Assessment of In Vitro Probiotic Potential of Lactic Acid Bacteria

Abstract

Abstract Probiotic potential of fermented milks isolates Lactobacillus rhamnosus NS6, Streptococcus thermophilus MD2 and Streptococcus thermophilus MD8 were carried out by performing various in vitro tests. MD2 and MD8 were able to survive at pH 2 and 3 in broth, while NS6 was found to be pH sensitive and could not survive at pH 2, but maintained its viability at 3 pH. All the cultures were able to survive at 0.5 % (w/v) oxgall (bile) concentration in broth. NS6 was most resistant to bile than rest isolates. They were susceptible to ampicilin, azithromycin, tetracycline, gentamycin and erythromycin while these strains were resistant to nalidixic acid, oxacilin, colistin and kanamycin. Cell supernatant of NS6 showed a higher antimicrobial activity i.e., 24 mm zone against E. coli and S. aureus; 16 mm zone against B. cereus and S. typhi and neutralization of cell supernatant showed significant reduction in antimicrobial activity. All the three strains were hydrophobic to both, xylene and n-hexadecan. The mean percentage hydrophobicity was higher to xylene than n-hexadecanfor all the strains. Cell-auto-aggregation was found to be rising during 5 h of incubation for cultures. They were able to co-aggregate with B. cereus, S, typhi, E. coli and S. aureus (indicators). None of the culture could hydrolyze sodium taurocholate (bile) while they deconjugated sodium taurocholate to release free cholic acid. NS6 gave maximum bile deconjugation ability (364 µg/ml). Similarly, in case of cholesterol reduction and antioxidative activity (ABTS method), NS6 was more potent than others. Keywords: Lactobacillus rhamnosus, Streptococcus thermophilus, lactic acid bacteria, probiotics, bile Cite this Article M.R. Kathiriya, S. Hati, J.B. Prajapati et al. Assessment of In Vitro Probiotic Potential of Lactic Acid Bacteria. Research & Reviews: Journal of Dairy Science and Technology. 2016: 5(1):  17–30p.