Characterization and antibacterial activity of a Bacteriocin-like Inhibitory Substance (BLIS) produced by Levilactobacillus brevis.

The rise of multidrug-resistant Gram-negative pathogens, for which few treatment options remain, poses a serious and growing global public health threat. This study investigates the antimicrobial activity, characteristics, and mode of action of a bacteriocin-like inhibitory substance produced by Levilactobacillus brevis (L. brevis) strain. The newly isolated L. brevis WJY-3 was identified by 16 S rRNA gene sequencing. The bacteriocin-like inhibitory substance (BLIS WJY-3A) was obtained following a series of purification steps including filtration, concentration, and dialysis, and it exhibited broad-spectrum antibacterial activity against both Gram-positive and Gram-negative pathogens, with particularly potent efficacy against Gram-negative bacteria. The WJY-3 strain was cultivated in a batch mode to produce cell-free supernatant, and the antimicrobial activity, optical density, and pH were monitored. Peak antibacterial activity was observed during the stationary phase, corresponding to 20 h of cultivation. Moreover, BLIS WJY-3A was stable under conditions of heat treatment, an acid-neutral environment, and various types of enzyme treatments. The molecular weight of BLIS WJY-3A was determined using Tris-Tricine sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be less than 1 kDa. Furthermore, propidium iodide uptake assays and scanning electron microscopy revealed that BLIS WJY-3A exerts its antibacterial effect by disrupting the cell membrane integrity of the indicator bacterium Pasteurella multocida (P. multocida). In conclusion, the antimicrobial activity and stability of BLIS WJY-3 warrant further investigation toward the development of an antibiotic alternative compound against diverse pathogenic bacteria in livestock and poultry.