Enzymatic and non-enzymatic wood-decay pathway characterization in Fomitiporia mediterranea

Among grapevine trunk diseases-related fungi, the basidiomycete Fomitiporia mediterranea (Fmed) is responsible for wood-decay in Vitis vinifera, showing an intermediate behaviour between brownand white-rot fungi. Nowadays, it is widely accepted that, in brown-rot fungi, wood decay is the result of synergic enzymatic and non-enzymatic degrading action. In the first one, enzymatic action, laccases and manganese peroxidases (MnP) play a major role in catalysing lignin degradation, splitting C?-C?, ?-aryl, C1-C? and aromatic C-C bonds. In the second one, non- enzymatic action, the lignin/cellulose degradation is attributed to the non-enzymatic Fenton/Haber Weiss pathway, generating hydroxyl radicals within the wood cell, also thanks to Fe oxidation. Because low-molecular weight (LMW) iron-binding compounds mediate this wood degradation, the mechanism has been named "chelator-mediated Fenton" (CMF) reaction. Since it is still not clear if Fmed has both mechanisms of lignin/cellulose degradation (enzymatic and CMF reactions), these two pathways were evaluated screening 13 Fmed strains, assaying: i) laccase and MnP activity; ii) the strains capability to produce LMW iron-binding compounds, ferrous-iron (Fe2+) accumulation and the consequent production of hydroxyl radicals.