Efficient synthesis of (R)-2-chloro-1-phenylethol using a yeast carbonyl reductase with broad substrate spectrum and 2-propanol as cosubstrate

Abstract

In the screening of six Escherichia coli strains for overexpressing recombinant short-chain dehydrogenases/reductases from Yarrowia lipolytica ACA-DC 50109, an NADPH-dependent carbonyl reductase (YlCR) was identified with capability of producing chiral alcohols. The protein YlCR was over-expressed in E. coli BL21 (DE3), purified to homogeneity, and characterized of biocatalytic properties. The purified enzyme exhibited the highest activity at 35°C and optimal pH at 7.0. The kinetic parameters Km and Kcat of YlCR were 7.59mM and 3.9S−1 for α-chloroacetophenone, 366.1mM and 2.94S−1 for 2-propanol. YlCR showed a broad substrate spectrum toward aldehydes, ketones, α- and β-keto esters. Among them, α-chloroacetophenone was found to be efficiently converted to (R)-2-chloro-1-phenylethol, the precursor for the synthesis of anti-depressants and α- or β-adrenergic drugs. Using 2-propanol as the hydrogen donor, α-chloroacetophenone (50mM) was reduced with the recombinant E. coli, and the obtained conversation and enantiomeric excess (e.e) were both 99%. When the α-chloroacetophenone concentration was up to 200mM, the conversion achieved 63%, and the e.e was always 99%. The present study serves as a valuable guidance for the future applications of this versatile biocatalyst.