The antibacterial mechanism of the novel bacteriocin LpH25 and the synergistic preservation effect of this bacteriocin and Nisin in fresh milk

Abstract

Bacteriocin, a natural preservative in the food industry, has been found to have a strong inhibitory effect on foodborne pathogens. This study focuses on the structure, stability and antibacterial mechanism of the novel bacteriocin LpH25, as well as the synergistic antibacterial effect of LpH25 in combination with Nisin on E. coli and S. aureus in milk. It was shown that the growth of L. rhamnosus LS-8 was inhibited by acidic environments and pepsin. LpH25 was an unsaturated polypeptide containing an aromatic ring and had good amphipathic. Additionally, bacteriocin LpH25 displayed remarkable thermal stability (121 °C, 30 min) and broad pH stability (pH 2.5–11), remaining stable at −80 °C for over 270 days and exhibiting insensitivity to various enzymes within 2 h. Moreover, LpH25 showed strong inhibitory activity against Escherichia coli, Staphylococcus aureus, and Cronobacter sakazakii within 5 h. Further experiments revealed that LpH25 could effectively inhibit the formation of E. coli outer membranes and flagella to exert antibacterial activity, ultimately leading to cell death. LpH25 inhibited the growth of S. aureus by repressing peptidoglycan synthesis. In addition, the number of viable bacteria in contaminated milk treated with LpH25 mixed with Nisin remained stable (6.5log10 CFU/mL) for seven days. This study provides important theoretical support for promoting the development of antibacterial agents, addressing the challenge of drug resistance of pathogenic bacteria, and extending the shelf life of milk.