The catalytic efficiency of lipase in a novel water-in-[Bmim][PF6] microemulsion stabilized by both AOT and Triton X-100

In the water-in-[Bmim][PF6] microemulsion stabilized by both AOT and Triton X-100, the lipase-catalyzed hydrolysis of 4-nitrophenyl butyrate (p-NPB) was investigated to evaluate the catalytic efficiency of lipase in this novel microemulsion. The structural parameters of the microemulsion and the conditions of the enzymatic reaction affect the catalytic activity of lipase, especially the concentration of Tris–HCl buffer. Under optimum conditions, the catalytic activity of lipase in the present microemulsion is much higher than that in H2O saturated [Bmim][PF6]. When the partitioning of the substrate in the microemulsion is taken into account, the catalytic efficiency of lipase in this novel microemulsion is 14.3 times that in H2O saturated [Bmim][PF6] due to the significant decrease of the Michaelis constant in the microemulsion. Due to the large interface, high water activity, and probably the activating effect of the imidazolium cation in the water pool, the present microemulsion is demonstrated to be a promising medium for the lipase-catalyzed hydrolytic reaction. To demonstrate an important biocatalytic application in the IL-based microemulsion, the lipase-catalyzed synthesis of the flavoring agent benzyl acetate via transesterification of vinyl acetate with benzyl alcohol was also studied in the medium. Due to the high dispersion of lipase, large interface and removal of the byproduct, a maximum yield of 94% was obtained, indicating that the novel microemulsion is really important and useful.

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► The structural parameters of the microemulsion and the conditions of the enzymatic reaction affect the activity of lipase.
► The catalytic efficiency of lipase in the microemulsion is 14.3 times that in H2O saturated [Bmim][PF6].
► The imidazolium cation in the microemulsion has activating effect on the lipase-catalyzed hydrolytic reaction.
► The microemulsion is a good medium for the synthesis of benzyl acetate via transesterification.