Bioconversion process for synthesis of tert-butyl (3R,5S)-6-chloro-3,5-dihydroxyhexanoate using liquid-core immobilized Saccharomyces cerevisiae CGMCC No 2233

Abstract

Tert-butyl (3R,5S)-6-chloro-3,5-dihydroxyhexanoate was synthesized using asymmetric reduction of tert-butyl (S)-6-chloro-5-hydroxy-3-oxo-hexanoate with liquid-core immobilized Saccharomyces cerevisiae CGMCC No. 2233. The optimum conditions for preparation of the liquid-core immobilized cells were found to be 2% guar gum, 5% CaCl2, 0.8% sodium alginate, capsule diameter 2mm, 0.3% chitosan (1.0×105) solution, and 30 min for formation of the film of liquid-core immobilized cells. The optimum re-cultivation time was 32 h. The optimum reduction conditions were found to be pH 6.8–7.2, 160 r/min, and 30 °C. Conversion was found to reach 100% when initial concentration of substrate was less than 50 g/L. The diastereomeric excess of tert-butyl (3R,5S)-6-chloro-3,5-dihydroxyhexanoate exceeded 99%. The liquid-core immobilized cells retained their effectiveness even after 15 uses.