Significant variations in bile tolerance and ability to assimilate cholesterol were observed among 12 cultures of Lactobacillus acidophilus of human origin. The degree of bile tolerance as measured by rapidity of growth in MRS broth supplemented with .3% oxgall could not be predicted by the rapidity of growth in the broth without oxgall. There was no apparent direct relationship between bile tolerance and cholesterol assimilation. However, among the cultures that most actively assimilated cholesterol, there were significant differences in bile tolerance. The most active cholesterol-assimilating cultures also varied in the ability to produce bacteriocins. A culture of L. acidophilus of human origin, which assimilates cholesterol, grows well in presence of bile, and produces bacteriocins can be selected for use as a dietary adjunct for humans. A culture of L. acidophilus possessing all these characteristics should have an advantage over one that does not in establishing and functioning in the intestinal tract to assimilate cholesterol.

The relationships among growth in the presence of bile, deconjugation of sodium taurocholate, and assimilation of cholesterol by 19 cultures of Lactobacillus acidophilus were examined. Cultures of L. acidophilus were grown at 37 degrees C in lactobacilli MRS broth supplemented with sodium thioglycollate, sodium taurocholate, and cholesterol (cholesterol phosphatidyl choline micelles). Deconjugation activity was maximum in the late exponential phase of growth, which also coincided with maximum assimilation of cholesterol. Considerable variation existed among cultures in their ability to grow in the presence of bile, to deconjugate sodium taurocholate, and to assimilate cholesterol. However, statistical analyses revealed no significant correlations.

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