Heterologous expression of a novel d‑lactate dehydrogenase from Lactobacillus sp. ZX1 and its application for d‑phenyllactic acid production.

d‑Phenyllactic acid (d‑PLA) shows great potential for biopreservative production owning to its anti-microbial activity. In this study, strain ZX1, which could inhibit the growth of other microbes was isolated and identified as Lactobacillus genus. Strain ZX1 could produce d‑PLA with 0.16 g·L-1. Furthermore, a novel d‑lactate dehydrogenase gene was identified and expressed in Escherichia coli BL21 (DE3) with the specific activity of 71.64 U·mg-1 protein under the optimal temperature and pH of 35 °C and 6.2. The kinetic constants for Kcat, Km, Vmax were 10.71 s-1, 2.356 mM and 11.27 μM·mg-1·min-1 for phenylpyruvic acid (PPA), respectively. 18.21 g·L-1d‑PLA from PPA with yield of 90.49% and productivity of 2.49 g·L-1·h-1 was obtained by the recombinant E. coli BL21 harboring d‑LDH, indicating that engineered E. coli BL21 (d‑LDH) has excellent potential in commercial d‑PLA production.