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YEAST CATALYZED REDUCTION OF BETA-KETO-ESTERS .1. FACTORS AFFECTING WHOLE-CELL CATALYTIC ACTIVITY AND STEREOSELECTIVITY
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UNSPECIFIED (1995) YEAST CATALYZED REDUCTION OF BETA-KETO-ESTERS .1. FACTORS AFFECTING WHOLE-CELL CATALYTIC ACTIVITY AND STEREOSELECTIVITY. BIOCATALYSIS AND BIOTRANSFORMATION, 12 (3). pp. 159-178. ISSN 1024-2422.
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Abstract
Six yeasts were studied for their ability to reduce ethyl 4-chloroacetoacetate (ethyl 4-chloro-3-oxobutanoate) stereoselectively. Five species reduced the substrate to ethyl (S)-4-chloro-3-hydroxybutanoate of high (92-99%) optical purity. With glucose-grown cells, substrate reduction could only be demonstrated when growth was oxygen-limited, whereas xylose-grown Pichia capsulata could be grown under conditions of oxygen excess without losing its reducing ability. Zygosaccharomyces rouxii exhibited high enantioselectivity (greater than or equal to 98% ee (S)-enantiomer) under all conditions tested, whilst in P. capsulata, a novel switch was observed from producing mainly the (S)-enantiomer using glucose as co-substrate to producing mainly the (R)-enantiomer using 2-propanol as co-substrate. This switch was correlated with a change in reduction predominantly from an NADPH-dependent dehydrogenase system to an NADH-dependent system. In the production of ethyl (R)-4-chloro-3-hydroxybutanoate with P. capsulata, the enantioselectivity was also found to depend upon growth conditions. With glucose-grown cells, higher enantioselectivity was observed using cells harvested in stationary phase (93-94% ee) compared with cells harvested in exponential phase (43-60% ee). Growing P. capsulata with xylose rather than glucose as the major source of carbon for growth resulted in an eight-fold increase in the specific rate of ethyl (R)-4-chloro-3-hydroxybutanoate production using 2-propanol as co-substrate, although enantioselectivity was slightly reduced (65-81% ee). compared with the maximum achieved with glucose-grown cells. The effect of growth on xylose could also be correlated with enhanced activity of an NADH-dependent (R)-selective dehydrogenase system.
Item Type: | Journal Article | ||||
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Subjects: | Q Science > QD Chemistry T Technology > TP Chemical technology |
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Journal or Publication Title: | BIOCATALYSIS AND BIOTRANSFORMATION | ||||
Publisher: | HARWOOD ACAD PUBL GMBH | ||||
ISSN: | 1024-2422 | ||||
Official Date: | 1995 | ||||
Dates: |
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Volume: | 12 | ||||
Number: | 3 | ||||
Number of Pages: | 20 | ||||
Page Range: | pp. 159-178 | ||||
Publication Status: | Published |
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