Abstract

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The aim of this study was to assess the antagonistic activities of lactic acid bacteria (LAB) isolated from raw cow milk on selected food-borne pathogens. The antagonistic activities of five different strains of LAB isolates; Lactobacillus plantarum, Leuconostoc mesenteriodes, Lactococcus lactis, Lactobacillus acidiophilus and Lactobacillus bulgaricus from raw cow milk on six selected food borne pathogens; Staphylococcus aureus, Escherichia coli, Salmonella sp., Shigella sp., Enterobacter sp. and Serratia sp. were examined using agar well diffusion method. The production and quantification of lactic acid, hydrogen peroxide and diacetyl by these LAB were determined using standard method of analytical chemistry and the LAB were further assayed for antibacterial effect and activity of their crude bacteriocin. The antagonistic effect against food borne pathogens ranged between 3.2 to 11.3 mm, lactic acid (1.2 to 3.0 ml), diacetyl (0.4 to 1.5 ml) and hydrogen peroxide (0.6 to 2.1 ml), and the bacterocins produced had strong inhibition zones of 2 to 6 mm. The bacterocins activity ranged between 1200 to 5800 AU/mL. The highest bacterocins activity (5800 AU/mL) was with Lactobacillus acidophilus at pH 4.1 while the least (1200 AU/mL) was with Lactobacillus mesenteriodes at pH 1.21. The results of this study showed that metabolites produced by lactic acid bacteria had strong inhibition against food borne pathogens, and could be used as biological preservative in food industry as an alternative to chemical preservatives.

Keywords: Lactic acid bacteria, raw cow milk, pathogens, antagonistic activitie