Antimicrobial effect of bacteriocin from Lactobacillus fermentum isolated from goat milk on perishable foods. San Luis. Argentina

Abstract— Strain selected for this study was isolated and named as sl36, from samples of goat milk collected from stainless steel drums in a dairy farm (San Luis, Argentina). The LAB strain was biochemically typified as Lactobacillus fermentum and designated as L. fermentum sl36. This identification was confirmed by 16S rRNA full sequences. The selected strain showed antimicrobial activity against food-borne pathogens, Listeria monocytogenes, Listeria innocua, Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa and Escherichia coli. The inhibitory activity was lost after treatment with trypsin, which indicates that this activity is due to a protein nature substance compatible with bacteriocins produced by Gram positive bacteria.The inhibitory substance was stable at different pH and temperatures. Perishable food samples (semi-hard cheese, cream, cooked pork shoulder) were treated with cell free supernatant from studied strain and then with indicator S. aureus and E. faecalis bacteria suspensions. Lactobacillus fermentum sl36 caused the inhibition of the growth of E. faecalis and S. aureus in the treated foods. Our work shows that it is possible to increase the safety of food perishable directly using the bacteriocins produced by the LAB strains, difference from the more frequent practice of using the bacteria themselves as probiotics