Characterization of potential probiotic bacteria isolated from sorghum and pearl millet of the semi-arid tropics

Abstract

The present study was conducted to isolate and characterize probiotic properties of bacteria isolated from flour and batter samples of sorghum and pearl millet. A total of five different selective media including plate count agar, yeast glucose chloramphenicol agar, Bifidobacterium agar, actinomycetes isolation agar and de ManRogosa and Sharpe agar were used and the most prominent bacteria (which were found abundantly in the plate) were isolated and maintained on the respective media slants at 4°C for further studies. The bacteria were characterized for various traits including Gram staining, morphology (color, size, shape, elevation, margin, form and surface), biochemistry (urease, catalase, oxidase, hydrogen sulphide, nitrogen reduction, gelatin liquefaction, starch hydrolysis and carbohydrate utilization), IMViC tests (indole, methyl red, Voges Proskauer and citrate utilization), probiotic potentials [acid (pH 2, 3), bile (0.5%), NaCl (6 and 9%)], phenol tolerance [0.4%], antibiotic tolerance (tetracycline, streptomycin, kanamycin, chloramphenicol, ciprofloxacin, ampicillin, penicillin, erythromycin and vancomycin) and antimicrobial activity against human pathogens (Escherichia coli, Staphylococcus aureus and Salmonella typhi). A total of nine probiotic bacterial isolates were short listed based on these traits. The sequences of 16s rDNA gene of the nine isolates were found matched with Bacillus subtilis (two isolates), Bacillus cereus (three isolates), Bacillus pumilus (one isolate), Bacillus amyloliquefaciens (one isolate), Sphingobacterium thalpophilum (one isolate) and Brevibacterium sp. (one isolate) in BLAST analysis. The sequences of the nine bacteria were submitted to NCBI and accession numbers obtained. This study indicated that the selected bacteria could be exploited to develop new probiotic foods.