Identification of Lactic Acid Bacteria Isolated From Selected Nigerian Foods and Comparison of Their Bacteriocins Activities

Abstract

Three fermented food samples used for this study were fura, wara and nunu, after collection and inoculation in peptone water, these samples were kept in refrigerator at 5oC for further analysis. After serial dilutions, 0.2 ml of 10-4 dilution factor from each sample was transferred into 20 ml of sterile De-Mann, Rogosa and Sharpe agar (MRS) medium, the plates were labeled as “F (fura), W (wara) and N (nunu)” respectively. All distinct and well isolated colonies were subcultured and examined for various morphological characteristics. Different species of Lactobacillus, Leuconostoc and Lactococcus isolated were subjected to biochemical tests to identify the species. Based on the morphological appearance three genuses of lactic acid bacteria from the samples were isolated. These bacteria were sub cultured in MRS broth and incubated at 32oc, after 24hrs, they were centrifuged at 3000 rpm for 15 minutes. The supernatant containing the bacteriocins were collected. The antimicrobial assay was performed on six bacteria (Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Klebsiella spp, Pseudomonas aeruginosa and Proteus mirabilis) using agar well diffusion as described by Schillinger and Lucke (1989). After incubation, the plates were examined for zones of inhibition. Three replicates were made for each bacterium and the average activity was recorded. The results showed varied inhibitory effects of the bacteriocins on the clinical isolates, when these bacteriocins activity was compared with standard drug, (15μg Gentamicin) an increased activity was observed in gentamicin. In conclusion, the zones of inhibition observed in this research strongly suggest that bacteriocins from lactic acid bacteria are potent in treating diseases caused by these organisms