In vitro antimicrobial characteristics of bacteriocin-producing Lactobacillus strains from Nigerian indigenous fermented foods

A total of 50 bacteriocin- producing Lactobacillus strains isolated from some Nigerian indigenous fermented foods and beverages (ogi, fufu, garri and nono) and characterized as L. acidophilus, L. casei, L. fermentum, L. lactis and L. plantarum were screened for their inhibitory potentials against food- borne pathogenic indicator bacterial isolates; Acinetobater sp., Alkaligenes sp., Enterobacter aerogenes, Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Shigella flexneri, from the same or similar fermented food sources, and against clinical indicator bacterial isolates and type cultures- Bacillus subtilis NCTC8236, K12 Escherichia coli V157, NCTC11560, Vibrio INABA B. cereus CIS25, CIS32, B. licheniformis CIS26, Pseudomonas aeruginosa CIS23, Klebsiella aerogenes CIS24, Kleb. pneumoniae CIS29V and Kleb. aerogenes CIS55. It was observed that each fermented food had its own microbial interaction with minimal in vitro inhibitory activity (1.5 - 10.0%) by the bacteriocin- producing Lactobacillus strains against the indicator bacterial isolates from the fermented foods and beverages, indicating narrow to moderate antimicrobial spectrum; while the inhibitory profiles against the clinical bacterial isolates and the type cultures by the putative strains were between 75.0 - 100.0%. The effect of different pH on the antimirobial potentials of the Lactobacillus strains indicates highest inhibitory activities between 5.5 and 7.5. The survival rates of the pathogenic indicator bacteria in the fermented food sources were between 8 and 14 days while the clinical isolates survived in simulated fermented food samples between 5 and 9 days.