Abstract

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The study aimed to isolate and characterize probiotic lactic acid bacteria from fermented foods using conventional and molecular methods. The isolation was done using De Man, Rogosa, and Sharpe (MRS) agar using standard procedure and standard biochemical tests for the identification of lactic acid bacteria. The isolates were confirmed using polymerase chain reaction (PCR), sequence analysis and comparison with Genbank resources were conducted to identify species levels. The isolates were evaluated for their probiotic potential using low pH tolerance, bile tolerance, and hemolytic tests, some antibiotic susceptibility pattern and antibacterial activity against enteric pathogens. The isolates identified were rod/bacilli and cocci, all Gram positive, but catalase, citrate, hydrogen sulfide (H2S), indole, urease, Voges-Proskauer negative, and no NH3 production from arginine. The isolates were positive for methyl red and bile esculin salt. The sugar fermentation profile of eight different sugars and Molecular analysis identifies the isolates, which were found to be Lactobacillus plantarum in Kunun-Zaki, Lactobacillus acidophilus, Lactobacillus fermentum, and Lactobacillus plantarum in Nono, Streptococcus thermophilus and Lactobacillus bulgarus in Yoghurt. Phylogenic tree revealed the isolates were related to the reference strain in the Genbank. The study showed that all the isolates were able to survive at low pH levels, tolerate bile concentrations, adhere to cover slips, were non-hemolytic and were susceptible to majority of the antibiotic tested; also the isolates had antagonistic activity against Escherichia coli and Salmonella Typhi, indicating their potential as probiotics.

Keywords: Fermented foods, Lactobacillus species, probiotic, Streptococcus thermophilus