Characterization and Antibacterial Activity of Lactic Acid Bacteria Isolated from Traditionally Fermented Foods against Some Selected Food Pathogens

Abstract

This study identified the antimicrobial compounds found in lactic acid bacteria isolated from several traditional fermented foods, such as ogi, ugba, and yoghurt, as well as their antimicrobial effectiveness against a few chosen food pathogens. Fifteen (15) food samples including five each for yoghurt, ogi, and ugba were tested for the presence of lactic acid bacteria. Nine organisms were isolated from the food samples and were phenotypically and genotypically characterized. It was discovered that two of the isolates were Lactococcus spp, five Lactobacillus spp, one Bacillus spp, and one Streptococcus spp. The genotypic characterization revealed that the lactic acid bacteria isolates Lactococcus lactis subsp. lactis 0711XYBLS, Lactobacillus fermentum CS19, Lactococcus lactis and Lactobacillus fermentum were closely related at 99% evolutionary distance. For the sole purpose of this research, Lactococcus lactis subsp. lactis 0711XYBLS and Lactobacillus fermentum CS19 were utilized to determine their antimicrobial potentials against selected food pathogens. Antimicrobial metabolites, diacetyl, hydrogen peroxide and lactic acid were produced by the isolated lactic acid bacteria at varying concentrations. The selected lactic acid bacteria isolates were tested against food pathogens and their clear zones of inhibitions were noted. Lactococcus lactis subsp lactis 0711XYBLS isolated from ogi showed the highest antibacterial activity against Gram positive and Gram negative food pathogens ranging from 18.67 ± 1.15 to 12.67 ± 0.57 and 16.33 ± 0.56 to 8.00 ± 6.08 respectively whereas Lactobacillus fermentum CS19 showed antibacterial activity for Gram positive food pathogens at 16.00 ± 1.00 to 8.67 ± 1.15 and 15.33 ± 1.15 to 8.67 ± 0.57 in Gram negative food pathogens. Between the pathogens, a significant difference was recorded at a significant level of p<0.05. Nevertheless, both organisms demonstrated strong antibacterial activity against the chosen food pathogens and have the potential to be used as new antimicrobial agents. This potential can be used extensively in the food industry as biopresevatives rather than chemical preservation, which may be harmful to consumer’s health.