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  • 1
    Electronic Resource
    Electronic Resource
    Studies on the production of (S)-(+)-solketal (2,2-dimethyl-1,3-dioxolane-4-methanol) by enantioselective oxidation of racemic solketal with Comamonas testosteroni (1994)
    Springer
    Applied microbiology and biotechnology 42 (1994), S. 8-15 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract All strains of Comamonas testosteroni investigated here, produced quinohaemoprotein ethanol dehydrogenase (QH-EDH) when grown on ethanol or butanol, but one strain of C. acidovorans and of C. terrigena did not. Hybridization experiments showed that the gene for QH-EDH is absent in the latter two strains. Induction and properties of the QH-EDHs seem to be similar: all C. testosteroni strains produced the enzyme in its apo-form [without pyrroloquinoline quinone (PQQ)] and the levels were higher at growth at low temperature; preference for the R-enentiomer and similar selectivity was shown in the oxidation of solketal (2,2-dimethyl-1,3-dioxolane-4-methanol) by cells (supplemented with PQQ); the fragment of the qhedh gene gave high hybridization with the DNA of the C. testosteroni strains. Experiments with C. testosteroni LMD 26.36 revealed that the organism is well suited for production of (S)-solketal: it shows an adequate enantioselectivity (E value of 49) for the oxidation of racemic solketal; the conversion rate of (R)-solketal is only 3.5 times lower than that of ethanol; the optimal pH for conversion (7.6) is in a region where solketal has sufficient chemical stability; separation of the remaining (S)-solketal from the acid formed is simple; induction of QH-EDH, the sole enzyme responsible for the oxidation of (R)-solketal, occurs during growth on ethanol or butanol so that the presence of solketal (inhibitory for growth) is not required; production of active cells and the conversion step can be integrated into one process, provided that PQQ and solketal addition occur at the appropriate moment; the conversion seems environmentally feasible. However, since high concentrations of solketal inhibit respiration via QH-EDH, further investigations on the mechanism of inhibition and the stability of the enzyme might be rewarding as it could lead to application of higher substrate concentrations with consequently lower down-stream processing costs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00170216
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Studies on the production of (S)-(+)-solketal (2,2-dimethyl-1,3-dioxolane-4-methanol) by enantioselective oxidation of racemic solketal with Comamonas testosteroni (1994)
    Springer
    Applied microbiology and biotechnology 42 (1994), S. 8-15 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract All strains of Comamonas testosteroni investigated here, produced quinohaemoprotein ethanol dehydrogenase (QH-EDH) when grown on ethanol or butanol, but one strain of C. acidovorans and of C. terrigena did not. Hybridization experiments showed that the gene for QH-EDH is absent in the latter two strains. Induction and properties of the QH-EDHs seem to be similar: all C. testosteroni strains produced the enzyme in its apo-form [without pyrroloquinoline quinone (PQQ)] and the levels were higher at growth at low temperature; preference for the R–enantiomer and similar selectivity was shown in the oxidation of solketal (2,2-dimethyl-1,3-dioxolane-4-methanol) by cells (supplemented with PQQ); the fragment of the qhedh gene gave high hybridization with the DNA of the C. testosteroni strains. Experiments with C. testosteroni LMD 26.36 revealed that the organism is well suited for production of (S)-solketal: it shows an adequate enantioselectivity (E value of 49) for the oxidation of racemic solketal; the conversion rate of (R)-solketal is only 3.5 times lower than that of ethanol; the optimal pH for conversion (7.6) is in a region where solketal has sufficient chemical stability; separation of the remaining (S)-solketal from the acid formed is simple; induction of QH-EDH, the sole enzyme responsible for the oxidation of (R)-solketal, occurs during growth on ethanol or butanol so that the presence of solketal (inhibitory for growth) is not required; production of active cells and the conversion step can be integrated into one process, provided that PQQ and solketal addition occur at the appropriate moment; the conversion seems environmentally feasible. However, since high concentrations of solketal inhibit respiration via QH-EDH, further investigations on the mechanism of inhibition and the stability of the enzyme might be rewarding as it could lead to application of higher substrate concentrations with consequently lower downstream processing costs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050208
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Effects of diffusion limitation on immobilized nitrifying microorganisms at low temperatures (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 1-9 
    Details
    ISSN: 0006-3592
    Keywords: nitrification ; immobilized cells ; activation energy ; diffusion limitation ; temperature ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Activation energies of suspended and immobilized nitrifying bacteria were determined and compared to determine if diffusion limitation results in decreased sensitivity for temperature. The activation energy for the respiration activity of suspended Nitrosomonas europaea and Nitrobacter agilis was found to be 86.4 and 58.4 kJ mol-1, respectively. The activation energy for oxygen diffusion in the support material, κ-carrageenan, determined from the effect of temperature on the effective diffusion coefficient (D), was 17.2 kJ mol-1. Consequently, the apparent actvation energy of diffusion limited cells should be lower. It was indeed shown that due to the effect of diffusion limitation and to temperature effects on the Monod constant Ks, the immobilized-cell activity was less sensitive to temperature. The apparent activation energy for immobilized Ns. europaea was between 28.6 and 94.2 kJ mol-1 and for immobilized Nb. agilis between 1.4 and 72.9 kJ mol-1, depending on the oxygen concentration and temperature. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260450102
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    Paper (German National Licenses)
    Fulltext
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