The Antibacterial Effect and Mechanism of a Bacteriocin Produced by <i>Weissella sagaensis</i> ZD-66 against Major Foodborne Pathogens

<i>Salmonella</i> Typhimurium is a pathogen bacterium responsible for foodborne diseases. In this study, <i>Weissella sagaensis</i> ZD-66, a bacteriocin-producing strain, was isolated from pickled vegetables. The bacteriocin produced by this strain was characterized, and its antibacterial mechanism was investigated. The genome size of <i>W. sagaensis</i> ZD-66 was 1,862,304 bp, with a GC content of 36.87%. Further, bioinformatic analysis using the BAGEL4 database revealed a class IIa bacteriocin gene cluster, identified as Penocin A. <i>W. sagaensis</i> ZD-66 showed maximum antibacterial activity at 28 h during fermentation. The <i>W. sagaensis</i> ZD-66 was partially purified by using dialysis and Tricine-SDS-PAGE, which revealed a molecular weight of less than 1 kDa. The <i>W. sagaensis</i> ZD-66 showed broad-spectrum inhibition against foodborne pathogens, including <i>S.</i> Typhimurium, <i>Staphylococcus aureus</i>, <i>Escherichia coli</i>, <i>Listeria monocytogenes</i>, and <i>Cronobacter sakazakii</i>. The bacteriocin was stable at 121°C for 30 min, pH resistant (pH 3-7), and under UV exposure for up to 2.5 h. However, its antibacterial activity of bacteriocin decreases after treatment with pepsin, trypsin, and pronase E. Furthermore, the treatment with bacteriocin led to the cell membrane being damaged, nucleic acid leakage, and reduced intracellular ATP content. Observation of the ultrastructure of bacteria by Scanning electron microscopy revealed that bacteriocin can inhibit <i>S.</i> Typhimurium by disrupting the cell membrane and pore formation. These results suggest that the bacteriocin produced by <i>W. sagaensis</i> ZD-66 has the potential for a natural food preservative.