Bile salts and acid tolerance and cholesterol removal from media by some lactic acid bacteria and bifidobacteria

الملخص EN

In this study three strains of Lactobacillus acidophilus (DSM 9126, DSM 20079 and DSM 20242), two strains of Bifid bacteria (infantis DSM 20088 and angulated DSM 20098) and Streptococcus thermophiles DSM 20617 were tested for acid tolerance, bile salt tolerance, capability to remove cholesterol and to DE conjugate sodium taurocholate from the culture medium.

Results showed that a considerable variation existed among cultures in their growth viability in the presence of bile salt, DE conjugation of sodium taurocholate and assimilation of cholesterol from the medium.

Moreover, the two cultures of bifid bacteria (infant is DSM 20088 and angulate DSM 20098) were shown to be the most bile salts tolerant culture.

All bacterial strains tested in this study exhibited sensitivity to acidity at pH 2.

However, increasing the pH of the medium to 3 had improved the acid tolerance of all strains except Streptococcus thermophiles.

Addition of 1% skim milk powder into medium at pH 2 increased the viability of all strains especially bifid bacteria strains.

All tested strains removed less cholesterol from the broth (ranged from 3.08-29.68 %( compared to those grown in broth supplemented with 0.2% bile salts (from 36.07-55.43%).

Furthermore, considerable amount of cholesterol was precipitated with cells obtained from broth enriched with 0.2% bile salts.

Lactobacillus acidophilus DSM 20079 appeared to be more active in DE conjugation of sodium taurocholate (2.38 µmol / ml) compared to the other strains, as well as being able to remove up to 66061 mg of cholesterol (95.6%) from the culture medium and therefore, is regarded as a suitable candidate probiotic and adjunct culture.