Bacteriostatic mechanism of Lactiplantibacillus plantarum CS3 cell-free supernatant of on soy sauce spoilage bacteria

This study aimed to purify and characterize a novel antibacterial substance produced by Lactiplantibacillus plantarum CS3 and explored its antibacterial mechanism. Antimicrobial substances were isolated and purified by ultrafiltration, extraction, and gel filtration chromatography. The purified substance was identified by LC/MS as the WRWLRKL heptapeptide (1057.29 Da). The minimum inhibitory concentrations of the crude extract of antimicrobial peptides (CS3-F2) against Staphylococcus hominis and Staphylococcus capitis were 1.25 mg/ml and 1 mg/ml, respectively. The crude extract directly affected the cell wall and membrane, inhibited biofilm formation, caused leakage of cell contents, and directly bound to genomic DNA, affecting the respiratory metabolism of spoilage bacteria, blocking normal binding of enzymes and receptors, and ultimately leaded to cell death. Furthermore, the addition of L. plantarum CS3 could improve the quality and flavor characteristics of soy sauce.