title: Sterol side-chain cleavage with immobilized Mycobacterium cells in water-immiscible organic solvents.
abstract: The possibility of using whole Mycobacterium sp. cells for the selective degradation of the side-chain of sitosterol in an organic bioconversion medium was investigated. Sterol solubility limits were estimated and free-cell biocompatibility tests were carried out, using a range of water-immiscible solvents. Among these, phthalates exhibited good biocompatibility and sterol-solubilizing capacities. Several organic and inorganic matrices were tested for the immobilization of Mycobacterium sp. cells by surface adhesion. Celite led to the best results, being thus selected for beta-sitosterol side-chain degradation tests in phthalates and in aqueous medium. Cells entrapped in kappa-carrageenan and in polyurethane foams were also used in these tests. The highest degradation activities were obtained with cells immobilized in Celite, with bis(2-ethylhexyl)phthalate as the conversion medium, resulting in molar conversion yields up to 70%, with respect to beta-sitosterol (5 g l-1). Further activity and stability tests revealed that this bioconversion system is markedly temperature dependent.
authors.affiliation: Departamento de Biologia, Universidade de Minho, Braga, Portugal.
authors.forename: A C
authors.initials: AC
authors.lastname: Dias
authors.forename: J M
authors.initials: JM
authors.lastname: Cabral
authors.forename: H M
authors.initials: HM
authors.lastname: Pinheiro
mesh_terms: D000735:Androstenedione / Q000378:metabolism; D001673:Biodegradation, Environmental; D001709:Biotechnology; D007692:Diatomaceous Earth; D008855:Microscopy, Electron, Scanning; D009161:Mycobacterium / Q000378:metabolism* / Q000648:ultrastructure; D012855:Sitosterols / Q000378:metabolism; D012995:Solubility; D012997:Solvents; D013261:Sterols / Q000378:metabolism*; D013696:Temperature; D014867:Water
chemical_list: D012855:Sitosterols; D012997:Solvents; D013261:Sterols; D014867:Water; D000735:Androstenedione; C025473:gamma-sitosterol; D007692:Diatomaceous Earth