Functional characterization of a novel microbial esterase identified from the Indian Ocean and its use in the stereoselective preparation of (R)-methyl mandelate

Genomic mining has identified a novel microbial alkaline esterase from the Indian Ocean. This esterase was overexpressed in E. coli BL21 (DE3) and further functionally characterized. Under optimal conditions (10 mmol/L substrate, pH 6.0, 2 h at 40 °C), this esterase can hydrolyze racemic methyl mandelate to ( R )-methyl mandelate with very high optical purity ( e.e. >99%) and yield (nearly 90%). Interestingly, the stereoselectivity of this esterase is opposite to that of two previously reported lipases that can generate ( S )-methyl mandelate through the hydrolysis of racemic methyl mandelate. No organic solvents or other additives were required to optimize the optical purity and production of the final chiral product ( R )-methyl mandelate, which can potentially simplify the production procedure of ( R )-methyl mandelate catalyzed by esterase.