Initial stages of Fagus sylvatica wood colonization by the white-rot basidiomycete Trametes versicolor: Enzymatic characterization

The initial stages of wood colonization and degradation by the white-rot Trametes versicolor have been investigated. T. versicolor was grown on Fagus sylvatica wood chips under solid-state fermentation in the presence of malt agar. The beginning of the colonization process was not associated with peroxidases production or hydrolytic activity. In contrast, a sharp induction of laccase expression was observed during the first colonization days. This induction is not due solely to fungal growth on wood chips since similar data were obtained in the presence of biocide (propiconazole)-treated wood, suggesting that enzyme production is due at least in part to the mycelium surrounding wood chips using nutrients from malt agar medium. Laccase production correlated with wood acetone extractives degradation, in particular with the oxidation of catechin, a major compound of beech extracts. In complementary experiments, wood-extracted laccases were shown to be active with wood acetone extracts and pure catechin. Furthermore, wood extractives induced laccase expression. Taken together, these data suggest that the initial stages of wood colonization on malt agar by T. versicolor correlate with wood extractives degradation requiring laccase activity, whereas the other wood-degrading systems (peroxidases and polysaccharides hydrolases) are still repressed.