Highly Enantioselective Conversion of Racemic 1-Phenyl-1,2-ethanediol by Stereoinversion Involving a Novel Cofactor-Dependent Oxidoreduction System of <i>Candida </i><i>p</i><i>arapsilosis </i>CCTCC M203011

Abstract

An economical and convenient biocatalytic process was developed for the preparation of ( S )-1-phenyl-1,2-ethanediol (PED), which is a valuable chiral building block for pharmaceuticals and liquid crystals, by stereoselective microbial conversion from the corresponding racemate. As a result of screening bacteria, yeasts, and molds, the enantioselective conversion of racemic PED by Candida parapsilosis CCTCC M203011 was found to be the most efficient process to produce ( S )-PED with high optical purity of 98% ee and yield of 92%. By detecting the intermediate produced in the reaction by GC−MS, it was suggested that ( S )-enantiomer was produced from the intermediate identified as β-hydroxyacetophenone by asymmetric reduction after stereoselective oxidation of ( R )-enantiomer to β-hydroxyacetophenone. After investigating the cofactor requirement and stereospecificity of the reaction catalyzed by the cell-free extract from C. parapsilosis CCTCC M203011, it was found that the stereoselective conversion involved the oxidation of ( R )-PED to the intermediate with NADP + as the cofactor and the reduction reaction that formed the product used NADH as the cofactor, which was catalyzed by a novel cofactor-dependent oxidoreduction system. The NADP + -dependent ( R )-specific alcohol dehydrogenase involved in stereoinversion was purified from C. parapsilosis CCTCC M203011, which has a relative molecular mass of 45kD.