Coimmobilized Dual Enzymes in a Continuous Flow Reactor for the Efficient Synthesis of Optically Pure γ/δ-Lactones

Enzyme catalysis is a promising method for producing chiral chemicals with high stereoselectivity under mild conditions. However, the traditional batch reaction suffers from low enzyme stability, low cofactor recycling, and poor enzyme reusability. Here, we present a continuous-flow method using coimmobilized dual enzymes for the synthesis of chiral γ-/δ-lactones, which are widely used in fragrances and flavors. Typically, a carbonyl reductase mutant SmCR_M5 from Serratia marcescens, was coimmobilized by covalent binding with BmGDH, a glucose dehydrogenase capable of recovering and recycling the cofactor NADPH. After immobilization, SmCR_M5 and BmGDH exhibited a 8.9-/8.7-fold increase in catalytic efficiency (k_cat/K_m) and a 57-/15-fold increase in half-life at 30 °C, respectively. We demonstrated that coimmobilized dual enzymes used in a continuous flow reactor showed a higher reaction rate and a higher space-time yield (1586 g·L^-1 d^-1) than free enzymes and immobilized enzymes in a batch reaction for the production of (R)-δ-decalactone. This continuous flow reactor can run continuously for more than 650 h with 99% ee and 80% conversion, and the total volume exceeds 1500 reactor volumes. The robustness of this continuous-flow immobilized enzyme system provides a green and efficient method for the synthesis of high value-added chiral chemicals.