Chiral Alcohol Synthesis with Microbial Carbonyl Reductases in a Water‐Organic Solvent Two‐Phase System

Production of chiral 4-chloro-3-hydroxybutanoate ethyl esters (CHBE) was performed through microbial asymmetric reduction of 4-chloroacetoacetate ethyl ester (CAAE). The enzymes reducing CAAE to (R)- and (S)-CHBE were found to be produced by Sporobolomyces salmonicolor and Candida magnoliae, respectively. The enzyme of S. salmonicolor is a novel NADPH-dependent aldehyde reductase (AR) belonging to the aldo-keto reductase superfamily. When AR-overproducing Escherichia coli transformant cells or C. magnoliae cells were incubated in an organic solvent-water two-phase system, 300 or 90 mg/mL of CAAE was almost stoichiometrically converted to (R)- or (S)-CHBE (> 92% ee), respectively.