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In this study, we describe the biochemical features and the ability of a new laccase isoform from a Marasmius quercophilus strain collected on evergreen oak litter to transform various aromatic compounds. This laccase, induced with ferulic acid, exhibits interesting enzymatic properties, such as great thermal stability at 30 and 40 • C (24 h), no inhibition with EDTA, Cystein or SDS. These biochemical features are quite different from those observed with the laccase of another M. quercophilus strain collected in a different area of the South of France. Thus, this study shows the degree of variation in the properties of this enzymatic system within the same species. Furthermore we demonstrate that several natural aromatic compounds were transform leading to polymerization. The transformation of chlorophenols such as 2-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol is also observed without adding mediators (2,2-azinobis(3-ethylbenzthiazoline-6-sulfonate) or 1-hydroxybenzotriazole) to the reaction mixture. Thus, the mediators used do not seem to extend the substrate range for this laccase under these experimental conditions.

Marasmius quercophilus is a white-rot fungus involved in carbon recycling in Mediterranean ecosystems because of its laccase production. Here we described the effect of metal ions and halide salts, on laccase activity in order to point out the action of such environmental pollutants on this enzyme of major importance. Furthermore we tested organic solvent effects on laccase reaction since reaction mixture including solvent can be used in the transformation of xenobiotics. In the case of metal ions, we found that chloride ions were responsible for inhibition while CuSO(4) and MnSO(4) enhanced laccase activity. When halides were tested, we showed the following degree of inhibition: F(-)>Cl(-)>Br(-). Furthermore we found that I(-) was oxidized by laccase with I(2) as the product of the reaction. With ABTS, 50% of the laccase activity remains for solvent concentration ranging from 40% to 60% depending on the solvent used while with syringaldazine solvent concentration ranged from 50% to 70%. The organic solvent effects observed were probably a result of enzyme denaturation and of both enhancement of oxidised product solubilisation and of substrate solubilisation (for syringaldazine). These results show that laccase from M. quercophilus is not rapidly inhibited by certain environmental pollutants which sustains its role in carbon turnover under pertubation. However the strong effect of chloride ion on laccase activity should be further investigated with in situ studies since this could drastically influence carbon recycling in litters from Mediterranean littoral locations.

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Various methods of suberin extraction have been used in order to identify monomers of this complex polymer. Pre-extraction of waxes has allowed us to identify for the first time 3-friedelanol as a terpen from cork. Moreover, the wax chemical composition found here varied from previous results since cerin was not identified while friedelin and betulin were. Three fractions were obtained: a polymeric, a monomeric and a low molecular weight fraction, the last of which has never before been described. 2,6-heptanediol was found to be the main compound of this fraction. Furthermore, depolymerisation at room temperature gives the same yields as those obtained at reflux, defining an easier and cheaper methodology.

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