Beech wood (Fagus sylvatica) modified with the textile finishing agent 1,3 dimethylol-4,5-dihydroxyethylen urea (DMDHEU) has shown to improve durability against the white-rot fungus Trametes versicolor. In a mini-block test, the weight loss over eight weeks of incubation decreased with increasing weight percent gain (WPG) of DMDHEU. At 25% WPG, no significant weight loss was observed, while untreated beech wood lost 37% of its initial weight under the same conditions. This increase in resistance was shown not to be caused by a biocidal effect of monomeric DMDHEU: the growth of T. versicolor and Coniophora puteana was not significantly reduced, when DMDHEU was added to sterile malt agar plates in concentrations of up to 10%. Poria placenta was not negatively affected up to a DMDHEU concentration of 5%. A solid state fermentation experiment was performed with T. versicolor on milled untreated and DMDHEU modified wood in order to determine the production of extra-cellular protein and the activity of wood-decaying enzymes. T. versicolor was not able to grow on wood treated to the highest WPG (14.9%). The activity of ligninolytic enzymes (laccase, manganese peroxidase) was highest at 7.9% WPG compared to the untreated control and 2.8% WPG. The overall production of hydrolytic enzymes was low in all cases and a clear distinction between untreated and modified wood was not possible.

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