Characterization and antibacterial activity of lactobacillus species isolated from a traditionally fermented cereal beverage (kunun-zaki) in Nigeria

Kunun-zaki is an indigenous cereal beverage in Nigeria that undergoes spontaneous fermentation by mixed cultures of autochthonous bacteria species. Given the antimicrobial compounds synthesized by lactic acid bacteria (LAB), this study aimed to evaluate the antibacterial activities of Lactobacillus species isolated from Kunun-zaki. The traditionally fermented cereal beverage (Kunun-zaki) was analyzed for pH and LAB counts. Lactobacillus isolates were identified using both phenotypic tests and molecular method (16S rRNA amplification). Then the representative isolates were subjected 16S rRNA amplification analysis using universal primers (27F/1492R). Cell-free supernatant (CFS) extracts of the isolates were tested for antibacterial activity against Staphylococcus aureus, Escherichia coli, Salmonella spp., and Klebsiella spp., by using the agar well diffusion method. The pH values of traditionally fermented Kunun-zaki ranges from 4.50 ± 0.10 to 6.83 ± 0.05, while LAB count ranges from 2.45 × 103 ± 1.80 × 102 cfu/mL to 2.87×103 ± 4.36 ×101 cfu/mL within 0-48 h after preparation. Eight isolates were obtained and identified as Lactiplantibacillus plantarum (35%), Limosilactobacillus fermentum (25%), Lacticaseibacillus acidophilus (25%), and Ligilactobacillus salivarius (12.5%) The CFS extracts of Lactobacillus isolates exhibitedsignificant inhibitory activity against Staphylococcus aureus, E. coli, Salmonella spp., and Klebsiella spp., with zones of inhibition ranging from 8.16 ± 0.28 mm to 20.30±0.60 mm. Notably, only Salmonella spp. was resistance to some Lactobacillus isolates (LBK0-23, LBK4-24, LBK4-26), showing a pattern of selective resistance. Tukey’s HSD post-hoc analysis confirmed significant differences (p<0.05) among the inhibition profiles of individual isolates. These results indicate the potential of Lactobacillus spp. in traditional production of Kunun-zaki beverages and their role as promising antibacterial agent.