Biosynthesis of optically pure chiral alcohols by a substrate coupled and biphasic system with a short-chain dehydrogenase from Streptomyces griseus.

The increasing demand for biocatalysts in synthesizing enantiomerically pure chiral alcohols results from the outstanding characteristics of enzymes in reaction, economic, ecological issues. Many carbonyl reductases for producing chiral alcohols have been reported but there is still a lack of good catalytic efficacies. Herein, five carbonyl reductases from different Streptomyces were discovered by the strategy of genome mining. These reductases were overexpressed, and we chose SgCR for further study as it owned better enzyme activity. This protein was purified to apparent homogeneity, and its amino acid sequence was analyzed in comparison with that of the reported SDRs. The biocatalytic properties of SgCR were investigated, and this enzyme was confirmed to have the ability to convert various prochiral ketones into highly optically active alcohols. SgCR exhibited the highest activity towards ethyl 4-chloro-3-oxobutanoate (COBE) and the corresponding product ethyl (S)-4-chloro-3-hydroxybutanoate ((S)-CHBE) was obtained with high yield and excellent e.e. value by optimizing the biphasic system. Eventually, using isopropanol as the co-substrate for NADH recycling in the substrate-coupled reaction, the yield and enantioselectivity of (S)-CHBE were obtained at the values of 90% and 99%, respectively. These results indicate that SgCR is a promising boicatalyst for the synthesis of chiral alcohols in industry.