Tolerance of Lactobacillus and Bifidobacterium strains to low pH, bile salts and digestive enzymes

Probiotic strains of L. casei, L. acidophilus, L. helveticus, B. animalis, B. lactis and two strains of B. bifidum were examined for their survival at pH 3.0 and 3% bile salts. Additionally, the viability of L. casei cells was tested in presence of pepsin, trypsin, chymotrypsin, alpha-amylase and lipase, and after heating at 90ºC for 30 min. It was found that all pre-treatments caused significant decrease in bacteria survival. The most sensitive strain for stress factors was B. bifidum 1. Using Caco-2 monolayer culture as the in vitro adhesion model, the significant reduction of adherence after thermal treatment, digestion with pepsin, trypsin and chymotrypsin, and bile salts were observed. The inhibition of bacteria adhesion after thermal denaturation and proteolysis proved an hypothesis that adhesion factors are of proteinaceous origin.