Antibacterial Activity of Bacteriocin-Like Inhibitory Substances (BLIS) of <i>Levilactobacillus brevis</i> PG-11 against <i>Salmonella</i> Typhimurium

<i>Salmonella</i> Typhimurium is a major cause of foodborne illness. This study investigated the antibacterial activity, characterization, and mode of action of bacteriocin-like inhibitory substances (BLIS) produced by <i>Levilactobacillus brevis</i> PG-11, isolated from traditional Chinese kimchi. The BLIS of <i>L. brevis</i> PG-11 exhibited strong antibacterial activity against <i>S</i>. Typhimurium ATCC 14028. It also exhibited broad-spectrum antimicrobial activity against various foodborne and human pathogens, including <i>Escherichia coli</i>, <i>Staphylococcus aureus</i>, <i>Klebsiella pneumoniae</i>, <i>Pseudomonas aeruginosa</i>, and <i>Staphylococcus epidermidis</i>. The minimum inhibitory concentration (MIC) of the BLIS against <i>E. coli</i>, <i>S</i>. Typhimurium, and <i>S. aureus</i> was 62.5, 125, and 125 mg/ml. The active antibacterial substances were partially purified using dialysis and tricine-SDS-PAGE, revealing a molecular weight of less than 1 kDa for the active antibacterial substances. Furthermore, the BLIS was stable under acidic pH (pH 3.0-6.0), heat treatment (121°C, 20 min), UV radiation (4 h), and sensitivity to papain. Maximum antibacterial activity was observed during the stationary growth phase after 32 h of culture. Propidium iodide (PI) uptake, ATP leakage, and scanning electron microscopy (SEM) confirmed that BLIS disrupted cell membrane integrity, leading to cell membrane damage pore formation, and bacterial growth inhibition. These results highlight the potential of <i>L. brevis</i> PG-11 BLIS as a natural biological preservative for food preservation applications.