title: Selection of Mycobacterium sp. strains with capacity to biotransform high concentrations of beta-sitosterol.
abstract: In this work, phytosterol-biotransforming strains were selected from Mycobacterium sp., using a high concentration of beta-sitosterol. The selection was made by culturing the strains in a medium enriched with 14 g beta-sitosterol/l as the unique source of carbon. During 2 months, the bacterial cultures were transferred successively. The extraction of the biotransformation products was made with methanol and ethyl acetate. The qualitative and quantitative analysis was made by means of thin-layer chromatography, gas-liquid chromatography (GLC) and GLC-mass spectrometry. Under these conditions, it was observed that after seven transfers, the strains MYcobacterium sp. MB-3683 and the Mycobacterium fortuitum B-11045 increased their biotransformation capacity from 20% to 64% and from 34% to 55%, respectively. The products in the highest proportion identified for each trial were androstenedione and androstadienedione. The results suggest that the high substrate concentration could be a selective mechanism to obtain strains more efficient in the biotransformation of beta-sitosterol into steroidal bases.
authors.affiliation: Department of Microbiology, Faculty of Biological Sciences, University of Concepción, Chile. mavidal@udec.cl
authors.forename: M
authors.initials: M
authors.lastname: Vidal
authors.forename: J
authors.initials: J
authors.lastname: Becerra
authors.forename: M A
authors.initials: MA
authors.lastname: Mondaca
authors.forename: M
authors.initials: M
authors.lastname: Silva
mesh_terms: D000730:Androstadienes / Q000737:chemistry / Q000378:metabolism; D000735:Androstenedione / Q000096:biosynthesis / Q000737:chemistry; D002855:Chromatography, Thin Layer; D008401:Gas Chromatography-Mass Spectrometry; D009161:Mycobacterium / Q000145:classification / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular; D012855:Sitosterols / Q000378:metabolism* / Q000493:pharmacokinetics
chemical_list: D000730:Androstadienes; D012855:Sitosterols; C006573:1,4-androstadiene-3,17-dione; D000735:Androstenedione; C025473:gamma-sitosterol