Co-immobilization of Short-Chain Dehydrogenase/Reductase and Glucose Dehydrogenase for the Efficient Production of (±)-Ethyl Mandelate

Derivatives of (±)-ethyl mandelate are important intermediates in the synthesis of numerous pharmaceuticals. Therefore, efficient routes for the production of these derivatives are highly desirable. The short-chain dehydrogenase/reductase (SDR) is a biocatalyst that could potentially be applied to the synthesis of (±)-ethyl mandelate; however, this enzyme requires the reduced form of the cofactor nicotine adenine dinucleotide (phosphate) (NAD(P)H), which is expensive. In this study, we developed a co-immobilization strategy to overcome the issue of NADPH demand in the SDR catalytic process. The SDR from Thermus thermophilus HB8 and the NAD(P)-dependent glucose dehydrogenase (GDH) from Thermoplasma acidophilum DSM 1728 were co-immobilized on silica gel. The properties and the catalytic abilities of this dual-enzyme system were evaluated. A final yield of 1.17 mM (±)-ethyl mandelate was obtained from the catalytic conversion of ethyl benzoylformate, with a conversion rate of ethyl benzoylformate to (S)-(+)-mandelate of 71.86% and in an enantiomeric excess of > 99% after 1.5 h. This system offers an efficient route for the biosynthesis of (±)-ethyl mandelate. Graphical Abstract In this study, we developed a co-immobilization strategy to overcome the issue of NADPH demand in the SDR catalytic process. The SDR from Thermus thermophilus HB8 and the NAD(P)-dependent glucose dehydrogenase (GDH) from Thermoplasma acidophilum DSM 1728 were co-immobilized on silica gel. Results showed that, this dual-system offers an efficient route for the biosynthesis of (±)-ethyl mandelate.