This study aimed to identify a probiotic bacterium with antagonistic activity against the foodborne pathogen Staphylococcus aureus (S. aureus) and investigate the mechanism of its antibacterial components. Growth kinetics were analyzed to assess bacterial proliferation. Acid and bile salt tolerance are vital indicators for evaluating probiotic survival in the gastrointestinal tract. The results indicated that Companilactobacillus farciminis (C. farciminis) YLR-1 not only had high tolerance to salt conditions (0.03%, 0.3%, and 0.5%) but also has a high survival rate at pH 3–4. The bacteriocin-like inhibitory substance (BLIS) isolated from C. farciminis YLR-1 was dialyzed using a membrane with a molecular weight cut-off (MWCO) of 500 Da, followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis. The results indicate that the BLIS produced by C. farciminis YLR-1 is a small-molecule peptide. BLIS displayed pH tolerance within acidic and neutral environments (4–8) and exhibited thermostability. When treated with proteinase K, the antibacterial action of BLIS was found to be inactivated. Membrane disruption mechanisms were examined using fluorescence imaging and scanning electron microscopy (SEM). SEM and fluorescence imaging revealed that BLIS-induced membrane damage in S. aureus ATCC 25923 causes cytoplasmic leakage and cell death.

The excessive use of synthetic preservatives poses significant threats to food safety and human health. This study systematically investigated the genetic characteristics of the Limosilactobacillus fermentum (L. fermentum) z-6 strain, the antibacterial properties of the bacteriocin-like substance (FC) it produces, and its mechanism of action. The results demonstrated that this bacteriocin-like substance exhibited remarkable antimicrobial activity and exceptional stability, maintaining high activity across a broad pH range (4.0–8.0) and withstanding heat treatment at 100 °C and UV irradiation, indicating robust environmental adaptability. Its proteinaceous nature was confirmed by its detection below 1 kDa on Tricine-SDS-PAGE and its inactivation by trypsin and pepsin. The FC showed broad-spectrum inhibition against foodborne pathogens, including Salmonella enterica serovar Typhimurium, E. coli, A. baumannii, S. aureus, P. mirabilis and L. monocytogenes. Mechanistic investigation demonstrated that the FC exerts antibacterial effects primarily through membrane disruption, as evidenced by a live-dead staining assay confirming significantly enhanced permeability in Salmonella enterica serovar Typhimurium, and scanning electron microscopy revealing distinct pore formation on bacterial surfaces. It is speculated that the FC produced by z-6, due to its excellent properties and outstanding antibacterial performance, could potentially serve as a natural biopreservative.