Adaptation of Listeria monocytogenes to Enterocin B: Insights from a Cheese-Based Model System

Despite extensive EU food safety regulations, controlling L. monocytogenes in dairy product remains challenging due to its ability to withstand hurdles technologies by adaptation systems. Biopreservation addresses consumer demand for eco-friendly products, with LAB-derived bacteriocins widely used in the food industry. The present study was conducted within the framework of the ONFOODS project (www.onfoods.it) and it was focused on identification and characterization of an enterocin and the evaluation of the transcriptomic response of L. monocytogenes in a cheese-based model system. Cell free supernatant of E. faecium CR12 was tested for his ability to inhibit L. monocytogenes in an agar-well diffusion assay. The proteinaceous nature of the active compound was assessed, and its antimicrobial activity were evaluated in relation to the growth kinetics and after exposure to different pH and temperatures. Bacteriocin adsorption and effect on Listeria growth were examined. The partially purified and identified enterocin B was included in a model system inoculated with L. monocytogenes and transcriptomic response was evaluated. The highest enterocin production was reached after 9-18 h of growth, and it was susceptible to proteases. The activity was unchanged after exposure to different pH and temperature conditions. The effect was bactericidal in exponential phase of Listeria, and adsorption was maximum at pH 4–6, and 25–60 °C. CR12 was sensitive to all tested antibiotics except gentamycin, displaying γ-hemolytic activity and no amine production. Bacteriocin encoding genes entA, entB and entP were detected but only an enterocin B was identified. The addition of enterocin led to an overall increase in stress response and motility genes expression, while adhesion and virulence factors remained generally downregulated. This study elucidated the mechanisms of action of enterocin B and clarified its role in regulating gene expression of Listeria The study elucidated the antibacterial mechanism of enterocin B and its potential application in cheese. This study shed the light of mechanisms of action of enterocin B and cleared the regulation of gene expression in L