Novel antibacterial peptide LPP produced by the probiotic Lacticaseibacillus paracasei GY1 specifically inhibits Staphylococcus aureus

Staphylococcus (S.) aureus is an important microorganism that causes foodborne poisoning, which threatens food safety. However, few studies have investigated novel natural antibacterial peptides produced by the probiotic Lactobacillus sp., which effectively inhibits S. aureus. In mulberry orchard soil used as a screening resource, 28 LAB were isolated and found to have antibacterial effects on S. aureus. Among them, the antibacterial activity of Lacticaseibacillus (L.) paracasei GY1 reached 103 % when 40 g/L sucrose and 15 g/L yeast extract was used, the initial pH was 7, and the temperature was 37 °C for 48 h. This strain maintains cell viability in gastric and intestinal fluids as well as in 4 % NaCl, with its self-aggregation ability reaching 94 %. A novel antibacterial peptide (EKSQAHLDAGAK) was separated and purified by macroporous resin D101, DEAE Focusose 6FF anion exchange chromatography, Sephadex G-15 gel filtration chromatography, and preparative HPLC. Its EC₅₀ and MIC values were 117.57 and 176.64 μg/mL, respectively. Its inhibitory effect is achieved by destroying the cell membrane, enhancing cell permeability, and reducing cell division. The probiotic L. paracasei GY1 can be used to develop functional foods, and the antibacterial peptide serves as an important reference for the precise control of foodborne pathogens.