Antibacterial mechanism of action of plantaricin LP21-2 against Escherichia coli and its potential application in yak milk

The mechanism of action of plantaricin against Escherichia coli and its potential application in dairy products remain unclear. In this study, the antibacterial activity and mechanism of action of plantaricin LP21-2 against the E. coli strain ATCC25922 were investigated. The results showed that plantaricin LP21-2 inhibited the growth of E. coli_22 as well as inhibited and degraded the biofilm formation in E. coli_22. The mechanism of action of plantaricin LP21-2 against E. coli_22 cells involves the reduction of cell viability and metabolic activity, triggering the leakage of intracellular substances (e.g., DNA, proteins, and ATP) and inducing oxidative stress damage and morphological deformation. Moreover, plantaricin LP21-2 exhibited no hemolytic activity and negligible toxicity in mammalian Caco-2 cells, indicating good biosafety. When yak milk was used as a food model, E. coli_22 viable counts (6.19 ± 0.03 log CFU/ml) were effectively reduced by 0.23, 0.6 and 1.94 log CFU/ml, with the use of plantaricin LP21-2 at 1/2, 1×, and 2× MIC, respectively, after 12 days of storage at 4 °C. Notably, the addition of plantaricin LP21-2 maintained the nutrient composition, antioxidant parameters, and sensory properties of yak milk. Overall, these findings provide novel insights into plantaricin LP21-2 against E. coli and highlight its promising application in dairy foods.