Chitosan-Based Composite Film Containing Cell-Free Supernatant of Lactiplantibacillus plantarum JC2211 for Chilled Pork Preservation

Abstract

Traditional fermented vegetables are important resources for screening excellent antibacterial lactic acid bacteria (LAB). In this study, a strain of Lactiplantibacillus plantarum JC2211 with broad-spectrum antibacterial activity against Salmonella Typhimurium (S.T), Staphylococcus aureus (S.a), Listeria monocytogenes (L.m), and Pseudomonas aeruginosa (P.a) was isolated from Yangzhou pickles. The minimum inhibitory concentration (MIC) of its cell-free supernatant (CFS) against all four pathogens was 25 μL/mL. The strain exhibited favorable biosafety and strong environmental adaptability, tolerating 8% NaCl, pH 3.0–10.0, and 0.3% bile salt. The CFS exerted synergistic antibacterial effects via multiple pathways, including increasing cell membrane permeability, reducing membrane potential, decreasing intracellular ATP levels, and inducing ROS accumulation. Metabolite identification indicated that organic acids (dominated by D-lactic acid at 9.37%, citric acid at 8.00%, and phenyllactic acid at 4.42%) were the main components. Using chitosan (CS) as the base material, composite preservation films were fabricated by incorporating 10–50% CFS. The composite film containing 40% CFS (CS/CFS40) exhibited the optimal comprehensive performance, with ABTS and DPPH radical scavenging rates of 90.24% and 79.17%, respectively, along with satisfactory tensile strength (18.70 MPa) and elongation at break (22.93%). In chilled pork preservation, the CS/CFS40 film significantly inhibited the proliferation of spoilage microorganisms, and effectively retarded lipid oxidation. Moreover, the film suppressed the colonization of L.m and S.T on meat surfaces, with bacterial loads maintained at 2.07–2.67 lg CFU/g and 2.92–2.99 lg CFU/g, respectively, over 7 days of refrigeration. Collectively, the CS/CFS40 composite film extended the shelf life of chilled pork to approximately 6 days. This study provides a novel natural biological preservative and eco-friendly active packaging material for chilled meat preservation.