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Involvement of hydrogen peroxide in wood decay by brown-rot and white-rot fungi
1985 - IRG/WP 1256
To gain further understanding of the role of H2O2 in wood degradation by brown- and white-rot fungi, we studied the following: (a) extracellular H2O2 production, (b) effect of various hydroxyl radical (·OH) and singlet O2 (1O2) quenching agents on wood and cellulose degradation, (c) intracellular H2O2 production and catalase activity, and (d) cytochemical localization of H2O2 with diaminobenzidine (DAB) during wood degradation. Extracellular H2O2 detection varied with the growth media and chromogen. The chromogen 2,2'-azino-di-(3-ethyl benzthiazoline-6-sulphonic acid) (ABTS) was more sensitive than o-dianisidine. Extracellular H2O2 was not detected in half of the brown-rot fungi. One white-rot fungus did not produce detectable amounts of H2O2. ·OH and 1O2 quenching agents generally did not inhibit decay of wood or decomposition of cellulose by either brown- or white-rot fungi. DAB did not detect the presence of H2O2 within or outside cells of the brown-rot fungus, Poria placenta. Nor was H2O2 -generating activity detected in sonicated extracts of this fungus. With the white-rot fungus, Coriolus versicolor, H2O2 occurred predominantly in the periplasmic space, but also in the cytoplasm and hyphal sheath. Sonicates of Coriolus versicolor contained H2O2 -generating activity. These observations provide further support for H2O2 involvement in degradation of wood by white-rot fungi, but raise doubts concerning its participation in wood degradation by brown-rot fungi.
T L Highley, L L Murmanis

Effect of angle of exposure on degradation of radiata pine during weathering trials
1988 - IRG/WP 2301
The importance of angle of exposure on the degree of weathering of materials has not been adequately resolved. In conventional tests, specimens are exposed at an angle of 45° facing the equator, but more recently experiments on polymeric materials have suggested that an angle of 0° may be preferable since this angle maximises levels of received ultra-violet radiation. In this paper the degradation of Radiata pine (Pinus radiata D. Don) during weathering was assessed at 5 angles of exposure (0°, 45°, 60°, 70°, 90°) over 50 days by measuring changes in weight and chemical composition. In order to confirm previous observations measurements of received ultra-violet radiation (< 320 nm) at these angles of exposure were also made using polysulphone polymer film dosimeters. Roth weight loss and chemical data indicate that degradation of Radiata pine during weathering was negatively correlated (p < 0.001) with increasing angle of exposure. The implications of these findings for the conduct of weathering trials are discussed.
P D Evans

Relationship between degradation of wood, cellulose or lignin-related compounds and production of hydroxyl radical or accumulation of oxalic acid in cultures of brown-rot fungi
1994 - IRG/WP 94-10062
The degradation activities of brown rot fungi against wood, cellulose, and lignin-related compounds were measured in cultures containing glucose or wood as a carbon source. Also the activities of one-electron oxidation and hydroxyl radical production and the amount of oxalic acid present in the cultures were measured. The degradation activities of the fungi against wood, crystalline cellulose and the lignin model compounds were in direct proportion to the activities of one-electron oxidaton and hydroxyl radical production. The amount of oxalic acid win the cultures was inversely proportional to those activities and oxalic acid was almost not detectable in the cultures in which wood was actively degraded. On the basis of these results it is concluded that one-electron systems including hydroxyl radicals play important roles in the initial stage of wood decay by brown rot fungi and degrade oxalic acid produced by the fungi to trace amounts.
S Itakura, T Hirano, H Tanaka, A Enoki

Fungal Attack on Lignin and Cellulose: Elucidation of Brown- and White-Rot Mechanisms Comparing Biomimetic and In-Vivo Degradation Patterns
2010 - IRG/WP 10-10714
This paper examines research and hypotheses that have been developed over several years on wood degradation mechanisms. This information is combined with new data and analyses to explain why wood decay patterns caused by brown-rot fungi and specific types of white-rot fungi are different. New data, including work with both biomimetic studies on low molecular weight compounds, degradative enzymes, and wood decayed by brown- and white-rot fungi support a role for these compounds, which results in different types of fungal decay. Specifically the presence or absence of low molecular weight phenolate compounds that bind and reduce iron to generate oxygen radicals is related to brown-rot, as well as “selective white-rot” decay of wood. Free radicals generated by the low molecular weight systems are important in opening up the structure of wood in advance of, or concurrent with, enzymatic attack in both brown-rot and selective white-rot decay. “Simulataneous white-rot” fungi do not typically posses a highly expressed low molecular weight phenolate system and this may help to explain the erosion pattern of decay observed in decay by this type of white-rot. New analytical techniques including Pyrolysis-molecular beam mass spectrometry and 13C-labeled tetramethylammonium hydroxide thermochemolysis are used to provide new information, particularly regarding how lignin is attacked, and either repolymerized or solubilized depending on the type of fungal attack. Discussion of the mechanisms involved, and how new wood protection schemes may be developed to exploit these mechanisms is reviewed.
V Arantes, B Goodell, A M F Milagres, Yuhui Qian, T Filley, J Jellison, S Kelley

Micromorphological and chemical characteristics of waterlogged archaeological bamboos excavated from the Yellow Sea
2012 - IRG/WP 12-10785
Bamboos have widely used as documentation material in Far Eastern countries such China, Korea and Japan. In particular, bamboo slips as documentation material were extensively used even after the wide spread of paper in those countries. A large number of bamboo slips have been excavated from the shipwreck since 2009 in Korea. Understanding the cause of deterioration of ancient bamboos is crucial for developing technology of restoring artifacts of historical and cultural value. When compared to archaeological wood, it is very seldom to find the research work on the ancient bamboo artifacts. In particular, examinations on the waterlogged archaeological bamboo works are rare. The work presented is on bamboo slips which were excavated from a shipwreck. Various microscopical techniques and chemical methods were employed to characterize the waterlogged archaeological bamboos which had been submerged for more than 800 years in the ocean of Yellow Sea. Erosion bacteria were the most important degraders of waterlogged archaeological bamboo cell walls with occasional TEM images indicating presence also of bacterial tunneling. Chemical analyses showed that cellulose and hemicelluloses were extensively degraded with an indication that lignin was also degraded to some extent.
Mi Young Cha, Yoon Soo Kim

Effect of medium-term degradation of beech wood by erosive (Phanerochaete chrysosporium) and lignin-selective (Ceriporiopsis subvermispora) strains of white rot fungi on its selected physical properties
2004 - IRG/WP 04-40292
At the Faculty of Wood Sciences and Technology a fungal delignification of normal and tension beech wood by erosive and lignin-selective strains white-rot fungi has been studied. The pre-treatment of both kind of wood samples was accompanied by partial delignification and apparent changes of their physical properties influencing the polar liquids penetration.
R Solár, S Kurjatko, M Mamonová, J Hudec

A discussion of current theories concerning CCA fixation
1983 - IRG/WP 3238
The understanding of the fixation mechanism of CCA and related preservatives in wood has been greatly improved by a significant series of recent scientific papers. In view of recent concerns in New Zealand regarding the long-term efficacy of CCA in high decay-hazard situations, it was considered appropriate to review this recent work and to contrast it with theories presented by previous workers.
D V Plackett

Cytochemical localization of hydrogen peroxide in brown rot fungus Tyromyces palustris by cerium chloride technique
1999 - IRG/WP 99-10299
Cerium chloride (CeCl3) was used to localize H2O2 cytochemically for studying relationship between ultrastructural and functional characteristics of cellulose degradation by brown rot fungi. This technique proved very useful in localizing discrete electron-densereactionproducts at high resolution with minimal nonspecific deposition. The cytochemical localization of extracellular H2O2 by CeCl3 using TEM demonstrated the presence of H2O2 within the fungal hyphae. Furthermore, our results give an indication of the diffusion of extarcellular H2O2 from brown-rot decay fungi into the intact wood cell walls in the early stages of decay.
Yoon Soo Kim, Seung-Gon Wi

Lignin degradation by wood-degrading fungi
1986 - IRG/WP 1310
The wood-degrading white-rot fungus Phanerochaete chrysosporium, has been the subject of intensive research in recent years and, based upon isolation of the extracelluar enzyme ligninase, major advances have now been made toward elucidating the mechanism by which this fungus degrades lignin. From these developments, a model emerges which could explain the process by which wood-degrading fungi in general, attack lignin.
P J Harvey, H E Schoemaker, J M Palmer

Contribution of wood components on the absorption of copper amine
2000 - IRG/WP 00-30216
The contribution of wood components on the absorption of copper amine was investigated. Holocellulose, lignin and xylan absorbed significant amount of copper. The amount of copper absorbed by cellulose was almost negligible. The removal of extractive also decreased the amount of copper absorption. This study clearly indicates the importance of lignin, hemicellulose in the absorption of copper amine in wood.
D P Kamdem, Jun Zhang

Defining fungal decay types - Final proposal
1988 - IRG/WP 1355
The term soft rot is proposed for all forms of decay caused by Ascomycetes and non-basidiomyceteous Fungi imperfecti. The terms brown rot and white rot should be used only for decay caused by Basidiomycetes. Brown rot is characterized by extensive depolymerization of the cellulose and limited lignin degradation. White rot is characterised by significant degradation of the lignin component in wood.
T Nilsson

Immunogold labelling of size marker proteins in brown rot-degraded pine wood
1990 - IRG/WP 1428
Pine wood degraded by Fomitopsis pinicola was infiltrated with a mixture of ovalbumin (45 kDa) and myoglobin (16.7 kDa). After crosslinking of the proteins with glutaraldehyde and preparation for electron microscopy ultrathin sections were labeled with gold-conjugated antibodies. Simultaneous labeling of both proteins on the same section showed that at 50-70% weight loss ovalbumin did not penetrate the brown rot-degraded wood cell walls at all, while partial penetration was observed with myoglobin. Considerable areas of the wood cell walls were not penetrated even by the small myoglobin molecules, although extensive degradation was evident. The results suggest that not only the initial brown rot attack, but all chemical reactions taking place inside the wood cell walls, depolymerization of cellulose to soluble oligosaccharides as well as lignin modification, are caused by a low molecular weight fungal agent.
E Srebotnik, K Messner

Immunogold localisation of catalytic domain of endocellulase in the cellulosic substrates
1997 - IRG/WP 97-10205
The reaction of catalytic domain of endocellulase on the cellulosic substrates was visualised by using immunogold labelling procedures to obtain a better understanding of the mechanism of enzymatic cellulose hydrolysis. Polyclonal antibody was produced against the catalytic domain of endo-l, 4-ß-glucanase (EGI) from a ruminal anaerobic bacterium Ruminococcus albus F-40. Immuno-TEM works showed the positive labelling of polyclonal antibody of catalytic domain endocellulase on the cellulosic structures. Gold particles occurred mostly in the disrupted terminal areas of cellulose microfibrils. In contrast, gold labelling on the central part of microfibril was not so much distributed as that in the terminal part. The catalytic domain of endocellulase was presented mainly in the outer membrane of bacterial cells, suggesting that this enzyme is a cell surface protein serving to degrade the cellulosic substrates. The labelling density between the whole endocellulase and the catalytic domain of endocellulase was different. Micromorphological characteristics of cellulose degradation by this bacterium were also examined by SEM and TEM.
Yoon Soo Kim, Seung-Gon Wi, Kyu Ho Myung, K Ohmiya, S Karita

Ultrastructure of degraded, CCA-treated Pinus radiata wood from a marine pile
1990 - IRG/WP 1461
During an inspection of marine piles, 12 years after installation, severe degradation was noted on one of them in the vicinity of a corroded eye-bolt. The wood was dark brown in colour and tended to crumble easily. Wood fragments were examined by light microscopy and scanning and transmission electron microscopy and were also analysed for carbohydrates and lignin. Light microscopy showed numerous cracks in tracheid walls resulting in delamination at middle lamella - S1 and S1 - S2 junctures and also in fractures across the tracheid wall. Chemical analysis showed extensive losses in hemicelluloses and also losses in cellulose. Observations with polarised light microscopy supported the data from chemical analysis on cellulose degradation. Although presence of microbial flora in the lumen of wood cells was revealed by scanning electron microscopy, transmission electron microscopy showed only occasional soft rot decay zones in the S2 layer. We suggest that the degradation of Pinus radiata wood cell wall is primarily due to chemical attack, fungal decay playing a minor role.
A P Singh, M E Hedley

Identification of terminal structures in cellulose degraded by the brown-rot fungus Postia placenta
1989 - IRG/WP 1389
To gain insight into the biochemical mechanism employed by brown-rot fungi to depolymerize cellulose, we identified the end-groups of chemically pure cellulose that had been depolymerized by the brown-rot fungus, Postia placenta. The depolymerized cellulose was acid hydrolyzed and the anion fractions isolated by ion chromatography. Sugar acids were identified by gas chromatographic and mass spectrocopic analysis. Cellulose degraded by Fenton&apos;s reagent (H2O2/Fe2+) was also analyzed. The two systems generated the same sugar acids but not in the same quantities. The acids identified include glyceric and erythronic, indicating oxidative cleavage of the vicinal diol carbon-carbon bonds within glucosyl residues in the cellulose polymer. Gluconic and arabonic acids were also identified as major products. No uronic acids were produced in either systems.
T K Kirk, T L Highley, R E Ibach, M D Mozuch

Natural weathering of wood in a sunny climate effects on surface chemistry and paint adhesion
1997 - IRG/WP 97-20109
Radiata pine veneers and blocks were exposed to natural weathering under Australian summer conditions over a period of 30 days. Infrared spectroscopy revealed that there was perceptible surface delignification after 4 hours exposure, substantial surface delignification after 3 days exposure and almost complete surface delignification after 6 days. Viscometry determinations on holocellulose samples from weathered veneers and unweathered controls indicated significant depolymerisation of cellulose after short periods of weathering. A tape test was used to assess the adhesion of acrylic latex primers to weathered blocks. The adhesion of exterior acrylic primers decreased on weathered wood surfaces and was significantly lower on specimens that were weathered for 5 to 10 days. An oil-modified acrylic primer showed greater adhesion to weathered wood surfaces. Primer adhesion was lower on weathered radial surfaces than on similarly exposed tangential surfaces. The practical implications of these findings for the coating of exterior wood with acrylic latex primers and the development of photoprotective treatments for wood are discussed briefly.
P D Evans, P D Thay, K J Schmalzl

Correlation between changes in colour and chemical composition during photo-degradation of wood surfaces
2005 - IRG/WP 05-40301
Changes in colour of wood (yellowing) during photo degradation or weathering reflect chemical changes in wood. Therefore, the relationship between changes in chemical composition and CIELAB colour parameters is very important to characterize photodegradation of lignocellulosic surfaces. In this study, the changes in chemical composition and yellowing due to photo-degradation was studied by exposing wood surfaces of Pinus roxburghii (chir pine) to a xenon source. Changes in chemical composition were monitored by measuring IR and fluorescence spectra and were correlated with colour changes. A linear correlation between degradation of lignin and total colour change (&#61508;E) was observed.
K K Pandey

Distinguishing isolates of Aureobasidium on the basis of their ability to utilise lignin breakdown products as a sole carbon source
1996 - IRG/WP 96-10151
Wild isolates of Aureobasidium were obtained by dilution plating from a ca 20 year old painted pine window frame. Four isolates were obtained from the paint/wood interface region and four isolated from regions deep in the wood. The isolates were then used to inoculate liquid cultures containing ferulic acid, a lignin breakdown product, present as the sole carbon source. Ability of the isolates to use ferulate, judged by fungal yield, viable propagule count and absorbance at 280 nm (a measure of the aromatic&apos;s final concentration) was dependent on the site of isolation. Isolates from the paint/wood interface were consistently better at utilising ferulate than those isolated from deep in the wood and a possible reason for this is suggested.
M W Schoeman, D J Dickinson

Soft rot decay in acetylated wood. Chemical and anatomical changes in decayed wood
2002 - IRG/WP 02-40231
Acetylated Beech (Fagus sylvatica) and Scots Pine (Pinus sylvestris) wood were studied in soil beds under laboratory conditions for longer periods. High mass losses and dynamic MOE losses were measured in non-acetylated wood and at lower weight percent gains (WPG). Rapid losses of lignin, holocellulose and ?-cellulose occurred in non-acetylated beech wood and no losses were detected at the highest WPG. Changes in chemical composition of acetylated beech wood at lower WPGs was measured. Slight changes in chemical composition of non-acetylated Scots pine wood were also observed and minor changes in acetylated wood at all WPGs; except in holocellulose. An intensive anatomical study was performed by light microscopy and SEM microscopy. The results are presented and discussed. Results showed a significant prevention of acetylation against fungal growth above 8 % and 10 % WPGs in beech and pine respectively.
B Mohebby, H Militz

Effects of alkali treatment on some mechanical and chemical properties of creosote treated oaks
1991 - IRG/WP 2366
To date, there is a lack of information on the effects of chemical treatment on the performance of creosote preservative treated oak sleepers. This factorial experiment was designed to analyze three main effects: species (Quercus alba and Quercus rubra) creosote treatment (treated and untreated), and alkali (NaOH) soaking (0, 1, and 10 percent). The modulus of elasticity (MOE) and fiber stress at proportional limit in compression perpendicular to grain, hardness modulus, surface hardness, alcohol-benzene extractives, hot-water extractives, 1% NaOH extractives, lignin, pentosans, holocellulose, and alpha-cellulose content were determined on specimens. The test results indicated that species, creosote treatment, and alkali soaking significantly affect both the mechanical and chemical properties of the oak sleepers.
P Chow, A J Reinschmidt, E J Barenberg, L C Chang

Degradation of lignin model compounds with coordinated copper in the presence of peroxide
1998 - IRG/WP 98-10282
A novel diffusible system capable of decomposing lignin model compounds with copper, coordinators and peroxides has been proposed. When pyridine was used as a copper coordinator, two synthetic dyes, Poly-R and RBBR were intensively decolorized with Cu(II) and H2O2 in aqueous solutions at room temperature. Although reactions with Cu(II) and H2O2 produce a strong oxidant, hydroxyl radical, via a Fenton pathway, the coordinated copper system presented here was much more effective than the simple Fenton reaction for decolorizing the polymeric dyes. In contrast to the dye decolorization, the Cu(II)/pyridine/H2O2 system was not effective for depolymerizing 14 C-labeled synthetic lignin. However, phenolic and nonphenolic lignins were extensively decomposed by Cu(II) and pyridine in the presence of lipid hydroperoxide model compounds in aqueous solution at room temperature. Since pyridine is produced by ligninolytic fungi and the pyridine nucleus is an essential component of fungal metabolites, we herein propose that the copper/coordination compound/peroxide could be involved in decomposition or modification of lignin during wood rotting.
K Koller, K Messner, T Watanabe

Quantification of wood decay effects by HPLC analysis
1992 - IRG/WP 92-1576
The present work quantified the effects of the white rot basidiomycetes Coriolus versicolor and Phanaerochaete chrysosporium, and also those of the brown rot fungi Coniophora puteana and Lentinus lepideus, on Pinus patula and Eucalyptus grandis. Wood colonisation was quantified by Kjeldahl nitrogen determinations converted to biomass assays, and degradation was quantified by weight losses produced in the wood. Degraded wood samples were then analysed using high performance liquid chromatography (HPLC) of hydrolysates and their sugar contents were determined to establish whether the glucose of cellulose and xylose of hemicellulose had been utilised by the respective fungi. The extent and nature of sugar utilisation by each fungus in wood was then compared with the biomass and degradation data. Statistical analyses of these comparisons correlated the extents of colonisation, degradation, and the patterns of wood sugars predominantly utilised by each fungus. It was verified that the extent of wood conversion increased with biomass production. Importantly, the result of corresponding glucose and xylose analyses confirmed the brown rot physiological capacity a cellulolytic and hemicellulolytic, whereas that of the white rotters was primarily non-cellulolytic. In contrast, these analyses also showed that the white rotter Phanaerochaete chrysosporium demonstrated some cellulolytic and hemicellulolytic activity. The significance of these findings becomes apparent when colonised wood of apparent soundness is analysed as described here to determine whether or not decay was associated with such colonisation.
V Singh, M Tarin, G D Shelver, A A W Baecker

The rôle of lignin in the nutrition of several Australian termites
1983 - IRG/WP 1191
The ability of Nasutitermes exitiosus (Hill), Coptotermes acinaciformis (Frogatt), Coptotermes lacteus (Froggatt) and Mastotermes darwiniensis (Froggatt) to degrade 14C-lignin preparations was examined. The lower termites were unable to degrade lignin. Nasutitermes exitiosus was able to cause a 5-8% degradation of hardwood lignins and a synthetic lignin. It failed to degrade the lignin of Pinus radiata D.Don.
L J Cookson

A technique for the rapid assessment of wood surface degradation during weathering
1987 - IRG/WP 2281
Radiate pine (Pinus radiata D. Don) sapwood samples taken from four trees were converted into thin strips 100 x 10 x 0.085 (85 µm) mm³, (longitudinal x radial x tangential) in size and exposed in preweighed hatches to the weather inclined at 45° facing equatorially for 10, 20, 40, 60, 80 and 100 days. Significant (P < 0.001) weight losses occurred with time over the exposure period. Differences between samples were non significant. Chemical analysis indicated a progressive increase in surface solubility resulting in significant losses of polysaccharides and lignin.
P D Evans, D Abbott, S Thein

Lignin degradation by a non-enzymatic system supposed to be active in white rot fungi
2000 - IRG/WP 00-10340
Electron microscopic investigations have shown that ligninolytic enzymes of white-rot fungi are only able to penetrate the wood cell wall in late stages of degradation. Thus, the selective degradation of lignin of certain white-rot fungi can only be explained on the basis of a low molecular weight, highly diffusible system. A system, consisting of copper, a coordination compound and either H2O2 or organic peroxide was found to be highly ligninolytic and has been proven on different types of lignin model compounds. In this paper, it is shown that this system is also capable of delignifying soft and hardwood lignin. Delignification was indicated on wood sections by differential staining with astra-blue and safranine and was quantified by UV-microscopy in cell walls. It was demonstrated that especially when organic peroxide was used in the copper system, even the recalcitrant softwood lignin was depolymerized while with H2O2 only hardwood lignin was oxidized efficiently. Due to the selectivity of lignin degradation it is assumed that rather peroxyl, alkoxyl or carbon centered radicals than hydroxyl radicals are the active compounds. In principle the copper system is comparable to the diffusible system active in brown-rot, but with the latter one leading to cellulose degradation. A deeper insight into the mechanism of white-rot decay, including also the likelihood of non-enzymatic reactions could alter the generally accepted picture of purely enzymatic reactions and could probably offer a new approach to chemical wood preservation.
P Lamaipis, W Gindl, T Watanabe, K Messner

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