Mechanism of high antifungal effect of chitosan-metal salts of newly developed wood-preservative on wood.

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In this study, the auther proposed a mechanism of high antifungal effects of chitosan-metal salts (CCS) on wood, which was newly developed wood-preservative in cooperation with Dr.T.Kobayashi, Toyo Wood Preservative Company. The micro-distribution (localization) of the CCS's effective component (copper metal) within the CCS-treated wood specimens, and the fungal behavior of TYP (Tyromyces palustris) within the CCS treated wood blocks in related to the copper-metal distribution by means of SEM-WDXA.As results, the copper metals were firmly bonded to the cell wall surfaces of the JIS wood-specimen even after the JIS-A9201 (1991) weathering treatments, and were localized on the opened lumen surfaces of the tracheids and selectively on the lumen surfaces within the ray parenchyma cells or axial parenchyma cells. When the CCS preservative was applied to the real-scaled timbers, the copper metals were only deposited in the few cell layrs at the surface portion of the treated timber. Nevertheless, the CCS treated woods showed prominently high resistance against the TYP fungal attacks. The TYP hyphae were inhibited selectively in the ray parenchyma cells or axial parenchyma cells, that was clalified by the SEM observation of the TYP rotted woods. Judgging from these evidences, it is clear that the CCS treatment were fundamentally differed from the CCA treatment, that is, the former is "specified cell surface adhere (deposition) type", but the latter is "all cell wall impregnation type". Then, the CCS treatments exhibited the high antifungal effects by means of the least amount of the copper metals in comparison with the CCA treatment, the requried chemicals of the CCS treatment were almost one tenth of the CCA treatment. As conclusion, newly developed CCS wood preservative will be strongly recommended as the post-CCA,because of both sides from safeness and effectiveness.