Isolation and Characterization of Potential Probiotic Lactobacillus gasseri Strains Isolated from Different Sources

The present study was designed with a aim to isolate and select potential probiotic L. gasseri strains from breast fed human infant feces (0–3 months), saliva and breast milk samples (0–3 months old lactating mothers). A total number of 34 L. gasseri isolates isolated from these samples were initially screened to check their survival at pH-2. Out of these 34 isolates only nine isolates viz. Lg5, Lg6, Lg12, Lg23, Lg50b, Lg61b, Lg70, Lg8sf and Lg2sc were found to be most acid tolerant and selected for further in vitro evaluation. When tested for bile tolerance three isolates Lg70, Lg2sc, Lg8sf were found to resist 2% bile and showed highest viability among the tested nine strains. The nine isolates exhibited varying degree of hydrophobicity to three tested hydrocarbons and were also demonstrated to have adhesive properties on Caco-2 cell lines. Four L. gasseri strains viz. Lg50, Lg61b, Lg70 and Lg8sf were found to have strong BSH activity and were also found to assimilate cholesterol in vitro. The isolate Lg70 showed highest in vitro cholesterol assimilation following 24 h incubation in broth having cholesterol. Almost all the L. gasseri isolates showed activity against tested indicator strains. These nine isolates were susceptible to clinically used antibiotics. When tested for virulence traits none of the isolate were found positive for hemolysis, DNase and Gelatinase activity and hence were found to be safe. In this study the L. gasseri strain Lg70 was found as the most promising probiotic candidate.