Revealing the antibacterial mechanism of dielectric barrier discharge cold plasma and lactic acid synergy against Pseudomonas fragi based on molecular docking and oxidative damage.

Slaughter process of broiler is a major source of microbial contamination and chilling is one of the most important steps for carcasses' sterilization. However, limited research has focused on the carcasses' sterilization technology. Furthermore, the use of sodium hypochlorite in chilling operations can pose risks to human health. Therefore, we hypothesized that synergistic application of dielectric barrier discharge cold plasma (DBD) combined with lactic acid (LA) (DBD + LA) can effectively inhibit the growth of proliferation of specific spoilage bacteria in carcasses. Based on this hypothesis, this study first verified that Pseudomonas is the dominant genus responsible for chicken spoilage and that DBD + LA effectively inhibits its growth. Subsequently, the antibacterial mechanism of DBD + LA against Pseudomonas fragi (P. fragi) was further investigated. After 145 s of DBD + LA treatment, a marked decline in the total viable counts was observed, accompanied by the disruption of cell membrane integrity. Furthermore, DBD + LA treatment considerably increased reactive oxygen species levels while reducing the activities of catalase and superoxide dismutase (SOD), intensifying oxidative damage to membrane lipids, proteins, and DNA. Molecular docking revealed that active species, including H2O2 and ·OH, interact with the outer membrane protein A, amino acid residues in SOD, and nucleobases in DNA through hydrogen bonding, compromising the structural stability of bacterial proteins and DNA. Collectively, these findings indicate that DBD + LA induces oxidative stress in P. fragi and suppressing bacterial activity. The results are expected to decrease microbial contamination of chicken carcasses and provide insights for the application of DBD in the food industry.