Improving whole-cell biocatalysis for helicid benzoylation by the addition of ionic liquids

Abstract

Highly efficient and regioselective synthesis of pharmacologically useful 6′-O-benzoyl-helicid catalyzed by the whole-cell catalysts was successfully performed for the first time. The catalytic performance of Aspergillus oryzae whole cells for helicid benzoylation was significantly enhanced in acetone-ionic liquids (ILs) systems containing anions PF6, BF4, and TF2N as compared to pure acetone. The catalytic performances of A. oryzae whole cells not only depend on the anion of ILs, but the cation. In acetone-[BMIM][PF6] (5%, v/v) system, the substrate conversion efficiency reached 99 % at 24 h and initial reaction rate was achieved to be 7.42 mM/h, while 99 % substrate conversion was acquired at 72 h in acetone. Moreover, the A. oryzae whole cells showed excellent 6′-regioselectivity (99 %) and high operational stability in helicid benzoylation maintaining 75.5 % of its original activity after seven repeated reaction cycles in acetone-[BMIM][PF6] (5%, v/v) system. In conclusion, the inclusion of a suitable level of ionic liquids might exhibit a high potential for improving whole-cell biocatalysis for helicid benzoylation in a regioselective and cost-effective manner.