Genomic, Probiotic, and Safety Characterization of Lactiplantibacillus Plantarum L-1 and the Anti-Biofilm Activity of its Bacteriocin Against Listeria Monocytogenes.

Listeria monocytogenes biofilms persist in food processing environments and pose a serious threat to food safety. This study aimed to comprehensively characterize Lactiplantibacillus plantarum L-1, a strain isolated from traditional Chinese Jiangshui, and to evaluate the anti-biofilm activity of its crude bacteriocin against L. monocytogenes. The strain exhibited promising probiotic attributes, including high survival rates under simulated gastrointestinal conditions (68.9% at pH 2.0, 85.0% in the presence of 0.3% bile salts) and a satisfactory safety profile (antibiotic susceptibility, γ-hemolysis, and no toxicity in mice). Whole-genome sequencing identified genetic determinants for stress tolerance and a gene cluster encoding multiple bacteriocins, including pln EF, pln J, pln N, and a putative bacteriocin. LC-MS identified three expressed bacteriocins: Plantaricin E, F, and N. The crude bacteriocin showed high stability under a range of temperatures (60-121 °C) and pH (2.0-12.0), with a MIC of 2.2 mg/mL against L. monocytogenes. At sub-inhibitory concentrations that did not affect planktonic growth (1/32×, 1/16×, 1/8× MIC), it significantly inhibited biofilm formation in a concentration-dependent manner, achieving 89.5% inhibition at 1/4 × MIC. The bacteriocin suppressed metabolic activity, reduced exopolysaccharide (EPS) production, and inhibit the integrity of biofilm structure, and downregulated the expression of key biofilm-related genes without affecting bacterial growth. These findings highlight the potential of L. plantarum L-1 as a dual-functional probiotic and a natural biocontrol agent against L. monocytogenes biofilms in the food industry.