Abstract

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Lactobacilli, a genera belonging to Lactic acid bacteria (LAB) are widely applied in fields related to food, feed, pharmaceuticals and biotechnology. The present study was aimed at isolating bacteriocin producing Lactobacillus species from ‘Nono’. The samples were screened for the presence of Lactobacillus spp based on routine cultural characteristics, general morphological, biochemical tests and phenotypically using the API 50CHL technique. The LAB were screened by inoculating into MRS broth for 48 hours for bacteriocin production. The crude bacteriocins were evaluated for in vitro antagonistic activity by agar well diffusion method against foodborne pathogens. The extracted crude bacteriocins were partially purified using 80% cold- acetone saturation. Bacteriocins’ activity (arbitrary unit per ml/AU/mL) as well as stability towards varying temperatures, pH and effect of proteolytic enzymes on the partially purified bacteriocins were determined using standard procedures. The results revealed that Lactobacillus plantarum 1, Lactobacillus fermentum 1 and Lactobacillus pentosus were isolated from nono. The extracted bacteriocins exhibited a broad spectrum of activity against S.aureus (18.3+0.6mm) and E.coli (20+0.8mm). The partially purified bacteriocins were heat stable at temperature range of (40oC- 100oC) (6400-200 AU/ml). They were also stable at pH range of 2-6 (12800-200 AU/mL). The bacteriocins were sensitive to proteolytic enzymes such as chymotrypsin and proteinase K, but not sensitive to catalase and α-amylase which served as the control enzymes. This further confirms the proteinaceous nature of bacteriocins. Bacteriocin of Lactobacillus pentosus exhibited the highest activity against the tested isolates. The result of this research indicates that bacteriocins could be used in controlling contamination causing microorganisms as well as an alternative to the use of chemical preservatives as food additives.

Keywords: Antagonistic Activity, Bacteriocins, Cold-Acetone, Lactobacillus species, Nono.