Antibacterial effect of postbiotics derived from Lactobacillus plantarum against biofilm forming bacteria

Abstract

The current study investigated the antibacterial and antibiofilm potential of postbiotics derived from Lactobacillus plantarum (UBLP-40) against Bacillus subtilis (MTCC 441) and Pseudomonas aeruginosa (MTCC 424), two biofilm-forming bacteria relevant to dairy processing environments. The preparation of postbiotic involved culturing L. plantarum in MRS broth, followed by heat inactivation, ultrasonication, centrifugation, filtration and lyophilization. Biofilm-forming abilities were assessed using the tissue culture plate method with crystal violet staining. Based on optical density (OD595), B. subtilis (OD = 0.122) was classified as a moderate biofilm former, while P. aeruginosa (OD = 0.306) was a strong biofilm former. Minimum inhibitory concentrations (MICs) of the postbiotic were determined by broth microdilution, with MICs of 500 mg/mL for B. subtilis and 400 mg/mL for P. aeruginosa. Minimum biofilm inhibitory concentrations (MBICs) were found to be 150 mg/mL for both strains. Antibiofilm efficacy at concentrations of 700, 800 and 900 mg/mL demonstrated a dose-dependent reduction in biofilm mass. B. subtilis showed reductions of 51.72, 62.07, and 68.97 per cent  while P. aeruginosa showed reductions of 64.85, 77.23 and 80.20 per cent respectively. All reductions were statistically significant (p<0.05). These results highlight the promising antimicrobial and antibiofilm efficacy of L. plantarum postbiotics, supporting their use as natural, safe alternatives for microbial control in dairy and food processing environments.