1c:I[419806,["/_next/static/chunks/bb923814e1f4d2e9.js","/_next/static/chunks/dd3ee9f5b7716ca6.js","/_next/static/chunks/4204a0ae82542ca8.js","/_next/static/chunks/1270dead247da766.js","/_next/static/chunks/6e1aa89a642f40be.js","/_next/static/chunks/cd5e572bc3e4eb92.js","/_next/static/chunks/8ffd0b71567920d8.js","/_next/static/chunks/67ea6dfd21f16c5f.js","/_next/static/chunks/24eb4379f68013fd.js","/_next/static/chunks/b8cd775ffdf935bd.js","/_next/static/chunks/983103cd9eb7b428.js","/_next/static/chunks/d4ac9dcf27f6ff52.js","/_next/static/chunks/294b9525248c8e5f.js"],"default"] 1d:T466,In timber infested by brown-rot fungi, a rapid loss of strength is attributed to production of hydroxyl radicals (HO^.). The hydroxyl radicals are produced by the Fenton reaction [Fe(II)/H₂O₂], but the pathways leading to Fe(II) and H₂O₂ have remained unclear. Cellobiose dehydrogenase, purified from cultures of Coniophora puteana, has been shown to couple oxidation of cellodextrins to conversion of Fe(III) to Fe(II). Two characteristics of brown rot are release of oxalic acid and lowering of the local pH, often to about pH 2. Modelling of Fe(II) speciation in the presence of oxalate has revealed that Fe(II)-oxalate complexes are important at pH 4-5, but at pH 2 almost all Fe(II) is in an uncomplexed state which reacts very slowly with dioxygen. Diffusion of Fe(II) away from the hyphae will promote conversion to Fe(II)-oxalate and autoxidation with H₂O₂ as product. Thus the critical Fe(II)/H₂O₂ combination will be generated at a distance, enabling hydroxyl radicals to be formed without damage to the hyphae.1e:T49b,Low concentrations of H 2 O 2 and Fe ++ caused rapid weight loss of wood of sweetgum and loblolly pine. The degree of polymerization of cellulose in treated woods decreased rapidly at low weight loss and then diminished gradually. The alkali solubility of exposed woods increased rapidly at low weight loss and was inversely related to the degree of polymerization. The H 2 O 2 -Fe system solubilized hemicelluloses of both woods more readily than cellulose. Lignin of sweetgum, but not pine, was changed so that it was solubilized by strong acid hydrolysis. The optimal pH for weight loss was about 3.3 for sweetgum and 3.0 for pine. Wood of both species absorbed much of the available Fe from solution. The literature suggests that brown-rot is oxidative rather than being strictly hydrolytic. The H 2 O 2 -Fe ++ system oxidizes cotton cellulose, and it essentially reproduced in wood and wood cellulose, characteristics of brown-rot basidiomycetes. These fungi produce H 2 O 2 from native substrates in wood (Koenigs, 1974) and the optimal pH for degradation. Thus, it is proposed that these fungi may attack cellulose and partly decay wood via an H 2 O 2 -Fe ++ system.1f:T41e,Three white-rot fungi, P ~l !~p o r ~i s oersicolor, Ganoclerma ap)))lanatr~nl, and Peniophora "C," produce an adaptive cellulase conlplex that can degrade both so111ble cellulose (C,) and microcrystalline cellulose ( C , ), a highly ordered form of cellnlose.Production of C, m~cl C, by thr white-rot fungi was represscd by sinlple sugars.CI-llulase preparations from three 1)ron.n-rotfungi, Poria ntonticolu, Ler~tinus lel~iderrs, and Lerlzites trabeu, exhi11itc:d only C , activity; ~~~icrocrystallinc celll~lose was not significantly degraded.Contrary to the celllilase ( C , ) of thr whit(--rot fungi, that of the brown-rot fungi apparently is constituti~e, since activity was a l l u n d a ~~t in c ~~l t i ~r e s with sirnplr sugars or \vith non-cell~~losic polysaccharities as the sole sotlrce of carbon.This work disclosed no differences between the.cellulase-indl~cing effects of hard~voods versus those of soft\voods that lnight help explaiil the preference of white rotters for hard\voods and brown rotters for oftw woods.Additionul keywords:

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