Oxidation of 3-, 7-, and 12-hydroxyl Groups of Cholic Acid by an Alkalophilic Bacillus sp.

抄録

TTUR 2-2, an alkalophilic Bacillus strain isolated from soil, grew well in media containing cholic acid (CA) at 5% or higher and efficiently converted 7α- and 12α-hydroxyl groups of CA to keto groups, with the conversion rate for both hydroxyl groups reaching 100% by 72 hours of cultivation. The strain also converted a 3α-hydroxyl group to a keto group, but the conversion rate was about 5% at 72 hours. The strain neither affected any other part of the CA molecule, nor oxidized 7β- or 12β-hydroxyl groups. By NTG mutagenesis, the following mutants were acquired ; (1) converting only the 7α- and 12α-hydroxyl groups, (2) converting only the 12α-hydroxyl group, and (3) converting only the 7α-hydroxyl group. These mutants selectively produce 12-ketochenodeoxycholic acid (12KCDCA), 7-ketodeoxycholic acid (7KDOCA), and 7, 12-diketolithocholic acid (7, I2DKLCA), from CA ; and 7-ketolithochohc acid (7KLCA) from chenodeoxycholic acid (CDCA), respectively, at high yields, close to 100%.