Effect of lactic acid bacteria on phenyllactic acid production in kimchi

Phenyllactic acid (2-hydroxy-3-phenyl propionic acid; PLA) is a natural antibacterial compound derived from phenylalanine catabolism. PLA shares a metabolic pathway with lactic acid (LA) and is metabolized by the glycolytic enzyme, lactate dehydrogenase, during fermentation. In this study, we identified PLA in fermented kimchi and investigated its relationship with kimchi-derived lactic acid bacteria (LAB) during kimchi fermentation using liquid chromatography-mass spectrometry. PLA was detected in four kimchi samples to different extents depending on the initial glucose concentration and fermentation stage, indicating a link between bacterial growth and PLA production. PLA content in the kimchi was 12.0-21.1 mu g/ml at the early stage and decreased to 4.8-9.5 mu g/ml at 3 or 4 weeks. PLA production in LAB was associated with the presence of lactate dehydrogenase genes, and differed from lactic acid production. Bacteria lacking the D-lactate dehydrogenase gene (2-Hacid dh) did not produce PLA. Addition of Lactobacillus plantation enhanced PLA production 1.7-fold, reaching a maximum at 14 days. Lactobacillus brevis and Leuconostoc lactis caused increases of approximately 1.5-fold compared to the control. These results suggested that addition of specific LAB to kimchi as starter cultures can increase PLA content, and has great potential to enhance safety of the food product.