In order to protect non-durable wood species against microbial deterioration one alternative is modified wood. The lowered equilibrium moisture in modified wood is believed to be one of the main mechanisms against wood decaying fungi. But moisture is most likely not the only protection mechanism. The aim of this study was to profile Postia placenta colonization during 20 weeks in furfurylated, acetylated and thermally modified Scots pine sapwood. Two reference preservatives (CC and CCA) and control were included for comparison. After 20 weeks the lowest mass loss was found for acetylated wood and CCA. The three wood modification systems and CCA had lower wood moisture content than the CC and control. The fungal DNA data did mirror the mass loss data well; the exception was unexpected high levels in acetylated wood. The gene expression studies of selected genes support previous studies, i.e. indications of increased expression of genes related to oxidative metabolism and reduction of genes related to the enzymatic breakdown of polysaccharides in modified wood. Interestingly, microscopy revealed calcium oxalate crystals in acetylated wood, starting 5 weeks after incubation and thermally modified wood after 17 weeks. The crystals are believed to play a part of pH regulation, to reduce pH to levels where the chelator mediated Fenton system could be active.
Keywords: Chelator Mediated Fenton (CMF) degradation, enzymatic degradation, oxidative degradation, brown rot, fungal colonization
Authors
Pilgård A.
Research Institutes of Sweden, Bioeconomy/Biobased materials, Borås, Sweden
Technische Universität München, Holzforschung München, München, Germany
Schmöllerl B.
Holzforschung Austria, Wien, Austria
Risse M.
Technische Universität München, Holzforschung München, München, Germany
Fossdal CG
Norwegian Institute of Bioeconomy, Ås, Norway
Alfredsen G.
Norwegian Institute of Bioeconomy, Ås, Norway
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