Comparative Analysis of <i>N</i>-Lactoyl-phenylalanine and 3-Phenyllactic Acid Production in Lactic Acid Bacteria from Kimchi: Metabolic Insights and Influencing Factors

<i>N</i>-Lactoyl-phenylalanine (Lac-Phe) is a metabolite known for its appetite-suppressing and antiobesity properties, while phenyllactic acid (PLA) is recognized for its antibacterial activity. Both metabolites are derived from phenylalanine and lactic acid metabolism through peptidase and dehydrogenase activities. The aim of this study was to investigate the production of Lac-Phe and PLA in kimchi, focusing on the role of lactic acid bacteria (LAB). Ultrahigh performance liquid chromatography coupled with time-of-flight mass spectrometry was used to quantify these metabolites in homemade and commercial kimchi. Lac-Phe and PLA were detected in both kimchi sample types. Various genera, including <i>Lactobacillus</i>, <i>Leuconostoc</i>, and <i>Weissella,</i> were evaluated for Lac-Phe and PLA production. LAB strains exhibiting high Lac-Phe production generally showed lower PLA production, indicating an inverse relationship between these two metabolites. Analysis of dipeptidase sequences revealed that the presence of carnosine dipeptidase 2 (CNDP2)-like M20 metallopeptidase is crucial for Lac-Phe production in LAB. Additionally, phenylalanine was identified as a major factor for both Lac-Phe and PLA production, whereas lactic acid supplementation did not significantly affect their production levels.