Enhancement of Soluble Expression and Biochemical Characterization of Two Epoxide Hydrolases from Bacillus

Background: Enantiopure epoxides are important intermediates in the synthesis of high-value chiral chemicals. Epoxide hydrolases have been exploited in biocatalysis for kinetic resolution of racemic epoxides to produce enantiopure epoxides and vicinal diols. It is necessary to obtain sufficient stable epoxide hydrolases with high enantioselectivity to meet the requirements of industry. Objectives: Enhancement of soluble expression and biochemical characterization of epoxide hydrolases from Bacillus pumilus and B. subtilis. Material and Methods: Homologous genes encoding epoxide hydrolases from B. pumilus and B. subtilis were cloned and expressed in Escherichia coli. The recombinant epoxide hydrolases were characterized biochemically. Results: Low temperature induction of expression and aC-terminal-fused His-tag enhanced soluble expression of the epoxide hydrolases from the two Bacillus species in E. coli. These epoxide hydrolases could hydrolyze various epoxide substrates, with stereoselectivity toward some epoxides such as styrene oxide and glycidyl tosylate. Conclusions: The position of the His-tag and the induction temperature were found to play a vital role in soluble expression of these two epoxide hydrolases in E. coli. In view of their catalytic properties, the epoxide hydrolases from Bacillus have potential for application in kinetic resolution of some epoxides to prepare enantiopure epoxides and vicinal diols.