Isolation, characterization, and properties study of probiotic lactic acid bacteria of selected yoghurt from Bangladesh

Probiotics, as functional food components, are recognized as safe microorganisms of viable single or mixed cultures with claimed health promoting effects on their host by improving the properties of the indigenous intestinal microflora. In the present study, a total of ten probiotic lactic acid bacteria were isolated comprising Lactobacillus acidophilus, Lactobacillus brevis, Bifidobacterium sp. and Streptococcus thermophilus. According to morphological, physiological, and biochemical assays, all the isolates were gram positive, endospore negative, catalase negative, non-motile, and possessed bile salt hydrolase activity characteristic to probiotic bacteria. Carbohydrate fermentation profiles ensured the presumptive identification. Importantly, the isolates were resistant to artificial gastric juice environment at pH 2.2, and their resistance decreased after 24 h of incubation at 37°C. Moreover, bile salt tolerance was observed not only at 0.05, 0.1, 0.15, and 0.3% artificial bile from 0 to 4 h of incubation at 37°C, but also started multiplication after 16 h. The best phenol tolerance found at 0.1 to 0.2% phenol, very low at 0.3 and 0.4% phenol after 12 and 24 h of incubation, respectively. They also possessed excellent tolerance against 1 to 7% NaCl. Because of being probiotic potentiality, the best isolates can be used for probiotic product development in future.