Characterization of a Bacteriocin-like Substance from Loigolactobacillus coryniformis WYQ-2 and Its Antibacterial Activity Against Escherichia coli.

Escherichia coli is a common porcine diarrheal pathogen transmitted via the fecal-oral route through contaminated environments and feed. This study evaluated the antimicrobial potential of a bacteriocin-like substance produced by Loigolactobacillus coryniformis WYQ-2 isolated from pickled vegetables. Its physicochemical stability, molecular mass, and antimicrobial spectrum were characterized, and the mode of action against Escherichia coli was investigated through intracellular ATP quantification, live/dead staining, and scanning electron microscopy (SEM). The substance exhibited broad-spectrum antibacterial activity, with the strongest inhibition against Escherichia coli (the diameter of the inhibition zone reached 41.35 mm). It remained stable under prolonged UV irradiation (0-2.5 h), under heating at 100 °C, and within the pH range of 3.0-9.0. Molecular mass determination revealed a low-molecular-weight peptide (<2.7 kDa). Protease susceptibility tests showed activity was reduced by trypsin and papain, slightly sensitive to proteinase K, yet relatively stable toward other tested proteases. Mechanistically, ATP levels declined markedly within 0.5-2 h of treatment, while live/dead staining and SEM confirmed membrane disruption, deformation, and surface indentations in treated Escherichia coli cells. These findings demonstrate that the WYQ-2-derived bacteriocin-like substance possesses favorable physicochemical traits and exerts antibacterial action primarily by compromising membrane integrity, highlighting its promise as a natural alternative for controlling porcine diarrheal diseases.