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  • 1
    Electronic Resource
    Electronic Resource
    Effect of hydration on the morphology of enzyme powder (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 1171-1175 
    Details
    ISSN: 0006-3592
    Keywords: enzymes ; organic solvents ; hydration ; environmental electron microscopy ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We report the first direct images of the hydration of protein powders. Using an environmental scanning electron microscope (ESEM) we have taken a series of micrographs of a region of the enzyme (subtilisin) power whilst hydrating the sample. In addition, the sample has been viewed during exposure to toluene vapors. The ESEM is a remarkable new instrument that will have wide applicability in imaging of biological materials in their native environments.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260391114
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  • 2
    Electronic Resource
    Electronic Resource
    The effects of surface adsorption on the thermal stability of proteins (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 8-15 
    Details
    ISSN: 0006-3592
    Keywords: adsorption ; silica ; proteins ; lysozyme ; surface polarity ; protein stability ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of surface adsorption on the structure and stability of proteins is a matter of increasing interest in biotechnology. Therefore, we have examined the effect of adsorption to silica on the thermal stability of 7 proteins employing differential scanning calorimetry (DSC) and front surface fluorescence (FSF) spectroscopy. In general, it was found that surface adsorption decreased the thermal stability of the bound protein. Using lysozyme for further studies, DSC, FSF, and FTIR spectroscopies, as well as enzymatic activity measurements, were used to explore the effect of decreasing surface apolarity on stability. It was observed that increasing surface apolarity produced decreasing stability and increasing structural alteration of the adsorbed protein.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260400103
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  • 3
    Electronic Resource
    Electronic Resource
    Determination of equilibrium and individual rate constants for subtilisin-catalyzed transesterification in anhydrous environments (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 1069-1077 
    Details
    ISSN: 0006-3592
    Keywords: enzymes ; organic solvents ; mechanism ; subtilisin ; microscopic rate constants ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We report here the first determinations of individual rate constants and equilibrium constants for enzymatic reactions in essentially anhydrous organic solvents. Using the added nucleophile method we have measured the effect of changing solvent on the binding and catalytic steps for subtilisin-catalyzed transesterification of N-protected amino acid esters. The detailed information generated indicates that once the substrate has bound to the enzyme, the catalytic machinery can work at rates equivalent to those in water. The decreased overall rates for subtilisin suspended in anhydrous solvents are merely the result of extremely high values for Ks, in most cases, coupled with low concentrations of nucleophile (∼1.0M in organic solvents, and 55M in water). The method described, which is generally applicable, and straightforward experimentally, will, we believe, enable a clearer understanding of how changing solvent can predictably affect the activity and specificity of the enzyme. © 1992 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260400910
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  • 4
    Electronic Resource
    Electronic Resource
    Biocatalytic synthesis of acrylates in organic solvents and supercritical fluids: I. Optimization of enzyme environment (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 158-166 
    Details
    ISSN: 0006-3592
    Keywords: enzymes ; organic solvents ; supercritical fluids ; acrylates ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biocatalytic transesterification of methylmethacrylate is possible in many different solvents. The reaction rate is readily controlled by variation in solvent physical properties. The reaction proceeds better in hydrophobic solvents, and activity can be restored in hydrophilic solvents by the addition of water. We have now demonstrated that supercritical carbon dioxide is not a good solvent for the reaction between 2-ethlhexanol and methylmethacrylate. It apperars that the supercritical carbon dioxide may either alter the pH of the microaqueous environment associated with the protein or reversibly form covalent complexes with free amine groups on the surface of the enzyme. Although supercritical carbon dioxide is a poor solvent for acrylate transesterification, many other supercritical fluids (ethane, ethylene, sulfur hexafluoride, and fluoroform) are better than most conventional solvents. In supercritical ethane it is possible to control the activity of the enzyme by changing pressure, and the enzyme appears to follow Michaelis-Menten Kinetics. We find that sulfur hexafluoride, the first anhydrous inorganic solvent in which biocatalytic activity has been reported, is a better solvent than any conventional or supercritical organic fluid tested.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260400122
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  • 5
    Electronic Resource
    Electronic Resource
    Protein extraction and activity in reverse micelles of a nonionic detergent (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 806-814 
    Details
    ISSN: 0006-3592
    Keywords: enzymes ; proteins ; organic solvents ; microemulsions ; nonionic surfactants ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We describe, for the first time, the ability of a polyoxyethylene sorbitan trioleate-isopropanol microemulsion in hexane to solubilize pure proteins. The dependences of cytochrome c extraction and buffer solubilization by the reverse micellar system on ionic strength of the aqueous phase, detergent concentration, and cosurfactant concentration result in increased extraction. In addition, subtilisin (a serine protease) is shown to be active in this microemulsion. Further the activity of the enzyme can be regulated by the water content of the micelles, enabling control of enzyme activity by “solvent engineering.”
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390803
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  • 6
    Electronic Resource
    Electronic Resource
    The influence of vessel height and top-section size on the hydrodynamic characteristics of airlift fermentors (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 69-76 
    Details
    ISSN: 0006-3592
    Keywords: airlift ; fermentor, airlift ; hydrodynamics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fermentations of the yeast Saccharomyces cerevisiae were carried out in a 90 to 250-L working volume concentric tube airlift fermentor. Measurements of liquid circulation velocity, gas hold-up, and liquid mixing were made under varying conditions of gas flowrate, vessel height, and top-section size. Both liquid circulation velocity and mixing time increased with vessel height. Liquid velocity varied approximately in proportion to the square root of column height, supporting a theoretically based relationship. The effect of vessel height on gas hold-up was negligible. The height of the top-section had a significant effect on liquid mixing. Mixing time decreased with increasing size of the top-section up to a critical height. As the top-section was expanded beyond this height, little improvement in mixing was seen. This indicated the presence of a two-zone flow pattern in the top-section. Liquid velocity and gas hold-up were essentially independent of top-section height. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260430110
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  • 7
    Electronic Resource
    Electronic Resource
    Two-Step biocatalytic conversion of an ester to an aldehyde in reverse micelles (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 232-241 
    Details
    ISSN: 0006-3592
    Keywords: enzymes ; organic solvents ; alcohol dehydrogenase ; reverse micelles ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Lipases from Candida cyclindracea (L-1754) and wheat germ (L-3001) have been used to hydrolyze esters to their corresponding alcohols and acids in reverse micelles. Alcohol dehydrogenase from baker's yeast (YADH) was subsequently used to reduce the alcohol products to aldehydes. Cofactor recycling in the redox reaction was achieved using a sacrificial cosubstrate, as described previously. Four surfactants (sodium dioctylsulfosuccinate, Nonidet P-40 with Triton X-35, polyoxyethylene, 10-cetyl-ether, polyoxyethylene sorbitan trioleate) were employed to determine the effect of amphiphile on ester hydrolysis and redox reaction rates separately. The effect of type of organic solvent, W0 [(water]/[surfactant)], and substrate concentration on separte enzyme activity were also investigated. A brief investigation of a single phase, two-step reaction catalyzed by the combination of lipase and YADH in reverse micelles is also reported. The activities of the enzymes are significantly different when used together instead of independently. © 1994 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260430307
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  • 8
    Electronic Resource
    Electronic Resource
    High pressure EPR studies of protein mobility in reversed micelles (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 342-348 
    Details
    ISSN: 0006-3592
    Keywords: organic solvents ; reversed micelles ; protein mobility ; EPR spectra of enzymes ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We have investigated the effect of pressure on structural properties of subtilisin solubilized in reversed micelles of Tween-85/isopropanol in hexane. Electron paramagnetic resonance (EPR) spectra of spin-labeled enzyme indicate a reduction in spin-label mobility when the enzyme is transferred from aqueous solution to the microemulsion. One explanation for the spectral broadening is a change in the protein's active-site conformation and/or dynamics. However, over a W0 range of 80 to 180, EPR spectroscopy could detect no change in the enzyme's environment, conformation, or molecular dynamics. The EPR spectra also contained a contribution from free spin label located in an environment with a polarity roughly between that of propanol and bulk water. No changes in the polarity surrounding the free spin label nor in the enzyme's structural properties were evident at pressures up to 10,000 psi. Previous work has demonstrated that pressure can be used to manipulate the size of some reversed micelles, and the EPR data indicated that for this system such pressure tuning of micellar properties will not adversely affect the structure of solubilized enzyme. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260430412
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  • 9
    Electronic Resource
    Electronic Resource
    Transfer vectors for maximal expression of passenger genes in the Bombyx mori nuclear polyhedrosis virus expression system (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1293-1300 
    Details
    ISSN: 0006-3592
    Keywords: baculoviruses ; transfer vectors ; expression vectors ; chloramphenicol acetyl transferase ; metallothionein ; deletion mutagenesis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A series of Bombyx mori nuclear polyhedrosis virus (Bm-NPV) transfer vectors has been developed containing various lengths of the polyhedrin promoter, including sequences 3′ of the initiation codon. The ATG initiation codon was mutated in some of these vectors to allow for the production of authentic nonfusion proteins. The ability of the various polyhedrin promoter constructs to direct expression of foreign gene sequences was assessed using two test genes, chloramphenicol acetyl transferase (cat), and human metallothionein II. Accumulation of cat mRNA and nonfused protein was low when only polyhedrin promoter sequences to -8 (relative to the translational start site of polyhedrin mRNA) were included in the transfer vector, but cat expression was comparable with that of the wild-type polyhedrin gene when promoter sequences to +5 were present. Further addition of polyhedrin gene sequences to +26 or +94 resulted in no further increase in expression. Similar results were obtained for expression of human metallothionein II, where constructs encoding polyhedrin-metallothionein fusion proteins containing polyhedrin sequences to at least +5 resulted in high levels of mRNA and protein accumulation. The expression vectors containing the +5, +26, or +94 BmNPV polyhedrin promoter can thus be used to direct maximal levels of production of nonfused proteins (when the polyedrin ATG has been mutated) or of fusion proteins, depending on which is more suitable for a particular application. These new vectors are a useful addition to those presently available and should increase the utility of the BmNPV expression system for large-scale protein production. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260421106
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  • 10
    Electronic Resource
    Electronic Resource
    Biodegradation of pesticides in nonionic water-in-oil microemulsions of tween 85: Relationship between micelle structure and activity (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 946-959 
    Details
    ISSN: 0006-3592
    Keywords: enzymes ; phosphotriesterase ; reversed micelles ; microemulsions ; nonionic surfactants ; organophosphorus hydrolase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Water-in-oil microemulsion systems have been studied in recent years for a number of applications in protein separation and enzymology. Although it is well established that reversed micelle systems provide an excellent medium for nonaqueous biocatalytic studies, there is still much speculation as to the interaction of the enzyme with the surfactant interface. Polyoxyethylene sorbitan trioleate (Tween 85) is a nonionic surfactant which has some interesting properties for microemulsion formation and protein solubilization. In conjunction with a separate article describing the structural features of Tween 85 reversed micelles in hexane with isopropanol as a cosurfactant, this work describes the activity of an enzyme, organophosphorus hydrolase, for degrading organophosphorus pesticides in this microemulsion system. Ternary phase diagrams were constructed to outline the phase boundaries at different temperatures and isopropanol concentrations, which elucidate the role of the cosurfactant alcohol, as well as some features of micelle structure. Kinetic and stability studies with organophosphorus hydrolase show the effect of enzyme partitioning between the micelle surfactant layer and aqueous core. © 1994 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260431008
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