Aerobic and Anaerobic Biotransformation of Bile Acids by Escherichia coli (I)

Abstract

The effects of Escherichia coli on the transformation of bile acids were examined in aerobic and anaerobic culturing systems for 4 days. Bile acids were converted to methyl ester dimethylethylsilyl ether derivatives and determined by capillary gas liquid chromatography. E. coli oxidized cholic acid (CA) and chenodeoxycholic acid (CDCA) to 3α, 12α-dihydroxy- 7-oxo-5β-cholanoic acid (3α12α 7=O) and 3a-hydroxy-7-oxo-5β-cholanoic acid (3α7=O), and reduced these oxo-bile acids to CA and CDCA, respectively. These oxidation and reduction reactions occurred in both aerobic and anaerobic cultures, finally attaining certain equilibrium values. The values, or oxidation/reduction ratios, were 9 or more in the aerobic culture, and about 1 in the anaerobic culture. E. coli also oxidized taurocholic acid in the aerobic culture, but not in the anaerobic culture.