title: Bioconversion of (+)-valencene in submerged cultures of the ascomycete Chaetomium globosum.
abstract: Submerged cultures of the ascomycete Chaetomium globosum oxidised the exogenous sesquiterpene (+)-valencene to nootkatone via the stereoselective generation of alpha-nootkatol. Inhibition experiments suggested that the first introduction of oxygen, the rate-limiting step of the bioconversion, may have been catalysed by a cytochrome-P450-monooxygenase. However, nootkatone was not the final metabolite: further flavour-active and inactive, non-volatile oxidation products were identified. (+)-Valencene and the flavour-active mono-oxyfunctionalised transformation products, alpha-nootkatol, nootkatone, and valencene-11,12-epoxide accumulated preferably inside the fungal cells. Di- and poly-oxygenated products, such as nootkatone-11,12-epoxide, were found solely in the culture medium, indicating an active transport of these metabolites into the extracellular compartment during (+)-valencene detoxification. These metabolic properties may have contributed to the high tolerance of the fungus towards the exogenous hydrocarbon.
authors.affiliation: Zentrum für Angewandte Chemie der Universität Hannover, Institut für Lebensmittelchemie, Hannover, Germany.
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Kaspera
authors.forename: Ulrich
authors.initials: U
authors.lastname: Krings
authors.forename: Tsevegsuren
authors.initials: T
authors.lastname: Nanzad
authors.forename: Ralf G
authors.initials: RG
authors.lastname: Berger
mesh_terms: D001709:Biotechnology / Q000379:methods; D002597:Chaetomium / Q000254:growth & development* / Q000378:metabolism*; D003470:Culture Media; D004852:Epoxy Compounds / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction; D000081223:Polycyclic Sesquiterpenes; D012717:Sesquiterpenes / Q000737:chemistry / Q000378:metabolism*
chemical_list: D003470:Culture Media; D004852:Epoxy Compounds; D000081223:Polycyclic Sesquiterpenes; D012717:Sesquiterpenes; C041991:Nootkatol; C050302:nootkatone