Abstract: The biocatalytic asymmetric hydrolysis of styrene oxide to (R)-1-phenyl-1,2-ethanediol catalyzed by Mung bean epoxide hydrolase in organic solvent/buffer biphasic systems was studied. In comparison with an aqueous monophasic system, the organic solvent/buffer biphasic system not only inhibited effectively the non-enzymatic hydrolysis of styrene oxide, but also markedly improved the substrate concentration, product yield, and product ee value. Among various organic solvents examined, the n-hexane was the most suitable organic phase for the reaction. In the n-hexane/buffer biphasic system, the initial reaction rate was clearly faster and the product yield and product ee value were much higher owing to the excellent solvent property of n-hexane for styrene oxide and relatively good biocompatibility with Mung bean epoxide hydrolase. Moreover, the optimal volume ratio of n-hexane to buffer, reaction temperature, buffer pH value, and substrate concentration for the enzymatic hydrolysis were found to be 1:1, 35 ^oC, 6.5, and 20 mmol/L, respectively, under which the initial reaction rate, the product yield, and the product ee value were 5.42 mmol/(L·h), 49.2%, and 94.3%, respectively.

Key words: Mung bean epoxide hydrolase, styrene oxide, (R)-1-phenyl-1,2-ethanediol, organic solvent/buffer biphasic system, asymmetric hydrolysis