Development and characterization of recombinant whole-cell biocatalysts expressing epoxide hydrolase from Rhodotorula glutinis for enantioselective resolution of racemic epoxides

Various recombinant whole-cell biocatalysts expressing the epoxide hydrolase (EH) gene of Rhodotorula glutinis were developed and characterized for preparing enantiopure epoxides. Double copies of EH gene were integrated into the chromosome of Pichia pastoris to overexpress EH protein under the control of alcohol oxidase (AOX) promoter. The EH gene was also expressed and displayed on the surface of Saccharomyces cerevisiae. Escherichia coli Rosetta which has tRNA genes for rare codons was employed as a host cell to express the EH gene at a high level. The kinetic characteristics of the recombinant whole-cell biocatalysts were analyzed and relevant parameters were determined. Enantiopure (S)-styrene oxide with an enantiomeric excess higher than 99% was readily obtained by enantioselective hydrolysis of racemic styrene oxides at an initial concentration of 20 mM using the recombinant EHs.