Use of Ionic Liquid To Significantly Improve Asymmetric Reduction of Ethyl Acetoacetate Catalyzed by Acetobacter sp. CCTCC M209061 Cells

Abstract

Biocatalytic reduction of ethyl acetoacetate (EAA) to ethyl (R)-3-hydroxybutyrate [(R)-EHB] with Acetobacter sp. CCTCC M209061 cells was successfully conducted in ionic liquid (IL)-based biphasic systems. Several water-immiscible ILs were used to construct biphasic systems. The best IL investigated was 1-butyl-3-methylimidazolium hexafluorophosphate (C4mim·PF6), which also had good biocompatibility. Several influential variables were examined. The optimum parameters were as follows: volume ratio of buffer to C4mim·PF6, 1/2 (v/v); substrate concentration, 55 mmol/L; buffer pH, 5.5; cosubstrate concentration, 80 mmol/L; reaction temperature, 35 °C; and shaking speed, 220 rpm. Under these optimal conditions, the initial reaction rate, the yield, and the product e.e. were 0.39 mmol/(L min), 90.8%, and >99%, respectively, which were much better than results reported previously. This efficient whole-cell biocatalytic process was feasible on a 450-mL preparative scale, and the immobilized cells showed excellent ...