No abstract

The strain of Mycobacterium sp. VKM Ac-1817D forms 9alpha-hydroxy-androst-4-ene-3,17-dione (9-OH-AD) as a major product from sitosterol. The formation of 9-OH-AD was accompanied with its partial destruction due to residual steroid-1-dehydrogenase (St1DH) activity. The activity was found to be induced by androst-4-ene-3,17-dione (AD), while other intermediates of sitosterol oxidation did not influence 1(2)-dehydrogenation. The enzyme is located mainly in the cytosolic fraction. The cytosolic St1DH (dimer, M (r) approximately 58 kDa) was partially purified by ammonium sulfate fractionation, ion-exchange chromatography on DEAE-Sepharose and Phenyl-Sepharose, and gel filtration on Bio-Gel A-0.5M. It expressed the St1DH activity toward both AD and 9-OH-AD.

In total, 481 fungal strains were screened for the ability to carry out 7(a/b)-hydroxylation of dehydroepiandrosterone (DHEA, 3b-hydroxy-5-androsten-17-one). Representatives of 31 genera of 15 families and 9 orders of ascomycetes, 17 genera of 9 families and 2 orders of zygomycetes, 2 genera of two families and 2 orders of basidiomycetes, and 14 genera of mitosporic fungi expressed 7(a/b)-hydroxylase activity. The majority of strains were able to introduce a hydroxyl group to position 7a. Active strains selectively producing 3b,7a-dihydroxy-5-androsten-17-one were found among Actinomucor, Backusella, Benjaminiella, Epicoccum, Fusarium, Phycomyces and Trichothecium, with the highest yield of 1.25 and 1.9 g L (1 from 2 and 5 g L (1 DHEA, respectively, reached with F. oxysporum. Representatives of Acremonium, Bipolaris, Conidiobolus and Curvularia formed 3b,7b-dihydroxy-5-androsten-17-one as a major product from DHEA. The structures of the major steroid products were confirmed by thin-layer chromatography (TLC), gas chromatography (GC), mass spectra (MS), and 1 H-NMR analyses.

Biotransformation of 1-benzoylindole (BI) by the strains Aspergillus flavus VKM F-1024 and Aspergillus oryzae VKM F-44 was studied. The major metabolites isolated were identified as 4-hydroxyindole (4-HI), 5-hydroxyindole (5-HI), 4-hydroxy- -benzoylindole, 4-hydroxy-1-(4'-hydroxy)-benzoylindole and indole. The structure of the metabolites was determined by mass spectrometry and proton nuclear magnetic resonance spectroscopy. The pathways of BI metabolism via initial monohydroxylation at C-4 and C-5 followed by cleavage of the benzoyl substituent to yield 4-HI and 5-HI were proposed. Indole was formed as a by-product, and its role as a potent inhibitor of BI hydroxylation at C-4 and C-5 is discussed.

Soybean extract residue (scum), a waste of soybean oil production, was examined as a raw material for C 17 -ketosteroid production. As a model process, its bioconversion to 9α-hydroxyandrost-4-ene-3,17-dione (9-OH-AD) by Mycobacterium sp VKM Ac-1817D was studied. The content of transformable sterols (sitosterol, stigmasterol and campesterol) in scum was estimated at ∼14%. The bioconversion of scum to 9-OH-AD was characterized by a long lag-period (300-350 h) followed by 9-OH-AD accumulation. The microbial or chemical elimination of fatty non-identified components resulted in sterol-enriched scum preparations. Effective conversion of these preparations by Mycobacterium sp was demonstrated: 9-OH-AD molar yield ∼65% was reached at 60 h from the scum preparation containing 10 g dm −3 transformable sterols. The process productivity was comparable with that for high quality-sitosterol of wood origin (tall-oil sitosterol).