Functional Properties of Postbiotics Derived From Liquorilactobacillus hordei SK-6 for Bio-Decontamination in Ready-To-Eat Lettuce

This study characterized the postbiotics produced by Lactiplantibacillus plantarum Y48, Liquorilactobacillus hordei SK-6, and Lp. plantarum VB-29, focusing on their antibacterial properties against Escherichia coli and Listeria monocytogenes in contaminated ready-to-eat lettuce. Postbiotic activity was evaluated using the disk diffusion method, minimum inhibitory concentration (MIC, mg/mL), minimum bactericidal concentration (MBC, mg/mL), antioxidant properties, and total phenolic content (TPC). The survival of pathogenic microorganisms in the presence of postbiotics was analyzed using the Baranyi model. The antioxidant content of the postbiotics ranged from 465 to 597 mg TE/100 g, while TPC values were between 1195 and 1353 mg GAE/100 g. Notably, Lq. hordei SK-6 postbiotics exhibited significant antibacterial activity, forming inhibition zones of 17 and 25 mm against E. coli and L. monocytogenes respectively, with a MIC value of 12.5 mg/mL for both pathogens. Based on these findings, Lq. hordei SK-6 postbiotics were tested in contaminated lettuce samples stored at 4°C. The 3% postbiotic treatment reduced the E. coli population from 6.08 to 5.43 log₁₀ CFU/g on Day 0, representing a statistically significant decrease (p < 0.05). After 48 h, the 1% postbiotic treatment reduced E. coli and L. monocytogenes by 0.59 and 0.82 log₁₀ CFU/g, respectively, while a 3% postbiotic resulted in a 1.62 log₁₀ CFU/g reduction in L. monocytogenes (p < 0.05). In conclusion, Lq. hordei SK-6 postbiotics demonstrated potential as a natural biodecontaminant tool to preserve and improve the microbial safety of ready-to-eat lettuce.