Candida parapsilosis Whole Cell Catalyzed Asymmetric Reduction:Inhibition and Removal of Substrate(Product)

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.