Enantioselective resolution of (±)-1-phenylethyl acetate by extracellular proteases from deep-sea bacterium Bacillus sp. DL-2

Abstract

Chiral 1-phenylethanol and its ester derivative are important chiral chemicals in diverse industries and the preparation of those optically pure enantiomers is of great importance. One bacterium, Bacillus sp. DL-2, whose extracellular proteases could efficiently asymmetrically hydrolyse (±)-1-phenylethyl acetate, was isolated from the deep sea of the Western Pacific. After the immobilization of extracellular proteases and the optimization of enzymatic reactions, (R)-1-phenylethanol was prepared with the enantiomeric excess (e.e.) being 97% and the yield being 41%, respectively. The optimal resolution reaction condition for the preparation of (R)-1-phenylethanol using immobilized extracellular proteases was found to be 5-mM (±)-1-phenylethyl acetate, 360 mg/mL immobilized extracellular proteases, pH 6.5, and 20 °C for 2 h. (S)-1-phenylethyl acetate was generated through enzymatic kinetic resolution with the e.e. being as high as 99% and the yield being 71%, respectively. The optimal resolution reaction condition for the preparation of (S)-1-phenylethyl acetate was found to be 2.5-mM (±)-1-phenylethyl acetate, 440 mg/mL immobilized extracellular proteases, pH 7.5, and 35 °C for 10 h. Our report is the first report about the kinetic resolution of (±)-1-phenylethyl acetate using proteases and the enantio-preference of the proteases was found to be the same as those of most other esterases/lipases. Also notably, the optical purity of (S)-1-phenylethyl acetate generated through kinetic resolution using the proteases of Bacillus sp. DL-2 was the highest report so far. Proteases from deep-sea Bacillus sp. DL-2 are new contributions to the biocatalyst library for the preparation of valuable chiral alcohols and chiral esters through kinetic resolution.

Keywords:

• Asymmetric hydrolysis
• extracellular proteases
• immobilization
• marine microorganisms
• (R)-1-phenylethanol
• (S)-1-phenylethyl acetate

Acknowledgements

We are grateful for the Research Vessel KEXUE of the Chinese Academy of Sciences for collecting deep-sea samples.

Disclosure statement

The authors declare that they have no conflict of interest.

Additional information

Funding

This work was financially supported by the Scientific and Technological Project of Ocean and Fishery from Guangdong Province [A201701C12], the Senior User Project of RV KEXUE [KEXUE2018G05], the Priority Research Program of the Chinese Academy of Sciences [XDA11030404] and Natural Science Foundation of Guangdong Province [2018A030313151].