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  • 1
    Electronic Resource
    Electronic Resource
    The effect of protein impurities on lysozyme crystal growth (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 776-785 
    Details
    ISSN: 0006-3592
    Keywords: protein crystallization ; impurities ; lysozyme ; purification ; solubility ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: While bulk crystallization from impure solutions is used industrially as a purification step for a wide variety of materials, it is a technique that has rarely been used for proteins. Proteins have a reputation for being difficult to crystallize and high purity of the initial crystallization solution is considered paramount for success in the crystallization. Although little is written on the purifying capability of protein crystallization or of the effect of impurities on the various aspects of the crystallization process, recent published reports show that crystallization shows promise and feasibility as a purification technique for proteins.To further examine the issue of purity in macromolecule crystallization, this study investigates the effect of the protein impurities, avidin, ovalbumin, and conalbumin at concentrations up to 50%, on the solubility, crystal face growth rates, and crystal purity of the protein lysozyme. Solubility was measured in batch experiments while a computer controlled video microscope system was used to measure the {110} and {101} lysozyme crystal face growth rates. While little effect was observed on solubility and high crystal purity was obtained ( 〉 99.99%), the effect of the impurities on the face growth rates varied from no effect to a significant face specific effect leading to growth cessation, a phenomenon that is frequently observed in protein crystal growth. The results shed interesting light on the effect of protein impurities on protein crystal growth and strengthen the feasibility of using crystallization as a unit operation for protein purification. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:776-785, 1998.
    Additional Material: 10 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis of protein-containing polymers in organic solvents (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 10-17 
    Details
    ISSN: 0006-3592
    Keywords: proteins ; enzymes ; immobilization ; biopolymers ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Subtilisin has been modified with polyethylene glycol (PEG) monomethacrylate (MW 8000) by reductive alkylation, and incorporated into polymethyl methacrylate durring free-radical initiated polymerization. The activity and stability of the PEG-modified enzymes have been determined in aqueous buffer and organic solvents. The Km and Vmax values for unmodified, singly and doubly modified subtilisin were compared in these environments, and the half-lives of both modified enzymes were remarkably high (up to 2 months). The protein-containing polymer was analyzed for activity and polymer properties, and our results indicate that active subtilisin can be incorporated into polymethyl methacrylate during polymerization in organic solvents while retaining its activity and stability. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260450103
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  • 3
    Electronic Resource
    Electronic Resource
    A comparison of lipase-catalyzed ester hydrolysis in reverse micelles, organic solvents, and biphasic systems (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 60-70 
    Details
    ISSN: 0006-3592
    Keywords: enzymes ; organic solvents ; lipase ; reverse micelles ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The performance of lipases from Candida rugosa and wheat germ have been investigated in three reaction media using three acetate hydrolyses as model reactions (ethyl acetate, allyl acetate, and prenyl acetate). The effect of substrate properties and water content were studied for each system (organic solvent, biphasic system, and reverse micelles). Not unexpectedly, the effect of water content is distinct for each system, and the optimal water content for enzyme activity is not always the same as that for productivity. A theoretical model has been used to simulate and predict enzyme performance in reverse micelles, and a proposed partitioning model for biphasic systems agrees well with experimental results. While the highest activities observed were in the micellar system, productivity in microemulsions is limited by low enzyme concentrations. Biphasic systems, however, support relatively good activity and productivity. The addition of water to dry organic solvents, combined with the dispersion of lyophilized enzyme powders in the solvent, resulted in significant enzyme aggregation, which not surprisingly limits the applicability of the “anhydrous” enzyme suspension approach. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260470108
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  • 4
    Electronic Resource
    Electronic Resource
    Protein purification by bulk crystallization: The recovery of ovalbumin (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 316-323 
    Details
    ISSN: 0006-3592
    Keywords: ovalbumin ; bulk crystallization ; crystalgrowth rate ; nucleation ; purification ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Crystallization is used industrially for the recovery and purification of many inorganic and organic materials. However, very little is reported on the application of bulk crystallization for proteins. In this work, ovalbumin was selected as a model protein to investigate the feasibility of using bulk crystallization for the recovery and purification of proteins. A stirred 1-L seeded batch crystallizer was used to obtain the crystal growth kinetics of ovalbumin in ammonium sulfate solutions at 30°C. The width of the metastable region, in which crystal growth can occur without any nucleation, is equivalent to a relative supersaturation of about 20. The bulk crystallizations were undertaken within this range (using initial relative supersaturations less than 10) and nucleation was not observed. The ovalbumin concentration in solution was measured by UV absorbance and checked by crystal content measurement. Crystal size distributions were measured both by using a Malvern Mastersizer and by counting crystals through a microscope. The crystal growth rate was found to have a second-order dependence upon the ovalbumin supersaturation. While there is no discernible effect of ammonium sulfate concentration at pH 4.90, there is a slight effect at higher pH values. Overall the effect of ammonium sulfate concentration is small compared to the effect of pH, for which there is a 10-fold increase in the growth rate constant, kGσ over the range pH 4.6-5.4. To demonstrate the degree of purification which can be achieved by bulk crystallization, ovalbumin was crystallized from a solution containing conalbumin (80,000 Da) and lysozyme (14, 600 Da). After one crystallization and a crystal wash, ovalbumin crystals were produced with a protein purity greater than 99%. No contamination by the other proteins was observed when using overloaded sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) stained with Coomassie blue stain and only trace amounts of lysozyme were observed using a silver stain. The presence of these other proteins in solution did not effect the crystal growth rate constant, kGσ. The study demonstrates the feasibility of using bulk crystallization for the recovery and purification of ovalbumin. It should be readily applicable to other protein systems. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480404
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  • 5
    Electronic Resource
    Electronic Resource
    The role of hydration in enzyme activity and stability: 1. Water adsorption by alcohol dehydrogenase in a continuous gas phase reactor (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 700-708 
    Details
    ISSN: 0006-3592
    Keywords: alcohol dehydrogenase ; enzyme ; water sorption isoterm ; gas phase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The adsorption of water by alcohol dehydrogenase from baker's yeast (YADH) has been measured in a continuous-flow gas reactor at varying temperatures. Adsorption isotherms in the presence of gaseous organic substrates are compared to those from organic-free gas mixtures. Almost no effect of the hydrophobic molecule on total water adsorption was observed. A rarely mentioned multilayer isotherm model from the 1930s, the Huttig's isotherm, has been found to fit the experimental data with extremely good accuracy. The model enables the calculation of both the heat of adsorption of water to the enzyme and the total amount of water necessary for monolayer coverage. The heat of adsorption of water in the first layer is approximately -16 kcal/mol. This tight binding of water, which is much higher than the heat of condensation of pure water, helps to explain the kinetic properties of YADH-catalyzed reactions on vapor phase substrates. While the monolayer coverage is temperature independent, the enzyme demonstrates hysteresis when transitioning between adsorption and desorption. The hysteresis observed in water sorption studies may also explain previously reported properties of the enzyme. © 1996 John Wiley & Sons, Inc.
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  • 6
    Electronic Resource
    Electronic Resource
    The role of hydration in enzyme activity and stability: 2. Alcohol dehydrogenase activity and stability in a continuous gas phase reactor (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 709-716 
    Details
    ISSN: 0006-3592
    Keywords: enzymes ; gas phase ; alcohol dehydrogenase ; hydration ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The degree of enzyme hydration is the one of the most important factors which can affect enzyme activity and stability in water-limited environments. Alcohol dehydrogenase from baker's yeast (YADH) has been used as a model enzyme to study the effects of hydration on activity, stability, and cofactor stability with gas phase substrates. In all cases, the enzyme is essentially inactive until a temperature-independent degree of surface coverage by water molecules has been reached. The critical water content corresponds to 40-50% of a single monolayer. Careful control of the degree of hydration, by adjustments to gas humidity and temperature, enables the enzyme to be stabilized for periods exceeding 1 month, whereas in water the half-life of the enzyme is 30 min. The reaction with gas phase substrates follows a pseudo-first-order mechanism with an activation energy of 7.5 ± kcal/mol, which is almost half of that in aqueous solution. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Covalent binding of a nerve agent hydrolyzing enzyme within polyurethane foams (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 450-457 
    Details
    ISSN: 0006-3592
    Keywords: enzymes ; immobilization ; phosphotriesterase ; polyurethane foam ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A phosphotriesterase preparation, extracted from Escherichia coli DH5α cells, was immobilized within a polyurethane foam matrix during polymer synthesis. The enzyme-foam interaction was shown to be covalent and analysis of the hydrolysis of paraoxon in aqueous solution demonstrated that more than 50% of the initial enzyme specific activity was retained after immobilization in the foam. Factors affecting the rate of paraoxon degradation include foam hydrophobicity, the degree of mixing applied to initiate polymerization, and foam pretreatment prior to use in substrate hydrolysis. The storage stability of the foam is significant, with phosphotriesterase-foam activity profiles exhibiting a three month half-life. Foams are currently being developed for biocatalytic air filtering, in which gaseous substrates will be simultaneously adsorbed and degraded by the immobilized enzyme system. © 1996 John Wiley & Sons, Inc.
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  • 8
    Electronic Resource
    Electronic Resource
    Dramatically stabilized phosphotriesterase - polymers for nerve agent degradation (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 54 (1997), S. 105-114 
    Details
    ISSN: 0006-3592
    Keywords: enzymes ; phosphotriesterase ; immobilization ; polyurethane foam ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Phosphotriesterase (EC 3.1.8.1) was immobilized within a polyurethane foam matrix during polymer synthesis using a prepolymer synthesis strategy. In addition to retaining greater than 50% of the enzyme specific activity, numerous benefits were incurred upon immobilization. Orders of magnitude increases in storage and thermal stability (net stabilization energy = 12.5 kJ/mol) were observed without the need for enzyme premodification. The immobilized enzyme system was protease resistant and seemed to display no adverse effects from immobilization, such as an alteration of enzyme function. The organic solvent, dimethyl sulfoxide, also exhibited a stabilizing effect on phosphotriesterase enzyme systems over a range of intermediate concentrations. We attribute these effects in part to direct interaction between the aprotic solvent and metal containing residues present at the enzyme's active site. Our data demonstrate that just 2.5 kg of immobilized enzyme may be sufficient to degrade 30,000 tons of nerve agent in just 1 year. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 105-114, 1997.
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  • 9
    Electronic Resource
    Electronic Resource
    Biocatalytic polyester synthesis: Analysis of the evolution of molecular weight and end group functionality (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 227-239 
    Details
    ISSN: 0006-3592
    Keywords: enzymes ; polymer ; polyester ; MALDI-TOF ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The enzymatic synthesis of polyesters from activated diesters and diols has been investigated. Differences between enzymatic synthesis and traditional chemical condensation processes are discussed. The disappearance of monomers during the initial phase of reaction indicates that enzyme has a higher specificity for transesterification of ester-terminated oligomers. During the intermediate phase, enzymatic polymerization involves a competition between diol and enzyme-bound water for the nucleophilic attack of the acyl enzyme intermediate. Competition between enzymatic transesterification and hydrolysis at different stages of polymerization in nonaqueous media is responsible for termination of polyesters with acid end-groups and also for limiting the polymer molecular weight. The resulting oligoester consists of chains that are either terminated with  -  OH groups and/or  -  COOH groups. We have used Matrix Assisted Laser Desorption/Ionization  -  Time of Flight Mass spectroscopy (MALDI-TOF) along with colorimetric titration techniques to determine the acidity of enzyme-synthesized polyesters. This paper addresses how the enzymatic polymerization proceeds, and compares our results to the growing literature in this field. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 227-239, 1997.
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  • 10
    Electronic Resource
    Electronic Resource
    Rapid biocatalytic polytransesterification: Reaction kinetics in an exothermic reaction (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 428-437 
    Details
    ISSN: 0006-3592
    Keywords: enzymes ; polyesters ; bulk polymerization ; calorimetry ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biocatalytic polytransesterification at high concentrations of monomers proceeds rapidly and is accompanied by an increase in the temperature of the reaction mixture due to liberation of heat of reaction during the initial phase. We have used principles of reaction calorimetry to monitor the kinetics of polymerization during this initial phase, thus relating the temperature to the extent of polymerization. Rate of polymerization increases with the concentration of monomers. This is also reflected by the increase in the temperature of the reaction mixture. Using time-temperature-conversion contours, a differential method of kinetic analysis was used to calculate the energy of activation (∼15.1 Kcal/mol). © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:428-437, 1998.
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