Characterization of a d‐Lactate Dehydrogenase from Lactobacillus fermentum JN248 with High Phenylpyruvate Reductive Activity

Abstract Phenyllactic acid (PLA) is a novel antimicrobial compound. A novel NADH‐dependent d ‐lactate dehydrogenase ( d ‐LDH), named as LF‐ d ‐LDH0653, with high phenylpyruvate (PPA) reducing activity was isolated from Lactobacillus fermentum JN248. Its optimum pH and temperature were 8.0 and 50 °C, respectively. The Michaelis–Menten constant ( K m ), turnover number ( k cat ), and catalytic efficiency ( k cat / K m ) for NADH were 1.20 mmol/L, 67.39 s −1 , and 56.16 (mmol/L) −1 s −1 , respectively. The ( K m ), ( k cat ), and ( k cat / K m ) for phenylpyruvate were 1.68 mmol/L, 122.66 s −1 , and 73.01 (mmol/L) −1 s −1 , respectively. This enzyme can catalyze phenylpyruvate and the product presented excellent optical purity (enantioselectivity >99%). The results suggest that LF‐ d ‐LDH0653 is a promising biocatalyst for the efficient synthesis of optically pure d ‐PLA. Practical Application A novel d ‐LDH with phenylpyruvate reducing activity has been isolated and identified. It could be used as a reference for improving the production of optically pure d ‐PLA. d ‐PLA has a potential for application as antimicrobial an agent in dairy industry and baking industry, pharmaceutical agent in medicine and cosmetics.