A new high phenyl lactic acid-yielding Lactobacillus plantarum IMAU10124 and a comparative analysis of lactate dehydrogenase gene

Phenyl lactic acid (PLA) has been widely reported as a new natural antimicrobial compound. In this study, 120 Lactobacillus plantarum strains were demonstrated to produce PLA using high-performance liquid chromatography. Lactobacillus plantarum IMAU10124 was screened with a PLA yield of 0.229 g L-1. Compared with all previous reports, this is the highest PLA-producing lactic acid bacteria (LAB) when grown in MRS broth without any optimizing conditions. When 3.0 g L-1 phenyl pyruvic acid (PPA) was added to the medium as substrate, PLA production reached 2.90 g L-1, with the highest 96.05% conversion rate. A lowest PLA-yielding L. plantarum IMAU40105 (0.043 g L-1) was also screened. It was shown that the conversion from PPA to PLA by lactic dehydrogenase (LDH) is the key factor in the improvement of PLA production by LAB. Comparing the LDH gene of two strains, four amino acid mutation sites were found in this study in the LDH of L. plantarum IMAU10124.