This paper examines research and hypotheses that have been developed over several years on wood degradation mechanisms. This information is combined with new data and analyses to explain why wood decay patterns caused by brown-rot fungi and specific types of white-rot fungi are different. New data, including work with both biomimetic studies on low molecular weight compounds, degradative enzymes, and wood decayed by brown- and white-rot fungi support a role for these compounds, which results in different types of fungal decay. Specifically the presence or absence of low molecular weight phenolate compounds that bind and reduce iron to generate oxygen radicals is related to brown-rot, as well as “selective white-rot” decay of wood. Free radicals generated by the low molecular weight systems are important in opening up the structure of wood in advance of, or concurrent with, enzymatic attack in both brown-rot and selective white-rot decay. “Simulataneous white-rot” fungi do not typically posses a highly expressed low molecular weight phenolate system and this may help to explain the erosion pattern of decay observed in decay by this type of white-rot. New analytical techniques including Pyrolysis-molecular beam mass spectrometry and 13C-labeled tetramethylammonium hydroxide thermochemolysis are used to provide new information, particularly regarding how lignin is attacked, and either repolymerized or solubilized depending on the type of fungal attack. Discussion of the mechanisms involved, and how new wood protection schemes may be developed to exploit these mechanisms is reviewed.

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