Efficient microbial resolution of racemic methyl 3-cyclohexene-1-carboxylate as chiral precursor of Edoxaban by newly identified Acinetobacter sp. JNU9335.

Optically active 3-cyclohexene-1-carboxylic acid (CHCA) derivatives are important pharmaceutical intermediates. Due to the special rotatable structure, enantioselective preparation of chiral CHCA is hard to achieve. To identify efficient and enantioselective hydrolases for the biosynthesis of CHCA from methyl 3-cyclohexene-1-carboxylate (CHCM), target-oriented screening from soil samples and gene mining from genome database were explored. All putative hydrolases attempted displayed low enantioselectivity. A hydrolase-producing strain JNU9335 was successfully identified with relatively high enantioselectivity, and was designated as a strain of Acinetobacter sp. according to 16S rDNA sequence and phylogenetic analysis. After optimization, strain JNU9335 could produce 233 U·L‒1 hydrolase with E value of 21. Isooctane/aqueous biphasic system is favorable for the enzymatic resolution of CHCM, the E value of JNU9335 could further be increased to 36. The newly identified JNU9335 could tolerate as high as 1.0 M CHCM, producing (S)-CHCM with ees of 99.6% and isolation yield of 34.7%. This study provides an efficient biocatalyst for the preparation of chiral 3-cyclohexene-1-carboxylic acid derivatives.