Mitogenic response and probiotic characteristics of lactic acid bacteria isolated from indigenously pickled vegetables and fermented beverages
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Lactic acid bacteria from indigenous pickled vegetables and fermented beverages (fermented rice and Madhuca longifolia flowers) were isolated and investigated for their functional characteristics in vitro as potential new probiotic strains. Four isolates (all Lactobacillus spp.) selected on the basis of high tolerance to bile (0.2%) were identified by standard and molecular methods (16S rDNA) as L. helveticus, L. casei, L. delbrueckii and L. bulgaricus from pickled vegetables and fermented beverages respectively. These selected strains had antibiotic resistance, tolerance to artificial gastric juice and phenol (0.4%), enzymatic profile, and antagonistic activity against enteric pathogens (Enterobacter sakazakii, Salmonella typhimurium, Shigella flexneri 2a, Listeria monocytogenes, Yersinia enterocolitica and Aeromonas hydrophila). All strains survived well in artificial gastric juice at low pH (3.0) values for 4 h, possessed bile salt hydrolase activity and were susceptible to most antibiotics including vancomycin. Additionally, the isolates exhibited high tolerance to phenol, high cell surface hydrophobicity (>60%) and induced proliferation of murine splenocytes. All the four strains of present study suppressed the Con A-stimulated proliferation of the mouse spleen cells, although L. casei had the strongest suppressive effect. The results of this study suggest a potential application of the strains (following human clinical trials), for developing probiotic foods.