The bile acid deconjugating capacity of Saccharomyces boulardii was tested in isolated culture and in co-culture upon the bile acid metabolizing capacity of Bacteroides fragilis. S. boulardii was grown over 60 h in plain brain heart infusion (BHI) broth and in the presence of either 2 mM glycocholic or glycochenodeoxycholic acid under both aerobic and anaerobic conditions. S. boulardii did not metabolize either glycocholic acid or glycochenodeoxycholic acid. S. boulardii and B. fragilis were grown anaerobically together in BHI broth supplemented with either 0.1 mM glycholic acid or 0.1 mM glycochenodeoxycholic acid. When S. boulardii and B. fragilis were anaerobically co-cultured, S. boulardii did not alter the bile acid metabolism of B. fragilis. Specifically primary and conjugated bile acids decreased over time, while keto bile acids and free bile acids increased. S. boulardii not only fails to metabolize primary conjugated bile acids but it does not enhance or inhibit the bile acid metabolism of B. fragilis when the organisms are co-cultured in anaerobic medium.