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Screening of fungal strains for wood extractive degradation
1998 - IRG/WP 98-10254
Fungal strains were screened for their ability to degrade apolar extractives in wood from scots pine. The degradation of total wood extractives by 91 different strains was monitored in stationary batch assays incubated for 6 weeks. The results obtained show that the ability of wood-inhabiting fungi to utilize wood extractives varied greatly, even for different isolates of the same species. Fungal pretreatment provided up to 70% total resin reduction. Outstanding strains included mainly white-rot fungi. Several sapstain strains were also efficient extractive degraders. Apolar extractives are well known for their inhibitory effect to fungal growth. However, our findings show that wood extractives can serve as carbon source for numerous wood-inhabiting fungi. Furthermore, these results indicate the potentials of wood-inhabiting fungi in biotechnological processes for pulp and paper manufacturing, ie., wood chip depitching and biodetoxification.
J Dorado, M J Martinez-Inigo, T A van Beek, F W Claassen, J B P A Wijnberg, R Sierra-Alvarez

Wood extractive concentration and sem examination of pretreated southern yellow pine wood chips with blue-stain fungi for mushroom production
2001 - IRG/WP 01-10407
Mushroom-producing white-rotting basidiomycetes either do not colonize or else colonize very poorly on freshly prepared southern yellow pine wood chips. This study evaluates the resinous extractive content of southern yellow pine before and after treatment with colorless mutant blue-stain fungi. The blue-stain fungi penetrate into the sapwood of southern yellow pine and utilize nonstructural resinous extractives, simultaneously reducing the total resinous extractive content. Scanning electron microscopic examination showed that heavy mycelial growth with good sporulation occurred on the surface of wood chips within 2 days and in parenchyma cells within 6 days. Ophiostoma spp. removed 61.1% to 99.9% of the extractives from the southern yellow pine wood within a period of 4 to 5 days. We conclude that white-rot basidiomycetes can easily colonize and produce fruiting bodies on treated southern yellow pine wood wastes.
S C Croan, J Haight

Airborne algae as a wood degradation factor
1992 - IRG/WP 92-1549
The occurrence of airborne (aerophytic) algae on wood is a very frequent phenomenon. However, there is currently a lack of information concerning their effect on the wood tissue. Some important genus of algae infesting wood under natural conditions are listed, as well as the results of experimental studies in the "in vitro" culture concerning the effect of two selected algal species on some physico-mechanical properties and on the structure of beech and Scots pine woods.
K J Krajewski, J Wazny

Antifungal properties of new quaternary ammonium and imidazolium salts against wood decay, staining and mould fungi
2004 - IRG/WP 04-30347
The biological activity of twenty-four potential wood preservatives – imidazolium and quaternary ammonium salts with a modified anion structure was determined employing screening agar-plate and agar-block methods. Experiments were carried out on Scots pine (Pinus sylvestris L.) wood. The aim of the performed studies was to investigate the effect of structure modification of IC and QAC with organic anions or copper (ll) and zinc complexes on their biological activity against wood decay, staining and mould fungi. The fungicidal value of new compounds for Coniophora puteana ranged from 0.64 kg/m3 to 2.2 kg/m3. Aspergillus niger turned out to be the most resistant fungus to the action of modified IC and QACs, whereas Sclerophoma pityophila was effectively inhibited by the examined salts. The performed soil-block tests showed that the IC and QAC were leached from the experimental wood in conditions of contact with moist soil and revealed their fungal detoxification by mould fungi, especially by Gliocladium roseum. Observations made using the scanning electron microscope of the colonization and decay of treated wood by mould fungi confirmed tolerance of mould fungi to QACs.
J Zabielska-Matejuk, W Wieczorek

The preliminary characterization of ß-1,4-xylanase of the brown-rot fungus Gloeophyllum trabeum
1990 - IRG/WP 1447
The extracellular ß-1,4-xylanase of the brown-rot fungus, Gloeophyllum trabeum, was isolated from crude extract by chromatofocusing method (PBE 94 column chromatography). The isoelectric point was estimated to 4.2-4.8 by cromatofocusing and 4.5 by isoelectric focusing (IEF). The molecular weight of the enzyme was estimated to 37,000 dalton by SDS-PAGE. The optimal temperature for the crude extract xylanase was +70°C. The enzyme stability, after 1 h incubation, decreased sharply above +60°C and pH 6.
A-C Ritschkoff, M Rättö, L Viikari

Biodegradation of creosote/naphthalene-treated wood in the marine environment
1977 - IRG/WP 428
The present study was undertaken to determine the biodegradability of marine grade creosote and selected components, including naphtalene, and to determine the effectiveness of (up to 40%) creosote in protecting wood from microbial attack. Also, the impact(s) of creosote and naphtalene-enriched creosote on the microbial ecology os estuarine environments was examined.
P A Seesman, R R Colwell, A Zachary, A J Emery

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

Biodegradation of acetylated southern pine and aspen composition boards
1994 - IRG/WP 94-40020
This objective of this study was to investigate the influence of the acetylation treated wood fiber, Phenol-formaldehyde resin content level, two wood fiber species, three fungi species on the dimensional stability and decay resistence of high density composition boards. A standard ASTM method was used to evaluate weight loss and thickness change. The linear shrinkage and expansion of each species were also determined. All specimens were exposed to decay chambers for 16 weeks. Test results indicated that most of the main factors significantly influence the thickness and length changes and the decay resistance of the high density composition boards.
P Chow, T Harp, R Meimban, J A Youngquist, R M Powell

Acetylation of lignocellulosic materials
1989 - IRG/WP 3516
A simplified procedure for the acetylation of lignocellulosic materials has been developed. The acetylation is done with a limited amount of liquid acetic anhydride without the addition of a catalyst or an organic co-solvent. Dimensional stability and biological resistance are both much improved by the acetylation. Equilibrium moisture content in acetylated material is considerably lower than in unmodified material. No reduction of bending strength was found for acetylated solid wood samples. The process can be employed for both fibers, wood particles and solid wood. The process is applicable to hardwoods and softwoods, including solid spruce wood, and to non-wood fibers such as jute.
P Larsson, A-M Tillman

The fungal degradation of quaternary ammonium compounds in wood
1998 - IRG/WP 98-10263
This work focuses on the biodegradation of didecyldimethylammonium chloride (DDAC) by the mould fungus Gliocladium roseum within a woody matrix. Three sawdust types, distinguished by their treatment and amount of DDAC retained, were inoculated with the fungus and their DDAC loss was measured over 11 weeks. The rates of degradation varied depending on the sawdust; however, a significant loss of DDAC was observed for all three. A metabolic by-product coincided with the fungal degradation of DDAC. The metabolite was separated using preparative HPLC and identified by proton-NMR and infrared spectroscopy to be a hydroxylated QAC.
J W Dubois, J N R Ruddick

Effect of extractive fractions of Thuja plicata and Chamaecyparis nootkatensis heartwood on Coptotermes formosanus
2004 - IRG/WP 04-10535
Heartwood of some species has natural resistance to attack by termites due to the presence of toxic and/or repellent extractives, but the role of individual extractives in termite inhibition is poorly understood. Developing a better understanding of which extractives are most effective against termites may be useful for the identification of improved termite management strategies. The effect of selective extractive removal on termite resistance was assessed using matched samples of Thuja plicata (D.Don) and Chamaecyparis nootkatensis (D.Don) Spach heartwood. Samples were extracted using a variety of solvents and then exposed to Coptotermes formosanus Shiraki in a no-choice feeding test. The results suggest that the methanol-soluble extractives in Thuja plicata and Chamaecyparis nootkatensis play important roles in making the heartwood resistant to attack by Coptotermes formosanus. Volatile and hexane-soluble extractives were less important. Further analysis of specific extractive compounds are underway.
A Taylor, B L Gartner, J J Morrell, K Tsunoda

Biochemical relationships between biodegradation of cellulose and formation of oxalic acid in brown-rot wood decay
1991 - IRG/WP 1472
Non-enzymic hydrolysis of cellulose with low concentrations of oxalic acid was examined. The incubation of pine wood pulp with 1% oxalic acid (pH 1.3) at 35°C for 4 weeks reduced the original viscosity to 60%. Reducing sugars were liberated from various cellulosic samples by the oxalic acid treatment. However, crystallinities of cellulose in those samples did not change before and after the treatments. Then, the enzymatic formation of oxalic acid was investigated in relation to cellulose biodegradation by brown-rot fungi. We succeeded in isolating oxaloacetase from the brown-rot fungus Tyromyces palustris in cell-free extracts which catalyze hydrolysis of oxaloacetate to produce oxalate and acetate. During the brown-rot wood decay process, oxaloacetase may play an important role in degradation of wood carbohydrate.
M Shimada, Y Akamatsu, A Ohta, M Takahashi

Biodegradation of wood in wet environments: A review
1997 - IRG/WP 97-10217
Wood in wet environments is attacked and degraded by soft rot fungi and erosion and tunnelling bacteria, which are more tolerant to high moisture and reduced oxygen conditions than basidiomycetes, such as white and brown rot fungi. Since basidiomycetes are normally more aggressive and can degrade wood faster than soft rot fungi and bacteria wood in wet environments can survive longer. In fact, archaeological investigations have shown that wood buried deep in ocean sediments have survived relatively intact for hundreds and even thousands of years. In this review degradation patterns of various types of microbial wood decay have been briefly described, and then examples of decay type(s) present in wood exposed in various wet environments are presented. Concluding remarks emphasise the importance of understanding the relationship between the conditions of wet environments and the biological wood decay present for prolonging the life of wood in service and properly restoring wooden artefacts of historical value.
A P Singh, Yoon Soo Kim

Isolation of soil borne bacteria and fungi from treated timber
2001 - IRG/WP 01-50174
Most research in the last few decades has focused on the development of new strategies to control biological attack and the means to quantify this. Comparatively little work has been done to examine the effect that treated timber might have on its surrounding environment. This presentation will describe a methodology that attempts to detect any changes which might occur in the soil microflora following the introduction of timber treated with a number of chemical agents containing organic active ingredients (a.i.). It was also the purpose to isolate organisms that can break down organic a.i.. A technique was developed to determine whether the presence and nature of a timber preservative influenced the size and composition of a microbial population that colonised timber when buried in soil. Samples of treated timber were incubated in a solution eluted from soil that contained a diverse, viable microbial population. After incubation, the size and composition of the microflora both in the eluate and adhering to the timber was examined.
I Stephan, A Stegemann, G Heidrich

Natural durability, density and extractive contents of 42 wood species of Bangladesh.
2003 - IRG/WP 03-10490
Natural durability, density and major extractive contents of 42 lesser used or unused wood species of Bangladesh have been studied. Correlation analysis between these properties has been performed. It has been shown that natural durability of these species neither explained by water soluble nor by alcohol benzene extractive contents. Density has a weak but significant positive correlation with durability which indicates that density might have some influence on durability of these wood species.
S Akhter, K Akhter, S C Das

Enhanced biodegradation of cocopeat by soft rot fungi
1998 - IRG/WP 98-10276
Biodegradation of cocopeat (coir dust) was enhanced by the addition of nitrogen (N) fertilizer and inoculation with the soft rot fungus Chaetomium globosum. The N and fungally treated cocopeats had a greater percentage weight loss (27%) after 3 months compared with 7% weight loss without the added fungi and N fertilizer. In addition, their hemicellulose, cellulose and lignin contents were greatly reduced. The decay patterns examined by light microscopy were typical of soft rot and included cavity formation. A bioassay using cress (Lepidium sativum L.) showed that root growth was inhibited by raw cocopeat extracts. This inhibitory effect was virtually eliminated in extracts from the biodegraded cocopeat. This suggests that the 'composted' cocopeat appeared sufficiently mature for use as a horticultural substrate after 3 months of biodegradation.
P Y Yau, R J Murphy

Confocal Laser Scanning Microscopy (CLSM) of decayed wood
1998 - IRG/WP 98-10273
Confocal laser scanning microscopy (CLSM) is currently being used to examine biodegraded wood and is proving to be a useful new technique in this area of work. Non-invasive optical sectioning within a thick specimen (20 - 50 µm), coupled with post image processing techniques allows manipulation of images and 3-D reconstruction from serial sections. Glutaraldehyde can cause cell autofluorescence, and since wood cell components do not react with it, a relatively simple technique for localising fungal hyphae, using glutaraldehyde as a fixative, was developed. Subsequent use of probes specific for chitin provided superior images of fungal hyphae in wood. High resolution, sequential, 2-D images can be produced to determine the mode of fungal attack within a thick wood specimen in a dynamic way. Voxel 3-D reconstruction of a series of image stacks enabled stereo viewing of objects.
Ying Xiao, R N Wakeling, A P Singh

Soft Rot Decay of Cengal (Neobalanocarpus heimii) Heartwood in Ground Contact in Relation to Extractive Microdistribution
2003 - IRG/WP 03-10501
The heartwood of cengal (Neobalanocarpus heimii, fam. Dipterocarpaceae) is naturally durable. A square-sawn utility pole specimen of cengal heartwood, after 30 years in ground contact, showed 10-15 mm surface decay all around the ground line position, accompanied with isolated surface termite attack at the decayed region. Light and transmission electron microscopy (TEM) of the decayed regions provided evidence of wood cell wall degradation by cavity-forming soft rot fungi. In the outermost layers, where such decay was most severe and severely discolored, all tissue types were degraded. However, in regions with moderate decay, differences in tissue types were observable in the extent of cell wall degradation. The presence of relatively intact vessels and parenchyma cells among heavily degraded fibres suggested that fibres were more susceptible to decay than vessels and parenchyma. Middle lamella was the only cell wall region which remained intact in all cell types which were severely degraded. Analysis of cengal heartwood revealed high contents of extractives soluble in hot water (14.1% m/m) or methanol (20.3% m/m), lignin (31.4% m/m) and phenolic materials (23.5% m/m), while microscopic observations provided information on the microdistribution of extractive materials. Vessels, fibres and parenchyma cells (both ray and axial parenchyma) all contained extractives in their lumen, but in variable amounts. The bulk of extractives were present in the lumina of fibres and parenchyma cells, filling them partially or completely. In vessels, only a thin layer of the extractives was present coating the warty layer. Brown coloration of cell walls in the light micrographs and their electron dense appearance in the TEM micrographs suggested that cell walls were also impregnated with extractives. This feature was typical of all cell types, but the amount and distribution of extractives was variable, judging by the variations in the coloration and density of cell walls. Overall, cell wall density of vessel and parenchyma cell walls appeared to be greater than that of fibre walls. TEM observations also provided evidence that pit membranes connecting parenchyma cells were well coated and impregnated with extractives, which was also found in the narrow canals of fibre pit pairs. Fungal hyphae were present in the extractive masses localized in cell lumina, and indications were that the extractives did not completely inhibit fungal growth. The microscopic observations suggested a close correlation between extractive microdistribution and the pattern and extent of cell wall degradation. In addition to fungitoxicity, the physical constraint of the extractive material present in cengal heartwood cells is likely to have a profound effect on restricting growth and pathways for cell wall colonization by soft rot fungi, thus conferring natural wood protection. Collectively, these observations suggest that both extractive content and their microdistribution are crucial in controlling wood decay, and should be closely examined to elucidate the role of heartwood extractives in wood durability and as natural preservatives.
A P Singh, A H H Wong, Yoon Soo Kim, Seung-Gon Wi, Kwang Ho Lee

Aspects of the fungal degradation of quaternary ammonium compounds in liquid culture
1997 - IRG/WP 97-30160
Didecyldimethylammonium chloride (DDAC) is a quaternary ammonium compound (QAC) that has found use as an anti-sapstain preservative for the transportation of softwood lumber from Canada to overseas markets. However, its use is limited by the knowledge that certain mould fungi seem capable of degrading it. The aim of this research was to gain knowledge about the fungal degradation of DDAC. The effects of Verticillium bulbillosum - a demonstrated QAC-degrading mould - on DDAC within a defined liquid culture were studied. Interactions between the liquid medium and DDAC; the degree of fungal tolerance under varying conditions; and rate of degradation paralleled with fungal growth were examined.
J W Dubois, J N R Ruddick

Bioremediation of surfactant contaminated waste
1996 - IRG/WP 96-50070
The objective of this work was to determine the potential of fungi as agents for the bioremediation of wastes (particularly wood and soil) contaminated with quaternary ammonium compounds (QACs). Until now only bacteria have been investigated for this purpose. Tolerant strains of Gliocladium roseum and Verticillium bulbillosum were studied for their ability to degrade the following QACs: didecyldimethylammonium chloride, cocoalkyltrimethylammonium chloride, and dicocodimethylammoium chloride. Preliminary experiments were used to determine the toxic threshold concentrations for selected QACs in solid and liquid media. As solid media, wood and soil were treatet with the different QACs and inoculated with one of the fungi. After a pre determined incubation period, the QAC was extracted from the wood and soil samples and the loss of chemical was measured by HPLC using an indirect photometric detection. Both fungi were able to degrade considerable amounts of all QACs tested under the experimental conditions.
J L Bürgel, J Dubois, J N R Ruddick

Fungal siderophores and their rôle in wood biodegradation
1990 - IRG/WP 1442
Iron and other metals such as manganese, play an important role in the metabolic functions of fungi that cause wood deterioration. These transition metals are also found in, or associated with, the extracellular fungal enzymes shown to be directly involved in the decay process. Recently our research group was able to show that siderophores (low molecular weight biological chelators) are produced by both brown and white rot fungi. These siderophores may function to scavenge transition metals for fungal metabolism and extracellular enzyme production. In addition, our preliminary work with the purified siderophores suggests that these compounds may play a more direct role in lignin modification, similar to that reported by other researchers investigating the properties of 'biomimetic' structures. Because of the low molecular weight of the siderophore-metal complex (500-1000 daltons), and the oxidizing potential of the bound transition metals, certain siderophore structures could also play a potential role in early stages of cellulose depolymerization by brown rot fungi. Developing a better understanding of the action of fungal siderophores, their role in scavenging metals for fungal metabolism, and their possible function directly in lignocellulose degradation, will help us to better understand how wood degradation occurs.
J Jellison, B Goodell, F Fekete, V Chandhoke

Micromorphology of decay in Keruing heartwood by the basidiomycetes Phellinus contiguus and Dacrymyces stillatus
2002 - IRG/WP 02-10454
This study aimed to characterise the micromorphology of fungal decay in a wooden handrailing in an above ground exposure at the Thames embankment in London. Keruing heartwood (Dipterocarpus spp.) was determined as the construction timber and the two basidiomycetes Phellinus contiguus and Dacrymyces stillatus identified as main decay organisms. Their decay patterns within Keruing heartwood were studied using light microscopy. Besides typical white and brown rot decay features the analysis also revealed cavities in the fibre S2 wall layers. A laboratory screening test with monocultures of both fungi confirmed their individual ability to form rhomboidal shaped cavities similar to those commonly associated with “true” soft rot fungi. This form of attack indicates that typical soft rot-like cavities can also be formed by white and brown rotting basidiomycetes facultatively and are therefore not an absolute indication for the occurrence of soft rot causing asco- and deuteromycetes respectively.
G Kleist, M Ray, R J Murphy

Variation in natural durability of British grown Douglas fir ((Pseudotsuga menziesii (Mirb.) Franco). Part II. Effect of extractive contents and taxifolin
2002 - IRG/WP 02-10446
The previous paper (Part I: Effect of density and growth rate) described the variation in natural durability of 4 Douglas fir (DF) seed origins (Darrington, J. Landing, Naselle and Hawkinsville) in a pure culture decay test and fungal cellar test. The pure culture tests were performed against two brown rot fungi (Coniophora puteana and Postia placenta). In the fungal cellar test soft rot was the predominant decay type because of the high moisture content. The paper showed that significant variation in natural durability occurred between the seed origins and between trees within the seed origins. Furthermore density partly explained the variation in the natural durability of 3, of the 4 seed origins. Extractives are often considered to be the major reason for heartwood durability. This paper has determined the variation in extractive contents between different seed origins and has examined the effect of extractive contents and taxifolin, the main component of acetone extracts on the decay resistance of 26 year old DF trees from different seed origins.
S Akhter, M D C Hale

Evidence for actinomycete degradation of wood cell walls
1990 - IRG/WP 1444
Several unique patterns of degradation occurring in wood cell walls have been observed in wooden stakes inserted in unsterile soil in the laboratory. Some of the patterns have also been observed in coniferous wood taken from forest floors. All the observed attack types occur within wood cell walls, mainly within the S2 layer. Attack is characterised by channels of varying diameter or small fusiform cavities arranged in the form of a rosette. Some channels are narrow, 0.5-1.0 µm, and form a highly branched network. Other channels are wider, up to approx. 2-3 µm and less branched. All channels are produced by hyphae growing within the wood cell walls. Attack has been observed to arise from the branching of thin hyphae growing longitudinally in the fibre lumina. The small diameter of the hyphae and the fact that these decay patterns have not been described for wood degrading fungi indicate that actinomycetes may be responsible.
T Nilsson, G F Daniel, S L Bardage

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

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