Metabolomic signatures of lactic acid bacteria: their growth rates and roles in enhancing kimchi quality

Abstract Kimchi, a traditional Korean fermented food, undergoes spontaneous fermentation driven by lactic acid bacteria (LAB), which significantly influences its flavor, texture, and nutritional content. The quality of kimchi is largely determined by the metabolites produced during microbial metabolism, but the relationship between intra- and extra-cellular metabolism of LAB remains unclear. This study aimed to investigate the metabolism of various LAB strains isolated from kimchi, through metabolomic analysis of both their intra- and extra-cellular matrices, and to explore the role of their metabolism during kimchi fermentation. Hetero- and homo-fermentative characters of Leuconstoc and Lactiplantibacillus strains were characterized by production of extracellular mannitol and lactate, respectively. Notably, the rapid growth of Lactiplantibacillus strains was found to associated with a substantial uptake of extracellular glucose and aromatic amino acids, whereas the slow growth of Leuconostoc strains contributed to the production of most extracellular amino acids and a less uptake of extracellular glucose. Indeed, Lactiplantibacillus strains may regulate intracellular pH through the elimination of intracellular acidic amino acids, while Leuconostoc strains possibly protect themselves against osmotic stress by producing intracellular betaine. Moreover, kimchi fermented under slow fermentation conditions contained higher levels of mannitol and amino acids compared to fast fermentation condition, thereby enhancing its nutritional value and overall quality. This study highlights the links between the slow fermentation or metabolic distinction of LAB and the potential contribution to the improvement of fermented food quality.