Wood degradation by white rot basidiomycetes and production of simple phenolic compounds

White rot fungi degrade and mineralize lignin through secretion of strong oxidative ligninolytic enzymes, preventing accumulation of deadwood organic matter. Due to the specific structures, different lignolytic enzymes has different mechanism in lignin degradation/oxidation, producing many natural secondary metabolites, including phenolic compounds (PC). PC in soil may regulate nutrient cycling in forest ecosystems by controlling the pool and form of nutrients available for trees. This work explores the PC produced at different times by nine main decay fungal species, belonging to Heterobasidion and Armillaria genera, before and after their inoculation and growth on silver fir (Abies alba Mill.) sawdust, as axenic culture system, under controlled conditions. A total of 81 samples (three replicates for each fungal species and other three replicates kept as a control) were analysed using high-performance liquid chromatography coupled to a hybrid quadrupole-orbitrap mass spectrometer. Eighteen PC, including simple phenols, alkylphenyl alcohols, hydroxybenzoketones, hydroxycinnamaldehydes, hydroxybenzaldehydes, hydroxyphenylacetic acids, hydroxycinnamic acids, hydroxybenzoic acids and hydroxycoumarins were detected. In particular, coniferyl alcohol, ferulic acid, p-coumaric acid, acetovanillone, vanillic acid, etc. showed a decreasing trend during degradation process, by contrast an accumulation trend was observed for protocatechuic acid, syringic acid and scopoletin. These results suggested different strategies of silver fir lignin degradation by selected fungal species. PCA revealed a good differentiation between PC and the activity of nine fungal species along the three times of silver fir sawdust degradation. The nine fungal species have different climate requirements which imply different PC production under different global warming scenarios.