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

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 PF 6 , BF 4, and TF 2 N 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][PF 6 ] (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][PF 6 ] (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.