Antagonistic effect and bacteriocinogenic activity of Lactic Acid Bacteria isolated from <i>Sorghum bicolor</i>-based ‘ogi’ on food borne bacterial pathogens from cabbage

Abstract

Background: Lactic acid bacteria (LAB) are important organisms recognized for fermentative ability as well as health and nutritional benefits. A large number of bacteriocins from LAB have been characterized and a number of studies have indicated the potential usefulness of bacteriocin in food preservative. The objective of this study was to evaluate the antagonistic effects and bacteriocinogenic activity of LAB isolated from Sorghum bicolor-based ‘ogi’ against selected food borne bacteria from cabbage samples.

Methodology: Five samples of Sorghum bicolor-based ‘ogi’ and 5 samples of suspected infected cabbage heads were randomly collected using sterile water proof material from Abakpa main market, Abakaliki, and processed at the Applied Microbiology Laboratory of Ebonyi State University, for isolation of LAB and food borne pathogen by conventional culture and biochemical identification tests. Antagonistic effects of LAB and its bacteriocinogenic activity were determined by agar well diffusion test.

Results: Three different Lactobacillus species designated A, B, and C, were isolated from the Sorghum bicolorbased ‘ogi’ and 5 bacterial species were isolated from cabbage heads; Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Salmonella, and Shigella species. The Lactobacillus species had inhibitory effect against S. aureus, E. coli, and Shigella species with inhibition zone diameters (IZD) of 19 mm, 10 mm, and 10 mm respectively. The crude bacteriocin extracts from the Lactobacillus species showed higher inhibitory activity against tested bacterial isolates at 10-1 (0.1ml) than at 10-2 dilution (0.01ml), and the inhibitory activity was higher at pH 2 than pH 6 and 7, with no activity at pH 8.

Conclusion: This study showed that LAB and its extracted bacteriocin demonstrated in vitro inhibitory activity against food borne pathogens isolated from cabbage heads. There is the need to further characterize the active components of the bacteriocin for possible commercial use as preservatives and potential source of new antimicrobial agent.

Keywords: Lactic acid bacteria, bacteriocin, cabbage, fermented food, ‘ogi’