Synthesis of methyl ursodeoxycholate via microbial reduction of methyl 7-ketolithocholate with Eubacterium aerofaciens JCM 7790 grown on two kinds ofcarbon and hydride sources, glucose and mannitol

Eubacterium aerofaciens JCM 7790, which produces 7 beta -hydroxysteroid deh ydrogenase [7 beta -HSDH], efficiently catalyzed the reduction of methyl 7- ketolithocholate [Me-7KLCA] to afford methyl ursodeoxycholate [Me-UDCA] in an anaerobic interface bioreactor. For the high accumulation of Me-UDCA, th e best supplement of carbon and hydride source to the ABCM medium (glucose content, 0.3 wt.%) was screened because glucose strongly repressed 7 beta - HSDH production. The supplementation of cellobiose, mannitol, sodium glucon ate, and sodium pyruvate was effective to improve the production of Me-UDCA , although many mono-and disaccharides, such as fructose, sucrose, and lact ose, strongly repressed 7 beta -HSDH activity. A phosphate buffer was used as the aqueous phase in the carrier to avoid the lowering of medium pH in t he carrier caused by the accumulation of organic acids via fermentation by E. aerofaciens. Thus, the productivity of Me-UDCA was elevated by the combi nation of glucose and mannitol as carbon and hydride sources and by using a phosphate buffer.