摘要：

The asymmetric reduction of ethyl 3-oxobutanoate (EOB) to ethyl (S)-(+)-3-hydroxybutanoate ((S)-(+)-3-EHB) catalyzed by dehydrogenases with high activity in cetyltrimethylammonium bromide (CTAB) permeabilized baker's yeast cells using alcohol and glucose as co-substrates was studied. The results showed that the activity of the alcohol dehydrogenase and glucose-6-phosphate dehydrogenase in the permeabilized cells increased 482-fold and 6.5-fold, respectively, compared with those in the control cells. The concentration of the permeabilized cells was particularly important for the high yield and selectivity in aerobic conditions and in the medium containing alcohol and glucose. EOB was reduced faster by the permeabilized cells than by the control cells. Both the yield and the enantiomeric excess of (S)-(+)-3-EHB were low when the cell concentration was less than 90 mg/ml. The highest (S)-(+)-3-EHB concentration of 314 mmol/L was obtained with ≥90 mg/ml of the permeabilized cells at the optimized pH, temperature and feeding rate. During the first 6 h, the yield and enantiomeric excess reached 94% and 98%, respectively, but decreased to 91% and 85% after 24 h.

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