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 K_cat, K_m, V_max 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⁻¹ D‑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.