Deoxycholic acid transformations catalyzed by selected filamentous fungi.

More than 100 filamentous fungi strains, mostly ascomycetes and zygomycetes from different phyla, were screened for the ability to convert deoxycholic acid (DCA) to valuable bile acid derivatives. Along with 11 molds which fully degraded DCA, several strains were revealed capable of producing cholic acid, ursocholic acid, 12-keto-lithocholic acid (12-keto-LCA), 3-keto-DCA, 15ß-hydroxy-DCA and 15ß-hydroxy-12-oxo-LCA as major products from DCA. The last metabolite was found to be a new compound. The ability to catalyze the introduction of a hydroxyl group at the 7(α/ß)-positions of the DCA molecule was shown for 32 strains with the highest 7ß-hydroxylase activity level for Fusarium merismoides VKM F-2310. Curvularia lunata VKM F-644 exhibited 12α-hydroxysteroid dehydrogenase activity and formed 12-keto-LCA from DCA. Acremonium rutilum VKM F-2853 and Neurospora crassa VKM F-875 produced 15ß-hydroxy-DCA and 15ß-hydroxy-12-oxo-LCA, respectively, as major products from DCA, as confirmed by MS and NMR analyses. For most of the positive strains, the described DCA-transforming activity was unreported to date. The presented results expand the knowledge on bile acid metabolism by filamentous fungi, and might be suitable for preparative-scale exploitation aimed at the production of marketed bile acids.

Hydroxylation of lithocholic acid by selected actinobacteria and filamentous fungi.

Selected actinobacteria and filamentous fungi of different taxonomy were screened for the ability to carry out regio- and stereospecific hydroxylation of lithocholic acid (LCA) at position 7ß. The production of ursodeoxycholic acid (UDCA) was for the first time shown for the fungal strains of Bipolaris, Gibberella, Cunninghamella and Curvularia, as well as for isolated actinobacterial strains of Pseudonocardia, Saccharothrix, Amycolatopsis, Lentzea, Saccharopolyspora and Nocardia genera. Along with UDCA, chenodeoxycholic (CDCA), deoxycholic (DCA), cholic (CA), 7-ketodeoxycholic and 3-ketodeoxycholic acids were detected amongst the metabolites by some strains. A strain of Gibberella zeae VKM F-2600 expressed high level of 7ß-hydroxylating activity towards LCA. Under optimized conditions, the yield of UDCA reached 90% at 1g/L of LCA and up to 60% at a 8-fold increased substrate loading. The accumulation of the major by-product, 3-keto UDCA, was limited by using selected biotransformation media.