Effect of Bacteriocins-producing Lactic Acid Bacteria on Target Microorganisms

A B S T R A C T The problem of increased resistance of bacteria to antibiotics and the increasing demand for safe foods has enhanced the interest in replacing antibiotics by natural products (biopreservatives). In this study the antagonistic effect of lactic acid bacteria (LAB) producing-bacteriocins on nine target organisms was studied using the agar-well diffusion assay (AWDA). LAB was isolated from Sudanese fresh sausages, intestines of different animals, saliva, cheese and cucumber in MRS broth and on MRS agar media. The target organisms studied were Salmonella sp, S. typhi, Staphylococcus aureus, Bacillus subtilis, B. cereus, B. stearothermophilus, B. pantotheticus, Escherichia coli, and Pediococcus strain BFE 2306. Only 16 LAB isolates of 30 produced clear inhibition zones. These LAB isolates were identified as Enterococcus faecalis (3 isolates), Enterococcus avium, Pediococcus pentosaceus (3 isolates), P. domanosus, Lactobacillus murinus (2 isolates), L. gasseri (2 isolates), L. acidophilus, L. plantarum, L. alimentarius, and L. casi subsp. Rhamanosus. Crude bacteriocins and pellets of Enterococcus faecalis, Pediococcos pentosaceus and Lactobacillus murinus exhibited the strongest antimicrobial activity ranging between 40 and 1280 AU/ml, while most supernatants of bacteriocin-producers did not show antimicrobial activity against all indicator organisms (0.00-640 AU/ml). Sudanese products of animal sources can be a rich source for bacteriocins-producing LAB and can be used