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Characterization of wood decay enzymes by MALDI-MS for post-translational modification and gene identification
2002 - IRG/WP 02-10442
The recent sequencing of the Phanerochaete chrysosporium genome presents many opportunities, including the possibility of rapidly correlating specific wood decay proteins of the fungus with the corresponding gene sequences. Here we compare mass fragments of trypsin digests, determined by MALDI-MS (Matrix Assisted Laser Desorption Ionization-Mass Spectrometry), with predicted mass fragments derived from genome sequence. Glyoxal oxidase of P. chrysosporium is used for proof of concept because its genomic organization is known. Glyoxal oxidase was also chosen because it is a glycoprotein, as are many other fungal proteins, and post-translational sites are predicted by MALDI-MS.
T H de Koker, P J Kersten

Effect of protective additives on leachability and efficacy of borate treated wood
2002 - IRG/WP 02-30290
Borate preservatives have been used extensively in many countries as an effective means for protecting wood against fungal and insect attack especially in interior environments. Under exterior conditions, borate compounds have a main disadvantage as they can be leached from treated wood as a result of their water solubility. In this study, we compared the potential of different additives for reducing the leachability of boron preservatives from treated wood. Scots pine sapwood (Pinus sylvestris) and poplar (Populus trichocarpa x deltoides) test samples were vacuum treated with 1 % BAE (Boric Acid Equivalent) disodium octaborate tetrahydrate (DOT) solutions containing various additives e.g. glycerol/glyoxal, polyvinylpyrrolidone (PVPY), a commercial resin compound and a commercial water repellent. The European Standard EN 84 was used as a leaching test for both coated and uncoated specimens. The results of chemical analysis of leachates taken at different periods showed that the use of protective additives reduces the boron leachability. The glycerol/glyoxal additive applied to treated pine sapwood showed the best performance. The percent of boron retained in uncoated pine sapwood was 26% while coated samples still retained 45% after 14 days of intense leaching. Similar tests on poplar revealed 19% and 34% for uncoated and coated samples, respectively.This represents a gain of 20 to 25% compared to pure DOT treated specimens of both wood species. Preliminary biological tests were carried out on malt agar using a miniblock technique for uncoated pine sapwood and beech, with Poria placenta and Coriolus versicolor, respectively. After six weeks of exposure to fungal attack all boron protective systems tested proved their effectiveness, as none of the test samples exhibited a mass loss exceeding 4%. The reference 1% BAE without protective additives showed an average mass loss of 15%. Finally, test data are reported of standard EN 113 testing in view of a further evaluation of the biological efficacy of combined DOT-additive treatments.
A Mohareb, J Van Acker, M Stevens

Physiologic response of Phanerochaete chrysosporium to exposure to triazole fungicides
1994 - IRG/WP 94-10066
Triazoles are increasingly important fungicides which are employed for a variety of applications included wood protection. Several recent studies suggest that white rot fungi are more tolerant of triazole compounds than other wood degrading fungi. Cultural studies using a white rot fungus, Phanerochaete chrysosporium, and 0.2 or 0.8 ppm of tebuconazole or propiconazole suggested that mycelial dry weight was most affected by the presence of triazoles. Extracellular carboxymethylcellulase, cellobiosidase and phenol oxidase activities were depressed but not inhibited by triazoles, while ß-glucosidase activity appeared to be slimulated by the presence of these biocides. The results suggest that white rot fungi may be less sensitive to triazoles and this diminished sensitivity may permit these fungi to become more important on wood treated with this biocide.
J J Morrell, R K Velicheti

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

Analysis of D-glucose metabolism of wood decay fungi using 13C-NMR and 13C-labeled substrates
2003 - IRG/WP 03-10475
D-Glucose metabolism is thought to be important during wood decay by fungi, not only for anabolic and catabolic purposes of central metabolism, but also as a potential source of peroxide required by extracellular peroxidases. There has been some confusion in the literature as to whether this peroxide-generating activity is of the glucose 1-oxidase or pyranose 2-oxidase (glucose 2-oxidase) type with various fungi or even within the same fungal species. Definitive classification requires accurate identification of the enzymatic products D-glucono-1,5-lactone and D-arabino-2-hexosulose (glucosone) with glucose 1-oxidase and pyranose 2-oxidase, respectively. We used 13C-NMR to distinguish these reactions starting with 13C-labeled glucose. The use of labeled substrates simplifies analysis and greatly increases detection sensitivity without requiring the isolation or derivatization of metabolites. We synthesized 13C-1-glucosone to study subsequent metabolism with crude enzyme preparations. Preliminary results with Phanerochaete chrysosporium are presented.
T H de Koker, M D Mozuch, P J Kersten

Wood and filter paper degradation, phenol oxidase and one-electron oxidation activities by the white rot fungus Ceriporiopsis subvermispora
2003 - IRG/WP 03-10486
The activities of one-electron oxidation and phenol oxidase during incubation of cultures of the white-rot basidiomycete Ceriporiopsis subvermispora containing either glucose or wood were periodically measured. Further, the degradation activities against wood and filter paper were examined during the course of cultivation. Weight losses of Japanese beech wood and Japanese cedar wood after 12 weeks were about 20% and 15%, respectively. Weight loss of filter paper was about 23% after 9 weeks. The one-electron oxidation and phenol oxidase activities in wood-containing cultures were higher than those in glucose-containing cultures. Extracellular low-molecular-weight substance has been isolated and has been characterized to compare with the substances from other wood degrading fungi that catalyze a redox reaction between O2 and electron donors to produce hydroxyl radicals. The mechanism on wood degradation caused by the white-rot fungus C. subvermispora is discussed.
H Tanaka, S Itakura, A Enoki

Effect of aqueous polymer treatments on wood properties. Part 2: Mechanical properties
1990 - IRG/WP 3611
Partially air-dried sapwood of sweetgum (Liquidambar styraciflua) and southern pine (Pinus spp.) was treated with either aqueous polyacrylate or aqueous dimethyloldihydroxyethyleneurea (DMDHEU) solutions. Tests for static bending, toughness, and hardness were conducted on matched treated and untreated pieces according to ASTM Standards. Properties of pine were not affected by treatment with the polyacrylate. With sweetgum, the modulus of rupture and modulus of elasticity were reduced, while hardness was improved. For the DMDHEU treatment, reduction in property values for both species was related to curing temperature.
Z Ashaari, H M Barnes, D E Lyon, R C Vasishth, D D Nicholas

Effect of aqueous polymer treatments on wood properties. Part 1: Treatability and dimensional stability
1990 - IRG/WP 3610
Partially air-dried sapwood of sweetgum (Liquidambar styraciflua) and southern pine (Pinus spp.) was treated with either aqueous polyacrylate or aqueous dimethyloldihydroxyethyleneurea (DMDHEU) solutions. Tests for dimensional stability were conducted on matched treated and untreated pieces. Measurement of the antishrink efficiency indicated that DMDHEU was a better stabilizer than the polyacrylate system. Stability was related to polymer retention and curing temperature.
Z Ashaari, H M Barnes, R C Vasishth, D D Nicholas, D E Lyon

Phenol oxidase activity and one-electron oxidation activity in wood degradation by soft-rot deuteromycetes
2007 - IRG/WP 07-10615
Wood degradation, one-electron oxidation activity as assayed by ethylene generation from 2-keto-4-thiomethylbutyric acid (KTBA), and phenol oxidase activity were measured in cultures of six deuteromyce fungi, with glucose or wood as the carbon source. The four fungi that degraded Japanese beech wood had higher one-electron oxidation activities in wood-containing cultures than in glucose-containing cultures. These four fungi also had measurable phenol oxidase activity in wood-containing cultures, but not in glucose-containing cultures. The two mould fungi that did not significantly degrade wood had no phenol oxidase activity in either wood- or glucose-containing cultures. The one-electron oxidation activity in intact cultures of the soft-rot deuteromycetes was roughly related with the rate of mass loss during wood degradation in those cultures. However, there was no clear relationship between phenol oxidase activity and either one-electron oxidation activity or the rate of wood mass loss, either over time, or in total. Most of the one-electron oxidation activity resulted from phenol oxidase and hydroxyl radical. Most of the phenol oxidase activity resulted from laccase. Furthermore, the mechanism of wood degradation by one of these deuteromycete fungi, Graphium sp., was investigated. Most of the phenol oxidase activity appeared to derive from laccase. Most of the ethylene generation from KTBA was attributed to hydroxyl radicals, produced by a low-molecular-mass substance in the extracellular media. This substance was composed of protein, carbohydrates, and Fe(II), and catalyzed redox reactions between O2 and unidentified electron donors, to produce hydroxyl radicals via H2O2. It is suggested that hydroxyl radicals may produce new phenolic substructures on the lignin polymer, making it susceptible to attack by laccase. Thus, one-electron oxidation acitivity and laccase activity are both important in wood degradation by Graphium sp.
H Tanaka, M Yamakawa, S Itakura, A Enoki

Oxidative stress and lignin peroxidase production in Phanerochaete chrysosporium
2008 - IRG/WP 08-10655
In Phanerochaete chrysosporium liquid cultures, the induction of lignin peroxidases is directly related to accumulation of reactive oxygen species at the mitochondrial level. In this study, we demonstrate that the expression of the mitochondrial thiol-related antioxidant system is not directly coupled to the LiPs expression. When the antioxidant systems are not able to cope with ROS accumulation, a major change in the respiratory pathway leading to a large modification of the oxidative phosphorylation occurs. The adaptative system revealed by this study plays probably a central role in the LiPs expression regulation and could allow identifying new targets for wood preservatives.
M Morel, L Diss, C Fourrey, M Chalot, M Droux, J P Jacquot, E Gelhaye

Effect of wood polymers degradation during heat treatment on extracellular enzymatic activities involved in beech degradation by Trametes versicolor
2008 - IRG/WP 08-40392
Effect of heat treatment on extracellular enzymes involved in wood degradation by Trametes versicolor was investigated. Heat-treated and untreated beech blocks were exposed to T. versicolor on malt agar medium and extracellular enzymatic activities investigated. A strong ABTS oxidizing activity has been detected during the first stage of colonization in both cases, while cellulase activities are mainly detected in the case of untreated beech wood. Further investigations carried out on holocellulose, isolated using sodium chlorite delignification procedure, either on untreated beech wood or heat treated one, indicate that commercially available cellulases are able to hydrolyse totally holocellulose from untreated sawdust, while hollocellulose from heat treated one was only partially hydrolysed. CP/MAS 13C NMR analysis of heat treated beech wood but also its lignin and holocellulose fractions obtained after acidic hydrolysis of polysaccharides or delignification with sodium chlorite indicates an important modification of hollocellulose showing degradation of hemicelluloses as generally described in the literature, but also formation of carbonaceous materials within the wood structure. All these data suggest that chemical modifications of wood components during heat treatment disturb enzymatic system involved in wood degradation.
S Lekounougou, G Nguila Inari, M Pétrissans, S Dumarçay, J P Jacquot, E Gelhaye, P Gérardin