Abstract: Asymmertric reduction synthesis of (S)-4-chloro-3-hydroxybutyrate ethyl (S-CHBE) from 4-chloro-3-oxo-butyrate ethyl (COBE) was introduced as model reaction. Candida parapsilosis CCTCC M 203011, an efficient biocatalyst, was obtained from laboratory preserved strains, which could reduce COBE to S-CHBE with high efficiency and enantioselectivity. 96% in yield and over 99% in e.e were achieved respectively when COBE was 20 g/L. However, the product inhibition to enzymatic reaction and substrate toxicity to enzyme/microbial cell were the main reasons which restricted the reaction efficiency. Coupled with aqueous-organic biphasic system and substrate feeding strategy, the product was removed in situ and the substrate concentration in aqueous phase controlled below 4 g/L, the accumulated concentration of COBE was increased to 60 g/L with 95% in yield. And a higher product titer (approximately 230 g/L) and high optical purity (>99%) were achieved through increasing the usage of cell.

Key words: Candida parapsilosis, asymmetric reduction, (S)-4-chloro-3-hydroxybutyrate ethyl, substrate feeding, in situ product removal

摘要： 以不对称还原4-氯乙酰乙酸乙酯(COBE)制备(S)-4-氯-3-羟基丁酸乙酯(S-CHBE)为模式反应，从实验室保藏菌种中筛选获得高效生物催化剂近平滑假丝酵母(Candida parapsilosis) CCTCC M 203011，底物浓度为20 g/L时产物产率达96%，光学纯度(e.e值)大于99%. 底(产)物分别具有对细胞(酶)的毒害作用和对酶促反应的抑制作用，是影响不对称还原反应催化效率的主要因素. 采用水-有机双相原位萃取和分批补料联用策略，原位萃取产物并控制水相底物浓度不高于4 g/L，可将底物浓度提高到60 g/L，产率达95%；同时采用高生物量策略，将产物总体积浓度提高到230 g/L，e.e值保持99%以上.

关键词: 近平滑假丝酵母, 不对称还原, (S)-4-氯-3-羟基丁酸乙酯, 底物分批补给, 产物原位萃取