Antibiofilm activity of postbiotics derived from Lacticaseibacillus paracasei

Abstract

Biofilm-associated contamination by Pseudomonas and Bacillus remains a major challenge in dairy processing environments, necessitating natural and effective antimicrobial alternatives. This study evaluated the antimicrobial and antibiofilm efficacy of a postbiotic preparation derived from Lacticaseibacillus paracasei UBLP-35 against these predominant dairy-associated spoilage organisms. The postbiotic was produced through heat inactivation, ultrasonic lysis and lyophilization, yielding a cell-free bioactive preparation. Antimicrobial activity assessed by agar disc diffusion demonstrated a strong, concentration-dependent inhibitory effect (P=0.001). Pseudomonas aeruginosa inhibition zones increased from 6.60±0.15 mm at 300 mg/mL to a maximum of 13.93±0.28 mm at 900 mg/mL, while Bacillus inhibition expanded from 7.23±0.10 mm to 16.15±0.41 mm over the same concentration range. Antibiofilm assays revealed substantial suppression of biofilm formation, with optical density values decreasing significantly at higher postbiotic concentrations (P=0.001). At 900 mg/mL, biofilm biomass was reduced to 0.043±0.002 in P. aeruginosa and 0.032±0.001 in Bacillus subtilis, corresponding to 78.71 and 72.41 per cent inhibition, respectively. Lower concentrations (300-800 mg/mL) also produced graded reductions, confirming a clear dose-response trend. Overall, the results demonstrate that L. paracasei-derived postbiotics exhibited potent, broad-spectrum antimicrobial and antibiofilm activities. The high efficacy at ? 800 mg/mL highlights the potential of this postbiotic as a clean-label biopreservative for mitigating biofilm-mediated spoilage in dairy processing systems. These findings support the industrial applicability of LAB postbiotics as stable, natural and safe interventions for enhancing microbial safety and extending product shelf life.