Prophylactic efficacy of Lactobacillus curvatus B67-derived postbiotic and quercetin, separately and combined, against Listeria monocytogenes and Salmonella enterica ser. Typhimurium on processed meat sausage.

This study investigated the antimicrobial and antibiofilm efficacy of separate and combined treatments of Lactobacillus curvatus B67-produced postbiotic and the polyphenolic flavanol quercetin against Listeria monocytogenes and Salmonella enterica ser. Typhimurium. The antimicrobial potentiality of the postbiotic was chiefly associated with organic acids (e.g., lactic and acetic acids). At sub-minimum inhibitory concentration (1/2 MIC), the postbiotic and quercetin effectively reduced the pathogenic biofilm cells on processed pork sausage and meat-processing surfaces (e.g., stainless-steel and rubber). Moreover, the postbiotic exhibited strong residual antimicrobial efficacy over diverse pH and temperature ranges. In addition, the combination of postbiotic with quercetin increased the leakage of pathogenic intracellular metabolites (e.g., nucleic acids and protein) and inhibited pathogenic biofilm formation on both biotic and abiotic surfaces. Therefore, this study confirmed that lactic acid bacteria-derived postbiotic and plant-derived quercetin could be used as potential alternative bioprotective agents in the meat processing industry.

Antibiofilm efficacy of Leuconostoc mesenteroides J.27-derived postbiotic and food-grade essential oils against Vibrio parahaemolyticus, Pseudomonas aeruginosa, and Escherichia coli alone and in combination, and their application as a green preservative in the seafood industry.

Foodborne pathogen-mediated biofilms in food processing environments are severe threats to human lives. In the interest of human and environmental safety, natural substances with antimicrobial properties and generally regarded as safe (GRAS) status are the futuristic disinfectants of the food industry. In this study, the efficacy of bioactive, soluble products (metabolic by-products) from lactic acid bacteria (LAB) and plant-derived essential oils (EO) were investigated as biocidal agents. The postbiotic produced by kimchi-derived Leuconostoc mesenteroides J.27 isolate was analyzed for its metabolic components to reveal its antimicrobial potential against three pathogenic microorganisms (Vibrio parahaemolyticus, Pseudomonas aeruginosa, and Escherichia coli). Additionally, the efficacy of food-grade EO (eugenol and thymol, respectively) was also assessed in our study. Determination of the minimum inhibitory concentration (MIC) of postbiotic and EO against three tested pathogens revealed that the sub-MIC (0.5 MIC) of postbiotic and EO could efficiently inhibit the biofilm formation on both seafood (squid) and seafood-processing surfaces (rubber and low-density polyethylene plastic). Moreover, the polymerase chain reaction (PCR) analysis confirmed that the LAB J.27 isolate possesses bacteriocin- and enzyme-coding genes. The residual antibacterial activity of the produced postbiotic was maintained over a diverse pH range (pH 1-6) but was entirely abolished at neutral or higher pH values. However, the activity was unaffected by exposure to high temperatures (100 and 121 °C) and storage (30 days). Notably, the leakage of intracellular metabolites, damage to DNA, and the down-regulation of biofilm-associated gene expression in the pathogens increased significantly (p > 0.05) following the combination treatment of postbiotic with thymol compared to postbiotic with eugenol. Nonetheless, all in vitro results indicated the prospective use of combining Leu. mesenteroides J.27-derived postbiotic with both EO as a "green preservative" in the seafood industry to inhibit the formation of pathogenic microbial biofilms.