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Hemicellulosic induction of oxalic acid in Postia placenta
1994 - IRG/WP 94-10060
Most studies suggest that enzymes produced by brown-rot fungi are too large to penetrate sound wood structures, even after decay begins. Thus, nonenzymatic agents have been proposed to initiate brown-rot decay. We have reported that the brown-rot fungus Postia placenta MAD-698 initiates a 2-fold decrease in wood pH within 7 days of colonization which is mediated by production of oxalic acid. Strain ME-20, essentially a non-decay isolate of Postia placenta, does not accumulate oxalic acid when colonizing wood. Our lab has been investigating potential inducers of oxalic acid production, and we have been comparing hemicellulose-like substrates with cellulose-like substrates in liquid culture. Potent inducers of oxalic acid include xylan, glucomannan, chitin, uronic acids, pectin and compounds containing acetyl sidechains. Although cellobiose also induces oxalic acid in MAD-698, utilization of cellulose is considered a relatively late event, therefore not influencing incipient decay. We conclude that oxalic acid induction is an early event in the decay and is initiated by hemicellulosic substrates and by-products.
F Green III, M Larsen, T L Highley


Biological resistance of furfuryl alcohol-treated wood
1992 - IRG/WP 92-3703
Biological resistance of FFA (furfuryl alcohol)-treated wood was investigated in relation to the rise of ASE (anti-swelling efficiency) resulting from the treatment. Sapwood blocks of Japanese red pine, cedar and beech were vacuum-impregnated with various concentrations of aqueous FFA solutions to get the target levels of% (w/w) RL (resin loading). Air-dried blocks were kept in an oven at 120°C for 8 hours to insure the resin formation submerged in water for 1 week to leach away the unpolymerized portion, re-dried, and exposed to decay fungi and termites. The treatment was more effective for pine and cedar than for beech to enhance their decay resistance. As in cases of chemical modification, the treatment was more effective against white-rot fungus Coriolus versicolor than brown-rot Tyromyces palustris. The required RL to reduce the decay by Coriolus versicolor to less than 3% weight loss was ca. 20% for both softwoods but it was ca. 30% for Tyromyces palustris. FFA-treated woods were less attacked by a destructive subterranean termites Coptotermes formosanus and caused their higher mortality with the increase of RL. The pretreatment of boric-acid impregnation yielded the higher ASE and biological resistance at the lower RL than those of sole FFA-treatment. Decay by Coriolus versicolor virtually eliminated even at 0.5% RL for the treated pine and cedar subjected to the boric acid pretreatment.
J Y Ryu, Y Imamura, M Takahashi


Determination of thermal degradation of isothiazolone treated wood
1997 - IRG/WP 97-30154
Wood treated with 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one was the subject of thermal degradation study. The study included burning isothiazolone treated wood under various temperatures with and without oxygen. The result showed that no harmful combustion products, such as polychlorinated dibenzo-p-dioxins, polychlorinated dibenzo-p-furans and polychlorinated biphenyls, were detected. These findings indicate that isothiazolone treated wood can be safely disposed by incineration.
Bing Yu