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

Abstract 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. Highlights • An excellent anti-microbial strain ZX1 was isolated. • Strain ZX1 was a superior d ‑PLA-producing wild strain. • A novel ldhD gene from strain ZX1 was cloned, expressed and characterized. • E. coli BL21 (d ‑LDH) provided a high productivity and conversion yield. [ABSTRACT FROM AUTHOR]