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Enhancement of epoxide hydrolase production by 60Co gamma and UV irradiation mutagenesis of Aspergillus niger ZJB‐09103

An effective epoxide hydrolase (EH) production strain was mutagenized using 60Co gamma and UV irradiation. Among positive mutant strains, the EH activity of C2‐44 reached 33.7 U/g, which was 267% as much as that of the original Aspergillus niger ZJB‐09103. Compared with the wild type, there were significant changes in morphology for C2‐44, including the color of mycelia on the slants and the shape of conidial head. In addition, glucose and soybean cake were the optimal carbon and nitrogen source in terms of EH activity for the mutant C2‐44 instead of soluble starch and peptone for the wild‐type strain. The reaction time required to reach 99% enantiomeric excesses of (S)‐epichlorohydrin from racemic substrate was shortened significantly by the mutant C2‐44. This phenomenon was probably explained by the higher Vmax for hydrolysis of racemic epichlorohydrin by C2‐44 compared with Aspergillus niger ZJB‐09103.