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  • ASTROPHYSICS  (6,235)
  • Biochemistry and Biotechnology  (3,182)
  • 1990-1994  (9,417)
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  • 1
    Electronic Resource
    Electronic Resource
    The effect of electrochemical regeneration upon the enzymatic catalysis of a thermodynamically unfavorable reaction (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 788-796 
    Details
    ISSN: 0006-3592
    Keywords: enzymatic electrocatalysis ; NADH ; cofactor regeneration ; product inhibition ; organic synthesis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The association between enzymatic and electrochemical reactions, enzymatic electrocatalysis, had proven to be a very powerful tooth in both analytical and synthetic fields. However, most of the combinations studied have involved enzymatic catalysis of irreversible or quasi-irreversible reaction. In the present work, we have investigated the possibility of applying enzymatic electrocatalysis to a case where the electrochemical reaction drives a thermodynamically unfavorable reversible reaction. Such thermodynamically unfavorable reactions include most of the oxidations catalyzed by dehydrogenases. Yeast alcohol dehydrogenase (E.C. 1.1.1.1) was chosen as a model enzyme because the oxidation of ethanol is thermodynamically very unfavorable and because its kinetics are well known. The electrochemical reaction was the oxidation of NADH which is particularly attractive as a method of cofactor regeneration. Both the electrochemical and enzymatic reactions occur in the same batch reactor in such a way that electrical energy is the only external driving force. Two cases were experimentally and theoretically developed with the enzyme either in solution or immobilized onto the electrode's surface. In both cases, the electrochemical reaction could drive the enzymatic reaction by NADH consumption in solution or directly in the enzyme's microenvironment. However even for a high efficiency of NADH consumption, the rate of enzymatic catalysis was limited by product (acetaldedehyde) inhibition. Extending this observation to the subject of organic synthesis catalyzed by dehydrogenases, we concluded that thermodynamically unfavorable reaction and can only be used in a process if efficient NAD regeneration and product elimination are simultaneously carried out within the reactor.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380713
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  • 2
    Electronic Resource
    Electronic Resource
    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380801
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  • 3
    Electronic Resource
    Electronic Resource
    Production of monoclonal antibody using free-suspended and immobilized hybridoma cells: Effect of serum (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 821-830 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma ; immobilization ; serum ; flow cytometry ; antibody productivity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of serum on cell growth and monoclonal antibody (MAb) productivity was studied in a repeated fedbatch mode using both free-suspended and immobilized S3H5/γ2bA2 hybridoma cells. In the suspension culture, serum influenced the cell growth rate but not the specific MAb productivity. The average specific growth rate of the suspension culture in medium containing 10% serum was approximately 0.99 ± 0.12 day-1 (±standard deviation), while that in medium containing 1% serum was approximately 0.73 ± 0.12 day-1. The specific MAb productivity was almost constant at 3.69 ± 0.57 μg/106 cells/day irrespective of serum concentration reached a maximum at ca. 1.8 × 106 cells/mL of medium in 10% serum medium, and the cell concentration was gradually reduced to 1%. The specific MAb productivity of the immobilized cells was more than three times higher than that of the free-suspended cells. The amount of serum in the medium did not influence the specific MAb production rate of the immobilized cells. The maintenance of high cell concentration and the enhanced specific MAb productivity of the immobilized cell culture resulted in a higher volumetric MAb productivity. In addition, MAb yield in the immobilized cell culture with medium containing 1% serum was 2.2 mg/mL of serum, which was approximately three times higher than that in the suspension culture.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380804
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  • 4
    Electronic Resource
    Electronic Resource
    Optimization of a two-stage recombinant fermentation process: The dilution rate effect (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 831-837 
    Details
    ISSN: 0006-3592
    Keywords: fermentation ; Escherichia coli ; recombinant fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of dilution rates on the performance of a two-stage fermentation system for a recombinant Escherichia coli culture were studied. Dilution rate determines the apparent or averaged specific growth rate of a heterogeneous population of cells in the recombinant culture. The specific growht rate affects the genetic parameters involved in product formation in the second stage, such as plasmid stability, plasmid content, and specific gene expression rate. Kinetic models and correlations were developed for these parameters based on experimental data. Simulations of plasmid stability in the first stage showed that for longer fermentation periods, plasmid stability is better at higher dilution rates. However, the plasmid content is lower at these dilution rates. The optimal apparent specific growth rate for maximum productivity in the second stage was determined using two methods: (1) direct search for a constant specific growth rate, and (2) dynamic optimization using the maximum principle for a time-dependent specific growth rate profile. The results of the calculations showed that the optimum constant apparent specific growth rate for maximum over-all productivity is 0.40 h-1. This coincides with the optimal specific growht rate for maximum plasmid content in the expressed stage. A 3.5% increase in overall productivity can be obtained by using a linear time dependent apparent specific growth rate control, μ2(t) = 0.0007t, in the course of the fermentation time.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380805
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  • 5
    Electronic Resource
    Electronic Resource
    Reaction kinetics in biofilms (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 877-882 
    Details
    ISSN: 0006-3592
    Keywords: microtechnique ; microprobe ; biofilm ; dissolved oxygen concentration ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel in situ microtechnique allows evaluating parameters of diffusion-controlled reactions in biofilms. A microprobe, 15 μm in diameter, was used to simultaneously measure the dissolved oxygen concentration and the optical density at different depths in a submerged biofilm. Based on the results, the biofilm diffusion coefficient for dissolved oxygen, Df the dissolved oxygen flux through the biofilm surface, J02, and the half velocity coefficient, Ks, have been calculated.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380809
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  • 6
    Electronic Resource
    Electronic Resource
    Fluorescence modeling in a multicomponent system (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 907-922 
    Details
    ISSN: 0006-3592
    Keywords: fluorescene monitoring ; inner-filter effect ; biosensor ; tryptophan ; tyrosine ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An extensive fluorescence database for binary tyrosinetryptophan mixtures utilizing 280 nm excitation was collected. The database spanned three orders of magnitude (10-6M-10-3M) and covered all compositions within this range. A generalized model for describing the multicomponent fluorescence signals as a function of emission wavelength, excitation wavelength, and sample composition was derived. A geometric integral that contained all the geometric factors affecting fluorescence was introduced; thus the model was applicable to various configurations, including the three used in this study: an NADH probe, a backscatter laser-induced fluorescence setup, and a commercial spectroflurometer. A correction factor was proposed that allowed linearization of the fluorescence signals with respect to fluorophore concentrations. The effect of the water Raman on fluorescence spectra was also modeled. The model contains only two wavelength-dependent parameters for each of the components present in a sample, one specifying absorption of the excitation energy and the other specifying the species' fluorescence tendency. These wavelength-dependent parameters were correlated with polynomials. The average prediction error at each wavelength was 10-20%, a major portion of which was attributed to experimental uncertainties.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380812
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  • 7
    Electronic Resource
    Electronic Resource
    Xylanase production by Aspergillus awamori. Development of a medium and optimization of the fermentation parameters for the production of extracellular xylanase and β-xylosidase while maintaining low protease production (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 883-890 
    Details
    ISSN: 0006-3592
    Keywords: Aspergillus awamori ; low protease production ; dinitrosalicylic method ; xylanase ; β-xylosidase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A growth medium was developed for maximal production in batch culture of extracellular xylanase and β-xylosidase by Aspergillus awamori CMI 142717 and a mutant (AANTG 43) derived from the wild-type strain. The optimum pH for the production of xylanase and β-xylosidase was 4.0. The best temperature of xylanase production was 30°C; 35°C was optimal for β-xylosidase. Protease production was never completely suppressed under any of the conditions tested. However, protease titre was 3.5-fold less than the control in medium in which proteose peptone and yeast extract were omitted: the level of xylanase was not affected (8.6 U mL-1) but β-xylosidase titre was increased 4.7-fold to 1.5 U mL-1. When corn steep liquor was used as the sole nitrogen source, xylanse and β-xylosidase titres were further increased by 1.5- and 1.9-fold, respectively. Of the carbon sources investigated, ball-milled oat straw or oat spelt xylan produced the highest titres of xylanse and β-xylosidase. None of the soluble carbon sources investigated produced the high titres of xylanase or β-xylosidase induced by either oat straw for xylanse and β-xylosidase was 2% and the optimum spore inoculum was between 106 and 107 spores/mL-1 final concentration. The level of xylanse activity obtained in the culture filtrates of the mutant was a remarkable 820 U mL-1 when the reducing sugar released was measured by the dinitrosalicylic acid method. This enzyme titre would appear to be the highest reported so far. The xylanases system contained the correct balance of enzymes to effect extensive hydrolysis of oat spelt xylan. The protease titre was very low.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380810
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  • 8
    Electronic Resource
    Electronic Resource
    Kinetic analysis of cephalosporin biosynthesis in Streptomyces clavuligerus (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 941-947 
    Details
    ISSN: 0006-3592
    Keywords: Streptomyces clavuligerus ; cephalosporin ; rate-limiting enzyme ; kinetic model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A kinetic model describing the cephalosporin biosynthesis in Streptomyces clavuligerus was developed. Using previously reported kinetic data of biosynthetic enzymes, we examined the kinetics of cephalosporin production. The predicted time profile of the specific production rate during a batch culture parallels that of experimental observation. Sensitivity analysis reveals that δ-(L-α-aminoadipyl)-L-cysteinyl-D-valine (ACV) synthetase is the rate-limiting enzyme. The effect of amplifying ACV synthetase on the specific production rate was analyzed theoretically. Increasing ACV synthetase enhances the production rate initially until ACV synthetase enhances the production rate initially until deacetocycephalosporin C hydroxylase becomes rate-limiting. Such kinetic analysis can provide a rational basis for modifying the biosynthetic machinery of cephalosporin through gene cloning.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380815
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  • 9
    Electronic Resource
    Electronic Resource
    Application of lipase to concentrate the docosahexaenoic acid (DHA) fraction of fish oil (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 956-959 
    Details
    ISSN: 0006-3592
    Keywords: Rhizopus niveus ; DHA ; omega-3 fatty acid ; specification ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A commercial lipase preparation from Rhizopus niveus was used to concentrate the omega-3 fatty acid, docosahexaenoic acid (DHA) component in fish oil. The DHA content of cod-liver oil was 9.64% (w/w) of total fatty acids. Enzymatic digestion conditions were established which produced a DHA content in the monoglycerides fraction of 29.17% (w/w) of total fatty acid, triglyceride, and diglyceride components were 5.72, 9.95, and 15316%, respectively.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380818
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  • 10
    Electronic Resource
    Electronic Resource
    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380901
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