South Asian Journal of Research in Microbiology

Aims: To determine the antimicrobial potency of lactic acid bacteria isolated from fermented food products.

Place and Duration of Study: Department of Microbiology, Michael Okpara University of Agriculture, Umudike, Abia State, Nigeria.

Methodology: Lactic acid bacteria were isolated using De Mann, Rogosa and Sharpe agar and identified using cultural, morphological and molecular techniques. Spoilage bacteria were isolated from spoiled tomatoes using standard microbiological methods. Isolated lactic acid bacteria were screened for antimicrobial activity. Crude bacteriocin of isolates which exhibited significant inhibition against food spoilage organisms were extracted and used for antimicrobial assay.

Results: Lactic acid bacteria which exhibited significant inhibitory activity against the test organisms were identified as Lactobacillus plantarum and Lactobacillus fermentum while spoilage bacteria isolated from spoiled tomatoes were Enterobacter aerogenes, Pseudomonas aureginosa and Bacillus cereus. Lactobacillus plantarum and Lactobacillus fermentum Crude Bacteriocin Extracts exhibited highest inhibition against Bacillus cereus. Both Crude Bacteriocin Extracts exhibited highest inhibitory activity against the spoilage organisms at 40^oC with zones of inhibition of 16mm and 15mm respectively against Bacillus cereus. There was significant difference in the inhibition of the test organisms at different temperatures (P = 0.05). Both Crude Bacteriocin Extracts exhibited maximum inhibitory activity at pH 4. There was significant difference in the inhibition of the test organisms at different pH 4 (P = 0.05). The inhibitory activity of the Crude Bacteriocin Extracts decreased with increased storage time at a constant temperature of 37^oC.

Conclusion: Bacteriocins produced by Lactobacillus plantarum and Lactobacillus fermentum exhibited significant inhibitory activity against food spoilage bacteria.