Abstract: In this study, a recombinant Escherichia coli strain carrying D-mandelate dehydrogenase, L-leucine dehydrogenase and mandelate racemase encoding genes was established by using a dual plasmid co-expression system of pACYCDuet-1 and pET28a, which was named as E. coli BL21(DE3)/pACYCDuet-1-EsLeuDH-LhDMDH:pET28a-ArMR. Under low temperature and in the presence of low concentrations of the inducer, the recombinant strain successfully expressed three recombinant enzymes with catalytic activities, and the activities of D-mandelate dehydrogenase, L-leucine dehydrogenase and mandelate racemase in its fermentation broth were 195.8, 56.2 and 174.5 U/mL respectively. Using the induced whole cells as the catalyst and D,L-mandelic acid as the substrate, the yield of L-phenylglycine was 77.48% after reaction at 30 ℃ for 48 h in 500 mmol/L NH4Cl-NH3·H2O buffer at pH 9.5 with an agitation rate of 180 r/min with an enantiomeric excess (e.e.) value of greater than 99%. This study has potential for industrial application, laying a solid foundation for large-scale biosynthesis of L-phenylglycine.

Key words: L-phenylglycine; whole-cell catalysis; green chemistry; co-expression; cascade reaction