Your search resulted in 26 documents. Displaying 25 entries per page.
A new process for in situ polymerization of vinyl monomers in wood to delay boron leaching
1998 - IRG/WP 98-40110
Efforts were accelerated on effective use of boron compounds in wood preservation owing to their environmentally safe characteristics and relatively low costs in addition to their well-known high bioactivity and fire resistant properties. Although having these unique favorable properties, they are readily leachable from treated wood at humid conditions. Therefore, they had limited market for exterior applications. A supplementary combination treatment with vinyl monomers; styrene (ST) and methylmetacrylate (MMA) was studied in order to extend the service life of boron treated wood. Sapwood specimens of Japanese cedar (Cryptomeria japonica D. Don) first treated with boric acid (BA) at 1.00% aqueous solution concentration. Vinyl monomers were impregnated after air-drying of BA-treated wood at ambient temperatures. Polymerization was performed during compression of monomer impregnated wood to a 50 to 70% dry set of radial dimension under a hot-press heated to the polymerization temperatures of 60 and 90°C required by the selected catalysts VAZO (a, a' - Azobis-isobutyronitrile) and benzoyl peroxide, respectively. Wood acquired a perfect dimensional stability and remarkably high moisture exclusion efficiency with the minimum water holding capacity with the compressed-wood polymer composite (CWPC) process that was approved by submerging of the test specimens in tap water, boiling water exposure to a 10 cycles accelerated severe weathering. As a result, boron leaching rate from CWPC pretreated with BA was considerably slower than that from ordinary WPC. Scanning electron microscope (SEM) observations were found explanatory for controlled-but-continuous boron leaching determined analytically. An effective bulking was found necessary to accompany to polymerization in cell wall with an even distribution of monomer in wood. Grafting to cell wall components can be tried further to achieve an envelop polymerization of boron deposited sites in WPC for better boron immobility.
M K Yalinkilic, W Dwianto, Y Imamura, M Takahashi
The influence of crystalline and amorphous cellulose on extracellular hydrogen peroxide production by brown-rot fungi
1991 - IRG/WP 1482
The production of hydrogen peroxide (H2O2) has been suggested to play a key role in the degradation of wood by wood-rotting fungi. The production of extracellular hydrogen peroxide was studied by a quantitative method which detects the oxidation of the 2,2-azinobis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) by H2O2 and horseradish peroxidase (HRP) in liquid culture medium. The carbon sources used were crystalline and amorphous cellulose. Two brown-rotters, Serpula lacrymans and Poria placenta, were able to produce clearly detectable amounts of extracellular hydrogen peroxide in liquid medium which contained crystalline cellulose as carbon source. No detectable H2O2 was produced in conditions where amorphous medium was used as carbon source. This result suggests that the conformational structure of the substrate may induce H2O2 production by brown-rot fungi.
A-C Ritschkoff, L Viikari
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
Effect of fatty acid removal on treatability of Douglas-fir
1993 - IRG/WP 93-40008
Treatment of Douglas-fir with chromated-copper-arsenate (CCA) poses a major challenge. Several hypotheses based on the anatomical aspects as well as chemical reactivity of the preservative formulations with cell wall constituents and deposits have been proposed. Techniques to prevent pit aspiration or slow fixation reactions have, however, not significantly improved treatment. The presence of high molecular weight fatty acids have been reported to be responsible for higher hydrophobicity in some wood species. These acids can react with Cu+2/Cr+3 ions to form insoluble metallic soaps, thereby immobilizing Cu/Cr and increasing wood hydrophobicity by a mechanism similar to that employed in paper sizing. The effect of fatty acids on treatability was explored by removing these components via several extraction methods. In general, extracted wood had higher gross solution absorptions and chemical retentions, but preservative penetration was largely unaffected. The results suggest that removal or disruption of fatty acids can improve treatability of Douglas-fir heartwood.
S Kumar, J J Morrell
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
Iron in stone wool - one reason for the increased growth and decay capacity of Serpula lacrymans
1992 - IRG/WP 92-1537
The chemical compositions of stone wool and glass wool were analysed. There was more iron in the stone wool than in the glass wool. It was found that iron present in stone wool was easily dissolved by oxalic acid that Serpula lacrymans is able to produce. The stone wool promoted the decay of pine wood by Serpula lacrymans. The glass wool had no effect on the decay capacity of Serpula Iacrymans. The iron derived from the stone wool may be one reason for the increased growth and decay capacity of Serpula lacrymans. Transition metals (Fe2+, Mn2+, etc.) combined with hydrogen peroxide (H2O2) are believed to be necessary for the oxidative breakdown of polysaccharides.
L Paajanen, A-C Ritschkoff
Photo-discoloration and Degradation of Wood and its Stabilisation by Modification with Benzoyl Chloride
2004 - IRG/WP 04-40274
Photo degradation of Pinus roxburghii (chir pine) and Hevea brasiliensis (rubber wood) was studied under artificial accelerated weathering conditions in a Xenon test chamber. The irradiated samples were analyzed for color changes and chemical changes. Analysis of colour changes in wood surfaces by UV-Vis. irradiation was carried out using a colour measuring (CIELAB) system and chemical changes were monitored using FTIR and fluorescence spectroscopy. Irradiation modified physical and chemical characteristics of wood surfaces and resulted in rapid colour changes, reduction in lignin content and increased concentration of chromophoric groups on the wood surfaces. Colour changes were correlated with formation of carbonyl groups and lignin decay rate determined by FTIR measurements. Fluorescence emission spectra measured from un-weathered wood shows excitation wavelength dependence. Photo irradiation leads to a rapid reduction in the emission intensity, broadening of spectra and a significant red shift in the emission maximum. Photo stability of wood surfaces esterified with benzoyl chloride was also assessed. The modification was characterized and analyzed by fluorescence and FTIR spectroscopy and photo-stability of modified wood was assessed. Esterification of wood by benzoyl chloride suppressed the colour changes (photo-discoloration) and also reduced the lignin degradation and generation of carbonyl groups on irradiated wood surfaces. Results show esterification of wood with benzoyl chloride was effective at inhibiting photo-degradation of wood polymers.
K K Pandey
Screening of lignin peroxidase from white-rot fungi
1998 - IRG/WP 98-10274
Since lignin peroxidase was first found in the ligninolytic culture of Phanerochaete chrysosporium, it has been regarded as an enzyme responsible for the lignin biodegradation and studied comprehensively. As the results of these studies its unique characteristics have been revealed. On the other hand, the features of lignin peroxidase produced by other white-rot fungi have not been studied so much. In this study, over 80 white-rot fungi were examined for their ability to produce lignin peroxidase. Five fungi produced lignin peroxidase, and they were subjected to further investigations. These lignin peroxidases showed higher activity at pH 3.5 than pH 4.5 in the oxidation of veratryl alcohol. It could oxidize guaiacol slowly. These features are similar to those from P. chrysosporium. Newly isolated lignin peroxidase were inactivated by the reaction with hydrogen peroxide. There was a difference in the rates of the inactivation by the hydrogen peroxide treatment. The rate observed in the inactvation of lignin peroxidase from P. chrysosporium was moderate.
Controlling the sapstain fungus Ceratocystis coerulescens by metabolites obtained from Bjerkandera adusta and Talaromyces flavus
1993 - IRG/WP 93-10024
Sapstain causes severe damage to wood and wood products, posing a major economic problem for the wood industry. The purpose of this study was to determine if metabolites from Bjerkandera adusta and Talaromyces flavus would (1) decolorize stain in wood caused by Ceratocystis coerulescens and (2) prevent sapstain by Ceratocystis coerulescens. We studied the interaction of the sapstain fungus Ceratocystis coerulescens against the test fungi Bjerkandera adusta and Talaromyces flavus in dual cultures on agar medium. The metabolites obtained from test fungi were examined on pine veener disks stained by Ceratocystis coerulescens. Our results indicate that the test fungi were antagonistic to the sapstain fungus Ceratocystis coerulescens. The combination of metabolites from the antagonists decolorize the sapstained pine veener disks and killed the existing growth of Ceratocystis coerulescens.
S C Croan, T L Highley
Fungicidal activity of some new water borne copper octanoate based formulations
1999 - IRG/WP 99-30198
Four new water borne formulations for preservation of wood were prepared: the composition of Cu(II) octanoate, 2-aminoethanol (ethanolamine) and water; the composition of complex of Cu(II) octanoate with nicotinamide, 2-aminoethanol and water; the one of Cu(II) octanoate, organic boron complex, 2-aminoethanol, dimethyl sulfoxide and water and finally, the mixture of Cu(II) octanoate, diazene, 2-aminoethanol and water. Fungicidal activity of these new formulations against Trametes versicolor, Antrodia vaillantii and Coniophora puteana was determined by filter paper and mini-block test methods. Compared to the commercially used wood preservative containing Cu(II) naphthenate / Cu(II) 2-ethylhexanoate, the new compositions have stronger fungicidal activity. The strongest biocidal activity was exhibited by the formulation with a Cu(II) octanoate/nicotinamide complex.
M Petric, M Pavlic, F Pohleven, P Segedin, B Kozlevcar, S Polanc, B Stefane, R Lenarsic
Production of exraxellular hydrogen peroxide and oxalic acid by brown-rot fungus Poria placenta
1995 - IRG/WP 95-10112
Hydrogen peroxide and oxalic acid have been suggested to be essential in the degradation of wood carbohydrates by brown-rot fungi. Hydrogen peroxide has been suggested to be one of the diffusible low molecular weight agents produced by brown-rot fungi for the degradation of wood carbohydrates by generating highly active radicals. The production of hydrogen peroxide and oxalic acid by Poria placenta was studied on crystalline cellulose, amorphous cellulose and glucose media. Hydrogen peroxide and oxalic acid were clearly produced on culture media containing either amorphous or crystalline cellulose. Hydrogen peroxide and oxalic acid were formed simultaneously and highest amounts of these compounds were obtained on amorphous cellulose. The production of hydrogen peroxide and oxalic acid was surprisingly low on glucose medium.
A-C Ritschkoff, M Rättö, J Buchert, L Viikari
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
Extracellular hydrogen peroxide producing and hydrogen peroxide reducing compounds of wood decay fungi
1991 - IRG/WP 1516
Extracellular H2O2-producing and H2O2-reducing compounds were isolated from wood-containing cultures of all the white-rot and brown-rot fungi and Ascomycetes which well degraded wood, but were not detected in the culture of the fungi which degraded little wood. The compounds are glycopeptides with a low molecular weight, require H2O2 for one-electron oxidation, catalyze the redox reaction between an electron donor such as NADH or ascorbic acid and O2 to produce H2O2 via O2·-, and produce ·OH by Fenton's reaction between the ferrous iron bound to the ligands and H2O2. The compounds show no phenol-oxidase activity and catalyze the hydroxylation of phenol to catechol and hydroquinone in the presence of H2O2.
A Enoki, G Fuse, H Tanaka
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
Extracellular substance from the white rot basidiomycete Irpex lacteus involved in wood degradation
1992 - IRG/WP 92-1571
Cellulases, phenol oxidase, and a substance that both produced and reduced H2O2 were isolated from cultures containing wood or glucose on which the white-rot fungus Irpex lacteus was growing. The rate of wood degradation by the fungus with different amounts of glucose in the medium was measured. More of the substance that produced and reduced H2O2 was found extracellularly in cultures containing wood than in cultures containing glucose. The extent of one-electron oxidation activity of the extracellular substance was correlated with that of the wood-degrading activity, but the extent of phenol oxidase activity was not. The extracellular substance catalyzed the hydroxylation of phenol to hydroquinone and catechol in the presence of H2O2 or of NADH and O2. The substance seemed to be a glycopeptide containing Fe(II) and its molecular weight was very low.
H Tanaka, T Hirano, G Fuse, A Enoki
The role of oxidation in wood degradation by brown-rot fung
1992 - IRG/WP 92-1562
Brown-rot fungi are suggested to degrade cellulose by oxidation with hydrogen radicalsformed eg. in the conversion of hydrogen peroxide in the Fenton type reactions. The stuctural changes in the holocellulose in wood induced by Fenton's reaction on wood components are very similar to those caused by brown-rot fungi. In this work the effect of the Fenton reaction on wood components was studied. The brown-rot fungi produce extracellular hydrogen peroxide while growing on sawdust medium and on crystalline cellulose. Hydrogen peroxide is apparently formed by the action of an oxidase enzyme. In this work the role of enzymatic oxidation in cellulose degradation by the brown-rot fungus, Poria placenta was studied.
A-C Ritschkoff, J Pere, J Buchert, L Viikari
Mechanistic aspects of the reactions of copper complexes with lignin in the presence of hydrogen peroxide and lipid hydroperoxide model compounds as proposed for white rot fungi
2001 - IRG/WP 01-10399
The structural principles and the oxidative reactions of the catalytic system consisting of copper, hydroperoxides, and copper coordination compounds that contain aromatic nitrogen atoms are similar to those of catalytic centers of oxidative enzymes involved in delignification reactions of white rot fungi. The system is capable of selectively degrading lignin and its low molecular weight would allow to react oxidatively also at sites of the wood cell wall, where enzymes cannot penetrate. Understanding the mechanisms of white rot would offer perspectives to develop targeted wood preservatives to inhibit these enzymatic and non-enzymatic reactions of wood decay. Studies on the mechanism of the copper/pyridine and 4-aminopyridine resp./hydrogen peroxide system that were carried out with 14C-labeled lignin and cellulose model compounds demonstrated the selectivity of the copper system for lignin structures and the ability of the system to oxidise even non-phenolic lignin. Product profiles of the reactions supported by ESR measurements suggested a non-radical reaction pathway involved in that case. However, when a lipid hydroperoxide model (cumene hydroperoxide, CHP) was used as peroxide source, a variety of free radicals derived from this peroxide could be detected in ESR. Selective staining of treated wood sections with safranin and astra blue showed degradation of softwood and hardwood lignin in the middle lamella and secondary cell wall. Besides its importance for developing targeted wood preservatives, the coordinated copper system has great potential for application for selective lignin degradation in the pulp and paper industry and could therefore replace environmentally problematic chlorine and chlorine dioxide based pulp bleaching stages.
K Fackler, P Lamaipis, E Srebotnik, M Humar, C Tavzes, F Pohleven, M Sentjurc, T Watanabe, K Messner
Extracellular hydrogen peroxide-producing and one-electron oxidation system of brown-rot fungi
1990 - IRG/WP 1445
Wood-component-degrading compounds involved in the initial degradation of the cellulose and lignin in wood were isolated from wood-containing culture of brown-rot fungi, Gloeophyllum trabeum and Tyromyces palustris and partially purified by gel filtration on Sephadex G-25 and DEAE-Sepharose ion-exchange chromatography. The compounds were glycoproteins. The molecular weights of the glycoproteins as determined by gel filtration were very small and about 1,600-2,000. The one-electron oxidation activity of the peptides was determined by measuring ethylene production from 2-keto-4-thiomethylbutyric acid (KTBA). The peptides contained ferrous iron,required H2O2 for KTBA oxidation, were capable of catalyzing the oxidation of NADH to produce H2O2 in the presence of 02 and showed little phenol-oxidase activity under conditions giving high activity against KTBA. The ferrous iron combined with the glycopeptides was oxidized to the ferric state by H2O2.
A Enoki, S Yoshioka, H Tanaka, G Fuse
Experiments on the degradation of tributyltin oxide: A progress report
1984 - IRG/WP 3287
A variety of experiments designed to assess the chemical and physical factors affecting the degradation of tributyltin oxide in treated timber are described. Simple procedures in which temperature and oxygen availability were increased in the presence of wood and water suggest that the wood itself was of prime importance. Attempts to decrease degradation with antioxidants were unsuccessful but led to the idea that free radicals may be instrumental in the degradative mechanism. Subsequent work in which a range of antioxidants and free radical producing systems were used confirmed the susceptibility of tributyltin oxide to the action of free radicals. It is suggested that the presence of free radicals in the painted and treated wood system may be an important factor in the eventual degradation of tributyltin oxide.
R J Orsler, G E Holland
In-house accelerated method for testing decay resistance of treated wood
2004 - IRG/WP 04-20286
Fungicidal compounds often change their effectiveness when they are incorporated into candidate formulations. For this reason fungistatic effectiveness needs to be re-evaluated as many times as the formula has been modified for better performance. To avoid multiple expenses, in-house fungistatic tests are essential. Our goal was to develop in-house usable, simple but reliable and reproductive procedure for testing decay resistance of the Sansin priming formulae without a need for special testing equipment. Our preliminary trials have proved that commercially available, heat processed wood pellet fuel can be used as an excellent substrate for growing certain wood rotting fungi. In contact with water wood pellets quickly disintegrate and convert into sawdust, gaining up to three times increase in volume. When wood pellets are wetted with water containing hydrogen peroxide, the vapors of this antiseptic kill non-desirable air-borne contaminants and protect the substrate from further contamination for as long period as peroxide remains in the substrate at sufficient concentration. When peroxide protected substrate is spawned with well-organized fungal organisms (for example true decay/test fungi), they will rapidly colonize the substrate and develop a powerful mycelial network capable of decomposing most of the natural fiber based materials. Treated and non-treated wood specimens were buried in spawned, hydrogen peroxide protected wood pellet fuel-based substrate and placed in transparent, perforated plastic containers to determine the effect of this procedure on rapid colonization and accelerated wood degradation. Parallel test was set up with specimens inserted in 150mm diameter dishes containing fungal cultures developed on the beer based agar medium. The results after 45 and 90 days of exposure to the brown rot causing fungus Gloeophyllum trabeum indicate that the weight loss in control blocks in containers was higher than in the dishes for 7 and 11 percent respectively.
Redox regulation of enzyme activity during wood decay
1996 - IRG/WP 96-10172
A potential strategy in the search for alternative wood preservatives against fungal decay is to target the extracellular wood-decay process itself, rather than the decay organisms. This presents novel targets for selective disruption and possibly without the broad-spectrum toxicity associated with conventional wood preservatives. The enzymes of white rot decay are mechanistically diverse (e.g. hydrolytic, oxidative, peroxidative) and therefore various strategies for the disruption of their activity can be conceptualized. We have characterized how effectors control activity of the extracellular enzyme glyoxal oxidase. This enzyme is secreted by Phanerochaete chrysosporium and produces hydrogen peroxide required by ligninolytic peroxidases. Our studies with recombinant glyoxal oxidase show that the native enzyme is activated by inorganic oxidants or by lignin peroxidase when peroxidase substrates of high redox potential are used. The interconversion between active and inactive forms of the enzyme is defined in redox terms based on spectroelectrochemical measurements of the active site of glyoxal oxidase.
P J Kersten, B Kurek, J W Whittaker
The production of extracellular hydrogen peroxide by some brown-rot fungi
1990 - IRG/WP 1446
The role of hydrogen peroxide (H2O2) has been discussed in the degradation of wood by wood-rotting fungi. The production of extracellular hydrogen peroxide was studied by detecting the oxidation of the chromogen 2,2'-azinobis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) by H2O2 and horse radish peroxidase (HPR). ABTS and HPR were added to a solid wood based culture media. In this study two brown-rotters, Poria placenta and Serpula lacrymans, produced detectable extracellular hydrogen peroxide.
A-C Ritschkoff, L Paajanen, L Viikari
Micromorphology of oak wood degraded by brown rot fungus Coniophora puteana
2000 - IRG/WP 00-10356
To characterize the degradation of hardwood by brown rot fungus, Coniophora puteana was incubated on the wood blocks of Quercus accutissima. For comparison, the same fungus was also incubated on the pine wood blocks of Pinus densiflora. In softwood, the shape of the wood cells and thickness of the cell appeared unchanged even the loss of birefringence in the affected areas. In contrast, oak wood decayed by brown rot fungus showed the erosion of wood cell walls from lumen towards the middle lamella. Complete degradation of cell walls including the lignin- rich middle lamella occurred in some areas of the oak wood cells. Degradation modes of brown rot fungus C. puteana in oak wood followed a typical white rot. The production of hydrogen peroxide was confirmed cytochemically by the deposition of cerium chloride in the degraded wood cell walls. However, Bavendamm test was negative to C. puteana. The present work suggested that hydrogen peroxide produced by brown rot fungus might be associated with not only the depolymerization of cellulose in softwood but also the degradation of lignin in hardwood.
Yoon Soo Kim, Seung-Gon Wi, Kwang-Ho Lee
Effects of bleaching process on the roughness values of wood surfaces of Lebanon cedar (Cedrus libani A. Rich.) and Black poplar (Populus nigra L.) using NaOH (sodium hydroxide), H2O2 (hydrogen peroxide) and Ca(OH)2 (calcium hydroxide)
2008 - IRG/WP 08-40403
Technical progress in the wood industry has been rapid in recent times. In this case, the quality assurance of the consumer products aligned with aesthetics value appears as one of the most important parameters. Because of the outer appearance of goods exert an effect on customers, interest in production of high quality surfaces of wooden commodities has increased essentially based on the surface smoothness (and/or the surface roughness of wood) aiming to reach the customer-oriented quality criteria. An aesthetics behaviour is being more influenced than the functional situation of the merchandise when the customers making the decision to buy wood products. It has been well estabilished that some of the properties of wood material (i.e. density, porosity, moisture content, fiber directions), and the wood machining process and its conditions (i.e. kinematics of the cutting process, wood sanding process) make the surface smoothness of wood problematic. There is a lack of information about the effects of bleaching process (i.e. one of the special technical ways to increase the aesthetics of wood products) on the smoothness of wood surfaces despite numerous reports published on the machining tools and the cellular structure of wood. In this study, therefore, effects of bleaching process on the surface roughness of wood was investigated for Lebanon cedar (Cedrus libani A. Rich.) and Black poplar (Populus nigra L.) using the bleaching chemicals NaOH (sodium hydroxide), H2O2 (hydrogen peroxide) and Ca(OH)2 (calcium hydroxide) by the two prescriptions with or without calcium hydroxide.
I Usta, E Aydinlar
Degradation of wood veneers by Fenton’s reagents: effects of low molecular weight phenolic compounds on hydrogen peroxide decay and tensile strength loss
2009 - IRG/WP 09-20400
Pine wood (Pinus sylvestris) veneers strips were incubated in acetate buffer containing hydrogen peroxide and iron to mimic mechanisms of brown rot decay and assess the degradation of cellulose through analysis of the tensile properties of the decayed wood. The tensile properties of thin wood strips treated with Fenton system reagents or precursors were determined and correlated to weight loss as reaction conditions were varied. The effect of 2,3‑DHBA concentration on the decay rate of H2O2 in the reaction mixture and the mechanisms of H2O2 decomposition will be discussed. The concentration and ratio of the low molecular weight, phenolic compound 2,3-dihydroxybenzoic acid (2,3‑DHBA) were also studied with regard to the generation of hydroxyl radicals from H2O2 and the resulting weight and strength loss. The pathway and rate of H2O2 decay depended on the pH and the medium (water, buffer) of the reaction mixture. As the concentrations of 2,3-DHBA above an optimal ration with iron, strength loss of the wood strips was reduced. This is likely to have occurred because concentrations of catechols that exceed a 1:1 ratio sequester iron via hexadentate and quadradentate ligand formation as has been previously reported Wood constituents were also shown to reduce Fe(III) to Fe(II) and to drive the Fenton reaction.
Yanjun Xie, R Well, Zefang Xiao, B Goodell, J Jellison, H Militz, C Mai