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  • Biochemistry and Biotechnology  (11)
  • 1995-1999
  • 1990-1994  (11)
  • 1980-1984
  • 1970-1974
  • 1960-1964
  • 1940-1944
  • 1994  (11)
  • 1
    Electronic Resource
    Electronic Resource
    Lipase catalyzed esterification of glycidol in nonaqueous solvents: Solvent effects on enzymatic activity (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 119-124 
    Details
    ISSN: 0006-3592
    Keywords: glycidol ; enatioselective esterification ; lipase ; nonaqueous solvents ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We studied the effect of organic solvents on the kinetics of porcine pancreatic lipase (pp) for the resolution of racemic glycidol through esterification with butyric acid. We quantified ppl hydration by measuring water sorption isotherms for the enzyme in the solvents/mixtures tested. The determination of initial rates as a function of enzyme hydration revealed that the enzyme exhibits maximum apparent activity in the solvents/mixtures at the same water content (9% to 11% w/w) within the associated experimental error. The maximum initial rates are different in all the media and correlate well with the logarithm of the molar solubility of water in the media, higher initial rates being observed in the solvents/mixtures with lower water solubilities. The data for the mixtures indicate that ppl apparent activity responds to bulk property of the solvent. Measurements of enzyme particle sizes in five of the solvents, as function of enzyme hydration, revealed that mean particle sizes increased with enzyme hydration in all the solvents, differences between solvents being more pronounced at enzyme hydration levels close to 10%. At this hydration level, solvents having a higher water content lead to lower reaction rates; these are the solvents where the mean enzyme particle sizes are greater. Calculation of the observable modulus indicates there are no internal diffusion limitations. The observed correlation between changes in initial rates and changes in external surface area of the enzyme particles suggests that interfacial activation of ppl is only effective at the external surface of the particles. Data obtained for the mixtures indicate that ppl enantioselectivity depends on specific solvent-enzyme interactions. We make reference to ppl hydration and activity in supercritical carbon dioxide. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440117
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  • 2
    Electronic Resource
    Electronic Resource
    The influence of polyalcohols and carbohydrates on the thermostability of α-amylase (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 107-114 
    Details
    ISSN: 0006-3592
    Keywords: polyols and carbohydrates ; protein thermostability ; heat inactivation kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of polyhydric alcohols and carbohydrates on the thermostability, i.e., the heat inactivation kinetics, of Bacillus licheniformis α-amylase was studied in the temperature range 96° to 130°C. High concentrations (from 9 to 60 weight percent) of glycerol, sorbitol, mannitol, sucrose, or starch can markedly decrease the inactivation rate constant, k, and in the studied cases, this stabilizing effect grows stronger with increasing additive concentration. Statements about stabilization should, however, be specified carefully with respect to temperature, because EA is mostly altered likewise. For dissolved enzyme EA was almost always decreased in the presence of polyol or carbohydrate, whereas for immobilized enzyme it was augmented in each studied instance. The inactivation of dissolved enzyme can, in all the studied cases, be adequately described as a firstorder process. Immobilized enzyme, however, shows biphasic then first-order inactivation kinetics, depending on the additive concentration and temperature. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260430202
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of biofilm structures on oxygen distribution and mass transport (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 1131-1138 
    Details
    ISSN: 0006-3592
    Keywords: confocal microscopy ; microelectrodes ; cell clusters ; pores ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Aerobic biofilms were found to have a complex structure consisting of microbial cell clusters (discrete aggregates of densely packed cells) and interstitial voids. The oxygen distribution was strongly correlated with these strutures. The voids facilitated oxygen transport from the bulk liquid through the biofilm, supplying approximately 50% of the total oxygen consumed by the cells. The mass transport rate from the bulk liquid is influenced by the biofilm structure; the observed exchange surface of the biofilm is twice that calculated for a simple planar geometry. The oxygen diffusion occurred in the direction normal to the cluster surfaces, the horizontal and vertical components of the oxygen gradients were of equal importance. Consequently, for calculations of mass transfer rates a three-dimensional model is necessary. These findings imply that to accurately describe biofilm activity, the relation between the arrangement of structural components and mass transfer must be undrstood. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260431118
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  • 4
    Electronic Resource
    Electronic Resource
    Co-immobilized Nitrosomonas europaea and Nitrobacter agilis cells: validation of a dynamic model for simultaneous substrate conversion and growth in κ-carrageenan gel beads (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 1153-1163 
    Details
    ISSN: 0006-3592
    Keywords: dynamic modeling ; nitrification ; biomass profile ; immobilized cells ; Nitrobacter ; Nitrosomonas ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A dynamic model for two microbial species immobilized in a gel matrix is presented and validated with experiments. The model characterizes the nitrification of ammonia with Nitrosomonas europaea and Nitrobacter agilis co-immobilized in K-carrageenan gel beads. The model consists of kinetic equations for the microorganisms and mass transfer equations for the substrates and products inside and outside the gel beads. The model predicts reactor bulk concentrations together with the substrate consumption rate, product formation, and biomass growth inside the gel beads as a function of time. A 50-day experiment with immobilized cells in a 3.3-dm3 air-lift loop reactor was carried out to validate the model. The parameter values for the model were obtained from literature and separate experiments. The experimentally determined reactor bulk concentrations and the biomass distribution of the two microorganisms in the gel beads were well predicted by the model. A sensitivity analysis of the model for the given initial values indicated the most relevant parameters to be the maximum specific growth rate of the microorganisms, the diffusion coefficient of oxygen, and the radius of the beads. The dynamic model provides a useful tool for further study and possible control of the nitrification process. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260431121
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  • 5
    Electronic Resource
    Electronic Resource
    A method for simultaneous determination of solubility and transfer coefficient of oxygen in aqueous media using off-gas mass spectrometry (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 149-154 
    Details
    ISSN: 0006-3592
    Keywords: mass spectrometry ; oxygen-transfer coefficient ; solubility of oxygen ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A static method was developed that simultaneously determined the solubility of oxygen and the oxygen-transfer coefficient in a stirred bioreactor. It was based on the static method developed by van Sonsbeek et al. to determine the ka in a liquid-impelled loop reactor. Only physical properties of the liquid were used to determine both parameters using a mass spectrometer. Data about the solubility of oxygen in water are available from the literature. Therefore, the solubility of oxygen in water was used to compare our data with published data. Furthermore, the solubility of oxygen in trypticase soy broth was compared to literature data. No significant deviations between our data and literature data could be observed. Our static method and the commonly applied dynamic method to determine the oxygen-transfer coefficient yielded similar results. The effect of temperature on the oxygen-transfer coefficient could be expressed as the activation energy needed for the transition of oxygen from the gas to the water phase. This was verified using the Arrhenius equation. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260430207
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  • 6
    Electronic Resource
    Electronic Resource
    Ethene removal from a synthetic waste gas using a dry biobed (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 642-648 
    Details
    ISSN: 0006-3592
    Keywords: waste gas treatment ; ethene ; volatile organic compounds ; granular activated carbon ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A packed granular activated carbon (GAC) biobed, inoculated with the ethane-degrading strain Mycobacterium E3, was used to study ethene removal from a synthetic waste gas. Ethene, for which the dimensionless partition coefficient for an air-water system at 20°C is about 7.6, was used as a model compound for poorly water soluble gaseous pollutants. In a first mode or operation, the GAC biobed was sprinkled intermittently and the waste gas influent was continuously pre-humidified, establishing relatively moist conditions (water content 〉40% to 45%). A volumetric ethene removal rate of 0.382 kg COD · m-3 · d-1 (0.112 kg ethene · m-3 · d-1) was obtained for an influent concentration of 125 ppm, a superficial waste gas velocity of 3.6E-3 m · s-1 and a pseudo residence time of 45 s. However, in the second mode of operation, omitting the pre-humidification of the waste gas influent and establishing a “dry” biobed (water content 〈40% to 45%), and thus obtaining better mass transfer to the biofilm, the ethene removal could be doubled for otherwise comparable operating parameters. Furthermore, under decreased wetting and for the given experimental conditions (influent concentration 125 to 816 ppm, waste gas superficial velocity 3.0E-3 m ·s-1, pseudo waste gas residence time 43 s), the ethene removal was not limited by mass transfer of ethene through the water layer covering the biofilm. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440511
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  • 7
    Electronic Resource
    Electronic Resource
    DSC and protein-based time-temperature integrators: Case study of α-amylase stabilized by polyols and/or sugar (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 859-865 
    Details
    ISSN: 0006-3592
    Keywords: differential scanning calorimetry ; kinetics ; time-temperature integrators ; protein thermostability ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Differential scanning calorimetry (DSC) was used as a tool for rapid assay of the thermostability of two Bacillus sp. α-amylases and horseradish peroxidase as a function of the concentration of glycerol, sorbitol, and sucrose. In this screening study, the DSC peak temperature proved to be a good measure of protein thermostability. By means of isothermal heating experiments, the kinetics of heat decay of B. amyloliquefaciens α-amylase were studied by following the course of the DSC peak area (heat exchange (ΔH/wt)) as a function of time. The high stability of this enzyme in the presence of polyolic alcohols or carbohydrates allowed working at temperatures as high as 127°C. The results of this study can have particular relevance with regard to research on and development of protein-based time-temperature integrators (TTls) for evaluating heat pasteurization or sterilization treatments of foods or pharmaceutical products. The use of the DSC peak area (ΔH.wt) as TTI-response was validated in experiments with a time-variable temperature profile. Finally, it was shown how the results of such non-isothermal experiments can even be used for (re-) estimation of the protein decay kinetic parameters (k, EA). © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440712
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  • 8
    Electronic Resource
    Electronic Resource
    Liquid flow in heterogeneous biofilms (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 636-641 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; hydrodynamics ; mass transport ; particle tracking ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Liquid flow was studied in aerobic biofilms, consisting of microbial cell clusters (discrete aggregates of densely packed cells) and interstitial voids. Fluorescein microinjection was used as a qualitative technique to determine the presence of flow in cell clusters and voids. Flow velocity profiles were determined by tracking fluorescent latex spheres using confocal microscopy. Liquid was flowing through the voids and was stagnant in the cell clusters. Consequently, in voids both diffusion and convection may contribute to mass transfer, whereas in cell clusters diffusion is the dominant factor. The flow velocity in the biofilm depended on the average flow velocity of the bulk liquid. The velocity profiles in biofilms were linear and the velocity was zero at the substratum surface. The velocity gradients within biofilms were 50% of that near walls without biofilm coverage. The influence of the biofilm roughness on the flow velocity profiles was similar to that caused by rigid roughness elements. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440510
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  • 9
    Electronic Resource
    Electronic Resource
    Characterization of plasma membrane redox activity from ehrlich cells (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 12 (1994), S. 149-152 
    Details
    ISSN: 0263-6484
    Keywords: Ferricyanide reductase ; glycosidases ; phospholipases ; tumour ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Ferricyanide reductase activity of plasma membranes isolated from Ehrlich ascites tumour cells was very sensitive to trypsin treatment. The decreases of activity observed after treatment with different glycosidases suggests that ferricyanide reductase is a glycoprotein. The opposite effects of phospholipase A2 and phospholipase C on the redox activity indicate that the phospholipidic environment plays an important role in the function of ferricyanide reductase. Sodium ions at millimolar concentrations, and some divalent cations at micromolar concentrations (Ca2+, Mg2+, Sr2+, and Mn2+) behaved as stimulators of ferricyanide reductase activity.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cbf.290120211
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  • 10
    Electronic Resource
    Electronic Resource
    Analysis of the proteins of aging Caenorhabditis elegans by high resolution two-dimensional gel electrophoresis (1994)
    Weinheim : Wiley-Blackwell
    Electrophoresis 15 (1994), S. 289-296 
    Details
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The metabolic rate decreases dramatically as a function of age in the nematode worm Caenorhabditis elegans. Superoxide anion production, which is tightly linked to oxygen consumption, and thus to metabolic rate, drops to a 20-fold lower level in 10-day-old, senescent worms, as compared to 4-day-old young adults. In a long-lived mutant strain of the same species metabolic activity is much better preserved. High resolution two-dimensional gel electrophoresis was employed to study alterations in the protein profile, correlating with changes of metabolic activity. Surprisingly, few proteins show age- or age- and strain-specific variations of spot intensity. The abundance of the huge majority of proteins displayed on these gels remains unaltered, irrespective of age and strain differences. These results imply that there are no major age-related alterations of proteins due to faulty protein synthesis or free radical attack, and that age-related changes in the rate of protein synthesis and breakdown must be strictly coordinated throughout the aging process.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150150149
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