to use the coarse-grained model to make quantitative predictions for longer chains. We illustrate our results by a detailed discussion of the classical problem of chain cyclization in the Rouse model, which offers the simplest example of a multi-scale descriptions, if we consider differently discretized Rouse models for the same physical system. Moreover, we are able to explore different combinations of compact and non-compact diffusion in the local and large-scale dynamics by varying the embedding dimension.

  8. Cascade enzymatic reactions for efficient carbon sequestration.

    Science.gov (United States)

    Xia, Shunxiang; Zhao, Xueyan; Frigo-Vaz, Benjamin; Zheng, Wenyun; Kim, Jungbae; Wang, Ping

    2015-04-01

    Thermochemical processes developed for carbon capture and storage (CCS) offer high carbon capture capacities, but are generally hampered by low energy efficiency. Reversible cascade enzyme reactions are examined in this work for energy-efficient carbon sequestration. By integrating the reactions of two key enzymes of RTCA cycle, isocitrate dehydrogenase and aconitase, we demonstrate that intensified carbon capture can be realized through such cascade enzymatic reactions. Experiments show that enhanced thermodynamic driving force for carbon conversion can be attained via pH control under ambient conditions, and that the cascade reactions have the potential to capture 0.5 mol carbon at pH 6 for each mole of substrate applied. Overall it manifests that the carbon capture capacity of biocatalytic reactions, in addition to be energy efficient, can also be ultimately intensified to approach those realized with chemical absorbents such as MEA. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Isothermal calorimetry of enzymatic biodiesel reaction

    DEFF Research Database (Denmark)

    Fjerbæk Søtoft, Lene; Westh, Peter; Christensen, Knud Villy

    2010-01-01

      Isothermal calorimetry ITC has been used to investigate enzymatic biodiesel production. The transesterification of rapeseed oil with methanol and ethanol was catalyzed by the immobilized lipase Novozym 435 at 40°C. The ITC-experiments clearly demonstrate the possibilities of investigating complex...... and composition change in the system, the heat of reaction at 40°C for the two systems has been determined to -9.8 ± 0.9 kJ/mole biodiesel formed from rapeseed oil and methanol, and - 9.3 ± 0.7 kJ/mole when rapeseed oil and ethanol is used....

  10. Modeling the Influence of Diffusion-Controlled Reactions and Residual Termination and Deactivation on the Rate and Control of Bulk ATRP at High Conversions

    Directory of Open Access Journals (Sweden)

    Ali Mohammad Rabea

    2015-04-01

    Full Text Available In high-conversion atom transfer radical polymerization (ATRP, all the reactions, such as radical termination, radical deactivation, dormant chain activation, monomer propagation, etc. could become diffusion controlled sooner or later, depending on relative diffusivities of the involved reacting species. These diffusion-controlled reactions directly affect the rate of polymerization and the control of polymer molecular weight. A model is developed to investigate the influence of diffusion-controlled reactions on the high conversion ATRP kinetics. Model simulation reveals that diffusion-controlled termination slightly increases the rate, but it is the diffusion-controlled deactivation that causes auto-acceleration in the rate (“gel effect” and loss of control. At high conversions, radical chains are “trapped” because of high molecular weight. However, radical centers can still migrate through (1 radical deactivation–activation cycles and (2 monomer propagation, which introduce “residual termination” reactions. It is found that the “residual termination” does not have much influence on the polymerization kinetics. The migration of radical centers through propagation can however facilitate catalytic deactivation of radicals, which improves the control of polymer molecular weight to some extent. Dormant chain activation and monomer propagation also become diffusion controlled and finally stop the polymerization when the system approaches its glass state.

  11. Thermally activated reaction–diffusion-controlled chemical bulk reactions of gases and solids

    Directory of Open Access Journals (Sweden)

    S. Möller

    2015-01-01

    Full Text Available The chemical kinetics of the reaction of thin films with reactive gases is investigated. The removal of thin films using thermally activated solid–gas to gas reactions is a method to in-situ control deposition inventory in vacuum and plasma vessels. Significant scatter of experimental deposit removal rates at apparently similar conditions was observed in the past, highlighting the need for understanding the underlying processes. A model based on the presence of reactive gas in the films bulk and chemical kinetics is presented. The model describes the diffusion of reactive gas into the film and its chemical interaction with film constituents in the bulk using a stationary reaction–diffusion equation. This yields the reactive gas concentration and reaction rates. Diffusion and reaction rate limitations are depicted in parameter studies. Comparison with literature data on tokamak co-deposit removal results in good agreement of removal rates as a function of pressure, film thickness and temperature.

  12. On the Green's function of the partially diffusion-controlled reversible ABCD reaction for radiation chemistry codes

    International Nuclear Information System (INIS)

    Plante, Ianik; Devroye, Luc

    2015-01-01

    Several computer codes simulating chemical reactions in particles systems are based on the Green's functions of the diffusion equation (GFDE). Indeed, many types of chemical systems have been simulated using the exact GFDE, which has also become the gold standard for validating other theoretical models. In this work, a simulation algorithm is presented to sample the interparticle distance for partially diffusion-controlled reversible ABCD reaction. This algorithm is considered exact for 2-particles systems, is faster than conventional look-up tables and uses only a few kilobytes of memory. The simulation results obtained with this method are compared with those obtained with the independent reaction times (IRT) method. This work is part of our effort in developing models to understand the role of chemical reactions in the radiation effects on cells and tissues and may eventually be included in event-based models of space radiation risks. However, as many reactions are of this type in biological systems, this algorithm might play a pivotal role in future simulation programs not only in radiation chemistry, but also in the simulation of biochemical networks in time and space as well

  13. On the Green's function of the partially diffusion-controlled reversible ABCD reaction for radiation chemistry codes

    Energy Technology Data Exchange (ETDEWEB)

    Plante, Ianik, E-mail: ianik.plante-1@nasa.gov [Wyle Science, Technology & Engineering, 1290 Hercules, Houston, TX 77058 (United States); Devroye, Luc, E-mail: lucdevroye@gmail.com [School of Computer Science, McGill University, 3480 University Street, Montreal H3A 0E9 (Canada)

    2015-09-15

    Several computer codes simulating chemical reactions in particles systems are based on the Green's functions of the diffusion equation (GFDE). Indeed, many types of chemical systems have been simulated using the exact GFDE, which has also become the gold standard for validating other theoretical models. In this work, a simulation algorithm is presented to sample the interparticle distance for partially diffusion-controlled reversible ABCD reaction. This algorithm is considered exact for 2-particles systems, is faster than conventional look-up tables and uses only a few kilobytes of memory. The simulation results obtained with this method are compared with those obtained with the independent reaction times (IRT) method. This work is part of our effort in developing models to understand the role of chemical reactions in the radiation effects on cells and tissues and may eventually be included in event-based models of space radiation risks. However, as many reactions are of this type in biological systems, this algorithm might play a pivotal role in future simulation programs not only in radiation chemistry, but also in the simulation of biochemical networks in time and space as well.

  14. Biosensing strategies based on enzymatic reactions and nanoparticles.

    Science.gov (United States)

    Díez-Buitrago, Beatriz; Briz, Nerea; Liz-Marzán, Luis M; Pavlov, Valeri

    2018-04-16

    Enzymes are pivotal elements in bioanalysis due to their specificity and extremely high catalytic activity. The sensitivity of bioanalytical assays depends mainly on the capacity of an observer to detect the product(s) of a biocatalytic reaction. Both natural and artificial compounds have been traditionally used to evaluate enzymatic activities. The drawbacks of chromogenic and fluorogenic organic enzymatic substrates are their high cost and low stability, resulting in high background signals. We review here state of the art assays in the detection of enzymatic activities using recent advances in nanoscience. Novel methods based on the use of nanoparticles lead to increased sensitivity and decreased costs for bioanalysis based on enzymes as recognition elements and signal amplifiers in Enzyme-Linked Immunosorbent Assays (ELISA). Novel approaches toward the detection of enzymatic activities are based on biocatalytic synthesis, modulation, etching, and aggregation of nanoparticles under physiological conditions.

  15. Apple phenolics and their contribution to enzymatic browning reactions

    Directory of Open Access Journals (Sweden)

    Wiesław Oleszek

    2014-01-01

    Full Text Available Chlorogenic acid, epicatechin, procyanidin B2 and C1 were isolated from apple skin. These compounds as well as quercetine and phloretine glycosides isolated from apples were studied individually and as mixtures for their participation in the enzymatic browning reactions. The importance of quercetine glycosides and the synergistic effect of phloridzin and phloretine xyloglucoside with chlorogenic acid and flavans in the browning reaction are reported.

  16. Enzymatic spectrophotometric reaction rate determination of aspartame

    Directory of Open Access Journals (Sweden)

    Trifković Kata T.

    2015-01-01

    Full Text Available Aspartame is an artificial sweetener of low caloric value (approximately 200 times sweeter than sucrose. Aspartame is currently permitted for use in food and beverage production in more than 90 countries. The application of aspartame in food products requires development of rapid, inexpensive and accurate method for its determination. The new assay for determination of aspartame was based on set of reactions that are catalyzed by three different enzymes: α-chymotrypsin, alcohol oxidase and horseradish peroxidase. Optimization of the proposed method was carried out for: (i α-chymotrypsin activity; (ii time allowed for α-chymotrypsin action, (iii temperature. Evaluation of the developed method was done by determining aspartame content in “diet” drinks, as well as in artificial sweetener pills. [Projekat Ministarstva nauke Republike Srbije, br. III46010

  17. Novel investigation of enzymatic biodiesel reaction by isothermal calorimetry

    DEFF Research Database (Denmark)

    Søtoft, Lene Fjerbaek; Westh, Peter; Christensen, Knud V.

    2010-01-01

    Isothermal calorimetry (ITC) was used to investigate solvent-free enzymatic biodiesel production. The transesterification of rapeseed oil with methanol and ethanol was catalyzed by immobilized lipase Novozym 435 at 40 °C. The aim of the study was to determine reaction enthalpy for the enzymatic...... transesterification and to elucidate the mass transfer and energetic processes taking place. Based on the measured enthalpy and composition change in the system, the heat of reaction at 40 °C for the two systems was determined as −9.8 ± 0.9 kJ/mole biodiesel formed from rapeseed oil and methanol, and −9.3 ± 0.7 k...

  18. Recent Trends in Quantum Chemical Modeling of Enzymatic Reactions.

    Science.gov (United States)

    Himo, Fahmi

    2017-05-24

    The quantum chemical cluster approach is a powerful method for investigating enzymatic reactions. Over the past two decades, a large number of highly diverse systems have been studied and a great wealth of mechanistic insight has been developed using this technique. This Perspective reviews the current status of the methodology. The latest technical developments are highlighted, and challenges are discussed. Some recent applications are presented to illustrate the capabilities and progress of this approach, and likely future directions are outlined.

  19. Enzymatic processes in alternative reaction media: a mini review

    Directory of Open Access Journals (Sweden)

    Mansour Ghaffari-Moghaddam

    2015-08-01

    Full Text Available Biocatalysis is a growing field in the production of fine chemicals and will most probably increase its share in the future. Enzymatic reactions are carried out under mild conditions, i.e., non-toxic solvents, low temperature and pressure, which eliminates most environmental drawbacks associated with conventional production methods. The superiority of chemo-, regio- and enantioselectivity of enzymes exhibit significant advantages over conventional catalysts for production of fine chemicals, flavors, fragrances, agrochemicals and pharmaceuticals. Enzymes can function both in aqueous and non-aqueous solvents. As a result of the growing scientific and industrial interest towards green chemistry, green solvent systems, which are mainly water, supercritical fluids, ionic liquids, fluorinated solvents, and solvent-free systems have become more popular in biocatalysis. However, the activity and selectivity of an enzyme is heavily dependent on solvent properties. In this review, various green solvents were classified and some of their influential features on enzyme activity were discussed.

  20. Distance-dependent diffusion-controlled reaction of •NO and O2•- at chemical equilibrium with ONOO-.

    Science.gov (United States)

    Botti, Horacio; Möller, Matías N; Steinmann, Daniel; Nauser, Thomas; Koppenol, Willem H; Denicola, Ana; Radi, Rafael

    2010-12-16

    The fast reaction of (•)NO and O(2)(•-) to give ONOO(-) has been extensively studied at irreversible conditions, but the reasons for the wide variations in observed forward rate constants (3.8 ≤ k(f) ≤ 20 × 10(9) M(-1) s(-1)) remain unexplained. We characterized the diffusion-dependent aqueous (pH > 12) chemical equilibrium of the form (•)NO + O(2)(•-) = ONOO(-) with respect to its dependence on temperature, viscosity, and [ONOO(-)](eq) by determining [ONOO(-)](eq) and [(•)NO](eq). The equilibrium forward reaction rate constant (k(f)(eq)) has negative activation energy, in contrast to that found under irreversible conditions. In contradiction to the law of mass action, we demonstrate that the equilibrium constant depends on ONOO(-) concentration. Therefore, a wide range of k(f)(eq) values could be derived (7.5-21 × 10(9) M(-1) s(-1)). Of general interest, the variations in k(f) can thus be explained by its dependence on the distance between ONOO(-) particles (sites of generation of (•)NO and O(2)(•-)).

  1. Enzymatic Halogenation and Dehalogenation Reactions: Pervasive and Mechanistically Diverse.

    Science.gov (United States)

    Agarwal, Vinayak; Miles, Zachary D; Winter, Jaclyn M; Eustáquio, Alessandra S; El Gamal, Abrahim A; Moore, Bradley S

    2017-04-26

    Naturally produced halogenated compounds are ubiquitous across all domains of life where they perform a multitude of biological functions and adopt a diversity of chemical structures. Accordingly, a diverse collection of enzyme catalysts to install and remove halogens from organic scaffolds has evolved in nature. Accounting for the different chemical properties of the four halogen atoms (fluorine, chlorine, bromine, and iodine) and the diversity and chemical reactivity of their organic substrates, enzymes performing biosynthetic and degradative halogenation chemistry utilize numerous mechanistic strategies involving oxidation, reduction, and substitution. Biosynthetic halogenation reactions range from simple aromatic substitutions to stereoselective C-H functionalizations on remote carbon centers and can initiate the formation of simple to complex ring structures. Dehalogenating enzymes, on the other hand, are best known for removing halogen atoms from man-made organohalogens, yet also function naturally, albeit rarely, in metabolic pathways. This review details the scope and mechanism of nature's halogenation and dehalogenation enzymatic strategies, highlights gaps in our understanding, and posits where new advances in the field might arise in the near future.

  2. Phosphorylated aminosugars: Synthesis, properties, and reactivity in enzymatic reactions

    International Nuclear Information System (INIS)

    Sem, D.S.; Cleland, W.W.

    1991-01-01

    A number of phosphorylated aminosugars have been prepared and tested as substrates for metabolic reactions. 6-Aminoglucose is a slow substrate for yeast hexokinase with a V max that is only 0.012% that of glucose. While V max is pH independent, V/K decreases below the pK of 9.0 of the amino group. 6-Aminoglucose is a competitive inhibitor vs glucose with a K i value increasing below the pK of 9 but leveling off at 33 mM below pH 7.16. Thus, protonation decreases binding affinity by 2.4 kcal/mol and only the neutral amine is catalytically competent. 6-Aminoglucose-6-P was synthesized enzymatically with hexokinase. Its pK's determined by 31 P NMR were 2.46 and 8.02 (α anomer) and 2.34 and 7.85 (β anomer), with a β:α ratio of 3.0. It is most stable at pH 12, while as a monoanion its half-life is 3 h. The 31 P NMR chemical shifts of the analogues are 8-8.5 ppm at pH 9.5. Their relative stability is 6-aminogluconate-6-P > 3-aminoglyceraldehyde-3-P > 6-aminoglucose-6-P > 6-aminofructose-1,6-bis-P≅6-aminofructose-6-P > 5-aminoribulose-5-P. These analogues were tested as substrates for their respective enzymes. Phosphorylated aminosugars are thus excellent isosteric analogues of normal metabolic intermediates, except for reactions catalyzed by kinases

  3. Process technology for multi-enzymatic reaction systems

    DEFF Research Database (Denmark)

    Xue, Rui; Woodley, John M.

    2012-01-01

    In recent years, biocatalysis has started to provide an important green tool in synthetic organic chemistry. Currently, the idea of using multi-enzymatic systems for industrial production of chemical compounds becomes increasingly attractive. Recent examples demonstrate the potential of enzymatic...... synthesis and fermentation as an alternative to chemical-catalysis for the production of pharmaceuticals and fine chemicals. In particular, the use of multiple enzymes is of special interest. However, many challenges remain in the scale-up of a multi-enzymatic system. This review summarizes and discusses...... the technology options and strategies that are available for the development of multi-enzymatic processes. Some engineering tools, including kinetic models and operating windows, for developing and evaluating such processes are also introduced....

  4. Method of reduction of nitroaromatics by enzymatic reaction with redox enzymes

    Science.gov (United States)

    Shah, Manish M.

    2000-01-01

    A method for the controlled reduction of nitroaromatic compounds such as nitrobenzene and 2,4,6-trinitrotoluene by enzymatic reaction with redox enzymes, such as Oxyrase (Trademark of Oxyrase, Inc., Mansfield, Ohio).

  5. Co-solvent effects on reaction rate and reaction equilibrium of an enzymatic peptide hydrolysis.

    Science.gov (United States)

    Wangler, A; Canales, R; Held, C; Luong, T Q; Winter, R; Zaitsau, D H; Verevkin, S P; Sadowski, G

    2018-04-25

    This work presents an approach that expresses the Michaelis constant KaM and the equilibrium constant Kth of an enzymatic peptide hydrolysis based on thermodynamic activities instead of concentrations. This provides KaM and Kth values that are independent of any co-solvent. To this end, the hydrolysis reaction of N-succinyl-l-phenylalanine-p-nitroanilide catalysed by the enzyme α-chymotrypsin was studied in pure buffer and in the presence of the co-solvents dimethyl sulfoxide, trimethylamine-N-oxide, urea, and two salts. A strong influence of the co-solvents on the measured Michaelis constant (KM) and equilibrium constant (Kx) was observed, which was found to be caused by molecular interactions expressed as activity coefficients. Substrate and product activity coefficients were used to calculate the activity-based values KaM and Kth for the co-solvent free reaction. Based on these constants, the co-solvent effect on KM and Kx was predicted in almost quantitative agreement with the experimental data. The approach presented here does not only reveal the importance of understanding the thermodynamic non-ideality of reactions taking place in biological solutions and in many technological applications, it also provides a framework for interpreting and quantifying the multifaceted co-solvent effects on enzyme-catalysed reactions that are known and have been observed experimentally for a long time.

  6. Multicompartment Artificial Organelles Conducting Enzymatic Cascade Reactions inside Cells

    DEFF Research Database (Denmark)

    Gallardo, Maria Godoy; Labay, Cédric Pierre; Trikalitis, Vasileios

    2017-01-01

    Cell organelles are subcellular structures entrapping a set of enzymes to achieve a specific functionality. The incorporation of artificial organelles into cells is a novel medical paradigm which might contribute to the treatment of various cell disorders by replacing malfunctioning organelles....... In particular, artificial organelles are expected to be a powerful solution in the context of enzyme replacement therapy since enzymatic malfunction is the primary cause of organelle dysfunction. Although several attempts have been made to encapsulate enzymes within a carrier vehicle, only few intracellularly...

  7. Modular rate laws for enzymatic reactions: thermodynamics, elasticities and implementation.

    Science.gov (United States)

    Liebermeister, Wolfram; Uhlendorf, Jannis; Klipp, Edda

    2010-06-15

    Standard rate laws are a key requisite for systematically turning metabolic networks into kinetic models. They should provide simple, general and biochemically plausible formulae for reaction velocities and reaction elasticities. At the same time, they need to respect thermodynamic relations between the kinetic constants and the metabolic fluxes and concentrations. We present a family of reversible rate laws for reactions with arbitrary stoichiometries and various types of regulation, including mass-action, Michaelis-Menten and uni-uni reversible Hill kinetics as special cases. With a thermodynamically safe parameterization of these rate laws, parameter sets obtained by model fitting, sampling or optimization are guaranteed to lead to consistent chemical equilibrium states. A reformulation using saturation values yields simple formulae for rates and elasticities, which can be easily adjusted to the given stationary flux distributions. Furthermore, this formulation highlights the role of chemical potential differences as thermodynamic driving forces. We compare the modular rate laws to the thermodynamic-kinetic modelling formalism and discuss a simplified rate law in which the reaction rate directly depends on the reaction affinity. For automatic handling of modular rate laws, we propose a standard syntax and semantic annotations for the Systems Biology Markup Language. An online tool for inserting the rate laws into SBML models is freely available at www.semanticsbml.org. Supplementary data are available at Bioinformatics online.

  8. Enzymatic conformational fluctuations along the reaction coordinate of cytidine deaminase

    OpenAIRE

    Noonan, Ryan C.; Carter, Charles W.; Bagdassarian, Carey K.

    2002-01-01

    Analysis of the crystal structures for cytidine deaminase complexed with substrate analog 3-deazacytidine, transition-state analog zebularine 3,4-hydrate, and product uridine establishes significant changes in the magnitude of atomic-scale fluctuations along the (approximate) reaction coordinate of this enzyme. Differences in fluctuations between the substrate analog complex, transition-state analog complex, and product complex are monitored via changes in corresponding crystallographic tempe...

  9. Carpatizine, a novel bridged oxazine derivative generated by non-enzymatic reactions.

    Science.gov (United States)

    Fu, Peng; MacMillan, John B

    2017-06-27

    Carpatizine (1), a new bridged oxazine derivative, was isolated from a marine-derived Streptomyces strain SNE-011. The structure was fully determined by spectroscopic analysis, ECD calculations and chemical methods. A plausible non-enzymatic reaction mechanism from daryamide D leading to carpatizine was presented, which was confirmed by chemical transformation.

  10. Solvent Optimization for Efficient Enzymatic Monoacylglycerol Production Based on a Glycerolysis Reaction

    DEFF Research Database (Denmark)

    Damstrup, Marianne; Jensen, Tine; Sparsø, Flemming V.

    2005-01-01

    This study was aimed at screening solvent systems of varying polarities to identify suitable solvents for efficient and practical enzymatic glycerolysis. Several pure solvents and solvent mixtures were screened in a batch reaction system consisting of glycerol, sunflower oil, and Novozymo (R) 435...

  11. Non-Enzymatic biopolymerization reactions supported by heterogeneous media

    DEFF Research Database (Denmark)

    Monnard, Pierre-Alain

    2011-01-01

    Heterogeneous media, such as micro-structured aqueous environments, could offer an alternative approach to the synthesis of biopolymers with novel functions. Structured media are here defined as specialized, self-assembled structures that are formed, e.g, by amphiphiles, such as liposomes, emulsion...... compartments and lipid-bilayer lattices. Another kind of media is represented by co-existing, self-assembled phases in the reaction medium, e.g., in water-ice matrices. These media have the capacity to assemble chemical molecules or complex catalytic assemblies into unique configurations that are unstable...

  12. The dual effects of Maillard reaction and enzymatic hydrolysis on the antioxidant activity of milk proteins.

    Science.gov (United States)

    Oh, N S; Lee, H A; Lee, J Y; Joung, J Y; Lee, K B; Kim, Y; Lee, K W; Kim, S H

    2013-08-01

    The objective of this study was to determine the enhanced effects on the biological characteristics and antioxidant activity of milk proteins by the combination of the Maillard reaction and enzymatic hydrolysis. Maillard reaction products were obtained from milk protein preparations, such as whey protein concentrates and sodium caseinate with lactose, by heating at 55°C for 7 d in sodium phosphate buffer (pH 7.4). The Maillard reaction products, along with untreated milk proteins as controls, were hydrolyzed for 0 to 3h with commercial proteases Alcalase, Neutrase, Protamex, and Flavorzyme (Novozymes, Bagsværd, Denmark). The antioxidant activity of hydrolyzed Maillard reaction products was determined by reaction with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, their 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity, and the ability to reduce ferric ions. Further characteristics were evaluated by the o-phthaldialdehyde method and sodium dodecyl sulfate-PAGE. The degree of hydrolysis gradually increased in a time-dependent manner, with the Alcalase-treated Maillard reaction products being the most highly hydrolyzed. Radical scavenging activities and reducing ability of hydrolyzed Maillard reaction products increased with increasing hydrolysis time. The combined products of enzymatic hydrolysis and Maillard reaction showed significantly greater antioxidant activity than did hydrolysates or Maillard reaction products alone. The hydrolyzed Maillard reaction products generated by Alcalase showed significantly higher antioxidant activity when compared with the other protease products and the antioxidant activity was higher for the whey protein concentrate groups than for the sodium caseinate groups. These findings indicate that Maillard reaction products, coupled with enzymatic hydrolysis, could act as potential antioxidants in the pharmaceutical, food, and dairy industries. Copyright © 2013 American Dairy Science Association

  13. Quantum Chemical Modeling of Enzymatic Reactions: The Case of Decarboxylation.

    Science.gov (United States)

    Liao, Rong-Zhen; Yu, Jian-Guo; Himo, Fahmi

    2011-05-10

    We present a systematic study of the decarboxylation step of the enzyme aspartate decarboxylase with the purpose of assessing the quantum chemical cluster approach for modeling this important class of decarboxylase enzymes. Active site models ranging in size from 27 to 220 atoms are designed, and the barrier and reaction energy of this step are evaluated. To model the enzyme surrounding, homogeneous polarizable medium techniques are used with several dielectric constants. The main conclusion is that when the active site model reaches a certain size, the solvation effects from the surroundings saturate. Similar results have previously been obtained from systematic studies of other classes of enzymes, suggesting that they are of a quite general nature.

  14. Precision Synthesis of Functional Polysaccharide Materials by Phosphorylase-Catalyzed Enzymatic Reactions

    Directory of Open Access Journals (Sweden)

    Jun-ichi Kadokawa

    2016-04-01

    Full Text Available In this review article, the precise synthesis of functional polysaccharide materials using phosphorylase-catalyzed enzymatic reactions is presented. This particular enzymatic approach has been identified as a powerful tool in preparing well-defined polysaccharide materials. Phosphorylase is an enzyme that has been employed in the synthesis of pure amylose with a precisely controlled structure. Similarly, using a phosphorylase-catalyzed enzymatic polymerization, the chemoenzymatic synthesis of amylose-grafted heteropolysaccharides containing different main-chain polysaccharide structures (e.g., chitin/chitosan, cellulose, alginate, xanthan gum, and carboxymethyl cellulose was achieved. Amylose-based block, star, and branched polymeric materials have also been prepared using this enzymatic polymerization. Since phosphorylase shows a loose specificity for the recognition of substrates, different sugar residues have been introduced to the non-reducing ends of maltooligosaccharides by phosphorylase-catalyzed glycosylations using analog substrates such as α-d-glucuronic acid and α-d-glucosamine 1-phosphates. By means of such reactions, an amphoteric glycogen and its corresponding hydrogel were successfully prepared. Thermostable phosphorylase was able to tolerate a greater variance in the substrate structures with respect to recognition than potato phosphorylase, and as a result, the enzymatic polymerization of α-d-glucosamine 1-phosphate to produce a chitosan stereoisomer was carried out using this enzyme catalyst, which was then subsequently converted to the chitin stereoisomer by N-acetylation. Amylose supramolecular inclusion complexes with polymeric guests were obtained when the phosphorylase-catalyzed enzymatic polymerization was conducted in the presence of the guest polymers. Since the structure of this polymeric system is similar to the way that a plant vine twines around a rod, this polymerization system has been named

  15. Effect of micro-stirring on enzymatic reaction kinetics inside a biomimetic container

    Science.gov (United States)

    Gozen, Irep; Horowitz, Viva; Chambers, Zachary; Manoharan, Vinothan

    The intracellular environment is dynamic, influenced by the motion of active machinery such as cytoskeleton filaments and molecular motors. To understand whether and how such activity affects the rates of diffusion-limited reactions, we construct a model system consisting of a phospholipid vesicle encapsulating a small number of micro- or nanoparticles, the active motion of which can be induced by chemical or magnetic cues. We aim to determine a relation between active motion of particles and rates of enzymatic reactions in the confined volume. Our findings might illuminate how active motion influences cytoplasmic reaction dynamics, or may have played a role in protocell genetics.

  16. The Effect of Irradiation Treatment on the Non-Enzymatic Browning Reaction in Legume Seeds

    International Nuclear Information System (INIS)

    El-Niely, H.F.G.

    2013-01-01

    The present study was conducted to evaluate the effects of gamma irradiation treatment, at room temperature, on the non-enzymatic browning reaction (Millerd reaction products, MRPs) generated in soybeans, broad beans and dried peas seeds at dose levels of 10, 30 and 60 kGy and their effects on the chemical constituents, soluble protein, available lysine and in vitro protein digestibility. The formation of MRPs in the studied legumes was assayed by monitoring the formation of brown pigments (browning intensity) by spectrophotometric method. The results revealed that the chemical composition of irradiated legumes showed non-significant differences relative to the raw one. A dose dependent decrease in soluble proteins and available lysine in the three legumes were observed. The non-enzymatic browning reaction was significantly increased with increasing the radiation dose, which was proved by changes in browning index tests. At the same time, the in vitro protein digestibility was increased after irradiation up to 60 kGy. Irradiation of dried peas with 60 kGy produced higher browning index than the other legumes. A positive correlation was observed between the radiation dose and the browning index for soybeans (R2= 0.96), broad beans (R2 = 0.81) and dried peas (R2 = 0.97) which means that 96%, 81% and 97 of the variation in the incidence of non-enzymatic browning reaction in soybean, broad bean and dried peas, respectively, are due to the effect of irradiation treatments. The present study suggests that the formation of non-enzymatic browning reaction did not impair the nutritional quality of legumes, therefore, the process of irradiation was helpful in increasing the in vitro protein digestibility of studied legumes. These results clearly indicated that gamma irradiation processing at the studied doses can add valuable effects to the studied legumes

  17. Bistability, electric potentials and sensor behaviour in an enzymatic reaction system

    International Nuclear Information System (INIS)

    Malchow, H.; Felber, F.

    1987-07-01

    A special ionic enzyme kinetics in a continuously stirred flow reactor which is membrane coupled to a reservoir is considered starting from a general expression for the substrate dependence of enzymatic reaction rates including pH effects. Both bistability of the reaction and electric potentials between the interior and exterior of the reactor can be observed having regard to mass and charge conservation as well as global electroneutrality. The sudden jumps at critical concentration values from one stable solution branch to the other on a hysteresis loop are supposed to be the basic action principle of a non-equilibrium concentration threshold sensor. (author). 38 refs, 3 figs

  18. The In Situ Enzymatic Screening (ISES) Approach to Reaction Discovery and Catalyst Identification.

    Science.gov (United States)

    Swyka, Robert A; Berkowitz, David B

    2017-12-14

    The importance of discovering new chemical transformations and/or optimizing catalytic combinations has led to a flurry of activity in reaction screening. The in situ enzymatic screening (ISES) approach described here utilizes biological tools (enzymes/cofactors) to advance chemistry. The protocol interfaces an organic reaction layer with an adjacent aqueous layer containing reporting enzymes that act upon the organic reaction product, giving rise to a spectroscopic signal. ISES allows the experimentalist to rapidly glean information on the relative rates of a set of parallel organic/organometallic reactions under investigation, without the need to quench the reactions or draw aliquots. In certain cases, the real-time enzymatic readout also provides information on sense and magnitude of enantioselectivity and substrate specificity. This article contains protocols for single-well (relative rate) and double-well (relative rate/enantiomeric excess) ISES, in addition to a colorimetric ISES protocol and a miniaturized double-well procedure. © 2017 by John Wiley & Sons, Inc. Copyright © 2017 John Wiley & Sons, Inc.

  19. Design of an embedded inverse-feedforward biomolecular tracking controller for enzymatic reaction processes.

    Science.gov (United States)

    Foo, Mathias; Kim, Jongrae; Sawlekar, Rucha; Bates, Declan G

    2017-04-06

    Feedback control is widely used in chemical engineering to improve the performance and robustness of chemical processes. Feedback controllers require a 'subtractor' that is able to compute the error between the process output and the reference signal. In the case of embedded biomolecular control circuits, subtractors designed using standard chemical reaction network theory can only realise one-sided subtraction, rendering standard controller design approaches inadequate. Here, we show how a biomolecular controller that allows tracking of required changes in the outputs of enzymatic reaction processes can be designed and implemented within the framework of chemical reaction network theory. The controller architecture employs an inversion-based feedforward controller that compensates for the limitations of the one-sided subtractor that generates the error signals for a feedback controller. The proposed approach requires significantly fewer chemical reactions to implement than alternative designs, and should have wide applicability throughout the fields of synthetic biology and biological engineering.

  20. The effect of irradiation temperature on the non-enzymatic browning reaction in cooked rice

    International Nuclear Information System (INIS)

    Lee, Ju-Woon; Oh, Sang-Hee; Kim, Jae-Hun; Byun, Eui-Hong; Ree Kim, Mee; Baek, Min; Byun, Myung-Woo

    2007-01-01

    The effect of irradiation temperature on the non-enzymatic browning reaction in a sugar-glycine solution and cooked rice generated by gamma irradiation was evaluated in the present study. When the sugar-glycine solution and cooked rice were irradiated at room temperature, the browning reaction was dramatically increased during the post-irradiation period. In the case of irradiation at below the freezing point, the browning by irradiation was retarded during not only irradiation but also a post-irradiation period. The changes of the sugar profile, such as a sugar loss or reducing power of the irradiated sugar-glycine solution and the electron spin resonance signal intensity of the irradiated cooked rice were also decreased with lower irradiation temperature. The present results may suggest that the production of free radicals and a radiolysis product is inhibited during gamma irradiation in the frozen state and it may prevent the browning reaction generated by gamma irradiation from occurring

  1. The effect of irradiation temperature on the non-enzymatic browning reaction in cooked rice

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ju-Woon [Radiation Application Research Division, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, PO Box 1266, Jeongeup, Jeonbuk 580-185 (Korea, Republic of); Oh, Sang-Hee [Radiation Application Research Division, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, PO Box 1266, Jeongeup, Jeonbuk 580-185 (Korea, Republic of); Kim, Jae-Hun [Radiation Application Research Division, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, PO Box 1266, Jeongeup, Jeonbuk 580-185 (Korea, Republic of); Byun, Eui-Hong [Radiation Application Research Division, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, PO Box 1266, Jeongeup, Jeonbuk 580-185 (Korea, Republic of); Ree Kim, Mee [Department of Food and Nutrition, Chungnam National University, Gung-Dong 220, Yuseong, Daejeon 305-764 (Korea, Republic of); Baek, Min [Atomic Energy Policy Division, Ministry of Science and Technology, Government Complex-Gwacheon, Kyunggi 427-715 (Korea, Republic of); Byun, Myung-Woo [Radiation Application Research Division, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, PO Box 1266, Jeongeup, Jeonbuk 580-185 (Korea, Republic of)]. E-mail: mwbyun@kaeri.re.kr

    2007-05-15

    The effect of irradiation temperature on the non-enzymatic browning reaction in a sugar-glycine solution and cooked rice generated by gamma irradiation was evaluated in the present study. When the sugar-glycine solution and cooked rice were irradiated at room temperature, the browning reaction was dramatically increased during the post-irradiation period. In the case of irradiation at below the freezing point, the browning by irradiation was retarded during not only irradiation but also a post-irradiation period. The changes of the sugar profile, such as a sugar loss or reducing power of the irradiated sugar-glycine solution and the electron spin resonance signal intensity of the irradiated cooked rice were also decreased with lower irradiation temperature. The present results may suggest that the production of free radicals and a radiolysis product is inhibited during gamma irradiation in the frozen state and it may prevent the browning reaction generated by gamma irradiation from occurring.

  2. Modeling networks of coupled enzymatic reactions using the total quasi-steady state approximation.

    Directory of Open Access Journals (Sweden)

    Andrea Ciliberto

    2007-03-01

    Full Text Available In metabolic networks, metabolites are usually present in great excess over the enzymes that catalyze their interconversion, and describing the rates of these reactions by using the Michaelis-Menten rate law is perfectly valid. This rate law assumes that the concentration of enzyme-substrate complex (C is much less than the free substrate concentration (S0. However, in protein interaction networks, the enzymes and substrates are all proteins in comparable concentrations, and neglecting C with respect to S0 is not valid. Borghans, DeBoer, and Segel developed an alternative description of enzyme kinetics that is valid when C is comparable to S0. We extend this description, which Borghans et al. call the total quasi-steady state approximation, to networks of coupled enzymatic reactions. First, we analyze an isolated Goldbeter-Koshland switch when enzymes and substrates are present in comparable concentrations. Then, on the basis of a real example of the molecular network governing cell cycle progression, we couple two and three Goldbeter-Koshland switches together to study the effects of feedback in networks of protein kinases and phosphatases. Our analysis shows that the total quasi-steady state approximation provides an excellent kinetic formalism for protein interaction networks, because (1 it unveils the modular structure of the enzymatic reactions, (2 it suggests a simple algorithm to formulate correct kinetic equations, and (3 contrary to classical Michaelis-Menten kinetics, it succeeds in faithfully reproducing the dynamics of the network both qualitatively and quantitatively.

  3. A Method for the Determination of Bi-substrate Kinetic Coefficients: the Example of the b-D-glucose- NAD-GDH Enzymatic Reaction

    Directory of Open Access Journals (Sweden)

    Jean BERTHIER

    2015-08-01

    Full Text Available Colorimetric detection of glucose in sample liquids such as human plasma is made by using enzymatic reactions. Either glucose oxidase (GOX or glucose dehydrogenase (GDH can be used to convert glucose. In the multi reactional scheme, the first enzymatic reaction is determinant. We focused here on the study of the enzyme GDH together with the enzymatic cofactor NAD (nicotinamide adenine dinucleotide. This reaction falls in the category of ternary enzymatic reactions. Such reactions depend on four parameters. A method to determine these four parameters is presented in this work, based on a comparison between a series of experiments and the theory. The best values of the parameters are indicated.

  4. Conferring specificity in redox pathways by enzymatic thiol/disulfide exchange reactions.

    Science.gov (United States)

    Netto, Luis Eduardo S; de Oliveira, Marcos Antonio; Tairum, Carlos A; da Silva Neto, José Freire

    2016-01-01

    Thiol-disulfide exchange reactions are highly reversible, displaying nucleophilic substitutions mechanism (S(N)2 type). For aliphatic, low molecular thiols, these reactions are slow, but can attain million times faster rates in enzymatic processes. Thioredoxin (Trx) proteins were the first enzymes described to accelerate thiol-disulfide exchange reactions and their high reactivity is related to the high nucleophilicity of the attacking thiol. Substrate specificity in Trx is achieved by several factors, including polar, hydrophobic, and topological interactions through a groove in the active site. Glutaredoxin (Grx) enzymes also contain the Trx fold, but they do not share amino acid sequence similarity with Trx. A conserved glutathione binding site is a typical feature of Grx that can reduce substrates by two mechanisms (mono and dithiol). The high reactivity of Grx enzymes is related to the very acid pK(a) values of reactive Cys that plays roles as good leaving groups. Therefore, although distinct oxidoreductases catalyze similar thiol–disulfide exchange reactions, their enzymatic mechanisms vary. PDI and DsbA are two other oxidoreductases, but they are involved in disulfide bond formation, instead of disulfide reduction, which is related to the oxidative environment where they are found. PDI enzymes and DsbC are endowed with disulfide isomerase activity, which is related with their tetra-domain architecture. As illustrative description of specificity in thiol-disulfide exchange, redox aspects of transcription activation in bacteria, yeast, and mammals are presented in an evolutionary perspective. Therefore, thiol-disulfide exchange reactions play important roles in conferring specificity to pathways, a required feature for signaling.

  5. Moessbauer- and EPR-Snapshots of an Enzymatic Reaction: The Cytochrome P450 Reaction Cycle

    Energy Technology Data Exchange (ETDEWEB)

    Schuenemann, V. [University of Luebeck, Institute of Physics (Germany); Jung, C. [Max-Delbrueck-Center for Molecular Medicine (Germany); Lendzian, F. [Technical University, PC 14, Max-Volmer Laboratory for Biophysical Chemistry (Germany); Barra, A.-L. [Grenoble High Magnetic Field Laboratory (France); Teschner, T.; Trautwein, A. X. [University of Luebeck, Institute of Physics (Germany)

    2004-12-15

    In this communication we present a complimentary Moessbauer- and EPR-study of the time dependance of the reaction of substrate free P450cam with peracetic acid within a time region ranging from 8 ms up to 5 min. An Fe(IV) species as well as a tyrosyl radical residing on the amino acid residue Tyr96 have been identified as reaction intermediates. These species possibly are formed by the reduction of compound I by means of transferring an electron from Tyr 96 to the heme moiety.

  6. Moessbauer- and EPR-Snapshots of an Enzymatic Reaction: The Cytochrome P450 Reaction Cycle

    International Nuclear Information System (INIS)

    Schuenemann, V.; Jung, C.; Lendzian, F.; Barra, A.-L.; Teschner, T.; Trautwein, A. X.

    2004-01-01

    In this communication we present a complimentary Moessbauer- and EPR-study of the time dependance of the reaction of substrate free P450cam with peracetic acid within a time region ranging from 8 ms up to 5 min. An Fe(IV) species as well as a tyrosyl radical residing on the amino acid residue Tyr96 have been identified as reaction intermediates. These species possibly are formed by the reduction of compound I by means of transferring an electron from Tyr 96 to the heme moiety.

  7. A general framework for thermodynamically consistent parameterization and efficient sampling of enzymatic reactions.

    Directory of Open Access Journals (Sweden)

    Pedro Saa

    2015-04-01

    the kinetic behaviour of these enzymes, but it also provided insights about the particular features underpinning the observed kinetics. Overall, this framework will enable systematic parameterization and sampling of enzymatic reactions.

  8. Preparation and Characterization of Enzyme Compartments in UV-Cured Polyurethane-Based Materials and Their Application in Enzymatic Reactions

    Directory of Open Access Journals (Sweden)

    Diana Uhrich

    2017-11-01

    Full Text Available The preparation and characterization of UV-cured polyurethane-based materials for the mild inclusion immobilization of enzymes was investigated. Full curing of the polymer precursor/enzyme solution mixture was realized by a short irradiation with UV-light at ambient temperatures. The included aqueous enzyme solution remains highly dispersed in the polymer material with an even size distribution throughout the polymer material. The presented concept provides stable enzyme compartments which were applied for an alcohol dehydrogenase-catalyzed reduction reaction in organic solvents. Cofactor regeneration was achieved by a substrate-coupled approach via 2-propanol or an enzyme-coupled approach by a glucose dehydrogenase. This reaction concept can also be used for a simultaneous application of contrary biocatalytic reaction conditions within an enzymatic cascade reaction. Independent polymer-based reaction compartments were provided for two incompatible enzymatic reaction systems (alcohol dehydrogenase and hydroxynitrile lyase, while the relevant reactants diffuse between the applied compartments.

  9. Specific inflammatory response of Anemonia sulcata (Cnidaria) after bacterial injection causes tissue reaction and enzymatic activity alteration.

    Science.gov (United States)

    Trapani, M R; Parisi, M G; Parrinello, D; Sanfratello, M A; Benenati, G; Palla, F; Cammarata, M

    2016-03-01

    The evolution of multicellular organisms was marked by adaptations to protect against pathogens. The mechanisms for discriminating the ''self'' from ''non-self" have evolved into a long history of cellular and molecular strategies, from damage repair to the co-evolution of host-pathogen interactions. We investigated the inflammatory response in Anemonia sulcata (Cnidaria: Anthozoa) following injection of substances that varied in type and dimension, and observed clear, strong and specific reactions, especially after injection of Escherichia coli and Vibrio alginolyticus. Moreover, we analyzed enzymatic activity of protease, phosphatase and esterase, showing how the injection of different bacterial strains alters the expression of these enzymes and suggesting a correlation between the appearance of the inflammatory reaction and the modification of enzymatic activities. Our study shows for the first time, a specific reaction and enzymatic responses following injection of bacteria in a cnidarian. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. Bovine glue (BioGlue) is catabolized by enzymatic reaction in the vascular dog model.

    Science.gov (United States)

    Van Belleghem, Yves; Forsyth, Ramses G; Narine, Kishan; Moerman, Annelies; Taeymans, Yves; Van Nooten, Guido J

    2004-06-01

    The aim of the study is to explore the feasibility, patency, and histologic changes of a sutureless vascular anastomotic technique using biological glue as sole fixation method. Eight mongrel dogs (+/-15 kg) underwent direct reanastomosis of their transsected iliac arteries. Both ends were placed on a 5-mm balloon and the anastomosis was secured with biological glue (BioGlue, Cryolife, Kennesaw, GA). No intravascular suture material was used. All survivors were angiographically controlled for patency after 6 weeks and 3 months. Then the animals were euthanized and tissues were obtained for histologic and pathologic examination by light and electron microscopy. All procedures were successful except for 1 animal that died of uncontrollable bleeding at the anastomotic site. All first-time angiographically controlled grafts except three were patent. One animal showed manifest signs of fungal infection. Histology detected early granulocyte infiltration with an important enzymatic reaction adjacent to the surface of glue. Later on, the glue gradually regressed to disappear completely. Fibroblastic neointimal lining was noticed in most of the anastomoses, with some marked differences in the endothelium compared with normal. Good permeability (57%) was observed in this new sutureless anastomotic technique in the canine model. In contrast to previous reported studies we noticed a clear enzymatic breakdown of the glue before total disappearance. It is not yet known to what extend use of the bovine glue was responsible for this phenomenon.

  11. Effect of temperature towards lipid oxidation and non-enzymatic browning reactions in krill oil upon storage

    DEFF Research Database (Denmark)

    Lu, Henna Fung Sieng; Bruheim, I.; Haugsgjerd, B.O.

    2014-01-01

    was assessed by peroxide value and anisidine value, measurement of lipid derived volatiles, lipid classes and antioxidants. The non-enzymatic browning reactions were assessed through the measurement of pyrroles, free amino acids content and Strecker-derived volatiles. The increase of incubation temperature......The main objective of this study was to investigate the effect of temperature towards lipid oxidation and non-enzymatic browning reactions in krill oil upon storage. Krill oil was incubated at two different temperatures (20 and 40°C) for 28 or 42 days. The oxidative stability of krill oil...

  12. Investigation of lipid oxidation and non-enzymatic browning reactions in marine PL emulsions

    DEFF Research Database (Denmark)

    Lu, Henna Fung Sieng; Nielsen, Nina Skall; Baron, Caroline P.

    Marine phospholipids (PL) have received much attention recently due to their numerous advantages. One of these advantages is their better resistance towards oxidation as compared to fish oil. In addition to the antioxidative properties of α-tocopherol and phospholipids, the better oxidative...... stability of marine PL might be attributed to antioxidative properties of pyrroles formed between oxidised lipids with amine groups from phosphatidylethanolamine (PE) or residues amino acids that are present in marine PL. The main objective of this study was to investigate if the presence of amine group...... of amino acids (leucine, methionine and lysine) from 2 authentic standards (PC and PE) and 2 purified marine PL (LC and MPL) through sonication method. Emulsions were incubated at 60 ºC for 0, 2, 4 and 6 days. Non-enzymatic browning reactions were investigated through measurement of i) Strecker aldehydes...

  13. The browning kinetics of the non-enzymatic browning reaction in L-ascorbic acid/basic amino acid systems

    Directory of Open Access Journals (Sweden)

    Ai-Nong YU

    Full Text Available Abstract Under the conditions of weak basis and the reaction temperature range of 110-150 °C, lysine, arginine and histidine were reacted with L-ascorbic acid at equal amount for 30-150 min, respectively and the formation of browning products was monitored with UV–vis spectrometry. The kinetic characteristics of their non-enzymatic browning reaction were investigated. The study results indicated that the non-enzymatic browning reaction of these three amino acids with L-ascorbic acid to form browning products was zero-order reaction. The apparent activation energies for the formation of browning products from L-ascorbic acid/lysine, L-ascorbic acid/arginine and L-ascorbic acid/histidine systems were 54.94, 50.08 and 35.31kJ/mol. The activation energy data indicated the degree of effects of reaction temperature on non-enzymatic browning reaction. Within the temperature range of 110-150 °C, the reaction rate of L-ascorbic acid/lysine system was the fastest one, followed by that of the L-ascorbic acid/arginine system. The reaction rate of L-ascorbic acid/histidine system was the slowest one. Based on the observed kinetic data, the formation mechanisms of browning products were proposed.

  14. Enzymatic Transesterification of Ethyl Ferulate with Fish Oil and Reaction Optimization by Response Surface Methodology

    Directory of Open Access Journals (Sweden)

    Zhiyong Yang

    2012-01-01

    Full Text Available The enzymatic transesterification of ethyl ferulate (EF with fish oil from cod liver was investigated with Novozym® 435 as catalyst under solvent-free conditions. The purpose of the study is to evaluate the synthesis system for the production of feruloyl fish oil in industry. The modified HPLC method was first set up to characterise the reaction products together with liquid chromatography electrospray time-of-flight mass spectrometry (HPLC-ESI-TOF-MS. The influence of the addition of glycerol to the system on the feruloyl acylglycerol profile was investigated in terms of transesterification performance. The bioconversion rate of EF can be significantly increased with the increased formation of feruloyl fish oil products when appropriate amount of glycerol is present in the reaction. Therefore, an equivalent molar amount of glycerol was added to EF for the practical optimization of the system. The mutual effects of temperature (40 to 70 °C, reaction time (1 to 5 days, enzyme load (2 to 20 % and molar ratio of fish oil and EF in the substrate (1 to 5 were thus studied with the assistance of response surface methodology (RSM for the purpose of maximizing the formation of feruloyl fish oil. The models were well fitted and verified. The optimized conditions were found to be: temperature 70 °C, enzyme load 4.3 %, substrate ratio 4.7, and reaction time 5 days. Under these conditions, the maximum conversion of EF reached 92.4 %, and the formation of feruloyl fish oil reached 80.4 %, but the formation of by-product was minimized to 11.4 % only.

  15. An Immunosensing System Using Stilbene Glycoside as a Fluorogenic Substrate for an Enzymatic Reaction Model

    Directory of Open Access Journals (Sweden)

    Ya-Fei Tan

    2008-09-01

    Full Text Available A natural product, stilbene glycoside (2,3,5,4’-tetrahydroxydiphenylethylene-2-O-glucoside, TBG, has been evaluated for the first time as a potential substrate for horseradish peroxidase (HRP-catalyzed fluorogenic reactions. The properties of TBG as a fluorogenic substrate for HRP and its application in a fluorometric enzyme-linked immunosensing system were compared with commercially available substrates such as p-hydroxyphenylpropionic acid (pHPPA, chavicol and Amplex red using Brucella melitensis antibody (BrAb as a model analyte. The immunosensing body based on HRP-BrAb was constructed by dispersing graphite, BrAg and paraffin wax at room temperature. In a competitive immunoassay procedure, the BrAb competed with HRP-BrAb to react with the immobilized BrAg. In the enzymatic reaction, the binding HRP-BrAb on the sensing body surface can catalyze the polymerization reaction of TBG by H2O2 forming fluorescent dimers and causing an increase in fluorescence intensity. TBG showed comparable ability for HRP detection and its enzyme-linked immunosensing reaction system, in a linear detection ranging of 3.5´10-8~7.6´10-6g/L and with a detection limit of 1.7´10-9 g/L. The immobilized biocomposite surface could be regenerated with excellent reproducibility (RSD=3.8% by simply polishing with an alumina paper. The proposed immunosensing system has been used to determine the BrAb in rabbit serum samples with satisfactory results.

  16. Quantum chemical modeling of enzymatic reactions: the case of histone lysine methyltransferase.

    Science.gov (United States)

    Georgieva, Polina; Himo, Fahmi

    2010-06-01

    Quantum chemical cluster models of enzyme active sites are today an important and powerful tool in the study of various aspects of enzymatic reactivity. This methodology has been applied to a wide spectrum of reactions and many important mechanistic problems have been solved. Herein, we report a systematic study of the reaction mechanism of the histone lysine methyltransferase (HKMT) SET7/9 enzyme, which catalyzes the methylation of the N-terminal histone tail of the chromatin structure. In this study, HKMT SET7/9 serves as a representative case to examine the modeling approach for the important class of methyl transfer enzymes. Active site models of different sizes are used to evaluate the methodology. In particular, the dependence of the calculated energies on the model size, the influence of the dielectric medium, and the particular choice of the dielectric constant are discussed. In addition, we examine the validity of some technical aspects, such as geometry optimization in solvent or with a large basis set, and the use of different density functional methods. Copyright 2010 Wiley Periodicals, Inc.

  17. Study on the Spectrophotometric Detection of Free Fatty Acids in Palm Oil Utilizing Enzymatic Reactions

    Directory of Open Access Journals (Sweden)

    Nur Hidayah Azeman

    2015-07-01

    Full Text Available In this paper, a comprehensive study has been made on the detection of free fatty acids (FFAs in palm oil via an optical technique based on enzymatic aminolysis reactions. FFAs in crude palm oil (CPO were converted into fatty hydroxamic acids (FHAs in a biphasic lipid/aqueous medium in the presence of immobilized lipase. The colored compound formed after complexation between FHA and vanadium (V ion solution was proportional to the FFA content in the CPO samples and was analyzed using a spectrophotometric method. In order to develop a rapid detection system, the parameters involved in the aminolysis process were studied. The utilization of immobilized lipase as catalyst during the aminolysis process offers simplicity in the product isolation and the possibility of conducting the process under extreme reaction conditions. A good agreement was found between the developed method using immobilized Thermomyces lanuginose lipase as catalyst for the aminolysis process and the Malaysian Palm Oil Board (MPOB standard titration method (R2 = 0.9453.

  18. Advances in quantum and molecular mechanical (QM/MM) simulations for organic and enzymatic reactions.

    Science.gov (United States)

    Acevedo, Orlando; Jorgensen, William L

    2010-01-19

    Application of combined quantum and molecular mechanical (QM/MM) methods focuses on predicting activation barriers and the structures of stationary points for organic and enzymatic reactions. Characterization of the factors that stabilize transition structures in solution and in enzyme active sites provides a basis for design and optimization of catalysts. Continued technological advances allowed for expansion from prototypical cases to mechanistic studies featuring detailed enzyme and condensed-phase environments with full integration of the QM calculations and configurational sampling. This required improved algorithms featuring fast QM methods, advances in computing changes in free energies including free-energy perturbation (FEP) calculations, and enhanced configurational sampling. In particular, the present Account highlights development of the PDDG/PM3 semi-empirical QM method, computation of multi-dimensional potentials of mean force (PMF), incorporation of on-the-fly QM in Monte Carlo (MC) simulations, and a polynomial quadrature method for efficient modeling of proton-transfer reactions. The utility of this QM/MM/MC/FEP methodology is illustrated for a variety of organic reactions including substitution, decarboxylation, elimination, and pericyclic reactions. A comparison to experimental kinetic results on medium effects has verified the accuracy of the QM/MM approach in the full range of solvents from hydrocarbons to water to ionic liquids. Corresponding results from ab initio and density functional theory (DFT) methods with continuum-based treatments of solvation reveal deficiencies, particularly for protic solvents. Also summarized in this Account are three specific QM/MM applications to biomolecular systems: (1) a recent study that clarified the mechanism for the reaction of 2-pyrone derivatives catalyzed by macrophomate synthase as a tandem Michael-aldol sequence rather than a Diels-Alder reaction, (2) elucidation of the mechanism of action of fatty

  19. Modeling of the Reaction Mechanism of Enzymatic Radical C–C Coupling by Benzylsuccinate Synthase

    Directory of Open Access Journals (Sweden)

    Maciej Szaleniec

    2016-04-01

    Full Text Available Molecular modeling techniques and density functional theory calculations were performed to study the mechanism of enzymatic radical C–C coupling catalyzed by benzylsuccinate synthase (BSS. BSS has been identified as a glycyl radical enzyme that catalyzes the enantiospecific fumarate addition to toluene initiating its anaerobic metabolism in the denitrifying bacterium Thauera aromatica, and this reaction represents the general mechanism of toluene degradation in all known anaerobic degraders. In this work docking calculations, classical molecular dynamics (MD simulations, and DFT+D2 cluster modeling was employed to address the following questions: (i What mechanistic details of the BSS reaction yield the most probable molecular model? (ii What is the molecular basis of enantiospecificity of BSS? (iii Is the proposed mechanism consistent with experimental observations, such as an inversion of the stereochemistry of the benzylic protons, syn addition of toluene to fumarate, exclusive production of (R-benzylsuccinate as a product and a kinetic isotope effect (KIE ranging between 2 and 4? The quantum mechanics (QM modeling confirms that the previously proposed hypothetical mechanism is the most probable among several variants considered, although C–H activation and not C–C coupling turns out to be the rate limiting step. The enantiospecificity of the enzyme seems to be enforced by a thermodynamic preference for binding of fumarate in the pro(R orientation and reverse preference of benzyl radical attack on fumarate in pro(S pathway which results with prohibitively high energy barrier of the radical quenching. Finally, the proposed mechanism agrees with most of the experimental observations, although the calculated intrinsic KIE from the model (6.5 is still higher than the experimentally observed values (4.0 which suggests that both C–H activation and radical quenching may jointly be involved in the kinetic control of the reaction.

  20. Strong negative interference of ethamsylate (Dicynone®) in serum creatinine quantification via enzymatic assay using Trinder reaction.

    Science.gov (United States)

    Wiewiorka, Ondrej; Dastych, Milan; Čermáková, Zdenka

    2013-08-01

    With discrepancies encountered as early as the verification of enzymatic method for quantification of serum creatinine, our research pointed to a later confirmed interference caused by a compound called ethamsylate present in the commonly used antihemorrhagic drug Dicynone. We measured concentrations of creatinine of 10 patients with blood taken before and 15 minutes after the intravenous administration of a 500 mg dose of Dicynone. The creatinine concentration was determined using Jaffe method and enzymatic method that utilize Trinder reaction (Roche) in analyzer Cobas c 501 (Roche AG, Basel, Switzerland). We also monitored concentration of blood creatinine in three patients before and 15 minutes after application of Dicynone (500 mg i.v.) and in the following 6th, 12th, 18th, and 24th hours. We discovered a significant negative bias in creatinine results using enzymatic assay with Trinder reaction in blood taken 15 min after i.v. application of 500 mg Dicynone to patients compared to their pre-application values (average decrease of 47%). Unlike this, the results of compensated Jaffe method yielded steady results in all samples (average deviation 0.6% from original values). However, 12 h after the drug administration comparable results were seen as before the administration. Considering the strong negative interference of ethamsylate in enzymatic assay using Trinder reaction for creatinine quantification, blood from patients with prescribed Dicynone should be taken at least 12 h after the last application of the drug for obtaining the correct creatinine values.

  1. Include dispersion in quantum chemical modeling of enzymatic reactions: the case of isoaspartyl dipeptidase.

    Science.gov (United States)

    Zhang, Hai-Mei; Chen, Shi-Lu

    2015-06-09

    The lack of dispersion in the B3LYP functional has been proposed to be the main origin of big errors in quantum chemical modeling of a few enzymes and transition metal complexes. In this work, the essential dispersion effects that affect quantum chemical modeling are investigated. With binuclear zinc isoaspartyl dipeptidase (IAD) as an example, dispersion is included in the modeling of enzymatic reactions by two different procedures, i.e., (i) geometry optimizations followed by single-point calculations of dispersion (approach I) and (ii) the inclusion of dispersion throughout geometry optimization and energy evaluation (approach II). Based on a 169-atom chemical model, the calculations show a qualitative consistency between approaches I and II in energetics and most key geometries, demonstrating that both approaches are available with the latter preferential since both geometry and energy are dispersion-corrected in approach II. When a smaller model without Arg233 (147 atoms) was used, an inconsistency was observed, indicating that the missing dispersion interactions are essentially responsible for determining equilibrium geometries. Other technical issues and mechanistic characteristics of IAD are also discussed, in particular with respect to the effects of Arg233.

  2. Optimization of reaction parameters for enzymatic glyceride synthesis from fish oil: Ethyl esters versus free fatty acids

    DEFF Research Database (Denmark)

    Ravn, Helle Christine; Damstrup, Marianne L.; Meyer, Anne S.

    2012-01-01

    Enzymatic conversion of fish oil free fatty acids (FFA) or fatty acid ethyl esters (FAE) into glycerides via esterification or transesterification was examined. The reactions catalyzed by Lipozyme™ 435, a Candida antarctica lipase, were optimized. Influence on conversion yields of fatty acid chain...... length, saturation degree, temperature, enzyme dosage, molar ratio glycerol:fatty acids, acyl source composition (w/w ratio FFA:FAE), and reaction time was evaluated collectively by multiple linear regression. All reaction variables influenced the conversion into glycerides. Transesterification of FAE...

  3. Applications of a single-molecule detection in early disease diagnosis and enzymatic reaction study

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jiangwei [Iowa State Univ., Ames, IA (United States)

    2008-01-01

    Various single-molecule techniques were utilized for ultra-sensitive early diagnosis of viral DNA and antigen and basic mechanism study of enzymatic reactions. DNA of human papilloma virus (HPV) served as the screening target in a flow system. Alexa Fluor 532 (AF532) labeled single-stranded DNA probes were hybridized to the target HPV-16 DNA in solution. The individual hybridized molecules were imaged with an intensified charge-coupled device (ICCD) in two ways. In the single-color mode, target molecules were detected via fluorescence from hybridized probes only. This system could detect HPV-16 DNA in the presence of human genomic DNA down to 0.7 copy/cell and had a linear dynamic range of over 6 orders of magnitude. In the dual-color mode, fluorescence resonance energy transfer (FRET) was employed to achieve zero false-positive count. We also showed that DNA extracts from Pap test specimens did not interfere with the system. A surface-based method was used to improve the throughput of the flow system. HPV-16 DNA was hybridized to probes on a glass surface and detected with a total internal reflection fluorescence (TIRF) microscope. In the single-probe mode, the whole genome and target DNA were fluorescently labeled before hybridization, and the detection limit is similar to the flow system. In the dual-probe mode, a second probe was introduced. The linear dynamic range covers 1.44-7000 copies/cell, which is typical of early infection to near-cancer stages. The dual-probe method was tested with a crudely prepared sample. Even with reduced hybridization efficiency caused by the interference of cellular materials, we were still able to differentiate infected cells from healthy cells. Detection and quantification of viral antigen with a novel single-molecule immunosorbent assay (SMISA) was achieved. Antigen from human immunodeficiency virus type 1(HIV-1) was chosen to be the target in this study. The target was sandwiched between a monoclonal capture antibody and a

  4. Correlating enzymatic browning inhibition and antioxidant ability of Maillard reaction products derived from different amino acids.

    Science.gov (United States)

    Xu, Haining; Zhang, Xiaoming; Karangwa, Eric; Xia, Shuqin

    2017-09-01

    Up to now, only limited research on enzymatic browning inhibition capacity (BIC) of Maillard reaction products (MRPs) has been reported and there are still no overall and systematic researches on MRPs derived from different amino acids. In the present study, BIC and antioxidant capacity, including 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity and Fe 2+ reducing power activity, of the MRPs derived from 12 different amino acids and three reducing sugars were investigated. The MRPs of cysteine (Cys), cystine, arginine (Arg) and histidine (His) showed higher BIC compared to other amino acids. Lysine (Lys)-MRPs showed the highest absorbance value at 420 nm (A 420 ) but very limited BIC, whereas Cys-MRPs, showed the highest BIC and the lowest A 420 . The A 420 can roughly reflect the trend of BIC of MRPs from different amino acids, except Cys and Lys. MRPs from tyrosine (Tyr) showed the most potent antioxidant capacity but very limited BIC, whereas Cys-MRPs showed both higher antioxidant capacity and BIC compared to other amino acids. Partial least squares regression analysis showed positive and significant correlation between BIC and Fe 2+ reducing power of MRPs from 12 amino acids with glucose or fructose, except Lys, Cys and Tyr. The suitable pH for generating efficient browning inhibition compounds varies depending on different amino acids: acidic pH was favorable for Cys, whereas neutral and alkaline pH were suitable for His and Arg, respectively. Increasing both heating temperature and time over a certain range could improve the BIC of MRPs of Cys, His and Arg, whereas any further increase deteriorates their browning inhibition efficiencies. The types of amino acid, initial pH, temperature and time of the Maillard reaction were found to greatly influence the BIC and antioxidant capacity of the resulting MRPs. There is no clear relationship between BIC and the antioxidant capacity of MRPs when reactant type and processing parameters of the Maillard

  5. A compartmentalized out-of-equilibrium enzymatic reaction network for sustained autonomous movement

    NARCIS (Netherlands)

    Nijemeisland, M.; Abdelmohsen, L.K.E.A.; Huck, W.T.S.; Wilson, D.A.; van Hest, J.C.M.

    2016-01-01

    Every living cell is a compartmentalized out-ofequilibrium system exquisitely able to convert chemical energy into function. In order to maintain homeostasis, the flux of metabolites is tightly controlled by regulatory enzymatic networks. A crucial prerequisite for the development of lifelike

  6. Modeling and simulation of enzymatic gluconic acid production using immobilized enzyme and CSTR-PFTR circulation reaction system.

    Science.gov (United States)

    Li, Can; Lin, Jianqun; Gao, Ling; Lin, Huibin; Lin, Jianqiang

    2018-04-01

    Production of gluconic acid by using immobilized enzyme and continuous stirred tank reactor-plug flow tubular reactor (CSTR-PFTR) circulation reaction system. A production system is constructed for gluconic acid production, which consists of a continuous stirred tank reactor (CSTR) for pH control and liquid storage and a plug flow tubular reactor (PFTR) filled with immobilized glucose oxidase (GOD) for gluconic acid production. Mathematical model is developed for this production system and simulation is made for the enzymatic reaction process. The pH inhibition effect on GOD is modeled by using a bell-type curve. Gluconic acid can be efficiently produced by using the reaction system and the mathematical model developed for this system can simulate and predict the process well.

  7. THE KINETICS OF THE REACTIONS CATALYZED BY AN ENZYMATIC PREPARATION PRODUCED BY A BACILLUS LICHENIFORMIS STRAIN

    Directory of Open Access Journals (Sweden)

    MONICA DRAGOMIRESCU

    2007-05-01

    Full Text Available Robust immobilization techniques that preserve the activity of biomolecules have manypotential applications. In recent years, a number of new bioimobilisation methods in solgel-derived materials were reported. The interactions between the biomolecule and theinorganic material determine the degree to which the biomolecule retains its nativeproperties. The newer technological developments in the field of immobilizedbiocatalysts can offer the possibility of a wider and more economical exploitation ofbiocatalysts in biological applications, food and feed industry, medicine, and in thedevelopment of bioprocess monitoring devices, like the biosensors.The aim of this study was to obtain immobilized enzymatic preparations by methodswhich affect enzyme conformations and kinetic parameters as less as possible. Weimmobilized the enzymatic preparation with protease activity produced by a Bacilluslicheniformis B 40 local strain by physical bonding on ceramics and entrapment into solgel-derived glasses obtained from tetraethyl orthosilicate (TEOS, deposited in thin layeron a ceramic support (entrapment/deposition. Both physically adsorbed andentrapped/deposited enzymes follow Michaelis-Menten kinetics, similar with the solubleenzyme. In the case of immobilized enzymes, the apparent Michaelis constant, Km, wasgreater than that of the native one, as it was expected. The kinetic parameters indicatethat the enzymatic preparations adsorbed on ceramic support and entrapped/depositedshow less affinity for the substrate, Km being 1.3 and 2.1 times higher than that of thenative enzyme, respectively. The maximum velocity increased also by 3.5 and 7.9 timesrespectively, compared with the free counterpart (according to Lineweaver-Burklinearization.

  8. Enzymatic Synthesis and Structural Characterization of Theanderose through Transfructosylation Reaction Catalyzed by Levansucrase from Bacillus subtilis CECT 39.

    Science.gov (United States)

    Ruiz-Aceituno, Laura; Sanz, Maria Luz; de Las Rivas, Blanca; Muñoz, Rosario; Kolida, Sofia; Jimeno, Maria Luisa; Moreno, F Javier

    2017-12-06

    This work addresses the high-yield and fast enzymatic production of theanderose, a naturally occurring carbohydrate, also known as isomaltosucrose, whose chemical structure determined by NMR is α-d-glucopyranosyl-(1 → 6)-α-d-glucopyranosyl-(1 → 2)-β-d-fructofuranose. The ability of isomaltose to act as an acceptor in the Bacillus subtilis CECT 39 levansucrase-catalyzed transfructosylation reaction to efficiently produce theanderose in the presence of sucrose as a donor is described by using four different sucrose:isomaltose concentration ratios. The maximum theanderose concentration ranged from 122.4 to 130.4 g L -1 , was obtained after only 1 h and at a moderate temperature (37 °C), leading to high productivity (109.7-130.4 g L -1 h -1 ) and yield (up to 37.3%) values. The enzymatic synthesis was highly regiospecific, since no other detectable acceptor reaction products were formed. The development of efficient and cost-effective procedures for the biosynthesis of unexplored but appealing oligosaccharides as potential sweeteners, such as theanderose, could help to expand its potential applications which are currently limited by their low availability.

  9. High-yield production of pure tagatose from fructose by a three-step enzymatic cascade reaction.

    Science.gov (United States)

    Lee, Seon-Hwa; Hong, Seung-Hye; Kim, Kyoung-Rok; Oh, Deok-Kun

    2017-08-01

    To produce tagatose from fructose with a high conversion rate and to establish a high-yield purification method of tagatose from the reaction mixture. Fructose at 1 M (180 g l -1 ) was converted to 0.8 M (144 g l -1 ) tagatose by a three-step enzymatic cascade reaction, involving hexokinase, plus ATP, fructose-1,6-biphosphate aldolase, phytase, over 16 h with a productivity of 9 g l -1 h -1 . No byproducts were detected. Tagatose was recrystallized from ethanol to a purity of 99.9% and a yield of 96.3%. Overall, tagatose at 99.9% purity was obtained from fructose with a yield of 77%. This is the first biotechnological production of tagatose from fructose and the first application of solvent recrystallization for the purification of rare sugars.

  10. The role of phosphate in a multistep enzymatic reaction: reactions of the substrate and intermediate in pieces.

    Science.gov (United States)

    Kholodar, Svetlana A; Allen, C Leigh; Gulick, Andrew M; Murkin, Andrew S

    2015-02-25

    Several mechanistically unrelated enzymes utilize the binding energy of their substrate's nonreacting phosphoryl group to accelerate catalysis. Evidence for the involvement of the phosphodianion in transition state formation has come from reactions of the substrate in pieces, in which reaction of a truncated substrate lacking its phosphorylmethyl group is activated by inorganic phosphite. What has remained unknown until now is how the phosphodianion group influences the reaction energetics at different points along the reaction coordinate. 1-Deoxy-D-xylulose-5-phosphate (DXP) reductoisomerase (DXR), which catalyzes the isomerization of DXP to 2-C-methyl-D-erythrose 4-phosphate (MEsP) and subsequent NADPH-dependent reduction, presents a unique opportunity to address this concern. Previously, we have reported the effect of covalently linked phosphate on the energetics of DXP turnover. Through the use of chemically synthesized MEsP and its phosphate-truncated analogue, 2-C-methyl-D-glyceraldehyde, the current study revealed a loss of 6.1 kcal/mol of kinetic barrier stabilization upon truncation, of which 4.4 kcal/mol was regained in the presence of phosphite dianion. The activating effect of phosphite was accompanied by apparent tightening of its interactions within the active site at the intermediate stage of the reaction, suggesting a role of the phosphodianion in disfavoring intermediate release and in modulation of the on-enzyme isomerization equilibrium. The results of kinetic isotope effect and structural studies indicate rate limitation by physical steps when the covalent linkage is severed. These striking differences in the energetics of the natural reaction and the reactions in pieces provide a deeper insight into the contribution of enzyme-phosphodianion interactions to the reaction coordinate.

  11. Monoacylglycerol synthesis via enzymatic glycerolysis using a simple and efficient reaction system

    DEFF Research Database (Denmark)

    Yang, Tiankui; MORTEN, REBSDORF; ULRIK, ENGELRUD

    2005-01-01

    TL IM and Novozym 435 were employed in a batch reaction system. Novozym 435 showed better properties in glycerolysis. The increased temperature and high glycerol/oil ratio had little effect on the yield of MAGs in such a system. The reaction in a packed bed reactor (PBR) gave lower yield of MAGs...

  12. CONTINUOUS AND SEMICONTINUOUS REACTION SYSTEMS FOR HIGH-SOLIDS ENZYMATIC HYDROLYSIS OF LIGNOCELLULOSICS

    Directory of Open Access Journals (Sweden)

    A. González Quiroga

    2015-12-01

    Full Text Available Abstract An attractive operation strategy for the enzymatic hydrolysis of lignocellulosics results from dividing the process into three stages with complementary goals: continuous enzyme adsorption at low-solids loading (5% w/w with recycling of the liquid phase; continuous liquefaction at high-solids content (up to 20% w/w; and, finally, continuous or semicontinuous hydrolysis with supplementation of fresh enzymes. This paper presents a detailed modeling and simulation framework for the aforementioned operation strategies. The limiting micromixing situations of macrofluid and microfluid are used to predict conversions. The adsorption and liquefaction stages are modeled as a continuous stirred tank and a plug flow reactor, respectively. Two alternatives for the third stage are studied: a train of five cascading stirred tanks and a battery of batch reactors in parallel. Simulation results show that glucose concentrations greater than 100 g L-1 could be reached with both of the alternatives for the third stage.

  13. Reaction mechanisms and rate constants of waste degradation in landfill bioreactor systems with enzymatic-enhancement.

    Science.gov (United States)

    Jayasinghe, P A; Hettiaratchi, J P A; Mehrotra, A K; Kumar, S

    2014-06-01

    Augmenting leachate before recirculation with peroxidase enzymes is a novel method to increase the available carbon, and therefore the food supply to microorganisms at the declining phase of the anaerobic landfill bioreactor operation. In order to optimize the enzyme-catalyzed leachate recirculation process, it is necessary to identify the reaction mechanisms and determine rate constants. This paper presents a kinetic model developed to ascertain the reaction mechanisms and determine the rate constants for enzyme catalyzed anaerobic waste degradation. The maximum rate of reaction (Vmax) for MnP enzyme-catalyzed reactors was 0.076 g(TOC)/g(DS).day. The catalytic turnover number (k(cat)) of the MnP enzyme-catalyzed was 506.7 per day while the rate constant (k) of the un-catalyzed reaction was 0.012 per day. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. Self-powered gustation electronic skin for mimicking taste buds based on piezoelectric-enzymatic reaction coupling process

    Science.gov (United States)

    Zhao, Tianming; Fu, Yongming; He, Haoxuan; Dong, Chuanyi; Zhang, Linlin; Zeng, Hui; Xing, Lili; Xue, Xinyu

    2018-02-01

    A new self-powered wearable gustation electronic skin for mimicking taste buds has been realized based on enzyme-modified/ZnO nanowire arrays on patterned-electrode flexible substrate. The e-skin can actively taste beverages or fruits without any external electric power. Through the piezoelectric-enzymatic reaction coupling effect, the nanowires can harvest the mechanical energy of body movement and output piezoelectric signal. The piezoelectric output is significantly dependent on the concentration of target analyte. The response for detecting 2 × 10-2 M ascorbic acid (ascorbate acid oxidase@ZnO) is up to 171.747, and the selectivity is high. The response for detecting 50% alcohol (alcohol oxidase@ZnO) is up to 45.867. Our results provide a new research direction for the development of multifunctional e-skin and expand the study scope for self-powered bionic systems.

  15. Carbon dioxide/methanol conversion cycle based on cascade enzymatic reactions supported on superparamagnetic nanoparticles

    Directory of Open Access Journals (Sweden)

    CATERINA G.C. MARQUES NETTO

    2017-10-01

    Full Text Available ABSTRACT The conversion of carbon dioxide into important industrial feedstock is a subject of growing interest in modern society. A possible way to achieve this goal is by carrying out the CO2/methanol cascade reaction, allowing the recycle of CO2 using either chemical catalysts or enzymes. Efficient and selective reactions can be performed by enzymes; however, due to their low stability, immobilization protocols are required to improve their performance. The cascade reaction to reduce carbon dioxide into methanol has been explored by the authors, using, sequentially, alcohol dehydrogenase (ADH, formaldehyde dehydrogenase (FalDH, and formate dehydrogenase (FDH, powered by NAD+/NADH and glutamate dehydrogenase (GDH as the co-enzyme regenerating system. All the enzymes have been immobilized on functionalized magnetite nanoparticles, and their reactions investigated separately in order to establish the best performance conditions. Although the stepwise scheme led to only 2.3% yield of methanol per NADH; in a batch system under CO2 pressure, the combination of the four immobilized enzymes increased the methanol yield by 64 fold. The studies indicated a successful regeneration of NADH in situ, envisaging a real possibility of using immobilized enzymes to perform the cascade CO2-methanol reaction.

  16. Integrated microreactor for enzymatic reaction automation: An easy step toward the quality control of monoclonal antibodies.

    Science.gov (United States)

    Ladner, Yoann; Mas, Silvia; Coussot, Gaelle; Bartley, Killian; Montels, Jérôme; Morel, Jacques; Perrin, Catherine

    2017-12-15

    The main purpose of the present work is to provide a fully integrated miniaturized electrophoretic methodology in order to facilitate the quality control of monoclonal antibodies (mAbs). This methodology called D-PES, which stands for Diffusion-mediated Proteolysis combined with an Electrophoretic Separation, permits to perform subsequently mAb tryptic digestion and electrophoresis separation of proteolysis products in an automated manner. Tryptic digestion conditions were optimized regarding the influence of enzyme concentration and incubation time in order to achieve similar enzymatic digestion efficiency to that obtained with the classical methodology (off-line). Then, the optimization of electrophoretic separation conditions concerning the nature of background electrolyte (BGE), ionic strength and pH was realized. Successful and repeatable electrophoretic profiles of three mAbs digests (Trastuzumab, Infliximab and Tocilizumab), comparable to the off-line digestion profiles, were obtained demonstrating the feasibility and robustness of the proposed methodology. In summary, the use of the proposed and optimized in-line approach opens a new, fast and easy way for the quality control of mAbs. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Quantum chemical modeling of enzymatic reactions: the case of 4-oxalocrotonate tautomerase.

    Science.gov (United States)

    Sevastik, Robin; Himo, Fahmi

    2007-12-01

    The reaction mechanism of 4-oxalocrotonate tautomerase (4-OT) is studied using the density functional theory method B3LYP. This enzyme catalyzes the isomerisation of unconjugated alpha-keto acids to their conjugated isomers. Two different quantum chemical models of the active site are devised and the potential energy curves for the reaction are computed. The calculations support the proposed reaction mechanism in which Pro-1 acts as a base to shuttle a proton from the C3 to the C5 position of the substrate. The first step (proton transfer from C3 to proline) is shown to be the rate-limiting step. The energy of the charge-separated intermediate (protonated proline-deprotonated substrate) is calculated to be quite low, in accordance with measured pKa values. The results of the two models are used to evaluate the methodology employed in modeling enzyme active sites using quantum chemical cluster models.

  18. Intracellular Microreactors as Artificial Organelles to Conduct Multiple Enzymatic Reactions Simultaneously

    DEFF Research Database (Denmark)

    Gallardo, Maria Godoy; Labay, Cédric Pierre; Jansman, Michelle M. T.

    2017-01-01

    The creation of artificial organelles is a new paradigm in medical therapy that aims to substitute for missing cellular function by replenishing a specific cellular task. Artificial organelles tackle the challenge of mimicking metabolism, which is the set of chemical reactions that occur within a...

  19. Assessing the reaction conditions to mediate the milkfat-soybean oil enzymatic interesterification

    Directory of Open Access Journals (Sweden)

    Ariela Veloso de Paula

    Full Text Available Summary A food grade lipase from Rhizopus oryzae immobilized on a hybrid polysiloxane-polyvinyl alcohol matrix (SiO2-PVA was used as the biocatalyst to mediate the interesterification reactions of a blend containing 65% milkfat and 35% soybean oil. All the reactions occurred in an inert nitrogen atmosphere in cylindrical glass reactors (80 mL with 40 g of the milkfat-soybean oil blend. The influence of the following variables was evaluated: biocatalyst loading (250-1500 activity units per gram of blend, biocatalyst moisture content (5-20%, temperature (45-60 °C and incubation time (2-48 h. The reactions were monitored by determining the free fatty acid content, triacylglycerol (TAGs composition in carbon species, and the consistency of the interesterified (IE products. The reaction conditions were set based on the parameters that provided a high interesterification yield and good consistency of the final product within the ideal range (200 to 800 gf cm-2. Hence the best results were obtained using a biocatalyst loading of 500 U g-1 of blend with 10% moisture content at 45 °C for 4 h. Under these conditions the consistency of the interesterified product was 539.7 ± 38 gf cm-2. The results demonstrated the potential of the immobilized lipase to alter the TAGs profile of the milkfat-soybean oil blend, allowing for the production of structured lipids.

  20. Design of an embedded inverse-feedforward biomolecular tracking controller for enzymatic reaction processes

    OpenAIRE

    Foo, Mathias; Kim, Jongrae; Sawlekar, Rucha; Bates, Declan G.

    2017-01-01

    Feedback control is widely used in chemical engineering to improve the performance and robustness of chemical processes. Feedback controllers require a ‘subtractor’ that is able to compute the error between the process output and the reference signal. In the case of embedded biomolecular control circuits, subtractors designed using standard chemical reaction network theory can only realise one-sided subtraction, rendering standard controller design approaches inadequate. Here, we show how a b...

  1. Polymerase-endonuclease amplification reaction (PEAR for large-scale enzymatic production of antisense oligonucleotides.

    Directory of Open Access Journals (Sweden)

    Xiaolong Wang

    Full Text Available Antisense oligonucleotides targeting microRNAs or their mRNA targets prove to be powerful tools for molecular biology research and may eventually emerge as new therapeutic agents. Synthetic oligonucleotides are often contaminated with highly homologous failure sequences. Synthesis of a certain oligonucleotide is difficult to scale up because it requires expensive equipment, hazardous chemicals and a tedious purification process. Here we report a novel thermocyclic reaction, polymerase-endonuclease amplification reaction (PEAR, for the amplification of oligonucleotides. A target oligonucleotide and a tandem repeated antisense probe are subjected to repeated cycles of denaturing, annealing, elongation and cleaving, in which thermostable DNA polymerase elongation and strand slipping generate duplex tandem repeats, and thermostable endonuclease (PspGI cleavage releases monomeric duplex oligonucleotides. Each round of PEAR achieves over 100-fold amplification. The product can be used in one more round of PEAR directly, and the process can be further repeated. In addition to avoiding dangerous materials and improved product purity, this reaction is easy to scale up and amenable to full automation. PEAR has the potential to be a useful tool for large-scale production of antisense oligonucleotide drugs.

  2. Efficient one-pot enzymatic synthesis of alpha-(1 -> 4)-glucosidic disaccharides through a coupled reaction catalysed by Lactobacillus acidophilus NCFM maltose phosphorylase

    DEFF Research Database (Denmark)

    Nakai, Hiroyuki; Dilokpimol, Adiphol; Abou Hachem, Maher

    2010-01-01

    Lactobacillus acidophilus NCFM maltose phosphorylase (LaMalP) of glycoside hydrolase family 65 catalysed enzymatic synthesis of alpha-(1 -> 4)-glucostdic disacchandes from maltose and five monosacchandes in a coupled phosphorolysis/reverse phosphorolysis one-pot reaction Thus phosphorolysis...

  3. Development of an enzymatic microreactor based on microencapsulated laccase with off-line capillary electrophoresis for measurement of oxidation reactions.

    Science.gov (United States)

    Roman-Gusetu, Georgiana; Waldron, Karen C; Rochefort, Dominic

    2009-11-20

    Microencapsulation is used here as a new technique to immobilize enzymes in a microreactor coupled off-line to capillary electrophoresis (CE), allowing the determination of enzymatic reaction products. The redox enzyme laccase was encapsulated using the method of interfacial cross-linking of poly(ethyleneimine) (PEI). The 50 microm diameter capsules were slurry packed from a suspension into a capillary-sized reactor made easily and quickly from a short length of 530 microm diameter fused-silica tubing. The volume of the bed of laccase microcapsules in the microreactor was in the order of 1.1 microL through which 50 microL of the substrate o-phenylenediamine (OPD) was flowed. The oxidation product 2,3-diaminophenazine (DAP) and the remaining OPD were quantified by CE in a pH 2.5 phosphate buffer. Peak migration time reproducibility was in the order of 0.4% RSD and peak area reproducibility was less than 1.7% RSD within the same day. Using the OPD peak area calibration curve, a conversion efficiency of 48% was achieved for a 2-min oxidation reaction in the microreactor.

  4. Preparation of radioactive acetyl-l-carnitine by an enzymatic exchange reaction

    International Nuclear Information System (INIS)

    Emaus, R.; Bieber, L.L.

    1982-01-01

    A rapid method for the preparation of [1- 14 C]acetyl-L-carnitine is described. The method involves exchange of [1- 14 C]acetic acid into a pool of unlabeled acetyl-L-carnitine using the enzymes acetyl-CoA synthetase and carnitine acetyltransferase. After isotopic equilibrium is attained, radioactive acetylcarnitine is separated from the other reaction components by chromatography on Dowex 1 (C1 - ) anion exchange resin. One of the procedures used to verify the product [1- 14 C]acetyl-L-carnitine can be used to synthesize (3S)-[5- 14 C]citric acid

  5. Enzymatic synthesis of sorbitan esters using a low-boiling-point azeotrope as a reaction solvent.

    Science.gov (United States)

    Sarney, D B; Barnard, M J; Virto, M; Vulfson, E N

    1997-05-20

    Sorbitan esters were prepared by controlled dehydration of sorbitol followed by lipase-catalyzed esterification of the resulting "sorbitan." The reaction was carried out in azeotropic mixtures of tert-butanol/n-hexane. A partial phase diagram to determine the temperature required for the distillation of the azeotrope at a given ratio of the solvents was constructed. The effect of varying concentrations of the two solvents on the rate of esterification and the monoester/diester ratio of the final product was investigated in detail. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 351-356, 1997.

  6. Technical Report for a Study on the Mechanism and Control of Non-Enzymatic Browning Reaction in Gamma-Irradiated Food

    Energy Technology Data Exchange (ETDEWEB)

    Byun, Myung Woo; Lee, Ju Woon; Kim, Jae Hun

    2007-01-15

    Gamma irradiation leads to a non-enzymatic browning reaction (carbonyl -amine reaction) in an aqueous system similar to those induced in a heated one. This reaction may influence the changes of the color in irradiated foods. The intensity of the reaction was dependent on the type of the sugar, if the occurrence is by irradiation or by heating. There was a difference in the browning reaction between irradiation and heating. Although no browning was observed in the heated solution of the non-reducing sugar, the formation of colored products was observed in the irradiated sucrose-lysine solution. It could be explained on the basis that irradiation promotes the breakdown of the glycosidic linkages of the disaccharide, sucrose and the produce of a reducing power. The high molecular weight melanoidin (> MW 12,000-14,000 Da) was produced by gamma irradiation from the non-enzymatic browning reaction between glucose and glycine. The structure of melanoidin was similar to melanodin from heat processing. The results suggested that gamma-irradiation occurred the non-enzymatic browning reaction that is similar the reaction by heat processing. Non-enzymatic browning reaction during gamma-irradiation processing was greatly influenced by pH and medium of reaction system. The brown color development of irradiated sugar solutions with and without glycine is more increased in buffer system especially with alkaline pH than DDW. When food is irradiated, off-color such as browning can be produced due to the non-enzymatic browning reaction and it is influenced by other ions and/or pH of system. This suggests that the browning of irradiated food might be retarded by lowering the pH of the system. Gamma-irradiation produce the free radical and the radiolysis products of sugar and glycine and then they may be condensed to colored products during post-irradiation. However, when the food is irradiated in frozen state, the production of free radical and radiolysis product is inhibited and it

  7. Technical Report for a Study on the Mechanism and Control of Non-Enzymatic Browning Reaction in Gamma-Irradiated Food

    International Nuclear Information System (INIS)

    Byun, Myung Woo; Lee, Ju Woon; Kim, Jae Hun

    2007-01-01

    Gamma irradiation leads to a non-enzymatic browning reaction (carbonyl -amine reaction) in an aqueous system similar to those induced in a heated one. This reaction may influence the changes of the color in irradiated foods. The intensity of the reaction was dependent on the type of the sugar, if the occurrence is by irradiation or by heating. There was a difference in the browning reaction between irradiation and heating. Although no browning was observed in the heated solution of the non-reducing sugar, the formation of colored products was observed in the irradiated sucrose-lysine solution. It could be explained on the basis that irradiation promotes the breakdown of the glycosidic linkages of the disaccharide, sucrose and the produce of a reducing power. The high molecular weight melanoidin (> MW 12,000-14,000 Da) was produced by gamma irradiation from the non-enzymatic browning reaction between glucose and glycine. The structure of melanoidin was similar to melanodin from heat processing. The results suggested that gamma-irradiation occurred the non-enzymatic browning reaction that is similar the reaction by heat processing. Non-enzymatic browning reaction during gamma-irradiation processing was greatly influenced by pH and medium of reaction system. The brown color development of irradiated sugar solutions with and without glycine is more increased in buffer system especially with alkaline pH than DDW. When food is irradiated, off-color such as browning can be produced due to the non-enzymatic browning reaction and it is influenced by other ions and/or pH of system. This suggests that the browning of irradiated food might be retarded by lowering the pH of the system. Gamma-irradiation produce the free radical and the radiolysis products of sugar and glycine and then they may be condensed to colored products during post-irradiation. However, when the food is irradiated in frozen state, the production of free radical and radiolysis product is inhibited and it

  8. Using an enzymatic galactose assay to detect lactose glycation extents of two proteins caseinate and soybean protein isolate via the Maillard reaction.

    Science.gov (United States)

    Wang, Xiao-Peng; Zhao, Xin-Huai

    2017-06-01

    Glycation of food proteins via the Maillard reaction has been widely studied in the recent years; however, the amount of saccharide connected to proteins is usually not determined. An enzymatic galactose assay was proposed firstly in this study to detect lactose glycation extents of caseinate and soybean protein isolate (SPI) during the Maillard reaction at two temperatures and different times. The separated glycated proteins were hydrolysed to release galactose necessary for the enzymatic assay and glycation calculation. Caseinate and SPI both obtained the highest lactose glycation extents at 100 °C or 121 °C by a reaction time of 180 or 20 min. Short- and long-time reaction resulted in lower glycation extents. During the reaction, three chemical indices (absorbences at 294/490 nm and fluorescence intensities) of reaction mixtures increased continually, but another index reactable NH 2 of glycated proteins showed the opposite trend. In general, changing profiles of the four indices were inconsistent with those profiles of lactose glycation extents of glycated proteins, implying practical limitation of the four indices in studies. This proposed enzymatic assay could directly detect lactose glycation of the two proteins, and thus was more useful than the four chemical indices to monitor glycation of the two proteins. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  9. Product inhibition of enzymatic hydrolysis of cellulose: are we running the reactions all wrong?

    DEFF Research Database (Denmark)

    Meyer, Anne S.

    2012-01-01

    cellobiose and glucose. The reported KI for glucose on the T. reesei cellulases and -glucosidase varies from 0.04 to 5 g/L. The type of inhibition is debated, and probably varies for different -glucosidases, but with a required goal of sufficient glucose concentration to support ethanol concentrations....... This is because the currently used Trichoderma reesei derived cellulases, i.e. exoglucanases (mainly the cellobiohydrolases Cel7A and Cel6A), endo-1,4--glucanases, and now boosted with -glucosidase and other enzymes, now considered the “industry standard” enzymes, are significantly inhibited by the products...... of minimum ∼5–6% v/v, the glucose product concentrations exceed the critical limit for product inhibition. Hence, regardless of the recent progress in enzyme development for cellulose hydrolysis, the glucose product inhibition remains an issue, which is exacerbated as the reaction progresses, especially...

  10. Determination of SFC, FFA, and equivalent reaction time for enzymatically interestified oils using NIRS

    DEFF Research Database (Denmark)

    Houmøller, Lars P.; Kristensen, Dorthe; Rosager, Helle

    2007-01-01

    The use of near infrared spectroscopy (NIRS) for rapid determination of the degree of interesterification of blends of palm stearin, coconut oil, and rapeseed oil obtained using an immobilized Thermomyces lanuginosa lipase at 70 ◦C was investigated. Interesterification was carried out by applying...... that NIRS could be used to replace the traditional methods for determining FFA and SFC in vegetable oils.It was possible to monitor the activity of the immobilized enzyme for interesterification of margarine oils by predicting the equivalent reaction time in a batch reactor from NIR spectra. Root mean...... square errors of prediction for two different oil blends interesterified for 300 and 170 min were 21 and 12 min, respectively....

  11. Anaerobic Microbial Degradation of Hydrocarbons: From Enzymatic Reactions to the Environment.

    Science.gov (United States)

    Rabus, Ralf; Boll, Matthias; Heider, Johann; Meckenstock, Rainer U; Buckel, Wolfgang; Einsle, Oliver; Ermler, Ulrich; Golding, Bernard T; Gunsalus, Robert P; Kroneck, Peter M H; Krüger, Martin; Lueders, Tillmann; Martins, Berta M; Musat, Florin; Richnow, Hans H; Schink, Bernhard; Seifert, Jana; Szaleniec, Maciej; Treude, Tina; Ullmann, G Matthias; Vogt, Carsten; von Bergen, Martin; Wilkes, Heinz

    2016-01-01

    Hydrocarbons are abundant in anoxic environments and pose biochemical challenges to their anaerobic degradation by microorganisms. Within the framework of the Priority Program 1319, investigations funded by the Deutsche Forschungsgemeinschaft on the anaerobic microbial degradation of hydrocarbons ranged from isolation and enrichment of hitherto unknown hydrocarbon-degrading anaerobic microorganisms, discovery of novel reactions, detailed studies of enzyme mechanisms and structures to process-oriented in situ studies. Selected highlights from this program are collected in this synopsis, with more detailed information provided by theme-focused reviews of the special topic issue on 'Anaerobic biodegradation of hydrocarbons' [this issue, pp. 1-244]. The interdisciplinary character of the program, involving microbiologists, biochemists, organic chemists and environmental scientists, is best exemplified by the studies on alkyl-/arylalkylsuccinate synthases. Here, research topics ranged from in-depth mechanistic studies of archetypical toluene-activating benzylsuccinate synthase, substrate-specific phylogenetic clustering of alkyl-/arylalkylsuccinate synthases (toluene plus xylenes, p-cymene, p-cresol, 2-methylnaphthalene, n-alkanes), stereochemical and co-metabolic insights into n-alkane-activating (methylalkyl)succinate synthases to the discovery of bacterial groups previously unknown to possess alkyl-/arylalkylsuccinate synthases by means of functional gene markers and in situ field studies enabled by state-of-the-art stable isotope probing and fractionation approaches. Other topics are Mo-cofactor-dependent dehydrogenases performing O2-independent hydroxylation of hydrocarbons and alkyl side chains (ethylbenzene, p-cymene, cholesterol, n-hexadecane), degradation of p-alkylated benzoates and toluenes, glycyl radical-bearing 4-hydroxyphenylacetate decarboxylase, novel types of carboxylation reactions (for acetophenone, acetone, and potentially also benzene and

  12. A chemometric method to identify enzymatic reactions leading to the transition from glycolytic oscillations to waves

    Science.gov (United States)

    Zimányi, László; Khoroshyy, Petro; Mair, Thomas

    2010-06-01

    In the present work we demonstrate that FTIR-spectroscopy is a powerful tool for the time resolved and noninvasive measurement of multi-substrate/product interactions in complex metabolic networks as exemplified by the oscillating glycolysis in a yeast extract. Based on a spectral library constructed from the pure glycolytic intermediates, chemometric analysis of the complex spectra allowed us the identification of many of these intermediates. Singular value decomposition and multiple level wavelet decomposition were used to separate drifting substances from oscillating ones. This enabled us to identify slow and fast variables of glycolytic oscillations. Most importantly, we can attribute a qualitative change in the positive feedback regulation of the autocatalytic reaction to the transition from homogeneous oscillations to travelling waves. During the oscillatory phase the enzyme phosphofructokinase is mainly activated by its own product ADP, whereas the transition to waves is accompanied with a shift of the positive feedback from ADP to AMP. This indicates that the overall energetic state of the yeast extract determines the transition between spatially homogeneous oscillations and travelling waves.

  13. 26kDa endochitinase from barley seeds: real-time monitoring of the enzymatic reaction and substrate binding experiments using electrospray ionization mass spectrometry

    DEFF Research Database (Denmark)

    Dennhart, Nicole; Weigang, Linda M M; Fujiwara, Maho

    2009-01-01

    A 26 kDa endochitinase from barley seeds was enzymatically characterized exclusively by electrospray ionization mass spectrometry (ESI-MS). At first, oligosaccharide hydrolysis catalyzed by the barley chitinase was monitored in real-time by ESI-MS. The reaction time-course obtained by ESI......-MS monitoring was found to be consistent with the data obtained earlier by HPLC, and the quantitative profile was successfully simulated by kinetic modeling of the enzymatic hydrolysis. It is obvious that the real-time monitoring method by ESI-MS allows a faster and cheaper determination of the chitinase...... of the enzymatic activity in E67Q is definitely caused by a point mutation of Glu67 but not due to partial unfolding of the mutated enzyme. Finally, association constants of enzyme-oligosaccharide complexes were calculated from Scatchard plots obtained by mass spectra. The binding free energy values obtained for E...

  14. Internet Databases of the Properties, Enzymatic Reactions, and Metabolism of Small Molecules—Search Options and Applications in Food Science

    Directory of Open Access Journals (Sweden)

    Piotr Minkiewicz

    2016-12-01

    Full Text Available Internet databases of small molecules, their enzymatic reactions, and metabolism have emerged as useful tools in food science. Database searching is also introduced as part of chemistry or enzymology courses for food technology students. Such resources support the search for information about single compounds and facilitate the introduction of secondary analyses of large datasets. Information can be retrieved from databases by searching for the compound name or structure, annotating with the help of chemical codes or drawn using molecule editing software. Data mining options may be enhanced by navigating through a network of links and cross-links between databases. Exemplary databases reviewed in this article belong to two classes: tools concerning small molecules (including general and specialized databases annotating food components and tools annotating enzymes and metabolism. Some problems associated with database application are also discussed. Data summarized in computer databases may be used for calculation of daily intake of bioactive compounds, prediction of metabolism of food components, and their biological activity as well as for prediction of interactions between food component and drugs.

  15. Establishing MALDI-TOF as Versatile Drug Discovery Readout to Dissect the PTP1B Enzymatic Reaction.

    Science.gov (United States)

    Winter, Martin; Bretschneider, Tom; Kleiner, Carola; Ries, Robert; Hehn, Jörg P; Redemann, Norbert; Luippold, Andreas H; Bischoff, Daniel; Büttner, Frank H

    2018-07-01

    Label-free, mass spectrometric (MS) detection is an emerging technology in the field of drug discovery. Unbiased deciphering of enzymatic reactions is a proficient advantage over conventional label-based readouts suffering from compound interference and intricate generation of tailored signal mediators. Significant evolvements of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MS, as well as associated liquid handling instrumentation, triggered extensive efforts in the drug discovery community to integrate the comprehensive MS readout into the high-throughput screening (HTS) portfolio. Providing speed, sensitivity, and accuracy comparable to those of conventional, label-based readouts, combined with merits of MS-based technologies, such as label-free parallelized measurement of multiple physiological components, emphasizes the advantages of MALDI-TOF for HTS approaches. Here we describe the assay development for the identification of protein tyrosine phosphatase 1B (PTP1B) inhibitors. In the context of this precious drug target, MALDI-TOF was integrated into the HTS environment and cross-compared with the well-established AlphaScreen technology. We demonstrate robust and accurate IC 50 determination with high accordance to data generated by AlphaScreen. Additionally, a tailored MALDI-TOF assay was developed to monitor compound-dependent, irreversible modification of the active cysteine of PTP1B. Overall, the presented data proves the promising perspective for the integration of MALDI-TOF into drug discovery campaigns.

  16. Enzymatic Synthesis of Highly Fluorescent 8-Azapurine Ribosides Using a Purine Nucleoside Phosphorylase Reverse Reaction: Variable Ribosylation Sites

    Directory of Open Access Journals (Sweden)

    Goran Mikleušević

    2013-10-01

    Full Text Available Various forms of purine-nucleoside phosphorylase (PNP were used as catalysts of enzymatic ribosylation of selected fluorescent 8-azapurines. It was found that the recombinant calf PNP catalyzes ribosylation of 2,6-diamino-8-azapurine in a phosphate-free medium, with ribose-1-phosphate as ribose donor, but the ribosylation site is predominantly N7 and N8, with the proportion of N8/N7 ribosylated products markedly dependent on the reaction conditions. Both products are fluorescent. Application of the E. coli PNP gave a mixture of N8 and N9-substituted ribosides. Fluorescence of the ribosylated 2,6-diamino-8-azapurine has been briefly characterized. The highest quantum yield, ~0.9, was obtained for N9-β-d-riboside (λmax 365 nm, while for N8-β-d-riboside, emitting at ~430 nm, the fluorescence quantum yield was found to be close to 0.4. Ribosylation of 8-azaguanine with calf PNP as a catalyst goes exclusively to N9. By contrast, the E. coli PNP ribosylates 8-azaGua predominantly at N9, with minor, but highly fluorescent products ribosylated at N8/N7.

  17. Effect of Thermal Processing towards Lipid Oxidation and Non-enzymatic Browning Reactions of Antartic Krill (Euphausia superba) Meal.

    Science.gov (United States)

    Liu, Yanzi; Cong, Peixu; Li, Beijia; Song, Yu; Liu, Yanjun; Xu, Jie; Xue, Changhu

    2018-04-13

    Antarctic krill is a huge source of biomass and prospective high-quality lipid source. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), nutritionally important lipid components with poor oxidative stability, were used as markers of oxidation during thermal processing of Antarctic krill (Euphausia superba) meal by evaluating the lipolysis, lipid oxidation, and non-enzymatic browning reactions. Liquid chromatography-mass spectrometry of the phospholipids (PLs) and the main oxidation products of free fatty acids (FFAs) and phosphatidylcholine (PC) was effective for evaluating the oxidation of EPA and DHA. During boiling, oxidation of EPA and DHA in the FFA and PC fractions and hydrolysis of the fatty acids at the sn-2 position of the PLs were predominant. The changes in PC during drying were mainly attributed to the oxidation of EPA and DHA. Heat treatment increased the oxidation products and concentration of hydrophobic pyrrole owing to pyrrolization between phosphatidylethanolamine (PE) and the lipid oxidation products. The lipid oxidation level of Antarctic krill increased after drying, owing to prolonged heating under the severe conditions. This article is protected by copyright. All rights reserved.

  18. TEMPO/viologen electrochemical heterojunction for diffusion-controlled redox mediation: a highly rectifying bilayer-sandwiched device based on cross-reaction at the interface between dissimilar redox polymers.

    Science.gov (United States)

    Tokue, Hiroshi; Oyaizu, Kenichi; Sukegawa, Takashi; Nishide, Hiroyuki

    2014-03-26

    A couple of totally reversible redox-active molecules, which are different in redox potentials, 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) and viologen (V(2+)), were employed to give rise to a rectified redox conduction effect. Single-layer and bilayer devices were fabricated using polymers containing these sites as pendant groups per repeating unit. The devices were obtained by sandwiching the redox polymer layer(s) with indium tin oxide (ITO)/glass and Pt foil electrodes. Electrochemical measurements of the single-layer device composed of polynorbornene-bearing TEMPO (PTNB) exhibited a diffusion-limited current-voltage response based on the TEMPO(+)/TEMPO exchange reaction, which was almost equivalent to a redox gradient through the PTNB layer depending upon the thickness. The bilayer device gave rise to the current rectification because of the thermodynamically favored cross-reaction between TEMPO(+) and V(+) at the polymer/polymer interface. A current-voltage response obtained for the bilayer device demonstrated a two-step diffusion-limited current behavior as a result of the concurrent V(2+)/V(+) and V(+)/V(0) exchange reactions according to the voltage and suggested that the charge transport process through the device was most likely to be rate-determined by a redox gradient in the polymer layer. Current collection experiments revealed a charge transport balance throughout the device, as a result of the electrochemical stability and robustness of the polymers in both redox states.

  19. PENGARUH SORPSI AIR DAN SUHU TRANSISI GELAS TERHADAP LAJU PENCOKLATAN NON-ENZIMATIS PADA PANGAN MODEL [The Effect of Water Sorption and Glass Transition Temperature on Non-Enzymatic Browning Reaction of Food Models

    Directory of Open Access Journals (Sweden)

    Dede R Adawiyah1

    2005-12-01

    Full Text Available This research was aimer/ to study the extend of non enzymatic browning reaction in food models containing the mixture of tapioca starch, casein, sucrose and oh at different moisture contents (2.55%, 5.26%, 7.54%, 15.20%. 15.93% and 23.99% and storage temperatures (30, 55 and 700C. The non-enzymatic browning reaction was detected from brown color intensity measured by spechtrophotometer and colorimetric methods. The non-enzymatic browning reaction or food model follow pseudo-zero order reaction, suggesting that browning reaction occurred at moisture content above monolayer zone. T-Tg (T storage - Tg prediction and reaction rate constant (k plots showed that browning reaction occurred at temperature around glass transition and increased significantly at 150 above Tg of casein. Tapioca starch in the food model was under glassy condition. The mobility of substrate increased and diffused at amorphous matrix.

  20. Enzymatic conversion of sucrose to glucose and its anomerization by quantitative NMR spectroscopy: Application of a simple consecutive reaction rates approach

    Science.gov (United States)

    Singh, Jaideep; Her, Cheenou; Krishnan, V. V.

    2018-02-01

    The anomerization of carbohydrates is an essential process that determines the relative stabilization of stereoisomers in an aqueous solution. In a typical real-time enzyme kinetics experiment, the substrate (sucrose) is converted to glucose and fructose by the enzyme invertase. The product (α-D-glucose) starts to convert to β-D-glucose immediately by hydrolysis. Though the anomerization process is independent of the enzyme catalysis, the progress curve describing the production of β-D-glucose from α-D-glucose is directly affected by the kinetics of consecutive reactions. When α-D-glucose is continually converted to β-D-glucose, by the enzymatic action, the time course of both α- and β-D-glucose is influenced by the enzyme kinetics. Thus, a reversible first-order rate equation is not adequate to model the reaction mechanism, leading to erroneous results on the rates of formation of the glucose anomers. In this manuscript, we incorporate an approximate method to address consecutive general reactions involving enzyme kinetics and first-order reaction processes. The utility of the approach is demonstrated in the real-time NMR measurement of the anomerization process of α-D-glucose (enzymatically produced from sucrose) to β-D-glucose, as a function of invertase enzyme concentration. Variable temperature experiments were used to estimate the thermodynamic parameters of the anomerization process and are consistent with literature values.

  1. Diffusion-controlled reactions modeling in Geant4-DNA

    Czech Academy of Sciences Publication Activity Database

    Karamitros, M.; Luan, S.; Bernal, M. A.; Allison, J.; Baldacchino, G.; Davídková, Marie; Francis, Z.; Friedland, W.; Ivanchenko, A.; Ivanchenko, V.; Mantero, A.; Nieminen, P.; Santin, G.; Tran, H. N.; Stepan, V.; Incerti, S.

    2014-01-01

    Roč. 274, OCT (2014), s. 841-882 ISSN 0021-9991 Institutional support: RVO:61389005 Keywords : chemical kinetics simulation * radiation chemistry * Fokker-Planck equation * Smoluchowski diffusion equation * Brownian bridge * dynamical time steps * k-d tree * radiolysis * radiobiology * Geant4-DNA * Brownian dynamics Subject RIV: BO - Biophysics Impact factor: 2.434, year: 2014

  2. Synthesis and spectral characterization of 2,2-diphenylethyl glucosinolate and HPLC-based reaction progress curve data for the enzymatic hydrolysis of glucosinolates by Sinapis alba myrosinase

    Directory of Open Access Journals (Sweden)

    Chase A. Klingaman

    2017-02-01

    Full Text Available The data presented in this article are related to the research article, “HPLC-based enzyme kinetics assay for glucosinolate hydrolysis facilitate analysis of systems with both multiple reaction products and thermal enzyme denaturation” (C.K. Klingaman, M.J. Wagner, J.R. Brown, J.B. Klecker, E.H. Pauley, C.J. Noldner, J.R. Mays, [1]. This data article describes (1 the synthesis and spectral characterization data of a non-natural glucosinolate analogue, 2,2-diphenylethyl glucosinolate, (2 HPLC standardization data for glucosinolate, isothiocyanate, nitrile, and amine analytes, (3 reaction progress curve data for enzymatic hydrolysis reactions with variable substrate concentration, enzyme concentration, buffer pH, and temperature, and (4 normalized initial velocities of hydrolysis/formation for analytes. These data provide a comprehensive description of the enzyme-catalyzed hydrolysis of 2,2-diphenylethyl glucosinolate (5 and glucotropaeolin (6 under widely varied conditions.

  3. Non-Enzymatic-Browning-Reaction: A Versatile Route for Production of Nitrogen-Doped Carbon Dots with Tunable Multicolor Luminescent Display

    Science.gov (United States)

    Wei, Weili; Xu, Can; Wu, Li; Wang, Jiasi; Ren, Jinsong; Qu, Xiaogang

    2014-01-01

    The non-enzymatic browning, namely Maillard reaction is commonly invoked to account for abiotic chemical transformations of organic matter. Here we report a new reaction pathway via the Maillard reaction to systematically synthesize a series of nitrogen-doped carbon dots (C-dots) with superhigh quantum yield (QY) and tunable multicolor luminescent displayment. The starting materials are glucose and the serial amino acid analogues which allow systemically controlling luminescent and physicochemical properties of C-dots at will. Unexpectedly, the as-prepared C-dots possess bright photoluminescence with QY up to 69.1% which is almost the highest ever reported, favorable biocompatibility, excellent aqueous and nonaqueous dispersibility, ultrahigh photostability, and readily functionalization. We have demonstrated that they are particularly suitable for multicolor luminescent display and long-term and real-time cellular imaging. Furthermore, the methodology is readily scalable to large yield, and can provide sufficient amount of C-dots for practical demands.

  4. Accelerated diffusion controlled creep of polycrystalline materials. Communication 1. Model of diffusion controlled creep acceleration

    International Nuclear Information System (INIS)

    Smirnova, E.S.; Chuvil'deev, V.N.

    1998-01-01

    The model is suggested which describes the influence of large-angle grain boundary migration on a diffusion controlled creep rate in polycrystalline materials (Coble creep). The model is based on the concept about changing the value of migrating boundary free volume when introducing dislocations distributed over the grain bulk into this boundary. Expressions are obtained to calculate the grain boundary diffusion coefficient under conditions of boundary migration and the parameter, which characterized the value of Coble creep acceleration. A comparison is made between calculated and experimental data for Cd, Co and Fe

  5. Aza‐Michael addition reaction: Post‐polymerization modification and preparation of PEI/PEG‐based polyester hydrogels from enzymatically synthesized reactive polymers

    DEFF Research Database (Denmark)

    Hoffmann, Christian; Stuparu, Mihaiela C.; Daugaard, Anders Egede

    2015-01-01

    The utility of aza‐Michael addition chemistry for post‐polymerization functionalization of enzymatically prepared polyesters is established. For this, itaconate ester and oligoethylene glycol are selected as monomers. A Candida Antarctica lipase B catalyzed polycondensation reaction between the two...... monomers provides the polyesters, which carry an activated carbon‐carbon double bond in the polymer backbone. These electron deficient alkenes represent suitable aza‐Michael acceptors and can be engaged in a nucleophilic addition reaction with small molecular mono‐amines (aza‐Michael donors) to yield...... functionalized linear polyesters. Employing a poly‐amine as the aza‐Michael donor, on the other hand, results in the formation of hydrophilic polymer networks....

  6. Anticancer system created by acrolein and hydroxyl radical generated in enzymatic oxidation of spermine and other biochemical reactions.

    Science.gov (United States)

    Alarcon, R A

    2012-10-01

    A hypothesis suggesting the existence of a ubiquitous physiological anticancer system created by two highly reactive oxidative stress inducers with anticancer properties, acrolein and hydroxyl radical, is reported in this communication. Both components can originate separately or together in several biochemical interactions, among them, the enzymatic oxidation of the polyamine spermine, which appear to be their main source. The foundations of this hypothesis encompass our initial search for growth-inhibitors or anticancer compounds in biological material leading to the isolation of spermine, a polyamine that became highly cytotoxic through the generation of acrolein, when enzymatically oxidized. Findings complemented with pertinent literature data by other workers and observed anticancer activities by sources capable of producing acrolein and hydroxyl radical. This hypothesis obvious implication: spermine enzymatic oxidations or other biochemical interactions that would co-generate acrolein and hydroxyl radical, the anticancer system components, should be tried as treatments for any given cancer. The biochemical generation of acrolein observed was totally unexpected, since this aldehyde was known; as a very toxic and highly reactive xenobiotic chemical produced in the pyrolysis of fats and other organic material, found as an atmospheric pollutant, in tobacco smoke and car emissions, and mainly used as a pesticide or aquatic herbicide. Numerous studies on acrolein, considered after our work a biological product, as well, followed. In them, acrolein widespread presence, its effects on diverse cellular proteins, such as, growth factors, and its anticancer activities, were additionally reported. Regarding hydroxyl radical, the second component of the proposed anticancer system, and another cytotoxic product in normal cell metabolism, it co-generates with acrolein in several biochemical interactions, occurrences suggesting that these products might jointly fulfill some

  7. ENCAPSULATION OF HORSERADISH PEROXIDASE-GLUCOSE OXIDASE (HRP-GOx IN SILICA AQUAGEL SYNTHESIZED FROM RICE HULL ASH FOR ENZYMATIC REACTION OF GLUCOSE

    Directory of Open Access Journals (Sweden)

    Nuryono Nuryono

    2010-06-01

    Full Text Available In recent years, the sol-gel technique has attracted increasing interest as a unique approach to immobilize biomolecules for bioanalytical applications as well as biochemical and biophysical studies. In this research, encapsulation of Horseradish peroxidase-Glucose oxidase (HRP-GOx enzymes in silica aquagel from rice hull ash by sol-gel process has been carried out. In addition, the effect of several parameters (weight ratio of HRP to GOx, pH, temperature, sodium ion concentration on enzyme activity was studied, as well. Rice hull ash, which was produced by ashing at 700 °C, was extracted it's silika by NaOH solution 1 M at 100 °C for two hours to produce sodium silikate (Na2SiO3 solution. The Na2SiO3 solution with pH of 13 was added with a strong cation exchanger resin, to produce sol solution with the pH of 4. Encapsulation was emphasized by mixing sol solution and phosphate buffer pH 7 containing HRP-GOx solution at volume ratio of buffer to sol solution 1:5. The mixture was transferred into 96-microwell plate and was aged for 24 hours. Enzymatic reaction was carried out by adding chromogenic solution of phenol and 4-aminoantipyrine (4-AAP and b-D-glucose solution (as substrate into the microwell. Enzymatic activity was examined by measuring absorbance of product solution at 490 nm with ELISA reader. Result of enzymatic activity for encapsulated enzymes (SGE was compared to that for free enzymes (EB. Results showed that at the investigated condition, HRP-GOx enzymes gave high activity at weight ratio of HRP to GOx 10:1 and pH 7 for both SGE and EB. Encapsulation caused the enzymes activity decrease to 53.0±0.2 %. However, SGE was observed to be more stable on pH and temperature changes than EB. Study on the effect of sodium concentration showed that the increase of sodium concentration from 0.10 to 0.37 M decreased the enzymatic activity to 56±0.2%. Reusability test showed that the synthesized SGE was reusable with activity decrease of 60

  8. Bimolecular interaction of argpyrimidine (a Maillard reaction product) in in vitro non-enzymatic protein glycation model and its potential role as an antiglycating agent.

    Science.gov (United States)

    Bhattacherjee, Abhishek; Dhara, Kaliprasanna; Chakraborti, Abhay Sankar

    2017-09-01

    Non- enzymatic glycation, also known as Maillard reaction, is one of the most important and investigated reactions in biochemistry. Maillard reaction products (MRPs) like protein-derived advanced glycation end products (AGEs) are often referred to cause pathophysiological complications in human systems. On contrary, several MRPs are exogenously used as antioxidant, antimicrobial and flavouring agents. In the preset study, we have shown that argpyrimidine, a well-established AGE, interacts with bovine serum albumin (BSA) and glucose individually in standard BSA-glucose model system and successfully inhibits glycation of the protein. Bimolecular interaction of argpyrimidine with glucose or BSA has been studied independently. Chromatographic purification, different spectroscopic studies and molecular modeling have been used to evaluate the nature and pattern of interactions. Binding of argpyrimidine with BSA prevents incorporation of glucose inside the native protein. Argpyrimidine can also directly entrap glucose. Both these interactions may be associated with the antiglycation potential of argpyrimidine, indicating a beneficial function of an AGE. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Biomimicry Promotes the Efficiency of a 10-Step Sequential Enzymatic Reaction on Nanoparticles, Converting Glucose to Lactate.

    Science.gov (United States)

    Mukai, Chinatsu; Gao, Lizeng; Nelson, Jacquelyn L; Lata, James P; Cohen, Roy; Wu, Lauren; Hinchman, Meleana M; Bergkvist, Magnus; Sherwood, Robert W; Zhang, Sheng; Travis, Alexander J

    2017-01-02

    For nanobiotechnology to achieve its potential, complex organic-inorganic systems must grow to utilize the sequential functions of multiple biological components. Critical challenges exist: immobilizing enzymes can block substrate-binding sites or prohibit conformational changes, substrate composition can interfere with activity, and multistep reactions risk diffusion of intermediates. As a result, the most complex tethered reaction reported involves only 3 enzymes. Inspired by the oriented immobilization of glycolytic enzymes on the fibrous sheath of mammalian sperm, here we show a complex reaction of 10 enzymes tethered to nanoparticles. Although individual enzyme efficiency was higher in solution, the efficacy of the 10-step pathway measured by conversion of glucose to lactate was significantly higher when tethered. To our knowledge, this is the most complex organic-inorganic system described, and it shows that tethered, multi-step biological pathways can be reconstituted in hybrid systems to carry out functions such as energy production or delivery of molecular cargo. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Optimization of reaction conditions for enzymatic viscosity reduction and hydrolysis of wheat arabinoxylan in an industrial ethanol fermentation residue

    DEFF Research Database (Denmark)

    Sørensen, H.R.; Pedersen, S.; Meyer, Anne Boye Strunge

    2006-01-01

    with a 50:50 mixture of an enzyme preparation from Humicola insolens, Ultraflo L, and a cellulolytic enzyme preparation from Trichoderma reesei, Celluclast 1.5 L. This enzyme mixture was previously shown to exhibit a synergistic action on arabinoxylan degradation. The viscosity of vinasse decreased...... of enzyme-catalyzed hydrolysis of arabinoxylan, beta-glucan, and cellulose. In designed response surface experiments, the optimal enzyme reaction conditions with respect to pH and temperature of the vinasse, the vinasse supernatant (mainly soluble material), and the vinasse sediment (mainly insoluble...

  11. Hairpin stabilized fluorescent silver nanoclusters for quantitative detection of NAD+ and monitoring NAD+/NADH based enzymatic reactions.

    Science.gov (United States)

    Jain, Priyamvada; Chakma, Babina; Patra, Sanjukta; Goswami, Pranab

    2017-03-01

    A set of 90 mer long ssDNA candidates, with different degrees of cytosine (C-levels) (% and clusters) was analyzed for their function as suitable Ag-nanocluster (AgNC) nucleation scaffolds. The sequence (P4) with highest C-level (42.2%) emerged as the only candidate supporting the nucleation process as evident from its intense fluorescence peak at λ 660 nm . Shorter DNA subsets derived from P4 with only stable hairpin structures could support the AgNC formation. The secondary hairpin structures were confirmed by PAGE, and CD studies. The number of base pairs in the stem region also contributes to the stability of the hairpins. A shorter 29 mer sequence (Sub 3) (ΔG = -1.3 kcal/mol) with 3-bp in the stem of a 7-mer loop conferred highly stable AgNC. NAD + strongly quenched the fluorescence of Sub 3-AgNC in a concentration dependent manner. Time resolved photoluminescence studies revealed the quenching involves a combined static and dynamic interaction where the binding constant and number of binding sites for NAD + were 0.201 L mol -1 and 3.6, respectively. A dynamic NAD + detection range of 50-500 μM with a limit of detection of 22.3 μM was discerned. The NAD + mediated quenching of AgNC was not interfered by NADH, NADP + , monovalent and divalent ions, or serum samples. The method was also used to follow alcohol dehydrogenase and lactate dehydrogenase catalyzed physiological reactions in a turn-on and turn-off assay, respectively. The proposed method with ssDNA-AgNC could therefore be extended to monitor other NAD + /NADH based enzyme catalyzed reactions in a turn-on/turn-off approach. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Noncanonical substrate preference of lambda exonuclease for 5'-nonphosphate-ended dsDNA and a mismatch-induced acceleration effect on the enzymatic reaction.

    Science.gov (United States)

    Wu, Tongbo; Yang, Yufei; Chen, Wei; Wang, Jiayu; Yang, Ziyu; Wang, Shenlin; Xiao, Xianjin; Li, Mengyuan; Zhao, Meiping

    2018-04-06

    Lambda exonuclease (λ exo) plays an important role in the resection of DNA ends for DNA repair. Currently, it is also a widely used enzymatic tool in genetic engineering, DNA-binding protein mapping, nanopore sequencing and biosensing. Herein, we disclose two noncanonical properties of this enzyme and suggest a previously undescribed hydrophobic interaction model between λ exo and DNA substrates. We demonstrate that the length of the free portion of the substrate strand in the dsDNA plays an essential role in the initiation of digestion reactions by λ exo. A dsDNA with a 5' non-phosphorylated, two-nucleotide-protruding end can be digested by λ exo with very high efficiency. Moreover, we show that when a conjugated structure is covalently attached to an internal base of the dsDNA, the presence of a single mismatched base pair at the 5' side of the modified base may significantly accelerate the process of digestion by λ exo. A detailed comparison study revealed additional π-π stacking interactions between the attached label and the amino acid residues of the enzyme. These new findings not only broaden our knowledge of the enzyme but will also be very useful for research on DNA repair and in vitro processing of nucleic acids.

  13. Noncanonical substrate preference of lambda exonuclease for 5′-nonphosphate-ended dsDNA and a mismatch-induced acceleration effect on the enzymatic reaction

    Science.gov (United States)

    Yang, Yufei; Chen, Wei; Wang, Jiayu; Yang, Ziyu; Wang, Shenlin; Xiao, Xianjin; Li, Mengyuan

    2018-01-01

    Abstract Lambda exonuclease (λ exo) plays an important role in the resection of DNA ends for DNA repair. Currently, it is also a widely used enzymatic tool in genetic engineering, DNA-binding protein mapping, nanopore sequencing and biosensing. Herein, we disclose two noncanonical properties of this enzyme and suggest a previously undescribed hydrophobic interaction model between λ exo and DNA substrates. We demonstrate that the length of the free portion of the substrate strand in the dsDNA plays an essential role in the initiation of digestion reactions by λ exo. A dsDNA with a 5′ non-phosphorylated, two-nucleotide-protruding end can be digested by λ exo with very high efficiency. Moreover, we show that when a conjugated structure is covalently attached to an internal base of the dsDNA, the presence of a single mismatched base pair at the 5′ side of the modified base may significantly accelerate the process of digestion by λ exo. A detailed comparison study revealed additional π–π stacking interactions between the attached label and the amino acid residues of the enzyme. These new findings not only broaden our knowledge of the enzyme but will also be very useful for research on DNA repair and in vitro processing of nucleic acids. PMID:29490081

  14. Label-free and sensitive detection of T4 polynucleotide kinase activity via coupling DNA strand displacement reaction with enzymatic-aided amplification.

    Science.gov (United States)

    Cheng, Rui; Tao, Mangjuan; Shi, Zhilu; Zhang, Xiafei; Jin, Yan; Li, Baoxin

    2015-11-15

    Several fluorescence signal amplification strategies have been developed for sensitive detection of T4 polynucleotide kinase (T4 PNK) activity, but they need fluorescence dye labeled DNA probe. We have addressed the limitation and report here a label-free strategy for sensitive detection of PNK activity by coupling DNA strand displacement reaction with enzymatic-aided amplification. A hairpin oligonucleotide (hpDNA) with blunt ends was used as the substrate for T4 PNK phosphorylation. In the presence of T4 PNK, the stem of hpDNA was phosphorylated and further degraded by lambda exonuclease (λ exo) from 5' to 3' direction to release a single-stranded DNA as a trigger of DNA strand displacement reaction (SDR). The trigger DNA can continuously displace DNA P2 from P1/P2 hybrid with the help of specific cleavage of nicking endonuclease (Nt.BbvCI). Then, DNA P2 can form G-quadruplex in the presence of potassium ions and quadruplex-selective fluorphore, N-methyl mesoporphyrin IX (NMM), resulting in a significant increase in fluorescence intensity of NMM. Thus, the accumulative release of DNA P2 led to fluorescence signal amplification for determining T4 PNK activity with a detection limit of 6.6×10(-4) U/mL, which is superior or comparative with established approaches. By ingeniously utilizing T4 PNK-triggered DNA SDR, T4 PNK activity can be specifically and facilely studied in homogeneous solution containing complex matrix without any external fluorescence labeling. Moreover, the influence of different inhibitors on the T4 PNK activity revealed that it also can be explored to screen T4 PNK inhibitors. Therefore, this label-free amplification strategy presents a facile and cost-effective approach for nucleic acid phosphorylation related research. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Organic influences on inorganic patterns of diffusion-controlled precipitation in gels

    Science.gov (United States)

    Barge, Laura M.; Nealson, Kenneth H.; Petruska, John

    2010-06-01

    The well-known AgNO 3/K 2CrO 4 reaction-diffusion system produces periodic bands of silver chromate precipitate in gelatin, but only randomly oriented crystals in agarose gel. We show that comparable bands can be produced in agarose gel by adding small amounts of simple organic acids (e.g., acetic acid, N-acetyl glycine, and N-acetyl alanine) that suppress crystal growth and promote formation of rounded particles of precipitate. These results indicate that α-carboxyl groups of amino acids or short peptides in gelatin under mildly acidic conditions can induce periodic band patterns in diffusion-controlled silver chromate precipitates.

  16. Enzymatic reactions in reversed micelles

    NARCIS (Netherlands)

    Hilhorst, M.H.

    1984-01-01

    It has been recognised that enzymes in reversed micelles have potential for application in chemical synthesis. Before these expectations will be realised many problems must be overcome. This thesis deals with some of them.
    In Chapter 1 the present knowledge about reversed micelles and

  17. Enzymatic Synthesis of Psilocybin.

    Science.gov (United States)

    Fricke, Janis; Blei, Felix; Hoffmeister, Dirk

    2017-09-25

    Psilocybin is the psychotropic tryptamine-derived natural product of Psilocybe carpophores, the so-called "magic mushrooms". Although its structure has been known for 60 years, the enzymatic basis of its biosynthesis has remained obscure. We characterized four psilocybin biosynthesis enzymes, namely i) PsiD, which represents a new class of fungal l-tryptophan decarboxylases, ii) PsiK, which catalyzes the phosphotransfer step, iii) the methyltransferase PsiM, catalyzing iterative N-methyl transfer as the terminal biosynthetic step, and iv) PsiH, a monooxygenase. In a combined PsiD/PsiK/PsiM reaction, psilocybin was synthesized enzymatically in a step-economic route from 4-hydroxy-l-tryptophan. Given the renewed pharmaceutical interest in psilocybin, our results may lay the foundation for its biotechnological production. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Predictability of solute transport in diffusion-controlled hydrogeologic regimes

    International Nuclear Information System (INIS)

    Gillham, R.W.; Cherry, J.A.

    1983-01-01

    Hydrogeologic regimes that are favourable for the subsurface management of low-level radioactive wastes must have transport properties that will limit the migration velocity of contaminants to some acceptably low value. Of equal importance, for the purpose of impact assessment and licensing, is the need to be able to predict, with a reasonable degree of certainty and over long time periods, what the migration velocity of the various contaminants of interest will be. This paper presents arguments to show that in addition to having favourable velocity characteristics, transport in saturated, diffusion-controlled hydrogeologic regimes is considerably more predictable than in the most common alternatives. The classical transport models for unsaturated, saturated-advection-controlled and saturated-diffusion-controlled environments are compared, with particular consideration being given to the difficulties associated with the characterization of the respective transport parameters. Results are presented which show that the diffusion of non-reactive solutes and solutes that react according to a constant partitioning ratio (K/sub d/) are highly predictable under laboratory conditions and that the diffusion coefficients for the reactive solutes can be determined with a reasonable degree of accuracy from independent measurements of bulk density, porosity, distribution coefficient and tortuosity. Field evidence is presented which shows that the distribution of environmental isotopes and chloride in thick clayey deposits is consistent with a diffusion-type transport process in these media. These results are particularly important in that they not only demonstrate the occurrence of diffusion-controlled hydrogeologic regimes, but they also demonstrate the predictability of the migration characteristics over very long time periods

  19. Influence of enzymatic reactions on the electrochemical behavior of EN X2CrNiMo17-11-2 (AISI 316L) stainless steel in bio-corrosion: role of interfacial processes on the modification of the passive layer

    International Nuclear Information System (INIS)

    Landoulsi, J.

    2008-01-01

    The outstanding corrosion behavior of stainless steels (SS) results from the presence of thin oxide layer (some nanometers). In non sterile aqueous media, stainless steels may exhibit a non stable behavior resulting from interactions between microbial species and passive film. In fact, microorganisms can be deeply involved in the corrosion processes usually reported as Microbial Influenced Corrosion (MIC). They can induce the initiation or the acceleration of this phenomenon and they do so when organized in bio-films. From the electrochemical point of view, stainless steels showed an increase of the free corrosion potential (Ecorr) attributed to the bio-film settlement. The Eco' ennoblement was broadly reported in seawater and seems to be confirmed in fresh water according to recent findings. A considerable progress in the comprehension of MIC processes was related to the role of extracellular species, essentially enzymes. Many enzymatic reactions occurring in bio-films consist on using oxygen as electron acceptor to generate hydrogen peroxide and related species. The aim of this work is to understand the mechanisms involved in the electrochemical behavior of stainless steel according to an enzymatic approach in medium simulating fresh water. To this end, glucose oxidase was chosen to globalize aerobic activities of bio-films. Electrochemical measurements in situ and surface analysis allow the comprehension of the role and the nature of interfacial processes. Surface characterization was performed with the help of a new quantitative utilization of XPS analysis and AFM. Results show a significant evolution in term of morphology (surface organization), (ii) chemical composition (passive layer, adsorbed organic species) and (iii) chemical reaction (oxidation, dissolution, effect of enzyme). Finally, a new enzymatic system is proposed to mimic specific physicochemical conditions at the SS / bio-film interface, in particular enzymatic generation of oxidant species in

  20. Implantation of algorithms of diffuse control in DSPS

    International Nuclear Information System (INIS)

    Perez C, B.

    2003-01-01

    In this thesis work there are presented: a) The characteristics and main components used in an electronic system based on a Dsp guided to control applications of processes, b) The description of an algorithm of diffuse control whose objective is the regulation of neutron power in a model of the punctual kinetics of a nuclear research reactor type TRIGA, and c) The installation in language assembler and execution in real time of the control algorithm in the system based on a Dsp. With regard to the installation and execution of the algorithm, the reaches of the project have been delimited to the following: a) Readiness of the entrance values to the controller in specific registrations of the system Dsp, b) Conversion of the entrances to the numerical formats with those that one obtains the best acting in the control algorithm, c) Execution of the algorithm until the obtaining of the value of the controller's exit, and d) Placement of the result in specific registrations of the Dsp for their later reading for an external parallel interface. It is necessary to mention that the simulation of the punctual kinetics of a reactor type TRIGA in the Pc and its integration with the control system based on the one Dsp is had contemplated as continuation of this work and that one of those will constitute main activities in my project of master thesis. A brief description of the topics presented in this thesis is given next. In the chapter one it is presented a general description of the diffuse logic and some of their applications in the industry. The main characteristics of a Dsp are also presented that they make it different from a micro controller or a microprocessor of general purpose. In the chapter 2 details of the internal architecture of the Dsp TMS320CS0 of Texas Instruments that are not explained with detail in the manual of user of the same one. This chapter has as objective to understand the internal hardware of the Dsp that is used for to carry out the program in

  1. Axisymmetric vortex method for low-Mach number, diffusion-controlled combustion

    CERN Document Server

    Lakkis, I

    2003-01-01

    A grid-free, Lagrangian method for the accurate simulation of low-Mach number, variable-density, diffusion-controlled reacting flow is presented. A fast-chemistry model in which the conversion rate of reactants to products is limited by the local mixing rate is assumed in order to reduce the combustion problem to the solution of a convection-diffusion-generation equation with volumetric expansion and vorticity generation at the reaction fronts. The solutions of the continuity and vorticity equations, and the equations governing the transport of species and energy, are obtained using a formulation in which particles transport conserved quantities by convection and diffusion. The dynamic impact of exothermic combustion is captured through accurate integration of source terms in the vorticity transport equations at the location of the particles, and the extra velocity field associated with volumetric expansion at low Mach number computed to enforced mass conservation. The formulation is obtained for an axisymmet...

  2. Diffusion in Solids Fundamentals, Methods, Materials, Diffusion-Controlled Processes

    CERN Document Server

    Mehrer, Helmut

    2007-01-01

    Diffusion is a vital topic in solid-state physics and chemistry, physical metallurgy and materials science. Diffusion processes are ubiquitous in solids at elevated temperatures. A thorough understanding of diffusion in materials is crucial for materials development and engineering. This book first gives an account of the central aspects of diffusion in solids, for which the necessary background is a course in solid state physics. It then provides easy access to important information about diffuson in metals, alloys, semiconductors, ion-conducting materials, glasses and nanomaterials. Several diffusion-controlled phenomena, including ionic conduction, grain-boundary and dislocation pipe diffusion, are considered as well. Graduate students in solid-state physics, physical metallurgy, materials science, physical and inorganic chemistry or geophysics will benefit from this book as will physicists, chemists, metallurgists, materials engineers in academic and industrial research laboratories.

  3. Enzymatic Modification of Sphingomyelin

    DEFF Research Database (Denmark)

    Due to its major role in maintaining the water-retaining properties of the epidermis, ceramide is of great commercial potential in cosmetic and pharmaceuticals such as hair and skin care products. Currently, chemical synthesis of ceramide is a costly process, and developments of alternative cost......-efficient, high yield production methods are of great interest. In the present study, the potential of producing ceramide through the enzymatic hydrolysis of sphingomyelin have been studied. sphingomyelin is a ubiquitous membrane-lipid and rich in dairy products or by-products. It has been verified...... that sphingomyelin modification gives a feasible approach to the potential production of ceramide. The reaction system has been improved through system evaluation and the optimization of several important factors, and phospholipase C from Clostridium perfringens shows higher activity towards the hydrolysis reaction...

  4. Enzymatic modification of starch

    DEFF Research Database (Denmark)

    Jensen, Susanne Langgård

    In the food industry approaches for using bioengineering are investigated as alternatives to conventional chemical and physical starch modification techniques in development of starches with specific properties. Enzyme-assisted post-harvest modification is an interesting approach to this, since...... it is considered a clean and energy saving technology. This thesis aimed to investigate the effect of using reaction conditions, simulating an industrial process, for enzymatic treatment of starch with branching enzyme (BE) from Rhodothermus obamensis. Thus treatements were conducted at 70°C using very high...... substrate concentration (30-40% dry matter (DM)) and high enzyme activity (750-2250 BE units (BEU)/g sample). Starches from various botanical sources, representing a broad range of properties, were used as substrates. The effects of the used conditions on the BE-reaction were evaluated by characterization...

  5. Super Nonlinear Electrodeposition-Diffusion-Controlled Thin-Film Selector.

    Science.gov (United States)

    Ji, Xinglong; Song, Li; He, Wei; Huang, Kejie; Yan, Zhiyuan; Zhong, Shuai; Zhang, Yishu; Zhao, Rong

    2018-03-28

    Selector elements with high nonlinearity are an indispensable part in constructing high density, large-scale, 3D stackable emerging nonvolatile memory and neuromorphic network. Although significant efforts have been devoted to developing novel thin-film selectors, it remains a great challenge in achieving good switching performance in the selectors to satisfy the stringent electrical criteria of diverse memory elements. In this work, we utilized high-defect-density chalcogenide glass (Ge 2 Sb 2 Te 5 ) in conjunction with high mobility Ag element (Ag-GST) to achieve a super nonlinear selective switching. A novel electrodeposition-diffusion dynamic selector based on Ag-GST exhibits superior selecting performance including excellent nonlinearity (<5 mV/dev), ultra-low leakage (<10 fA), and bidirectional operation. With the solid microstructure evidence and dynamic analyses, we attributed the selective switching to the competition between the electrodeposition and diffusion of Ag atoms in the glassy GST matrix under electric field. A switching model is proposed, and the in-depth understanding of the selective switching mechanism offers an insight of switching dynamics for the electrodeposition-diffusion-controlled thin-film selector. This work opens a new direction of selector designs by combining high mobility elements and high-defect-density chalcogenide glasses, which can be extended to other materials with similar properties.

  6. The crystal structure of Lactococcus lactis dihydroorotate dehydrogenase A complexed with the enzyme reaction product throws light on its enzymatic function

    DEFF Research Database (Denmark)

    Rowland, Paul; Bjørnberg, Olof; Nielsen, Finn S.

    1998-01-01

    Dihydroorotate dehydrogenases (DHODs) catalyze the oxidation of (S)-dihydroorotate to orotate, the fourth step and only redox reaction in the de novo biosynthesis of pyrimidine nucleotides. A description is given of the crystal structure of Lactococcus lactis dihydroorotate dehydrogenase A (DHODA......) complexed with the product of the enzyme reaction orotate. The structure of the complex to 2.0 A resolution has been compared with the structure of the native enzyme. The active site of DHODA is known to contain a water filled cavity buried beneath a highly conserved and flexible loop. In the complex...

  7. Implementation of a Low-Cost Automated LED Photometer for Enzymatic Reaction Detection to Teach Basic Bioelectronics Technologies in Vocational High Schools

    Science.gov (United States)

    Chen, Huai-Yi; Nieh, Hwa-Ming; Yang, Ming-Feng; Chou, Yu-Kung; Chung, Jui-Hsu; Liou, Je-Wen

    2016-01-01

    This study proposes a home-assembled, low-cost blue light-emitting diode (LED) photometer that uses simple and low-cost hardware and software, costing about US $150. This 425-nm wavelength photometer is controlled by an 89C51 microcontroller chip. Glucose concentration detection experiments involving enzyme coupling reactions were carried out to…

  8. Development of a Sensitive Electrochemical Enzymatic Reaction-Based Cholesterol Biosensor Using Nano-Sized Carbon Interdigitated Electrodes Decorated with Gold Nanoparticles.

    Science.gov (United States)

    Sharma, Deepti; Lee, Jongmin; Seo, Junyoung; Shin, Heungjoo

    2017-09-15

    We developed a versatile and highly sensitive biosensor platform. The platform is based on electrochemical-enzymatic redox cycling induced by selective enzyme immobilization on nano-sized carbon interdigitated electrodes (IDEs) decorated with gold nanoparticles (AuNPs). Without resorting to sophisticated nanofabrication technologies, we used batch wafer-level carbon microelectromechanical systems (C-MEMS) processes to fabricate 3D carbon IDEs reproducibly, simply, and cost effectively. In addition, AuNPs were selectively electrodeposited on specific carbon nanoelectrodes; the high surface-to-volume ratio and fast electron transfer ability of AuNPs enhanced the electrochemical signal across these carbon IDEs. Gold nanoparticle characteristics such as size and morphology were reproducibly controlled by modulating the step-potential and time period in the electrodeposition processes. To detect cholesterol selectively using AuNP/carbon IDEs, cholesterol oxidase (ChOx) was selectively immobilized via the electrochemical reduction of the diazonium cation. The sensitivity of the AuNP/carbon IDE-based biosensor was ensured by efficient amplification of the redox mediators, ferricyanide and ferrocyanide, between selectively immobilized enzyme sites and both of the combs of AuNP/carbon IDEs. The presented AuNP/carbon IDE-based cholesterol biosensor exhibited a wide sensing range (0.005-10 mM) and high sensitivity (~993.91 µA mM -1 cm -2 ; limit of detection (LOD) ~1.28 µM). In addition, the proposed cholesterol biosensor was found to be highly selective for the cholesterol detection.

  9. Random-walk simulation of diffusion-controlled processes among static traps

    International Nuclear Information System (INIS)

    Lee, S.B.; Kim, I.C.; Miller, C.A.; Torquato, S.; Department of Mechanical and Aerospace Engineering and Department of Chemical Engineering, North Carolina State University, Raleigh, North Carolina 27695-7910)

    1989-01-01

    We present computer-simulation results for the trapping rate (rate constant) k associated with diffusion-controlled reactions among identical, static spherical traps distributed with an arbitrary degree of impenetrability using a Pearson random-walk algorithm. We specifically consider the penetrable-concentric-shell model in which each trap of diameter σ is composed of a mutually impenetrable core of diameter λσ, encompassed by a perfectly penetrable shell of thickness (1-λ)σ/2: λ=0 corresponding to randomly centered or ''fully penetrable'' traps and λ=1 corresponding to totally impenetrable traps. Trapping rates are calculated accurately from the random-walk algorithm at the extreme limits of λ (λ=0 and 1) and at an intermediate value (λ=0.8), for a wide range of trap densities. Our simulation procedure has a relatively fast execution time. It is found that k increases with increasing impenetrability at fixed trap concentration. These ''exact'' data are compared with previous theories for the trapping rate. Although a good approximate theory exists for the fully-penetrable-trap case, there are no currently available theories that can provide good estimates of the trapping rate for a moderate to high density of traps with nonzero hard cores (λ>0)

  10. From conservative to reactive transport under diffusion-controlled conditions

    Science.gov (United States)

    Babey, Tristan; de Dreuzy, Jean-Raynald; Ginn, Timothy R.

    2016-05-01

    We assess the possibility to use conservative transport information, such as that contained in transit time distributions, breakthrough curves and tracer tests, to predict nonlinear fluid-rock interactions in fracture/matrix or mobile/immobile conditions. Reference simulated data are given by conservative and reactive transport simulations in several diffusive porosity structures differing by their topological organization. Reactions includes nonlinear kinetically controlled dissolution and desorption. Effective Multi-Rate Mass Transfer models (MRMT) are calibrated solely on conservative transport information without pore topology information and provide concentration distributions on which effective reaction rates are estimated. Reference simulated reaction rates and effective reaction rates evaluated by MRMT are compared, as well as characteristic desorption and dissolution times. Although not exactly equal, these indicators remain very close whatever the porous structure, differing at most by 0.6% and 10% for desorption and dissolution. At early times, this close agreement arises from the fine characterization of the diffusive porosity close to the mobile zone that controls fast mobile-diffusive exchanges. At intermediate to late times, concentration gradients are strongly reduced by diffusion, and reactivity can be captured by a very limited number of rates. We conclude that effective models calibrated solely on conservative transport information like MRMT can accurately estimate monocomponent kinetically controlled nonlinear fluid-rock interactions. Their relevance might extend to more advanced biogeochemical reactions because of the good characterization of conservative concentration distributions, even by parsimonious models (e.g., MRMT with 3-5 rates). We propose a methodology to estimate reactive transport from conservative transport in mobile-immobile conditions.

  11. Enzymatic Spectrophotometric Reaction Rate Determination of Glucose in Fruit Drinks and Carbonated Beverages. An Analytical Chemistry Laboratory Experiment for Food Science-Oriented Students

    Science.gov (United States)

    Vasilarou, Argyro-Maria G.; Georgiou, Constantinos A.

    2000-10-01

    The glucose oxidase-horseradish peroxidase coupled reaction using phenol and 4-aminoantipyrine is used for the kinetic determination of glucose in drinks and beverages. This laboratory experiment demonstrates the implementation of reaction rate kinetic methods of analysis, the use of enzymes as selective analytical reagents for the determination of substrates, the kinetic masking of ascorbic acid interference, and the analysis of glucose in drinks and beverages. The method is optimized for student use in the temperature range of 18-28 °C and can be used in low-budget laboratories equipped with an inexpensive visible photometer. The mixed enzyme-chromogen solution that is used is stable for two months. Precision ranged from 5.1 to 12% RSD for analyses conducted during a period of two months by 48 students.

  12. The dipteran parasitoid Exorista bombycis induces pro- and anti-oxidative reactions in the silkworm Bombyx mori: Enzymatic and genetic analysis.

    Science.gov (United States)

    Makwana, Pooja; Pradeep, Appukuttan Nair R; Hungund, Shambhavi P; Ponnuvel, Kangayam M; Trivedy, Kanika

    2017-02-01

    Hymenopteran parasitoids inject various factors including polydnaviruses along with their eggs into their host insects that suppress host immunity reactions to the eggs and larvae. Less is known about the mechanisms evolved in dipteran parasitoids that suppress host immunity. Here we report that the dipteran, Exorista bombycis, parasitization leads to pro-oxidative reactions and activation of anti-oxidative enzymes in the silkworm Bombyx mori larva. We recorded increased activity of oxidase, superoxide dismutase, thioredoxin peroxidase, catalase, glutathione-S-transferase (GST), and peroxidases in the hemolymph plasma, hemocytes, and fat body collected from B. mori after E. bombycis parasitization. Microarray and qPCR showed differential expression of genes encoding pro- and anti-oxidant enzymes in the hemocytes. The significance of this work lies in increased understanding of dipteran parasitoid biology. © 2017 Wiley Periodicals, Inc.

  13. Reaction

    African Journals Online (AJOL)

    abp

    19 oct. 2017 ... Reaction to Mohamed Said Nakhli et al. concerning the article: "When the axillary block remains the only alternative in a 5 year old child". .... Bertini L1, Savoia G, De Nicola A, Ivani G, Gravino E, Albani A et al ... 2010;7(2):101-.

  14. QM/MM Geometry Optimization on Extensive Free-Energy Surfaces for Examination of Enzymatic Reactions and Design of Novel Functional Properties of Proteins.

    Science.gov (United States)

    Hayashi, Shigehiko; Uchida, Yoshihiro; Hasegawa, Taisuke; Higashi, Masahiro; Kosugi, Takahiro; Kamiya, Motoshi

    2017-05-05

    Many remarkable molecular functions of proteins use their characteristic global and slow conformational dynamics through coupling of local chemical states in reaction centers with global conformational changes of proteins. To theoretically examine the functional processes of proteins in atomic detail, a methodology of quantum mechanical/molecular mechanical (QM/MM) free-energy geometry optimization is introduced. In the methodology, a geometry optimization of a local reaction center is performed with a quantum mechanical calculation on a free-energy surface constructed with conformational samples of the surrounding protein environment obtained by a molecular dynamics simulation with a molecular mechanics force field. Geometry optimizations on extensive free-energy surfaces by a QM/MM reweighting free-energy self-consistent field method designed to be variationally consistent and computationally efficient have enabled examinations of the multiscale molecular coupling of local chemical states with global protein conformational changes in functional processes and analysis and design of protein mutants with novel functional properties.

  15. Online quench-flow electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry for elucidating kinetic and chemical enzymatic reaction mechanisms.

    Science.gov (United States)

    Clarke, David J; Stokes, Adam A; Langridge-Smith, Pat; Mackay, C Logan

    2010-03-01

    We have developed an automated quench-flow microreactor which interfaces directly to an electrospray ionization (ESI) mass spectrometer. We have used this device in conjunction with ESI Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) to demonstrate the potential of this approach for studying the mechanistic details of enzyme reactions. For the model system chosen to test this device, namely, the pre-steady-state hydrolysis of p-nitrophenyl acetate by the enzyme chymotrypsin, the kinetic parameters obtained are in good agreement with those in the literature. To our knowledge, this is the first reported use of online quench-flow coupled with FTICR MS. Furthermore, we have exploited the power of FTICR MS to interrogate the quenched covalently bound enzyme intermediate using top-down fragmentation. The accurate mass capabilities of FTICR MS permitted the nature of the intermediate to be assigned with high confidence. Electron capture dissociation (ECD) fragmentation allowed us to locate the intermediate to a five amino acid section of the protein--which includes the known catalytic residue, Ser(195). This experimental approach, which uniquely can provide both kinetic and chemical details of enzyme mechanisms, is a potentially powerful tool for studies of enzyme catalysis.

  16. Comparison of the role that entropy has played in processes of non-enzymatic and enzymatic catalysis

    International Nuclear Information System (INIS)

    Dixon Pineda, Manuel Tomas

    2012-01-01

    The function that entropy has played is compared in processes of non-enzymatic and enzymatic catalysis. The processes followed are showed: the kinetics of the acid hydrolysis of 3-pentyl acetate and cyclopentyl acetate catalyzed by hydrochloric acid and enzymatic hydrolysis of ethyl acetate and γ-butyrolactone catalyzed by pig liver esterase. The activation parameters of Eyring were determined for each process and interpreted the contribution of the entropy of activation for catalysis in this type of model reactions. (author) [es

  17. An active site mutant of Escherichia coli cyclopropane fatty acid synthase forms new non-natural fatty acids providing insights on the mechanism of the enzymatic reaction.

    Science.gov (United States)

    E, Guangqi; Drujon, Thierry; Correia, Isabelle; Ploux, Olivier; Guianvarc'h, Dominique

    2013-12-01

    We have produced and purified an active site mutant of the Escherichia coli cyclopropane fatty acid synthase (CFAS) by replacing the strictly conserved G236 within cyclopropane synthases, by a glutamate residue, which corresponds to E146 of the homologous mycolic acid methyltransferase, Hma, producing hydroxymethyl mycolic acids. The G236E CFAS mutant had less than 1% of the in vitro activity of the wild type enzyme. We expressed the G236E CFAS mutant in an E. coli (DE3) strain in which the chromosomal cfa gene had been deleted. After extraction of phospholipids and conversion into the corresponding fatty acid methyl esters (FAMEs), we observed the formation of cyclopropanated FAMEs suggesting that the mutant retained some of the normal activity in vivo. However, we also observed the formation of new C17 methyl-branched unsaturated FAMEs whose structures were determined using GC/MS and NMR analyses. The double bond was located at different positions 8, 9 or 10, and the methyl group at position 10 or 9. Thus, this new FAMEs are likely arising from a 16:1 acyl chain of a phospholipid that had been transformed by the G236E CFAS mutant in vivo. The reaction catalyzed by this G236E CFAS mutant thus starts by the methylation of the unsaturated acyl chain at position 10 or 9 yielding a carbocation at position 9 or 10 respectively. It follows then two competing steps, a normal cyclopropanation or hydride shift/elimination events giving different combinations of alkenes. This study not only provides further evidence that cyclopropane synthases (CSs) form a carbocationic intermediate but also opens the way to CSs engineering for the synthesis of non-natural fatty acids. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

  18. Enzymatic network for production of ether amines from alcohols

    NARCIS (Netherlands)

    Palacio, Cyntia M.; Crismaru, Gica Ciprian; Bartsch, Sebastian; Navickas, Vaidotas; Ditrich, Klaus; Breuer, Michael; Abu, Rohana; Woodley, John; Baldenius, Kai-Uwe; Wu, Bian; Janssen, Dick

    We constructed an enzymatic network composed of three different enzymes for the synthesis of valuable ether amines. The enzymatic reactions are interconnected to catalyze the oxidation and subsequent transamination of the substrate and to provide cofactor recycling. This allows production of the

  19. Enzymatic labelling of. gamma. -globulin and insulin with iodine-125

    Energy Technology Data Exchange (ETDEWEB)

    Lucka, B; Russin, K [Institute of Nuclear Physics, Krakow (Poland)

    1979-01-01

    The parameters of enzymatic labelling of proteins with iodine 125 were examined. The manner and sequence of reagent addition, the effects of reagent concentration, reaction time and total Na/sup 125/I activity on the labelling yield were determined.

  20. Enzymatic approaches to rare sugar production.

    Science.gov (United States)

    Zhang, Wenli; Zhang, Tao; Jiang, Bo; Mu, Wanmeng

    Rare sugars have recently attracted much attention because of their potential applications in the food, nutraceutical, and pharmaceutical industries. A systematic strategy for enzymatic production of rare sugars, named Izumoring, was developed >10years ago. The strategy consists of aldose-ketose isomerization, ketose C-3 epimerization, and monosaccharide oxidation-reduction. Recent development of the Izumoring strategy is reviewed herein, especially the genetic approaches to the improvement of rare sugar-producing enzymes and the applications of target-oriented bioconversion. In addition, novel non-Izumoring enzymatic approaches are also summarized, including enzymatic condensation, phosphorylation-dephosphorylation cascade reaction, aldose epimerization, ulosonic acid decarboxylation, and biosynthesis of rare disaccharides. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. Enzymatic Inverse Opal Hydrogel Particles for Biocatalyst.

    Science.gov (United States)

    Wang, Huan; Gu, Hongcheng; Chen, Zhuoyue; Shang, Luoran; Zhao, Ze; Gu, Zhongze; Zhao, Yuanjin

    2017-04-19

    Enzymatic carriers have a demonstrated value for chemical reactions and industrial applications. Here, we present a novel kind of inverse opal hydrogel particles as the enzymatic carriers. The particles were negatively replicated from spherical colloidal crystal templates by using magnetic nanoparticles tagged acrylamide hydrogel. Thus, they were endowed with the features of monodispersity, small volume, complete penetrating structure, and controllable motion, which are all beneficial for improving the efficiency of biocatalysis. In addition, due to the ordered porous nanostructure, the inverse opal hydrogel particles were imparted with unique photonic band gaps (PBGs) and vivid structural colors for encoding varieties of immobilized enzymes and for constructing a multienzymes biocatalysis system. These features of the inverse opal hydrogel particles indicate that they are ideal enzymatic carriers for biocatalysis.

  2. Photoelectrochemical enzymatic biosensors.

    Science.gov (United States)

    Zhao, Wei-Wei; Xu, Jing-Juan; Chen, Hong-Yuan

    2017-06-15

    Enzymatic biosensors have been valuable bioanalytical devices for analysis of diverse targets in disease diagnosis, biological and biomedical research, etc. Photoelectrochemical (PEC) bioanalysis is a recently emerged method that promptly becoming a subject of new research interests due to its attractive potential for future bioanalysis with high sensitivity and specificity. PEC enzymatic biosensors integrate the inherent sensitivities of PEC bioanalysis and the selectivity of enzymes and thus share their both advantages. Currently, PEC enzymatic biosensors have become a hot topic of significant research and the recent impetus has grown rapidly as demonstrated by increased research papers. Given the pace of advances in this area, this review will make a thorough discussion and survey on the fundamentals, sensing strategies, applications and the state of the art in PEC enzymatic biosensors, followed by future prospects based on our own opinions. We hope this work could provide an accessible introduction to PEC enzymatic biosensors for any scientist. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Influence of enzymatic reactions on the electrochemical behavior of EN X2CrNiMo17-11-2 (AISI 316L) stainless steel in bio-corrosion: role of interfacial processes on the modification of the passive layer; Influence des reactions enzymatiques sur le comportement electrochimique de l'acier inoxydable ENX2CrNiMo17-11-2 (AISI 316L) en biocorrosion: role des processus interfaciaux sur la modification du film passif

    Energy Technology Data Exchange (ETDEWEB)

    Landoulsi, J

    2008-01-15

    The outstanding corrosion behavior of stainless steels (SS) results from the presence of thin oxide layer (some nanometers). In non sterile aqueous media, stainless steels may exhibit a non stable behavior resulting from interactions between microbial species and passive film. In fact, microorganisms can be deeply involved in the corrosion processes usually reported as Microbial Influenced Corrosion (MIC). They can induce the initiation or the acceleration of this phenomenon and they do so when organized in bio-films. From the electrochemical point of view, stainless steels showed an increase of the free corrosion potential (Ecorr) attributed to the bio-film settlement. The Eco' ennoblement was broadly reported in seawater and seems to be confirmed in fresh water according to recent findings. A considerable progress in the comprehension of MIC processes was related to the role of extracellular species, essentially enzymes. Many enzymatic reactions occurring in bio-films consist on using oxygen as electron acceptor to generate hydrogen peroxide and related species. The aim of this work is to understand the mechanisms involved in the electrochemical behavior of stainless steel according to an enzymatic approach in medium simulating fresh water. To this end, glucose oxidase was chosen to globalize aerobic activities of bio-films. Electrochemical measurements in situ and surface analysis allow the comprehension of the role and the nature of interfacial processes. Surface characterization was performed with the help of a new quantitative utilization of XPS analysis and AFM. Results show a significant evolution in term of morphology (surface organization), (ii) chemical composition (passive layer, adsorbed organic species) and (iii) chemical reaction (oxidation, dissolution, effect of enzyme). Finally, a new enzymatic system is proposed to mimic specific physicochemical conditions at the SS / bio-film interface, in particular enzymatic generation of oxidant species

  4. Method for the enzymatic production of hydrogen

    Science.gov (United States)

    Woodward, J.; Mattingly, S.M.

    1999-08-24

    The present invention is an enzymatic method for producing hydrogen comprising the steps of: (a) forming a reaction mixture within a reaction vessel comprising a substrate capable of undergoing oxidation within a catabolic reaction, such as glucose, galactose, xylose, mannose, sucrose, lactose, cellulose, xylan and starch; the reaction mixture also comprising an amount of glucose dehydrogenase in an amount sufficient to catalyze the oxidation of the substrate, an amount of hydrogenase sufficient to catalyze an electron-requiring reaction wherein a stoichiometric yield of hydrogen is produced, an amount of pH buffer in an amount sufficient to provide an environment that allows the hydrogenase and the glucose dehydrogenase to retain sufficient activity for the production of hydrogen to occur and also comprising an amount of nicotinamide adenine dinucleotide phosphate sufficient to transfer electrons from the catabolic reaction to the electron-requiring reaction; (b) heating the reaction mixture at a temperature sufficient for glucose dehydrogenase and the hydrogenase to retain sufficient activity and sufficient for the production of hydrogen to occur, and heating for a period of time that continues until the hydrogen is no longer produced by the reaction mixture, wherein the catabolic reaction and the electron-requiring reactions have rates of reaction dependent upon the temperature; and (c) detecting the hydrogen produced from the reaction mixture. 8 figs.

  5. Enzymatic synthesis of vanillin

    NARCIS (Netherlands)

    van den Heuvel, RHH; Fraaije, MW; Laane, C; van Berkel, WJH; Heuvel, Robert H.H. van den; Berkel, Willem J.H. van

    Due to increasing interest in natural vanillin, two enzymatic routes for the synthesis of vanillin were developed. The flavoprotein vanillyl alcohol oxidase (VAO) acts on a wide range of phenolic compounds and converts both creosol and vanillylamine to vanillin with high yield. The VAO-mediated

  6. Enzymatic synthesis of vanillin

    NARCIS (Netherlands)

    Heuvel, van den R.H.H.; Fraaije, M.W.; Laane, C.; Berkel, van W.J.H.

    2001-01-01

    Due to increasing interest in natural vanillin, two enzymatic routes for the synthesis of vanillin were developed. The flavoprotein vanillyl alcohol oxidase (VAO) acts on a wide range of phenolic compounds and converts both creosol and vanillylamine to vanillin with high yield. The VAO-mediated

  7. Enzymatic Activity Detection via Electrochemistry for Enceladus

    Science.gov (United States)

    Studemeister, Lucy; Koehne, Jessica; Quinn, Richard

    2017-01-01

    Electrochemical detection of biological molecules is a pertinent topic and application in many fields such as medicine, environmental spills, and life detection in space. Proteases, a class of molecules of interest in the search for life, catalyze the hydrolysis of peptides. Trypsin, a specific protease, was chosen to investigate an optimized enzyme detection system using electrochemistry. This study aims at providing the ideal functionalization of an electrode that can reliably detect a signal indicative of an enzymatic reaction from an Enceladus sample.

  8. Enzymatic epoxidation of biodiesel optimized by response surface ...

    African Journals Online (AJOL)

    During the enzymatic epoxidation of biodiesel, stearic acid was selected as oxygen carrier. Enzyme screening and the load of stearic acid were investigated. The effects of four main reaction conditions including reaction time, temperature, enzyme load, and mole ratio of H2O2/C=C-bonds on the epoxy oxygen group content ...

  9. Enzymatic desulfurization of coal

    Energy Technology Data Exchange (ETDEWEB)

    Boyer, Y.N.; Crooker, S.C.; Kitchell, J.P.; Nochur, S.V.

    1991-05-16

    The overall objective of this program was to investigate the feasibility of an enzymatic desulfurization process specifically intended for organic sulfur removal from coal. Toward that end, a series of specific objectives were defined: (1) establish the feasibility of (bio)oxidative pretreatment followed by biochemical sulfate cleavage for representative sulfur-containing model compounds and coals using commercially-available enzymes; (2) investigate the potential for the isolation and selective use of enzyme preparations from coal-utilizing microbial systems for desulfurization of sulfur-containing model compounds and coals; and (3) develop a conceptual design and economic analysis of a process for enzymatic removal of organic sulfur from coal. Within the scope of this program, it was proposed to carry out a portion of each of these efforts concurrently. (VC)

  10. Enzymatic hydrolysis of multi-use forage energy crops, year 2 report: Studies on the improvement of reaction conditions, differences between forages. SRC technical report No. 141, and SRC publication No. C-711-6-B-83

    Energy Technology Data Exchange (ETDEWEB)

    Jackson, L.J.; Coxworth, E.C.

    1983-12-31

    The main objective of the work described in this report is to optimize the conversion of forages and crop residues to simple sugars, and to determine the quantity of protein that can be readily recovered after enzymatic hydrolysis of those materials. The simple sugars would be used as substrates for fermentation to fuels and chemicals, and the protein is a potentially valuable byproduct for use as fertilizer or feed. The plant materials studied were kochia, Jerusalem artichoke, pea stem and chaff, oilseed radish, alfalfa, and slender wheat grass. The enzymes used in the hydrolysis were Onozuka R-10, Celluclast 200L Type N, and cellobiase 250L. Results reported include comparisons of enzymatic reactivity of the materials studied, the quantity of protein remaining after treatment, and the dry matter solubility of the materials achieved using the different enzymes.

  11. Isothermal calorimetry on enzymatic biodiesel production

    DEFF Research Database (Denmark)

    Fjerbæk, Lene

    2008-01-01

    information about effects taking place when using lipases immobilized on an inert carrier for transesterification of a triglyceride and an alcohol as for biodiesel production. The biodiesel is produced by rapeseed oil and methanol as well as ethanol and a commercial biocatalyst Novozym 435 from Novozymes...... containing a Candida Antarctica B lipase immobilized on an acrylic resin. The reaction investigated is characterized by immiscible liquids (oil, methanol, glycerol and biodiesel) and enzymes imm. on an inert carrier during reaction, which allows several effects to take place that during normal reaction...... conditions can not be elucidated. These effects have been observed with isothermal calorimetry bringing forth new information about the reaction of enzymes catalyzing transesterification. Enzymatic biodiesel production has until now not been investigated with isothermal microcalorimetry, but the results...

  12. Archetypal sandwich-structured CuO for high performance non-enzymatic sensing of glucose

    Science.gov (United States)

    Meher, Sumanta Kumar; Rao, G. Ranga

    2013-02-01

    In the quest to enhance the selectivity and sensitivity of novel structured metal oxides for electrochemical non-enzymatic sensing of glucose, we report here a green synthesis of unique sandwich-structured CuO on a large scale under microwave mediated homogeneous precipitation conditions. The physicochemical studies carried out by XRD and BET methods show that the monoclinic CuO formed via thermal decomposition of Cu2(OH)2CO3 possesses monomodal channel-type pores with largely improved surface area (~43 m2 g-1) and pore volume (0.163 cm3 g-1). The fascinating surface morphology and pore structure of CuO is formulated due to homogeneous crystallization and microwave induced self assembly during synthesis. The cyclic voltammetry and chronoamperometry studies show diffusion controlled glucose oxidation at ~0.6 V (vs. Ag/AgCl) with extremely high sensitivity of 5342.8 μA mM-1 cm-2 and respective detection limit and response time of ~1 μM and ~0.7 s, under a wide dynamic concentration range of glucose. The chronoamperometry measurements demonstrate that the sensitivity of CuO to glucose is unaffected by the absence of dissolved oxygen and presence of poisoning chloride ions in the reaction medium, which essentially implies high poison resistance activity of the sandwich-structured CuO. The sandwich-structured CuO also shows insignificant interference/significant selectivity to glucose, even in the presence of high concentrations of other sugars as well as reducing species. In addition, the sandwich-structured CuO shows excellent reproducibility (relative standard deviation of ~2.4% over ten identically fabricated electrodes) and outstanding long term stability (only ~1.3% loss in sensitivity over a period of one month) during non-enzymatic electrochemical sensing of glucose. The unique microstructure and suitable channel-type pore architecture provide structural stability and maximum accessible electroactive surface for unimpeded mobility of glucose as well as the

  13. Production of MAG via enzymatic glycerolysis

    Science.gov (United States)

    Jamlus, Norul Naziraa Ahmad; Derawi, Darfizzi; Salimon, Jumat

    2015-09-01

    Enzymatic glycerolysis of a medium chain methyl ester, methyl laurate was performed using lipase Candida antarctica (Novozyme 435) for 6 hours at 55°C. The percentage of components mixture of product were determined by using gas chromatography technique. The enzymatic reaction was successfully produced monolaurin (45.9 %), dilaurin (47.1 %) and trilaurin (7.0 %) respectively. Thin layer chromatography (TLC) plate also showed a good separation of component spots. Fourier transformation infra-red (FTIR) spectrum showed the presence of ester carbonyl at wavenumber 1739.99 cm-1 and hydrogen bonded O-H at 3512.03 cm-1. The product is potentially to be used as emulsifier and additive in food industry, pharmaceutical, as well as antibacterial.

  14. Kinetics of Bio-Reactions

    DEFF Research Database (Denmark)

    Villadsen, John

    2015-01-01

    his chapter predicts the specific rates of reaction by means of a mathematical expression, the kinetics of the reaction. This expression can be derived through a mechanistic interpretation of an enzymatically catalyzed reaction, but it is essentially of empirical nature for cell reactions. The mo...

  15. Implantation of algorithms of diffuse control in DSPS; Implantacion de algoritmos de control difuso en DSPS

    Energy Technology Data Exchange (ETDEWEB)

    Perez C, B

    2003-07-01

    In this thesis work there are presented: a) The characteristics and main components used in an electronic system based on a Dsp guided to control applications of processes, b) The description of an algorithm of diffuse control whose objective is the regulation of neutron power in a model of the punctual kinetics of a nuclear research reactor type TRIGA, and c) The installation in language assembler and execution in real time of the control algorithm in the system based on a Dsp. With regard to the installation and execution of the algorithm, the reaches of the project have been delimited to the following: a) Readiness of the entrance values to the controller in specific registrations of the system Dsp, b) Conversion of the entrances to the numerical formats with those that one obtains the best acting in the control algorithm, c) Execution of the algorithm until the obtaining of the value of the controller's exit, and d) Placement of the result in specific registrations of the Dsp for their later reading for an external parallel interface. It is necessary to mention that the simulation of the punctual kinetics of a reactor type TRIGA in the Pc and its integration with the control system based on the one Dsp is had contemplated as continuation of this work and that one of those will constitute main activities in my project of master thesis. A brief description of the topics presented in this thesis is given next. In the chapter one it is presented a general description of the diffuse logic and some of their applications in the industry. The main characteristics of a Dsp are also presented that they make it different from a micro controller or a microprocessor of general purpose. In the chapter 2 details of the internal architecture of the Dsp TMS320CS0 of Texas Instruments that are not explained with detail in the manual of user of the same one. This chapter has as objective to understand the internal hardware of the Dsp that is used for to carry out the program in

  16. Implantation of algorithms of diffuse control in DSPS; Implantacion de algoritmos de control difuso en DSPS

    Energy Technology Data Exchange (ETDEWEB)

    Perez C, B

    2003-07-01

    In this thesis work there are presented: a) The characteristics and main components used in an electronic system based on a Dsp guided to control applications of processes, b) The description of an algorithm of diffuse control whose objective is the regulation of neutron power in a model of the punctual kinetics of a nuclear research reactor type TRIGA, and c) The installation in language assembler and execution in real time of the control algorithm in the system based on a Dsp. With regard to the installation and execution of the algorithm, the reaches of the project have been delimited to the following: a) Readiness of the entrance values to the controller in specific registrations of the system Dsp, b) Conversion of the entrances to the numerical formats with those that one obtains the best acting in the control algorithm, c) Execution of the algorithm until the obtaining of the value of the controller's exit, and d) Placement of the result in specific registrations of the Dsp for their later reading for an external parallel interface. It is necessary to mention that the simulation of the punctual kinetics of a reactor type TRIGA in the Pc and its integration with the control system based on the one Dsp is had contemplated as continuation of this work and that one of those will constitute main activities in my project of master thesis. A brief description of the topics presented in this thesis is given next. In the chapter one it is presented a general description of the diffuse logic and some of their applications in the industry. The main characteristics of a Dsp are also presented that they make it different from a micro controller or a microprocessor of general purpose. In the chapter 2 details of the internal architecture of the Dsp TMS320CS0 of Texas Instruments that are not explained with detail in the manual of user of the same one. This chapter has as objective to understand the internal hardware of the Dsp that is used for to carry out the program

  17. Degradations and Rearrangement Reactions

    Science.gov (United States)

    Zhang, Jianbo

    This section deals with recent reports concerning degradation and rearrangement reactions of free sugars as well as some glycosides. The transformations are classified in chemical and enzymatic ways. In addition, the Maillard reaction will be discussed as an example of degradation and rearrangement transformation and its application in current research in the fields of chemistry and biology.

  18. Shape and topology optimization of enzymatic microreactors

    DEFF Research Database (Denmark)

    Pereira Rosinha, Ines

    for effective and cost efficient reactors for pharmaceutical processes forces the industry to search for better technologies. In biochemical engineering, the used reactor design in a given process is usually limited to a range of well-established configurations and layouts. Usually the implemented reactors...... in a chemical process do not always yield in the best reaction conditions.This thesis develops an innovative application of topology and shape optimization methods to achemical engineering problem. The main goal is to design a reactor according to the limitations of the reaction system by modifying the reactor...... configuration. In this thesis structural optimization methods were exclusively applied to enzymatic microreactors. The case studies were chosen such that they can be experimentally tested afterwards. In this way, the design of the reactor is customized to the reaction system and itcontributes to the reduction...

  19. MODELING OF SUPERCRITICAL FLUID EXTRACTION KINETIC OF FLAXSEED OIL BY DIFFUSION CONTROL METHOD

    Directory of Open Access Journals (Sweden)

    Emir Zafer HOŞGÜN

    2013-06-01

    Full Text Available In this study, Flaxseed oil was extracted by Supercritical Carbondioxide Extraction, and extractionkinetics was modelled using diffusion controlled method.The effect of process parameters, such as pressure (20, 35, 55 MPa, temperature (323 and 343 K, and CO2 flow rate (1 and 3 L CO2 /min on the extraction yield and effective diffusivity (De was investigated. The effective diffusion coefficient varied between 2.4 x10-12 and 10.8 x10-12 m2s-1 for the entire range of experiments and increased with the pressure and flow rate. The model fitted well theexperimental data (ADD varied between 2.35 and 7.48%.

  20. Diffusion-controlled regime of surface-wave-produced plasmas in helium gas

    International Nuclear Information System (INIS)

    Berndt, J; Makasheva, K; Schlueter, H; Shivarova, A

    2002-01-01

    The study presents a numerical fluid-plasma model of diffusion-controlled surface-wave-sustained discharges in helium gas. The self-consistent behaviour of the discharge based on the interrelation between plasma density and Θ, the power absorbed on average by one electron, is described. The nonlinear process of step ionization in the charged particle balance equation is the main factor, which ensures the self-consistency. However, it is shown that in helium discharges, the ionization frequencies enter the dependence of Θ on the plasma density also through the ambipolar-diffusion coefficient. Results at two different values of the gas pressure and of the wave frequency are discussed. The lower value of the gas pressure is chosen according to the condition to have a pure diffusion-controlled regime without interference with a transition to the free-fall regime. The boundary condition for the ion flux at the wall sheath is used for determination of the value of μ, the quantity denoting the degree of the radial plasma-density inhomogeneity which, together with the electron-neutral elastic collision frequency, influences the wave propagation characteristics. The two values of the wave frequency chosen provide descriptions of high-frequency and microwave discharges. The model results in the self-consistent structure of the discharge: interrelated variations along the discharge length of wavenumber, space damping rate, Θ, plasma density and electron temperature. The power necessary for sustaining discharges of a given length is also calculated. Comparisons with argon discharges are shown

  1. Continuous and discreet methods in the aggregation and des fuzzy stages of a diffuse controller of neutron power

    International Nuclear Information System (INIS)

    Najera H, M.C.; Benitez R, J.S.

    2003-01-01

    The results of a comparative study are presented of: to) A denominated diffuse controller 'exact', designed by means of an innovative method that determines analytically so much the group of exit resultant in the aggregation stage like the de fuzzy process, and b) a diffuse controller denominated 'discreet' based on the discretization of the variable of having left as much for the aggregation as for the de fuzzy. These stages incorporated to the control algorithms whose objective is the ascent and regulation of the neutron power, carrying out an analysis of its performance. (Author)

  2. Quantifying the limits of transition state theory in enzymatic catalysis.

    Science.gov (United States)

    Zinovjev, Kirill; Tuñón, Iñaki

    2017-11-21

    While being one of the most popular reaction rate theories, the applicability of transition state theory to the study of enzymatic reactions has been often challenged. The complex dynamic nature of the protein environment raised the question about the validity of the nonrecrossing hypothesis, a cornerstone in this theory. We present a computational strategy to quantify the error associated to transition state theory from the number of recrossings observed at the equicommittor, which is the best possible dividing surface. Application of a direct multidimensional transition state optimization to the hydride transfer step in human dihydrofolate reductase shows that both the participation of the protein degrees of freedom in the reaction coordinate and the error associated to the nonrecrossing hypothesis are small. Thus, the use of transition state theory, even with simplified reaction coordinates, provides a good theoretical framework for the study of enzymatic catalysis. Copyright © 2017 the Author(s). Published by PNAS.

  3. Rational design of functional and tunable oscillating enzymatic networks

    Science.gov (United States)

    Semenov, Sergey N.; Wong, Albert S. Y.; van der Made, R. Martijn; Postma, Sjoerd G. J.; Groen, Joost; van Roekel, Hendrik W. H.; de Greef, Tom F. A.; Huck, Wilhelm T. S.

    2015-02-01

    Life is sustained by complex systems operating far from equilibrium and consisting of a multitude of enzymatic reaction networks. The operating principles of biology's regulatory networks are known, but the in vitro assembly of out-of-equilibrium enzymatic reaction networks has proved challenging, limiting the development of synthetic systems showing autonomous behaviour. Here, we present a strategy for the rational design of programmable functional reaction networks that exhibit dynamic behaviour. We demonstrate that a network built around autoactivation and delayed negative feedback of the enzyme trypsin is capable of producing sustained oscillating concentrations of active trypsin for over 65 h. Other functions, such as amplification, analog-to-digital conversion and periodic control over equilibrium systems, are obtained by linking multiple network modules in microfluidic flow reactors. The methodology developed here provides a general framework to construct dissipative, tunable and robust (bio)chemical reaction networks.

  4. Investigations on diffusion-controlled transformations in creep resistant steels and graded cemented carbides

    International Nuclear Information System (INIS)

    Prat Borquez, Orlando

    2011-01-01

    The objective of this work was to simulate diffusion-controlled transformations on engineering alloys designed by the author and his colleagues. The main challenge of the work is to adapt the existing DICTRA models to the experimental processing and working conditions investigated, as well as to find the adequate boundary conditions for the description of the diffusion-controlled transformations governing the microstructure formation and evolution, in order to obtain reliable simulation results. The simulations were compared with experimental results of the microstructure evolution by scanning electron microscopy and scanning transmission electron microscopy (STEM). Two groups of materials were investigated. The first group was 9-12% Cr heat resistant alloys. These alloys are particularly interesting because the microstructure evolves during working conditions. Different compositions were designed in order to form different kinds and amounts of precipitates. For the designed 9-12% Cr creep steels the coarsening of MX and M 23 C 6 particles was modeled by applying the coarsening model implemented in DICTRA. The cell method of DICTRA was applied to investigate the kinetics of the Laves phase growth on 9-12% Cr alloys. The particular objectives of these investigations were: a) to determine the coarsening rate of precipitates, b) to investigate the influence of alloying element on the growth rate of the Laves phase, c) to determine the influence of the M 23 C 6 formation on the growth kinetics of the Laves phase, d) to determine the growth mechanism at the interface of the Laves phase (i.e. up-hill diffusion), e) to investigate the effect of the cell size on the simulation kinetics of Laves phase. The second group of materials was cemented carbides. They are used as cutting tools or wear parts in the automotive, aircraft and mining industry among others. The wear performance of cemented carbides (hardmetals and cermets) can be largely improved by applying wear

  5. Parâmetros reacionais para a síntese enzimática do butirato de butila em solventes orgânicos Reactional parameters for enzymatic synthesis of butyl butyrate in organic solvent

    Directory of Open Access Journals (Sweden)

    Heizir F. CASTRO

    1997-12-01

    Full Text Available A síntese orgânica catalisada por enzimas envolve um mecanismo complexo dependente do tipo de substrato, enzima, solvente orgânico e teor de água no meio reacional. Neste trabalho foi estudado a influência de alguns desses parâmetros no rendimento da esterificação do butanol com ácido butírico, utilizando uma preparação enzimática comercial de lipase. A polaridade e natureza do solvente, bem como a razão molar entre o butanol e ácido butírico, foram considerados os fatores que mais influenciaram o desenvolvimento dessa síntese enzimática.The organic synthesis catalyzed by enzymes is a complex function of substrate concentration, water concentration in the liquid phase, enzyme and organic solvent properties. In this work the influence of some parameters on the esterification of butanol with butyric acid was investigated, using a commercial lipase preparation. The polarity and nature of the solvent and also the substrate mole ratios played an important role in the performance of this enzymatic synthesis.

  6. Solid-state diffusion-controlled growth of the phases in the Au-Sn system

    Science.gov (United States)

    Baheti, Varun A.; Kashyap, Sanjay; Kumar, Praveen; Chattopadhyay, Kamanio; Paul, Aloke

    2018-01-01

    The solid state diffusion-controlled growth of the phases is studied for the Au-Sn system in the range of room temperature to 200 °C using bulk and electroplated diffusion couples. The number of product phases in the interdiffusion zone decreases with the decrease in annealing temperature. These phases grow with significantly high rates even at the room temperature. The growth rate of the AuSn4 phase is observed to be higher in the case of electroplated diffusion couple because of the relatively small grains and hence high contribution of the grain boundary diffusion when compared to the bulk diffusion couple. The diffraction pattern analysis indicates the same equilibrium crystal structure of the phases in these two types of diffusion couples. The analysis in the AuSn4 phase relating the estimated tracer diffusion coefficients with grain size, crystal structure, the homologous temperature of experiments and the concept of the sublattice diffusion mechanism in the intermetallic compounds indicate that Au diffuses mainly via the grain boundaries, whereas Sn diffuses via both the grain boundaries and the lattice.

  7. Production of Fish Hydrolysates Protein From Waste of Fish Carp (Cyprinus Carpio) by Enzymatic Hydrolysis

    OpenAIRE

    Saputra, Dede; Nurhayati, Tati

    2016-01-01

    Fish Protein Hydrolysates (FPH) is the mixed products of polypeptide, dipeptides, and amino acid. It can be produced from materials that contained of protein by acid reaction, base reaction or enzymatic hydrolysis. The objectives of this study were to study the production of FPH from fish carp meat at post rigor phase and viscera by enzymatic hydrolysis, to determine the specific activity of papain enzyme, and to determine the solubility of FPH. Capacity of fish hydrolyzing can be identified ...

  8. Evaluation of wet oxidation pretreatment for enzymatic hydrolysis of softwood

    DEFF Research Database (Denmark)

    Palonen, H.; Thomsen, A.B.; Tenkanen, M.

    2004-01-01

    The wet oxidation pretreatment (water, oxygen, elevated temperature, and pressure) of softwood (Picea abies) was investigated for enhancing enzymatic hydrolysis. The pretreatment was preliminarily optimized. Six different combinations of reaction time, temperature, and pH were applied......, and the compositions of solid and liquid fractions were analyzed. The solid fraction after wet oxidation contained 58-64% cellulose, 2-16% hemicellulose, and 24-30% lignin. The pretreatment series gave information about the roles of lignin and hemicellulose in the enzymatic hydrolysis. The temperature...

  9. Enzymatic network for production of ether amines from alcohols

    DEFF Research Database (Denmark)

    Palacio, Cyntia M.; Crismaru, Ciprian G.; Bartsch, Sebastian

    2016-01-01

    We constructed an enzymatic network composed of three different enzymes for the synthesis of valuable ether amines. The enzymatic reactions are interconnected to catalyze the oxidation and subsequent transamination of the substrate and to provide cofactor recycling. This allows production...... of the desired ether amines from the corresponding ether alcohols with inorganic ammonium as the only additional substrate. To examine conversion, individual and overall reaction equilibria were established. Using these data, it was found that the experimentally observed conversions of up to 60% observed...... for reactions containing 10mM alcohol and up to 280mM ammonia corresponded well to predicted conversions. The results indicate that efficient amination can be driven by high concentrations of ammonia and may require improving enzyme robustness for scale-up....

  10. Diffusion-controlled cementation experiments in porous rock analogues using potash alum and halite

    Energy Technology Data Exchange (ETDEWEB)

    Hufe, A.; Hilgers, C. [RWTH Aachen Univ. (Germany). Inst. of Reservoir-Petrology; Stanjek, H. [RWTH Aachen Univ. (Germany). Inst. of Interface and Clay Mineralogy

    2013-08-01

    A good understanding of cementation is critical for reservoir quality predictions. However, studies of core material have shown that cementation may be driven by variations in pore size of the host rock. To better understand the underlying process, we developed a transparent microreactor for diffusion-controlled cementation experiments under the microscope. We studied the effect of different pore sizes and surface charges of solid material at different pH, using rock analogs. High-resolution videos allowed to analyze the nucleation from solution, pore cementation and growth rates of cements. Diffusion - considered the major mass transport during burial diagenesis - was driven along a temperature gradient across the microreactor. Pores were cemented with salt, which is well known to form pore-size dependent seals in silicilastic reservoirs. While halite precipitated primarily in pores bigger than 200 {mu}m, alum nucleated in smaller pores. The growth rate of alum (10{sup -5} mm/s) was one order of magnitude higher than that of halite. However, the dissolution rates of both minerals was similar at about 10{sup -6} mm/s. Authigenic euhdral halite migrated against the bulk diffusion transport and towards the higher-temperature reservoir. Halite growth rates increased by one order of magnitude to 1.8 x 10{sup -5} mm/s, if the phase boundary was vapor-liquid. A comparison nucleation in a 2-phase porous rock analog showed no difference in cementation pattern at a pH 7. However, at a pH of 10.5 the surface energies of the two different solids are altered, and porosity was reduced 60% more by cements in the phase-1 porous layers. Our experiments showed that pore size dependent nucleation and cementation is a process, which may also take place in complex reservoirs. With the successful pore clogging of halite we can now bring our experimental setup to reservoir conditions and establish the processes at elevated p-T conditions. (orig.)

  11. Enzymatic Hydrolysis of Alkaline Pretreated Coconut Coir

    Directory of Open Access Journals (Sweden)

    Akbarningrum Fatmawati

    2013-06-01

    Full Text Available The purpose of this research is to study the effect of concentration and temperature on the cellulose and lignin content, and the reducing sugars produced in the enzymatic hydrolysis of coconut coir. In this research, the coconut coir is pretreated using 3%, 7%, and 11% NaOH solution at 60oC, 80oC, and 100oC. The pretreated coir were assayed by measuring the amount of cellulose and lignin and then hydrolysed using Celluclast and Novozyme 188 under various temperature (30oC, 40oC, 50oC and pH (3, 4, 5. The hydrolysis results were assayed for the reducing sugar content. The results showed that the alkaline delignification was effective to reduce lignin and to increase the cellulose content of the coir. The best delignification condition was observed at 11% NaOH solution and 100oC which removed 14,53% of lignin and increased the cellulose content up to 50,23%. The best condition of the enzymatic hydrolysis was obtained at 50oC and pH 4 which produced 7,57 gr/L reducing sugar. © 2013 BCREC UNDIP. All rights reservedReceived: 2nd October 2012; Revised: 31st January 2013; Accepted: 6th February 2013[How to Cite: Fatmawati, A., Agustriyanto, R., Liasari, Y. (2013. Enzymatic Hydrolysis of Alkaline Pre-treated Coconut Coir. Bulletin of Chemical Reaction Engineering & Catalysis, 8 (1: 34-39 (doi:10.9767/bcrec.8.1.4048.34-39[Permalink/DOI: http://dx.doi.org/10.9767/bcrec.8.1.4048.34-39] | View in  |

  12. Automatic single- and multi-label enzymatic function prediction by machine learning

    Directory of Open Access Journals (Sweden)

    Shervine Amidi

    2017-03-01

    Full Text Available The number of protein structures in the PDB database has been increasing more than 15-fold since 1999. The creation of computational models predicting enzymatic function is of major importance since such models provide the means to better understand the behavior of newly discovered enzymes when catalyzing chemical reactions. Until now, single-label classification has been widely performed for predicting enzymatic function limiting the application to enzymes performing unique reactions and introducing errors when multi-functional enzymes are examined. Indeed, some enzymes may be performing different reactions and can hence be directly associated with multiple enzymatic functions. In the present work, we propose a multi-label enzymatic function classification scheme that combines structural and amino acid sequence information. We investigate two fusion approaches (in the feature level and decision level and assess the methodology for general enzymatic function prediction indicated by the first digit of the enzyme commission (EC code (six main classes on 40,034 enzymes from the PDB database. The proposed single-label and multi-label models predict correctly the actual functional activities in 97.8% and 95.5% (based on Hamming-loss of the cases, respectively. Also the multi-label model predicts all possible enzymatic reactions in 85.4% of the multi-labeled enzymes when the number of reactions is unknown. Code and datasets are available at https://figshare.com/s/a63e0bafa9b71fc7cbd7.

  13. Enzymatic deconstruction of xylan for biofuel production

    Science.gov (United States)

    DODD, DYLAN; CANN, ISAAC K. O.

    2010-01-01

    The combustion of fossil-derived fuels has a significant impact on atmospheric carbon dioxide (CO2) levels and correspondingly is an important contributor to anthropogenic global climate change. Plants have evolved photosynthetic mechanisms in which solar energy is used to fix CO2 into carbohydrates. Thus, combustion of biofuels, derived from plant biomass, can be considered a potentially carbon neutral process. One of the major limitations for efficient conversion of plant biomass to biofuels is the recalcitrant nature of the plant cell wall, which is composed mostly of lignocellulosic materials (lignin, cellulose, and hemicellulose). The heteropolymer xylan represents the most abundant hemicellulosic polysaccharide and is composed primarily of xylose, arabinose, and glucuronic acid. Microbes have evolved a plethora of enzymatic strategies for hydrolyzing xylan into its constituent sugars for subsequent fermentation to biofuels. Therefore, microorganisms are considered an important source of biocatalysts in the emerging biofuel industry. To produce an optimized enzymatic cocktail for xylan deconstruction, it will be valuable to gain insight at the molecular level of the chemical linkages and the mechanisms by which these enzymes recognize their substrates and catalyze their reactions. Recent advances in genomics, proteomics, and structural biology have revolutionized our understanding of the microbial xylanolytic enzymes. This review focuses on current understanding of the molecular basis for substrate specificity and catalysis by enzymes involved in xylan deconstruction. PMID:20431716

  14. Enzymatic hydrolysis of lactose of whey permeate

    Directory of Open Access Journals (Sweden)

    Karina Nascimento de Almeida

    2015-09-01

    Full Text Available The whey permeate is the residual of the concentration process of the whey proteins by ultrafiltration method. It contains important nutrients such as lactose, minerals and some proteins and lipids. It is without an ending industrial waste that causes serious damage to the environment. For its full use the lactose must be hydrolyzed to enable its consumption by intolerant people. The enzymatic hydrolysis by lactase (β-galactosidase of Kluyveromyces lactis yeast is a safe method that does not compromise the integrity of other nutrients, enabling further use of the permeate as a raw material. This study aimed to perform tests of enzymatic hydrolysis of lactose in whey permeate formulations in a concentration of 0.2%, 0.7% and 1% at 30, 60 and 90 minutes with pH 6.3 medium and 37 °C. The reactions were monitored by high performance liquid chromatography which showed that the enzyme concentration of 0.7% at time 30 minutes formulations became safe for consumption by lactose intolerant people, according to minimum levels established by law.

  15. Enzymatic transesterification of used frying oils

    Energy Technology Data Exchange (ETDEWEB)

    Kovacs, S.; Hancsok, J. (Univ. of Pannonia, Veszprem (HU)), Email: hancsokj@almos.uni-pannon.hu

    2009-07-01

    The research of converting used frying oils to less harmful products with much higher value was forced by environmental, human biological and economical reasons. One possible pathway of the transformation is the enzymatic transesterification. Through the research work used frying oils (UFO) and sunflower oils (SO) from different origins were first properly pre-treated. Then the previously mentioned feeds and different mixtures of them were transesterified in the presence of Novozym 435 enzyme catalyst under different process conditions. Characteristics of the produced methyl esters were evaluated according to the requirements of EN 14214:2009 standard. We determined that the transesterification of used frying oils is not expediential in the presence of enzyme catalyst because the significant decreasing of catalyst activity. We have found proper UFO and SO mixtures and combination of process conditions (pressure: atmospheric, temperature: 54 +-1 deg C; methanol to triglyceride molar ratio: 4:1; reaction time: 16 hours) resulting in high (>90 %) yield of monoesters. We clearly established that the best results through the enzymatic transesterification were obtained with the improved sunflower oils containing the highest amount (>88 %) of oleic acid and the used frying oils originated from this source. (orig.)

  16. Enzymatic Browning: a practical class

    Directory of Open Access Journals (Sweden)

    Maria Teresa Pedrosa Silva Clerici

    2014-10-01

    Full Text Available This paper presents a practical class about the enzymes polyphenol oxidases, which have been shown to be responsible for the enzymatic browning of fruits and vegetables. Vegetables samples were submitted to enzymatic inactivation process with chemical reagents, as well as by bleaching methods of applying heat by conventional oven and microwave oven. Process efficiency was assessed qualitatively by both observing the guaiacol peroxidase activity and after the storage period under refrigeration or freezing. The practical results obtained in this class allow exploring multidisciplinary knowledge in food science, with practical applications in everyday life.

  17. The mean first passage time in an energy-diffusion controlled regime with power-law distributions

    International Nuclear Information System (INIS)

    Zhou, Yanjun; Du, Jiulin

    2013-01-01

    Based on the mean first passage time (MFPT) theory, we derive an expression of the MFPT in an energy-diffusion controlled regime with a power-law distribution. We discuss the finite barrier effect (i.e. the thermal energy k B T is not small with respect to the potential barrier E b ) and compare it with Kramers’ infinite barrier result both in a power-law distribution and in a Maxwell–Boltzmann distribution. It is shown that the MFPT with a power-law distribution extends Kramers’ low-damping result to a relatively low barrier. We pay attention to the energy-diffusion controlled regime, which is of great interest in the context of Josephson junctions, and study how the power-law parameter κ affects the current distribution function in experiments with Josephson junctions. (paper)

  18. Formulation and analyses of vaporization and diffusion-controlled combustion of fuel sprays

    OpenAIRE

    Arrieta Sanagustín, Jorge

    2012-01-01

    This dissertation focuses on the modelling of vaporization and combustion of sprays. A general two-continua formulation is given for the numerical computation of spray flows, including the treatment of the droplets as homogenized sources. Group combustion is considered, with the reaction between the fuel coming from the vaporizing droplets and the oxygen of the air modeled in the Burke-Schumann limit of infinitely fast chemical reaction, with nonunity Lewis numbers allowed for the different r...

  19. Enzymatic production of ceramide from sphingomyelin

    DEFF Research Database (Denmark)

    Zhang, Long; Hellgren, Lars; Xu, Xuebing

    Ceramide is the key intermediate in the biosynthesis of all complex sphingolipids. Due to its major role in maintaining the water-retaining properties of the epidermis, ceramide is of great commercial potential in cosmetic and pharmaceuticals such as hair and skin care products. Currently, chemical...... contains a ceramide moiety, is a ubiquitous component of animal cell membranes, and dairy products or by-products is a rich source of sphingomyelin. It has been verified that enzymatic modification of sphingomyelin is a feasible approach for production of ceramide. The reaction system has been optimized...... through system evaluation and the optimization of several important factors. Sphingomyelin hydrolysis proved to be more efficient in two-phase (water: organic solvent) system than in one-phase (water-saturated organic solvent) system. Phospholipase C from Clostridium perfringens is the tested enzyme which...

  20. Direct electron transfer based enzymatic fuel cells

    International Nuclear Information System (INIS)

    Falk, Magnus; Blum, Zoltan; Shleev, Sergey

    2012-01-01

    In this mini-review we briefly describe some historical developments made in the field of enzymatic fuel cells (FCs), discussing important design considerations taken when constructing mediator-, cofactor-, and membrane-less biological FCs (BFCs). Since the topic is rather extensive, only BFCs utilizing direct electron transfer (DET) reactions on both the anodic and cathodic sides are considered. Moreover, the performance of mostly glucose/oxygen biodevices is analyzed and compared. We also present some unpublished results on mediator-, cofactor-, and membrane-less glucose/oxygen BFCs recently designed in our group and tested in different human physiological fluids, such as blood, plasma, saliva, and tears. Finally, further perspectives for BFC applications are highlighted.

  1. THEORY DEVELOPMENT OF ENZYMATIC AROMA RECOVERY

    Directory of Open Access Journals (Sweden)

    G. E. Dubova

    2014-01-01

    Full Text Available Summary. The fruit and vegetable pretreatment conditions and subsequent environment in which enzymatic reactions take place can be considered as potential factors in the formation of fresh flavors. The synthesis of aromatic components of fresh grass and green leaves occurs involving vegetable lipoxygenases. The molecules of a precursor-compound can withstand the processing modes, while enzymes and aromatic compounds break down frequently. Vegetable homogenates are potential sources of enzymes which produce natural aromatic substances. Formation of fresh favors is the most perceptible when it occurs as the result of the reaction between poliunsaturated fatty acids of cytoplasmic membranes and lipoxygenases and hydroperoxide lyase of plant material. Pre-treatment of samples positively influences binding energy in the complex of enzyme-substrate. The change of iodine number in treated homogenates, as compared to fresh ones, shows isomerization of flavor precursors. The minimal quantity of homogenates introduced (up to 20 g and the duration of aroma-restoring reaction (from 5 to 7 minutes were defined. Pre-cooling of homogenates activates enzymes, strengthens oxidability of the PUFA, and results in recovery of fresh aroma of plant material. Under conditions of enzyme inactivation, the synthesis of aromas is not possible. Conversely, production of aroma in food glazes and foams is possible in case of interphase activation between a substrate and enzymes.

  2. Perspectives for the industrial enzymatic production of glycosides.

    Science.gov (United States)

    de Roode, B Mattheus; Franssen, Maurice C R; van der Padt, Albert; Boom, Remko M

    2003-01-01

    Glycosides are of commercial interest for industry in general and specifically for the pharmaceutical and food industry. Currently chemical preparation of glycosides will not meet EC food regulations, and therefore chemical preparation of glycosides is not applicable in the food industry. Thus, enzyme-catalyzed reactions are a good alternative. However, until now the low yields obtained by enzymatic methods prevent the production of glycosides on a commercial scale. Therefore, high yields should be established by a combination of optimum reaction conditions and continuous removal of the product. Unfortunately, a bioreactor for the commercial scale production of glycosides is not available. The aim of this article is to discuss the literature with respect to enzymatic production of glycosides and the design of an industrially viable bioreactor system.

  3. Dynamic modeling and validation of a lignocellulosic enzymatic hydrolysis process

    DEFF Research Database (Denmark)

    Prunescu, Remus Mihail; Sin, Gürkan

    2013-01-01

    The enzymatic hydrolysis process is one of the key steps in second generation biofuel production. After being thermally pretreated, the lignocellulosic material is liquefied by enzymes prior to fermentation. The scope of this paper is to evaluate a dynamic model of the hydrolysis process...... on a demonstration scale reactor. The following novel features are included: the application of the Convection–Diffusion–Reaction equation to a hydrolysis reactor to assess transport and mixing effects; the extension of a competitive kinetic model with enzymatic pH dependency and hemicellulose hydrolysis......; a comprehensive pH model; and viscosity estimations during the course of reaction. The model is evaluated against real data extracted from a demonstration scale biorefinery throughout several days of operation. All measurements are within predictions uncertainty and, therefore, the model constitutes a valuable...

  4. Nanosilver: A Catalyst in Enzymatic Hydrolysis of Starch

    Directory of Open Access Journals (Sweden)

    Falkowska Marta

    2014-09-01

    Full Text Available Silver nanoparticles are widely used, because of their antimicrobial properties. In this paper, the rate of starch digestion in the presence of nanocatalyst was compared with the rate of reaction without nanosilver. The rate of enzymatic degradation of starch was found to be increased in the presence of silver nanoparticles. It is considered that α-amylase was immobilized onto the surface of nanoparticles.

  5. Kinetic modelling of enzymatic starch hydrolysis

    NARCIS (Netherlands)

    Bednarska, K.A.

    2015-01-01

    Kinetic modelling of enzymatic starch hydrolysis – a summary

    K.A. Bednarska

    The dissertation entitled ‘Kinetic modelling of enzymatic starch hydrolysis’ describes the enzymatic hydrolysis and kinetic modelling of liquefaction and saccharification of wheat starch.

  6. Modelling the Effects of Ageing Time of Starch on the Enzymatic Activity of Three Amylolytic Enzymes

    Science.gov (United States)

    Guerra, Nelson P.; Pastrana Castro, Lorenzo

    2012-01-01

    The effect of increasing ageing time (t) of starch on the activity of three amylolytic enzymes (Termamyl, San Super, and BAN) was investigated. Although all the enzymatic reactions follow michaelian kinetics, v max decreased significantly (P enzymes and the release of the reaction products to the medium. A similar effect was observed when the enzymatic reactions were carried out with unaged starches supplemented with different concentrations of gelatine [G]. The inhibition in the amylolytic activities was best mathematically described by using three modified forms of the Michaelis-Menten model, which included a term to consider, respectively, the linear, exponential, and hyperbolic inhibitory effects of t and [G]. PMID:22666116

  7. Impact of the fouling mechanism on enzymatic depolymerization of xylan in different configurations of membrane reactors

    DEFF Research Database (Denmark)

    Mohd Sueb, Mohd Shafiq Bin; Luo, Jianquan; Meyer, Anne S.

    2017-01-01

    In order to maximize enzymatic xylan depolymerization while simultaneously purifying the resulting monosaccharide (xylose), different ultrafiltration (UF) membrane reactor configurations were evaluated. Initial results showed that the two hydrolytic enzymes required for complete depolymerization...... which hindered enzymatic attack in addition to fouling. Reaction with both enzymes followed by UF was found to be the optimal configuration, providing at least 40% higher xylan hydrolysis than the cascade configuration (involving sequential reaction with each of the enzymes separately......) and the simultaneous reaction-filtration with both enzymes, respectively. This study thus confirmed that the reactor configuration has a crucial impact on the performance of both the reaction and the separation process of xylose during enzymatic xylan degradation, and that the type of fouling mechanism varies...

  8. Immobilization of alcohol dehydrogenase on ceramic silicon carbide membranes for enzymatic CH3 OH production

    DEFF Research Database (Denmark)

    Zeuner, Birgitte; Ma, Nicolaj; Berendt, Kasper

    2018-01-01

    BACKGROUND Alcohol dehydrogenase (ADH; EC 1.1.1.1) catalyzes oxidation of CH3OH to CHOH during NAD+ reduction to NADH. ADH can also accelerate the reverse reaction, which is studied as part of cascadic enzymatic conversion of CO2 to CH3OH. In the present study, immobilization of ADH onto macropor......BACKGROUND Alcohol dehydrogenase (ADH; EC 1.1.1.1) catalyzes oxidation of CH3OH to CHOH during NAD+ reduction to NADH. ADH can also accelerate the reverse reaction, which is studied as part of cascadic enzymatic conversion of CO2 to CH3OH. In the present study, immobilization of ADH onto......‐of‐concept for the use of NaOH‐treated SiC membranes for covalent enzyme immobilization and biocatalytic efficiency improvement of ADH during multiple reaction cycles. These data have implications for the development of robust extended enzymatic reactions....

  9. Use of hydrostatic pressure for modulation of protein chemical modification and enzymatic selectivity.

    Science.gov (United States)

    Makarov, Alexey A; Helmy, Roy; Joyce, Leo; Reibarkh, Mikhail; Maust, Mathew; Ren, Sumei; Mergelsberg, Ingrid; Welch, Christopher J

    2016-05-11

    Using hydrostatic pressure to induce protein conformational changes can be a powerful tool for altering the availability of protein reactive sites and for changing the selectivity of enzymatic reactions. Using a pressure apparatus, it has been demonstrated that hydrostatic pressure can be used to modulate the reactivity of lysine residues of the protein ubiquitin with a water-soluble amine-specific homobifunctional coupling agent. Fewer reactive lysine residues were observed when the reaction was carried out under elevated pressure of 3 kbar, consistent with a pressure-induced conformational change of ubiquitin that results in fewer exposed lysine residues. Additionally, modulation of the stereoselectivity of an enzymatic transamination reaction was observed at elevated hydrostatic pressure. In one case, the minor diasteromeric product formed at atmospheric pressure became the major product at elevated pressure. Such pressure-induced alterations of protein reactivity may provide an important new tool for enzymatic reactions and the chemical modification of proteins.

  10. Real-time ESI-MS of enzymatic conversion: impact of organic solvents and multiplexing.

    Science.gov (United States)

    Scheerle, Romy K; Grassmann, Johanna; Letzel, Thomas

    2012-01-01

    Different enzymatic assays were characterized systematically by real-time electrospray ionization mass spectrometry (ESI-MS) in the presence of organic solvents as well as in multiplex approaches and in a combination of both. Typically, biological enzymatic reactions are studied in aqueous solutions, since most enzymes show their full activity solely in aqueous solutions. However, in recent years, the use of organic solvents in combination with enzymatic reactions has gained increasing interest due to biotechnological advantages in chemical synthesis, development of online coupled setups screening for enzyme regulatory compounds, advantages regarding mass spectrometric detection and others. In the current study, the influence of several common organic solvents (methanol, ethanol, isopropanol, acetone, acetonitrile) on enzymatic activity (hen egg white lysozyme, chitinase, α-chymotrypsin, elastase from human neutrophils and porcine pancreas, acetylcholinesterase) was tested. Moreover, multiplexing is a promising approach enabling fast and cost-efficient screening methods, e.g. for determination of inhibitors in complex mixtures or in the field of biomedical research. Although in multiplexed setups the enzymatic activity may be affected by the presence of other substrates and/or enzymes, the expected advantages possibly will predominate. To investigate those effects, we measured multiple enzymatic assays simultaneously. For all conducted measurements, the conversion rate of the substrate(s) was calculated, which reflects the enzymatic activity. The results provide an overview about the susceptibility of the selected enzymes towards diverse factors and a reference point for many applications in analytical chemistry and biotechnology.

  11. Enzymatic Processes in Marine Biotechnology.

    Science.gov (United States)

    Trincone, Antonio

    2017-03-25

    In previous review articles the attention of the biocatalytically oriented scientific community towards the marine environment as a source of biocatalysts focused on the habitat-related properties of marine enzymes. Updates have already appeared in the literature, including marine examples of oxidoreductases, hydrolases, transferases, isomerases, ligases, and lyases ready for food and pharmaceutical applications. Here a new approach for searching the literature and presenting a more refined analysis is adopted with respect to previous surveys, centering the attention on the enzymatic process rather than on a single novel activity. Fields of applications are easily individuated: (i) the biorefinery value-chain, where the provision of biomass is one of the most important aspects, with aquaculture as the prominent sector; (ii) the food industry, where the interest in the marine domain is similarly developed to deal with the enzymatic procedures adopted in food manipulation; (iii) the selective and easy extraction/modification of structurally complex marine molecules, where enzymatic treatments are a recognized tool to improve efficiency and selectivity; and (iv) marine biomarkers and derived applications (bioremediation) in pollution monitoring are also included in that these studies could be of high significance for the appreciation of marine bioprocesses.

  12. Asymmetric Chemoenzymatic Reductive Acylation of Ketones by a Combined Iron-Catalyzed Hydrogenation-Racemization and Enzymatic Resolution Cascade

    KAUST Repository

    El-Sepelgy, Osama; Brzozowska, Aleksandra; Rueping, Magnus

    2017-01-01

    . By merging the iron-catalyzed redox reactions with enantioselective enzymatic acylations a wide range of benzylic, aliphatic and (hetero)aromatic ketones, as well as diketones, were reductively acylated. The corresponding products were isolated with high

  13. Solid diffusion control of the adsorption of basic dyes onto granular activated carbon and natural zeolite in fixed bed columns

    Directory of Open Access Journals (Sweden)

    M. MARINKOVSKI

    2001-07-01

    Full Text Available The adsorption of basic dyes from aqueous solutions onto granular activated carbon and natural zeolite was studied using a fixed bed column. The design procedures for fixed bed adsorption columns were investigated for two basic dyes Maxilon Goldgelb GL EC 400 % (MG-400 and Maxilon Schwarz FBL-01 300 % (MS-300. A computer program based on the solid diffusion control model has been developed. The model parameters: solid diffusion coefficient, DS, axial dispersion coefficient, DL and external mass transfer coefficient, kf for all the investigated systems were estimated by means of a best fit approach.

  14. Pretreatment and enzymatic hydrolysis of lignocellulosic biomass

    Science.gov (United States)

    Corredor, Deisy Y.

    The performance of soybean hulls and forage sorghum as feedstocks for ethanol production was studied. The main goal of this research was to increase fermentable sugars' yield through high-efficiency pretreatment technology. Soybean hulls are a potential feedstock for production of bio-ethanol due to their high carbohydrate content (≈50%) of nearly 37% cellulose. Soybean hulls could be the ideal feedstock for fuel ethanol production, because they are abundant and require no special harvesting and additional transportation costs as they are already in the plant. Dilute acid and modified steam-explosion were used as pretreatment technologies to increase fermentable sugars yields. Effects of reaction time, temperature, acid concentration and type of acid on hydrolysis of hemicellulose in soybean hulls and total sugar yields were studied. Optimum pretreatment parameters and enzymatic hydrolysis conditions for converting soybean hulls into fermentable sugars were identified. The combination of acid (H2SO4, 2% w/v) and steam (140°C, 30 min) efficiently solubilized the hemicellulose, giving a pentose yield of 96%. Sorghum is a tropical grass grown primarily in semiarid and dry parts of the world, especially in areas too dry for corn. The production of sorghum results in about 30 million tons of byproducts mainly composed of cellulose, hemicellulose, and lignin. Forage sorghum such as brown midrib (BMR) sorghum for ethanol production has generated much interest since this trait is characterized genetically by lower lignin concentrations in the plant compared with conventional types. Three varieties of forage sorghum and one variety of regular sorghum were characterized and evaluated as feedstock for fermentable sugar production. Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and X-Ray diffraction were used to determine changes in structure and chemical composition of forage sorghum before and after pretreatment and enzymatic hydrolysis

  15. Enzymatic determination of cadmium, zinc, and lead in plant materials

    International Nuclear Information System (INIS)

    Muginova, S.V.; Veselova, I.A.; Parova, L.M.; Shekhovtseva, T.N.

    2008-01-01

    Prospects are outlined for using the following enzymes (native and immobilized on polyurethane foam) in the rapid and highly sensitive determination of cadmium, zinc, and lead ions in plant materials (wild grass, fresh pea, and grape): horseradish peroxidase and alkaline phosphatases isolated from chicken intestine and Greenland seal small intestine. The analytical ranges of the above metals are 1x10 -3 -25; 7x10 -3 -250, and 3x10 -2 -67 mg/kg dry matter, respectively. The enzymatic determination procedures developed are based on the inhibiting effect of metal ions on the catalytic activity of peroxidase in the oxidation of o-dianisidine with hydrogen peroxide and alkaline phosphatases in the hydrolysis of p-nitrophenyl phosphate. The rates of enzymatic reactions were monitored spectrophotometrically or visually. In the analysis of plant extracts, their high acidity was diminished by choosing optimum dilution factors and pH values for test samples and the nature and concentration of a buffer solution. The interference of iron(III) was removed by introducing a 0.1 M tartaric acid solution into the indicator reaction. The accuracy of the results of the enzymatic determination of cadmium, zinc, and lead in plant materials was supported by atomic absorption spectrometry and anodic stripping voltammetry [ru

  16. Insights in the Diffusion Controlled Interfacial Flow Synthesis of Au Nanostructures in a Microfluidic System.

    Science.gov (United States)

    Kulkarni, Amol A; Sebastian Cabeza, Victor

    2017-12-19

    Continuous segmented flow interfacial synthesis of Au nanostructures is demonstrated in a microchannel reactor. This study brings new insights into the growth of nanostructures at continuous interfaces. The size as well as the shape of the nanostructures showed significant dependence on the reactant concentrations, reaction time, temperature, and surface tension, which actually controlled the interfacial mass transfer. The microchannel reactor assisted in achieving a high interfacial area, as well as uniformity in mass transfer effects. Hexagonal nanostructures were seen to be formed in synthesis times as short as 10 min. The wettability of the channel showed significant effect on the particle size as well as the actual shape. The hydrophobic channel yielded hexagonal structures of relatively smaller size than the hydrophilic microchannel, which yielded sharp hexagonal bipyramidal particles (diagonal distance of 30 nm). The evolution of particle size and shape for the case of hydrophilic microchannel is also shown as a function of the residence time. The interfacial synthesis approach based on a stable segmented flow promoted an excellent control on the reaction extent, reduction in axial dispersion as well as the particle size distribution.

  17. Kinetics of enzymatic hydrolysis of methyl ricinoleate

    Directory of Open Access Journals (Sweden)

    Neeharika, T. S.V.R.

    2015-12-01

    Full Text Available Ricinoleic acid is an unsaturated hydroxy fatty acid that naturally occurs in castor oil in proportions of up to 85–90%. Ricinoleic acid is a potential raw material and finds several applications in coatings, lubricant formulations and pharmaceutical areas. Enzymatic hydrolysis of castor oil is preferred over conventional hydrolysis for the preparation of ricinoleic acid to avoid estolide formation. A kinetics analysis of the enzymatic hydrolysis of Methyl Ricinoleate in the presence of Candida antarctica Lipase B was carried out in this study by varying reaction temperature (40–60 °C and enzyme concentration (2–5%. The optimal conditions were found to be 6 h reaction time, temperature 60°C, buffer to methyl ricinoleate ratio 2:1(v/w and 4% enzyme concentration to achieve a maximum conversion of 98.5%. A first order reversible reaction kinetic model was proposed to describe this reaction and a good agreement was observed between the experimental data and the model values. The effect of temperature on the forward reaction rate constant was determined by fitting data to the Arrhenius equation. The activation energy for forward reaction was found to be 14.69 KJ·mol−1.El ácido ricinoleico es un hidroxiácido insaturado que se produce naturalmente en el aceite de ricino en proporciones de hasta el 85–90%. El ácido ricinoleico es una materia prima con gran potencial y tiene aplicaciones en revestimientos, formulaciones lubricantes y en áreas farmacéuticas. Para la preparación del ácido ricinoleico se prefiere la hidrólisis enzimática del aceite de ricino a la hidrólisis convencional, para evitar la formación de estólidos. En este estudio se llevó a cabo la cinética de la hidrólisis enzimática del ricinoleato de metilo en presencia de lipasa de Candida antarctica B mediante la variación de la temperatura de reacción (40–60 °C y la concentración de la enzima (2–5%. Las condiciones óptimas de la reacción para

  18. Enhanced enzymatic cellulose degradation by cellobiohydrolases via product removal

    DEFF Research Database (Denmark)

    Ahmadi Gavlighi, Hassan; Meyer, Anne S.; Mikkelsen, Jørn Dalgaard

    2013-01-01

    Product inhibition by cellobiose decreases the rate of enzymatic cellulose degradation. The optimal reaction conditions for two Emericella (Aspergillus) nidulans-derived cellobiohydrolases I and II produced in Pichia pastoris were identified as CBHI: 52 °C, pH 4.5–6.5, and CBHII: 46 °C, pH 4.......8. The optimum in a mixture of the two was 50 °C, pH 4.9. An almost fourfold increase in enzymatic hydrolysis yield was achieved with intermittent product removal of cellobiose with membrane filtration (2 kDa cut-off): The conversion of cotton cellulose after 72 h was ~19 % by weight, whereas the conversion...

  19. Enzymatic biodiesel synthesis. Key factors affecting efficiency of the process

    Energy Technology Data Exchange (ETDEWEB)

    Szczesna Antczak, Miroslawa; Kubiak, Aneta; Antczak, Tadeusz; Bielecki, Stanislaw [Institute of Technical Biochemistry, Faculty of Biotechnology and Food Sciences, Technical University of Lodz, Stefanowskiego 4/10, 90-924 Lodz (Poland)

    2009-05-15

    Chemical processes of biodiesel production are energy-consuming and generate undesirable by-products such as soaps and polymeric pigments that retard separation of pure methyl or ethyl esters of fatty acids from glycerol and di- and monoacylglycerols. Enzymatic, lipase-catalyzed biodiesel synthesis has no such drawbacks. Comprehension of the latter process and an appreciable progress in production of robust preparations of lipases may soon result in the replacement of chemical catalysts with enzymes in biodiesel synthesis. Engineering of enzymatic biodiesel synthesis processes requires optimization of such factors as: molar ratio of substrates (triacylglycerols: alcohol), temperature, type of organic solvent (if any) and water activity. All of them are correlated with properties of lipase preparation. This paper reports on the interplay between the crucial parameters of the lipase-catalyzed reactions carried out in non-aqueous systems and the yield of biodiesel synthesis. (author)

  20. Process Evaluation Tools for Enzymatic Cascades Welcome Message

    DEFF Research Database (Denmark)

    Abu, Rohana

    improvement and implementation. Hence, the goal of this thesis is to evaluate the process concepts in enzymatic cascades in a systematic manner, using tools such as thermodynamic and kinetic analysis. Three relevant case studies have been used to exemplify the approach. In the first case study, thermodynamic......Biocatalysis is attracting significant attention from both academic and industrial scientists due to the excellent capability of enzyme to catalyse selective reactions. Recently, much interest has been shown in the application of enzymatic cascades as a useful tool in organic synthesis......, the kinetics can be controlled in a highly efficient way to achieve a sufficiently favourable conversion to a given target product. This is exemplified in the second case study, in the kinetic modelling of the formation of 2-ketoglutarate from glucoronate, the second case study. This cascade consists of 4...

  1. Cyanodeoxy-Glycosyl Derivatives as Substrates for Enzymatic Reactions

    Czech Academy of Sciences Publication Activity Database

    Carmona, A. T.; Bojarová, Pavla; Křen, Vladimír; Ettrich, Rüdiger; Martínková, Ludmila; Moreno-Vargas, A. J.; González, C.; Robina, I.

    2006-01-01

    Roč. 8, - (2006), s. 1876-1885 ISSN 1434-193X R&D Projects: GA ČR GA203/05/0172; GA ČR GA203/05/2267; GA MŠk OC D25.002; GA MŠk OC D25.001 Institutional research plan: CEZ:AV0Z50200510; CEZ:AV0Z60870520 Keywords : sugar nitrile s * azido-tetrazole tautomerism * glycosidase Subject RIV: EE - Microbiology, Virology Impact factor: 2.769, year: 2006

  2. Microbial reactions in coal and coal relevant structures. Part project: fungal and enzymatic depolarisation of brown coal for the production of low-molecular compounds. Interim report; Mikrobielle Umsetzung an Kohle und kohlenrelevanten Strukturen. Teilvorhaben: Pilzliche und enzymatische Depolymerisation von Braunkohle zur Gewinnung niedermolekularer Verbindungen. Zwischenbericht (Berichtszeitraum 01.01.1998 - 31.12.1998)

    Energy Technology Data Exchange (ETDEWEB)

    Ziegenhagen, D.; Bublitz, F.; Sorge, S.; Ullrich, R.; Hofrichter, M.; Fritsche, W.

    1999-04-29

    The present research project involved a study of the depolymerisation of brown coal constituents. The purpose of the depolymerisation experiments, which were carried out with fungi as well as their (acellular) enzymes, was to obtain products with a potential market value. Research focussed on one of the key enzymes of lignocellulose degradation, namely manganese (II) peroxidase (MnP). The effects of this enzyme on the depolymerisation of brown coal was studied in detail in acellular systems. The insights gained in this way then served as a basis for optimising the fungal and enzymatic depolymerisation processes for maximum yields of low-molecular products. The experiments carried out during the period under review were oriented to finding new types of lignolytically active organisms, isolating lignolytic enzymes and immobilising them on natural support materials, and further examining the action spectrum of MnP. Different model substrates were used in order to gain information on what bond types are MnP-cleavable and on possible reaction products. Substrates were either fixed to silica gel as support material or used without support material. The idea of using substrates fixed to support materials was motivated by the need to distinguish between intracellular and extracellular reactions involving the fungal mycelium. [Deutsch] Im Rahmen des Forschungsvorhabens wird die Depolymerisation von Braunkohle-Bestandteilen untersucht. Ziel der sowohl mit Pilzorganismen als auch mit deren Enzymen (zellfrei) durchgefuehrten Depolymerisationsversuche ist die Gewinnung von Produkten mit potentiellem Werkstoffcharakter. Im Mittelpunkt der Forschung steht eines der Schluesselenzyme des Ligninozellulose-Abbaus: Die Mangan(II)-Peroxidase (MnP). Die Wirkung dieses Enzyms bei der Depolymerisation von Braunkohle (Bk) in zellfreien Systemen wird weitergehend untersucht. Auf Grundlage der gewonnenen Erkenntnisse werden die pilzlichen und enzymatischen Depolymerisationsprozesse so

  3. Glucose obtained from rice bran by ultrasound-assisted enzymatic hydrolysis

    Directory of Open Access Journals (Sweden)

    Raquel Cristine Kuhn

    2015-05-01

    Full Text Available In this work ultrasound-assisted solid-state enzymatic hydrolysis of rice bran to obtain fermentable sugars was investigated. For this purpose, process variables such as temperature, enzyme concentration and moisture content were evaluated during the enzymatic hydrolysis with and without ultrasound irradiation. The enzyme used is a blend of amylases derived from genetically modified strains of Trichoderma reesei. Kinetic of the enzymatic hydrolysis of rice bran at the constant-reaction rate period were measured. The best results for the ultrasound-assisted enzymatic hydrolysis was obtained using 3 wt% of enzyme, 60 oC and moisture content of 65 wt%, yielding 0.38 g sugar/g rice bran, whereas for the hydrolysis in the absence of ultrasound the highest yield was 0.20 g sugar/g rice bran using 3 wt% of enzyme, 60 oC and moisture content of 50 wt%. The use of ultrasound-assisted enzymatic hydrolysis of rice bran was intensified, obtaining around 74% more fermentable sugar than in the absence, showing that the use of ultrasound is a promising technology to be used in enzymatic reaction as an alternative of process intensification.

  4. Diffusion-controlled interface kinetics-inclusive system-theoretic propagation models for molecular communication systems

    Science.gov (United States)

    Chude-Okonkwo, Uche A. K.; Malekian, Reza; Maharaj, B. T.

    2015-12-01

    Inspired by biological systems, molecular communication has been proposed as a new communication paradigm that uses biochemical signals to transfer information from one nano device to another over a short distance. The biochemical nature of the information transfer process implies that for molecular communication purposes, the development of molecular channel models should take into consideration diffusion phenomenon as well as the physical/biochemical kinetic possibilities of the process. The physical and biochemical kinetics arise at the interfaces between the diffusion channel and the transmitter/receiver units. These interfaces are herein termed molecular antennas. In this paper, we present the deterministic propagation model of the molecular communication between an immobilized nanotransmitter and nanoreceiver, where the emission and reception kinetics are taken into consideration. Specifically, we derived closed-form system-theoretic models and expressions for configurations that represent different communication systems based on the type of molecular antennas used. The antennas considered are the nanopores at the transmitter and the surface receptor proteins/enzymes at the receiver. The developed models are simulated to show the influence of parameters such as the receiver radius, surface receptor protein/enzyme concentration, and various reaction rate constants. Results show that the effective receiver surface area and the rate constants are important to the system's output performance. Assuming high rate of catalysis, the analysis of the frequency behavior of the developed propagation channels in the form of transfer functions shows significant difference introduce by the inclusion of the molecular antennas into the diffusion-only model. It is also shown that for t > > 0 and with the information molecules' concentration greater than the Michaelis-Menten kinetic constant of the systems, the inclusion of surface receptors proteins and enzymes in the models

  5. Electrochemical non-enzymatic glucose sensors

    International Nuclear Information System (INIS)

    Park, Sejin; Boo, Hankil; Chung, Taek Dong

    2006-01-01

    The electrochemical determination of glucose concentration without using enzyme is one of the dreams that many researchers have been trying to make come true. As new materials have been reported and more knowledge on detailed mechanism of glucose oxidation has been unveiled, the non-enzymatic glucose sensor keeps coming closer to practical applications. Recent reports strongly imply that this progress will be accelerated in 'nanoera'. This article reviews the history of unraveling the mechanism of direct electrochemical oxidation of glucose and making attempts to develop successful electrochemical glucose sensors. The electrochemical oxidation of glucose molecules involves complex processes of adsorption, electron transfer, and subsequent chemical rearrangement, which are combined with the surface reactions on the metal surfaces. The information about the direct oxidation of glucose on solid-state surfaces as well as new electrode materials will lead us to possible breakthroughs in designing the enzymeless glucose sensing devices that realize innovative and powerful detection. An example of those is to introduce nanoporous platinum as an electrode, on which glucose is oxidized electrochemically with remarkable sensitivity and selectivity. Better model of such glucose sensors is sought by summarizing and revisiting the previous reports on the electrochemistry of glucose itself and new electrode materials

  6. Sugar ester surfactants: enzymatic synthesis and applications in food industry.

    Science.gov (United States)

    Neta, Nair S; Teixeira, José A; Rodrigues, Lígia R

    2015-01-01

    Sugar esters are non-ionic surfactants that can be synthesized in a single enzymatic reaction step using lipases. The stability and efficiency of lipases under unusual conditions and using non-conventional media can be significantly improved through immobilization and protein engineering. Also, the development of de novo enzymes has seen a significant increase lately under the scope of the new field of synthetic biology. Depending on the esterification degree and the nature of fatty acid and/or sugar, a range of sugar esters can be synthesized. Due to their surface activity and emulsifying capacity, sugar esters are promising for applications in food industry.

  7. Sequential enzymatic epoxidation involved in polyether lasalocid biosynthesis.

    Science.gov (United States)

    Minami, Atsushi; Shimaya, Mayu; Suzuki, Gaku; Migita, Akira; Shinde, Sandip S; Sato, Kyohei; Watanabe, Kenji; Tamura, Tomohiro; Oguri, Hiroki; Oikawa, Hideaki

    2012-05-02

    Enantioselective epoxidation followed by regioselective epoxide opening reaction are the key processes in construction of the polyether skeleton. Recent genetic analysis of ionophore polyether biosynthetic gene clusters suggested that flavin-containing monooxygenases (FMOs) could be involved in the oxidation steps. In vivo and in vitro analyses of Lsd18, an FMO involved in the biosynthesis of polyether lasalocid, using simple olefin or truncated diene of a putative substrate as substrate mimics demonstrated that enantioselective epoxidation affords natural type mono- or bis-epoxide in a stepwise manner. These findings allow us to figure out enzymatic polyether construction in lasalocid biosynthesis. © 2012 American Chemical Society

  8. Modelling and operation of reactors for enzymatic biodiesel production

    DEFF Research Database (Denmark)

    Price, Jason Anthony

    to the production of high fructose corn syrup, upgrading of fats and oils and biodiesel production to name a few. Despite these examples of industrial enzymatic applications, it is still not “clear cut” how to implement biocatalyst in industry and how best to optimize the processes. This is because the processing...... aspects of the enzyme with reaction/reactor engineering is performed. This strategy is applied to a case study of biodiesel production catalysed by a liquid enzyme formulation. The use of enzymes for biodiesel production is still in its infancy with non-optimized process designs. Furthermore is it unclear...

  9. Enzymatic description of the anhydrofructose pathway of glycogen degradation. I

    DEFF Research Database (Denmark)

    Yu, Shukun; Refdahl, Charlotte; Lundt, Inge

    2004-01-01

    The anhydrofructose pathway describes the degradation of glycogen and starch to metabolites via 1,5-anhydro-D-fructose (1,5AnFru). The enzyme catalyzing the first reaction step of this pathway, i.e., a-1,4-glucan lyase (EC 4.2.1.13), has been purified, cloned and characterized from fungi and red...... possessed all enzymes needed for conversion of glycogen to APP, an a-1,4-glucan lyase from this fungus was isolated and partially sequenced. Based on this work, a scheme of the enzymatic description of the anhydrofructose pathway in A. melaloma was proposed. Keywords: Anhydrofructose pathway; Anthracobia...

  10. Enzymatic Dissolution of Biocomposite Solids Consisting of Phosphopeptides to Form Supramolecular Hydrogels

    KAUST Repository

    Shi, Junfeng; Yuan, Dan; Haburcak, Richard; Zhang, Qiang; Zhao, Chao; Zhang, Xixiang; Xu, Bing

    2015-01-01

    Enzyme-catalyzed dephosphorylation is essential for biomineralization and bone metabolism. Here we report the exploration of using enzymatic reaction to transform biocomposites of phosphopeptides and calcium (or strontium) ions to supramolecular hydrogels as a mimic of enzymatic dissolution of biominerals. 31P NMR shows that strong affinity between the phosphopeptides and alkaline metal ions (e.g., Ca2+ or Sr2+) induces the formation of biocomposites as precipitates. Electron microscopy reveals that the enzymatic reaction regulates the morphological transition from particles to nanofibers. Rheology confirms the formation of a rigid hydrogel. As the first example of enzyme-instructed dissolution of a solid to form supramolecular nanofibers/hydrogels, this work provides an approach to generate soft materials with desired properties, expands the application of supramolecular hydrogelators, and offers insights to control the demineralization of calcified soft tissues.

  11. Enzymatic Dissolution of Biocomposite Solids Consisting of Phosphopeptides to Form Supramolecular Hydrogels

    KAUST Repository

    Shi, Junfeng

    2015-10-14

    Enzyme-catalyzed dephosphorylation is essential for biomineralization and bone metabolism. Here we report the exploration of using enzymatic reaction to transform biocomposites of phosphopeptides and calcium (or strontium) ions to supramolecular hydrogels as a mimic of enzymatic dissolution of biominerals. 31P NMR shows that strong affinity between the phosphopeptides and alkaline metal ions (e.g., Ca2+ or Sr2+) induces the formation of biocomposites as precipitates. Electron microscopy reveals that the enzymatic reaction regulates the morphological transition from particles to nanofibers. Rheology confirms the formation of a rigid hydrogel. As the first example of enzyme-instructed dissolution of a solid to form supramolecular nanofibers/hydrogels, this work provides an approach to generate soft materials with desired properties, expands the application of supramolecular hydrogelators, and offers insights to control the demineralization of calcified soft tissues.

  12. Operation variables in transesterification of vegetable oil: an enzymatic catalysis review

    Directory of Open Access Journals (Sweden)

    Andrés Felipe Rojas González

    2010-01-01

    Full Text Available This paper presents the results of a literature review regarding how operating conditions influence vegetable oil enzymatic transesterification yield. The following parameters were studied: temperature and time reaction, alcohol: oil molar ratio, alcohol type, biocatalyst type and concentration, solvent, mixed intensity, reagent purity and free fatty acid and moisture concentration. Yields greater than 90% can be achieved in the enzymatic catalyst of vegetable oil using 35-50°C temperatures, long time reactions (7- 90h and a 3:1alcohol: vegetable oil molar ratio; however, such values would intrinsically depend on the type of lipase and oil u- sed. It was also found that free fatty acid and moisture concentration were parameters which did not require rigorous control due to high enzyme specificity. Lipases immobilised from Pseudomona cepacia bacteria and Rhizopus orizae fungi were most used in vegetable oil enzymatic transesterification.

  13. Lignin from hydrothermally pretreated grass biomass retards enzymatic cellulose degradation by acting as a physical barrier rather than by inducing nonproductive adsorption of enzymes

    DEFF Research Database (Denmark)

    Djajadi, Demi T.; Jensen, Mads M.; Oliveira, Marlene

    2018-01-01

    Lignin is known to hinder efficient enzymatic conversion of lignocellulose in biorefining processes. In particular, nonproductive adsorption of cellulases onto lignin is considered a key mechanism to explain how lignin retards enzymatic cellulose conversion in extended reactions. Lignin-rich resi...

  14. Radical-Mediated Enzymatic Polymerizations

    Science.gov (United States)

    Zavada, Scott R.; Battsengel, Tsatsral; Scott, Timothy F.

    2016-01-01

    Polymerization reactions are commonly effected by exposing monomer formulations to some initiation stimulus such as elevated temperature, light, or a chemical reactant. Increasingly, these polymerization reactions are mediated by enzymes―catalytic proteins―owing to their reaction efficiency under mild conditions as well as their environmental friendliness. The utilization of enzymes, particularly oxidases and peroxidases, for generating radicals via reduction-oxidation mechanisms is especially common for initiating radical-mediated polymerization reactions, including vinyl chain-growth polymerization, atom transfer radical polymerization, thiol–ene step-growth polymerization, and polymerization via oxidative coupling. While enzyme-mediated polymerization is useful for the production of materials intended for subsequent use, it is especially well-suited for in situ polymerizations, where the polymer is formed in the place where it will be utilized. Such polymerizations are especially useful for biomedical adhesives and for sensing applications. PMID:26848652

  15. [Response surface method optimize of nano-silica solid dispersion technology assistant enzymatic hydrolysis preparation genistein].

    Science.gov (United States)

    Jin, Xin; Zhang, Zhen-Hai; Zhu, Jing; Sun, E; Yu, Dan-Hong; Chen, Xiao-Yun; Liu, Qi-Yuan; Ning, Qing; Jia, Xiao-Bin

    2012-04-01

    This article reports that nano-silica solid dispersion technology was used to raise genistein efficiency through increasing the enzymatic hydrolysis rate. Firstly, genistin-nano-silica solid dispersion was prepared by solvent method. And differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) were used to verify the formation of solid dispersion, then enzymatic hydrolysis of solid dispersion was done by snailase to get genistein. With the conversion of genistein as criteria, single factor experiments were used to study the different factors affecting enzymatic hydrolysis of genistin and its solid dispersion. And then, response surface method was used to optimize of nano-silica solid dispersion technology assistant enzymatic hydrolysis. The optimum condition to get genistein through enzymatic hydrolysis of genistin-nano-silica solid dispersion was pH 7.1, temperature 52.2 degrees C, enzyme concentration 5.0 mg x mL(-1) and reaction time 7 h. Under this condition, the conversion of genistein was (93.47 +/- 2.40)%. Comparing with that without forming the genistin-nano-silica solid dispersion, the conversion increased 2.62 fold. At the same time, the product of hydrolysis was purified to get pure genistein. The method of enzymatic hydrolysis of genistin-nano-silica solid dispersion by snailase to obtain genistein is simple, efficiency and suitable for the modern scale production.

  16. Process development for gelatinisation and enzymatic hydrolysis of starch at high concentrations

    NARCIS (Netherlands)

    Baks, T.

    2007-01-01

    cum laude graduation (with distinction) Enzymatic hydrolysis of starch is encountered in day-to-day life for instance in the dishwasher during removal of stains with detergents or in our mouth during chewing of starch-based foods in the presence of saliva. The reaction is also important for the

  17. Ketone Body Acetoacetate Buffers Methylglyoxal via a Non-enzymatic Conversion during Diabetic and Dietary Ketosis

    DEFF Research Database (Denmark)

    Salomon, Trine; Sibbersen, Christian; Hansen, Jakob

    2017-01-01

    now demonstrate that during ketosis, another meta- bolic route is operative via direct non-enzymatic aldol reaction between methylglyoxal and the ke- tone body acetoacetate, leading to 3-hydroxyhex- ane-2,5-dione. This novel metabolite is present at a concentration of 10%–20% of the methylglyoxal...

  18. Chain length distribution and kinetic characteristics of an enzymatically produced polymer

    NARCIS (Netherlands)

    Mulders, K.J.M.; Beeftink, H.H.

    2013-01-01

    Non-processive enzymatic polymerization leads to a distribution of polymer chain lengths. A polymerization model was developed to investigate the relation between the extent of this distribution on one hand, and the polymerization start conditions and reaction kinetics on the other hand. The model

  19. Optimization of Pretreatment and Enzymatic Saccharification of Cogon Grass Prior Ethanol Production

    OpenAIRE

    Jhalique Jane R. Fojas; Ernesto J. Del Rosario

    2013-01-01

    The dilute acid pretreatment and enzymatic saccharification of lignocellulosic substrate, cogon grass (Imperata cylindrical, L.) was optimized prior ethanol fermentation using simultaneous saccharification and fermentation (SSF) method. The optimum pretreatment conditions, temperature, sulfuric acid concentration, and reaction time were evaluated by determining the maximum sugar yield at constant enzyme loading. Cogon grass, at 10% w/v substrate loading, has optimum pretr...

  20. Suppression of acyl migration in enzymatic production of structured lipids through temperature programming

    DEFF Research Database (Denmark)

    Yang, Tiankui; Fruekilde, Maj-Britt; Xu, Xuebing

    2005-01-01

    Acyl migration in the glycerol backbone often leads to the increase of by-products in the enzymatic production of specific structured lipids. Acyl migration is a thermodynamic process and is very difficult to stop fully in actual reactions. The objective of this study was to investigate...

  1. Enzymatic halogenation and oxidation using an alcohol oxidase-vanadium chloroperoxidase cascade

    NARCIS (Netherlands)

    But, Andrada; Noord, Van Aster; Poletto, Francesca; Sanders, Johan P.M.; Franssen, Maurice C.R.; Scott, Elinor L.

    2017-01-01

    The chemo-enzymatic cascade which combines alcohol oxidase from Hansenula polymorpha (AOXHp) with vanadium chloroperoxidase (VCPO), for the production of biobased nitriles from amino acids was investigated. In the first reaction H2O2 (and acetaldehyde) are generated from ethanol and oxygen by AOXHp.

  2. Thermodynamically based solvent design for enzymatic saccharide acylation with hydroxycinnamic acids in non-conventional media

    DEFF Research Database (Denmark)

    Zeuner, Birgitte; Kontogeorgis, Georgios; Riisager, Anders

    2012-01-01

    as well as other enzymatic hydroxycinnamate acylations in ionic liquid systems. The choice of solvent system is highly decisive for enzyme stability, selectivity, and reaction yields in these synthesis reactions. To increase the understanding of the reaction environment and to facilitate solvent screening......-free microemulsions of a hydrocarbon, a polar alcohol, and water are interesting solvent systems because they accommodate different substrate and product solubilities and maintain enzyme stability. Ionic liquids may provide advantages as solvents in terms of increased substrate and product solubility, higher...... of their amphiphilicity and antioxidative potential. Synthetic reactions using mono- or disaccharides as one of the substrates may moreover direct new routes for biomass upgrading in the biorefinery. The paper reviews the available data for enzymatic hydroxycinnamate saccharide ester synthesis in organic solvent systems...

  3. Kinetic study of batch and fed-batch enzymatic saccharification of pretreated substrate and subsequent fermentation to ethanol

    Directory of Open Access Journals (Sweden)

    Gupta Rishi

    2012-03-01

    Full Text Available Abstract Background Enzymatic hydrolysis, the rate limiting step in the process development for biofuel, is always hampered by its low sugar concentration. High solid enzymatic saccharification could solve this problem but has several other drawbacks such as low rate of reaction. In the present study we have attempted to enhance the concentration of sugars in enzymatic hydrolysate of delignified Prosopis juliflora, using a fed-batch enzymatic hydrolysis approach. Results The enzymatic hydrolysis was carried out at elevated solid loading up to 20% (w/v and a comparison kinetics of batch and fed-batch enzymatic hydrolysis was carried out using kinetic regimes. Under batch mode, the actual sugar concentration values at 20% initial substrate consistency were found deviated from the predicted values and the maximum sugar concentration obtained was 80.78 g/L. Fed-batch strategy was implemented to enhance the final sugar concentration to 127 g/L. The batch and fed-batch enzymatic hydrolysates were fermented with Saccharomyces cerevisiae and ethanol production of 34.78 g/L and 52.83 g/L, respectively, were achieved. Furthermore, model simulations showed that higher insoluble solids in the feed resulted in both smaller reactor volume and shorter residence time. Conclusion Fed-batch enzymatic hydrolysis is an efficient procedure for enhancing the sugar concentration in the hydrolysate. Restricting the process to suitable kinetic regimes could result in higher conversion rates.

  4. Kinetic study of batch and fed-batch enzymatic saccharification of pretreated substrate and subsequent fermentation to ethanol

    Science.gov (United States)

    2012-01-01

    Background Enzymatic hydrolysis, the rate limiting step in the process development for biofuel, is always hampered by its low sugar concentration. High solid enzymatic saccharification could solve this problem but has several other drawbacks such as low rate of reaction. In the present study we have attempted to enhance the concentration of sugars in enzymatic hydrolysate of delignified Prosopis juliflora, using a fed-batch enzymatic hydrolysis approach. Results The enzymatic hydrolysis was carried out at elevated solid loading up to 20% (w/v) and a comparison kinetics of batch and fed-batch enzymatic hydrolysis was carried out using kinetic regimes. Under batch mode, the actual sugar concentration values at 20% initial substrate consistency were found deviated from the predicted values and the maximum sugar concentration obtained was 80.78 g/L. Fed-batch strategy was implemented to enhance the final sugar concentration to 127 g/L. The batch and fed-batch enzymatic hydrolysates were fermented with Saccharomyces cerevisiae and ethanol production of 34.78 g/L and 52.83 g/L, respectively, were achieved. Furthermore, model simulations showed that higher insoluble solids in the feed resulted in both smaller reactor volume and shorter residence time. Conclusion Fed-batch enzymatic hydrolysis is an efficient procedure for enhancing the sugar concentration in the hydrolysate. Restricting the process to suitable kinetic regimes could result in higher conversion rates. PMID:22433563

  5. Combined subcritical water and enzymatic hydrolysis for reducing sugar production from coconut husk

    Science.gov (United States)

    Muharja, Maktum; Junianti, Fitri; Nurtono, Tantular; Widjaja, Arief

    2017-05-01

    Coconut husk wastes are abundantly available in Indonesia. It has a potential to be used into alternative renewable energy sources such as hydrogen using enzymatic hydrolysis followed by a fermentation process. Unfortunately, enzymatic hydrolysis is hampered by the complex structure of lignocellulose, so the cellulose component is hard to degrade. In this study, Combined Subcritical Water (SCW) and enzymatic hydrolysis are applied to enhance fermentable, thereby reducing production of sugar from coconut husk. There were two steps in this study, the first step was coconut husk pretreated by SCW in batch reactor at 80 bar and 150-200°C for 60 minutes reaction time. Secondly, solid fraction from the results of SCW was hydrolyzed using the mixture of pure cellulose and xylanase enzymes. Analysis was conducted on untreated and SCW-treated by gravimetric assay, liquid fraction after SCW and solid fraction after enzymatic hydrolysis using DNS assay. The maximum yield of reducing sugar (including xylose, arabinose glucose, galactose, mannose) was 1.254 gr per 6 gr raw material, representing 53.95% of total sugar in coconut husk biomass which was obtained at 150°C 80 bar for 60 minutes reaction time of SCW-treated and 6 hour of enzymatic hydrolysis using mixture of pure cellulose and xylanase enzymes (18.6 U /gram of coconut husk).

  6. Reaction Decoder Tool (RDT): extracting features from chemical reactions.

    Science.gov (United States)

    Rahman, Syed Asad; Torrance, Gilliean; Baldacci, Lorenzo; Martínez Cuesta, Sergio; Fenninger, Franz; Gopal, Nimish; Choudhary, Saket; May, John W; Holliday, Gemma L; Steinbeck, Christoph; Thornton, Janet M

    2016-07-01

    Extracting chemical features like Atom-Atom Mapping (AAM), Bond Changes (BCs) and Reaction Centres from biochemical reactions helps us understand the chemical composition of enzymatic reactions. Reaction Decoder is a robust command line tool, which performs this task with high accuracy. It supports standard chemical input/output exchange formats i.e. RXN/SMILES, computes AAM, highlights BCs and creates images of the mapped reaction. This aids in the analysis of metabolic pathways and the ability to perform comparative studies of chemical reactions based on these features. This software is implemented in Java, supported on Windows, Linux and Mac OSX, and freely available at https://github.com/asad/ReactionDecoder : asad@ebi.ac.uk or s9asad@gmail.com. © The Author 2016. Published by Oxford University Press.

  7. Nanocrystal Bioassembly: Asymmetry, Proximity, and Enzymatic Manipulation

    Energy Technology Data Exchange (ETDEWEB)

    Claridge, Shelley A. [Univ. of California, Berkeley, CA (United States)

    2008-05-01

    Research at the interface between biomolecules and inorganic nanocrystals has resulted in a great number of new discoveries. In part this arises from the synergistic duality of the system: biomolecules may act as self-assembly agents for organizing inorganic nanocrystals into functional materials; alternatively, nanocrystals may act as microscopic or spectroscopic labels for elucidating the behavior of complex biomolecular systems. However, success in either of these functions relies heavily uponthe ability to control the conjugation and assembly processes.In the work presented here, we first design a branched DNA scaffold which allows hybridization of DNA-nanocrystal monoconjugates to form discrete assemblies. Importantly, the asymmetry of the branched scaffold allows the formation of asymmetric2assemblies of nanocrystals. In the context of a self-assembled device, this can be considered a step toward the ability to engineer functionally distinct inputs and outputs.Next we develop an anion-exchange high performance liquid chromatography purification method which allows large gold nanocrystals attached to single strands of very short DNA to be purified. When two such complementary conjugates are hybridized, the large nanocrystals are brought into close proximity, allowing their plasmon resonances to couple. Such plasmon-coupled constructs are of interest both as optical interconnects for nanoscale devices and as `plasmon ruler? biomolecular probes.We then present an enzymatic ligation strategy for creating multi-nanoparticle building blocks for self-assembly. In constructing a nanoscale device, such a strategy would allow pre-assembly and purification of components; these constructs can also act as multi-label probes of single-stranded DNA conformational dynamics. Finally we demonstrate a simple proof-of-concept of a nanoparticle analog of the polymerase chain reaction.

  8. Ultrafast Excited-State Dynamics of Diketopyrrolopyrrole (DPP)-Based Materials: Static versus Diffusion-Controlled Electron Transfer Process

    KAUST Repository

    Alsulami, Qana

    2015-06-25

    Singlet-to-triplet intersystem crossing (ISC) and photoinduced electron transfer (PET) of platinum(II) containing diketopyrrolopyrrole (DPP) oligomer in the absence and presence of strong electron-acceptor tetracyanoethylene (TCNE) were investigated using femtosecond and nanosecond transient absorption spectroscopy with broadband capabilities. The role of platinum(II) incorporation in those photophysical properties was evaluated by comparing the excited-state dynamics of DPP with and without the metal centers. The steady-state measurements reveal that platinum(II) incorporation facilitates dramatically the interactions between DPP-Pt(acac) and TCNE, resulting in charge transfer (CT) complex formation. The transient absorption spectra in the absence of TCNE reveal ultrafast ISC of DPP-Pt(acac) followed by their long-lived triplet state. In the presence of TCNE, PET from the excited DPP-Pt(acac) and DPP to TCNE, forming the radical ion pairs. The ultrafast PET which occurs statically from DPP-Pt(acac) to TCNE in picosecond regime, is much faster than that from DPP to TCNE (nanosecond time scale) which is diffusion-controlled process, providing clear evidence that PET rate is eventually controlled by the platinum(II) incorporation.

  9. Diffusion-controlled oxygen reduction on multi-copper oxidase-adsorbed carbon aerogel electrodes without mediator

    Energy Technology Data Exchange (ETDEWEB)

    Tsujimura, S.; Kamitaka, Y.; Kano, K. [Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto (Japan)

    2007-12-15

    Bioelectrocatalytic reduction of O{sub 2} into water was archived at diffusion-controlled rate by using enzymes (laccase from Trametes sp. and bilirubin oxidase from Myrothecium verrucaria, which belong to the family of multi-copper oxidase) adsorbed on mesoporous carbon aerogel particle without a mediator. The current density was predominantly controlled by the diffusion of dissolved O{sub 2} in rotating-disk electrode experiments, and reached a value as large as 10 mA cm{sup -2} at 1 atm O{sub 2}, 25 C, and 8,000 rpm on the laccase-adsorbed electrode. The overpotential of the bioelectrocatalytic reduction of O{sub 2} was 0.4-0.55 V smaller than that observed on a Pt disk electrode. Without any optimization, the laccase-adsorbed biocathode showed stable current intensity of the O{sub 2} reduction in an air-saturated buffer at least for 10 days under continuous flow system. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  10. Ultrafast Excited-State Dynamics of Diketopyrrolopyrrole (DPP)-Based Materials: Static versus Diffusion-Controlled Electron Transfer Process

    KAUST Repository

    Alsulami, Qana; Aly, Shawkat Mohammede; Goswami, Subhadip; Alarousu, Erkki; Usman, Anwar; Schanze, Kirk S.; Mohammed, Omar F.

    2015-01-01

    Singlet-to-triplet intersystem crossing (ISC) and photoinduced electron transfer (PET) of platinum(II) containing diketopyrrolopyrrole (DPP) oligomer in the absence and presence of strong electron-acceptor tetracyanoethylene (TCNE) were investigated using femtosecond and nanosecond transient absorption spectroscopy with broadband capabilities. The role of platinum(II) incorporation in those photophysical properties was evaluated by comparing the excited-state dynamics of DPP with and without the metal centers. The steady-state measurements reveal that platinum(II) incorporation facilitates dramatically the interactions between DPP-Pt(acac) and TCNE, resulting in charge transfer (CT) complex formation. The transient absorption spectra in the absence of TCNE reveal ultrafast ISC of DPP-Pt(acac) followed by their long-lived triplet state. In the presence of TCNE, PET from the excited DPP-Pt(acac) and DPP to TCNE, forming the radical ion pairs. The ultrafast PET which occurs statically from DPP-Pt(acac) to TCNE in picosecond regime, is much faster than that from DPP to TCNE (nanosecond time scale) which is diffusion-controlled process, providing clear evidence that PET rate is eventually controlled by the platinum(II) incorporation.

  11. Production of resistant starch by enzymatic debranching in legume flours.

    Science.gov (United States)

    Morales-Medina, Rocío; Del Mar Muñío, María; Guadix, Emilia M; Guadix, Antonio

    2014-01-30

    Resistant starch (RS) was produced by enzymatic hydrolysis of flours from five different legumes: lentil, chickpea, faba bean, kidney bean and red kidney bean. Each legume was firstly treated thermally, then hydrolyzed with pullulanase for 24h at 50°C and pH 5 and lyophilized. At the end of each hydrolysis reaction, the RS amount ranged from 4.7% for red kidney beans to 7.5% for chickpeas. With respect to the curves of RS against hydrolysis time, a linear increase was observed initially and a plateau was generally achieved by the end of reaction. These curves were successfully modeled by a kinetic equation including three parameters: initial RS, RS at long operation time and a kinetic constant (k). Furthermore, the relative increase in hydrolysis, calculated using the kinetic parameters, was successfully correlated to the percentage of amylose. Copyright © 2013 Elsevier Ltd. All rights reserved.

  12. Enzymatic synthesis of C-11 formaldehyde: concise communication

    International Nuclear Information System (INIS)

    Slegers, G.; Lambrecht, R.H.D.; Vandewalle, T.; Meulewaeter, L.; Vandecasteele, C.

    1984-01-01

    An enzymatic synthesis of C-11 formaldehyde from C-11 methanol is presented, with immobilized alcohol oxidase and catalase: a rapid, simple procedure, with a high and reproducible yield. Carbon-11 methanol is oxidized to C-11 formaldehyde by passage over a column on which the enzymes alcohol oxidase and catalase are immobilized. The catalase increases reaction velocity by recycling the oxygen, and prevents destruction of the alcohol oxidase by eliminating the excess of hydrogen peroxide. The yield of the enzyme-catalyzed oxidation was 80-95%. A specific activity of 400-450 mCi/μmole was obtained at EOB + 20 min. Various immobilization techniques and the optimal reaction conditions of the immobilized enzymes are investigated

  13. Green enzymatic production of glyceryl monoundecylenate using immobilized Candida antarctica lipase B.

    Science.gov (United States)

    Yadav, Manish G; Kavadia, Monali R; Vadgama, Rajeshkumar N; Odaneth, Annamma A; Lali, Arvind M

    2017-11-26

    Enzymatic synthesis of glyceryl monoundecylenate (GMU) was performed using indigenously immobilized Candida anatarctica lipase B preparation (named as PyCal) using glycerol and undecylenic acid as substrates. The effect of molar ratio, enzyme load, reaction time, and organic solvent on the reaction conversion was determined. Both batch and continuous processes for GMU synthesis with shortened reaction time were developed. Under optimized batch reaction conditions such as 1:5 molar ratio of undecylenic acid and glycerol, 2 h of reaction time at 30% substrate concentration in tert-butyl alcohol, conversion of 82% in the absence of molecular sieve, and conversion of 93% in the presence of molecular sieve were achieved. Packed bed reactor studies resulted in high conversion of 86% in 10-min residence time. Characterization of formed GMU was performed by FTIR, MS/MS. Enzymatic process resulted in GMU as a predominant product in high yield and shorter reaction time periods with GMU content of 92% and DAG content of 8%. Optimized GMU synthesis in the present study can be used as a useful reference for industrial synthesis of fatty acid esters of glycerol by the enzymatic route.

  14. Detection of extracellular enzymatic activity in microorganisms ...

    African Journals Online (AJOL)

    sunny t

    2015-09-18

    Sep 18, 2015 ... microorganisms with all three enzymatic activities, thereby establishing these techniques as ... supplemented at 1% with vegetable oils, including olive (OLI) ..... cepacia lipase for biodiesel fuel production from soybean oil.

  15. Electrochemical, Chemical and Enzymatic Oxidations of Phenothiazines

    NARCIS (Netherlands)

    Blankert, B.; Hayen, H.; van Leeuwen, S.M.; Karst, U.; Bodoki, E.; Lotrean, S.; Sandulescu, R.; Mora Diaz, N.; Dominguez, O.; Arcos, J.; Kauffmann, J.-M.

    2005-01-01

    The oxidation of several phenothiazine drugs (phenothiazine, promethazine hydrochloride, promazine hydrochloride, trimeprazine hydrochloride and ethopropazine hydrochloride) has been carried out in aqueous acidic media by electrochemical, chemical and enzymatic methods. The chemical oxidation was

  16. Detection of extracellular enzymatic activity in microorganisms ...

    African Journals Online (AJOL)

    Detection of extracellular enzymatic activity in microorganisms isolated from waste vegetable oil contaminated soil using plate methodologies. Eugenia G. Ortiz Lechuga, Isela Quintero Zapata, Katiushka Arévalo Niño ...

  17. Enzymatic hydrolysis of plant extracts containing inulin

    Energy Technology Data Exchange (ETDEWEB)

    Guiraud, J.P.; Galzy, P.

    1981-10-01

    Inulin-rich extracts of chicory and Jerusalem artichoke are a good potential source of fructose. Total enzymatic hydrolysis of these extracts can be effected by yeast inulinases (EC 3.2.1.7). Chemical prehydrolysis is unfavourable. Enzymatic hydrolysis has advantages over chemical hydrolysis: it does not produce a dark-coloured fraction or secondary substances. It is possible to envisage the preparation of high fructose syrups using this process. (Refs. 42).

  18. Kinetics of enzymatic hydrolysis of methyl ricinoleate

    OpenAIRE

    Neeharika, T. S.V.R.; Lokesh, P.; Prasanna Rani, K. N.; Prathap Kumar, T.; Prasad, R. B.N.

    2015-01-01

    Ricinoleic acid is an unsaturated hydroxy fatty acid that naturally occurs in castor oil in proportions of up to 85–90%. Ricinoleic acid is a potential raw material and finds several applications in coatings, lubricant formulations and pharmaceutical areas. Enzymatic hydrolysis of castor oil is preferred over conventional hydrolysis for the preparation of ricinoleic acid to avoid estolide formation. A kinetics analysis of the enzymatic hydrolysis of Methyl Ricinoleate in the presence of Candi...

  19. New eutectic ionic liquids for lipase activation and enzymatic preparation of biodiesel†

    Science.gov (United States)

    Zhao, Hua; Baker, Gary A.; Holmes, Shaletha

    2012-01-01

    The enzymatic preparation of biodiesel has been hampered by the lack of suitable solvents with desirable properties such as high lipase compatibility, low cost, low viscosity, high biodegradability, and ease of product separation. Recent interest in using ionic liquids (ILs) as advanced reaction media has led to fast reaction rates and high yields in the enzymatic synthesis of biodiesel. However, conventional (i.e., cation–anion paired) ILs based on imidazolium and other quaternary ammonium salts remain too expensive for wide application at industrial scales. In this study, we report on newly-synthesized eutectic ILs derived from choline acetate or choline chloride coupled with biocompatible hydrogen-bond donors, such as glycerol. These eutectic solvents have favorable properties including low viscosity, high biodegradability, and excellent compatibility with Novozym® 435, a commercial immobilized Candida antarctica lipase B. Furthermore, in a model biodiesel synthesis system, we demonstrate high reaction rates for the enzymatic transesterification of Miglyol® oil 812 with methanol, catalyzed by Novozym® 435 in choline acetate/glycerol (1 : 1.5 molar ratio). The high conversion (97%) of the triglyceride obtained within 3 h, under optimal conditions, suggests that these novel eutectic solvents warrant further exploration as potential media in the enzymatic production of biodiesel. PMID:21283901

  20. Laboratory-scale method for enzymatic saccharification of lignocellulosic biomass at high-solids loadings

    Directory of Open Access Journals (Sweden)

    Dibble Clare J

    2009-11-01

    Full Text Available Abstract Background Screening new lignocellulosic biomass pretreatments and advanced enzyme systems at process relevant conditions is a key factor in the development of economically viable lignocellulosic ethanol. Shake flasks, the reaction vessel commonly used for screening enzymatic saccharifications of cellulosic biomass, do not provide adequate mixing at high-solids concentrations when shaking is not supplemented with hand mixing. Results We identified roller bottle reactors (RBRs as laboratory-scale reaction vessels that can provide adequate mixing for enzymatic saccharifications at high-solids biomass loadings without any additional hand mixing. Using the RBRs, we developed a method for screening both pretreated biomass and enzyme systems at process-relevant conditions. RBRs were shown to be scalable between 125 mL and 2 L. Results from enzymatic saccharifications of five biomass pretreatments of different severities and two enzyme preparations suggest that this system will work well for a variety of biomass substrates and enzyme systems. A study of intermittent mixing regimes suggests that mass transfer limitations of enzymatic saccharifications at high-solids loadings are significant but can be mitigated with a relatively low amount of mixing input. Conclusion Effective initial mixing to promote good enzyme distribution and continued, but not necessarily continuous, mixing is necessary in order to facilitate high biomass conversion rates. The simplicity and robustness of the bench-scale RBR system, combined with its ability to accommodate numerous reaction vessels, will be useful in screening new biomass pretreatments and advanced enzyme systems at high-solids loadings.

  1. Quantitation of Na+, K+-atpase Enzymatic Activity in Tissues of the Mammalian Vestibular System

    Science.gov (United States)

    Kerr, T. P.

    1985-01-01

    In order to quantify vestibular Na(+), K(+)-ATPase, a microassay technique was developed which is sufficiently sensitive to measure the enzymatic activity in tissue from a single animal. The assay was used to characterize ATPase in he vestibular apparatus of the Mongolian gerbil. The quantitative procedure employs NPP (5 mM) as synthetic enzyme substrate. The assay relies upon spectrophotometric measurement (410 nm) of nitrophenol (NP) released by enzymatic hydrolysis of the substrate. Product formation in the absence of ouabain reflects both specific (Na(+), K(+)-ATPase) and non-specific (Mg(++)-ATPase) enzymatic activity. By measuring the accumulation of reaction product (NP) at three-minute intervals during the course of incubation, it is found that the overall enzymatic reaction proceeds linearly for at least 45 minutes. It is therefore possible to determine two separate reaction rates from a single set of tissues. Initial results indicate that total activity amounts to 53.3 + or - 11.2 (S.E.M.) nmol/hr/mg dry tissue, of which approximately 20% is ouabain-sensitive.

  2. Peclet number as affected by molecular diffusion controls transient anomalous transport in alluvial aquifer-aquitard complexes

    Science.gov (United States)

    Zhang, Yong; Green, Christopher T.; Tick, Geoffrey R.

    2015-01-01

    This study evaluates the role of the Peclet number as affected by molecular diffusion in transient anomalous transport, which is one of the major knowledge gaps in anomalous transport, by combining Monte Carlo simulations and stochastic model analysis. Two alluvial settings containing either short- or long-connected hydrofacies are generated and used as media for flow and transport modeling. Numerical experiments show that 1) the Peclet number affects both the duration of the power-law segment of tracer breakthrough curves (BTCs) and the transition rate from anomalous to Fickian transport by determining the solute residence time for a given low-permeability layer, 2) mechanical dispersion has a limited contribution to the anomalous characteristics of late-time transport as compared to molecular diffusion due to an almost negligible velocity in floodplain deposits, and 3) the initial source dimensions only enhance the power-law tail of the BTCs at short travel distances. A tempered stable stochastic (TSS) model is then applied to analyze the modeled transport. Applications show that the time-nonlocal parameters in the TSS model relate to the Peclet number, Pe. In particular, the truncation parameter in the TSS model increases nonlinearly with a decrease in Pe due to the decrease of the mean residence time, and the capacity coefficient increases with an increase in molecular diffusion which is probably due to the increase in the number of immobile particles. The above numerical experiments and stochastic analysis therefore reveal that the Peclet number as affected by molecular diffusion controls transient anomalous transport in alluvial aquifer–aquitard complexes.

  3. Effect and Modeling of Glucose Inhibition and In Situ Glucose Removal During Enzymatic Hydrolysis of Pretreated Wheat Straw

    DEFF Research Database (Denmark)

    Andric, Pavle; Meyer, Anne S.; Jensen, Peter Arendt

    2010-01-01

    The enzymatic hydrolysis of lignocellulosic biomass is known to be product-inhibited by glucose. In this study, the effects on cellulolytic glucose yields of glucose inhibition and in situ glucose removal were examined and modeled during extended treatment of heat-pretreated wheat straw......, during 96 h of reaction. When glucose was removed by dialysis during the enzymatic hydrolysis, the cellulose conversion rates and glucose yields increased. In fact, with dialytic in situ glucose removal, the rate of enzyme-catalyzed glucose release during 48-72 h of reaction recovered from 20......-40% to become approximate to 70% of the rate recorded during 6-24 h of reaction. Although Michaelis-Menten kinetics do not suffice to model the kinetics of the complex multi-enzymatic degradation of cellulose, the data for the glucose inhibition were surprisingly well described by simple Michaelis...

  4. Chemo‐enzymatic epoxidation–process options for improving biocatalytic productivity

    DEFF Research Database (Denmark)

    Hagström, Anna E. V.; Törnvall, Ulrika; Nordblad, Mathias

    2011-01-01

    The reactor choice is crucial when designing a process where inactivation of the biocatalyst is a problem. The main bottleneck for the chemo‐enzymatic epoxidation has been found to be enzyme inactivation by the hydrogen peroxide, H2O2, substrate. In the work reported here, the effect of reaction...... parameters on the reaction performance have been investigated and used to establish suitable operating strategies to minimize the inactivation of the enzyme, using rapeseed methyl ester (RME) as a substrate in a solvent‐free system. The use of a controlled fed‐batch reactor for maintaining H2O2 concentration...... at 1.5 M resulted in increased productivity, up to 76 grams of product per gram of biocatalyst with higher retention of enzyme activity. Further investigation included a multistage design that separated the enzymatic reaction and the saturation of the RME substrate with H2O2 into different vessels...

  5. An investigation of nitrile transforming enzymes in the chemo-enzymatic synthesis of the taxol sidechain.

    Science.gov (United States)

    Wilding, Birgit; Veselá, Alicja B; Perry, Justin J B; Black, Gary W; Zhang, Meng; Martínková, Ludmila; Klempier, Norbert

    2015-07-28

    Paclitaxel (taxol) is an antimicrotubule agent widely used in the treatment of cancer. Taxol is prepared in a semisynthetic route by coupling the N-benzoyl-(2R,3S)-3-phenylisoserine sidechain to the baccatin III core structure. Precursors of the taxol sidechain have previously been prepared in chemoenzymatic approaches using acylases, lipases, and reductases, mostly featuring the enantioselective, enzymatic step early in the reaction pathway. Here, nitrile hydrolysing enzymes, namely nitrile hydratases and nitrilases, are investigated for the enzymatic hydrolysis of two different sidechain precursors. Both sidechain precursors, an openchain α-hydroxy-β-amino nitrile and a cyanodihydrooxazole, are suitable for coupling to baccatin III directly after the enzymatic step. An extensive set of nitrilases and nitrile hydratases was screened towards their activity and selectivity in the hydrolysis of two taxol sidechain precursors and their epimers. A number of nitrilases and nitrile hydratases converted both sidechain precursors and their epimers.

  6. Development and Validation of an Enzymatic Method To Determine Stevioside Content from Stevia rebaudiana.

    Science.gov (United States)

    Udompaisarn, Somsiri; Arthan, Dumrongkiet; Somana, Jamorn

    2017-04-19

    An enzymatic method for specific determination of stevioside content was established. Recombinant β-glucosidase BT_3567 (rBT_3567) from Bacteroides thetaiotaomicron HB-13 exhibited selective hydrolysis of stevioside at β-1,2-glycosidic bond to yield rubusoside and glucose. Coupling of this enzyme with glucose oxidase and peroxidase allowed for quantitation of stevioside content in Stevia samples by using a colorimetric-based approach. The series of reactions for stevioside determination can be completed within 1 h at 37 °C. Stevioside determination using the enzymatic assay strongly correlated with results obtained from HPLC quantitation (r 2 = 0.9629, n = 16). The percentages of coefficient variation (CV) of within day (n = 12) and between days (n = 12) assays were lower than 5%, and accuracy ranges were 95-105%. This analysis demonstrates that the enzymatic method developed in this study is specific, easy to perform, accurate, and yields reproducible results.

  7. Optimal information transfer in enzymatic networks: A field theoretic formulation

    Science.gov (United States)

    Samanta, Himadri S.; Hinczewski, Michael; Thirumalai, D.

    2017-07-01

    Signaling in enzymatic networks is typically triggered by environmental fluctuations, resulting in a series of stochastic chemical reactions, leading to corruption of the signal by noise. For example, information flow is initiated by binding of extracellular ligands to receptors, which is transmitted through a cascade involving kinase-phosphatase stochastic chemical reactions. For a class of such networks, we develop a general field-theoretic approach to calculate the error in signal transmission as a function of an appropriate control variable. Application of the theory to a simple push-pull network, a module in the kinase-phosphatase cascade, recovers the exact results for error in signal transmission previously obtained using umbral calculus [Hinczewski and Thirumalai, Phys. Rev. X 4, 041017 (2014), 10.1103/PhysRevX.4.041017]. We illustrate the generality of the theory by studying the minimal errors in noise reduction in a reaction cascade with two connected push-pull modules. Such a cascade behaves as an effective three-species network with a pseudointermediate. In this case, optimal information transfer, resulting in the smallest square of the error between the input and output, occurs with a time delay, which is given by the inverse of the decay rate of the pseudointermediate. Surprisingly, in these examples the minimum error computed using simulations that take nonlinearities and discrete nature of molecules into account coincides with the predictions of a linear theory. In contrast, there are substantial deviations between simulations and predictions of the linear theory in error in signal propagation in an enzymatic push-pull network for a certain range of parameters. Inclusion of second-order perturbative corrections shows that differences between simulations and theoretical predictions are minimized. Our study establishes that a field theoretic formulation of stochastic biological signaling offers a systematic way to understand error propagation in

  8. Enzymatic Hydrolysis of Pretreated Fibre Pressed Oil Palm Frond by using Sacchariseb C6

    Science.gov (United States)

    Hashim, F. S.; Yussof, H. W.; Zahari, M. A. K. M.; Rahman, R. A.; Illias, R. M.

    2017-06-01

    Enzymatic hydrolysis becomes a prominent technology for conversion of cellulosic biomass to its glucose monomers that requires an action of cellulolytic enzymes in a sequential and synergistic manner. In this study, the effect of agitation speed, glucan loading, enzyme loading, temperature and reaction time on the production of glucose from fibre pressed oil palm frond (FPOPF) during enzymatic hydrolysis was screened by a half factorial design 25-1 using Response Surface Methodology (RSM). The FPOPF sample was first delignified by alkaline pretreatment at 4.42 (w/v) sodium hydroxide for an hour prior to enzymatic hydrolysis using commercial cellulase enzyme, Sacchariseb C6. The effect of enzymatic hydrolysis on the structural of FPOPF has been evaluated by Scanning Electron Microscopy (SEM) analysis. Characterization of raw FPOPF comprised of 4.5 extractives, 40.7 glucan, 26.1 xylan, 26.2 lignin and 1.8 ash, whereas for pretreated FPOPF gave 0.3 extractives, 61.4 glucan, 20.4 xylan, 13.3 lignin and 1.3 ash. From this study, it was found that the best enzymatic hydrolysis condition yielded 33.01 ± 0.73 g/L of glucose when performed at 200 rpm of agitation speed, 60 FPU/mL of enzyme loading, 4 (w/w) of glucan loading, temperature at 55 □ and 72 hours of reaction time. The model obtained was significant with p-value enzymatic hydrolysis from pretreated FPOPF produce high amount of glucose that enhances it potential for industrial application. This glucose can be further used to produce high-value products.

  9. Methods for determining enzymatic activity comprising heating and agitation of closed volumes

    Science.gov (United States)

    Thompson, David Neil; Henriksen, Emily DeCrescenzo; Reed, David William; Jensen, Jill Renee

    2016-03-15

    Methods for determining thermophilic enzymatic activity include heating a substrate solution in a plurality of closed volumes to a predetermined reaction temperature. Without opening the closed volumes, at least one enzyme is added, substantially simultaneously, to the closed volumes. At the predetermined reaction temperature, the closed volumes are agitated and then the activity of the at least one enzyme is determined. The methods are conducive for characterizing enzymes of high-temperature reactions, with insoluble substrates, with substrates and enzymes that do not readily intermix, and with low volumes of substrate and enzyme. Systems for characterizing the enzymes are also disclosed.

  10. Enzymatic biodiesel production: Technical and economical considerations

    DEFF Research Database (Denmark)

    Munk Nielsen, Per; Brask, Jesper; Fjerbæk, Lene

    2008-01-01

    It is well documented in the literature that enzymatic processing of oils and fats for biodiesel is technically feasible. However, with very few exceptions, enzyme technology is not currently used in commercial-scale biodiesel production. This is mainly due to non-optimized process design...... and a lack of available costeffective enzymes. The technology to re-use enzymes has typically proven insufficient for the processes to be competitive. However, literature data documenting the productivity of enzymatic biodiesel together with the development of new immobilization technology indicates...... that enzyme catalysts can become cost effective compared to chemical processing. This work reviews the enzymatic processing of oils and fats into biodiesel with focus on process design and economy....

  11. Operation and Control of Enzymatic Biodiesel Production

    DEFF Research Database (Denmark)

    Price, Jason Anthony; Huusom, Jakob Kjøbsted; Nordblad, Mathias

    This work explores the control of biodiesel production via an enzymatic catalyst. The process involves the transesterification of oils/fats with an alcohol (usually methanol or ethanol), using enzymatic catalysts to generate mono-alkyl esters (the basis of biodiesel) and glycerol as by......-product. Current literature indicates that enzymatic processing of oils and fats to produce biodiesel is technically feasible and developments in immobilization technology indicate that enzyme catalysts can become cost effective compared to chemical processing. However, with very few exceptions, enzyme technology...... is not currently used in commercial-scale biodiesel production. This is mainly due to non-optimized process designs, which do not use the full potential of the catalysts in a cost-efficient way. Furthermore is it unclear what process variables need to be monitored and controlled to ensure optimal economics...

  12. A Factorial Analysis Study on Enzymatic Hydrolysis of Fiber Pressed Oil Palm Frond for Bioethanol Production

    Science.gov (United States)

    Hashim, F. S.; Yussof, H. W.; Zahari, M. A. K. M.; Illias, R. M.; Rahman, R. A.

    2016-03-01

    Different technologies have been developed to for the conversion of lignocellulosic biomass to suitable fermentation substrates for bioethanol production. The enzymatic conversion of cellulose seems to be the most promising technology as it is highly specific and does not produce substantial amounts of unwanted byproducts. The effects of agitation speed, enzyme loading, temperature, pH and reaction time on the conversion of glucose from fiber pressed oil palm frond (FPOPF) for bioethanol production were screened by statistical analysis using response surface methodology (RSM). A half fraction two-level factorial analysis with five factors was selected for the experimental design to determine the best enzymatic conditions that produce maximum amount of glucose. FPOPF was pre-treated with alkaline prior to enzymatic hydrolysis. The enzymatic hydrolysis was performed using a commercial enzyme Cellic CTec2. From this study, the highest yield of glucose concentration was 9.736 g/L at 72 hours reaction time at 35 °C, pH 5.6, and 1.5% (w/v) of enzyme loading. The model obtained was significant with p-value model had a maximum point which is likely to be the optimum point and possible for the optimization process.

  13. Kinetic study of enzymatic hydrolysis of acid-pretreated coconut coir

    Science.gov (United States)

    Fatmawati, Akbarningrum; Agustriyanto, Rudy

    2015-12-01

    Biomass waste utilization for biofuel production such as bioethanol, has become more prominent currently. Coconut coir is one of lignocellulosic food wastes, which is abundant in Indonesia. Bioethanol production from such materials consists of more than one step. Pretreatment and enzymatic hydrolysis is crucial steps to produce sugar which can then be fermented into bioethanol. In this research, ground coconut coir was pretreated using dilute sulfuric acid at 121°C. This pretreatment had increased the cellulose content and decreased the lignin content of coconut coir. The pretreated coconut coir was hydrolyzed using a mix of two commercial cellulase enzymes at pH of 4.8 and temperature of 50°C. The enzymatic hydrolysis was conducted at several initial coconut coir slurry concentrations (0.1-2 g/100 mL) and reaction times (2-72 hours). The reducing sugar concentration profiles had been produced and can be used to obtain reaction rates. The highest reducing sugar concentration obtained was 1,152.567 mg/L, which was produced at initial slurry concentration of 2 g/100 mL and 72 hours reaction time. In this paper, the reducing sugar concentrations were empirically modeled as a function of reaction time using power equations. Michaelis-Menten kinetic model for enzymatic hydrolysis reaction is adopted. The kinetic parameters of that model for sulfuric acid-pretreated coconut coir enzymatic hydrolysis had been obtained which are Vm of 3.587×104 mg/L.h, and KM of 130.6 mg/L.

  14. Kinetic study of enzymatic hydrolysis of potato starch

    Directory of Open Access Journals (Sweden)

    Óscar Fernando Castellanos Domínguez

    2004-01-01

    Full Text Available This article describes the kinetic study of potato starch enzymatic hydrolysis using soluble enzymes (Novo Nordisk. Different assays divided into four groups were used: reaction time (with which it was possible to reduce the 48-72 hour duration reported in the literature to 16 hours with comparable productivity levels; selecting the set of enzymes to be used (different types were evaluated - BAN and Termamyl as alfa-amylases during dextrinisation stage, and AMG, Promozyme and Fungamyl for sacarification reaction- identifying those presenting the best performance during hydrolysis.Reaction conditions were optimised for the process's two stages (destrinisation and sacarification. Enzyme dose, calcium cofactor concentration, pH, temperature and agitation speed were studied for the first stage. Enzyme ratio, pH and agitation speed were studied for sacarification; the latter parameter reported values having no antecedents in the literature (60 rpm and 30 rpm for first and second reactions, respectively. Michaelis Menten kinetics were calculated once conditions had been optimised, varying substrate from 10-50% P/V, obtaining km and Vmax kinetic parameters for each reaction. A kinetic model was found according to local working conditions which was able to explain potato starch conversion to glucose syrup, achieving 96 dextrose equivalents by the end of the reaction, being well within the maximum range reported in the literature (94-98.Laboratory equipment was constructed prior to carrying out assays which was able to reproduce and improve the conditions reported in the literature, making it a useful, reliable tool for use in assays returning good results.

  15. Enzymatic activity of the cellulolytic complex produced by trichoderma reesei. Enzymatic hydrolysis of cellulose

    International Nuclear Information System (INIS)

    Alfonsel Jaen, M.; Negro, M.J.; Saez, R.; Martin Moreno, C.

    1986-01-01

    The enzymatic activity characterization of the cellulolytic complex obtained from Trichoderma reese QM 9414 and the influence of the enzymatic hydrolysis conditions on the hydrolysis yield are studied. Pure cellulose and native or alkali pretreated biomass from Onopordum nervosum have been used as substrates. The values of pH, temperature, substrate concentration and enzyme-substrate ratio for the optimum activity of that complex, evaluated as glucose and reducing sugars productions, have been selected. Previous studies on enzymatic hydrolysis of O. nervosum have shown a remarkable effect of the alkaline pretreatments on the final hydrolysis yield. (author). 10 figs.; 10 refs

  16. Enzymatic activity of the cellulolytic complex produced by Trichoderma reesei. Enzymatic hydrolysis of cellulose

    International Nuclear Information System (INIS)

    Alfonsel J, M.; Negro A, M. J.; Saez A, R.; Martin M, C.

    1986-01-01

    The enzymatic activity characterization of the cellulolytic complex obtained from Trichoderma reesei QM 9414 and the influence of the enzymatic hydrolysis conditions on the hydrolysis yield are studied. Pure cellulose and native or alkali pretreated biomass Onopordum nervosum have been used as substrates. The values of pH, temperature, substrate concentration and enzyme-substrate ratio for the optimum activity of that complex, evaluated as glucose and reducing sugars production, have been selected. Previous studies on enzymatic hydrolysis of 0. nervosum have shown a remarkable effect of the alkaline pretreatments on the final hydrolysis yield. (Author) 10 refs

  17. Functional bio-based polyesters by enzymatic polymerization

    DEFF Research Database (Denmark)

    Daugaard, Anders Egede; Hoffmann, Christian; Andersen, Christian

    During recent years enzymatic polymerization has become increasingly popular as an alternative to classical polyesterification processes. The high regioselectivity observed for lipases permits preparation of novel polyesters with a high number of functional groups.1 This is particularly interesting...... polymerization was applied to prepare functional water soluble polyesters based on dimethyl itaconate and poly(ethyleneglycol).2 The monomer permits postfunctionalization using thiol-ene chemistry or aza-michael additions, which was used to illustrate the possibilites of preparing functional hydrogels. Hydrogels...... based on the polyesters were shown to be degradable and could be prepared either from the pure polyester or from prefunctionalized polyesters, though the thiol-ene reactions were found to be less effective. Since then a new monomer, trans-2,5-dihydroxy-3-pentenoic acid methyl ester (DPM) has been...

  18. Reactions of melatonin with radicals in deoxygenated aqueous solution

    International Nuclear Information System (INIS)

    Stasica, P.; Ulanski, P.; Rosiak, J.M.

    1998-01-01

    Reactions of melatonin (N-acetyl-5-methoxytryptamine) with radiolytically generated radicals were studied. Reaction of melatonin with OH radicals is diffusion-controlled (k=1.2 x 10 10 dm 3 mol -1 x s -1 ), the main (but not the only one) intermediate being the indolyl-type radical, while the rate constant for the reaction with hydrated electrons is k=4.3 x 10 8 dm 3 x mol -1 x s -1 . Melatonin is capable of scavenging tert-butanol radicals, while its reactivity towards polymer radicals of poly(acrylic acid) and poly(vinyl pyrrolidone) is very low. (author)

  19. [Non-enzymatic glycosylation of dietary protein in vitro].

    Science.gov (United States)

    Bednykh, B S; Evdokimov, I A; Sokolov, A I

    2015-01-01

    Non-enzymatic glycosylation of proteins, based on discovered by Mayarn reaction of carbohydrate aldehyde group with a free amino group of a protein molecule, is well known to experts in biochemistry of food industry. Generated brown solid in some cases give the product marketable qualities--crackling bread--in others conversely, worsen the product. The biological effects of far-advanced products of non-enzymatic protein glycosylation reaction have not been studied enough, although it was reported previously that they are not split by digestive enzymes and couldn't be absorbed by animals. The objective of this work was to compare the depth of glycosylation of different food proteins of animal and vegetable origin. The objects of the study were proteins of animal (casein, lactoglobulin, albumin) and vegetable (soy isolate, proteins of rice flour, buckwheat, oatmeal) origin, glucose and fructose were selected as glycosylation agents, exposure 15 days at 37 degrees C. Lactoglobulin was glycosylated to a lesser extent among the proteins of animal origin while protein of oatmeal was glycosylated in the least degree among vegetable proteins. Conversely, such proteins as casein and soya isolate protein bound rather large amounts of carbohydrates. Fructose binding with protein was generally higher than the binding of glucose. The only exception was a protein of oatmeal. When of glucose and fructose simultaneously presented in the incubation medium, glucose binding usually increased while binding of fructose, in contrast, reduced. According to the total amount of carbohydrate (mcg), which is able to attach a protein (mg) the studied food proteins located in the following order: albumin (38) > soy protein isolate (23) > casein (15,) > whey protein rice flour protein (6) > protein from buckwheat flour (3) > globulin (2) > protein of oatmeal (0.3). The results obtained are to be used to select the optimal combination of proteins and carbohydrates, in which the glycosylation

  20. Tandem and sequential multi-enzymatic syntheses

    NARCIS (Netherlands)

    Kim, B.G.; Ahn, J.H.; Sello, G.; Di Gennaro, P.; van Herk, T.; Hartog, A.F.; Wever, R.; Oroz-Guinea, I.; Sánchez-Moreno, I.; García-Junceda, E.; Wu, B.; Szymanski, W.; Feringa, B.L.; Janssen, D.B.; Villo, L.; Kreen, M.; Kudryashova, M.; Metsala, A.; Tamp, S.; Lille, ü.; Pehk, T.; Parve, O.; McClean, K.; Eddowes, P.; Whittall, J.; Sutton, P.W.

    2012-01-01

    This chapter contains sections titled: Production of Isorhamnetin 3-O-Glucoside in Escherichia coli Using Engineered Glycosyltransferase Multienzymatic Preparation of (−)-3-(Oxiran-2-yl)Benzoic Acid Enzymatic Synthesis of Carbohydrates from Dihydroxyacetone and Aldehydes by a One Pot Enzyme Cascade

  1. Enzymatic assay for methotrexate in erythrocytes

    DEFF Research Database (Denmark)

    Schrøder, H; Heinsvig, E M

    1985-01-01

    Methotrexate (MTX) accumulates in erythrocytes in MTX-treated patients. We present a modified enzymatic assay measuring MTX concentrations between 10 and 60 nmol/l in erythrocytes, adapted for a centrifugal analyser (Cobas Bio). About 40 patient's samples could be analysed within 1 h. The detection...

  2. Enzymatic hydrolysis of pretreated soybean straw

    International Nuclear Information System (INIS)

    Xu Zhong; Wang Qunhui; Jiang Zhaohua; Yang Xuexin; Ji Yongzhen

    2007-01-01

    In order to produce lactic acid, from agricultural residues such as soybean straw, which is a raw material for biodegradable plastic production, it is necessary to decompose the soybean straw into soluble sugars. Enzymatic hydrolysis is one of the methods in common use, while pretreatment is the effective way to increase the hydrolysis rate. The optimal conditions of pretreatment using ammonia and enzymatic hydrolysis of soybean straw were determined. Compared with the untreated straw, cellulose in straw pretreated by ammonia liquor (10%) soaking for 24 h at room temperature increased 70.27%, whereas hemicellulose and lignin in pretreated straw decreased to 41.45% and 30.16%, respectively. The results of infrared spectra (IR), scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis also showed that the structure and the surface of the straw were changed through pretreatment that is in favor of the following enzymatic hydrolysis. maximum enzymatic hydrolysis rate of 51.22% was achieved at a substrate concentration of 5% (w/v) at 50 deg. C and pH 4.8 using cellulase (50 fpu/g of substrate) for 36 h

  3. Starch: chemistry, microstructure, processing and enzymatic degradation

    Science.gov (United States)

    Starch is recognized as one of the most abundant and important commodities containing value added attributes for a vast number of industrial applications. Its chemistry, structure, property and susceptibility to various chemical, physical and enzymatic modifications offer a high technological value ...

  4. Coated tube for immunochemical and enzymatic assays

    International Nuclear Information System (INIS)

    Brown, J.L.; Lin, W.H.-T.; Woods, J.W.

    1979-01-01

    Containers such as test tubes suitable for use in solid phase immunochemical, enzymatical and particularly radioimmunoassay procedures are described. The lower part of the tube is a polymer, coated with an inert protein to which a biologically active substance eg an antibody to triiodothyronine, thyroxine or digoxin, is attached. (U.K.)

  5. Starch facilitates enzymatic wheat gluten hydrolysis

    NARCIS (Netherlands)

    Hardt, N.A.; Boom, R.M.; Goot, van der A.J.

    2015-01-01

    Wheat gluten can be hydrolyzed by either using (vital) wheat gluten or directly from wheat flour. This study investigates the influence of the presence of starch, the main component of wheat, on enzymatic wheat gluten hydrolysis. Wheat gluten present in wheat flour (WFG) and vital wheat gluten (VWG)

  6. Enzymatic conversion of lignocellulose into fermentable sugars

    DEFF Research Database (Denmark)

    Jørgensen, Henning; Kristensen, Jan Bach; Felby, Claus

    2007-01-01

    and hemicelluloses but these are not readily accessible to enzymatic hydrolysis and require a pretreatment, which causes an extensive modification of the lignocellulosic structure. A number of pretreatment technologies are under development and being tested in pilot scale. Hydrolysis of lignocellulose carbohydrates...

  7. Enzymatic production of polysaccharides from gum tragacanth

    DEFF Research Database (Denmark)

    2014-01-01

    Plant polysaccharides, relating to the field of natural probiotic components, can comprise structures similar to human milk oligosaccharides. A method for enzymatic hydrolysis of gum tragacanth from the bush-like legumes of the genus Astragalus, using a combination of pectin hydrolases...

  8. Aqueous two-phase systems for extractive enzymatic hydrolysis of biomass

    DEFF Research Database (Denmark)

    Bussamra, Bianca Consorti; Azzoni, Sindelia Freitas; Mussatto, Solange I.

    and enzymes, phase diagrams and volumetric ratios. The results of this project will make possible to design a process that enables high sugar concentration during the hydrolysis reaction, overcoming one of the biggest drawbacks regarding the production of second-generation ethanol: the enzymatic inhibition...... optimal aqueous two-phase systems for the separation of sugars and enzymes, which allow the development of an improved second-generation ethanol process.......Sugars derived from lignocellulosic materials are the main carbon sources in bio-based processes aiming to produce renewable fuels and chemicals. One of the major drawbacks during enzymatic hydrolysis of lignocellulosic materials to obtainsugars is the inhibition of enzymes by reaction products...

  9. Enzymatic browning and after-cooking darkening of Jerusalem artichoke tubers (Helianthus tuberosus L.)

    DEFF Research Database (Denmark)

    Bach, Vibe; Bennedbæk-Jensen, Sidsel; Clausen, Morten Rahr

    2013-01-01

    Jerusalem artichoke tubers (Helianthus tuberosus L.) undergo enzymatic browning when peeled or cut, and turn grey after boiling, due to after-cooking darkening reactions between iron and phenolic acids. In an attempt to reveal the components responsible for these discolouration reactions, sensory...... evaluation and instrumental colour measurements were related to contents of total phenolics, phenolic acids, organic acids and iron in three varieties of raw and boiled Jerusalem artichoke tubers harvested in the autumn and the spring. No differences were found between varieties in sensory evaluated...... enzymatic browning, but Rema and Draga had higher scores than Mari in after-cooking darkening. Jerusalem artichoke tubers had higher contents of total phenolics, phenolic acids and citric acid in the autumn and low contents in the spring, while it was the opposite for malic acid. None of the chemical...

  10. Enzymatic browning and after-cooking darkening of Jerusalem artichoke tubers (Helianthus tuberosus L.).

    Science.gov (United States)

    Bach, Vibe; Jensen, Sidsel; Clausen, Morten R; Bertram, Hanne C; Edelenbos, Merete

    2013-11-15

    Jerusalem artichoke tubers (Helianthus tuberosus L.) undergo enzymatic browning when peeled or cut, and turn grey after boiling, due to after-cooking darkening reactions between iron and phenolic acids. In an attempt to reveal the components responsible for these discolouration reactions, sensory evaluation and instrumental colour measurements were related to contents of total phenolics, phenolic acids, organic acids and iron in three varieties of raw and boiled Jerusalem artichoke tubers harvested in the autumn and the spring. No differences were found between varieties in sensory evaluated enzymatic browning, but Rema and Draga had higher scores than Mari in after-cooking darkening. Jerusalem artichoke tubers had higher contents of total phenolics, phenolic acids and citric acid in the autumn and low contents in the spring, while it was the opposite for malic acid. None of the chemical parameters investigated could explain the discolouration of the Jerusalem artichoke tubers. Copyright © 2013 Elsevier Ltd. All rights reserved.

  11. Enzymatic oxidation of rutin by horseradish peroxidase: kinetic mechanism and identification of a dimeric product by LC-Orbitrap mass spectrometry.

    Science.gov (United States)

    Savic, Sasa; Vojinovic, Katarina; Milenkovic, Sanja; Smelcerovic, Andrija; Lamshoeft, Marc; Petronijevic, Zivomir

    2013-12-15

    Flavonoid oxidation is important issue in food processing and quality. The kinetic mechanism of enzymatic oxidation of rutin by horseradish peroxidase (HRP) was studied. Rutin oxidation reaction was followed by recording of spectral changes over the time at 360 nm. The studied oxidation is mostly enzymatic and less part non-enzymatic. The reaction with HRP has a higher rate compared with the reaction without of HRP, whereby is part of non-enzymatic reaction about 10% of the total reaction. Kinetic parameters were determined from graphics of linear Michaelis-Menten equation, and it was found that investigated reactions of rutin oxidation by HRP take place in a ping-pong kinetic mechanism. High resolution HPLC-MS analysis of the mixture of oxidized products of rutin revealed the presence of rutin dimer. Because of widely distribution of rutin as well as presence of peroxidases and hydrogen peroxide in fresh foods identification of this enzymatic modification product can be beneficial for foods quality and safety. Copyright © 2013 Elsevier Ltd. All rights reserved.

  12. Improved enzymatic production of phenolated glycerides through alkyl phenolate intermediate

    DEFF Research Database (Denmark)

    Yang, Zhiyong; Feddern, Vivian; Glasius, Marianne

    2011-01-01

    This work reported a novel approach for synthesis of dihydrocaffoylated glycerides, consisting of 2 steps: enzymatic synthesis of octyl dihydrocaffeate (as a synthetic intermediate) from octanol and dihydrocaffeic acid (DHCA), and enzymatic interesterification of triglycerides with octyl dihydroc......This work reported a novel approach for synthesis of dihydrocaffoylated glycerides, consisting of 2 steps: enzymatic synthesis of octyl dihydrocaffeate (as a synthetic intermediate) from octanol and dihydrocaffeic acid (DHCA), and enzymatic interesterification of triglycerides with octyl...

  13. Process development for gelatinisation and enzymatic hydrolysis of starch at high concentrations

    OpenAIRE

    Baks, T.

    2007-01-01

    cum laude graduation (with distinction) Enzymatic hydrolysis of starch is encountered in day-to-day life for instance in the dishwasher during removal of stains with detergents or in our mouth during chewing of starch-based foods in the presence of saliva. The reaction is also important for the (food) industry, for example for the production of beer or bio-ethanol. In industry, it is usually preceded by gelatinisation to make the starch molecules available for the enzymes. Both gelatinisation...

  14. Simplification of lipase design in the enzymatic kinetic resolution of amines by saturation transfer difference NMR

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Marcio S.; Pietrobom, Daniel, E-mail: s.marcio@ufabc.edu.br [Universidade Federal do ABC (CCNH/UFABC), Santo André, SP (Brazil). Centro de Ciências Naturais e Humanas

    2016-07-01

    In this work, we demonstrate a nuclear magnetic resonance (NMR) method for racemic amide and lipase interaction as a first-pass design method in the enzymatic kinetic resolution of amines. As a novel adaptation of commonly used protein-ligand screening NMR methodologies, this approach relies upon a lipase-amide interaction wherein the time-consuming is reduced drastically and new insights are produced during the development of biocatalysis reactions. (author)

  15. [Experiences with the enzymatic determination of sugar and sugar substitutes in dietetic cake for diabetics (author's transl)].

    Science.gov (United States)

    Klingebiel, L; Grossklaus, R; Pahlke, G

    1979-11-01

    Sorbitol and fructose were determined enzymatically in home-made and commercially produced cake for diabetics. In some commercial products, a loss of fructose depending upon the baking period was found. This loss of fructose is to be attributed to the Maillard reaction. The findings were confirmed by comparative studies will a reference cake.

  16. Mechano-Enzymatic Deconstruction with a New Enzymatic Cocktail to Enhance Enzymatic Hydrolysis and Bioethanol Fermentation of Two Macroalgae Species

    Directory of Open Access Journals (Sweden)

    Sameh Amamou

    2018-01-01

    Full Text Available The aim of this study was to explore the efficiency of a mechano-enzymatic deconstruction of two macroalgae species for sugars and bioethanol production, by using a new enzymatic cocktail (Haliatase and two types of milling modes (vibro-ball: VBM and centrifugal milling: CM. By increasing the enzymatic concentration from 3.4 to 30 g/L, the total sugars released after 72 h of hydrolysis increased (from 6.7 to 13.1 g/100 g TS and from 7.95 to 10.8 g/100 g TS for the green algae U. lactuca and the red algae G. sesquipedale, respectively. Conversely, total sugars released from G. sesquipedale increased (up to 126% and 129% after VBM and CM, respectively. The best bioethanol yield (6 geth/100 g TS was reached after 72 h of fermentation of U. lactuca and no increase was obtained after centrifugal milling. The latter led to an enhancement of the ethanol yield of G. sesquipedale (from 2 to 4 g/100 g TS.

  17. Modeling of uncertainties in biochemical reactions.

    Science.gov (United States)

    Mišković, Ljubiša; Hatzimanikatis, Vassily

    2011-02-01

    Mathematical modeling is an indispensable tool for research and development in biotechnology and bioengineering. The formulation of kinetic models of biochemical networks depends on knowledge of the kinetic properties of the enzymes of the individual reactions. However, kinetic data acquired from experimental observations bring along uncertainties due to various experimental conditions and measurement methods. In this contribution, we propose a novel way to model the uncertainty in the enzyme kinetics and to predict quantitatively the responses of metabolic reactions to the changes in enzyme activities under uncertainty. The proposed methodology accounts explicitly for mechanistic properties of enzymes and physico-chemical and thermodynamic constraints, and is based on formalism from systems theory and metabolic control analysis. We achieve this by observing that kinetic responses of metabolic reactions depend: (i) on the distribution of the enzymes among their free form and all reactive states; (ii) on the equilibrium displacements of the overall reaction and that of the individual enzymatic steps; and (iii) on the net fluxes through the enzyme. Relying on this observation, we develop a novel, efficient Monte Carlo sampling procedure to generate all states within a metabolic reaction that satisfy imposed constrains. Thus, we derive the statistics of the expected responses of the metabolic reactions to changes in enzyme levels and activities, in the levels of metabolites, and in the values of the kinetic parameters. We present aspects of the proposed framework through an example of the fundamental three-step reversible enzymatic reaction mechanism. We demonstrate that the equilibrium displacements of the individual enzymatic steps have an important influence on kinetic responses of the enzyme. Furthermore, we derive the conditions that must be satisfied by a reversible three-step enzymatic reaction operating far away from the equilibrium in order to respond to

  18. Characterization of Secondary Mineral Grain Coatings and their Role as Diffusion-controlled Sinks and Sources for Metal Contaminants

    Science.gov (United States)

    Davis, J. A.; Guo, H.; Lai, B.; Kemner, K. M.; Ercius, P.; Fox, P. M.; Singer, D. M.; Minor, A.; Waychunas, G.

    2012-12-01

    Many important geochemical reactions occur at the mineral-water interface, including sorption and desorption reactions of contaminants. Fundamental knowledge of the kinetics of these processes is based primarily on experimental observations of reactions at faces of single crystals or macroscopic data from pure mineral powder suspensions. Sorption reactions at crystal faces are generally very fast, on the order of microseconds or less, with reaction times often limited only by film diffusion at the mineral-water interface. In well-stirred suspensions of aquifer sediments, however, sorptive equilibrium can take many hours or days to achieve steady-state concentrations. We have examined the potential reasons for sorption rate limitation using uranium(VI) sorption by sediments from a sandy aquifer in Savannah River, South Carolina (USA). U(VI) sorption by sand-sized grains from the aquifer is dominated by reaction with secondary mineral coatings on quartz and feldspar grains. The coatings studied were on the order of 15 microns in thickness (i.e., from quartz grain to aqueous solution) and composed primarily of clay minerals and hematite of varying particle size. Microfocused-XRF imaging of elemental concentrations (e.g., U, Fe) of polished cross-sections of the grain/coating contact showed strong spatial correlations of U and Fe within the coatings, regardless of the length of reaction time (30 minutes to 4 weeks). The spatial resolution of the μ-XRF technique is of the order of 2 microns in horizontal directions, but the uncertainty of the observed spatial gradients is high due to grain curvature away from the polished surface and fluorescence contributed from the entire 30 micron thickness of a typical grain/epoxy thin section. TEM characterization of focused-ion-beam (FIB), vertically-extracted samples of the grain-coating contact shows that complex pore networks exist within the coatings of variable dimensions and unknown connectivity. Using scanning TEM (STEM

  19. Design of an analytical aggregation of rules of a diffuse controller and its application in the model of a nuclear research reactor

    International Nuclear Information System (INIS)

    Najera H, M.C.

    2003-01-01

    As they have gone being managed complex systems that fulfill tasks inside industrial or nuclear processes, it becomes necessary the development of technical novel of control, in which can incorporate heuristic knowledge of operation without to necessarily use the theories of classic control based mainly in mathematical models. One of the control techniques that allows to carry out this is the control based on diffuse logic. For the case of a model of the nuclear research reactor Triga Mark III of the National Institute of Nuclear Research have been developed diverse algorithms of diffuse control that have as objective the regulation of the neutron power in the nucleus. The aggregation stages and desdifussification in these algorithms discretize the universe of values of the control variable, being required a high number of operations for their execution. With the purpose of reducing this number of operations and to obtain results more exact in the generation of the aggregated group in each cycle of control and in the determination of the center of gravity of this added group, it is presented the development of an analytical method for these calculations. The main objectives outlined in this entitled thesis D esign of an analytical aggregate of a diffuse controller rules and their application in the pattern of a nuclear research reactor , they are: to improve the behavior of control systems in closed knot based on diffuse logic by means of the development of an analytical method that determines an aggregated group resultant of the activation of rules in the diffuse controller and the obtaining of the exit variable using an exact solution of the technique of the center of gravity; and to compare the operation of these methods with those traditionally used ones that consider the discretization of the universe of the exit variable so much for the aggregation like for the desdiffusification. The chapters 1 and 2 present an introduction at two fundamental themes of the

  20. Enzymatic degradation of polycaprolactone–gelatin blend

    International Nuclear Information System (INIS)

    Banerjee, Aditi; Chatterjee, Kaushik; Madras, Giridhar

    2015-01-01

    Blends of polycaprolactone (PCL), a synthetic polymer and gelatin, natural polymer offer a optimal combination of strength, water wettability and cytocompatibility for use as a resorbable biomaterial. The enzymatic degradation of PCL, gelatin and PCL–gelatin blended films was studied in the presence of lipase (Novozym 435, immobilized) and lysozyme. Novozym 435 degraded the PCL films whereas lysozyme degraded the gelatin. Though Novozym 435 and lysozyme individually could degrade PCL–gelatin blended films, the combination of these enzymes showed the highest degradation of these blended films. Moreover, the enzymatic degradation was much faster when fresh enzymes were added at regular intervals. The changes in physico-chemical properties of polymer films due to degradation were studied by scanning electron microscopy, Fourier transform infrared spectroscopy and differential scanning calorimetry. These results have important implications for designing resorbable biomedical implants. (paper)

  1. A singular enzymatic megacomplex from Bacillus subtilis.

    Science.gov (United States)

    Straight, Paul D; Fischbach, Michael A; Walsh, Christopher T; Rudner, David Z; Kolter, Roberto

    2007-01-02

    Nonribosomal peptide synthetases (NRPS), polyketide synthases (PKS), and hybrid NRPS/PKS are of particular interest, because they produce numerous therapeutic agents, have great potential for engineering novel compounds, and are the largest enzymes known. The predicted masses of known enzymatic assembly lines can reach almost 5 megadaltons, dwarfing even the ribosome (approximately 2.6 megadaltons). Despite their uniqueness and importance, little is known about the organization of these enzymes within the native producer cells. Here we report that an 80-kb gene cluster, which occupies approximately 2% of the Bacillus subtilis genome, encodes the subunits of approximately 2.5 megadalton active hybrid NRPS/PKS. Many copies of the NRPS/PKS assemble into a single organelle-like membrane-associated complex of tens to hundreds of megadaltons. Such an enzymatic megacomplex is unprecedented in bacterial subcellular organization and has important implications for engineering novel NRPS/PKSs.

  2. Heavy metal pollution and soil enzymatic activity

    Energy Technology Data Exchange (ETDEWEB)

    Tyler, G

    1974-01-01

    The activity of hydrolytic soil enzymes was studied on spruce mor, polluted with Cu and Zn from a brass foundry in Sweden. Approximately straight regression lines were obtained between enzymatic activity or respiration rate and log Cu + Zn concentration, with highly significant negative regression coefficients for urease and acid phosphatase activity as well as respiration rate, whereas US -glucosidase activity was not measurably lower at high concentrations of Cu + Zn. 17 references, 5 figures.

  3. Effect of room temperature ionic liquid structure on the enzymatic acylation of flavonoids

    DEFF Research Database (Denmark)

    Lue, Bena-Marie; Guo, Zheng; Xu, Xuebing

    2010-01-01

    Enzymatic acylation reactions of flavonoids (rutin, esculin) with long chain fatty acids (palmitic, oleic acids) were carried out in 14 different ionic liquid media containing a range of cation and anion structures. Classification of RTILs according to flavonoid solubility (using COSMO...... must be struck that maximized flavonoid solubility with minimum negative impact on lipase activity. The process also benefitted from an increased reaction temperature which may have helped to reduced mass transfer limitations. Keywords: Room temperature ionic liquids (RTILs); Biosynthesis; Acylation......; Flavonoids; Lipase; Long chain fatty acids...

  4. Pretreatment of corn stover using wet oxidation to enhance enzymatic digestibility.

    Science.gov (United States)

    Varga, Eniko; Schmidt, Anette S; Réczey, Kati; Thomsen, Anne Belinda

    2003-01-01

    Corn stover is an abundant, promising raw material for fuel ethanol production. Although it has a high cellulose content, without pretreatment it resists enzymatic hydrolysis, like most lignocellulosic materials. Wet oxidation (water, oxygen, mild alkali or acid, elevated temperature and pressure) was investigated to enhance the enzymatic digestibility of corn stover. Six different combinations of reaction temperature, time, and pH were applied. The best conditions (60 g/L of corn stover, 195 degrees C, 15 min, 12 bar O2, 2 g/L of Na2CO3) increased the enzymatic conversion of corn stover four times, compared to untreated material. Under these conditions 60% of hemicellulose and 30% of lignin were solubilized, whereas 90% of cellulose remained in the solid fraction. After 24-h hydrolysis at 50 degrees C using 25 filter paper units (FPU)/g of drymatter (DM) biomass, the achieved conversion of cellulose to glucose was about 85%. Decreasing the hydrolysis temperature to 40 degrees C increased hydrolysis time from 24 to 72 h. Decreasing the enzyme loading to 5 FPU/g of DM biomass slightly decreased the enzymatic conversion from 83.4 to 71%. Thus, enzyme loading can be reduced without significantly affecting the efficiency of hydrolysis, an important economical aspect.

  5. Efficient sugar release by acetic acid ethanol-based organosolv pretreatment and enzymatic saccharification.

    Science.gov (United States)

    Zhang, Hongdan; Wu, Shubin

    2014-12-03

    Acetic acid ethanol-based organosolv pretreatment of sugar cane bagasse was performed to enhance enzymatic hydrolysis. The effect of different parameters (including temperature, reaction time, solvent concentration, and acid catalyst dose) on pretreatment prehydrolyzate and subsequent enzymatic digestibility was determined. During the pretreatment process, 11.83 g of xylose based on 100 g of raw material could be obtained. After the ethanol-based pretreatment, the enzymatic hydrolysis was enhanced and the highest glucose yield of 40.99 g based on 100 g of raw material could be obtained, representing 93.8% of glucose in sugar cane bagasse. The maximum total sugar yields occurred at 190 °C, 45 min, 60:40 ethanol/water, and 5% dosage of acetic acid, reaching 58.36 g (including 17.69 g of xylose and 40.67 g of glucose) based on 100 g of raw material, representing 85.4% of total sugars in raw material. Furthermore, characterization of the pretreated sugar cane bagasse using X-ray diffraction and scanning electron microscopy analyses were also developed. The results suggested that ethanol-based organosolv pretreatment could enhance enzymatic digestibilities because of the delignification and removal of xylan.

  6. Multi-Scale Computational Enzymology: Enhancing Our Understanding of Enzymatic Catalysis

    Science.gov (United States)

    Gherib, Rami; Dokainish, Hisham M.; Gauld, James W.

    2014-01-01

    Elucidating the origin of enzymatic catalysis stands as one the great challenges of contemporary biochemistry and biophysics. The recent emergence of computational enzymology has enhanced our atomistic-level description of biocatalysis as well the kinetic and thermodynamic properties of their mechanisms. There exists a diversity of computational methods allowing the investigation of specific enzymatic properties. Small or large density functional theory models allow the comparison of a plethora of mechanistic reactive species and divergent catalytic pathways. Molecular docking can model different substrate conformations embedded within enzyme active sites and determine those with optimal binding affinities. Molecular dynamics simulations provide insights into the dynamics and roles of active site components as well as the interactions between substrate and enzymes. Hybrid quantum mechanical/molecular mechanical (QM/MM) can model reactions in active sites while considering steric and electrostatic contributions provided by the surrounding environment. Using previous studies done within our group, on OvoA, EgtB, ThrRS, LuxS and MsrA enzymatic systems, we will review how these methods can be used either independently or cooperatively to get insights into enzymatic catalysis. PMID:24384841

  7. Multi-Scale Computational Enzymology: Enhancing Our Understanding of Enzymatic Catalysis

    Directory of Open Access Journals (Sweden)

    Rami Gherib

    2013-12-01

    Full Text Available Elucidating the origin of enzymatic catalysis stands as one the great challenges of contemporary biochemistry and biophysics. The recent emergence of computational enzymology has enhanced our atomistic-level description of biocatalysis as well the kinetic and thermodynamic properties of their mechanisms. There exists a diversity of computational methods allowing the investigation of specific enzymatic properties. Small or large density functional theory models allow the comparison of a plethora of mechanistic reactive species and divergent catalytic pathways. Molecular docking can model different substrate conformations embedded within enzyme active sites and determine those with optimal binding affinities. Molecular dynamics simulations provide insights into the dynamics and roles of active site components as well as the interactions between substrate and enzymes. Hybrid quantum mechanical/molecular mechanical (QM/MM can model reactions in active sites while considering steric and electrostatic contributions provided by the surrounding environment. Using previous studies done within our group, on OvoA, EgtB, ThrRS, LuxS and MsrA enzymatic systems, we will review how these methods can be used either independently or cooperatively to get insights into enzymatic catalysis.

  8. Enzymatic Synthesis of Biobased Polyesters and Polyamides

    Directory of Open Access Journals (Sweden)

    Yi Jiang

    2016-06-01

    Full Text Available Nowadays, “green” is a hot topic almost everywhere, from retailers to universities to industries; and achieving a green status has become a universal aim. However, polymers are commonly considered not to be “green”, being associated with massive energy consumption and severe pollution problems (for example, the “Plastic Soup” as a public stereotype. To achieve green polymers, three elements should be entailed: (1 green raw materials, catalysts and solvents; (2 eco-friendly synthesis processes; and (3 sustainable polymers with a low carbon footprint, for example, (biodegradable polymers or polymers which can be recycled or disposed with a gentle environmental impact. By utilizing biobased monomers in enzymatic polymerizations, many advantageous green aspects can be fulfilled. For example, biobased monomers and enzyme catalysts are renewable materials that are derived from biomass feedstocks; enzymatic polymerizations are clean and energy saving processes; and no toxic residuals contaminate the final products. Therefore, synthesis of renewable polymers via enzymatic polymerizations of biobased monomers provides an opportunity for achieving green polymers and a future sustainable polymer industry, which will eventually play an essential role for realizing and maintaining a biobased and sustainable society.

  9. Enzymatic transformation of nonfood biomass to starch

    Science.gov (United States)

    You, Chun; Chen, Hongge; Myung, Suwan; Sathitsuksanoh, Noppadon; Ma, Hui; Zhang, Xiao-Zhou; Li, Jianyong; Zhang, Y.-H. Percival

    2013-01-01

    The global demand for food could double in another 40 y owing to growth in the population and food consumption per capita. To meet the world’s future food and sustainability needs for biofuels and renewable materials, the production of starch-rich cereals and cellulose-rich bioenergy plants must grow substantially while minimizing agriculture’s environmental footprint and conserving biodiversity. Here we demonstrate one-pot enzymatic conversion of pretreated biomass to starch through a nonnatural synthetic enzymatic pathway composed of endoglucanase, cellobiohydrolyase, cellobiose phosphorylase, and alpha-glucan phosphorylase originating from bacterial, fungal, and plant sources. A special polypeptide cap in potato alpha-glucan phosphorylase was essential to push a partially hydrolyzed intermediate of cellulose forward to the synthesis of amylose. Up to 30% of the anhydroglucose units in cellulose were converted to starch; the remaining cellulose was hydrolyzed to glucose suitable for ethanol production by yeast in the same bioreactor. Next-generation biorefineries based on simultaneous enzymatic biotransformation and microbial fermentation could address the food, biofuels, and environment trilemma. PMID:23589840

  10. Microbial Enzymatic Degradation of Biodegradable Plastics.

    Science.gov (United States)

    Roohi; Bano, Kulsoom; Kuddus, Mohammed; Zaheer, Mohammed R; Zia, Qamar; Khan, Mohammed F; Ashraf, Ghulam Md; Gupta, Anamika; Aliev, Gjumrakch

    2017-01-01

    The renewable feedstock derived biodegradable plastics are important in various industries such as packaging, agricultural, paper coating, garbage bags and biomedical implants. The increasing water and waste pollution due to the available decomposition methods of plastic degradation have led to the emergence of biodegradable plastics and biological degradation with microbial (bacteria and fungi) extracellular enzymes. The microbes utilize biodegradable polymers as the substrate under starvation and in unavailability of microbial nutrients. Microbial enzymatic degradation is suitable from bioremediation point of view as no waste accumulation occurs. It is important to understand the microbial interaction and mechanism involved in the enzymatic degradation of biodegradable plastics under the influence of several environmental factors such as applied pH, thermo-stability, substrate molecular weight and/or complexity. To study the surface erosion of polymer film is another approach for hydrolytic degradation characteristion. The degradation of biopolymer is associated with the production of low molecular weight monomer and generation of carbon dioxide, methane and water molecule. This review reported the degradation study of various existing biodegradable plastics along with the potent degrading microbes (bacteria and fungi). Patents available on plastic biodegradation with biotechnological significance is also summarized in this paper. This paper assesses that new disposal technique should be adopted for the degradation of polymers and further research is required for the economical production of biodegradable plastics along with their enzymatic degradation. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  11. Structure of fungal oxyluciferin, the product of the bioluminescence reaction.

    Science.gov (United States)

    Purtov, K V; Osipova, Z M; Petushkov, V N; Rodionova, N S; Tsarkova, A S; Kotlobay, A A; Chepurnykh, T V; Gorokhovatsky, A Yu; Yampolsky, I V; Gitelson, J I

    2017-11-01

    The structure of fungal oxyluciferin was determined, the enzymatic bioluminescence reaction under substrate saturation conditions with discrete monitoring of formed products was conducted, and the structures of the end products of the reaction were established. On the basis of these studies, the scheme of oxyluciferin degradation to the end products was developed. The structure of fungal oxyluciferin was confirmed by counter synthesis.

  12. Enzymatically and chemically oxidized lignin nanoparticles for biomaterial applications.

    Science.gov (United States)

    Mattinen, Maija-Liisa; Valle-Delgado, Juan José; Leskinen, Timo; Anttila, Tuomas; Riviere, Guillaume; Sipponen, Mika; Paananen, Arja; Lintinen, Kalle; Kostiainen, Mauri; Österberg, Monika

    2018-04-01

    Cross-linked and decolorized lignin nanoparticles (LNPs) were prepared enzymatically and chemically from softwood Kraft lignin. Colloidal lignin particles (CLPs, ca. 200 nm) in a non-malodorous aqueous dispersion could be dried and redispersed in tetrahydrofuran (THF) or in water retaining their stability i.e. spherical shape and size. Two fungal laccases, Trametes hirsuta (ThL) and Melanocarpus albomyces (MaL) were used in the cross-linking reactions. Reactivity of ThL and MaL on Lignoboost™ lignin and LNPs was confirmed by high performance size exclusion chromatography (HPSEC) and oxygen consumption measurements with simultaneous detection of red-brown color due to the formation of quinones. Zeta potential measurements verified oxidation of LNPs via formation of surface-oriented carboxylic acid groups. Dynamic light scattering (DLS) revealed minor changes in the particle size distributions of LNPs after laccase catalyzed radicalization, indicating preferably covalent intraparticular cross-linking over polymerization. Changes in the surface morphology of laccase treated LNPs were imaged by atomic force (AFM) and transmission emission (TEM) microscopy. Furthermore, decolorization of LNPs without degradation was obtained using ultrasonication with H 2 O 2 in alkaline reaction conditions. The research results have high impact for the utilization of Kraft lignin as nanosized colloidal particles in advanced bionanomaterial applications in medicine, foods and cosmetics including different sectors from chemical industry. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

  13. Enzymatic carotenoid cleavage in star fruit (Averrhoa carambola).

    Science.gov (United States)

    Fleischmann, Peter; Watanabe, Naoharu; Winterhalter, Peter

    2003-05-01

    This paper presents the first description of an enzyme fraction exhibiting carotenoid cleavage activity isolated from fruit skin of Averrhoa carambola. Partial purification of the enzyme could be achieved by acetone precipitation, ultrafiltration (300 kDa, 50 kDa), isoelectric focusing (pH 3-10) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (7.5%). In this way, an enzymatically active protein fraction was obtained, consisting of four proteins in the molecular weight range of between 12 and 90 kDa. Using beta-carotene as substrate, the enzyme activity was detected spectrophotometrically at 505 nm. The main reaction product, detected by GC analysis, was beta-ionone. This proves that the isolated enzymes are closely related to aroma metabolism and release of star fruit. The time constant of the reaction was 16.6 min, the Michaelis Constant K(m)=3.6 micromol 1(-1) and the maximum velocity V(max)=10.5 x 10(-3) micromol l(-1) s(-1) mg((Protein))(-1). The optimum temperature was 45 degrees C.

  14. Chemical catalysis in biodiesel production (I): enzymatic catalysis processes

    International Nuclear Information System (INIS)

    Jachmarian, I.; Dobroyan, M.; Veira, J.; Vieitez, I.; Mottini, M.; Segura, N.; Grompone, M.

    2009-01-01

    There are some well known advantages related with the substitution of chemical catalysis by enzymatic catalysis processes.Some commercial immobilized lipases are useful for the catalysis of bio diesel reaction, which permits the achievement of high conversions and the recovery of high purity products, like a high quality glycerine. The main disadvantage of this alternative method is related with the last inactivation of the enzyme (by both the effect of the alcohol and the absorption of glycerol on catalyst surface), which added to the high cost of the catalyst, produces an unfavourable economical balance of the entire process. In the work the efficiency of two commercial immobilized lipases (Lipozyme TL IM y Novozyme 435 NNovozymes-Dinamarca) in the catalysis of the continuous transesterification of sunflower oil with different alcohols was studied. The intersolubility of the different mixturesinvolving reactans (S oil/alkyl esters/alcohol) and products (P mixtures with a higher content of 1% of glycerol,while for ethanol homogeneous mixtures were obtained at 12% of glycerol (44.44 12).Using and ethanolic substrate at the proportion S=19:75:6 and Lipozyme TL IM, it was possible to achieve a 98% of convertion to the corresponding biodiesel.When Novozymes 435 catalyzed the process it was possible to increase the oil concentration in the substrateaccording to proportion S=35:30:35, and a 78% conversion was obtained. The productivity shown by the firt enzyme was 70mg biodiesel g enzime-1, hora-1 while with the second one the productivity increased to 230. Results suggested that the convenient adjustement of substrate composition with the addition of biodiesel to reactants offers an efficient method for maximizing the enzyme productivity, hence improving the profitability of the enzymatic catalyzed process. (author)

  15. Study of Enzymatic Hydrolysis of Dilute Acid Pretreated Coconut Husk

    Directory of Open Access Journals (Sweden)

    Rudy Agustriyanto

    2012-12-01

    Full Text Available Coconut husk is classified as complex lignocellulosic material that contains cellulose, hemicellulose, lignin, and some other extractive compounds. Cellulose from coconut husk can be used as fermentation substrate after enzymatic hydrolysis. In contrary, lignin content from the coconut husk will act as an inhibitor in this hydrolysis process. Therefore, a pretreatment process is needed to enhance the hydrolysis of cellulose. The objective of this research is to investigate the production of the glucose through dilute acid pretreatment and to obtain its optimum operating conditions. In this study, the pretreatment was done using dilute sulfuric acid in an autoclave reactor. The pretreatment condition were varied at 80°C, 100°C, 120°C and 0.9%, 1.2%, 1.5% for temperature and acid concentration respectively. The acid pretreated coconut husk was then hydrolyzed using commercial cellulase (celluclast and β-glucosidase (Novozyme 188. The hydrolysis time was 72 hours and the operating conditions were varied at several temperature and pH. From the experimental results it can be concluded that the delignification temperature variation has greater influence than the acid concentration. The optimum operating condition was obtained at pH 4 and 50°C which was pretreated at 100°C using 1.5% acid concentration. Copyright © 2012 by BCREC UNDIP. All rights reserved. (Selected Paper from International Conference on Chemical and Material Engineering (ICCME 2012Received: 28th September 2012, Revised: 2nd October 2012, Accepted: 4th October 2012[How to Cite: R. Agustriyanto, A. Fatmawati, Y. Liasari. (2012. Study of Enzymatic Hydrolysis of Dilute Acid Pretreated Coconut Husk. Bulletin of Chemical Reaction Engineering & Catalysis, 7(2: 137-141. doi:10.9767/bcrec.7.2.4046.137-141] [How to Link / DOI: http://dx.doi.org/10.9767/bcrec.7.2.4046.137-141 ] | View in 

  16. Enzymatic oxidative biodegradation of nanoparticles: Mechanisms, significance and applications

    Energy Technology Data Exchange (ETDEWEB)

    Vlasova, Irina I. [Department of Environmental and Occupational Health, Center for Free Radical and Antioxidant Health, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15219 (United States); Research Institute for Physico-Chemical Medicine, Federal Medico-Biological Agency, Moscow 119453 (Russian Federation); Kapralov, Alexandr A. [Department of Environmental and Occupational Health, Center for Free Radical and Antioxidant Health, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15219 (United States); Michael, Zachary P.; Burkert, Seth C. [Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Shurin, Michael R. [Department of Pathology, University of Pittsburgh Medical Center, Pittsburgh, PA 15261 (United States); Department of Immunology, University of Pittsburgh Medical Center, Pittsburgh, PA 15261 (United States); Star, Alexander [Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Shvedova, Anna A., E-mail: ats@cdc.gov [Pathology and Physiology Research Branch, Health Effects Laboratory Division (HELD), National Institute for Occupational Safety and Health (NIOSH) and Department of Physiology and Pharmacology, West Virginia University, Morgantown, WV 26505 (United States); Kagan, Valerian E., E-mail: kagan@pitt.edu [Department of Environmental and Occupational Health, Center for Free Radical and Antioxidant Health, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15219 (United States); Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Departments of Pharmacology and Chemical Biology and Radiation Oncology, University of Pittsburgh, Pittsburgh, PA 15260 (United States)

    2016-05-15

    Biopersistence of carbon nanotubes, graphene oxide (GO) and several other types of carbonaceous nanomaterials is an essential determinant of their health effects. Successful biodegradation is one of the major factors defining the life span and biological responses to nanoparticles. Here, we review the role and contribution of different oxidative enzymes of inflammatory cells – myeloperoxidase, eosinophil peroxidase, lactoperoxidase, hemoglobin, and xanthine oxidase – to the reactions of nanoparticle biodegradation. We further focus on interactions of nanomaterials with hemoproteins dependent on the specific features of their physico-chemical and structural characteristics. Mechanistically, we highlight the significance of immobilized peroxidase reactive intermediates vs diffusible small molecule oxidants (hypochlorous and hypobromous acids) for the overall oxidative biodegradation process in neutrophils and eosinophils. We also accentuate the importance of peroxynitrite-driven pathways realized in macrophages via the engagement of NADPH oxidase- and NO synthase-triggered oxidative mechanisms. We consider possible involvement of oxidative machinery of other professional phagocytes such as microglial cells, myeloid-derived suppressor cells, in the context of biodegradation relevant to targeted drug delivery. We evaluate the importance of genetic factors and their manipulations for the enzymatic biodegradation in vivo. Finally, we emphasize a novel type of biodegradation realized via the activation of the “dormant” peroxidase activity of hemoproteins by the nano-surface. This is exemplified by the binding of GO to cyt c causing the unfolding and ‘unmasking’ of the peroxidase activity of the latter. We conclude with the strategies leading to safe by design carbonaceous nanoparticles with optimized characteristics for mechanism-based targeted delivery and regulatable life-span of drugs in circulation. - Highlights: • Nanoparticles can be degraded by

  17. Experimental evidence of a diffusion process associated with the mass asymmetry degree of freedom in heavy ion reactions

    International Nuclear Information System (INIS)

    Moretto, L.G.; Babinet, R.P.; Galin, J.; Thompson, S.G.

    1975-01-01

    Dramatic changes of fragment angular distributions over a large range of atomic numbers in the reactions induced by 14 N, 20 Ne, and 40 Ar on natural Ag targets are interpreted as evidence of a diffusion-controlled evolution of an intermediate complex along the mass asymmetry degree of freedom. (Auth.)

  18. Enzymatic production of biodiesel from microalgal oil using ethyl acetate as an acyl acceptor.

    Science.gov (United States)

    Alavijeh, Razieh Shafiee; Tabandeh, Fatemeh; Tavakoli, Omid; Karkhane, Aliasghar; Shariati, Parvin

    2015-01-01

    Microalgae have become an important source of biomass for biodiesel production. In enzymatic transesterification reaction, the enzyme activity is decreased in presence of alcohols. The use of different acyl acceptors such as methyl/ethyl acetate is suggested as an alternative and effective way to overcome this problem. In this study, ethyl acetate was used for the first time in the enzymatic production of biodiesel by using microalga, Chlorella vulgaris, as a triglyceride source. Enzymatic conversion of such fatty acids to biodiesel was catalyzed by Novozym 435 as an efficient immobilized lipase which is extensively used in biodiesel production. The best conversion yield of 66.71% was obtained at the ethyl acetate to oil molar ratio of 13:1 and Novozym 435 concentration of 40%, based on the amount of oil, and a time period of 72 h at 40℃. The results showed that ethyl acetate have no adverse effect on lipase activity and the biodiesel amount was not decreased even after seven transesterification cycles, so ethyl acetate has a great potential to be substituted for short-chain alcohols in transesterification reaction.

  19. The construction, fouling and enzymatic cleaning of a textile dye surface.

    Science.gov (United States)

    Onaizi, Sagheer A; He, Lizhong; Middelberg, Anton P J

    2010-11-01

    The enzymatic cleaning of a rubisco protein stain bound onto Surface Plasmon Resonance (SPR) biosensor chips having a dye-bound upper layer is investigated. This novel method allowed, for the first time, a detailed kinetic study of rubisco cleanability (defined as fraction of adsorbed protein removed from a surface) from dyed surfaces (mimicking fabrics) at different enzyme concentrations. Analysis of kinetic data using an established mathematical model able to decouple enzyme transfer and reaction processes [Onaizi, He, Middelberg, Chem. Eng. Sci. 64 (2008) 3868] revealed a striking effect of dyeing on enzymatic cleaning performance. Specifically, the absolute rate constants for enzyme transfer to and from a dye-bound rubisco stain were significantly higher than reported previously for un-dyed surfaces. These increased transfer rates resulted in higher surface cleanability. Higher enzyme mobility (i.e., higher enzyme adsorption and desorption rates) at the liquid-dye interface was observed, consistent with previous suggestions that enzyme surface mobility is likely correlated with overall enzyme cleaning performance. Our results show that reaction engineering models of enzymatic action at surfaces may provide insight able to guide the design of better stain-resistant surfaces, and may also guide efforts to improve cleaning formulations. Copyright 2010 Elsevier Inc. All rights reserved.

  20. Modeling enzymatic hydrolysis of lignocellulosic substrates using confocal fluorescence microscopy I: filter paper cellulose.

    Science.gov (United States)

    Luterbacher, Jeremy S; Moran-Mirabal, Jose M; Burkholder, Eric W; Walker, Larry P

    2015-01-01

    Enzymatic hydrolysis is one of the critical steps in depolymerizing lignocellulosic biomass into fermentable sugars for further upgrading into fuels and/or chemicals. However, many studies still rely on empirical trends to optimize enzymatic reactions. An improved understanding of enzymatic hydrolysis could allow research efforts to follow a rational design guided by an appropriate theoretical framework. In this study, we present a method to image cellulosic substrates with complex three-dimensional structure, such as filter paper, undergoing hydrolysis under conditions relevant to industrial saccharification processes (i.e., temperature of 50°C, using commercial cellulolytic cocktails). Fluorescence intensities resulting from confocal images were used to estimate parameters for a diffusion and reaction model. Furthermore, the observation of a relatively constant bound enzyme fluorescence signal throughout hydrolysis supported our modeling assumption regarding the structure of biomass during hydrolysis. The observed behavior suggests that pore evolution can be modeled as widening of infinitely long slits. The resulting model accurately predicts the concentrations of soluble carbohydrates obtained from independent saccharification experiments conducted in bulk, demonstrating its relevance to biomass conversion work. © 2014 Wiley Periodicals, Inc.

  1. [Optimization of enzymatic extraction of polysaccharide from Dendrobium officinale by box-Behnken design and response surface methodology].

    Science.gov (United States)

    Hu, Jian-mei; Li, Jing-ling; Feng, Peng; Zhang, Xiang-dong; Zhong, Ming

    2014-01-01

    To optimize the processing of enzymatic extraction of polysaccharide from Dendrobium officinale. With phenol-sulfuric acid method and the DNS determination polysaccharide, Box-Behnken response surface methodology was used to optimize different enzyme dosage, reaction temperature and reaction time by using Design-Expert 8.05 software for data analysis and processing. According to Box-Behnken response, the best extraction conditions for the polysaccharide from Dendrobium officinale were as follows: the amount of enzyme complex was 3.5 mg/mL, hydrolysis temperature was 53 degrees C, and reaction time was 70 min. In accordance with the above process, the polysaccharide yield was 16.11%. Box-Behnken response surface methodology is used to optimize the enzymatic extraction process for the polysaccharide in this study, which is effective, stable and feasible.

  2. Distribution, industrial applications, and enzymatic synthesis of D-amino acids.

    Science.gov (United States)

    Gao, Xiuzhen; Ma, Qinyuan; Zhu, Hailiang

    2015-04-01

    D-Amino acids exist widely in microbes, plants, animals, and food and can be applied in pharmaceutical, food, and cosmetics. Because of their widespread applications in industry, D-amino acids have recently received more and more attention. Enzymes including D-hydantoinase, N-acyl-D-amino acid amidohydrolase, D-amino acid amidase, D-aminopeptidase, D-peptidase, L-amino acid oxidase, D-amino acid aminotransferase, and D-amino acid dehydrogenase can be used for D-amino acids synthesis by kinetic resolution or asymmetric amination. In this review, the distribution, industrial applications, and enzymatic synthesis methods are summarized. And, among all the current enzymatic methods, D-amino acid dehydrogenase method not only produces D-amino acid by a one-step reaction but also takes environment and atom economics into consideration; therefore, it is deserved to be paid more attention.

  3. Properties important for solid–liquid separations change during the enzymatic hydrolysis of pretreated wheat straw

    DEFF Research Database (Denmark)

    Weiss, Noah Daniel; Felby, Claus; Thygesen, Lisbeth Garbrecht

    2018-01-01

    Objectives The biochemical conversion of lignocellulosic biomass into renewable fuels and chemicals provides new challenges for industrial scale processes. One such process, which has received little attention, but is of great importance for efficient product recovery, is solid–liquid separations......, which may occur both after pretreatment and after the enzymatic hydrolysis steps. Due to the changing nature of the solid biomass during processing, the solid–liquid separation properties of the biomass can also change. The objective of this study was to show the effect of enzymatic hydrolysis...... of cellulose upon the water retention properties of pretreated biomass over the course of the hydrolysis reaction. Results Water retention value measurements, coupled with 1H NMR T2 relaxometry data, showed an increase in water retention and constraint of water by the biomass with increasing levels...

  4. Binding of Nickel to Testicular Glutamate–Ammonia Ligase Inhibits Its Enzymatic Activity

    Science.gov (United States)

    SUN, YINGBIAO; OU, YOUNG; CHENG, MIN; RUAN, YIBING; VAN DER HOORN, FRANS A.

    2016-01-01

    SUMMARY Exposure to nickel has been shown to cause damage to the testis in several animal models. It is not known if the testis expresses protein(s) that can bind nickel. To test this, we used a nickel-binding assay to isolate testicular nickel-binding proteins. We identified glutamate–ammonia ligase (GLUL) as a prominent nickel-binding protein by mass spectrometry. Protein analysis and reverse transcriptase polymerase chain reaction showed that GLUL is expressed in the testis, predominantly in interstitial cells. We determined that GLUL has a higher affinity for nickel than for its regular co-factor manganese. We produced an enzymatically active, recombinant GLUL protein. Upon binding, nickel interferes with the manganese-catalyzed enzymatic activity of recombinant GLUL protein. We also determined that GLUL activity in testes of animals exposed to nickel sulfate is reduced. Our results identify testicular GLUL as the first testicular protein shown to be affected by nickel exposure. PMID:21254280

  5. Microwave irradiation of lignocellulosic materials, 4: Enhancement of enzymatic susceptibility of microwave-irradiated softwoods

    International Nuclear Information System (INIS)

    Azuma, J.; Higashino, J.; Isaka, M.; Koshijima, T.

    1985-01-01

    Effect of microwave irradiation on the enzymatic susceptibility of various softwoods was investigated. The pH values of the reaction liquor dropped with increasing temperature to 2.9-3.3 at 230°C, consistent with increase in acidity (0.5-0.85 meq at 230-239° C). Above approximately 180°C, hemicellulose underwent acid-mediated autohydrolysis and became water-soluble yielding a mixture of oligosaccharides and monosaccharides. The composition of water-soluble portion was similar for all wood species tested. The maximum extents of saccharification below 240°C ranged between 36-62% for softwoods, while those for hardwoods were between 88-93%. The present investigation confirmed that microwave pretreatment enhanced the enzymatic susceptibility of various softwoods. However, further attempt should be needed to give higher values equal to those for hardwoods. (author)

  6. Fabrication of high surface area graphene electrodes with high performance towards enzymatic oxygen reduction

    International Nuclear Information System (INIS)

    Di Bari, Chiara; Goñi-Urtiaga, Asier; Pita, Marcos; Shleev, Sergey; Toscano, Miguel D.; Sainz, Raquel; De Lacey, Antonio L.

    2016-01-01

    High surface area graphene electrodes were prepared by simultaneous electrodeposition and electroreduction of graphene oxide. The electrodeposition process was optimized in terms of pH and conductivity of the solution and the obtained graphene electrodes were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and electrochemical methods (cyclic voltammetry and impedance spectroscopy). Electrodeposited electrodes were further functionalized to carry out covalent immobilization of two oxygen-reducing multicopper oxidases: laccase and bilirubin oxidase. The enzymatic electrodes were tested as direct electron transfer based biocathodes and catalytic currents as high as 1 mA/cm 2 were obtained. Finally, the mechanism of the enzymatic oxygen reduction reaction was studied for both enzymes calculating the Tafel slopes and transfer coefficients.

  7. Real-Time Model Based Process Monitoring of Enzymatic Biodiesel Production

    DEFF Research Database (Denmark)

    Price, Jason Anthony; Nordblad, Mathias; Woodley, John

    2015-01-01

    In this contribution we extend our modelling work on the enzymatic production of biodiesel where we demonstrate the application of a Continuous-Discrete Extended Kalman Filter (a state estimator). The state estimator is used to correct for mismatch between the process data and the process model...... for Fed-batch production of biodiesel. For the three process runs investigated, using a single tuning parameter, qx=2 x 10-2 which represents the uncertainty in the process model, it was possible over the entire course of the reaction to reduce the overall mean and standard deviation of the error between......, there was over a ten-fold decrease in the overall mean error for the state estimator prediction compared with the predictions from the pure model simulations. It is also shown that the state estimator can be used as a tool for detection of outliers in the measurement data. For the enzymatic biodiesel process...

  8. Enzymatically interesterified fats based on mutton tallow and walnut oil suitable for cosmetic emulsions.

    Science.gov (United States)

    Kowalska, M; Mendrycka, M; Zbikowska, A; Stawarz, S

    2015-02-01

    Formation of emulsion systems based on interesterified fats was the objective of the study. Enzymatic interesterification was carried out between enzymatic mutton tallow and walnut oil in the proportions 2 : 3 (w/w) to produce fats not available in nature. At the beginning of the interesterification process, the balance between the interesterification and fat hydrolysis was intentionally disturbed by adding more water to the catalyst (Lipozyme IR MR) of the reaction to produce more of the polar fraction monoacylglycerols [MAGs] and diacylglycerols [DAGs]. To obtain a greater quantity of MAGs and DAGs in the reaction environment via hydrolysis, water was added (11, 13, 14, 16 w-%) to the enzymatic preparation. The obtained fats were used to form emulsions. The emulsions were evaluated with respect to sensory and skin moisturizing properties by 83 respondents. Determination of emulsion stability using temperature and centrifugal tests was carried out. Morphology and the type of emulsions were determined. The respondents described the skin to which the emulsions in testing were applied as smooth, pleasant to touch and adequately moisturized. The work has demonstrated that interesterification of a mutton tallow and walnut oil blend resulted in new fats with very interesting characteristics of triacylglycerols that are not present in the environment. The results of the present work indicate the possibility of application of fats with the largest quantity of MAGs and DAGs as a fat base of emulsions in the cosmetic industries. The hypothesis assumed in this work of producing additional quantities of MAGs and DAGs (in the process of enzymatic interesterification) responsible for the stability of the system was confirmed. It should be pointed out that the emulsions based on interesterified fats exhibited a greater level of moisturization of the skin than the emulsions containing non-interesterified fat. Also, in the respondents' opinion, the emulsion containing fat, which

  9. Synthesizing aspartyl-phenylalanine methyl precursor by enzymatic method. Kosoho ni yoru asuparutemu zenkutai no gosei

    Energy Technology Data Exchange (ETDEWEB)

    Hirata, M. (Waseda University, Tokyo (Japan)); Hirata, A. (Waseda University, Tokyo (Japan). School of Science and Engineering)

    1991-10-01

    Demand for aspartyl-phenylalanine methyl, an amino acid based artificial sweetener, is increasing for use by people on diet. The material is manufactured by making a precursor through dehydrating and condensing N-protective{sub L}-asparagine acid and {sub L}-phenylalanine methyl ester, and then removing the protective group. While the manufacturing methods include chemical process and enzymatic process, this paper introduces various researches done mainly by the latter process. The enzymatic process is simpler and safer than the chemical process, allowing experiments to be carried out easily. However, since the reaction equilibrium is biased more on the decomposition side than the synthesis side, it should be shifted to the synthesis side. Such operations may be carried out as separating the products simultaneously with the reaction, adding organic solvents, and operating the reaction in an organic solvent. The last operation, for example, reduces the concentration of liquid produced by the reaction by use of either water soluble or slightly soluble organic solvent, and improves the yield. It also has an advantage that relatively stable fixing enzymes can be adjusted by use of hydrophilic carriers. 68 refs., 8 figs.

  10. A Simple Method To Demonstrate the Enzymatic Production of Hydrogen from Sugar

    Science.gov (United States)

    Hershlag, Natalie; Hurley, Ian; Woodward, Jonathan

    1998-10-01

    There is current interest in and concern for the development of environmentally friendly bioprocesses whereby biomass and the biodegradable content of municipal wastes can be converted to useful forms of energy. For example, cellulose, a glucose polymer that is the principal component of biomass and paper waste, can be enzymatically degraded to glucose, which can subsequently be converted by fermentation or further enzymatic reaction to fuels such as ethanol or hydrogen. These products represent alternative energy sources to fossil fuels such as oil. Demonstration of the relevant reactions in high-school and undergraduate college laboratories would have value not only in illustrating environmentally friendly biotechnology for the utilization of renewable energy sources, such as cellulosic wastes, but could also be used to teach the principles of enzyme-catalyzed reactions. In the experimental protocol described here, it has been demonstrated that the common sugar glucose can be used to produce hydrogen using two enzymes, glucose dehydrogenase and hydrogenase. No sophisticated or expensive hydrogen detection equipment is required-only a redox dye, benzyl viologen, which turns purple when it is reduced. The color can be detected by a simple colorimeter. Furthermore, it is shown that the renewable resource cellulose, in its soluble derivative from carboxymethylcellulose, as well as aspen-wood waste, is also a source of hydrogen if the enzyme cellulase is included in the reaction mixture.

  11. Enzymatically crosslinked silk-hyaluronic acid hydrogels.

    Science.gov (United States)

    Raia, Nicole R; Partlow, Benjamin P; McGill, Meghan; Kimmerling, Erica Palma; Ghezzi, Chiara E; Kaplan, David L

    2017-07-01

    In this study, silk fibroin and hyaluronic acid (HA) were enzymatically crosslinked to form biocompatible composite hydrogels with tunable mechanical properties similar to that of native tissues. The formation of di-tyrosine crosslinks between silk fibroin proteins via horseradish peroxidase has resulted in a highly elastic hydrogel but exhibits time-dependent stiffening related to silk self-assembly and crystallization. Utilizing the same method of crosslinking, tyramine-substituted HA forms hydrophilic and bioactive hydrogels that tend to have limited mechanics and degrade rapidly. To address the limitations of these singular component scaffolds, HA was covalently crosslinked with silk, forming a composite hydrogel that exhibited both mechanical integrity and hydrophilicity. The composite hydrogels were assessed using unconfined compression and infrared spectroscopy to reveal of the physical properties over time in relation to polymer concentration. In addition, the hydrogels were characterized by enzymatic degradation and for cytotoxicity. Results showed that increasing HA concentration, decreased gelation time, increased degradation rate, and reduced changes that were observed over time in mechanics, water retention, and crystallization. These hydrogel composites provide a biologically relevant system with controllable temporal stiffening and elasticity, thus offering enhanced tunable scaffolds for short or long term applications in tissue engineering. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Enzymatic activity of fungi isolated from crops

    Directory of Open Access Journals (Sweden)

    Wioletta A. Żukiewicz-Sobczak

    2016-12-01

    Full Text Available Aim: To detect and assess the activity of extracellular hydrolytic enzymes and to find differences in enzymograms between fungi isolated from wheat and rye samples and grown on Czapek-Dox Broth and Sabouraud Dextrose Broth enriched with cereal (wheat or rye. Isolated strains were also classified in the scale of biosafety levels (BSL. Material and methods: The study used 23 strains of fungi cultured from samples of wheat and rye (grain, grain dust obtained during threshing and soil collected in the Lublin region (eastern Poland. API ZYM test (bioMérieux was carried out according to the manufacturer’s instructions. Classification of BSL (Biosafety levels was based on the current literature. Results : High enzymatic activity was found in strains cultured in media containing 1% of wheat grain ( Bipolaris holmi, Penicillium decumbens and with an addition of 1% of rye grain ( Cladosporium herbarum, Aspergillus versicolor, Alternaria alternata . The total number of enzymes varied depending on the type of media, and in most cases it was higher in the culture where an addition of cereal grains was used. Conclusions : Isolated strains of fungi reveal differences in the profiles of the enzyme assay. It can be assumed that the substrate enriched in grains stimulate the higher activity of mold enzymes. Key words: enzymatic activity, mold fungi, zymogram, biohazards.

  13. Lactose hydrolysis in an enzymatic membrane reactor

    Energy Technology Data Exchange (ETDEWEB)

    Mertens, B; Huyghebaert, A

    1987-10-01

    The enzymatic hydrolysis of lactose in whey permeate with subsequent recuperation of Saccharomyces lactis lactase by means of ultrafiltration was investigated. In whey permeate, S. lactis lactase shows maximal activity at pH 6.5; the optimal temperature was found to be 45/sup 0/C and is limited by strong thermal inactivation beyond this temperature. High activity combined with acceptable thermal inactivation (< 10% after 5 h incubation) was established at 30/sup 0/C. S. lactis lactase also displays considerable activity at low temperature (5/sup 0/C). Enzyme stability is reduced drastically by demineralisation: addition of low concentrations of manganese ions (10/sup -3/ M) considerably enhances stability. Using a DDS Lab-Unit 35 fitted with GR61PP polysulphon membranes (cut-off: 20.000), pilot scale experiments were carried out (pH 6.5; 30/sup 0/C) in which whey permeate was hydrolyzed to a degree of hydrolysis of 82% minimum. Enzyme recuperation amounted to 96.5% per batch, all enzyme activity loss being due to thermal inactivation. Microbiological examination of the enzymatic membrane reactor showed that growth of mcicroorganisms can largely be suppressed by working at lower temperature (5/sup 0/C). Eventually, 50 ppm H/sub 2/O/sub 2/ or sterile filtration will adequately solve microbiological problems without affecting enzyme activity.

  14. Enzymatic hydrolsis of pretreated rice straw

    Energy Technology Data Exchange (ETDEWEB)

    Vlasenko, E.Y.; Shoemaker, S.P. [California Inst. of Food and Agricultural Research, Davis, CA (United States); Ding, H. [California Univ., Davis (Canada). Dept. of Food Science and Technology; Labavitch, J.M. [California Univ., Davis, CA (United States). Dept. of Pomology

    1997-02-01

    California rice straw is being evaluated as a feedstock for production of power and fuel. This paper examines the initial steps in the process: pretreatment of rice straw and enzymatic hydrolysis of the polysaccharides in the pretreated material to soluble sugars. Rice straw was subjected to three distinct pretreatment procedures: acid-catalyzed steam explosion (Swan Biomass Company), acid hydrolysis (U.S. DOE National Renewable Energy Laboratory), and ammonia fiber explosion or AFEX (Texas A and M University). Standard conditions for each pretreatment were used, but none was optimized for rice straw specifically. Six commercial cellulases, products of Genencor International (USA), Novo (Denmark), Iogen (Canada) and Fermtech (Russia) were used for hydrolysis. The Swan- and the acid-pretreatments effectively removed hemicellulose from rice straw, providing high yields of fermentable sugars. The AFEX-pretreatment was distinctly different from other pretreatments in that it did not significantly solubilize hemicellulose. All three pretreatment procedures substantially increased enzymatic digestibility of rice straw. Three commercial Trichoderma-reesei-derived enzyme preparations: Cellulase 100L (Iogen), Spezyme CP (Genencor), and Al (Fermtech), were more active on pretreated rice straw compared than others tested. Conditions for hydrolysis of rice straw using Cellulase 100L were evaluated. The supplementation of this enzyme preparation with cellobiase (Novozyme 188) significantly improved the parameters of hydrolysis for the Swan- and the acid-pretreated materials, but did not affect the hydrolysis of the AFEX-pretreated rice straw. (Author)

  15. Method and device for thermal control of biological and chemical reactions using magnetic particles or magnetic beads and variable magnetic fields

    OpenAIRE

    Zilch, C.; Gerdes, W.; Bauer, J.; Holschuh, K.

    2009-01-01

    The invention relates to a method for the thermal control of at least one temperature-dependent enzymatic reaction in the presence of magnetic particles, particularly nanoparticles, or magnetic beads, in vitro by heating the magnetic beads or magnetic particles to at least one defined target temperature using alternating magnetic fields. The thermally controllable enzymatic reaction carried out with the method according to the invention is preferably a PCR reaction or another reaction for elo...

  16. Computational study on a puzzle in the biosynthetic pathway of anthocyanin: Why is an enzymatic oxidation/ reduction process required for a simple tautomerization?

    Science.gov (United States)

    Sato, Hajime; Wang, Chao; Yamazaki, Mami; Saito, Kazuki; Uchiyama, Masanobu

    2018-01-01

    In the late stage of anthocyanin biosynthesis, dihydroflavonol reductase (DFR) and anthocyanidin synthase (ANS) mediate a formal tautomerization. However, such oxidation/reduction process requires high energy and appears to be unnecessary, as the oxidation state does not change during the transformation. Thus, a non-enzymatic pathway of tautomerization has also been proposed. To resolve the long-standing issue of whether this non-enzymatic pathway is the main contributor for the biosynthesis, we carried out density functional theory (DFT) calculations to examine this non-enzymatic pathway from dihydroflavonol to anthocyanidin. We show here that the activation barriers for the proposed non-enzymatic tautomerization are too high to enable the reaction to proceed under normal aqueous conditions in plants. The calculations also explain the experimentally observed requirement for acidic conditions during the final step of conversion of 2-flaven-3,4-diol to anthocyanidin; a thermodynamically and kinetically favorable concerted pathway can operate under these conditions.

  17. Nuclear reactions

    International Nuclear Information System (INIS)

    Lane, A.M.

    1980-01-01

    In reviewing work at Harwell over the past 25 years on nuclear reactions it is stated that a balance has to be struck in both experiment and theory between work on cross-sections of direct practical relevance to reactors and on those relevant to an overall understanding of reaction processes. The compound nucleus and direct process reactions are described. Having listed the contributions from AERE, Harwell to developments in nuclear reaction research in the period, work on the optical model, neutron capture theory, reactions at doorway states with fine structure, and sum-rules for spectroscopic factors are considered in more detail. (UK)

  18. Analytical Validation of a New Enzymatic and Automatable Method for d-Xylose Measurement in Human Urine Samples

    Directory of Open Access Journals (Sweden)

    Israel Sánchez-Moreno

    2017-01-01

    Full Text Available Hypolactasia, or intestinal lactase deficiency, affects more than half of the world population. Currently, xylose quantification in urine after gaxilose oral administration for the noninvasive diagnosis of hypolactasia is performed with the hand-operated nonautomatable phloroglucinol reaction. This work demonstrates that a new enzymatic xylose quantification method, based on the activity of xylose dehydrogenase from Caulobacter crescentus, represents an excellent alternative to the manual phloroglucinol reaction. The new method is automatable and facilitates the use of the gaxilose test for hypolactasia diagnosis in the clinical practice. The analytical validation of the new technique was performed in three different autoanalyzers, using buffer or urine samples spiked with different xylose concentrations. For the comparison between the phloroglucinol and the enzymatic assays, 224 urine samples of patients to whom the gaxilose test had been prescribed were assayed by both methods. A mean bias of −16.08 mg of xylose was observed when comparing the results obtained by both techniques. After adjusting the cut-off of the enzymatic method to 19.18 mg of xylose, the Kappa coefficient was found to be 0.9531, indicating an excellent level of agreement between both analytical procedures. This new assay represents the first automatable enzymatic technique validated for xylose quantification in urine.

  19. Enzymatic Mercury Detoxification: The Regulatory Protein MerR

    CERN Multimedia

    Ctortecka, B; Walsh, C T; Comess, K M

    2002-01-01

    Mercury ions and organomercurial reagents are extremely toxic due to their affinity for thiol groups. Many bacteria contain an elaborate detoxification system for a metabolic conversion of toxic Hg$^{2+}$ or organomercurials to less toxic elemental Hg$^0$. The main components of the enzymatic mercury detoxification (see Fig. 1) are the regulatory protein MerR (mercury responsive genetic switch), the organomercurial lyase MerB (cleavage of carbon mercury bonds), and the mercuric ion reductase MerA (reduction of mercuric ions). In these proteins Hg$^{2+}$ is usually coordinated by the thiol groups of cysteines. We utilize the nuclear quadrupole interaction (NQI) of ${\\rm^{199m}}$Hg detected by time differential perturbed angular correlation (TDPAC) to identify the Hg metal site geometries in these proteins in order to elucidate the molecular origin of the ultrasensitivity, selectivity and reaction mechanism of this detoxification system. The short lived TDPAC probe ${\\rm^{199m}}$Hg ($\\tau_{1/2} =$ 43 min) is su...

  20. Enzymatic synthesis of 13N-β-nicotinamide adenine dinucleotide

    International Nuclear Information System (INIS)

    Lambrecht, R.H.D.; Slegers, G.; Claeys, A.; Vandecasteele, C.

    1985-01-01

    Nitrogen-13-labelled β-nicotinamide adenine dinucleotide ( 13 N-NAD) is an interesting new compound for positron emission tomography. A semi-automatic production method is developed that yields a solution of 13 N-NAD of radiopharmaceutical quality, suitable for human intravenous administration. The 13 N-NAD is prepared enzymatically in one step from cyclotron-produced 13 NH 3 and nicotinic acid adenine dinucleotide (deamido-NAD). The enzyme NAD synthetase (E.C. 6.3.1.5), catalysing this reaction, is extracted and purified from Escherichia coli. The purified enzyme is immobilized by glutaraldehyde coupling to γ-aminopropylsilane-coated porous glass beads. The enzyme-loaded glass beads are packed in a column. The kinetic properties of the column are optimized. For synthetizing 13 N-NAD, the mixture of co-factors and substrates, containing 13 NH 3 , is pumped over the enzyme column. The unreacted 13 NH 3 is separated from 13 N-NAD by on-line passage over a cation exchanger. After passing over a millipore filter, a sterile solution of radiochemically pure 13 N-NAD is obtained, containing 70 mCi in 10 mL. The total synthesis time is 10 minutes. The specific activity is about 120 mCi/μmol at EOB. Quality control includes sterility and pyrogen tests, HPLC and HPTLC analysis. (author)

  1. Enzymatic synthesis of rubber polymer in Hevea brasiliensis

    Energy Technology Data Exchange (ETDEWEB)

    Tang, F.; Hu, S.; Benedict, C.R. (Texas A and M Univ., College Station (United States))

    1991-05-01

    Light and Dennis purified serum soluble rubber transferase from Hevea latex to homogeneity. Prenyl transferase co-purified with rubber transferase. In the absence of washed rubber particles (WRP) the prenyl transferase catalyzed the formation of trans FPP from DMAPP and IPP. In the presence of WRP the transferase catalyzed cis additions of IPP to pre-existing rubber chains. Control mixtures of WRP, Mg{sup 2+} and FPP were not included to test for the contributions of the bound rubber transferase on WRP to the incorporation of IPP into polyisoprene. Bound rubber transferase catalyzes the repetitive addition of IPP to allylic-PP starter molecules to form polyisoprene. The order of utilization of allylic-PP starters was GGPP > FPP > GPP > DMAPP. The authors have shown that the polyisoprene enzymatically synthesized on WRP is a bimodal polymer consisting of different mol wt rubber chains similar to the polymeric characteristics of natural rubber. The bound rubber transferase was solubilized with Chaps and purified on DEAE-cellulose. The polymerization reaction catalyzed by the purified preparation showed a 98% requirement for pre-existing rubber chains. Results suggest that the prenyl transferase from Hevea serum may be part of the polymer starter system furnishing allylic-PP for the bound rubber transferase.

  2. Site-Specific Bioconjugation of an Organometallic Electron Mediator to an Enzyme with Retained Photocatalytic Cofactor Regenerating Capacity and Enzymatic Activity

    Directory of Open Access Journals (Sweden)

    Sung In Lim

    2015-04-01

    Full Text Available Photosynthesis consists of a series of reactions catalyzed by redox enzymes to synthesize carbohydrates using solar energy. In order to take the advantage of solar energy, many researchers have investigated artificial photosynthesis systems mimicking the natural photosynthetic enzymatic redox reactions. These redox reactions usually require cofactors, which due to their high cost become a key issue when constructing an artificial photosynthesis system. Combining a photosensitizer and an Rh-based electron mediator (RhM has been shown to photocatalytically regenerate cofactors. However, maintaining the high concentration of cofactors available for efficient enzymatic reactions requires a high concentration of the expensive RhM; making this process cost prohibitive. We hypothesized that conjugation of an electron mediator to a redox enzyme will reduce the amount of electron mediators necessary for efficient enzymatic reactions. This is due to photocatalytically regenerated NAD(PH being readily available to a redox enzyme, when the local NAD(PH concentration near the enzyme becomes higher. However, conventional random conjugation of RhM to a redox enzyme will likely lead to a substantial loss of cofactor regenerating capacity and enzymatic activity. In order to avoid this issue, we investigated whether bioconjugation of RhM to a permissive site of a redox enzyme retains cofactor regenerating capacity and enzymatic activity. As a model system, a RhM was conjugated to a redox enzyme, formate dehydrogenase obtained from Thiobacillus sp. KNK65MA (TsFDH. A RhM-containing azide group was site-specifically conjugated to p-azidophenylalanine introduced to a permissive site of TsFDH via a bioorthogonal strain-promoted azide-alkyne cycloaddition and an appropriate linker. The TsFDH-RhM conjugate exhibited retained cofactor regenerating capacity and enzymatic activity.

  3. Use of Enzymatic Bio-Fenton as a New Approach in Decolorization of Malachite Green

    Directory of Open Access Journals (Sweden)

    Afzal Karimi

    2012-01-01

    Full Text Available An enzymatic reaction using glucose oxidase was applied for in situ production of hydrogen peroxide for use in simultaneously Fenton's reaction in decolorization of malachite green. It was found that decolorization rate increased by increasing of glucose concentration from 0.2 g/L to 1.5 g/L. Decolorization rate showed different behaviors versus temperature changes. Initial rate of decolorization process was increased by increasing of temperature; after 30 minutes, especially at temperatures above 30°C, the decolorization rate was gradually reduced. The pH value in the reaction media was decreased from natural to about pH=3 which had synergic effect on the Fenton process by stabilizing of Fe2+ ions.

  4. Use of Enzymatic Bio-Fenton as a New Approach in Decolorization of Malachite Green

    Science.gov (United States)

    Karimi, Afzal; Aghbolaghy, Mostafa; Khataee, Alireza; Shoa Bargh, Shabnam

    2012-01-01

    An enzymatic reaction using glucose oxidase was applied for in situ production of hydrogen peroxide for use in simultaneously Fenton's reaction in decolorization of malachite green. It was found that decolorization rate increased by increasing of glucose concentration from 0.2 g/L to 1.5 g/L. Decolorization rate showed different behaviors versus temperature changes. Initial rate of decolorization process was increased by increasing of temperature; after 30 minutes, especially at temperatures above 30°C, the decolorization rate was gradually reduced. The pH value in the reaction media was decreased from natural to about pH = 3 which had synergic effect on the Fenton process by stabilizing of Fe2+ ions. PMID:22649310

  5. Enzymatic interesterification of palm stearin and coconut oil by a dual lipase system

    DEFF Research Database (Denmark)

    Ibrahim, Nuzul Amri Bin; Guo, Zheng; Xu, Xuebing

    2008-01-01

    greater than 100% over the theoretical value when the reaction proceeds for 2 h. The co-immobilization action of the carrier of the immobilized lipases towards the free lipase was proposed as being one of the reasons leading to the synergistic effect and this has been experimentally verified by a reaction......Enzymatic interesterification of palm stearin with coconut oil was conducted by applying a dual lipase system in comparison with individual lipase-catalyzed reactions. The results indicated that a synergistic effect occurred for many lipase combinations, but largely depending on the lipase species...... mixed and their ratios. The combination of Lipozyme TL IM and RM IM was found to generate a positive synergistic action at all test mixing ratios. Only equivalent amount mixtures of Lipozyme TL IM with Novozym 435 or Lipozyme RM IM with Novozym 435 produced a significant synergistic effect as well...

  6. Kinetics of enzymatic trans-esterification of glycerides for biodiesel production.

    Science.gov (United States)

    Calabrò, Vincenza; Ricca, Emanuele; De Paola, Maria Gabriela; Curcio, Stefano; Iorio, Gabriele

    2010-08-01

    In this paper, the reaction of enzymatic trans-esterification of glycerides with ethanol in a reaction medium containing hexane at a temperature of 37 degrees C has been studied. The enzyme was Lipase from Mucor miehei, immobilized on ionic exchange resin, aimed at achieving high catalytic specific surface and recovering, regenerating and reusing the biocatalyst. A kinetic analysis has been carried out to identify the reaction path; the rate equation and kinetic parameters have been also calculated. The kinetic model has been validated by comparison between predicted and experimental results. Mass transport resistances estimation was undertaken in order to verify that the kinetics found was intrinsic. Model potentialities in terms of reactors design and optimization are also shown.

  7. Enzymatic lignocellulose hydrolysis: Improved cellulase productivity by insoluble solids recycling

    Science.gov (United States)

    2013-01-01

    Background It is necessary to develop efficient methods to produce renewable fuels from lignocellulosic biomass. One of the main challenges to the industrialization of lignocellulose conversion processes is the large amount of cellulase enzymes used for the hydrolysis of cellulose. One method for decreasing the amount of enzyme used is to recycle the enzymes. In this study, the recycle of enzymes associated with the insoluble solid fraction after the enzymatic hydrolysis of cellulose was investigated for pretreated corn stover under a variety of recycling conditions. Results It was found that a significant amount of cellulase activity could be recovered by recycling the insoluble biomass fraction, and the enzyme dosage could be decreased by 30% to achieve the same glucose yields under the most favorable conditions. Enzyme productivity (g glucose produced/g enzyme applied) increased between 30 and 50% by the recycling, depending on the reaction conditions. While increasing the amount of solids recycled increased process performance, the methods applicability was limited by its positive correlation with increasing total solids concentrations, reaction volumes, and lignin content of the insoluble residue. However, increasing amounts of lignin rich residue during the recycle did not negatively impact glucose yields. Conclusions To take advantage of this effect, the amount of solids recycled should be maximized, based on a given processes ability to deal with higher solids concentrations and volumes. Recycling of enzymes by recycling the insoluble solids fraction was thus shown to be an effective method to decrease enzyme usage, and research should be continued for its industrial application. PMID:23336604

  8. Enzymatic lignocellulose hydrolysis: Improved cellulase productivity by insoluble solids recycling

    Directory of Open Access Journals (Sweden)

    Weiss Noah

    2013-01-01

    Full Text Available Abstract Background It is necessary to develop efficient methods to produce renewable fuels from lignocellulosic biomass. One of the main challenges to the industrialization of lignocellulose conversion processes is the large amount of cellulase enzymes used for the hydrolysis of cellulose. One method for decreasing the amount of enzyme used is to recycle the enzymes. In this study, the recycle of enzymes associated with the insoluble solid fraction after the enzymatic hydrolysis of cellulose was investigated for pretreated corn stover under a variety of recycling conditions. Results It was found that a significant amount of cellulase activity could be recovered by recycling the insoluble biomass fraction, and the enzyme dosage could be decreased by 30% to achieve the same glucose yields under the most favorable conditions. Enzyme productivity (g glucose produced/g enzyme applied increased between 30 and 50% by the recycling, depending on the reaction conditions. While increasing the amount of solids recycled increased process performance, the methods applicability was limited by its positive correlation with increasing total solids concentrations, reaction volumes, and lignin content of the insoluble residue. However, increasing amounts of lignin rich residue during the recycle did not negatively impact glucose yields. Conclusions To take advantage of this effect, the amount of solids recycled should be maximized, based on a given processes ability to deal with higher solids concentrations and volumes. Recycling of enzymes by recycling the insoluble solids fraction was thus shown to be an effective method to decrease enzyme usage, and research should be continued for its industrial application.

  9. PRETREATMENT OF LIGNOCELLULOSIC BIOMASS FOR ENZYMATIC HYDROLYSIS

    Directory of Open Access Journals (Sweden)

    Doan Thai Hoa

    2017-11-01

    Full Text Available The cost of raw materials continues to be a limiting factor in the production of bio-ethanol from traditional raw materials, such as sugar and starch. At the same time, there are large amount of agricultural residues as well as industrial wastes that are of low or negative value (due to costs of current effluent disposal methods. Dilute sulfuric acid pretreatment of elephant grass and wood residues for the enzymatic hydrolysis of cellulose has been investigated in this study.    Elephant grass (agricultural residue and sawdust (Pulp and Paper Industry waste with a small particulate size were treated using different dilute sulfuric acid concentrations at a temperature  of 140-170°C within 0.5-3 hours. The appropriate pretreatment conditions give the highest yield of soluble saccharides and total reducing sugars.

  10. Structure of the enzymatically synthesized fructan inulin

    International Nuclear Information System (INIS)

    Heyer, A.G.; Schroeer, B.; Radosta, S.; Wolff, D.; Czapla, S.; Springer, J.

    1998-01-01

    Construction, purification and characterization of a fusion protein of maltose-binding protein of Escherichia coli and the fructosyltransferase of Streptococcus mutans is described. With the purified protein, in vitro synthesis of inulin was performed. The obtained polysaccharide was characterized by high-performance size-exclusion chromatography (HPSEC) and static light scattering (SLS) in dilute aqueous and dimethyl sulfoxide solution. For all samples very high molecular weights between 60x10 6 and 90x10 6 g/mol and a remarkable small polydispersity index of 1.1 have been determined. Small root-mean-square radii of gyration point to a compact conformation in dilute solution. No difference between native and enzymatically synthesized inulin was observed by X-ray powder diffraction and thermoanalysis of solid samples. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  11. Structure of the enzymatically synthesized fructan inulin

    Energy Technology Data Exchange (ETDEWEB)

    Heyer, A.G.; Schroeer, B. [Max-Planck-Institut fuer Molekulare Pflanzenphysiologie, Karl-Liebknecht-Str. 25, 14476 Golm (Germany); Radosta, S. [Fraunhofer-Institut fuer Angewandte Polymerforschung, Postfach 126, 14504 Teltow (Germany); Wolff, D.; Czapla, S.; Springer, J. [Technische Universitaet Berlin, FG Makromolekulare Chemie, Str. des 17. Juni 135, 10623 Berlin (Germany)

    1998-12-15

    Construction, purification and characterization of a fusion protein of maltose-binding protein of Escherichia coli and the fructosyltransferase of Streptococcus mutans is described. With the purified protein, in vitro synthesis of inulin was performed. The obtained polysaccharide was characterized by high-performance size-exclusion chromatography (HPSEC) and static light scattering (SLS) in dilute aqueous and dimethyl sulfoxide solution. For all samples very high molecular weights between 60x10{sup 6} and 90x10{sup 6} g/mol and a remarkable small polydispersity index of 1.1 have been determined. Small root-mean-square radii of gyration point to a compact conformation in dilute solution. No difference between native and enzymatically synthesized inulin was observed by X-ray powder diffraction and thermoanalysis of solid samples. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  12. Enzymatic hydrolysis of corn bran arabinoxylan

    DEFF Research Database (Denmark)

    Agger, Jane

    as a model substrate because it represents a readily available agroindustrial side product with upgrading potentials. Corn bran originates from the wet-milling process in corn starch processing, is the outmost layers of the corn kernel and is particularly rich in pentose monosaccharides comprising the major...... in a complex and ridig cell wall structure. This thesis contains a thorough examination of the monosaccharide and structural composition of corn bran, which is used to assess and apply the relevant mono component enzyme preparations. In this way, the aim is to obtain the most effective minimal enzymatic......, especially with respect to xylose and glucose release, but vast amounts of the valuable monosaccharides are lost during this pretreatment and this is especially evident for arabinose. From a scientific point of view acid catalysed pretreatment renders the substrate in a state of disruption where assessment...

  13. Rapid enzymatic analysis of plasma for tyrosine.

    Science.gov (United States)

    Shimizu, H; Taniguchi, K; Sugiyama, M; Kanno, T

    1990-01-01

    In this rapid, simple, and convenient enzymatic method for measurement of tyrosine in plasma, tyrosine is converted to tyramine by action of tyrosine decarboxylase (EC 4.1.1.25) and the tyramine produced is oxidized to p-hydroxybenzyl aldehyde and hydrogen peroxide by action of tyramine oxidase (EC 1.4.3.9). The hydrogen peroxide is reacted with 4-aminoantipyrine and N-ethyl-N-(2-hydroxy-3-sulfopropyl)-m-toluidine in the presence of peroxidase (EC 1.11.1.7) to obtain quinoneimine dye, the absorbance of which is measured at 570 nm. Thus tyrosine is measured in the visible range. The CV was 4.6% or less, and the measurement was unaffected by other amino acids, except for phenylalanine. The values obtained (y) correlated well with those obtained with an amino acid analyzer (x): y = 0.902x + 3.92 mumol/L (Syx = 12.3; r = 0.985; n = 54).

  14. Radiation degradation and the subsequent enzymatic hydrolysis of waste paper

    International Nuclear Information System (INIS)

    Kamakura, M.; Kaetsu, I.

    1982-01-01

    Various studies have been carried out to find methods for the pretreatment of waste cellulosic materials to make them more susceptible to enzymatic hydrolysis. In the work reported here, the effects of preirradiating waste papers on subsequent enzymatic hydrolysis have been studied

  15. The Enzymatic Oxidation of Graphene Oxide

    Science.gov (United States)

    Kotchey, Gregg P.; Allen, Brett L.; Vedala, Harindra; Yanamala, Naveena; Kapralov, Alexander A.; Tyurina, Yulia Y.; Klein-Seetharaman, Judith; Kagan, Valerian E.; Star, Alexander

    2011-01-01

    Two-dimensional graphitic carbon is a new material with many emerging applications, and studying its chemical properties is an important goal. Here, we reported a new phenomenon – the enzymatic oxidation of a single layer of graphitic carbon by horseradish peroxidase (HRP). In the presence of low concentrations of hydrogen peroxide (~40 µM), HRP catalyzed the oxidation of graphene oxide, which resulted in the formation of holes on its basal plane. During the same period of analysis, HRP failed to oxidize chemically reduced graphene oxide (RGO). The enzymatic oxidation was characterized by Raman, UV-Vis, EPR and FT-IR spectroscopy, TEM, AFM, SDS-PAGE, and GC-MS. Computational docking studies indicated that HRP was preferentially bound to the basal plane rather than the edge for both graphene oxide and RGO. Due to the more dynamic nature of HRP on graphene oxide, the heme active site of HRP was in closer proximity to graphene oxide compared to RGO, thereby facilitating the oxidation of the basal plane of graphene oxide. We also studied the electronic properties of the reduced intermediate product, holey reduced graphene oxide (hRGO), using field-effect transistor (FET) measurements. While RGO exhibited a V-shaped transfer characteristic similar to a single layer of graphene that was attributed to its zero band gap, hRGO demonstrated a p-type semiconducting behavior with a positive shift in the Dirac points. This p-type behavior rendered hRGO, which can be conceptualized as interconnected graphene nanoribbons, as a potentially attractive material for FET sensors. PMID:21344859

  16. Characterizing Enzymatic Deposition for Microelectrode Neurotransmitter Detection

    Energy Technology Data Exchange (ETDEWEB)

    Hosein, W. K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Yorita, A. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Tolosa, V. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-08-12

    The enzyme immobilization process, one step in creating an enzymatic biosensor, was characterized and analyzed as a function of its physical properties. The neural glutamic biosensor is a flexible device, effectively minimizing trauma to the area of implantation. The Multielectrode Array (MEA) is composed primarily of a proprietary polymer which has been successfully implanted into human subjects in recent years. This polymer allows the device the pliability that other devices normally lack, though this poses some challenges to implantation. The electrodes are made of Platinum (Pt), and can range in number from eight to thirty two electrodes per device. These electrodes are electroplated with a semipermeable polymer layer to improve selectivity of the electrode to the neurotransmitter of interest, in this case glutamate. A signal is created from the interaction of glutamate in the brain with the glutamate oxidase (GluOx) which is immobilized on the surface of the electrode by using crosslinking chemistry in conjunction with glutaraldehyde and Bovine Serum Albumin (BSA). The glutamate is oxidized by glutamate oxidase, producing α-ketoglutarate and hydrogen peroxide (H2O2) as a by-product. The production of H2O2 is crucial for detection of the presence of the glutamate within the enzymatic coating, as it diffuses through the enzyme layer and oxidizes at the surface of the electrode. This oxidation is detectable by measurable change in the current using amperometry. Hence, the MEA allows for in vivo monitoring of neurotransmitter activity in real time. The sensitivity of the sensor to these neurotransmitters is dependent on the thickness of the layer, which is investigated in these experiments in order to optimize the efficacy of the device to detecting the substrate, once implanted.

  17. Stochastic amplification and signaling in enzymatic futile cycles through noise-induced bistability with oscillations

    Science.gov (United States)

    Samoilov, Michael; Plyasunov, Sergey; Arkin, Adam P.

    2005-02-01

    Stochastic effects in biomolecular systems have now been recognized as a major physiologically and evolutionarily important factor in the development and function of many living organisms. Nevertheless, they are often thought of as providing only moderate refinements to the behaviors otherwise predicted by the classical deterministic system description. In this work we show by using both analytical and numerical investigation that at least in one ubiquitous class of (bio)chemical-reaction mechanisms, enzymatic futile cycles, the external noise may induce a bistable oscillatory (dynamic switching) behavior that is both quantitatively and qualitatively different from what is predicted or possible deterministically. We further demonstrate that the noise required to produce these distinct properties can itself be caused by a set of auxiliary chemical reactions, making it feasible for biological systems of sufficient complexity to generate such behavior internally. This new stochastic dynamics then serves to confer additional functional modalities on the enzymatic futile cycle mechanism that include stochastic amplification and signaling, the characteristics of which could be controlled by both the type and parameters of the driving noise. Hence, such noise-induced phenomena may, among other roles, potentially offer a novel type of control mechanism in pathways that contain these cycles and the like units. In particular, observations of endogenous or externally driven noise-induced dynamics in regulatory networks may thus provide additional insight into their topology, structure, and kinetics. network motif | signal transduction | chemical reaction | synthetic biology | systems biology

  18. Conversion of Cassava Starch to Produce Glucose and Fructose by Enzymatic Process Using Microwave Heating

    Directory of Open Access Journals (Sweden)

    Sumardiono Siswo

    2018-01-01

    Full Text Available In this study, variation of glycosidase enzyme concentration and saccharification time on enzymatic hydrolysis using microwave have been investigated. Concentration and kinetic parameters rate of glucose and fructose were analyzed. Cassava starch was liquefied and gelatinized by microwave at 80°C. The gelatinized starch was saccharified at 60°C using (0.2;0.4;0.6;0.8;1% (w/v glycosidase enzyme for 24, 48 and 72 hours. The glucose which has been saccharified with 1% glycosidase enzyme for 72 hours gave highest conversion 66.23 %. The optimization process by multilevel reaction gave the highest conversion at enzyme concentrations 0.88 %and saccharification time 29 hours that 68.82%. The highest conversion of glucose was isomerized to fructose. The fructose which has been isomerized for 180 minutes gave highest conversion 20.05 %. The kinetics enzymatic reaction was approached and determined by Michaelis - Menten equation, Km and Vmax of reaction for glucose 22.94 g/L; 2.70 g/L hours and for fructose 3.39 g/L; 0.38 g/L. min respectively.

  19. Role of conformational dynamics in kinetics of an enzymatic cycle in a nonequilibrium steady state

    Science.gov (United States)

    Min, Wei; Xie, X. Sunney; Bagchi, Biman

    2009-08-01

    Enzyme is a dynamic entity with diverse time scales, ranging from picoseconds to seconds or even longer. Here we develop a rate theory for enzyme catalysis that includes conformational dynamics as cycling on a two-dimensional (2D) reaction free energy surface involving an intrinsic reaction coordinate (X) and an enzyme conformational coordinate (Q). The validity of Michaelis-Menten (MM) equation, i.e., substrate concentration dependence of enzymatic velocity, is examined under a nonequilibrium steady state. Under certain conditions, the classic MM equation holds but with generalized microscopic interpretations of kinetic parameters. However, under other conditions, our rate theory predicts either positive (sigmoidal-like) or negative (biphasic-like) kinetic cooperativity due to the modified effective 2D reaction pathway on X-Q surface, which can explain non-MM dependence previously observed on many monomeric enzymes that involve slow or hysteretic conformational transitions. Furthermore, we find that a slow conformational relaxation during product release could retain the enzyme in a favorable configuration, such that enzymatic turnover is dynamically accelerated at high substrate concentrations. The effect of such conformation retainment in a nonequilibrium steady state is evaluated.

  20. Enzymatic hydrolysis of biomimetic bacterial cellulose-hemicellulose composites.

    Science.gov (United States)

    Penttilä, Paavo A; Imai, Tomoya; Hemming, Jarl; Willför, Stefan; Sugiyama, Junji

    2018-06-15

    The production of biofuels and other chemicals from lignocellulosic biomass is limited by the inefficiency of enzymatic hydrolysis. Here a biomimetic composite material consisting of bacterial cellulose and wood-based hemicelluloses was used to study the effects of hemicelluloses on the enzymatic hydrolysis with a commercial cellulase mixture. Bacterial cellulose synthesized in the presence of hemicelluloses, especially xylan, was found to be more susceptible to enzymatic hydrolysis than hemicellulose-free bacterial cellulose. The reason for the easier hydrolysis could be related to the nanoscale structure of the substrate, particularly the packing of cellulose microfibrils into ribbons or bundles. In addition, small-angle X-ray scattering was used to show that the average nanoscale morphology of bacterial cellulose remained unchanged during the enzymatic hydrolysis. The reported easier enzymatic hydrolysis of bacterial cellulose produced in the presence of wood-based xylan offers new insights to overcome biomass recalcitrance through genetic engineering. Copyright © 2018 Elsevier Ltd. All rights reserved.

  1. Continuous and discreet methods in the aggregation and des fuzzy stages of a diffuse controller of neutron power; Metodos continuo y discreto en las etapas de agregacion y desdifusificacion de un controlador disfuso de potencia neutronica

    Energy Technology Data Exchange (ETDEWEB)

    Najera H, M.C.; Benitez R, J.S. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)

    2003-07-01

    The results of a comparative study are presented of: to) A denominated diffuse controller 'exact', designed by means of an innovative method that determines analytically so much the group of exit resultant in the aggregation stage like the de fuzzy process, and b) a diffuse controller denominated 'discreet' based on the discretization of the variable of having left as much for the aggregation as for the de fuzzy. These stages incorporated to the control algorithms whose objective is the ascent and regulation of the neutron power, carrying out an analysis of its performance. (Author)

  2. Optimization of enzymatic hydrolysis of guar gum using response surface methodology.

    Science.gov (United States)

    Mudgil, Deepak; Barak, Sheweta; Khatkar, B S

    2014-08-01

    Guar gum is a polysaccharide obtained from guar seed endosperm portion. Enzymatically hydrolyzed guar gum is low in viscosity and has several health benefits as dietary fiber. In this study, response surface methodology was used to determine the optimum conditions for hydrolysis that give minimum viscosity of guar gum. Central composite was employed to investigate the effects of pH (3-7), temperature (20-60 °C), reaction time (1-5 h) and cellulase concentration (0.25-1.25 mg/g) on viscosity during enzymatic hydrolysis of guar (Cyamopsis tetragonolobus) gum. A second order polynomial model was developed for viscosity using regression analysis. Results revealed statistical significance of model as evidenced from high value of coefficient of determination (R(2) = 0.9472) and P < 0.05. Viscosity was primarily affected by cellulase concentration, pH and hydrolysis time. Maximum viscosity reduction was obtained when pH, temperature, hydrolysis time and cellulase concentration were 6, 50 °C, 4 h and 1.00 mg/g, respectively. The study is important in optimizing the enzymatic process for hydrolysis of guar gum as potential source of soluble dietary fiber for human health benefits.

  3. Effect of the steam explosion pretreatment on enzymatic hydrolysis of eucalyptus wood and sweet sorghum baggages

    International Nuclear Information System (INIS)

    Negro, M. J.; Martinez, J. M.; Manero, J.; Saez, F.; Martin, C.

    1991-01-01

    The effect of steam explosion treatment on the enzymatic hydrolysis yield of two different lignocellulosic substrates is studied. Raw materials have been pretreated in a pilot plant designed to work in batch and equipped with a reactor vessel of 2 1 working volume where biomass was heated at the desired temperature and then exploded and recovered in a cyclone. Temperatures from 190 to 230 degree celsius and reaction times from 2 to 8 min. have been assayed. The efficiency of the steam explosion treatment has been evaluated on the composition of the lignocellulosic materials as well as on their enzymatic hydrolysis yield using a cellulolytic complex from T. reesel. Results show a high solubilization rate of hemicelluloses and variable losses of cellulose and lignin depending on the conditions tested. Enzymatic hydrolysis yields of both substrates experimented remarkable increments, corresponding the highest values obtained to 210 degree celsius; 2 min. and 21O degree celsius; 4 min. for sorghum bagasse and eucalyptus wood respectively. (Author) 13 refs

  4. Effect of the steam explosion pretreatment on enzymatic hydrolysis of eucalyptus wood and sweet sorghum bagasse

    International Nuclear Information System (INIS)

    Negro, M.J.; Martinez, J.M.; Manero, J.; Saez, F.; Martin, C.

    1990-01-01

    The effect of steam explosion treatment on the enzymatic hydrolysis yield of two different lignocellulosic substrates is studied. Raw materials have been pretreated in a pilot plant designed to work in batch and equiped with a reactor vessel of 2 1 working volume where biomass was heated at the desired temperature and then exploded and recovered in a cyclone. Temperatures from 190 to 230 o C and reaction times from 2 to 8 min. have been assayed. The efficiency of the steam explosion treatment has been evaluated on the composition of the lignocellulosic materials as well as on their enzymatic hydrolysis yield using a cellulolytic complex from T. reesei. Results show a high solubilization rate of hemicelluloses ands variable losses of cellulose and lignin depending on the conditions tested. Enzymatic hydrolysis yields of both substrates experimented remarkable increments, correspondig the highest values obtained to 210 o C; 2 min. and 210 o C; 4 min. for sorghum bagasse and eucaliptus wood respectivelly. (Author). 13 refs

  5. Pretreatment of corn stover using wet oxidation to enhance enzymatic digestibility

    DEFF Research Database (Denmark)

    Varga, E.; Schmidt, A.S.; Reczey, K.

    2003-01-01

    was about 85%. Decreasing the hydrolysis temperature to 40degreesC increased hydrolysis time from 24 to 72 h. Decreasing the enzyme loading to 5 FPU/g of DM biomass slightly decreased the enzymatic conversion from 83.4 to 71%. Thus, enzyme loading can be reduced without significantly affecting......) was investigated to enhance the enzymatic digestibility of corn stover. Six different combinations of reaction temperature, time, and pH were applied. The best conditions (60 g/L of corn stover, 195degreesC, 15 min, 12 bar O-2, 2 g/L of Na2CO) increased the enzymatic conversion of corn stover four times, compared...... to untreated material. Under these conditions 60% of hemicellulose and 30% of lignin were solubilized, whereas 90% of cellulose remained in the solid fraction. After 24-h hydrolysis at 50degreesC using 25 filter paper units (FPU)/g of drymatter (DM) biomass, the achieved conversion of cellulose to glucose...

  6. Micro-mechanical model for the tension-stabilized enzymatic degradation of collagen tissues

    Science.gov (United States)

    Nguyen, Thao; Ruberti, Jeffery

    We present a study of how the collagen fiber structure influences the enzymatic degradation of collagen tissues. Experiments of collagen fibrils and tissues show that mechanical tension can slow and halt enzymatic degradation. Tissue-level experiments also show that degradation rate is minimum at a stretch level coincident with the onset of strain-stiffening in the stress response. To understand these phenomena, we developed a micro-mechanical model of a fibrous collagen tissue undergoing enzymatic degradation. Collagen fibers are described as sinusoidal elastica beams, and the tissue is described as a distribution of fibers. We assumed that the degradation reaction is inhibited by the axial strain energy of the crimped collagen fibers. The degradation rate law was calibrated to experiments on isolated single fibrils from bovine sclera. The fiber crimp and properties were fit to uniaxial tension tests of tissue strips. The fibril-level kinetic and tissue-level structural parameters were used to predict tissue-level degradation-induced creep rate under a constant applied force. We showed that we could accurately predict the degradation-induce creep rate of the pericardium and cornea once we accounted for differences in the fiber crimp structure and properties.

  7. Blocked Enzymatic Etching of Gold Nanorods: Application to Colorimetric Detection of Acetylcholinesterase Activity and Its Inhibitors.

    Science.gov (United States)

    Saa, Laura; Grinyte, Ruta; Sánchez-Iglesias, Ana; Liz-Marzán, Luis M; Pavlov, Valeri

    2016-05-04

    The anisotropic morphology of gold nanorods (AuNRs) has been shown to lead to nonuniform ligand distribution and preferential etching through their tips. We have recently demonstrated that this effect can be achieved by biocatalytic oxidation with hydrogen peroxide, catalyzed by the enzyme horseradish peroxidase (HRP). We report here that modification of AuNRs with thiol-containing organic molecules such as glutathione and thiocholine hinders enzymatic AuNR etching. Higher concentrations of thiol-containing molecules in the reaction mixture gradually decrease the rate of enzymatic etching, which can be monitored by UV-vis spectroscopy through changes in the AuNR longitudinal plasmon band. This effect can be applied to develop novel optical assays for acetylcholinesterase (AChE) activity. The biocatalytic hydrolysis of acetylthiocholine by AChE yields thiocholine, which prevents enzymatic AuNR etching in the presence of HRP. Additionally, the same bioassay can be used for the detection of nanomolar concentrations of AChE inhibitors such as paraoxon and galanthamine.

  8. Next-Generation Catalysis for Renewables: Combining Enzymatic with Inorganic Heterogeneous Catalysis for Bulk Chemical Production

    DEFF Research Database (Denmark)

    Vennestrøm, Peter Nicolai Ravnborg; Christensen, C.H.; Pedersen, S.

    2010-01-01

    chemical platform under different conditions than those conventionally employed. Indeed, new process and catalyst concepts need to be established. Both enzymatic catalysis (biocatalysis) and heterogeneous inorganic catalysis are likely to play a major role and, potentially, be combined. One type...... of combination involves one-pot cascade catalysis with active sites from bio- and inorganic catalysts. In this article the emphasis is placed specifically on oxidase systems involving the coproduction of hydrogen peroxide, which can be used to create new in situ collaborative oxidation reactions for bulk...

  9. Optimization of enzymatic hydrolysis of guar gum using response surface methodology

    OpenAIRE

    Mudgil, Deepak; Barak, Sheweta; Khatkar, B. S.

    2012-01-01

    Guar gum is a polysaccharide obtained from guar seed endosperm portion. Enzymatically hydrolyzed guar gum is low in viscosity and has several health benefits as dietary fiber. In this study, response surface methodology was used to determine the optimum conditions for hydrolysis that give minimum viscosity of guar gum. Central composite was employed to investigate the effects of pH (3–7), temperature (20–60 °C), reaction time (1–5 h) and cellulase concentration (0.25–1.25 mg/g) on viscosity d...

  10. Enzymatic production of alkyl esters through alcoholysis: A critical evaluation of lipases and alcohols

    DEFF Research Database (Denmark)

    Li, Deng; Xu, Xuebing; Gudmundur G, Haraldsson

    2005-01-01

    This paper focuses on a detailed evaluation of commercially available immobilized lipases and simple monohydric alcohols for the production of alkyl esters from sunflower oil by enzymatic alcoholysis. Six lipases were tested with seven alcohols, including straight and branched-chain primary...... in an increased degree of conversion for all lipases except Novozym 435. The secondary alcohol 2-propanol significantly reduced the alcoholysis reaction with all lipases; however, the branch-chain isobutanol was more advantageous than linear 1-butanol for Novozym 435, Lipozyme RM IM, and Lipase PS-C. Many...

  11. Lignocellulose pretreatment technologies affect the level of enzymatic cellulose oxidation by LPMO

    DEFF Research Database (Denmark)

    Rodríguez-Zúñiga, Ursula Fabiola; Cannella, David; de Campos Giordano, Roberto

    2015-01-01

    of the cellulose oxidizing enzyme lytic polysaccharide monooxygenase (LPMO). The highest activity of LPMO was observed for the hydrothermally pretreated biomasses, which also contained the highest level of lignin. All hydrolysis were done at high dry matter levels, using a commercial enzyme preparation containing......Sugarcane bagasse, corn stover, and wheat straw are among the most available resources for production of cellulosic ethanol. For these biomasses we study the influence of pre-treatment methods on the chemical composition, as well as on the subsequent reactions of enzymatic hydrolysis and oxidation...

  12. Enzymatic Synthesis of Esculin Ester in Ionic Liquids Buffered with Organic Solvents

    DEFF Research Database (Denmark)

    Hu, Yifan; Guo, Zheng; Lue, Bena-Marie

    2009-01-01

    The enzymatic esterification of esculin catalyzed by Candida antarctica lipase B (Novozym 435) was carried out in ionic liquid (IL)-organic solvent mixed systems in comparison with individual systems. The reaction behaviors in IL-organic solvents were systemically evaluated using acetone as a model...... in IL-acetone mixtures made it possible to improve the solubility of esculin while the effects of ILs on lipase activity were minimized. Following the benignity of ILs to lipase activity, the anions of ILs were ranked in the order as [Tf2N](-) > [PF6](-) > [BF4](-) > [CF3SO3](-) > [C4F9SO3](-) > [TAF...

  13. Reactor design for minimizing product inhibition during enzymatic lignocellulose hydrolysis: I. Significance and mechanism of cellobiose and glucose inhibition on cellulolytic enzymes

    DEFF Research Database (Denmark)

    Andric, Pavle; Meyer, Anne S.; Jensen, Peter Arendt

    2010-01-01

    Achievement of efficient enzymatic degradation of cellulose to glucose is one of the main prerequisites and one of the main challenges in the biological conversion of lignocellulosic biomass to liquid fuels and other valuable products. The specific inhibitory interferences by cellobiose and glucose...... on enzyme-catalyzed cellulose hydrolysis reactions impose significant limitations on the efficiency of lignocellulose conversion especially at high-biomass dry matter conditions. To provide the base for selecting the optimal reactor conditions, this paper reviews the reaction kinetics, mechanisms......, and significance of this product inhibition, notably the cellobiose and glucose inhibition, on enzymatic cellulose hydrolysis. Particular emphasis is put on the distinct complexity of cellulose as a substrate, the multi-enzymatic nature of the cellulolytic degradation, and the particular features of cellulase...

  14. Immobilization of Lipase using Alginate Hydrogel Beads and Enzymatic Evaluation in Hydrolysis of p-Nitrophenol Butyrate

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shuang; Shang, Wenting; Yang, Xiaoxi; Zhang, Shujuan; Zhang, Xiaogang; Chen, Jiawei [Renmin Univ. of China, Beijing (China)

    2013-09-15

    The immobilization of enzyme is one of the key issues both in the field of enzymatic research and industrialization. In this work, we reported a facile method to immobilize Candida Antarctica lipase B (CALB) in alginate carrier. In the presence of calcium cation, the enzyme-alginate suspension could be cross-linked to form beads with porous structure at room temperature, and the enzyme CALB was dispersed in the beads. Activity of the enzyme-alginate composite was verified by enzymatic hydrolysis reaction of p-nitrophenol butyrate in aqueous phase. The effects of reaction parameters such as temperature, pH, embedding and lyophilized time on the reactive behavior were discussed. Reuse cycle experiments for the hydrolysis of p-nitrophenol butyrate demonstrated that activity of the enzyme-alginate composite was maintained without marked deactivation up to 6 repeated cycles.

  15. Enzymatic exchange of sulphur between cysteine and hydrogen sulphide in the yolk sac of an incubated bird's egg

    International Nuclear Information System (INIS)

    Chapeville, F.; Fromageot, P.

    1960-01-01

    Previous work has shown that the formation of cysteic acid from sulphate in incubated hen's eggs is due to the following reactions: a) reduction of sulphate to sulphite by the yolk sac endoderm cells; b) synthesis of cysteic acid from the sulphite in the presence of cysteine with liberation of hydrogen sulphide: HS-CH 2 -CH(NH 2 )-COOH + SO 3 H - → H 2 S + - O 3 S-CH 2 -CH(NH 2 )-COOH (1). The enzymatic system responsible for this reaction is localized on the yolk sac endoderm and in the yolk. It may be wondered whether reaction (1) is not made up of two consecutive reactions, one of which is reversible: HS-CH 2 -CH(NH 2 )-COOH ↔ H 2 S + organic chain (2) and organic chain + SO 3 H - → - O 3 S-CH 2 -CH(NH 2 )-COOH (3). It would then be clear why the addition of sulphite displaces the equilibrium towards the production of cysteic acid and hydrogen sulphide. If this is the case, the addition of ordinary cysteine and of marked hydrogen sulphide to the biological medium should make it possible to detect the formation of 35 S cysteine. The present work shows that the desulphurization of the cysteine (reaction 2) by the yolk sac + the yolk is in fact a reversible reaction, and that an enzymatic exchange occurs between the sulphur of the cysteine and that of the hydrogen sulphide. (author) [fr

  16. Oxidative degradation and non-enzymatic browning due to the interaction between oxidised lipids and primary amine groups in different marine PL emulsions

    DEFF Research Database (Denmark)

    Lu, Henna Fung Sieng; Nielsen, Nina Skall; Baron, Caroline P.

    2012-01-01

    investigated through the measurement of secondary volatile compounds by solid-phase microextraction (SPME) and dynamic headspace (DHS) connected to gas chromatography (GC–MS). Non-enzymatic browning reactions were investigated through the measurement of Strecker derived volatiles, colour changes and pyrrole...

  17. Enhanced Enzymatic Synthesis of a Cephalosporin, Cefadroclor, in the Presence of Organic Co-solvents.

    Science.gov (United States)

    Liu, Kun; Li, Sha; Pang, Xiao; Xu, Zheng; Li, Dengchao; Xu, Hong

    2017-05-01

    In this study, we investigated the enzymatic synthesis of a semi-synthetic cephalosporin, cefadroclor, from 7-aminodesacetoxymethyl-3-chlorocephalosporanic acid (7-ACCA) and p-OH-phenylglycine methyl ester (D-HPGM) using immobilized penicillin G acylase (IPA) in organic co-solvents. Ethylene glycol (EG) was employed as a component of the reaction mixture to improve the yield of cefadroclor. EG was found to increase the yield of cefadroclor by 15-45%. An investigation of altered reaction parameters including type and concentration of organic solvents, pH of reaction media, reaction temperature, molar ratio of substrates, enzyme loading, and IPA recycling was carried out in the buffer mixture. The best result was a 76.5% conversion of 7-ACCA, which was obtained from the reaction containing 20% EG (v/v), D-HPGM to 7-ACCA molar ratio of 4:1 and pH 6.2, catalyzed by 16 IU mL -1 IPA at 20 °C for 10 h. Under the optimum conditions, no significant loss of IPA activity was found after seven repeated reaction cycles. In addition, cefadroclor exhibited strong inhibitory activity against yeast, Bacillus subtilis NX-2, and Escherichia coli and weaker activity against Staphylococcus aureus and Pseudomonas aeruginosa. Cefadroclor is a potential antibiotic with activity against common pathogenic microorganisms.

  18. Application of extended Kalman filter to identification of enzymatic deactivation.

    Science.gov (United States)

    Caminal, G; Lafuente, J; López-Santín, J; Poch, M; Solà, C

    1987-02-01

    A recursive estimation scheme, the Extended Kalman Filter (EKF) technique, was applied to study enzymatic deactivation in the enzymatic hydrolysis of pretreated cellulose using a model previously developed by the authors. When no deactivation model was assumed, the results showed no variation with time for all the model parameters except for the maximum rate of cellobiose-to-glucose conversion (r'(m)).The r'(m) variation occurred in two zones with a grace period. A new model of enzymatic hydrolysis of pretreated cellulose deactivation was proposed and validated showing better behavior than the old deactivation model. This approach allows one to study enzyme deactivation without additional experiments and within operational conditions.

  19. Enzymatic Cellulose Palmitate Synthesis Using Immobilized Lipase

    Directory of Open Access Journals (Sweden)

    Anna Roosdiana

    2017-06-01

    Full Text Available Bacterial cellulose can be modified by esterification using palmitic acid and Mucor miehei  lipase  as catalyst. The purpose of this research was to determine the optimum conditions of esterification reaction of cellulose and palmitic acid . The esterification reaction was carried out at the time variation  of  6, 12, 18, 24 and 30 hours and the mass ratio of cellulose: palmitic acid (1: 11: 2, 1: 3, 1: 4, 1: 5,1:6 at 50 °C. The   cellulose palmitate  was examined  its  physical and chemical properties by using FTIR spectrophotometer, XRD, bubble point test and saponification  apparatus. The results showed that the optimum reaction time of esterification reaction of cellulose and palmitic acid occurred within 24 hours and the mass ratio of cellulose: palmitic acid was 1: 3 resulting in DS of  0.376 with  swelling index of 187 %, crystallinity index of 61.95%,  and Φ porous of 2.40 μm. Identification of functional groups using FTIR spectrophotometer showed that C=O ester group  was observed at 1737.74 cm-1 and strengthened  by  the appearance of C-O ester peak at 1280 cm-1. The conclusion of this study is reaction time and reactant ratio influence significantly the DS of cellulose ester.

  20. Aqueous enzymatic extraction of Moringa oleifera oil.

    Science.gov (United States)

    Mat Yusoff, Masni; Gordon, Michael H; Ezeh, Onyinye; Niranjan, Keshavan

    2016-11-15

    This paper reports on the extraction of Moringa oleifera (MO) oil by using aqueous enzymatic extraction (AEE) method. The effect of different process parameters on the oil recovery was discovered by using statistical optimization, besides the effect of selected parameters on the formation of its oil-in-water cream emulsions. Within the pre-determined ranges, the use of pH 4.5, moisture/kernel ratio of 8:1 (w/w), and 300stroke/min shaking speed at 40°C for 1h incubation time resulted in highest oil recovery of approximately 70% (goil/g solvent-extracted oil). These optimized parameters also result in a very thin emulsion layer, indicating minute amount of emulsion formed. Zero oil recovery with thick emulsion were observed when the used aqueous phase was re-utilized for another AEE process. The findings suggest that the critical selection of AEE parameters is key to high oil recovery with minimum emulsion formation thereby lowering the load on the de-emulsification step. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Enzymatic Systems for Cellulose Acetate Degradation

    Directory of Open Access Journals (Sweden)

    Oskar Haske-Cornelius

    2017-09-01

    Full Text Available Cellulose acetate (CA-based materials, like cigarette filters, contribute to landscape pollution challenging municipal authorities and manufacturers. This study investigates the potential of enzymes to degrade CA and to be potentially incorporated into the respective materials, enhancing biodegradation. Deacetylation studies based on Liquid Chromatography-Mass Spectrometry-Time of Flight (LC-MS-TOF, High Performance Liquid Chromatography (HPLC, and spectrophotometric analysis showed that the tested esterases were able to deacetylate the plasticizer triacetin (glycerol triacetate and glucose pentaacetate (cellulose acetate model compound. The most effective esterases for deacetylation belong to the enzyme family 2 (AXE55, AXE 53, GAE, they deacetylated CA with a degree of acetylation of up to 1.8. A combination of esterases and cellulases showed synergistic effects, the absolute glucose recovery for CA 1.8 was increased from 15% to 28% when an enzymatic deacetylation was performed. Lytic polysaccharide monooxygenase (LPMO, and cellobiohydrolase were able to cleave cellulose acetates with a degree of acetylation of up to 1.4, whereas chitinase showed no activity. In general, the degree of substitution, chain length, and acetyl group distribution were found to affect CA degradation. This study shows that, for a successful enzyme-based deacetylation system, a cocktail of enzymes, which will randomly cleave and generate shorter CA fragments, is the most suitable.

  2. Quasielastic reactions

    International Nuclear Information System (INIS)

    Henning, W.

    1979-01-01

    Quasielastic reaction studies, because of their capability to microscopically probe nuclear structure, are still of considerable interest in heavy-ion reactions. The recent progress in understanding various aspects of the reaction mechanism make this aim appear closer. The relation between microscopic and macroscopic behavior, as suggested, for example, by the single proton transfer data to individual final states or averaged excitation energy intervals, needs to be explored. It seems particularly useful to extend measurements to higher incident energies, to explore and understand nuclear structure aspects up to the limit of the energy range where they are important

  3. Enzymatic hydrolysis of organic phosphorus in swine manure and soil.

    Science.gov (United States)

    He, Zhongqi; Griffin, Timothy S; Honeycutt, C Wayne

    2004-01-01

    Organic phosphorus (Po) exists in many chemical forms that differ in their susceptibility to hydrolysis and, therefore, bioavailability to plants and microorganisms. Identification and quantification of these forms may significantly contribute to effective agricultural P management. Phosphatases catalyze reactions that release orthophosphate (Pi) from Po compounds. Alkaline phosphatase in tris-HCl buffer (pH 9.0), wheat (Triticum aestivum L.) phytase in potassium acetate buffer (pH 5.0), and nuclease P1 in potassium acetate buffer (pH 5.0) can be used to classify and quantify Po in animal manure. Background error associated with different pH and buffer systems is observed. In this study, we improved the enzymatic hydrolysis approach and tested its applicability for investigating Po in soils, recognizing that soil and manure differ in numerous physicochemical properties. We applied (i) acid phosphatase from potato (Solanum tuberosum L.), (ii) acid phosphatases from both potato and wheat germ, and (iii) both enzymes plus nuclease P1 to identify and quantify simple labile monoester P, phytate (myo-inositol hexakis phosphate)-like P, and DNA-like P, respectively, in a single pH/buffer system (100 mM sodium acetate, pH 5.0). This hydrolysis procedure released Po in sequentially extracted H2O, NaHCO3, and NaOH fractions of swine (Sus scrofa) manure, and of three sandy loam soils. Further refinement of the approach may provide a universal tool for evaluating hydrolyzable Po from a wide range of sources.

  4. Nano-yarn carbon nanotube fiber based enzymatic glucose biosensor

    International Nuclear Information System (INIS)

    Zhu Zhigang; Burugapalli, Krishna; Moussy, Francis; Song, Wenhui; Li Yali; Zhong Xiaohua

    2010-01-01

    A novel brush-like electrode based on carbon nanotube (CNT) nano-yarn fiber has been designed for electrochemical biosensor applications and its efficacy as an enzymatic glucose biosensor demonstrated. The CNT nano-yarn fiber was spun directly from a chemical-vapor-deposition (CVD) gas flow reaction using a mixture of ethanol and acetone as the carbon source and an iron nano-catalyst. The fiber, 28 μm in diameter, was made of bundles of double walled CNTs (DWNTs) concentrically compacted into multiple layers forming a nano-porous network structure. Cyclic voltammetry study revealed a superior electrocatalytic activity for CNT fiber compared to the traditional Pt-Ir coil electrode. The electrode end tip of the CNT fiber was freeze-fractured to obtain a unique brush-like nano-structure resembling a scale-down electrical 'flex', where glucose oxidase (GOx) enzyme was immobilized using glutaraldehyde crosslinking in the presence of bovine serum albumin (BSA). An outer epoxy-polyurethane (EPU) layer was used as semi-permeable membrane. The sensor function was tested against a standard reference electrode. The sensitivities, linear detection range and linearity for detecting glucose for the miniature CNT fiber electrode were better than that reported for a Pt-Ir coil electrode. Thermal annealing of the CNT fiber at 250 deg. C for 30 min prior to fabrication of the sensor resulted in a 7.5 fold increase in glucose sensitivity. The as-spun CNT fiber based glucose biosensor was shown to be stable for up to 70 days. In addition, gold coating of the electrode connecting end of the CNT fiber resulted in extending the glucose detection limit to 25 μM. To conclude, superior efficiency of CNT fiber for glucose biosensing was demonstrated compared to a traditional Pt-Ir sensor.

  5. Nano-yarn carbon nanotube fiber based enzymatic glucose biosensor

    Science.gov (United States)

    Zhu, Zhigang; Song, Wenhui; Burugapalli, Krishna; Moussy, Francis; Li, Ya-Li; Zhong, Xiao-Hua

    2010-04-01

    A novel brush-like electrode based on carbon nanotube (CNT) nano-yarn fiber has been designed for electrochemical biosensor applications and its efficacy as an enzymatic glucose biosensor demonstrated. The CNT nano-yarn fiber was spun directly from a chemical-vapor-deposition (CVD) gas flow reaction using a mixture of ethanol and acetone as the carbon source and an iron nano-catalyst. The fiber, 28 µm in diameter, was made of bundles of double walled CNTs (DWNTs) concentrically compacted into multiple layers forming a nano-porous network structure. Cyclic voltammetry study revealed a superior electrocatalytic activity for CNT fiber compared to the traditional Pt-Ir coil electrode. The electrode end tip of the CNT fiber was freeze-fractured to obtain a unique brush-like nano-structure resembling a scale-down electrical 'flex', where glucose oxidase (GOx) enzyme was immobilized using glutaraldehyde crosslinking in the presence of bovine serum albumin (BSA). An outer epoxy-polyurethane (EPU) layer was used as semi-permeable membrane. The sensor function was tested against a standard reference electrode. The sensitivities, linear detection range and linearity for detecting glucose for the miniature CNT fiber electrode were better than that reported for a Pt-Ir coil electrode. Thermal annealing of the CNT fiber at 250 °C for 30 min prior to fabrication of the sensor resulted in a 7.5 fold increase in glucose sensitivity. The as-spun CNT fiber based glucose biosensor was shown to be stable for up to 70 days. In addition, gold coating of the electrode connecting end of the CNT fiber resulted in extending the glucose detection limit to 25 µM. To conclude, superior efficiency of CNT fiber for glucose biosensing was demonstrated compared to a traditional Pt-Ir sensor.

  6. Uma perspectiva computacional sobre catálise enzimática A computational perspective on enzymatic catalysis

    Directory of Open Access Journals (Sweden)

    Guilherme M. Arantes

    2008-01-01

    Full Text Available Enzymes are extremely efficient catalysts. Here, part of the mechanisms proposed to explain this catalytic power will be compared to quantitative experimental results and computer simulations. Influence of the enzymatic environment over species along the reaction coordinate will be analysed. Concepts of transition state stabilisation and reactant destabilisation will be confronted. Divided site model and near-attack conformation hypotheses will also be discussed. Molecular interactions such as covalent catalysis, general acid-base catalysis, electrostatics, entropic effects, steric hindrance, quantum and dynamical effects will also be analysed as sources of catalysis. Reaction mechanisms, in particular that catalysed by protein tyrosine phosphatases, illustrate the concepts.

  7. Monitoring the enzymatic conversion of urea to ammonium by conventional or microchip capillary electrophoresis with contactless conductivity detection.

    Science.gov (United States)

    Schuchert-Shi, Aiping; Hauser, Peter C

    2008-05-15

    Capillary electrophoresis with contactless conductivity detection was used to directly quantify the ammonium produced in the enzymatic conversion of urea with urease. This allowed the characterization of the reaction without having to use more elaborate indirect optical methods for quantification. The maximum rate of reaction, V(max), was determined as 5.1 mmol x mL(-1) x min(-1), and the Michaelis-Menten constant, K(m), was determined as 16 mM. Furthermore, the method was successfully applied to the determination of urea in clinical samples of human blood by using a conventional capillary and a microchip device.

  8. cycloaddition reactions

    Indian Academy of Sciences (India)

    Unknown

    Molecular Modeling Group, Organic Chemical Sciences, Indian Institute of Chemical Technology,. Hyderabad ... thus obtained are helpful to model the regioselectivity ... compromise to model Diels–Alder reactions involving ...... acceptance.

  9. Colorimetric method for enzymatic screening assay of ATP using Fe(III)-xylenol orange complex formation.

    Science.gov (United States)

    Ishida, Akihiko; Yamada, Yasuko; Kamidate, Tamio

    2008-11-01

    In hygiene management, recently there has been a significant need for screening methods for microbial contamination by visual observation or with commonly used colorimetric apparatus. The amount of adenosine triphosphate (ATP) can serve as the index of a microorganism. This paper describes the development of a colorimetric method for the assay of ATP, using enzymatic cycling and Fe(III)-xylenol orange (XO) complex formation. The color characteristics of the Fe(III)-XO complexes, which show a distinct color change from yellow to purple, assist the visual observation in screening work. In this method, a trace amount of ATP was converted to pyruvate, which was further amplified exponentially with coupled enzymatic reactions. Eventually, pyruvate was converted to the Fe(III)-XO complexes through pyruvate oxidase reaction and Fe(II) oxidation. As the assay result, yellow or purple color was observed: A yellow color indicates that the ATP concentration is lower than the criterion of the test, and a purple color indicates that the ATP concentration is higher than the criterion. The method was applied to the assay of ATP extracted from Escherichia coli cells added to cow milk.

  10. Production of Fish Hydrolysates Protein From Waste of Fish Carp (Cyprinus Carpio by Enzymatic Hydrolysis

    Directory of Open Access Journals (Sweden)

    Dede Saputra

    2016-03-01

    Full Text Available Fish Protein Hydrolysates (FPH is the mixed products of polypeptide, dipeptides, and amino acid. It can be produced from materials that contained of protein by acid reaction, base reaction or enzymatic hydrolysis. The objectives of this study were to study the production of FPH from fish carp meat at post rigor phase and viscera by enzymatic hydrolysis, to determine the specific activity of papain enzyme, and to determine the solubility of FPH. Capacity of fish hydrolyzing can be identified by analyzing the content of dissolved total nitrogen (NTT compared with nitrogen total ingredient (NTB in order to get the value of total soluble nitrogen/total nitrogen material (NTT/NTB. The hydrolysis processes were carried out in 0,26% (w/v papain, 60 οC for 3 hours. The result showed that the specific activity of papain enzyme was about 3.28 U/mg. Solubility of FPH by comparing NTT/NTB was about 0.29% (fish meat and 0.40% (fish viscera. Proximate test of protein content of fish meat was 18.34 ± 0.04 (g/100 g; while viscera was about 0.95±0.04 (g/100 g. The result indicated that product waste of fish carp had potential as a major of source of FPH.

  11. Chemical interaction of disulfiram with nitrosodimethylamine after in vitro enzymatic activation

    International Nuclear Information System (INIS)

    Tacchi, A.M.; Bertram, B.; Wiessler, M.

    1984-01-01

    The in vitro reaction between disulfiram (DSF) and N-nitroso[ 14 C]dimethylamine [( 14 C]NDMA) was studied. Incubations of DSF with [ 14 C]NDMA were carried out in the presence of rat liver microsomes, control 9000 g (S9) supernatant fraction and phenobarbital-induced S9 fraction. HPLC analysis and liquid scintillation measurement provided evidence for the formation of methyldiethyldithiocarbamate (MeDDTC) as a product of the reaction between diethyldithiocarbamate (DDTC), the main active metabolite of DSF and the 'methyl-cation' released by NDMA after enzymatic activation. The amount of MeDDTC found here was consistent with the rate of oxidation of NDMA to formaldehyde. Scintillation counting confirmed that other radioactive peaks, not due to MeDDTC, were unrelated to the methylation of L-cysteine by [ 14 C]NDMA

  12. Enzymatic detoxification of jojoba meal and effect of the resulting meal on food intake in rats.

    Science.gov (United States)

    Bouali, Abderrahime; Bellirou, Ahmed; Boukhatem, Noureddin; Hamal, Abdellah; Bouammali, Boufelja

    2008-05-10

    When defatted jojoba meal is used as animal food, it causes food-intake reduction and growth retardation. Detoxification procedures by chemical, microbiological, and solvent extraction methods are reported by several authors. Here we report a successful detoxification of jojoba meal using enzymes. We establish reaction conditions that yield new meal which has the same nutritional qualities in proteins as the original meal. The enzymatic reaction gives rise to one major compound to which the structure of an amide is assigned on the basis of IR, 1H and 13C NMR spectra. The effect of the resulting jojoba meal on the food intake in rats is checked. In contrast, the detoxified meal containing the amide derivatives shows no toxicological activity since rats receiving oral administration of the obtained meal show normal growth. Thus, it is expected that this meal could be used as an animal feed ingredient.

  13. Enzymatic Transesterification of Ethyl Ferulate with Fish Oil and Its Optimization by Response Surface Methodology

    DEFF Research Database (Denmark)

    Yang, Zhiyong; Glasius, Marianne; Xu, Xuebing

    2012-01-01

    formation of feruloyl fish oil products as well when appropriate amount of glycerol was present in the reaction. Therefore, the addition of equivalent molar amount of glycerol to EF was decided for the practical optimization of the system. The mutual effects of temperature (40 to 70 oC), reaction time (1......The enzymatic transesterification of ethyl ferulate (EF) with cod liver fish oil was investigated with Novozym 435 as catalyst under solvent-free conditions. The purpose of the study is to evaluate the synthesis system for production of feruloyl fish oil in industry. The modified HPLC method...... to 5 days), enzyme load (2 to 20 %) and substrate amount ratio of fish oil/EF (1 to 5) were thus studied with assistance of response surface methodology (RSM) for the purpose of maximizing the formation towards feruloyl fish oil. The models were well fitted and verified. The optimized conditions were...

  14. Improving the phenotype predictions of a yeast genome-scale metabolic model by incorporating enzymatic constraints

    DEFF Research Database (Denmark)

    Sanchez, Benjamin J.; Zhang, Xi-Cheng; Nilsson, Avlant

    2017-01-01

    , which act as limitations on metabolic fluxes, are not taken into account. Here, we present GECKO, a method that enhances a GEM to account for enzymes as part of reactions, thereby ensuring that each metabolic flux does not exceed its maximum capacity, equal to the product of the enzyme's abundance...... and turnover number. We applied GECKO to a Saccharomyces cerevisiae GEM and demonstrated that the new model could correctly describe phenotypes that the previous model could not, particularly under high enzymatic pressure conditions, such as yeast growing on different carbon sources in excess, coping...... with stress, or overexpressing a specific pathway. GECKO also allows to directly integrate quantitative proteomics data; by doing so, we significantly reduced flux variability of the model, in over 60% of metabolic reactions. Additionally, the model gives insight into the distribution of enzyme usage between...

  15. Laboratory scale production of glucose syrup by the enzymatic ...

    African Journals Online (AJOL)

    Jen

    Laboratory scale production of glucose syrup by the enzymatic ... The industrial processing of starch to glucose, maltose and dextrin involves gelatinization, ... due to non-availability of appropriate technology and industry to harness these into.

  16. [Methods for enzymatic determination of triglycerides in liver homogenates].

    Science.gov (United States)

    Höhn, H; Gartzke, J; Burck, D

    1987-10-01

    An enzymatic method is described for the determination of triacylglycerols in liver homogenate. In contrast to usual methods, higher reliability and selectivity are achieved by omitting the extraction step.

  17. Recent insights in enzymatic synthesis of fructooligosaccharides from inulin.

    Science.gov (United States)

    Singh, Ram Sarup; Singh, Rupinder Pal; Kennedy, John F

    2016-04-01

    In the past few years, people are paying more attention to their dietary habits, and functional foods are playing a key role in maintaining the health of man. Prebiotics are considered as a main component of the functional foods which are usually composed of short chains of carbohydrates. Fructooligosaccharides (FOSs) are considered as one of the main group of prebiotics which have recognisable bifidogenic properties. FOSs are obtained either by extraction from various plant materials or by enzymatic synthesis from different substrates. Enzymatically, these can be obtained either from sucrose using fructosyltransferase or from inulin by endoinulinase. Inulin is a potent substrate for the enzymatic production of FOSs. This review article will provide an overview on the inulin as potent substrate, microbial sources of endoinulinases, enzymatic synthesis of FOSs from inulin, commercial status of FOSs, and their future perspectives. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Enzymatic biosensors based on the use of metal oxide nanoparticles

    International Nuclear Information System (INIS)

    Shi, Xinhao; Gu, Wei; Li, Bingyu; Chen, Ningning; Zhao, Kai; Xian, Yuezhong

    2014-01-01

    Over the past decades, various techniques have been developed to obtain materials at a nanoscale level to design biosensors with high sensitivity, selectivity and efficiency. Metal oxide nanoparticles (MONPs) are of particular interests and have received much attention because of their unique physical, chemical and catalytic properties. This review summarizes the progress made in enzymatic biosensors based on the use of MONPs. Synthetic methods, strategies for immobilization, and the functions of MONPs in enzymatic biosensing systems are reviewed and discussed. The article is subdivided into sections on enzymatic biosensors based on (a) zinc oxide nanoparticles, (b) titanium oxide nanoparticles, (c) iron oxide nanoparticles, and (d) other metal oxide nanoparticles. While substantial advances have been made in MONPs-based enzymatic biosensors, their applications to real samples still lie ahead because issues such as reproducibility and sensor stability have to be solved. (author)

  19. Modelling of the enzymatic kinetically controlled synthesis of cephalexin

    NARCIS (Netherlands)

    Schroën, C.G.P.H.; Fretz, C.B.; Bruin, de V.H.; Berendsen, W.; Moody, H.M.; Roos, E.C.; Roon, van J.L.; Kroon, P.J.; Strubel, M.; Janssen, A.E.M.; Tramper, J.

    2002-01-01

    In this study the influence of diffusion limitation on enzymatic kinetically controlled cephalexin synthesis from phenylglycine amide and 7-aminodeacetoxycephalosporinic acid (7-ADCA) was investigated systematically. It was found that if diffusion limitation occurred, both the synthesis/hydrolysis

  20. Factors of enzymatic biodiesel production from sludge palm oil (SPO ...

    African Journals Online (AJOL)

    ika

    2013-07-31

    Jul 31, 2013 ... Biodiesel is a non-toxic, renewable and environmental friendly fuel. This study ... of biodiesel from sludge palm oil (SPO), a low-cost waste oil via enzymatic catalysis. ... Increasing energy crisis and environmental concerns by.

  1. Effects of Surfactants on the Rate of Chemical Reactions

    Directory of Open Access Journals (Sweden)

    B. Samiey

    2014-01-01

    Full Text Available Surfactants are self-assembled compounds that depend on their structure and electric charge can interact as monomer or micelle with other compounds (substrates. These interactions which may catalyze or inhibit the reaction rates are studied with pseudophase, cooperativity, and stoichiometric (classical models. In this review, we discuss applying these models to study surfactant-substrate interactions and their effects on Diels-Alder, redox, photochemical, decomposition, enzymatic, isomerization, ligand exchange, radical, and nucleophilic reactions.

  2. Statistical properties of multistep enzyme-mediated reactions

    OpenAIRE

    de Ronde, Wiet H.; Daniels, Bryan C.; Mugler, Andrew; Sinitsyn, Nikolai A.; Nemenman, Ilya

    2008-01-01

    Enzyme-mediated reactions may proceed through multiple intermediate conformational states before creating a final product molecule, and one often wishes to identify such intermediate structures from observations of the product creation. In this paper, we address this problem by solving the chemical master equations for various enzymatic reactions. We devise a perturbation theory analogous to that used in quantum mechanics that allows us to determine the first () and the second (variance) cumu...

  3. DOTA-Functionalized Polylysine: A High Number of DOTA Chelates Positively Influences the Biodistribution of Enzymatic Conjugated Anti-Tumor Antibody chCE7agl.

    OpenAIRE

    Grünberg Jürgen; Jeger Simone; Sarko Dikran; Dennler Patrick; Zimmermann Kurt; Mier Walter; Schibli Roger

    2013-01-01

    Site-specific enzymatic reactions with microbial transglutaminase (mTGase) lead to a homogenous species of immunoconjugates with a defined ligand/antibody ratio. In the present study, we have investigated the influence of different numbers of 1,4,7,10-tetraazacyclododecane-N-N'-N''-N'''-tetraacetic acid (DOTA) chelats coupled to a decalysine backbone on the in vivo behavior of the chimeric monoclonal anti-L1CAM antibody chCE7agl. The enzymatic conjugation of (DOTA)1-decalysine, (DOTA)3-decaly...

  4. Inhibition of tyrosinase-mediated enzymatic browning by sulfite and natural alternatives

    NARCIS (Netherlands)

    Kuijpers, T.F.M.; Vincken, J.P.

    2013-01-01

    Although sulfite is widely used to counteract enzymatic browning, its mechanism has remained largely unknown. We describe a double inhibitory mechanism of sulfite on enzymatic browning, affecting both the enzymatic oxidation of phenols into o‑quinones, as well as the non‑enzymatic

  5. Diffuse control of gas turbines in power stations of combined cycle; Contral difuso de turbinas de gas en centrales de ciclo combinado

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez P, Marino; Garduno R, Raul; De Lara J, Salvadror; Castelo C, Luis [Instituto de Investigaciones Electricas, Cuernavaca, Morelos (Mexico)

    2001-07-01

    In this article the application of the technology of the fuzzy logic to the control of gas turbines is presented in order to evaluate it in one of the most difficult processes and with stricter control requirements that exist in the electrical generation industry. For being important for the generation electrical sector, given their use in Comision Federal de Electricidad (CFE), the first selected prototype was the gas turbines model W501 of Westinghouse, installed in the of combined cycle power stations of Dos Bocas, Veracruz, Gomez Palacio, Durango and Tula, Hidalgo, Mexico. The second selected prototype was the one of the turbo gas units type 5001 (that applies to the GE 5001 models and Westinghouse of series 191 and 251). Based on the analysis of the performance of the system of conventional control previously made, the controllers of speed and generation of electrical power were selected to be replaced by diffuse controllers. [Spanish] En este articulo se presenta la aplicacion de la tecnologia de la logica difusa al control de turbinas de gas con el proposito de evaluarla en uno de los procesos mas dificiles y con requerimientos mas estrictos de control que existen en la industria de generacion electrica. Por ser importantes para el sector electrico de generacion, dada su utilizacion en Comision Federal de Electricidad (CFE), el primer prototipo seleccionado fueron las turbinas de gas modelo W501 de Westinghouse, instaladas en la central de ciclo combinado de Dos Bocas, Veracruz, Gomez Palacio, Durango y Tula, Hidalgo, Mexico. El segundo prototipo seleccionado fue el de unidades turbogas tipo 5001 (que aplica a los modelos GE 5001 y Westinghouse de la serie 191 y 251). Basados en el analisis del desempeno del sistema de control convencional realizado previamente, los controladores de velocidad y de generacion de potencia electrica fueron seleccionados para ser sustituidos por controladores difusos.

  6. Direct Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Austern, N. [University of Pittsburgh, Pittsburgh, PA (United States)

    1963-01-15

    In order to give a unified presentation of one point of view, these lectures are devoted only to a detailed development of the standard theories of direct reactions, starting from basic principles. Discussion is given of the present status of the theories, of the techniques used for practical calculation, and of possible future developments. The direct interaction (DI) aspects of a reaction are those which involve only a few of the many degrees of freedom of a nucleus. In fact the minimum number of degrees of freedom which must be involved in a reaction are those required to describe the initial and final channels, and DI studies typically consider these degrees of freedom and no others. Because of this simplicity DI theories may be worked out in painstaking detail. DI processes concern only part of the wave function for a problem. The other part involves complicated excitations of many degrees of freedom, and gives the compound nucleus (CN) effects. While it is extremely interesting to learn how to separate DI and CN effects in an orderly manner, if they are both present in a reaction, no suitable method has yet been found. Instead, current work stresses the kinds of reactions and the kinds of final states in which DI effects dominate and in which CN effects may almost be forgotten. The DI cross-sections which are studied are often extremely large, comparable to elastic scattering cross-sections. (author)

  7. Kinetics based reaction optimization of enzyme catalysed reduction of formaldehyde to methanol with synchronous cofactor regeneration

    DEFF Research Database (Denmark)

    Marpani, Fauziah Binti; Sárossy, Zsuzsa; Pinelo, Manuel

    2017-01-01

    regeneration of the reducing equivalents during reaction is required. Herein, we report the optimization of the enzymatic conversion of formaldehyde (CHOH) to CH3 OH by alcohol dehydrogenase, the final step of the enzymatic redox reaction of CO2 to CH3 OH, with kinetically synchronous enzymatic cofactor...... regeneration using either glucose dehydrogenase (System I) or xylose dehydrogenase (System II). A mathematical model of the enzyme kinetics was employed to identify the best reaction set-up for attaining optimal cofactor recycling rate and enzyme utilization efficiency. Targeted process optimization...... experiments were conducted to verify the kinetically modelled results. Repetitive reaction cycles were shown to enhance the yield of CH3 OH, increase the total turnover number (TTN) and the biocatalytic productivity rate (BPR) value for both system I and II whilst minimizing the exposure of the enzymes...

  8. Bioelectrocatalytic NAD+/NADH inter-conversion: transformation of an enzymatic fuel cell into an enzymatic redox flow battery.

    Science.gov (United States)

    Quah, Timothy; Milton, Ross D; Abdellaoui, Sofiene; Minteer, Shelley D

    2017-07-25

    Diaphorase and a benzylpropylviologen redox polymer were combined to create a bioelectrode that can both oxidize NADH and reduce NAD + . We demonstrate how bioelectrocatalytic NAD + /NADH inter-conversion can transform a glucose/O 2 enzymatic fuel cell (EFC) with an open circuit potential (OCP) of 1.1 V into an enzymatic redox flow battery (ERFB), which can be rapidly recharged by operation as an EFC.

  9. Enzymatic production of ceramide from sphingomyelin

    DEFF Research Database (Denmark)

    Zhang, Long; Hellgren, Lars; Xu, Xuebing

    2006-01-01

    -saturated organic solvent) system. Among the screened phospholipase C, the Clostridium petfringens enzyme had the highest sphingomyetin conversion rate, with very small temperature dependence. Addition of ethanol to the system markedly enhanced the rate of ceramide formation, and a mixture of ethyl acetate: hexane...... (50:50) was the best organic solvent tested. Other factors such as (NH4)(2)SO4, MCI and CaCl, were also tested but excluded for further consideration. On the basis of the initial experiments, the reaction system was optimized using response surface methodology including five factors (enzyme amount...... systern evaluation and optimization, with the optimal conditions at 75 min reaction time, 3 U ml(-1) enzyme amount, 6% water amount, 1.8% ethanol arnount and 46% hexane in ethylacetate. (c) 2005 Elsevier B.V. All rights reserved....

  10. Identification of Maillard reaction induced chemical modifications on Ara h 1

    Science.gov (United States)

    The Maillard reaction is a non-enzymatic glycation reaction between proteins and reducing sugars that can modify nut allergens during thermal processing. These modifications can alter the structural and immunological properties of these allergens, and may result in increased IgE binding. Here, we ...

  11. Enzymatic oxidation of mercury vapor by erythrocytes

    Energy Technology Data Exchange (ETDEWEB)

    Halbach, S; Clarkson, T W

    1978-01-01

    The formation of glutathione radicals, the evolution of nascent oxygen or the peroxidatic reaction with catalase complex I are considered as possible mechanisms for the oxidation of mercury vapor by red blood cells. To select among these, the uptake of atomic mercury by erythrocytes from different species was studied and related to their various activities of catalase (hydrogen-peroxide:hydrogen-peroxide oxidoreductase, EC 1.11.1.6) and glutathione peroxidase (glutathione:hydrogen-peroxide oxidoreductase, EC 1.11.1.9). A slow and continuouus infusion of diluted H/sub 2/O/sub 2/ was used to maintain steady concentrations of complex I. 1% red cell suspensions were found most suitable showing high rates of Hg uptake and yielding still enough cells for subsequent determinations. The results indicate that the oxidation of mercury depends upon the H/sub 2/O/sub 2/-generation rate and upon the specific acticity of red-cell catalase. The oxidation occurred in a range of the catalase-H/sub 2/O/sub 2/ reaction where the evolution of oxygen could be excluded. Compounds reacting with complex I were shown to be effective inhibitors of the mercury uptake. GSH-peroxidase did not participate in the oxidation but rather, was found to inhibit it by competing with catalase for hydrogen peroxide. These findings support the view that elemental mercury is oxidized in erythrocytes by a peroxidatic reaction with complex I only.

  12. Reaction mechanisms

    International Nuclear Information System (INIS)

    Nguyen Trong Anh

    1988-01-01

    The 1988 progress report of the Reaction Mechanisms laboratory (Polytechnic School, France), is presented. The research topics are: the valence bond methods, the radical chemistry, the modelling of the transition states by applying geometric constraints, the long range interactions (ion - molecule) in gaseous phase, the reaction sites in gaseous phase and the mass spectroscopy applications. The points of convergence between the investigations of the mass spectroscopy and the theoretical chemistry teams, as well as the purposes guiding the research programs, are discussed. The published papers, the conferences, the congress communications and the thesis, are also reported [fr

  13. The effect of mass transport on the graphite/CO2 reaction

    International Nuclear Information System (INIS)

    Stephen, W.J.

    1984-11-01

    The Graphite/CO 2 reaction is strongly inhibited by the reaction product CO and therefore any model for the influence of mass transport on reaction rate should consider this. The problem of internal mass transport alone has been considered in previous notes. This note extends the models to include external mass transport. Results are compared with simple first order reaction with no volume change. The calculations demonstrate that, for strong CO inhibition, external mass transport limits reaction at a much lower rate than for first order kinetics and that the usual concept of three reaction zones corresponding to chemical control, in-pore diffusion control and boundary layer control can be unrealistically idealised. (U.K.)

  14. Allergic reactions

    Science.gov (United States)

    ... that don't bother most people (such as venom from bee stings and certain foods, medicines, and pollens) can ... person. If the allergic reaction is from a bee sting, scrape the ... more venom. If the person has emergency allergy medicine on ...

  15. The influence of Fe2+ on growth and development of cells enzymatically isolated from Porphyra yezoensis blades

    Science.gov (United States)

    Songdong, Shen; Jixun, Dai

    2005-03-01

    Fe2+ acted as an accessorial factor for many cellular enzymatic reactions is very important for seaweed growth and development, but the Fe2+ requirement in nori had not been seen, Porphyra yezoensis cells were separated enzymatically and cultured in a series of sterilized seawater media containing various concentrations of Fe2+. The growth development and cell were investigated in this work. Through this experiment, two biologically-meant concentration scales were found, one is low concentrations, 12.1-102.1 μg/L, 10-100 times than that in seawater, favoring the development of isolated cells of Porphyra and the other was high concentrations, more than 10mg/L inhibiting the cell growth, leading to the deformity and shrinkage of the cells. At the concentration of 50 mg/L, the cells stopped growing and died eventually.

  16. DNA-Based Sensor for Real-Time Measurement of the Enzymatic Activity of Human Topoisomerase I

    DEFF Research Database (Denmark)

    Marcussen, Lærke Bay; Jepsen, Morten Leth; Kristoffersen, Emil Laust

    2013-01-01

    Sensors capable of quantitative real-time measurements may present the easiest and most accurate way to study enzyme activities. Here we present a novel DNA-based sensor for specific and quantitative real-time measurement of the enzymatic activity of the essential human enzyme, topoisomerase I....... The basic design of the sensor relies on two DNA strands that hybridize to form a hairpin structure with a fluorophore-quencher pair. The quencher moiety is released from the sensor upon reaction with human topoisomerase I thus enabling real-time optical measurement of enzymatic activity. The sensor....... The cytotoxic effect of camptothecins correlates directly with the intracellular topoisomerase I activity. We therefore envision that the presented sensor may find use for the prediction of cellular drug response. Moreover, inhibition of topoisomerase I by camptothecin is readily detectable using the presented...

  17. Potentialities of a Membrane Reactor with Laccase Grafted Membranes for the Enzymatic Degradation of Phenolic Compounds in Water

    Directory of Open Access Journals (Sweden)

    Vorleak Chea

    2014-10-01

    Full Text Available This paper describes the degradation of phenolic compounds by laccases from Trametes versicolor in an enzymatic membrane reactor (EMR. The enzymatic membranes were prepared by grafting laccase on a gelatine layer previously deposited onto α-alumina tubular membranes. The 2,6-dimethoxyphenol (DMP was selected  from among the three different phenolic compounds tested (guaiacol, 4-chlorophenol and DMP to study the performance of the EMR in dead end configuration. At the lowest feed substrate concentration tested (100 mg·L−1, consumption increased with flux (up to 7.9 × 103 mg·h−1·m−2 at 128 L·h−1·m−2, whereas at the highest substrate concentration (500 mg·L−1, it was shown that the reaction was limited by the oxygen content.

  18. Role of enzymatic and non enzymatic antioxidant in ameliorating salinity induced damage in nostoc muscorum

    International Nuclear Information System (INIS)

    Hend, A.; Abeer, A.; Allah, A.

    2015-01-01

    Presence of high salt concentration in the growth medium adversely affected the plant growth and productivity by altering its metabolic activities. Experiments were conducted on cyanobacteriaum Nostoc muscorum grown in nitrogen free medium supplemented with 250 mM NaCl to evaluate the salt stress induced changes in growth, antioxidants and lipid composition. Salt stress significantly reduced the growth and physio-biochemical attributes. Salt stress increased malonaldehyde content thereby causing alterations in the lipid fraction. Significant reduction in polyunsaturated fatty acids including phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), phosphatidylinositol (PI) and phosphatidylserine (PS) was observed. Where as diacylglycerol, sterol ester and non-esterified fatty acids were increased. Activities of antioxidant enzymes and contents of non-enzymatic antioxidants including glutathione enhanced due to salt stress. An increase in accumulation of proline was also observed. Hence increased activity of antioxidants and altered fatty acid composition was observed in salt stressed Nostoc muscorum. (author)

  19. ENZYMATIC AND NON-ENZYMATIC ANTIOXIDANT DEFENSE WITH ALZHEIMER DISEASE1

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    A. Vaisi-Raygani

    2007-07-01

    Full Text Available The etiopathogenesis of Alzheimer's disease (AD is still unclear.  However, long-term oxidative stress is believed to be one of the major contributing factors in progression of neuronal degeneration and decline of cognitive function in AD. In order to assess the presence of oxidative stress in AD, we examined the enzymatic activities of the erythrocyte Cu-Zn superoxide dismutase (Cu-Zn SOD, glutathione peroxidase (GSH-Px, catalase (CAT, and plasma level of total antioxidant status (TAS in AD and control groups (age and sex-matched. The results showed that the Cu-Zn SOD activity was significantly higher and the level of GSH-Px and TAS activities were significantly lower in AD subjects than that in the control group (2111 ± 324 U/grHb, 43.7 ± 11.6 U/grHb, and 1.17 ± 0.23 mmol/l compared with 1371 ± 211 U/grHb; t= -2.17, P = 0.036, 56.3 ± 9.5 U/grHb; t=3.8, P = 0.014, and 1.54±0.2 mmol/l; t=11.18, P < 0.001, respectively.  While, the erythrocyte CAT activity was lower in AD subjects compared to the control group, the difference was not statistically significant (t = 1.3, P = 0.15. These findings support the idea that the oxidative stress plays an important role in the pathogenesis underlying AD neurodegeneration. In addition, the enzymatic activity of the erythrocyte Cu-Zn SOD and GSH-Px and the plasma level of TAS can be used as a measure of the oxidative stress and a marker for pathological changes in the brain of patients with AD. 

  20. ASSOCIATION BETWEEN ENZYMATIC AND NON-ENZYMATIC ANTIOXIDANT DEFENSE WITH ALZHEIMER DISEASE

    Directory of Open Access Journals (Sweden)

    A. Vaisi-Raygani

    2008-04-01

    Full Text Available The etiopathogenesis of dementia in Alzheimer's disease (AD is still unclear. However, long-term oxidative stress is believed to be one of the major contributing factors in progression of neuronal degeneration and decline of cognitive function in AD. In order to assess the presence of oxidative stress in AD, we examined the enzymatic activities of the erythrocyte Cu-Zn superoxide dismutase (Cu-Zn SOD, glutathione peroxidase (GSH-Px, catalase (CAT, and plasma level of total antioxidant status (TAS in AD and control groups (age and sex-matched. The results showed that the Cu-Zn SOD activity was significantly higher and the level of GSH-Px and TAS activities were significantly lower in AD subjects than that in the control group (2111±324 U/grHb, 43.7±11.6 U/grHb, and 1.17 ±0.23 mmol/L compared with 1371±211 U/gHb; t= -2.17, p=0.036, 56.3±9.5 U/gHb; t=3.8, p=0.014, and 1.54±0.2 mmol/L; t=11.18, P<0.001, respectively. While, the erythrocyte CAT activity was lower in AD subjects compared to the control group, the difference was not statistically significant (t=1.3, P=0.15. These findings support the idea that the oxidative stress plays an important role in the pathogenesis underlying AD neurodegeneration. In addition, the enzymatic activity of the erythrocyte Cu-Zn SOD and GSH-Px and the plasma level of TAS can be used as a measure of the oxidative stress and a marker for pathological changes in the brain of patients with AD.

  1. Fish protein hydrolysate production from sardine solid waste by crude pepsin enzymatic hydrolysis in a bioreactor coupled to an ultrafiltration unit

    International Nuclear Information System (INIS)

    Benhabiles, M.S.; Abdi, N.; Drouiche, N.; Lounici, H.; Pauss, A.; Goosen, M.F.A.; Mameri, N.

    2012-01-01

    The aims of the study were to optimize the production a fish protein hydrolysate (FPH) by enzymatic hydrolysis of sardine solid waste using crude pepsin, and to scale up the process in a bioreactor coupled to an ultrafiltration unit for product recovery. Results showed that the crude pepsin prepared by autolysis of the mucous membranes of a sheep stomach at optimal conditions (i. e. pH = 1.5–2 and incubation time of 6 h) could be satisfactory used for the enzymatic hydrolysis of fish solid waste. The optimal conditions for enzymatic reaction were: temperature 48 °C, and pH 1.5. The scale up of the enzymatic hydrolysis and the coupling of the reactor an ultrafiltration unit to concentrate the hydrolysate gave good results with a rejection coefficient for the protein hydrolysate product in the range of 90%. The volumetric concentration factor was 2.5, with a permeate flux of 200 L m −2 bar −1 . However, the results also suggest that the ultrafiltration product concentration process may be operating beyond the critical flux at which point irreversible membrane fouling occurs. - Highlights: ► Evaluating to produce a (FPH) by enzymatic hydrolysis of sardine solid wastes was achieved. ► Investigation of key parameters for optimal conditions for enzymatic hydrolysis have been studied. ► Valorization of sardine waste was realized by enzymatic hydrolysis process. ► Performances of this enzyme gave comparable results to those obtained with commercial pepsin. ► The nutritional quality of the FPH produced appears to be satisfactory.

  2. Fish protein hydrolysate production from sardine solid waste by crude pepsin enzymatic hydrolysis in a bioreactor coupled to an ultrafiltration unit

    Energy Technology Data Exchange (ETDEWEB)

    Benhabiles, M.S.; Abdi, N. [National Polytechnic school of Algiers, B.P. 182-16200, El Harrach, Algiers (Algeria); Drouiche, N., E-mail: nadjibdrouiche@yahoo.fr [National Polytechnic school of Algiers, B.P. 182-16200, El Harrach, Algiers (Algeria); Silicon Technology Development Unit (UDTS) 2, Bd Frantz Fanon BP140, Alger-7 Merveilles, 16000 (Algeria); Lounici, H. [National Polytechnic school of Algiers, B.P. 182-16200, El Harrach, Algiers (Algeria); Pauss, A. [University of Technology of Compiegne, Departement Genie chimique,B.P. 20.509, 60205 Compiegne cedex (France); Goosen, M.F.A. [Alfaisal University, Riyadh (Saudi Arabia); Mameri, N. [University of Technology of Compiegne, Departement Genie chimique,B.P. 20.509, 60205 Compiegne cedex (France)

    2012-05-01

    The aims of the study were to optimize the production a fish protein hydrolysate (FPH) by enzymatic hydrolysis of sardine solid waste using crude pepsin, and to scale up the process in a bioreactor coupled to an ultrafiltration unit for product recovery. Results showed that the crude pepsin prepared by autolysis of the mucous membranes of a sheep stomach at optimal conditions (i. e. pH = 1.5-2 and incubation time of 6 h) could be satisfactory used for the enzymatic hydrolysis of fish solid waste. The optimal conditions for enzymatic reaction were: temperature 48 Degree-Sign C, and pH 1.5. The scale up of the enzymatic hydrolysis and the coupling of the reactor an ultrafiltration unit to concentrate the hydrolysate gave good results with a rejection coefficient for the protein hydrolysate product in the range of 90%. The volumetric concentration factor was 2.5, with a permeate flux of 200 L m{sup -2} bar{sup -1}. However, the results also suggest that the ultrafiltration product concentration process may be operating beyond the critical flux at which point irreversible membrane fouling occurs. - Highlights: Black-Right-Pointing-Pointer Evaluating to produce a (FPH) by enzymatic hydrolysis of sardine solid wastes was achieved. Black-Right-Pointing-Pointer Investigation of key parameters for optimal conditions for enzymatic hydrolysis have been studied. Black-Right-Pointing-Pointer Valorization of sardine waste was realized by enzymatic hydrolysis process. Black-Right-Pointing-Pointer Performances of this enzyme gave comparable results to those obtained with commercial pepsin. Black-Right-Pointing-Pointer The nutritional quality of the FPH produced appears to be satisfactory.

  3. Enzymatic Degradation of Poly(ethylene 2,5-furanoate Powders and Amorphous Films

    Directory of Open Access Journals (Sweden)

    Simone Weinberger

    2017-10-01

    Full Text Available Poly(ethylene 2,5-furanoate (PEF is arousing great interest as a biobased alternative to plastics like poly(ethylene terephthalate (PET due to its wide range of potential applications, such as food and beverage packaging, clothing, and in the car industry. In the present study, the hydrolysis of PEF powders of different molecular masses (Mn = 55, Mw = 104 kg/mol and Mn = 18, Mw = 29 kg/mol and various particle sizes (180 < d and 180 < d < 425 µm using cutinase 1 from Thermobifida cellulosilytica (Thc_cut1 was studied. Thereby, the effects of molecular mass, particle size and crystallinity on enzymatic hydrolysis were investigated. The results show that particles with lower molecular mass are hydrolyzed faster than those with higher masses, and that the higher the molecular mass, the lower the influence of the particle size on the hydrolysis. Furthermore, cutinases from Humicola insolens (HiC and Thc_cut1 were compared with regard to their hydrolytic activity on amorphous PEF films (measured as release of 2,5-furandicarboxylic acid (FDCA and weight loss in different reaction media (1 M KPO pH 8, 0.1 M Tris-HCl pH 7 and at different temperatures (50 °C and 65 °C. A 100% hydrolysis of the PEF films was achieved after only 72 h of incubation with a HiC in 1 M KPO pH 8 at 65 °C. Moreover, the hydrolysis reaction was monitored by LC/TOF-MS analysis of the released reaction products and by Scanning Electron Microscopy (SEM examination of the polymer surfaces. Enzymatic hydrolysis of PEF with Thc_cut1 and HiC has potential for use in surface functionalization and recycling purposes.

  4. ENZYMATIC KINETIC STUDY HYDROLASE FROM CITRUS

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    Israel Hernández

    2015-09-01

    Full Text Available In this paper the degrading activity of enzymes derived from orange peels (Citrus x sinensis, grapefruit (Citrus paradise and pineapple (Ananas comosus on the organic matter in wastewater is evaluated. This activity is measured indirectly by quantifying the biochemical oxygen demand (COD before and after degradation process based on a period of time using the HACH DR / 2010, and then the kinetic study was performed by the differential method and integral with the experimental data, obtaining a reaction order of 1 to pectinase (orange, and order 2 for bromelain (pineapple.

  5. Effect of high hydrostatic pressure on the enzymatic hydrolysis of bovine serum albumin.

    Science.gov (United States)

    De Maria, Serena; Ferrari, Giovanna; Maresca, Paola

    2017-08-01

    The extent of enzymatic proteolysis mainly depends on accessibility of the peptide bonds, which stabilize the protein structure. The high hydrostatic pressure (HHP) process is able to induce, at certain operating conditions, protein displacement, thus suggesting that this technology can be used to modify protein resistance to the enzymatic attack. This work aims at investigating the mechanism of enzymatic hydrolysis assisted by HHP performed under different processing conditions (pressure level, treatment time). Bovine serum albumin was selected for the experiments, solubilized in sodium phosphate buffer (25 mg mL -1 , pH 7.5) with α-chymotrypsin or trypsin (E/S ratio = 1/10) and HPP treatment (100-500 MPa, 15-25 min). HHP treatment enhanced the extent of the hydrolysis reaction of globular proteins, being more effective than conventional hydrolysis. At HHP treatment conditions maximizing the protein unfolding, the hydrolysis degree of proteins was increased as a consequence of the increased exposure of peptide bonds to the attack of proteolytic enzymes. The maximum hydrolysis degree (10% and 7% respectively for the samples hydrolyzed with α-chymotrypsin and trypsin) was observed for the samples processed at 400 MPa for 25 min. At pressure levels higher than 400 MPa the formation of aggregates was likely to occur; thus the degree of hydrolysis decreased. Protein unfolding represents the key factor controlling the efficiency of HHP-assisted hydrolysis treatments. The peptide produced under high pressure showed lower dimensions and a different structure with respect to those of the hydrolysates obtained when the hydrolysis was carried out at atmospheric pressure, thus opening new frontiers of application in food science and nutrition. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  6. Enzymatic Phorbol Esters Degradation using the Germinated Jatropha Curcas Seed Lipase as Biocatalyst: Optimization Process Conditions by Response Surface Methodology

    Directory of Open Access Journals (Sweden)

    Avita Kusuma Wardhani

    2016-10-01

    Full Text Available Utilization of Jatropha curcas seed cake is limited by the presence of phorbol esters (PE, which are the main toxic compound and heat stable. The objective of this research was to optimize the reaction conditions of the enzymatic PE degradation of the defatted Jatropha curcas seed cake (DJSC using the acetone-dried lipase from the germinated Jatropha curcas seeds as a biocatalyst. Response Surface Methodology (RSM using three-factors-three-levels Box-Behnken design was used to evaluate the effects of the reaction time, the ratio of buffer volume to DJSC, and the ratio of enzyme to DJSC on PE degradation. The results showed that the optimum conditions of PE degradation were 29.33 h, 51.11 : 6 (mL/g, and 30.10 : 5 (U/g cake for the reaction time, the ratio of buffer volume to DJSC, and the ratio of enzyme to DJSC, respectively. The predicted degradation of PE was 98.96% and not significantly different with the validated data of PE degradation. PE content was 0.035 mg/g, in which it was lower than PE in non-toxic Jatropha seeds. The results indicated that enzymatic degradation of PE might be a promising method for degradation of PE.  Copyright © 2016 BCREC GROUP. All rights reserved Received: 22nd December 2015; Revised: 1st April 2016; Accepted: 14th April 2016 How to Cite: Wardhani, A.K., Hidayat, C., Hastuti, P. (2016. Enzymatic Phorbol Esters Degradation using the Germinated Jatropha Curcas Seed Lipase as Biocatalyst: Optimization Process Conditions by Response Surface Methodology. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (3: 346-353 (doi:10.9767/bcrec.11.3.574.346-353 Permalink/DOI: http://doi.org/10.9767/bcrec.11.3.574.346-353

  7. ENZYMATIC PRODUCTION OF ETHYL OLEATE ESTER USING A LIPASE FROM CANDIDA ANTARCTICA B

    Directory of Open Access Journals (Sweden)

    N. Sampaio Neta

    2012-05-01

    Full Text Available Lipases are biocatalysts of great importance in different areas, being able to catalyze reactions in aqueous or organic media. Furthermore, these enzymes are capable of using several substrates being stable in a wide range of pH and temperatures. Lipases promote the esterification between fatty acids and ethanol producing oleate esters. The aim of this work is to produce ethyl oleate ester by enzymatic esterification of oleic acid with ethanol. A lipase from Candida antarctica type B was used at a temperature of 55 °C. The reaction was conducted using oleic acid, sodium sulfate anhydrous, lipase and ethanol, with a ratio of oleic acid (0.03 mol or 10 ml, lipase (0.1 mol or 0.01 g, sodium sulfate anhydrous (5 g and ethanol 99 % (100 ml. Several reaction times were studied, namely 48, 72, 96 and 120 hours. Nuclear Magnetic Resonance (1H and 13C and Infrared spectra confirmed the production of ethyl oleate ester for the studied conditions. The highest ethyl oleate production yield was obtained for 96 hours reaction time. Ethyl oleate esters have been reported to possess interesting applications in several industrial fields, such as food, aromatics, cosmetics, detergents, flavors and pharmaceuticals.

  8. Enzymatic synthesis of vitamin B6 precursor

    Directory of Open Access Journals (Sweden)

    Prlainović Nevena Ž.

    2013-01-01

    Full Text Available 3-Cyano-4-ethoxymethyl-6-methyl-2-pyridone is an important precursor in the synthesis of vitamin B6, obtained in the addition reaction between 2-cyanoacetamide and 1-ethoxy-2,4-pentanedione catalyzed by lipase from Candida rugosa (triacylglycerol ester hydrolases, EC 3.1.1.3. This work shows new experimental data and mathematical modeling of lipase catalyzed synthesis of 3-cyano-4-ethoxymethyl-6-methyl-2-pyridone, starting from 1-ethoxy-2,4-pentanedione and 2-cyanoacetamide. Kinetic measurements were done at 50 oC with enzyme concentration of 1.2 % w/v. Experimental results were fitted with two kinetic models: the ordered bi-ter and ping-pong bi-ter model, and the initial rates of the reaction were found to correlate best with a ping-pong bi-ter mechanism with inhibition by 2-cyanoacetamide. Obtained specificity constants indicated that lipase from C. rugosa had higher affinity towards 1-ethoxy-2,4-pentanedione and less bulky substrates. [Projekat Ministarstva nauke Republike Srbije, br. 172013, br. III 46010 and br. 172049

  9. Effects of process parameters of various pretreatments on enzymatic hydrolysability of Ceiba pentandra (L.) Gaertn. (Kapok) fibre: A response surface methodology study

    International Nuclear Information System (INIS)

    Tye, Ying Ying; Lee, Keat Teong; Wan Abdullah, Wan Nadiah; Leh, Cheu Peng

    2015-01-01

    Kapok fibre is a promising raw material to produce sugar by enzymatic hydrolysis. In this work, effects of water, acid and alkaline pretreatments on the enzymatic sugar yield were studied through response surface methodology (RSM) and supported by the analysis of chemical compositions and physical structure of the fibre. For water pretreatment, reaction temperature and time were the independent variables while chemical concentration was also used as the third independent variable for acid and alkaline pretreatments. For all pretreatments, the enzymatic hydrolysis conditions were kept constant. The structure of pretreated fibre was also examined using scanning electron microscope (SEM). Results showed that water and acid pretreatments effectively dissolved hemicellulose of the fibre with the latter unveiled better results. The alkaline pretreatment resulted in the highest total glucose yield (g/kg of untreated fibre) as compared to water and acid pretreatments. SEM analysis illustrated that water and acid pretreatments led severe destruction of fibre structure; however, both of these pretreatments exhibited lower enhancement of enzymatic hydrolysability of kapok fibre as compared to that observed in alkaline pretreatment. - Highlights: • Effect of pretreatments on sugar yield was studied by response surface methodology. • Glucose yield was highly related to the chemical compositions of pretreated fibers. • Pretreatments altered the physical structure of kapok fibers. • Enzymatic hydrolysability of fibre was improved the most by alkaline treatment. • Over 94% cellulose of the pretreated fibres was converted to glucose

  10. State of the art and prospective of lipase-catalyzed transesterification reaction for biodiesel production

    International Nuclear Information System (INIS)

    Amini, Zeynab; Ilham, Zul; Ong, Hwai Chyuan; Mazaheri, Hoora; Chen, Wei-Hsin

    2017-01-01

    Highlights: • Enzymatic transesterification process is less energy intensive and robust. • Nano-materials are promising immobilization supports for lipase. • Packed-bed reactors are appropriate for scale-up use. • Potential recombinant, whole cell and recombinant whole cell lipases were enlisted. • Genetic engineering is a promising prospect in biodiesel area. - Abstract: The world demand for fuel as energy sources have arisen the need for generating alternatives such as biofuel. Biodiesel is a renewable fuel used particularly in diesel engines. Currently, biodiesel is mainly produced through transesterification reactions catalyzed by chemical catalysts, which produces higher fatty acid alkyl esters in shorter reaction time. Although extensive investigations on enzymatic transesterification by downstream processing were carried out, enzymatic transesterification has yet to be used in scale-up since commercial lipases are chiefly limited to the cost as well as long reaction time. While numerous lipases were studied and proven to have the high catalytic capacity, still enzymatic reaction requires more investigation. To fill this gap, finding optimal conditions for the reaction such as alcohol and oil choice, water content, reaction time and temperature through proper reaction modelling and simulations as well as the appropriate design and use of reactors for large scale production are crucial issues that need to be accurately addressed. Furthermore, lipase concentration, alternative lipase resources through whole cell technology and genetic engineering, recent immobilizing materials including nanoparticles, and the capacity of enzyme to be reused are important criteria to be neatly investigated. The present work reviews the current biodiesel feedstock, catalysis, general and novel immobilizing materials, bioreactors for enzymatic transesterification, potential lipase resources, intensification technics, and process modelling for enzymatic

  11. Enzymatic and free radical formation of cis- and trans- epoxyeicosatrienoic acids in vitro and in vivo.

    Science.gov (United States)

    Aliwarga, Theresa; Raccor, Brianne S; Lemaitre, Rozenn N; Sotoodehnia, Nona; Gharib, Sina A; Xu, Libin; Totah, Rheem A

    2017-11-01

    Epoxyeicosatrienoic acids (EETs) are metabolites of arachidonic acid (AA) oxidation that have important cardioprotective and signaling properties. AA is an ω-6 polyunsaturated fatty acid (PUFA) that is prone to autoxidation. Although hydroperoxides and isoprostanes are major autoxidation products of AA, EETs are also formed from the largely overlooked peroxyl radical addition mechanism. While autoxidation yields both cis- and trans-EETs, cytochrome P450 (CYP) epoxygenases have been shown to exclusively catalyze the formation of all regioisomer cis-EETs, on each of the double bonds. In plasma and red blood cell (RBC) membranes, cis- and trans-EETs have been observed, and both have multiple physiological functions. We developed a sensitive ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) assay that separates cis- and trans- isomers of EETs and applied it to determine the relative distribution of cis- vs. trans-EETs in reaction mixtures of AA subjected to free radical oxidation in benzene and liposomes in vitro. We also determined the in vivo distribution of EETs in several tissues, including human and mouse heart, and RBC membranes. We then measured EET levels in heart and RBC of young mice compared to old. Formation of EETs in free radical reactions of AA in benzene and in liposomes exhibited time- and AA concentration-dependent increase and trans-EET levels were higher than cis-EETs under both conditions. In contrast, cis-EET levels were overall higher in biological samples. In general, trans-EETs increased with mouse age more than cis-EETs. We propose a mechanism for the non-enzymatic formation of cis- and trans-EETs involving addition of the peroxyl radical to one of AA's double bonds followed by bond rotation and intramolecular homolytic substitution (S H i). Enzymatic formation of cis-EETs by cytochrome P450 most likely occurs via a one-step concerted mechanism that does not allow bond rotation. The ability to accurately measure

  12. Enzymatic modification of natural and synthetic polymers using lipases and proteases

    Science.gov (United States)

    Chakraborty, Soma

    Enzymatic modification of natural/synthetic polymers [starch nanoparticles, poly (n-alkyl acrylates) and poly(vinyl formamide)] was studied. Enzymes used for catalysis were lipases and proteases. Starch nanoparticles (40nm diameter) were incorporated into AOT-coated reverse micelles. Reactions performed with the acylating agents vinyl stearate, epsilon-caprolactone and maleic anhydride in toluene in presence of Novozyme-435 at 40°C for 36h gave products with degrees of substitution of 0.8, 0.6 and 0.4 respectively. DEPT-135 NMR spectra revealed that the modification occurred regioselectively at the C-6 position of the glucose units. Infrared microspectroscopy showed that the surfactant coated starch nanoparticles diffuse into pores of Novozyme-435 beads, coming in close proximity with CALB to promote modification. The modified products retained nanoscale dimensions. Catalysis of amide bond formation between a low molar mass amine and ester side groups of poly(n-alkyl acrylates)[poly(ethyl acrylate), poly(methyl acrylate) and poly(butyl acrylate)] was also examined. The nucleophiles were mono and diamines. Among the poly(n-alkyl acrylates) and the lipases studied, poly(ethyl acrylate) was the preferred substrate and Novozyme-435 the most active lipase. Poly(ethyl acrylate) in 80% by-volume toluene was reacted with 1 equivalent per repeat unit of hexyl amine at 70°C in presence of Novozyme-435. The product contained 10.6 mol% amide groups. Attempts to increase the amidation beyond 10--11 mol% by increasing the reaction time or use of fresh enzyme were unsuccessful, showing that poly(ethylacrylate-co-10mol%hexylacrylamide) is a poor substrate for further acylation. When chiral amines ([R,S]-alpha-methyl benzylamine, [R,S]-beta-methyl phenyl amine) were used as nucleophiles, Novozyme-435 enantioselectively catalyzed amidation of poly(ethyl acrylate). Poly(vinyl formamide), P(VfAm) by acid or base-catalyzed hydrolysis leads to poly(vinylamine), P(VAm), and

  13. Recent Advances in Enzymatic Fuel Cells: Experiments and Modeling

    Directory of Open Access Journals (Sweden)

    Ivan Ivanov

    2010-04-01

    Full Text Available Enzymatic fuel cells convert the chemical energy of biofuels into electrical energy. Unlike traditional fuel cell types, which are mainly based on metal catalysts, the enzymatic fuel cells employ enzymes as catalysts. This fuel cell type can be used as an implantable power source for a variety of medical devices used in modern medicine to administer drugs, treat ailments and monitor bodily functions. Some advantages in comparison to conventional fuel cells include a simple fuel cell design and lower cost of the main fuel cell components, however they suffer from severe kinetic limitations mainly due to inefficiency in electron transfer between the enzyme and the electrode surface. In this review article, the major research activities concerned with the enzymatic fuel cells (anode and cathode development, system design, modeling by highlighting the current problems (low cell voltage, low current density, stability will be presented.

  14. Enzymatic saccharification of brown seaweed for production of fermentable sugars.

    Science.gov (United States)

    Sharma, Sandeep; Horn, Svein Jarle

    2016-08-01

    This study shows that high drying temperatures negatively affect the enzymatic saccharification yield of the brown seaweed Saccharina latissima. The optimal drying temperature of the seaweed in terms of enzymatic sugar release was found to be 30°C. The enzymatic saccharification process was optimized by investigating factors such as kinetics of sugar release, enzyme dose, solid loading and different blend ratios of cellulases and an alginate lyase. It was found that the seaweed biomass could be efficiently hydrolysed to fermentable sugars using a commercial cellulase cocktail. The inclusion of a mono-component alginate lyase was shown to improve the performance of the enzyme blend, in particular at high solid loadings. At 25% dry matter loading a combined glucose and mannitol concentration of 74g/L was achieved. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. High volumetric power density, non-enzymatic, glucose fuel cells.

    Science.gov (United States)

    Oncescu, Vlad; Erickson, David

    2013-01-01

    The development of new implantable medical devices has been limited in the past by slow advances in lithium battery technology. Non-enzymatic glucose fuel cells are promising replacement candidates for lithium batteries because of good long-term stability and adequate power density. The devices developed to date however use an "oxygen depletion design" whereby the electrodes are stacked on top of each other leading to low volumetric power density and complicated fabrication protocols. Here we have developed a novel single-layer fuel cell with good performance (2 μW cm⁻²) and stability that can be integrated directly as a coating layer on large implantable devices, or stacked to obtain a high volumetric power density (over 16 μW cm⁻³). This represents the first demonstration of a low volume non-enzymatic fuel cell stack with high power density, greatly increasing the range of applications for non-enzymatic glucose fuel cells.

  16. Biocolloids with ordered urease multilayer shells as enzymatic reactors.

    Science.gov (United States)

    Lvov, Y; Caruso, F

    2001-09-01

    The preparation of biocolloids with organized enzyme-containing multilayer shells for exploitation as colloidal enzymatic nanoreactors is described. Urease multilayers were assembled onto submicrometer-sized polystyrene spheres by the sequential adsorption of urease and polyelectrolyte, in a predetermined order, utilizing electrostatic interactions for layer growth. The catalytic activity of the biocolloids increased proportionally with the number of urease layers deposited on the particles, demonstrating that biocolloid particles with tailored enzymatic activities can be produced. It was further found that precoating the latex spheres with nanoparticles (40-nm silica or 12-nm magnetite) enhanced both the stability (with respect to adsorption) and enzymatic activity of the urease multilayers. The presence of the magnetite nanoparticle coating also provided a magnetic function that allowed the biocolloids to be easily and rapidly separated with a permanent magnet. The fabrication of such colloids opens new avenues for the application of bioparticles and represents a promising route for the creation of complex catalytic particles.

  17. Multiple enzymatic profiles of Vibrio parahaemolyticus strains isolated from oysters

    Directory of Open Access Journals (Sweden)

    Renata Albuquerque Costa

    Full Text Available The enzymatic characterization of vibrios has been used as a virulence indicator of sanitary interest. The objective of this study was to determine the enzymatic profile of Vibrio parahaemolyticus strains (n = 70 isolated from Crassostrea rhizophorae oysters. The strains were examined for the presence of gelatinase (GEL, caseinase (CAS, elastase (ELAS, phospholipase (PHOS, lipase (LIP, amilase (AML and DNase. All enzymes, except elastase, were detected in more than 60% of the strains. The most recurrent enzymatic profiles were AML + DNase + PHOS + GEL + LIP (n = 16; 22.9% and AML + CAS + DNase + PHOS + GEL + LIP (n = 21; 30%. Considering the fact that exoenzyme production by vibrios is closely related to virulence, one must be aware of the bacteriological risk posed to human health by the consumption of raw or undercooked oysters.

  18. EPSPS variability, gene expression, and enzymatic activity in glyphosate-resistant biotypes of Digitaria insularis.

    Science.gov (United States)

    Galeano, E; Barroso, A A M; Vasconcelos, T S; López-Rubio, A; Albrecht, A J P; Victoria Filho, R; Carrer, H

    2016-08-12

    Weed resistance to herbicides is a natural phenomenon that exerts selection on individuals in a population. In Brazil, glyphosate resistance was recently detected in Digitaria insularis. The objective of this study was to elucidate mechanisms of weed resistance in this plant, including genetic variability, allelism, amino acid substitutions, gene expression, and enzymatic activity levels. Most of these have not previously been studied in this species. D. insularis DNA sequences were used to analyze genetic variability. cDNA from resistant and susceptible plants was used to identify mutations, alleles, and 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) expression, using real-time quantitative reverse transcription-polymerase chain reaction. In addition, EPSPS activity was measured. We found a decrease in genetic variability between populations related to glyphosate application. Substitutions from proline to threonine and tyrosine to cysteine led to a decrease in EPSPS affinity for the glyphosate. In addition, the EPSPS enzymatic activity was slightly higher in resistant plants, whereas EPSPS gene expression was almost identical in both biotypes, suggesting feedback regulation at different levels. To conclude, our results suggest new molecular mechanisms used by D. insularis to increase glyphosate resistance.

  19. Enzymatic analysis of Hemiscorpius lepturus scorpion venom using zymography and venom-specific antivenin.

    Science.gov (United States)

    Seyedian, Ramin; Pipelzadeh, Mohammad Hassan; Jalali, Amir; Kim, Euikyung; Lee, Hyunkyoung; Kang, Changkeun; Cha, Mijin; Sohn, Eun-Tae; Jung, Eun-Sun; Rahmani, Ali Hassan; Mirakabady, Abbas Zare

    2010-09-15

    Hemiscorpius lepturus envenomation exhibits various pathological changes in the affected tissues, including skin, blood cells, cardiovascular and central nervous systems. The enzymatic activity and protein component of the venom have not been described previously. In the present study, the electrophoretic profile of H. lepturus venom was determined by SDS-PAGE (12 and 15%), resulting in major protein bands at 3.5-5, 30-35 and 50-60 kDa. The enzymatic activities of the venom was, for the first time, investigated using various zymography techniques, which showed the gelatinolytic, caseinolytic, and hyaluronidase activities mainly at around 50-60 kDa, 30-40 kDa, and 40-50 kDa, respectively. Among these, the proteolytic activities was almost completely disappeared in the presence of a matrix metalloproteinase inhibitor, 1, 10-phenanthroline. Antigen-antibody interactions between the venom and its Iranian antivenin was observed by Western blotting, and it showed several antigenic proteins in the range of 30-160 kDa. This strong antigen-antibody reaction was also demonstrated through an enzyme-linked immunosorbent assay (ELISA). The gelatinase activity of the venom was suppressed by Razi institute polyvalent antivenin, suggesting the inhibitory effect of the antivenin against H. lepturus venom protease activities. Prudently, more extensive clinical studies are necessary for validation of its use in envenomed patients. Copyright 2010 Elsevier Ltd. All rights reserved.

  20. Kinetics of enzymatic high-solid hydrolysis of lignocellulosic biomass studied by calorimetry.

    Science.gov (United States)

    Olsen, Søren N; Lumby, Erik; McFarland, Kc; Borch, Kim; Westh, Peter

    2011-03-01

    Enzymatic hydrolysis of high-solid biomass (>10% w/w dry mass) has become increasingly important as a key step in the production of second-generation bioethanol. To this end, development of quantitative real-time assays is desirable both for empirical optimization and for detailed kinetic analysis. In the current work, we have investigated the application of isothermal calorimetry to study the kinetics of enzymatic hydrolysis of two substrates (pretreated corn stover and Avicel) at high-solid contents (up to 29% w/w). It was found that the calorimetric heat flow provided a true measure of the hydrolysis rate with a detection limit of about 500 pmol glucose s(-1). Hence, calorimetry is shown to be a highly sensitive real-time method, applicable for high solids, and independent on the complexity of the substrate. Dose-response experiments with a typical cellulase cocktail enabled a multidimensional analysis of the interrelationships of enzyme load and the rate, time, and extent of the reaction. The results suggest that the hydrolysis rate of pretreated corn stover is limited initially by available attack points on the substrate surface (conversion) but becomes proportional to enzyme dosage (excess of attack points) at later stages (>10% conversion). This kinetic profile is interpreted as an increase in polymer end concentration (substrate for CBH) as the hydrolysis progresses, probably due to EG activity in the enzyme cocktail. Finally, irreversible enzyme inactivation did not appear to be the source of reduced hydrolysis rate over time.

  1. Low melting point pyridinium ionic liquid pretreatment for enhancing enzymatic saccharification of cellulosic biomass.

    Science.gov (United States)

    Uju; Nakamoto, Aya; Shoda, Yasuhiro; Goto, Masahiro; Tokuhara, Wataru; Noritake, Yoshiyuki; Katahira, Satoshi; Ishida, Nobuhiro; Ogino, Chiaki; Kamiya, Noriho

    2013-05-01

    The potential of 1-hexylpyridinium chloride ([Hpy][Cl]), to pretreat cellulosic feedstocks was investigated using microcrystalline cellulose (Avicel) and Bagasse at 80 °C or 100 °C. Short [Hpy][Cl] pretreatments, conversion of pretreated Avicel to glucose was attained after 24h enzymatic saccharification under optimal conditions, whereas regenerated Bagasse showed 1-3-fold higher conversion than untreated biomass. FT-IR analysis of both Avicel and Bagasse samples pretreated with [Hpy][Cl] or 1-ethyl-3-methyimidazolium acetate ([Emim][OAc]) revealed that these ionic liquids behaved differently during pretreatment. [Hpy][Cl] pretreatment for an extended duration (180 min) released mono- and disaccharides without using cellulase enzymes, suggesting [Hpy][Cl] has capability for direct saccharification of cellulosic feedstocks. On the basis of the results obtained, [Hpy][Cl] pretreatment enhanced initial reaction rates in enzymatic saccharification by either crystalline polymorphic alteration of cellulose or partial degradation of the crystalline cellulosic fraction in biomass. Copyright © 2012 Elsevier Ltd. All rights reserved.

  2. Colorimetric determination of nitrate plus nitrite in water by enzymatic reduction, automated discrete analyzer methods

    Science.gov (United States)

    Patton, Charles J.; Kryskalla, Jennifer R.

    2011-01-01

    This report documents work at the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) to validate enzymatic reduction, colorimetric determinative methods for nitrate + nitrite in filtered water by automated discrete analysis. In these standard- and low-level methods (USGS I-2547-11 and I-2548-11), nitrate is reduced to nitrite with nontoxic, soluble nitrate reductase rather than toxic, granular, copperized cadmium used in the longstanding USGS automated continuous-flow analyzer methods I-2545-90 (NWQL laboratory code 1975) and I-2546-91 (NWQL laboratory code 1979). Colorimetric reagents used to determine resulting nitrite in aforementioned enzymatic- and cadmium-reduction methods are identical. The enzyme used in these discrete analyzer methods, designated AtNaR2 by its manufacturer, is produced by recombinant expression of the nitrate reductase gene from wall cress (Arabidopsis thaliana) in the yeast Pichia pastoris. Unlike other commercially available nitrate reductases we evaluated, AtNaR2 maintains high activity at 37°C and is not inhibited by high-phenolic-content humic acids at reaction temperatures in the range of 20°C to 37°C. These previously unrecognized AtNaR2 characteristics are essential for successful performance of discrete analyzer nitrate + nitrite assays (henceforth, DA-AtNaR2) described here.

  3. Enzymatic polymerization of aniline in the presence of different inorganic substrates

    Energy Technology Data Exchange (ETDEWEB)

    Flores-Loyola, E. [Centro de Investigacion en Quimica Aplicada, Blvd. Enrique Reyna No. 140, CP 25100 Saltillo, Coah (Mexico); Escuela de Ciencias Biologicas, UA de C. Carr. Torreon-Matamoros Km 7.5, Ciudad Universitaria, CP 27400 Torreon, Coah. (Mexico)], E-mail: erika-flores@mail.uadec.mx; Cruz-Silva, R. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas, UAEM. Av. Universidad 1001, Col. Chamilpa, CP 62210, Cuernavaca Mor. (Mexico); Romero-Garcia, J.; Angulo-Sanchez, J.L. [Centro de Investigacion en Quimica Aplicada, Blvd. Enrique Reyna No. 140, CP 25100 Saltillo, Coah (Mexico); Castillon, F.F.; Farias, M.H. [Centro de Ciencias de la Materia Condensada de la UNAM, Apdo. Postal 2681, CP 22800 Ensenada, B.C. (Mexico)

    2007-09-15

    The effect of different inorganic substrates in the structure of polyaniline synthesized by enzymatic oxidation was studied. The polymer characterization was done by electronic absorption and X-ray photoelectron spectroscopy. The substrates studied were: controlled pore glass, mordenite, zeolite Y, zeolite MCM-41, Wollastonite, silica gel, fuming silica and short glass fibers type E. Polyaniline was synthesized in the presence of the substrates under acidic aqueous conditions, using hydrogen peroxide as oxidizer and HRP or SBP enzymes as catalyst. The composition of the substrates strongly affected the degree of electronic conjugation of the synthesized polyaniline, whereas the pore size and the enzyme type apparently had no effect. The chemical structure of polyaniline enzymatically synthesized was more sensitive to the substrate composition than that chemically synthesized. Apparently substrates containing alkaline ions, such as sodium and calcium, promoted the formation of the branched, non-conductive polyaniline form. The effect of the substrates on the polyaniline structure can be explained considering the local pH effect of the templates surface on the coupling reaction of aniline radicals.

  4. Applications of Potential Energy Surfaces in the Study of Enzymatic Reactions

    OpenAIRE

    Bushnell, Eric A. C.; Huang, WenJuan; Gauld, James W.

    2012-01-01

    From a generated PES, one can determine the relative energies of species involved, the sequence in which they occur, and the activation barrier(s) associated with individual steps or the overall mechanism. Furthermore, they can provide more insights than a simple indication of a path of sequential mechanistic structures and their energetic relationships. The investigation into the activation of O2 by alpha-ketoglutarate-dependent dioxygenase (AlkB) clearly shows the opportunity for spin inver...

  5. Applications of Potential Energy Surfaces in the Study of Enzymatic Reactions

    Directory of Open Access Journals (Sweden)

    Eric A. C. Bushnell

    2012-01-01

    Full Text Available From a generated PES, one can determine the relative energies of species involved, the sequence in which they occur, and the activation barrier(s associated with individual steps or the overall mechanism. Furthermore, they can provide more insights than a simple indication of a path of sequential mechanistic structures and their energetic relationships. The investigation into the activation of O2 by alpha-ketoglutarate-dependent dioxygenase (AlkB clearly shows the opportunity for spin inversion, where one can see that the lowest energy product may be formed via several possible routes. In the investigation of uroporphyrinogen decarboxylase III (UROD, the use of QM/MM methods allowed for the inclusion of the anisotropic protein environment providing greater insight into the rate-limiting barrier. Lastly, the mechanism of 6-phospho-α-glucosidase (GlvA was discussed using different active site models. In particular, a continuum model PES was compared to the gas-phase PES.

  6. Cationic polymers for DNA origami coating - examining their binding efficiency and tuning the enzymatic reaction rates.

    Science.gov (United States)

    Kiviaho, Jenny K; Linko, Veikko; Ora, Ari; Tiainen, Tony; Järvihaavisto, Erika; Mikkilä, Joona; Tenhu, Heikki; Nonappa; Kostiainen, Mauri A

    2016-06-02

    DNA origamis are fully tailored, programmable, biocompatible and readily functionalizable nanostructures that provide an excellent foundation for the development of sophisticated drug-delivery systems. However, the DNA origami objects suffer from certain drawbacks such as low cell-transfection rates and low stability. A great deal of studies on polymer-based transfection agents, mainly focusing on polyplex formation and toxicity, exists. In this study, the electrostatic binding between a brick-like DNA origami and cationic block-copolymers was explored. The effect of the polymer structure on the binding was investigated and the toxicity of the polymer-origami complexes evaluated. The study shows that all of the analyzed polymers had a suitable binding efficiency irrespective of the block structure. It was also observed that the toxicity of polymer-origami complexes was insignificant at the biologically relevant concentration levels. Besides brick-like DNA origamis, tubular origami carriers equipped with enzymes were also coated with the polymers. By adjusting the amount of cationic polymers that cover the DNA structures, we showed that it is possible to control the enzyme kinetics of the complexes. This work gives a starting point for further development of biocompatible and effective polycation-based block copolymers that can be used in coating different DNA origami nanostructures for various bioapplications.

  7. Investigation of oxidative degradation and non‐enzymatic browning reactions in krill and fish oils

    DEFF Research Database (Denmark)

    Thomsen, Birgitte Raagaard; Haugsgjerd, Bjørn Ole; Griinari, Mikko

    2013-01-01

    conditions using the Oxipres™ at 90°C. The results from analysis of PV, AV, TBARS, conjugated dienes and trienes, and the antioxidant content suggested that krill oil was more oxidatively stable than fish oil. However, the color or other constituents of the krill oil might affect the result......The aim of this research was to investigate the oxidation progress and pathways of krill and fish oil during 21 days of incubation at 40°C. The oxidative stability of the oils was investigated through: (i) classical methods such as peroxide value (PV), anisidine value (AV), thiobarbituric reactive...... substance (TBARS), conjugated dienes and trienes, and antioxidant content, and (ii) advanced methods such as determination of volatiles content by dynamic headspace (DHS)‐GC/MS, lipid classes, and pyrrole content. In addition, the oxidative stability of the oils was evaluated under accelerated oxidation...

  8. Using in vitro derived enzymatic reaction rates of metabolism to inform pesticide body burdens in amphibians

    Science.gov (United States)

    Understanding how pesticide exposure to non-target species influences toxicity is necessary to accurately assess the ecological risks these compounds pose. To assess the potential metabolic activation of broad use pesticides in amphibians, in vitro and in vivo metabolic rate cons...

  9. A multi-enzymatic cascade reaction for the stereoselective production of γ-oxyfunctionalyzed amino acids

    Directory of Open Access Journals (Sweden)

    Junichi eEnoki

    2016-04-01

    Full Text Available A stereoselective three-enzyme cascade for synthesis of diasteromerically pure γ-oxyfunctionalized α-amino acids was developed. By coupling a dynamic kinetic resolution using an N-acylamino acid racemase and an L-selective aminoacylase from Geobacillus thermoglucosidasius with a stereoselective isoleucine dioxygenase from Bacillus thuringiensis, diastereomerically pure oxidized amino acids were produced from racemic N-acetylamino acids. The three enzymes differ in their optimal temperature and pH-spectra. Their different metal cofactor dependencies lead to inhibitory effects. Under optimized conditions, racemic N-acetylmethionine was quantitatively converted into L-methionine-(S-sulfoxide with 97% conversion and 95% de. The combination of these three different biocatalysts allows the direct synthesis of diastereopure oxyfunctionalized amino acids from inexpensive racemic starting material.

  10. Immobilization of Mucor miehei Lipase onto Macroporous Aminated Polyethersulfone Membrane for Enzymatic Reactions

    NARCIS (Netherlands)

    Handayani, Nurrahmi; Loos, Katja; Wahyuningrum, Deana; Buchari, [No Value; Zulfikar, Muhammad Ali

    2012-01-01

    Immobilization of enzymes is one of the most promising methods in enzyme performance enhancement, including stability, recovery, and reusability. However, investigation of suitable solid support in enzyme immobilization is still a scientific challenge. Polyethersulfone (PES) and aminated PES

  11. Oxidative stability and non-enzymatic browning reactions in Antarctic krill oil (Euphausia superba)

    DEFF Research Database (Denmark)

    Lu, Henna Fung Sieng; Bruheim, Inge; Jacobsen, Charlotte

    2014-01-01

    Antarctic krill oil has gained much consideration recently due to its rich content of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the form of phospholipids and its powerful antioxidant known as astaxanthin. To secure these valuable bioactive nutrients in krill oil, a gentle...

  12. Cationic polymers for DNA origami coating - examining their binding efficiency and tuning the enzymatic reaction rates

    Science.gov (United States)

    Kiviaho, Jenny K.; Linko, Veikko; Ora, Ari; Tiainen, Tony; Järvihaavisto, Erika; Mikkilä, Joona; Tenhu, Heikki; Nonappa, Affc; Kostiainen, Mauri A.

    2016-06-01

    DNA origamis are fully tailored, programmable, biocompatible and readily functionalizable nanostructures that provide an excellent foundation for the development of sophisticated drug-delivery systems. However, the DNA origami objects suffer from certain drawbacks such as low cell-transfection rates and low stability. A great deal of studies on polymer-based transfection agents, mainly focusing on polyplex formation and toxicity, exists. In this study, the electrostatic binding between a brick-like DNA origami and cationic block-copolymers was explored. The effect of the polymer structure on the binding was investigated and the toxicity of the polymer-origami complexes evaluated. The study shows that all of the analyzed polymers had a suitable binding efficiency irrespective of the block structure. It was also observed that the toxicity of polymer-origami complexes was insignificant at the biologically relevant concentration levels. Besides brick-like DNA origamis, tubular origami carriers equipped with enzymes were also coated with the polymers. By adjusting the amount of cationic polymers that cover the DNA structures, we showed that it is possible to control the enzyme kinetics of the complexes. This work gives a starting point for further development of biocompatible and effective polycation-based block copolymers that can be used in coating different DNA origami nanostructures for various bioapplications.DNA origamis are fully tailored, programmable, biocompatible and readily functionalizable nanostructures that provide an excellent foundation for the development of sophisticated drug-delivery systems. However, the DNA origami objects suffer from certain drawbacks such as low cell-transfection rates and low stability. A great deal of studies on polymer-based transfection agents, mainly focusing on polyplex formation and toxicity, exists. In this study, the electrostatic binding between a brick-like DNA origami and cationic block-copolymers was explored. The effect of the polymer structure on the binding was investigated and the toxicity of the polymer-origami complexes evaluated. The study shows that all of the analyzed polymers had a suitable binding efficiency irrespective of the block structure. It was also observed that the toxicity of polymer-origami complexes was insignificant at the biologically relevant concentration levels. Besides brick-like DNA origamis, tubular origami carriers equipped with enzymes were also coated with the polymers. By adjusting the amount of cationic polymers that cover the DNA structures, we showed that it is possible to control the enzyme kinetics of the complexes. This work gives a starting point for further development of biocompatible and effective polycation-based block copolymers that can be used in coating different DNA origami nanostructures for various bioapplications. Electronic supplementary information (ESI) available: Details of materials, syntheses of the polymers, fabrication and purification of DNA origamis, luminescence decay assays, agarose gel electrophoresis, ethidium bromide displacement assay, MTT assay and TEM characterization. See DOI: 10.1039/c5nr08355a

  13. Production of specific structured lipids by enzymatic interesterification: optimization of the reaction by response surface design

    DEFF Research Database (Denmark)

    Xu, Xuebing; Skands, Anja Rebecca Havegaard; Adler-Nissen, Jens

    1998-01-01

    Rapeseed oil and capric acid were interesterified in solvent-free media catalyzed by Lipozyme IM (Rhizomucor miehei) to produce specific-structured lipids (SSLs). The process was optimized by response surface design concerning the effects of acyl migration and the by-products of diacylglycerols...

  14. Enzymatic synthesizing of phytosterol oleic esters.

    Science.gov (United States)

    Pan, Xinxin; Chen, Biqiang; Wang, Juan; Zhang, Xinzhi; Zhul, Biyun; Tan, Tianwei

    2012-09-01

    A method of synthesizing the phytosterol esters from oleic acid and sterols was studied, using immobilized lipase Candida sp. 99-125 as catalyst. Molar ratio (oleic acid/phytosterols), temperature, reaction period, organic solvents, catalyst, and silica-gel drier were optimized, and the result showed that 93.4% of the sterols had been esterified under the optimal synthetic condition: the molar ratio of oleic acid/phytosterol is 1:1 in 10 mL iso-octane, immobilized lipase (w, 140% of the sterols), incubated in an orbital shaker (200 rpm) at a temperature of 45 °C for 24 h. The immobilized lipase could be reused for at least 13 times with limited loss of esterification activity. The conversion still maintained up to 86.6%. Hence, this developed process for synthesizing phytosterol esters could be considered as simple and low-energy consumption compared to existing chemical processes.

  15. Modification of margarine fats by enzymatic interesterification:

    DEFF Research Database (Denmark)

    Zhang, Hong; Pedersen, Lars Saaby; Kristensen, Dorther

    2004-01-01

    to the equilibrium state, and (iii) the reaction rate constant value (k). SFC0 and ΔSFC were related to only the types of blends and the blend ratios. The rate constant k was related to lipase activity on a given oil blend. Evaluation of the model was carried out with two groups of oil blends, i.e., palm stearin/coconut...... oil in weight ratios of 90:10, 80:20, and 70:30, and soybean oil/fully hydrogenated soybean oil in weight ratios of 80:20, 65:35, and 50:50. Correlation coefficients higher than 0.99 between the experimental and predicted values were observed for SFC at temperatures above 30°C. The model is useful...... for predicting changes in the SFC during lipase-catalyzed interesterification with a selected group of oil blends. It also can be used to control the process when particular SFC values are targeted....

  16. Enzymatic radioiodination of insulin for radioimmunoassay use

    Energy Technology Data Exchange (ETDEWEB)

    Awh, O D; Kim, J R [Korea Atomic Energy Research Inst., Seoul (Republic of Korea)

    1980-06-01

    Insulin was labelled with /sup 125/I using lactoperoxidase as an oxidizing agent. The reaction product was purified via two stages; a starch gel electrophoresis(SGE) and a Sephadex gel filtration(SF). Upon comparison of the labelling yields and the bindabilities of the labelled insulin to its antibody, it has been found that the enzyme method shows higher yields (50%) and the better bindability to its antibody than the conventional chloramine-T method (35%). By checking the insulin blank labelling mixture with a SGE, a paper chromatography, and a radioautography technique, a by-product in the lactoperoxidase method has been identified. The separated fractions in SGE and SF were also analyzed and discussed.

  17. Therapeutic effectiveness of a new enzymatic bleaching dentifrice.

    Science.gov (United States)

    Forner, Leopaldo; Amengual, José; Liena, Carmen; Riutord, Pere

    2012-01-01

    Research into bleaching focuses on new products in order to minimize undesirable effects. This study evaluated the bleaching effectiveness of a new enzymatic-activated dentifrice. A total of 20 volunteers were bleached with a dentifrice containing 5% lactoperoxidase and 3% carbamide peroxide applied three times a day for two minutes over 21 days. Color was recorded before and after the treatment using a spectrophotometer. CIELAB differences were calculated before and after treatment using the paired t test (P whitening teeth. Enzymatic dental bleaching is able to increase the efficiency of low concentration peroxides, reducing the potential risk of peroxides on oral tissues.

  18. Adhesion improvement of lignocellulosic products by enzymatic pre-treatment.

    Science.gov (United States)

    Widsten, Petri; Kandelbauer, Andreas

    2008-01-01

    Enzymatic bonding methods, based on laccase or peroxidase enzymes, for lignocellulosic products such as medium-density fiberboard and particleboard are discussed with reference to the increasing costs of presently used petroleum-based adhesives and the health concerns associated with formaldehyde emissions from current composite products. One approach is to improve the self-bonding properties of the particles by oxidation of their surface lignin before they are fabricated into boards. Another method involves using enzymatically pre-treated lignins as adhesives for boards and laminates. The application of this technology to achieve wet strength characteristics in paper is also reviewed.

  19. Optimization of Substrate Feeding for Enzymatic Biodiesel Production

    DEFF Research Database (Denmark)

    Price, Jason Anthony; Huusom, Jakob Kjøbsted; Nordblad, Mathias

    2013-01-01

    to be effective in mitigating the effects of substrate inhibition. Using enzymatic biodiesel production as a case study, the volumetric productivity of the reactor is increased while minimizing inactivation of the enzyme due to the alcohol. This is done by using a simple optimization routine where the substrate...... (both the vegetable oil and alcohol) feed rate/concentration is manipulated simultaneously. The results of the simulation were tested in the laboratory and are sufficiently positive to suggest the implementation of a feeding strategy for large scale enzymatic biodiesel production...

  20. Moving towards a Competitive Fully Enzymatic Biodiesel Process

    Directory of Open Access Journals (Sweden)

    Silvia Cesarini

    2015-06-01

    Full Text Available Enzymatic biodiesel synthesis can solve several problems posed by the alkaline-catalyzed transesterification but it has the drawback of being too expensive to be considered competitive. Costs can be reduced by lipase improvement, use of unrefined oils, evaluation of soluble/immobilized lipase preparations, and by combination of phospholipases with a soluble lipase for biodiesel production in a single step. As shown here, convenient natural tools have been developed that allow synthesis of high quality FAMEs (EN14214 from unrefined oils in a completely enzymatic single-step process, making it fully competitive.

  1. Radiolytic and electron-transfer reactions in supercritical CO2

    International Nuclear Information System (INIS)

    Bartels, D. M.; Dimitrijevic, N. M.; Jonah, C. D.; Takahashi, K.

    2000-01-01

    Using supercritical fluids as solvents is useful for both practical and theoretical reasons. It has been proposed to use supercritical CO 2 as a solvent for synthesis because it eliminates the air pollution arising from other solvents. The properties of supercritical fluids can be easily varied with only modest changes in temperature and density, so they provide a way of testing theories of chemical reactions. It has also been proposed to use supercritical fluids for the treatment of hazardous mixed waste. For these reasons the authors have studied the production of radiolytic species in supercritical CO 2 and have measured their reactivity as a function of density. They have shown that the C 2 O 4 + is formed. They also have shown that the electron transfer reactions of dimethylaniline to C 2 O 4 + and CO 2 (e - ) to benzoquinone are diffusion controlled over a considerable density range

  2. Quasielastic reactions

    International Nuclear Information System (INIS)

    Hansen, O.

    1983-01-01

    A brief review is presented of the experimental and theoretical situation regarding transfer reactions and inelastic scattering. In the first category there is little (very little) precision data for heavy projectiles and consequently almost no experience with quantitative theoretical analysis. For the inelastic scattering the rather extensive data strongly supports the coupled channels models with collective formfactors. At the most back angles, at intensities about 10 -5 of Rutherford scattering, a second, compound-like mechanism becomes dominant. The description of the interplay of these two opposite mechanisms provides a new challenge for our understanding

  3. A comparative study between chemical and enzymatic transesterification of high free fatty acid contained rubber seed oil for biodiesel production

    Directory of Open Access Journals (Sweden)

    Jilse Sebastian

    2016-12-01

    Full Text Available The choice of a paramount method for biodiesel production has significance as the demand of alternative fuels like biodiesel is growing rapidly. In the present study, experimental results from chemical-catalysed as well as enzyme-catalysed methods were compared using common influencing parameters such as oil/alcohol molar ratio, catalyst concentration and reaction duration. Requirement of certain solvents to enhance the reaction rate was explained in the enzyme-catalysed transesterification reaction. Biodiesel conversion of more than 90% was attained for chemical-catalysed transesterification, whereas the conversion rate was 85% for enzyme-catalysed method. This gives the indication of further refinement in the enzyme-catalysed transesterification process. The influencing parameters and absolute results of the analysis give the impression of superiority of enzymatic transesterification method for biodiesel production from high free fatty acid-contained rubber seed oil.

  4. Solvent-free enzymatic synthesis of feruloylated structured lipids by the transesterification of ethyl ferulate with castor oil.

    Science.gov (United States)

    Sun, Shangde; Zhu, Sha; Bi, Yanlan

    2014-09-01

    A novel enzymatic route of feruloylated structured lipids synthesis by the transesterification of ethyl ferulate (EF) with castor oil, in solvent-free system, was investigated. The transesterification reactions were catalysed by Novozym 435, Lipozyme RMIM, and Lipozyme TLIM, among which Novozym 435 showed the best catalysis performance. Effects of feruloyl donors, reaction variables, and ethanol removal on the transesterification were also studied. High EF conversion (∼100%) was obtained under the following conditions: enzyme load 20% (w/w, relative to the weight of substrates), reaction temperature 90 °C, substrate molar ratio 1:1 (EF/castor oil), 72 h, vacuum pressure 10 mmHg, and 200 rpm. Under these conditions, the transesterification product consisted of 62.6% lipophilic feruloylated structured lipids and 37.3% hydrophilic feruloylated lipids. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Enzymatic transesterification of soybean oil with ethanol using lipases immobilized on highly crystalline PVA microspheres

    International Nuclear Information System (INIS)

    Bergamasco, Juliana; Araujo, Marcelo V. de; Vasconcellos, Adriano de; Luizon Filho, Roberto A.; Hatanaka, Rafael R.; Giotto, Marcus V.; Aranda, Donato A.G.; Nery, José G.

    2013-01-01

    Polyvinyl alcohol (PVA) microspheres with different degree of crystallinity were used as solid supports for Rhizomucor miehei lipase immobilization, and the enzyme-PVA complexes were used as biocatalysts for the transesterification of soybean oil to fatty acid ethyl esters (FAEE). The amounts of immobilized enzyme on the polymeric supports were similar for both the amorphous microspheres (PVA4) and the high crystalline microspheres (PVA25). However, the enzymatic activity of the immobilized enzymes was depended on the crystallinity degree of the PVA microspheres: enzymes immobilized on the PVA4 microspheres have shown low enzymatic activity (6.13 U mg −1 ), in comparison with enzymes immobilized on the high crystalline PVA25 microspheres (149.15 U mg −1 ). A synergistic effect was observed for the enzyme-PVA25 complex during the transesterification reaction of soybean oil to FAEE: transesterification reactions with free enzyme with the equivalent amount of enzyme that were immobilized onto the PVA25 microspheres (5.4 U) have yielded only 20% of FAEE, reactions with the pure highly crystalline microsphere PVA25 have not yielded FAEE, however reactions with the enzyme-PVA25 complexes have yielded 66.3% of FAEE. This synergistic effect of an immobilized enzyme on a polymeric support has not been observed before for transesterification reaction of triacylglycerides into FAEE. Based on ATR-FTIR, 23 Na- and 13 C-NMR-MAS spectroscopic data and the interaction of the polymeric network intermolecular hydrogen bonds with the lipases residual amino acids a possible explanation for this synergistic effect is provided. Highlights: • Rhizomucor miehei lipase was immobilized on PVA microspheres (PVA4, PVA12, PVA25). • Polymer-enzyme complex was characterized by XDR, SEM, ATR-FTIR, 13 C-CPMAS-NMR, 23 Na-MAS-NMR. • Polymer-enzymes (PVA12 and PVA25) enzymes yielded considerable amount of ethyl esters. • Synergistic effect was observed for the polymer-enzyme complexes

  6. Incorporation of medium chain fatty acids into fish oil triglycerides by chemical and enzymatic inter esterification

    Energy Technology Data Exchange (ETDEWEB)

    Feltes, M. M. C.; Oliveira de Pilot, L.; Gomes Correira, F.; Grimaldi, R.; Mara Block, J.; Ninow, J. L.

    2009-07-01

    Structured triglycerides (STs) containing both medium chain fatty acids (MCFA) and polyunsaturated fatty acids (PUFA) in the same molecule offer nutritional and therapeutic benefits. The aim of this work was to establish the incorporation of MCFA into fish oil triglycerides (TAGs), while maintaining substantial levels of docosahexaenoic and eicosapentaenoic acids. The effects of different acyl donors (capric acid methyl ester/MeC10 or medium chain triglyceride/TCM) and of the catalyst (chemical or enzymatic) on the fatty acid composition of the reaction product were studied. The fatty acid composition of the fish oil TAG was modified after inter esterification to contain MCFA, and it depended on the catalyst and on the substrates. Thermo grams obtained by Differential Scanning Calorimetry (DSC) showed that inter esterification promoted noteworthy changes in the melting profile of the samples. STs of clinical nutrition interest containing both EPA and DHA obtained from fish oil along with MCFA were successfully produced. (Author) 70 refs.

  7. Kinetics of Enzymatic High-Solid Hydrolysis of Lignocellulosic Biomass Studied by Calorimetry

    DEFF Research Database (Denmark)

    Olsen, Søren Nymand; Rasmussen, Erik Lumby; McFarland, K.C.

    2011-01-01

    analysis of the interrelationships of enzyme load and the rate, time, and extent of the reaction. The results suggest that the hydrolysis rate of pretreated corn stover is limited initially by available attack points on the substrate surface (conversion) but becomes proportional to enzyme dosage......Enzymatic hydrolysis of high-solid biomass (>10% w/w dry mass) has become increasingly important as a key step in the production of second-generation bioethanol. To this end, development of quantitative real-time assays is desirable both for empirical optimization and for detailed kinetic analysis...... rate with a detection limit of about 500 pmol glucose s−1. Hence, calorimetry is shown to be a highly sensitive real-time method, applicable for high solids, and independent on the complexity of the substrate. Dose–response experiments with a typical cellulase cocktail enabled a multidimensional...

  8. Application of Ni(II-assisted peptide bond hydrolysis to non-enzymatic affinity tag removal.

    Directory of Open Access Journals (Sweden)

    Edyta Kopera

    Full Text Available In this study, we demonstrate a non-enzymatic method for hydrolytic peptide bond cleavage, applied to the removal of an affinity tag from a recombinant fusion protein, SPI2-SRHWAP-His(6. This method is based on a highly specific Ni(II reaction with (S/TXHZ peptide sequences. It can be applied for the protein attached to an affinity column or to the unbound protein in solution. We studied the effect of pH, temperature and Ni(II concentration on the efficacy of cleavage and developed an analytical protocol, which provides active protein with a 90% yield and ∼100% purity. The method works well in the presence of non-ionic detergents, DTT and GuHCl, therefore providing a viable alternative for currently used techniques.

  9. Expression of Enzymatically Inactive Wasp Venom Phospholipase A1 in Pichia pastoris

    DEFF Research Database (Denmark)

    Borodina, Irina; Jensen, Bettina M.; Wagner, Tim

    2011-01-01

    Wasp venom allergy is the most common insect venom allergy in Europe. It is manifested by large local reaction or anaphylactic shock occurring after a wasp sting. The allergy can be treated by specific immunotherapy with whole venom extracts. Wasp venom is difficult and costly to obtain...... and is a subject to composition variation, therefore it can be advantageous to substitute it with a cocktail of recombinant allergens. One of the major venom allergens is phospholipase A1, which so far has been expressed in Escherichia coli and in insect cells. Our aim was to produce the protein in secreted form...... in yeast Pichia pastoris, which can give high yields of correctly folded protein on defined minimal medium and secretes relatively few native proteins simplifying purification.Residual amounts of enzymatically active phospholipase A1 could be expressed, but the venom protein had a deleterious effect...

  10. Expression of enzymatically inactive wasp venom phospholipase A1 in Pichia pastoris

    DEFF Research Database (Denmark)

    Borodina, Irina; Jensen, Bettina M.; Wagner, Tim

    Wasp venom allergy is the most common insect venom allergy in Europe. It is manifested by large local reaction or anaphylactic shock occurring after a wasp sting. The allergy can be treated by specific immunotherapy with whole venom extracts. Wasp venom is difficult and costly to obtain...... and is a subject to composition variation, therefore it can be advantageous to substitute it with a cocktail of recombinant allergens. One of the major venom allergens is phospholipase A1, which so far has been expressed in Escherichia coli and in insect cells. Our aim was to produce the protein in secreted form...... in yeast Pichia pastoris, which can give high yields of correctly folded protein on defined minimal medium and secretes relatively few native proteins simplifying purification. Residual amounts of enzymatically active phospholipase A1 could be expressed, but the venom protein had a deleterious effect...

  11. Expression of enzymatically inactive wasp venom phospholipase A1 in Pichia pastoris

    DEFF Research Database (Denmark)

    Borodina, Irina; Jensen, Bettina M; Wagner, Tim

    2011-01-01

    Wasp venom allergy is the most common insect venom allergy in Europe. It is manifested by large local reaction or anaphylactic shock occurring after a wasp sting. The allergy can be treated by specific immunotherapy with whole venom extracts. Wasp venom is difficult and costly to obtain...... and is a subject to composition variation, therefore it can be advantageous to substitute it with a cocktail of recombinant allergens. One of the major venom allergens is phospholipase A1, which so far has been expressed in Escherichia coli and in insect cells. Our aim was to produce the protein in secreted form...... in yeast Pichia pastoris, which can give high yields of correctly folded protein on defined minimal medium and secretes relatively few native proteins simplifying purification.Residual amounts of enzymatically active phospholipase A1 could be expressed, but the venom protein had a deleterious effect...

  12. Highly efficient and enzymatic regioselective undecylenoylation of gastrodin in 2-methyltetrahydrofuran-containing systems.

    Directory of Open Access Journals (Sweden)

    Rongling Yang

    Full Text Available Highly efficient and regioselective acylation of pharmacologically interesting gastrodin with vinyl undecylenic acid has been firstly performed through an enzymatic approach. The highest catalytic activity and regioselectivity towards the acylation of 7'-hydroxyl of gastrodin was obtained with Pseudomonas cepacia lipase. In addition, it was observed the lipase displayed higher activity in the eco-friendly solvent 2-methyltetrahydrofuran-containing systems than in other organic solvents. In the co-solvent mixture of tetrahydrofuran and 2-methyltetrahydrofuran (3/1, v/v, the reaction rate was 60.6 mM/h, substrate conversion exceeded 99%, and 7'-regioselectivity was 93%. It was also interesting that the lipase-catalyzed acylation couldn't be influenced by the benzylic alcohol in gastrodin. However, pseudomonas cepacia lipase displayed different regioselectivity towards gastrodin and arbutin.

  13. Immobilization of enzymatic extracts of Portulaca oleracea cv. roots for oxidizing aqueous bisphenol A.

    Science.gov (United States)

    Matsushima, Kazuki; Kaneda, Hirokazu; Harada, Kazuo; Matsuura, Hideyuki; Hirata, Kazumasa

    2015-05-01

    Water pollution from the release of industrial wastewater is a serious problem for almost every industry. Enzymes from portulaca, Portulaca oleracea cv., have been investigated for their ability to degrade bisphenol A (BPA), one of the well-known estrogenic pollutants. Enzymatic crude extracts from P. oleracea cv. roots were immobilized on aminopropyl-modified glass beads. They maintained BPA metabolic activity over a broad range of pH values and temperatures. The immobilized enzyme was reusable with more than 50 % of its initial activity retained after 12 batch reactions and no loss of activity after storage for 1 month at -30 °C. Thus, the immobilization of extracts from P. oleracea cv. roots is a useful method for removing BPA from industrial wastewater.

  14. Efficient Enzymatic Synthesis of Phenolic Ester by Increasing Solubility of Phenolic Acids in Ionic Liquids

    DEFF Research Database (Denmark)

    Yang, Zhiyong; Guo, Zheng; Xu, Xuebing

    Compounds from phenolic acid family are well known natural antioxidants, but the application of phenolic acids as antioxidants in industry is limited due to the relatively low solubility in oil-based media. The properties of phenolic acids can be modified through enzymatic lipophilization...... and modified phenolic acids will have amphiphilic property, therefore they can be localized at oil-water or water-oil phase where oxidation is considered to occur frequently. It had been reported that immobilized Candida Antarctica lipase B was the most effective biocatalyst for the various esterification...... reactions, and it had been widely used for esterification of various phenolic acids with fatty alcohol or triglycerides. However, the conversion of phenolic acids is low due to low solubility in hydrophobic solvents and hindrance effect of unsaturated side chain towards the enzyme. Our studies show...

  15. Optimizing the Isolation of Microfibrillated Bamboo in High Pressure Enzymatic Hydrolysis

    Directory of Open Access Journals (Sweden)

    N. A. Sri Aprilia

    2015-07-01

    Full Text Available Bleached bamboo fiber was treated with a high pressure enzymatic hydrolysis (HPEH process in order to produce microfibrillated bamboo fiber (MBF. Mixture design of experiments was utilized to determine the optimal constituents of fiber, enzymes, and water for the HPEH process on the isolation yield of the MBF. Results showed the optimal combination for the maximal yield isolation of the MBF was 1 g fiber, 1 g enzyme, and 1 L water at 90 MPa and 70 °C. The influence of the reaction time of the HPEH process (6 to 48 h was also evaluated in this study. Morphological and thermal property analyses of untreated and treated bamboo fibers revealed that the HPEH process was effective for removing non-cellulosic components from the fibers. Thus, the HPEH process is an effective method for the isolation of the MBF, with the benefits of elevated crystallinity and thermal stability.

  16. Highly efficient and enzymatic regioselective undecylenoylation of gastrodin in 2-methyltetrahydrofuran-containing systems.

    Science.gov (United States)

    Yang, Rongling; Liu, Xueming; Chen, Zhiyi; Yang, Chunying; Lin, Yaosheng; Wang, Siyuan

    2014-01-01

    Highly efficient and regioselective acylation of pharmacologically interesting gastrodin with vinyl undecylenic acid has been firstly performed through an enzymatic approach. The highest catalytic activity and regioselectivity towards the acylation of 7'-hydroxyl of gastrodin was obtained with Pseudomonas cepacia lipase. In addition, it was observed the lipase displayed higher activity in the eco-friendly solvent 2-methyltetrahydrofuran-containing systems than in other organic solvents. In the co-solvent mixture of tetrahydrofuran and 2-methyltetrahydrofuran (3/1, v/v), the reaction rate was 60.6 mM/h, substrate conversion exceeded 99%, and 7'-regioselectivity was 93%. It was also interesting that the lipase-catalyzed acylation couldn't be influenced by the benzylic alcohol in gastrodin. However, pseudomonas cepacia lipase displayed different regioselectivity towards gastrodin and arbutin.

  17. Enzymatic synthesis of arbutin undecylenic acid ester and its inhibitory effect on mushroom tyrosinase.

    Science.gov (United States)

    Tokiwa, Y; Kitagawa, M; Raku, T

    2007-03-01

    A novel tyrosinase inhibitor, an arbutin derivative having undecylenic acid at the 6-position of its glucose moiety, was enzymatically synthesized. Its inhibitory activity was studied in vitro by using catechol and phenol as substrates. The IC(50) value of the arbutin ester on tyrosinase using catechol (4 x 10(-4) M) was 1% of that when arbutin (4 x 10(-2) M) was used. Using phenol, IC(50) of the arbutin ester (3 x 10(-4) M) as substrate was 10% of that of arbutin (3 x 10(-3) M). These results suggest that the arbutin ester inhibits the latter part of the tyrosinase reaction, which consists of hydroxylation and oxidation.

  18. Quinolone resistance-associated amino acid substitutions affect enzymatic activity of Mycobacterium leprae DNA gyrase.

    Science.gov (United States)

    Yamaguchi, Tomoyuki; Yokoyama, Kazumasa; Nakajima, Chie; Suzuki, Yasuhiko

    2017-07-01

    Quinolones are important antimicrobials for treatment of leprosy, a chronic infectious disease caused by Mycobacterium leprae. Although it is well known that mutations in DNA gyrase are responsible for quinolone resistance, the effect of those mutations on the enzymatic activity is yet to be studied in depth. Hence, we conducted in vitro assays to observe supercoiling reactions of wild type and mutated M. leprae DNA gyrases. DNA gyrase with amino acid substitution Ala91Val possessed the highest activity among the mutants. DNA gyrase with Gly89Cys showed the lowest level of activity despite being found in clinical strains, but it supercoiled DNA like the wild type does if applied at a sufficient concentration. In addition, patterns of time-dependent conversion from relaxed circular DNA into supercoiled DNA by DNA gyrases with clinically unreported Asp95Gly and Asp95Asn were observed to be distinct from those by the other DNA gyrases.

  19. Efficiency of new fungal cellulase systems in boosting enzymatic degradation of barley straw lignocellulose

    DEFF Research Database (Denmark)

    Rosgaard, L.; Pedersen, S.; Meyer, Anne Boye Strunge

    2006-01-01

    This study examined the cellulytic effects on steam-pretreated barley straw of cellulose-degrading enzyme systems from the five thermophilic fungi Chaetomium thermophilum, Thielavia terrestris, Thermoascus aurantiacus, Corynascus thermophilus, and Myceliophthora thermophila and from the mesophile...... Penicillum funiculosum. The catalytic glucose release was compared after treatments with each of the crude enzyme systems when added to a benchmark blend of a commercial cellulase product, Celluclast, derived from Trichoderma reesei and a P-glucosidase, Novozym 188, from Aspergillus niger. The enzymatic...... treatments were evaluated in an experimental design template comprising a span of pH (3.5-6.5) and temperature (35-65 degrees C) reaction combinations. The addition to Celluclast + Novozym 188 of low dosages of the crude enzyme systems, corresponding to 10 wt % of the total enzyme protein load, increased...

  20. Thermal and enzymatic pretreatment of sludge containing phthalate esters prior to mesophilic anaerobic digestion

    DEFF Research Database (Denmark)

    Gavala, Hariklia N.; Yenal, U.; Ahring, Birgitte Kiær

    2004-01-01

    The present study aimed at investigating the effect of thermal pretreatment of sludge at 70degreesC on the anaerobic degradation of three commonly found phthalic acid esters (PAE): di-ethyl phthalate (DEP), di-butyl phthalate (DBP), and di-ethylhexyl phthalate (DEHP). Also, the enzymatic treatment...... at 28degreesC with a commercial lipase was studied as a way to enhance PAE removal. Pretreatment at 70degreesC of the sludge containing PAE negatively influenced the anaerobic biodegradability of phthalate esters at 37degreesC. The observed reduction of PAE biodegradation rates after the thermal...... pretreatment was found to be proportional to the PAE solubility in water: the higher the solubility, the higher the percentage of the reduction (DEP > DBP > DEHP). PAE were slowly degraded during the pretreatment at 70degreesC, yet this was probably due to physicochemical reactions than to microbial...

  1. Nuclear reactions

    International Nuclear Information System (INIS)

    Corner, J.; Richardson, K.; Fenton, N.

    1990-01-01

    Nuclear reactions' marks a new development in the study of television as an agency of public policy debate. During the Eighties, nuclear energy became a major international issue. The disasters at Three-mile Island and Chernobyl created a global anxiety about its risks and a new sensitivity to it among politicians and journalists. This book is a case-study into documentary depictions of nuclear energy in television and video programmes and into the interpretations and responses of viewers drawn from many different occupational groupings. How are the complex and specialist arguments about benefit, risk and proof conveyed through the different conventions of commentary, interview and film sequence? What symbolic associations does the visual language of television bring to portrayals of the issue? And how do viewers make sense of various and conflicting accounts, connecting what they see and hear on the screen with their pre-existing knowledge, experience and 'civic' expectations. The authors examine some of the contrasting forms and themes which have been used by programme makers to explain and persuade, and then give a sustained analysis of the nature and sources of viewers' own accounts. 'Nuclear Reactions' inquires into the public meanings surrounding energy and the environment, spelling out in its conclusion some of the implications for future media treatments of this issue. It is also a key contribution to the international literature on 'television knowledge' and the processes of active viewing. (author)

  2. Enzymatic synthesis of gold nanoflowers with trypsin

    International Nuclear Information System (INIS)

    Li Linmei; Weng Jian

    2010-01-01

    A one-step and eco-friendly approach for the room-temperature synthesis of trypsin-mediated three-dimensional (3D) gold nanoflowers (AuNFs) with high colloidal stability is demonstrated. To prepare AuNFs, ascorbic acid (AA) was quickly added into the premixed solution of HAuCl 4 and trypsin at pH = 5.0. The results show that the molar ratio and feeding order of reactant agents, pH and reaction time play important roles in the formation of NFs. The growth mechanism of AuNFs is suggested as three steps: (1) immobilization of AuCl 4 - ions with a positively charged trypsin template, (2) spontaneous reduction of AuCl 4 - ions with AA in situ and capping Au 0 by 12 cysteines of trypsin, (3) reduction of more AuCl 4 - ions on the Au nuclei formed in the initial stages and anisotropic growth into AuNFs.

  3. Pressure Modulation of the Enzymatic Activity of Phospholipase A2, A Putative Membrane-Associated Pressure Sensor.

    Science.gov (United States)

    Suladze, Saba; Cinar, Suleyman; Sperlich, Benjamin; Winter, Roland

    2015-10-07

    Phospholipases A2 (PLA2) catalyze the hydrolysis reaction of sn-2 fatty acids of membrane phospholipids and are also involved in receptor signaling and transcriptional pathways. Here, we used pressure modulation of the PLA2 activity and of the membrane's physical-chemical properties to reveal new mechanistic information about the membrane association and subsequent enzymatic reaction of PLA2. Although the effect of high hydrostatic pressure (HHP) on aqueous soluble and integral membrane proteins has been investigated to some extent, its effect on enzymatic reactions operating at the water/lipid interface has not been explored, yet. This study focuses on the effect of HHP on the structure, membrane binding and enzymatic activity of membrane-associated bee venom PLA2, covering a pressure range up to 2 kbar. To this end, high-pressure Fourier-transform infrared and high-pressure stopped-flow fluorescence spectroscopies were applied. The results show that PLA2 binding to model biomembranes is not significantly affected by pressure and occurs in at least two kinetically distinct steps. Followed by fast initial membrane association, structural reorganization of α-helical segments of PLA2 takes place at the lipid water interface. FRET-based activity measurements reveal that pressure has a marked inhibitory effect on the lipid hydrolysis rate, which decreases by 75% upon compression up to 2 kbar. Lipid hydrolysis under extreme environmental conditions, such as those encountered in the deep sea where pressures up to the kbar-level are encountered, is hence markedly affected by HHP, rendering PLA2, next to being a primary osmosensor, a good candidate for a sensitive pressure sensor in vivo.

  4. Response Surface Methodology to Optimize Enzymatic Preparation of Deapio-Platycodin D and Platycodin D from Radix Platycodi

    Directory of Open Access Journals (Sweden)

    Jian Liang

    2012-03-01

    Full Text Available In the present work, we reported the enzymatic preparation of deapio-platycodin D (dPD and platycodin D (PD optimized by response surface methodology (RSM from Radix Platycodi. During investigation of the hydrolysis of crude platycosides by various glycoside hydrolases, snailase showed a strong ability to transform deapio-platycoside E (dPE and platycoside E (PE into dPD and PD with 100% conversion. RSM was used to optimize the effects of the reaction temperature (35–45 °C, enzyme load (5–20%, and reaction time (4–24 h on the conversion process. Validation of the RSM model was verified by the good agreement between the experimental and the predicted values of dPD and PD conversion yield. The optimum preparation conditions were as follows: temperature, 43 °C; enzyme load, 15%; reaction time, 22 h. The biotransformation pathways were dPE→dPD3→dPD and PE→PD3→PD, respectively. The determined method may be highly applicable for the enzymatic preparation of dPD and PD for medicinal purposes and also for commercial use.

  5. Environmentally evaluated HPLC-ELSD method to monitor enzymatic synthesis of a non-ionic surfactant.

    Science.gov (United States)

    Gaber, Yasser; Akerman, Cecilia Orellana; Hatti-Kaul, Rajni

    2014-01-01

    N-Lauroyl-N-methylglucamide is a biodegradable surfactant derived from renewable resources. In an earlier study, we presented an enzymatic solvent-free method for synthesis of this compound. In the present report, the HPLC method developed to follow the reaction between lauric acid/methyl laurate and N-methyl glucamine (MEG) and its environmental assessment are described. Use of ultraviolet (UV) absorption or refractive index (RI) detectors did not allow the detection of N-methyl glucamine (MEG). With Evaporative light scattering detector ELSD, it was possible to apply a gradient elution, and detect MEG with a limit of detection, LOD = 0.12 μg. A good separation of the peaks: MEG, lauric acid, product (amide) and by-product (amide-ester) was achieved with the gradient program with a run time of 40 min. The setting of ELSD detector was optimized using methyl laurate as the analyte. LC-MS/MS was used to confirm the amide and amide-ester peaks. We evaluated the greenness of the developed method using the freely available software HPLC-Environmental Assessment Tool (HPLC-EAT) and the method got a scoring of 73 HPLC-EAT units, implying that the analytical procedure was more environmentally benign compared to some other methods reported in literature whose HPLC-EAT values scored up to 182. Use of ELSD detector allowed the detection and quantification of the substrates and the reaction products of enzymatic synthesis of the surfactant, N-lauroyl-N-methylglucamide. The developed HPLC method has acceptable environmental profile based on HPLC-EAT evaluation.

  6. Enzymatic generation of hydrogen peroxide shows promising antifouling effect

    DEFF Research Database (Denmark)

    Kristensen, J.B.; Olsen, Stefan Møller; Laursen, B.S.

    2010-01-01

    Proteobacteria, tested in microtiter plates. However, enzymatically produced H2O2 released from a coating did not impede biofilm formation by bacteria in natural seawater tested in a biofilm reactor. A field trial revealed a noticeable effect of the enzyme system: after immersion in the North Sea for 97 days...

  7. Reversible sol-gel-sol medium for enzymatic optical biosensors

    NARCIS (Netherlands)

    Safaryan, S.; Yakovlev, A.; Pidko, E.A.; Vinogradov, A.; Vinogradov, V.

    2017-01-01

    In this paper we for the first time report a reversible sol-gel-sol approach to obtain optical enzymatic biosensors with improved enzyme stability and good sensitivity by using desktop inkjet printing. The developed technique is based on the bio-inorganic inks allowing for a sol-gel-sol transition

  8. The properties of main oxidases associated with enzymatic ...

    African Journals Online (AJOL)

    Lenovo User

    2012-07-03

    Jul 3, 2012 ... 1College of Food Science and Engineering, Shandong Agricultural University, Taian, Shandong, 271018,. People's Republic of China. 2The Central Hospital of Taian, Taian, Shandong ... pear vinegar, preserved pear and canned pear. However, enzymatic browning during processing impairs sensory.

  9. Enzymatic Browning in Sugar Beet Leaves (Beta vulgaris L.)

    NARCIS (Netherlands)

    Vissers, Anne; Kiskini, Alexandra; Hilgers, Roelant; Marinea, Marina; Wierenga, Peter Alexander; Gruppen, Harry; Vincken, Jean Paul

    2017-01-01

    Sugar beet (Beta vulgaris L.) leaves of 8 month (8m) plants showed more enzymatic browning than those of 3 month (3m). Total phenolic content increased from 4.6 to 9.4 mg/g FW in 3m and 8m, respectively, quantitated by

  10. Malondialdehyde level and some enzymatic activities in subclinical ...

    African Journals Online (AJOL)

    The purpose of this study was to evaluate the changes occurring in milk malondialdehyde (MDA) level and some enzymatic activities as a result of subclinical mastitis (SCM) in dairy cows. A total of 124 milk samples were collected from 124 lactating cows from the same herd in the period between the 2nd week after calving ...

  11. Enzymatic biodiesel production from sludge palm oil (SPO) using ...

    African Journals Online (AJOL)

    Biodiesel is a non-toxic, renewable and environmental friendly fuel. This study involved the production of biodiesel from sludge palm oil (SPO), a low-cost waste oil via enzymatic catalysis. The enzyme catalyst was a Candida cylindracea lipase, locally-produced using palm oil mill effluent as the low cost based medium.

  12. Short-time ultrasonication treatment in enzymatic hydrolysis of biomass

    Science.gov (United States)

    Zengqian Shi; Zhiyong Cai; Siqun Wang; Qixin Zhong; Joseph J. Bozell

    2013-01-01

    To improve the conversion of enzymatic hydrolysis of biomass in an energy-efficient manner, two shorttime ultrasonication strategies were applied on six types of biomass with different structures and components. The strategies include pre-sonication before the hydrolysis and intermittent sonication during the ongoing hydrolysis. The microstructures of each type of...

  13. Enzymatic modification of phospholipids forfunctional applications and human nutrition

    DEFF Research Database (Denmark)

    Guo, Zheng; Vikbjerg, Anders / Falk; Xu, Xuebing

    2005-01-01

    analogs based on the latest understanding of pivotal role of phospholipids in manifold biological processes, exploration of remarkable application potentials of phospholipids in meliorating human health, as well as development of new chemical and biotechnological approaches applied to the modification...... design. This will of course provide fundamental bases also for the development of enzymatic technology to produce structured or modified phospholipids....

  14. Functional palm oil-based margarine by enzymatic interesterification

    DEFF Research Database (Denmark)

    Ibrahim, Nuzul Amri Bin; Xu, Xuebing

    Palm stearin, palm kernel and fish oils were blended to a various composition ratios and enzymatically interesterified by Lipozyme TL IM lipase (Thermomyces lanuginosa) using a continuous packed bed reactor. The ratio of the oils ranged from 60-90%, 10-40% and 0-10% respectively. The enzyme was a...

  15. Enzymatic activities of Azotobacter chroococcum and survival in ...

    African Journals Online (AJOL)

    Enzymatic activities of Azotobacter chroococcum and survival in schloropyrifos amended sterile and non-sterile. M Shukla, V Kumar, RL Thakur, N Narula. Abstract. No Abstract. Cameroon Journal of Experimental Biology Vol. 2 (2) 2006: pp. 88-94. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for ...

  16. ETHANOL ORGANOSOLV PRETREATMENT OF BAMBOO FOR EFFICIENT ENZYMATIC SACCHARIFICATION

    Directory of Open Access Journals (Sweden)

    Zhiqiang Li,

    2012-06-01

    Full Text Available Bamboo is a potential lignocellulosic biomass for the production of bioethanol because of its high cellulose and hemicelluloses content. In this research, ethanol organosolv pretreatment with dilute sulfuric acid as the catalyst was studied in order to enhance enzymatic saccharification of moso bamboo. The addition of 2% (w/w bamboo dilute sulfuric acid in 75% ethanol had a particularly strong effect on fractionation of bamboo. It yielded a solids fraction containing 83.4% cellulose in the treated substrate. The cellulose conversion to glucose yield reached 77.1 to 83.4% after enzymatic hydrolysis of the solids fraction for 48 h at an enzyme loading of 15 FPU cellulase/g cellulose and 30 IU β-glucosidase/g cellulose. The enzymatic hydrolysis rate was significantly accelerated as the ethanol organosolv pretreatment time increased, reaching the highest enzymatic glucose yield of 83.4% after 48 h at 50 °C. The concentrations of fermentation inhibitors such as HMF (5-hydroxy-2-methyl furfural and furfural were 0.96 g/L and 4.38 g/L in the spent liquor after the ethanol organosolv pretreatment, which were slightly lower than the concentrations quantified during H2SO4-water treatment. Spent liquor was diluted with water, and more than 87.2% of lignin in raw bamboo was recovered as ethanol organosolv lignin through the filtration process.

  17. Enzymatic cell disruption of microalgae biomass in biorefinery processes.

    Science.gov (United States)

    Demuez, Marie; Mahdy, Ahmed; Tomás-Pejó, Elia; González-Fernández, Cristina; Ballesteros, Mercedes

    2015-10-01

    When employing biotechnological processes for the procurement of biofuels and bio-products from microalgae, one of the most critical steps affecting economy and yields is the "cell disruption" stage. Currently, enzymatic cell disruption has delivered effective and cost competitive results when compared to mechanical and chemical cell disruption methods. However, the introduction of enzymes implies additional associated cost within the overall process. In order to reduce this cost, autolysis of microalgae is proposed as alternative enzymatic cell disruption method. This review aims to provide the state of the art of enzymatic cell disruption treatments employed in biorefinery processes and highlights the use of endopeptidases. During the enzymatic processes of microalgae life cycle, some lytic enzymes involved in cell division and programmed cell death have been proven useful in performing cell lysis. In this context, the role of endopeptidases is emphasized. Mirroring these natural events, an alternative cell disruption approach is proposed and described with the potential to induce the autolysis process using intrinsic cell enzymes. Integrating induced autolysis within biofuel production processes offers a promising approach to reduce overall global costs and energetic input associated with those of current cell disruption methods. A number of options for further inquiry are also discussed. © 2015 Wiley Periodicals, Inc.

  18. Wet explosion pretreatment of sugarcane bagasse for enhanced enzymatic hydrolysis

    DEFF Research Database (Denmark)

    Biswas, Rajib; Uellendahl, Hinrich; Ahring, Birgitte Kiær

    2014-01-01

    .7% of the theoretical maximum value. Pretreatment at 200 C with oxygen exhibited enhanced enzymatic efficiency but lower xylose recovery and formation of the degradation products such as acetate, furfural and HMF of 7.6, 3.3 and 1.0 g/L, respectively. In the hydrolysis, the total sugars (glucose + xylose) yielded...

  19. Clinical evaluation of chemokine and enzymatic biomarkers of Gaucher disease

    NARCIS (Netherlands)

    Deegan, Patrick B.; Moran, Mary Teresa; McFarlane, Ian; Schofield, J. Paul; Boot, Rolf G.; Aerts, Johannes M. F. G.; Cox, Timothy M.

    2005-01-01

    Purpose: Gaucher disease is an exemplary orphan disorder. Enzyme replacement therapy with imiglucerase is effective, but very expensive. To improve the assessment of severity of disease and responses to this costly treatment, we have evaluated several enzymatic biomarkers and a newly-described

  20. Recombinant EXLX1 from Bacillus subtilis for enhancing enzymatic ...

    African Journals Online (AJOL)

    AJL

    2012-06-21

    Jun 21, 2012 ... enhancing enzymatic hydrolysis of corn stover with low cellulase loadings. Zhang Yan1, He Ming-Xiong2,3*, Wu Bo1, ... University, Chengdu 610064, China. 2Biogas Institute of Ministry of Agriculture, Biomass Energy Technology Research Centre, Section 4-13, Renming Nanlu,. Chengdu 610041, China.

  1. Effects of thermo-chemical pretreatment plus microbial fermentation and enzymatic hydrolysis on saccharification and lignocellulose degradation of corn straw.

    Science.gov (United States)

    Wang, Ping; Chang, Juan; Yin, Qingqiang; Wang, Erzhu; Zhu, Qun; Song, Andong; Lu, Fushan

    2015-10-01

    In order to increase corn straw degradation, the straw was kept in the combined solution of 15% (w/w) lime supernatant and 2% (w/w) sodium hydroxide with liquid-to-solid ratio of 13:1 (mL/g) at 83.92°C for 6h; and then added with 3% (v/v) H2O2 for reaction at 50°C for 2h; finally cellulase (32.3 FPU/g dry matter) and xylanase (550 U/g dry matter) was added to keep at 50°C for 48 h. The maximal reducing sugars yield (348.77 mg/g) was increased by 126.42% (Pcellulose, hemicellulose and lignin in pretreated corn straw with enzymatic hydrolysis were increased by 40.08%, 45.71% and 52.01%, compared with the native corn straw with enzymatic hydrolysis (P<0.05). The following study indicated that the combined microbial fermentation and enzymatic hydrolysis could further increase straw degradation and reducing sugar yield (442.85 mg/g, P<0.05). Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Spallation reactions; Reactions de spallation

    Energy Technology Data Exchange (ETDEWEB)

    Cugon, J.

    1996-12-31

    Spallation reactions dominate the interactions of hadrons with nuclei in the GeV range (from {approx} 0.1 to {approx} 10 GeV). They correspond to a sometimes important ejection of light particles leaving most of the time a residue of mass commensurate with the target mass. The main features of the experimental data are briefly reviewed. The most successful theoretical model, namely the intranuclear cascade + evaporation model, is presented. Its physical content, results and possible improvements are critically discussed. Alternative approaches are shortly reviewed. (author). 84 refs.

  3. Asymmetric Chemoenzymatic Reductive Acylation of Ketones by a Combined Iron-Catalyzed Hydrogenation-Racemization and Enzymatic Resolution Cascade

    KAUST Repository

    El-Sepelgy, Osama

    2017-02-28

    A general and practical process for the conversion of prochiral ketones into the corresponding chiral acetates has been realized. An iron carbonyl complex is reported to catalyze the hydrogenation-dehydrogenation-hydrogenation of prochiral ketones. By merging the iron-catalyzed redox reactions with enantioselective enzymatic acylations a wide range of benzylic, aliphatic and (hetero)aromatic ketones, as well as diketones, were reductively acylated. The corresponding products were isolated with high yields and enantioselectivities. The use of an iron catalyst together with molecular hydrogen as the hydrogen donor and readily available ethyl acetate as acyl donor make this cascade process highly interesting in terms of both economic value and environmental credentials.

  4. High-performance liquid chromatography analysis methods developed for quantifying enzymatic esterification of flavonoids in ionic liquids

    DEFF Research Database (Denmark)

    Lue, Bena-Marie; Guo, Zheng; Xu, X.B.

    2008-01-01

    Methods using reversed-phase high-performance liquid chromatography (RP-HPLC) with ELSD were investigated to quantify enzymatic reactions of flavonoids with fatty acids in the presence of diverse room temperature ionic liquids (RTILs). A buffered salt (preferably triethylamine-acetate) was found...... essential for separation of flavonoids from strongly polar RTILs, whereby RTILs were generally visible as two major peaks identified based on an ion-pairing/exchanging hypothesis. C8 and C12 stationary phases were optimal while mobile phase pH (3-7) had only a minor influence on separation. The method...

  5. Determination of myoglobin based on its enzymatic activity by stopped-flow spectrophotometry

    Science.gov (United States)

    Zheng, Qi; Liu, Zhihong; Cai, Ruxiu

    2005-04-01

    A new method has been developed for the determination of myoglobin (Mb) based on its enzymatic activity for the oxidation of o-phenylenediamine (OPDA) with hydrogen peroxide. Stopped-flow spectrophotometry was used to study the kinetic behavior of the oxidation reaction. The catalytic activity of Mb was compared to other three kinds of catalyst. The time dependent absorbance of the reaction product, 2,3-diamimophenazine (DAPN), at a wavelength of 426 nm was recorded. The initial reaction rate obtained at 40 °C was found to be proportional to the concentration of Mb in the range of 1.0 × 10 -6 to 4.0 × 10 -9 mol L -1. The detection limit of Mb was found to be 9.93 × 10 -10 mol L -1. The relative standard deviations were within 5% for the determination of different concentrations of Mb. Excess of bovine serum albumin (BSA), Ca(II), Mg(II), Cu(II), glucose, caffeine, lactose and uric acid did not interfere.

  6. Human Milk Fat Substitute Produced by Enzymatic Interesterification of Vegetable Oil Blend

    Directory of Open Access Journals (Sweden)

    Semra Turan

    2007-01-01

    Full Text Available Palm oil, palm kernel oil, olive oil, sunflower oil, and marine oil blend, formulated in the mass ratio of 4.0:3.5:1.0:1.5:0.2, was subjected to interesterification catalyzed by lipase from Thermomyces lanuginosa (Lipozyme® TL IM for obtaining a product that contains similar triacylglycerol (TAG structure to that of human milk fat (HMF. Reactions were carried out in a double jacketed glass vessel equipped with magnetic stirrer at 60 °C for 2, 4, 6, 8, 12 and 24 h. The blend was analyzed for fatty acid composition of both total fatty acids and those at the sn-2 position after pancreatic lipase hydrolysis. After interesterification, TAGs were purified by thin layer chromatography and TAG species were determined according to the carbon number (CN by high-temperature gas chromatography. Enzymatic interesterification generated significant differences for all TAG species from CN30 to CN54. Concentrations of some TAG species (CN30, 32, 34, 36, 38, 50, 52 and 54 decreased, while some (CN40 to 48 increased after 24 h. TAG species with higher CN reached maximum levels at the end of 6 h of reaction time. The predominant TAGs of the reaction product after 24 h were CN46, 48, 50, 52 and 54 with ratios of 13.8, 18.2, 13.9, 17.8, and 12.1 %, respectively. These TAG species contain mainly 1,3-diunsaturated-2-saturated structure, like HMF.

  7. Optimization of enzymatic esterification of dihydrocaffeic acid with hexanol in ionic liquid using response surface methodology.

    Science.gov (United States)

    Gholivand, Somayeh; Lasekan, Ola; Tan, Chin Ping; Abas, Faridah; Wei, Leong Sze

    2017-05-26

    Developing an efficient lipophilization reaction system for phenolic derivatives could enhance their applications in food processing. Low solubility of phenolic acids reduces the efficiency of phenolic derivatives in most benign enzyme solvents. The conversion of phenolic acids through esterification alters their solubility and enhances their use as food antioxidant additives as well as their application in cosmetics. This study has shown that lipase-catalyzed esterification of dihydrocaffeic acid with hexanol in ionic liquid (1-butyl-3-methylimidazoliumbis (trifluoromethylsulfonyl) imide) was the best approach for esterification reaction. In order to achieve the maximum yield, the process was optimized by response surface methodology (RSM) based on a five-level and four independent variables such as: dosage of enzyme; hexanol/dihydrocaffeic acid mole ratio; temperature and reaction time. The optimum esterification condition (Y = 84.4%) was predicted to be obtained at temperature of 39.4 °C, time of 77.5 h dosage of enzyme at 41.6% and hexanol/dihydrocaffeic acid mole ratio of 2.1. Finally, this study has produced an efficient enzymatic esterification method for the preparation of hexyl dihydrocaffeate in vitro using a lipase in an ionic liquid system. Concentration of hexanol was the most significant (p < 0.05) independent variable that influenced the yield of hexyl dihydrocaffeate. Graphical abstract Synthesis of different Hexyl dihydrocaffeates in ionic liquid.

  8. An Integrated Process of Ionic Liquid Pretreatment and Enzymatic Hydrolysis of Lignocellulosic Biomass with Immobilised Cellulase

    Directory of Open Access Journals (Sweden)

    Mihaela Ungurean

    2014-08-01

    Full Text Available An integrated process of lignocellulosic biomass conversion was set up involving pretreatment by an ionic liquid (IL and hydrolysis of cellulose using cellulase immobilised by the sol-gel method, with recovery and reuse of both the IL and biocatalyst. As all investigated ILs, regardless of the nature of the anion and the cation, led to the loss of at least 50% of the hydrolytic activity of cellulase, the preferred solution involved reprecipitation of cellulose and lignin after the pretreatment, instead of performing the enzymatic hydrolysis in the same reaction system. The cellulose recovered after pretreatment with 1-ethyl-3-methylimidazolium acetate ([Emim][Ac] and dimethylsulfoxide (DMSO (1:1 ratio, v/v was hydrolysed with almost double yield after 8 h of reaction time with the immobilised cellulase, compared to the reference microcrystalline cellulose. The dissolution capacity of the pretreatment mixture was maintained at satisfactory level during five reuse cycles. The immobilised cellulase was recycled in nine reaction cycles, preserving about 30% of the initial activity.

  9. A coupled CFD and two-phase substrate kinetic model for enzymatic hydrolysis of lignocellulose

    Science.gov (United States)

    Danes, Nicholas; Sitaraman, Hariswaran; Stickel, Jonathan; Sprague, Michael

    2017-11-01

    Cost-effective production of fuels from lignocellulosic biomass is an important subject of research in order to meet the world's current and future energy demands. Enzymatic hydrolysis is one of the several steps in the biochemical conversion of biomass into fuels. This process involves the interplay of non-Newtonian fluid dynamics that happen over tens of seconds coupled with chemical reactions that happen over several hours. In this work, we present a coupled CFD-reaction model for conversion of cellulose to sugars in a benchtop mixer reactor. A subcycling approach is used to circumvent the large time scale disparity between fluid dynamics and reactions. We will present a validation study of our simulations with experiments for well-mixed and stratified reactor scenarios along with predictions for conversion rates and product concentrations at varying impeller speeds and in scaled-up reactors. This work is funded by the Bioenergy Technology Office of DOE and the NSF's Enriched Doctoral Training program (DMS-1551229).

  10. The enzymatic and antioxidative stress response of Lemna minor to copper and a chloroacetamide herbicide.

    Science.gov (United States)

    Obermeier, Michael; Schröder, Christian A; Helmreich, Brigitte; Schröder, Peter

    2015-12-01

    Lemna minor L., a widely used model plant for toxicity tests has raised interest for its application to phytoremediation due to its rapid growth and ubiquitous occurrence. In rural areas, the pollution of water bodies with heavy metals and agrochemicals poses a problem to surface water quality. Among problematic compounds, heavy metals (copper) and pesticides are frequently found in water bodies. To establish duckweed as a potential plant for phytoremediation, enzymatic and antioxidative stress responses of Lemna minor during exposure to copper and a chloroacetamide herbicide were investigated in laboratory studies. The present study aimed at evaluating growth and the antioxidative and glutathione-dependent enzyme activity of Lemna plants and its performance in a scenario for phytoremediation of copper and a chloroacetamide herbicide. Lemna minor was grown in Steinberg medium under controlled conditions. Plants were treated with CuSO4 (ion conc. 50 and 100 μg/L) and pethoxamide (1.25 and 2.5 μg/L). Measurements following published methods focused on plant growth, oxidative stress, and basic detoxification enzymes. Duckweed proved to survive treatment with the respective concentrations of both pollutants very well. Its growth was inhibited scarcely, and no visible symptoms occurred. On the cellular basis, accumulation of O2(-) and H2O2 were detected, as well as stress reactions of antioxidative enzymes. Duckweed detoxification potential for organic pollutants was high and increased significantly with incubation. Pethoxamide was found to be conjugated with glutathione. Copper was accumulated in the fronds at high levels, and transient oxidative defense reactions were triggered. This work confirms the significance of L. minor for the removal of copper from water and the conjugation of the selective herbicide pethoxamide. Both organic and inorganic xenobiotics induced different trends of enzymatic and antioxidative stress response. The strong increase of stress

  11. Physico-chemical, spectroscopical and thermal characterization of bio diesel obtained by enzymatic route as a tool to select the most efficient immobilized lipase

    International Nuclear Information System (INIS)

    Silva, G.A.M.; Ros, P.C.M. da; Souza, L.T.A.; Costa, A.P.O.; Castro, H.F. de

    2012-01-01

    Two microbial lipases from Burkholderia cepacia and Pseudomonas fluorescens were evaluated as catalysts for the enzymatic transesterification of beef tallow with ethanol and the most efficient lipase source was selected by taking into account the properties of the product to be used as fuel. Both lipases were immobilized on an epoxy silica-polyvinyl alcohol composite by covalent immobilization and used to perform the reactions under the following operational conditions: beef tallow-to-ethanol molar ratio of 1:9, 45 degree C and 400 units of enzymatic activity per gram of fat. Products, characterized using Fourier Transform Infrared spectroscopy (FTIR), viscosimetry, thermogravimetry and 1 H NMR spectroscopy, suggested that the bio diesel sample obtained in the reaction catalyzed by Burkholderia cepacia lipase has the best set of properties for fuel usage. (author)

  12. Physico-chemical, spectroscopical and thermal characterization of bio diesel obtained by enzymatic route as a tool to select the most efficient immobilized lipase

    Energy Technology Data Exchange (ETDEWEB)

    Silva, G.A.M.; Ros, P.C.M. da; Souza, L.T.A.; Costa, A.P.O.; Castro, H.F. de, E-mail: heizir@dequi.eel.usp.br [Engineering School of Lorena. University of Sao Paulo (EEL/USP), Lorena, SP (Brazil)

    2012-01-15

    Two microbial lipases from Burkholderia cepacia and Pseudomonas fluorescens were evaluated as catalysts for the enzymatic transesterification of beef tallow with ethanol and the most efficient lipase source was selected by taking into account the properties of the product to be used as fuel. Both lipases were immobilized on an epoxy silica-polyvinyl alcohol composite by covalent immobilization and used to perform the reactions under the following operational conditions: beef tallow-to-ethanol molar ratio of 1:9, 45 degree C and 400 units of enzymatic activity per gram of fat. Products, characterized using Fourier Transform Infrared spectroscopy (FTIR), viscosimetry, thermogravimetry and {sup 1}H NMR spectroscopy, suggested that the bio diesel sample obtained in the reaction catalyzed by Burkholderia cepacia lipase has the best set of properties for fuel usage. (author)

  13. Dynamic Simulation, Sensitivity and Uncertainty Analysis of a Demonstration Scale Lignocellulosic Enzymatic Hydrolysis Process

    DEFF Research Database (Denmark)

    Prunescu, Remus Mihail; Sin, Gürkan

    2014-01-01

    This study presents the uncertainty and sensitivity analysis of a lignocellulosic enzymatic hydrolysis model considering both model and feed parameters as sources of uncertainty. The dynamic model is parametrized for accommodating various types of biomass, and different enzymatic complexes...

  14. Enzymatic detection of formalin-fixed museum specimens for DNA analysis and enzymatic maceration of formalin-fixed specimens

    DEFF Research Database (Denmark)

    Sørensen, Margrethe; Redsted Rasmussen, Arne; Simonsen, Kim Pilkjær

    2016-01-01

    % ethanol. The method was subsequently tested on wild-living preserved specimens and an archived specimen. The protease enzyme used was SavinaseH 16 L, Type EX from Novozymes A/S. The enzymatic screening test demands only simple laboratory equipment. The method is useful for natural history collections...

  15. Capillary gel electrophoresis-coupled aptamer enzymatic cleavage protection strategy for the simultaneous detection of multiple small analytes.

    Science.gov (United States)

    Perrier, Sandrine; Zhu, Zhenyu; Fiore, Emmanuelle; Ravelet, Corinne; Guieu, Valérie; Peyrin, Eric

    2014-05-06

    This novel, multi small-analyte sensing strategy is the result of combining the target-induced aptamer enzymatic protection approach with the CGE-LIF (capillary gel electrophoresis with laser-induced fluorescence) technique. The implemented assay principle is based on an analysis of the phosphodiesterase I (PDE I)-mediated size variation of a fluorescein-labeled aptamer (FApt), the enzyme catalyzing the removal of nucleotides from DNA in the 3' to 5' direction. In the absence of the target, the unfolded aptamer was enzymatically cleaved into short DNA fragments. Upon target binding, the DNA substrate was partially protected against enzymatic hydrolysis. The amount of bound aptamer remaining after the exonuclease reaction was proportional to the concentration of the target. The CGE technique, which was used to determine the separation of FApt species from DNA digested products, permitted the quantification of adenosine (A), ochratoxin A (O), and tyrosinamide (T) under the same optimized enzymatic conditions. This assay strategy was subsequently applied to the simultaneous detection of A, O, and T in a single capillary under buffered conditions using corresponding FApt probes of different lengths (23, 36, and 49 nucleotides, respectively). Additionally, the detection of these three small molecules was successfully achieved in a complex medium (diluted, heat-treated human serum) showing a good recovery. It is worth noting that the multiplexed analysis was accomplished for targets with different charge states by using aptamers possessing various structural features. This sensing platform constitutes a rationalized and reliable approach with an expanded potential for a high-throughput determination of small analytes in a single capillary.

  16. Synthesis of base-modified 2'-deoxyribonucleoside triphosphates and their use in enzymatic synthesis of modified DNA for applications in bioanalysis and chemical biology.

    Science.gov (United States)

    Hocek, Michal

    2014-11-07

    The synthesis of 2'-deoxyribonucleoside triphosphates (dNTPs) either by classical triphosphorylation of nucleosides or by aqueous cross-coupling reactions of halogenated dNTPs is discussed. Different enzymatic methods for synthesis of modified oligonucleotides and DNA by polymerase incorporation of modified nucleotides are summarized, and the applications in redox or fluorescent labeling, as well as in bioconjugations and modulation of interactions of DNA with proteins, are outlined.

  17. Evaluation of physical structural features on influencing enzymatic hydrolysis efficiency of micronized wood

    Science.gov (United States)

    Jinxue Jiang; Jinwu Wang; Xiao Zhang; Michael Wolcott

    2016-01-01

    Enzymatic hydrolysis of lignocellulosic biomass is highly dependent on the changes in structural features after pretreatment. Mechanical milling pretreatment is an effective approach to alter the physical structure of biomass and thus improve enzymatic hydrolysis. This study examined the influence of structural characteristics on the enzymatic hydrolysis of micronized...

  18. Lignin from hydrothermally pretreated grass biomass retards enzymatic cellulose degradation by acting as a physical barrier rather than by inducing nonproductive adsorption of enzymes.

    Science.gov (United States)

    Djajadi, Demi T; Jensen, Mads M; Oliveira, Marlene; Jensen, Anders; Thygesen, Lisbeth G; Pinelo, Manuel; Glasius, Marianne; Jørgensen, Henning; Meyer, Anne S

    2018-01-01

    Lignin is known to hinder efficient enzymatic conversion of lignocellulose in biorefining processes. In particular, nonproductive adsorption of cellulases onto lignin is considered a key mechanism to explain how lignin retards enzymatic cellulose conversion in extended reactions. Lignin-rich residues (LRRs) were prepared via extensive enzymatic cellulose degradation of corn stover ( Zea mays subsp. mays L.), Miscanthus  ×  giganteus stalks (MS) and wheat straw ( Triticum aestivum L.) (WS) samples that each had been hydrothermally pretreated at three severity factors (log R 0 ) of 3.65, 3.83 and 3.97. The LRRs had different residual carbohydrate levels-the highest in MS; the lowest in WS. The residual carbohydrate was not traceable at the surface of the LRRs particles by ATR-FTIR analysis. The chemical properties of the lignin in the LRRs varied across the three types of biomass, but monolignols composition was not affected by the severity factor. When pure cellulose was added to a mixture of LRRs and a commercial cellulolytic enzyme preparation, the rate and extent of glucose release were unaffected by the presence of LRRs regardless of biomass type and severity factor, despite adsorption of the enzymes to the LRRs. Since the surface of the LRRs particles were covered by lignin, the data suggest that the retardation of enzymatic cellulose degradation during extended reaction on lignocellulosic substrates is due to physical blockage of the access of enzymes to the cellulose caused by the gradual accumulation of lignin at the surface of the biomass particles rather than by nonproductive enzyme adsorption. The study suggests that lignin from hydrothermally pretreated grass biomass retards enzymatic cellulose degradation by acting as a physical barrier blocking the access of enzymes to cellulose rather than by inducing retardation through nonproductive adsorption of enzymes.

  19. Chain reaction

    International Nuclear Information System (INIS)

    Balogh, Brian.

    1991-01-01

    Chain Reaction is a work of recent American political history. It seeks to explain how and why America came to depend so heavily on its experts after World War II, how those experts translated that authority into political clout, and why that authority and political discretion declined in the 1970s. The author's research into the internal memoranda of the Atomic Energy Commission substantiates his argument in historical detail. It was not the ravages of American anti-intellectualism, as so many scholars have argued, that brought the experts back down to earth. Rather, their decline can be traced to the very roots of their success after World War II. The need to over-state anticipated results in order to garner public support, incessant professional and bureaucratic specialization, and the sheer proliferation of expertise pushed arcane and insulated debates between experts into public forums at the same time that a broad cross section of political participants found it easier to gain access to their own expertise. These tendencies ultimately undermined the political influence of all experts. (author)

  20. CuInSe2 nano-crystallite reaction kinetics using solid state reaction from Cu2Se and In2Se3 powders

    International Nuclear Information System (INIS)

    Hsiang, Hsing-I; Lu, Li-Hsin; Chang, Yu-Lun; Ray, Dahtong; Yen, Fu-Su

    2011-01-01

    Highlights: → CuInSe 2 phase increased gradually accompanied with a decrease in γ-In 2 Se 3 and no intermediate phase during calcination. → CuInSe 2 formation from Cu 2 Se and In 2 Se 3 powders follows a one-dimensional diffusion-controlled reaction with apparent activation energy of about 122.5 kJ/mol. → The solid reaction kinetics may be dominated by the diffusion of In 3+ ions. - Abstract: The reaction mechanism and CuInSe 2 formation kinetics using a solid state reaction from Cu 2 Se and In 2 Se 3 powders synthesized using a heating up process were investigated using X-ray diffractomy (XRD) and transmission electron microscopy (TEM). It was observed that the CuInSe 2 phase increased gradually, accompanied with a decrease in γ-In 2 Se 3 with no intermediate phase as the calcination temperature and soaking time were increased. The reaction kinetics was analyzed using the Avrami and polynomial kinetic model, suggesting that CuInSe 2 formation from Cu 2 Se and In 2 Se 3 powders follows a diffusion-controlled reaction with an apparent activation energy of about 122.5-182.3 kJ/mol. Cu 2 Se and In 2 Se 3 phases react and directly transform into CIS without the occurrence of any intermediate phase and the size of the newly formed CuInSe 2 crystallites was close to that of the Cu 2 Se reactant particle based on the TEM results, which indicated that the solid reaction kinetics may be dominated by the diffusion of In 3+ ions.