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  • 1
    Electronic Resource
    Electronic Resource
    Continuous production of enantiopure 1,2-epoxyhexane by yeast epoxide hydrolase in a two-phase membrane bioreactor (2000)
    Springer
    Applied microbiology and biotechnology 54 (2000), S. 641-646 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A two-phase membrane bioreactor was developed to continuously produce enantiopure epoxides using the epoxide hydrolase activity of Rhodotorula glutinis. An aqueous/organic cascade, hydrophilic, hollow-fiber membrane bioreactor was used: (1) to carry out large-scale resolution of epoxides, (2) to continuously extract residual enantiopure epoxides from the aqueous phase, and (3) to separate inhibitory formed diol from the yeast cells contained in the aqueous phase. Dodecane was employed to dissolve-feed epoxide as well as to extract residual epoxide. 1,2-Epoxyhexane was used as a model substrate. By use of this membrane bioreactor, enantiopure (S)-1,2-epoxyhexane (〉98% enantiomeric excess) was obtained with a volumetric productivity of 3.8 g l−1 h−1. The continuous-production system was operated for 12 days and resulted in 38 g enantiopure (S)-1,2-epoxyhexane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530000451
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Chiral resolution of 2,3-epoxyalkanes by Xanthobacter Py2 (1988)
    Springer
    Applied microbiology and biotechnology 27 (1988), S. 337-340 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary With propene-grown cells of Xanthobacter Py2 it was possible to resolve racemic mixtures of 2,3-epoxyalkanes. Only 2S-forms were metabolized by this organism, resulting in pure 2R-2,3-epoxyalkanes. Chiral resolution was obtained with trans-2,3-epoxybutane, trans-2,3-epoxypentane and cis-2,3-epoxypentane. Xanthobacter Py2 was however not able to discriminate between the enantiomeric forms of 1,2-epoxyalkanes, resulting in the complete degradation of both chiral forms of 1,2-epoxyalkanes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00251764
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis of optically pure 1,2-epoxypropane by microbial asymmetric reduction of chloroacetone (1992)
    Springer
    Applied microbiology and biotechnology 38 (1992), S. 297-300 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A number of bacteria and yeast was screened for asymmetric reduction of prochiral chloroacetone into chiral 1-chloro-2-propanol, which is chemically convertible into chiral 1,2-epoxypropane. In this way Rhodotorula glutinis produced optically pure S-1,2-epoxypropane with 98% enantiomeric excess and in a relatively high final concentration. The enzyme that catalysed the asymmetric reduction was an NAD(P)H-dependent alcohol dehydrogenase. Reduction of racemic 3-chloro-2-butanone resulted in mixtures of cis and trans-2,3-epoxybutane, indicating that no enantioselective reduction of this haloketone occurred.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00170075
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Dithiol- and NAD-dependent degradation of epoxyalkanes by Xanthobacter Py2 (1995)
    Springer
    Applied microbiology and biotechnology 42 (1995), S. 775-781 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A broad range of epoxyalkanes was converted into the corresponding ketones by cell extracts of Xanthobacter Py2. Both 1,2- and 2,3-epoxyalkanes were degraded and in addition, the degradation of 2,3-epoxyalkanes in all cases was highly enantioselective. Conversion of a deuterium-labelled substrate indicated that the ketone product was probably formed indirectly via an hydroxy intermediate. Degradation of epoxyalkanes by Xanthobacter Py2 was dependent on both NAD and another, not yet identified, cofactor that was present in the low-molecular-mass fraction (LMF) of propene-grown cells. It is proposed that the LMF was involved in a reductive reaction step since it could be replaced by dithiothreitol (DTT) and various other dithiol compounds. Epoxyalkane-degrading activity was inhibited by the sulphhydryl blocking reagent N-ethylmaleimide (NEM). Inhibition by NEM and stimulation by LMF, DTT and other dithiols was effective only in the simultaneous presence of NAD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00171961
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Resolution of 1,2-epoxyhexane by Rhodotorula glutinis using a two-phase membrane bioreactor (1999)
    Springer
    Applied microbiology and biotechnology 53 (1999), S. 7-11 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Large-scale resolution of epoxides by the yeast Rhodotorula glutinis was demonstrated in an aqueous/organic two-phase cascade membrane bioreactor. Due to the chemical instability and low solubility of epoxides in aqueous phases, an organic solvent was introduced into the reaction mixture in order to enhance the resolution of epoxide. A cascade hollow-fiber membrane bioreactor was used (1) to minimize the toxicity of organic solvents towards the epoxide hydrolase of R. glutinis, and (2) to remove inhibitory amounts of formed diol from the yeast cell containing aqueous phase. Dodecane was selected as a suitable solvent and 1,2-epoxyhexane as a model substrate. By use of this membrane bioreactor, highly concentrated (0.9 M in dodecane) enantiopure (〉 98% ee) (S)-1,2-epoxyhexane (6.5 g, 30% yield) was obtained from the racemic mixture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051606
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Dithiol- and NAD-dependent degradation of epoxyalkanes by Xanthobacter Py2 (1995)
    Springer
    Applied microbiology and biotechnology 42 (1995), S. 775-781 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  A broad range of epoxyalkanes was converted into the corresponding ketones by cell extracts of Xanthobacter Py2. Both 1,2- and 2,3-epoxyalkanes were degraded and in addition, the degradation of 2,3-epoxyalkanes in all cases was highly enantioselective. Conversion of a deuterium-labelled substrate indicated that the ketone product was probably formed indirectly via an hydroxy intermediate. Degradation of epoxyalkanes by Xanthobacter Py2 was dependent on both NAD and another, not yet identified, cofactor that was present in the low-molecular-mass fraction (LMF) of propene-grown cells. It is proposed that the LMF was involved in a reductive reaction step since it could be replaced by dithiothreitol (DTT) and various other dithiol compounds. Epoxyalkane-degrading activity was inhibited by the sulphhydryl blocking reagent N-ethylmaleimide (NEM). Inhibition by NEM and stimulation by LMF, DTT and other dithiols was effective only in the simultaneous presence of NAD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050330
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    Paper (German National Licenses)
    Fulltext
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