Enzymatic preparation of D-phenyllactic acid at high space-time yield with a novel phenylpyruvate reductase identified from Lactobacillus sp. CGMCC 9967.

An NADH-dependent phenylpyruvate reductase (LaPPR) was identified through screening the shotgun library of Lactobacillus sp. CGMCC 9967. It belongs to D-3-phosphoglycerate dehydrogenase (PGDH) subfamily of 2-hydroxy acid dehydrogenase superfamily. LaPPR was stable at pH 6.5 and 30 °C, with a half-life of 152 h. LaPPR has a substrate preference towards aromatic to aliphatic keto acids, and various keto acids could be reduced into D-hydroxy acids with excellent enantioselectivity (>99%). By construction the coexpression system with glucose dehydrogenase, as much as 100 g L(-1) phenylpyruvic acid was asymmetrically reduced into D-phenyllactic acid with 91.3% isolation yield and 243 g L(-1) d(-1) productivity. The results suggest that LaPPR is a promising biocatalyst for the efficient synthesis of optically pure D-phenyllactic acid.