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.