ANTIMICROBIAL EFFECT OF BACTERIOCIN FROM Lactobacillus fermentum ISOLATED FROM GOAT MILK ON PERISHABLES FOODS. SAN LUIS. ARGENTINA.

MITJANS N M,; CORIA M J, ; ALFONSO J, ; GAIDO RISO N, ; STAGNITTA P

MENDOZA

Congreso; XXXIV Reunión Científica Anual de la Sociedad de Biología de Cuyo; 2016

Sociedad de Biología de Cuyo

ANTIMICROBIAL EFFECT OF BACTERIOCIN FROM Lactobacillus fermentum ISOLATED FROM GOAT MILK ON PERISHABLES FOODS. SAN LUIS. ARGENTINA. Mitjans N M, Coria M J, Alfonso J, Gaido Riso N, Stagnitta PV. FQBYF, UNSL, E-mail: pvstag@unsl.edu.ar In the last decades, food industry has been focused on the reduction of the use of chemical preservatives. Numerous investigations are aimed to discover new bacterial strains able to produce bacteriocins, natural antimicrobials, to be used as food preservatives. The purposes of this study were to evaluate the spectrum of antimicrobial activity of a strain of Lactobacillus fermentum isolated from raw goat milk, determine the nature of the inhibitory substance and study its effect on the conservation of perishable foods. The antimicrobial activity of cell-free supernatant (CFS) of a culture of the strain under study was evaluated against Enterococcus faecalis, Listeria monocytogenes, L. innocua, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Candida albicans (liquid medium method). The peptide nature of the antimicrobial agent was studied by treatment of CFS with proteases. By Tricine-SDS PAGE the presence in the CFS of low molecular weight peptides was investigated. To study its possible application as a food preservative, aliquots of cooked pork shoulder, semi-hard cheese and cream were immersed in CFS, and then incubated in suspensions (107 CFU / ml) of S. aureus and E. faecalis which are indicators of inhibitory activity. L. fermentum showed inhibitory activity superior to 70% against all the indicators tested. The peptide nature of the inhibitory substance was demonstrated by loss of antimicrobial activity of CFS after proteases treatment and the low molecular weight peptide obtained by electrophoresis. These results provide strong evidence that inhibitory substance is a bacteriocin. Bacterial counts in food treated with CFS were between 10 and 100 times lower than in controls, according to the food, demonstrating that bacteriocin inhibited the growth of selected indicators. These studies confirm that L. fermentum produce a broad-spectrum bacteriocin which might be used to prevent spoilage of perishable foods.