Functional Characterization of a Marine Bacillus Esterase and its Utilization in the Stereo-Selective Production of D-Methyl Lactate.

Chiral lactic acid and its ester derivatives are crucial building blocks and platforms in the generation of high value-added drugs, fine chemicals and functional materials. Optically pure D-lactic acid and its ester derivatives cannot be directly generated from fermentation and are quite expensive. Herein, we identified, heterologously expressed and functionally characterized one Bacillus esterase BSE01701 from the deep sea of the Indian Ocean. Esterase BSE01701 could enzymatically resolve inexpensive racemic methyl lactate and generate chiral D-methyl lactate. The enantiomeric excess of desired chiral D-methyl lactate and the substrate conversion could reach over 99 % and 60 %, respectively, after process optimization. Notably, the addition of 60 % (v/v) organic co-solvent heptane could greatly improve both the enantiomeric excess of D-methyl lactate and the conversion. BSE01701 was a very promising marine microbial esterase in the generation of chiral chemicals in industry.