title: Alkylphenol oxidation with a laccase from a white-rot fungus: effects of culture induction and of ABTS used as a mediator.
abstract: We investigated the potential of the laccase from the white-rot fungus Marasmius quercophilus to transform certain alkylphenols (p-nonylphenol, p-octylphenol and p-t-octylphenol). We tested the reactivity of this enzyme under different conditions: in liquid cultures and using the partially purified laccase with and without 2,2'-azino-bis-3-ehtylbenzothiazoline-6-sulfonicacid (ABTS) as a mediator. The percentage of p-t-octylphenol disappearance in liquid cultures was 69.0 ± 1.5% and 81 ± 5% after a 8-d or 15-d incubation, respectively, with p-nonylphenol, these percentages were 62 ± 4% and 91 ± 6% and with p-octylphenol 37 ± 3% and 65 ± 1% after a 15-d and a 21-d incubations, respectively. Induced pre-cultures were also used to inoculate the liquid cultures to enhance p-octylphenol transformation: the percentages of disappearance were 91.0 ± 0.5% and 97 ± 1% after a 8-d and a 15-d incubation, respectively. Mass spectrometry analysis showed that the products of oxidation of p-octylphenol were dimers with a mass of 411 m/z. Furthermore, we identified a purple compound (m/z 476) formed when ABTS was added to the reaction medium with the purified laccase. This result confirms that, in complex environments such as soils or litters where many molecules can interact with the enzyme substrate or the product of oxidation, laccase activities and those of other phenoloxidases should not be measured with ABTS.
authors.affiliation: Equipe Ecologie Microbienne et Biotechnologies, UMR CNRS IRD 6116, Institut Méditerranéen d'Ecologie et de Paléoécologie, Faculté des Sciences et Techniques de St Jérôme, Université Paul Cézanne, 13397 Marseille, France. a-m.farnet@univ-cezanne.fr
authors.forename: A M
authors.initials: AM
authors.lastname: Farnet
authors.forename: A C
authors.initials: AC
authors.lastname: Chevremont
authors.forename: G
authors.initials: G
authors.lastname: Gil
authors.forename: S
authors.initials: S
authors.lastname: Gastaldi
authors.forename: E
authors.initials: E
authors.lastname: Ferre
mesh_terms: D052160:Benzothiazoles / Q000378:metabolism*; D001673:Biodegradation, Environmental; D042845:Laccase / Q000378:metabolism*; D055433:Marasmius / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D010084:Oxidation-Reduction; D010636:Phenols / Q000378:metabolism*; D013451:Sulfonic Acids / Q000378:metabolism*
chemical_list: D052160:Benzothiazoles; D010636:Phenols; D013451:Sulfonic Acids; C474055:octylphenol; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; C025256:nonylphenol; D042845:Laccase