Whole-Genome Sequencing of Three Lactiplantibacillus plantarum Strains Reveals Potential Metabolites for Boosting Host Immunity Safely

In response to the growing demand for immune-related products, this study evaluated the safety and immune-modulating potential of three newly discovered Lactiplantibacillus plantarum strains (GKM3, GKK1, and GKD7) through toxicity tests and whole-genome sequencing. Safety evaluations, including the analysis of antimicrobial resistance genes, virulence factors, plasmids, and prophages, classified these strains as safe for human consumption. Acute oral toxicity tests further supported their safety. To evaluate their immune-modulating potential, dendritic cells were exposed to these strains, and the secretion of key cytokines (IFN-β and IL-12) was measured. Among the strains, GKK1 exhibited the highest enhancement of IFN-β and IL-12 production, suggesting its potential as an immune-stimulating probiotic. Bioinformatics analysis revealed potential metabolic pathways and secondary metabolites, including predicted bacteriocins, associated with immune modulation. The presence of a nitrate reductase region in the GKK1 strain indicated its ability to produce nitric oxide, a critical molecule involved in immune regulation and host defense. The presence of glucorhamnan-related gene clusters in GKK1 also suggested immune-enhancing effects. Nitrate reductase expression was confirmed using qPCR, with the highest levels detected in GKK1. Moreover, this study is the first to show an anti-inflammatory effect of plantaricin A, linked to its presence in strain GKM3 and its potential therapeutic applications due to sequence similarity to known anti-inflammatory peptides. Overall, these three L. plantarum strains demonstrated a safe profile and GKK1 showed potential as an immunity-enhancing probiotic. However, additional investigation is required to confirm the involvement of specific metabolic pathways, secondary metabolites, and bacteriocins in immune responses.