The environmental friendly biotransformation of cyclohexene catalyzed by chloroperoxidase (CPO) with H₂O₂ as oxidant was carried out in this work. The yield of expected products was tuned and enhanced by solvent engineering. The results showed that the conversion of cyclohexene was enhanced 31% when only 1.5% (W_ILs/W_PBS) of imidazole/pyridine ionic liquids (ILs) was introduced into the PBS buffer. The decrease of enzyme kinetic parameters K_m and increase of K_cat and K_cat/K_m indicated that both the affinity and specificity of CPO to the substrate were improved in the presence of ILs, resulting in the increase of turnover number. This was the main reason of conversion enhancement. Moreover, UV-vis, fluorescence and circular dichroism assay and analysis of products composition indicated that ILs played multiple functions in this enzyme-catalyzed reaction: phase transfer catalysis, inducing catalytically favorable conformation of CPO and tuning the composition of products. This enzymic-reaction was over within 150 min, and enzyme consumption was small. So, it has some potential utility in industry application.

Key words: chloroperoxidase, cyclohexene, imidazole/pyridine ionic liquids