Biosynthesis of Phenylglyoxylic Acid by LhDMDH, a Novel D-Mandelate Dehydrogenase with High Catalytic Activity

D-Mandelate dehydrogenase (DMDH) has the potential to convert D-mandelic acid to phenylglyoxylic acid (PGA), which is a key building block in the field of chemical synthesis and is widely used to synthesize pharmaceutical intermediates or food additives. A novel NAD(+)-dependent D-mandelate dehydrogenase was cloned from Lactobacillus harbinensi (LhDMDH) by genome mining and expressed in Escherichia coli BL21. After being purified to homogeneity, the oxidation activity of LhDMDH toward D-mandelic acid was approximately 1200 U.mg(-1), which was close to four times the activity of the probe. Meanwhile, the k(cat)/K-m value of LhDMDH was 28.80 S-1.mM(-1), which was distinctly higher than the probe. By coculturing two E. coli strains expressing LhDMDH and LcLDH, we developed a system for the efficient synthesis of PGA, achieving a 60% theoretical yield and 99% purity without adding coenzyme or cosubstrate. Our data supports the implementation of a promising strategy for the chiral resolution of racemic mandelic acid and the biosynthesis of PGA.