Antimicrobial activities of lactic acid bacteria isolated from akamu and kunun-zaki (cereal based non-alcoholic beverages) in Nigeria

Abstract

Three lactic acid bacteria (LAB) isolates designated AS₁, AS₂ and KN₄ isolated from kunun-zaki (a sorghum based non-alcoholic beverage widely consumed in Northern Nigeria) and identified as Lactobacillus plantarum, Lactobacillus brevis and Lactobacillus delbruckii, respectively, produced significant inhibitory compounds in broth. The partially purified inhibitory compounds were screened by agar spot assay method for antagonistic activity against target Gram positive and negative bacteria as well as yeasts associated with food spoilage. The partially purified compounds exhibited strong activity against Staphylococcus aureus ATCC 12600, Bacillus cereus and Escherichia coli ATCC 11775. The inhibitory compound produced by AS₁ and KN₄ inhibited Bacillus subtilis. Only the inhibitory compound produced by AS₁ affected Candida albicans and Candida krusei. Analysis of variance indicated that there was a significant difference (P<0.05) in the susceptibility of the different target organisms to partially purified inhibitory compounds. Gram positive bacteria were affected more than yeasts. Proteolytic enzymes, trypsin and pepsin, but not catalase and α-amylase, completely inactivated antagonistic activity of the compounds demonstrating their proteinacious nature. The inhibitory compounds were fairly heat stable and also stable over broad pH ranges. The use of these or related GRAS isolates in the production of this and related beverage may increase the safety, shelf life and marketing appeal of such beverages

Keywords: Bacteriocins, lactic acid bacteria (LAB), target organisms, antimicrobial activity.

African Journal of Biotechnology, Vol 13(29) 2977-2984