Screening of probiotic strains of Lactiplantibacillus plantarum from Hu sheep and its ability to inhibit Listeria monocytogenes in pasteurized milk

Hu sheep is an important sheep breed in China whose intestines are rich in probiotics. In this study, a total of fifty-nine lactic acid bacteria strains were isolated from Hu sheep feces and twelve strains were identified as Lactiplantibacillus plantarum. Among them, six L. plantarum strains were selected and further evaluated for their probiotic properties. Our results suggested that L. plantarum ELPL14 possess potential probiotic properties. The application of ELPL14 against L. monocytogenes in the pasteurized milk was investigated and the results showed that the growth of L. monocytogenes was significantly decreased when simultaneously incubated with ELPL14 in pasteurized milk at 37 degrees C. Meanwhile, in the ELPL14 fermented pasteurized milk, the growth of L. monocytogenes was also significantly decreased at 28 degrees C and 4 degrees C. We further tested the plantaricin genes by PCR, and found that eleven plantaricin genes (plnEF, plnR, plnJ, plnK, plnL, plnN, plnB, plnC, plnD, plnI, and plnH) were detected in the genome of ELPL14, suggesting that the inhibition of ELPL14 against L. monocytogenes might be due to the production of bacteriocin. Our results demonstrated that L. plantarum ELPL14 from Hu sheep has the potential as a natural candidate for dairy additives to inhibit food-borne pathogens, especially L. monocytogenes.