Novel antimicrobial compounds from fermented food-derived Lacticaseibacillus paracasei B1 and Lactiplantibacillus plantarum O24 strains: Genomic and proteomic analysis

This study investigated the genomic and functional characteristics of antimicrobial compounds produced by Lacticaseibacillus paracasei strain B1 and Lactiplantibacillus plantarum strain O24, previously isolated from traditional Polish fermented foods. Whole-genome sequencing and bioinformatics analyses revealed multiple gene regions encoding bacteriocins, including lactococcins, plantaricins, and enterolysin A, with genes on both chromosomes and plasmids. Experimental validation confirmed the proteinaceous nature of the active antimicrobial substances, as evidenced by their sensitivity to proteolytic enzymes (trypsin, pepsin, and proteinase K) and their stability under heat (40–100 °C) and acidic pH conditions. Antimicrobial activity was observed against Gram-positive and Gram-negative bacteria, significantly inhibiting Listeria monocytogenes and Escherichia coli O157:H7. Fourier-Transform Infrared (FT-IR) spectroscopy assessed functional groups and active sites. Purification and molecular weight estimation via SDS-PAGE analysis identified protein bands of approximately 15 kDa and 10 kDa. LC-MS/MS analysis confirmed these results and indicated partial homology with previously reported bacteriocins, suggesting they may represent novel bacteriocins or bacteriocin-like inhibitory substances. These findings highlight the potential of food-origin lactic acid bacteria strains as a source of diverse and robust antimicrobial compounds, paving the way for food preservation and antimicrobial therapy applications.