Eco-friendly and mildly modification of wood cell walls with heat treated wood extracts to improve wood decay resistance

Wood protection using plant-derived extracts has shown some promise but the extracts are often easily leached making them less attractive for long-term wood protection. The potential of extracts from heat treated wood sawdust as a natural substitute for wood preservatives was explored, and a mild enzyme-catalyzed method was used to improve its leaching resistance. Laccase was used to catalyze grafting reactions of extracts from heat treated spruce (Picea asperata Mast.) and larch (Larix gmelinii (Rupr.) Kuzen.). The resulting extracts were screened for antifungal activity and then impregnated into poplar blocks (Populus tomentosa Carr.). Fourier Transform Infrared Spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to characterize extracts reactions. Gas chromatography-mass spectrometry (GC-MS) was used to analyze the grafted compounds. Acetone extracts from both heat treated spruce and larch exhibited good activity against the test fungi. Heat treated spruce and larch acetone extracts grafted on modified poplar and subjected to leaching showed better activity against the white-rot fungus, Trametes versicolor (L. ex Fr.) Quél. than the brown-rot fungus, Gloeophyllum trabeum (Pers.: Fr.) Murr. FTIR and XPS results indicated that heat-treated spruce and larch extracts were grafted on poplar by laccase catalysis. Squalene, 3-hydroxy-4-methoxybenzoic acid, and n-hexadecanoic acid were among those compounds suggested to be grafted. The results suggest that laccase-mediated pre-treatment of plant extracts has the potential to increase resistance to leaching. Trials with additional plant-extracts are recommended.