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Fungal and bacterial attack of CCA-treated Pinus radiata timbers from a water-cooling tower
1991 - IRG/WP 1488
Transmission electron microscopy of decaying CCA-treated Pinus radiata timbers from an industrial water cooling tower showed presence of a thick biofilm covering some areas of the wood. The biofilm contained various morphologically distinct forms of microorganisms embedded in a slime. The study provided evidence of the activity of soft rot fungi and tunnelling and erosion bacteria in wood cells. The extent of damage to wood cells due to microbial activity varied, combined fungal and bacterial attack having the most damaging impact.
A P Singh, M E Hedley, D R Page, C S Han, K Atisongkroh

Susceptibility of angiosperm sapwood to white-rot fungal colonization and subsequent degradation: a hypothesis
1997 - IRG/WP 97-10211
It has long been recognized that angiosperm sapwood in nature is relatively easily and preferentially degraded by white-rot fungi. This susceptibility to white-rot fungi is generally believed to be mainly caused by the structure and concentration of angiosperm lignin. However, an explicit explanation as to why lignin structure makes a particular wood vulnerable to white-rot colonisation and subsequent degradation has apparently never been given. We propose that free phenolic groups in wood, such as those present in the lignin or heartwood extractives, can act as free radical scavengers (antioxidants) which disrupt the various white-rot free radical degradative mechanisms. Consequently the presence of a relatively high free phenolic "density", such as that present in gymnosperm sapwood or angiosperm heartwood, may inhibit white-rot degradation. Conversely, white-rot fungi may find wood with a relatively low free phenolic content, such as angiosperm sapwood, easy to colonize. The complex structure of angiosperm wood, in which different cell types have different amounts and types of lignin -- and consequently different levels of free phenolic "densities" -- influences the susceptibility of angiosperm wood to initial white-rot colonisation and, perhaps, also the subsequent decay rate. In addition to the free phenolic ``density" other factors, some as yet unknown, undoubtedly also affect the decay resistance of a particular wood.
T Schultz, D D Nicholas

Use of fluorescent-coupled lectins as probes for studying fungal degradation of wood
1986 - IRG/WP 1288
The ability of the fluorescent-coupled lectins wheat germ agglutin (WGA) and Concanavalin A (Con A) to react with selected Basidiomycetes, Ascomycetes, and Fungi Imperfecti was evaluated using pure cultures of 35 fungi grown on malt extract agar. WGA, which binds specifically to the n-acetylglucosamine residues found in fungal chitin, reacted with nearly all hyaline fungal structures but did not react with dematiaceous (dark) structures. Several reasons are suggested for this variation. Con A, which is specific for a-D-mannosyl and a-D-glucosyl residues, reacted with about one half of the fungi that reacted with WGA. This variation in reactivity may be useful for studying simultaneous degradation by morphologically similar fungi having different lectin specificities. The results indicate that WGA is a useful probe for studying fungal degradation by non-dematiaceous fungi particularly at the early stages of decay.
J J Morrell, R L Krahmer, L C Lin

Fungal degradation of wood treated with metal-based preservatives. Part 2: Redox states of chromium
1996 - IRG/WP 96-10164
Concerns have arisen about the leaching of heavy metals from wood treated with metal-based preservatives, such as chromated copper arsenate (CCA). Of particular concern is the toxic redox state of chromium and arsenic in aging and decayed CCA-treated wood. Generally, hexavalent chromium is more toxic than trivalent chromium and trivalent arsenic is more toxic than pentavalent arsenic. The desired outcome from treating wood with CCA is total change of Cr(VI) to Cr(III) and As(III) to As(V). As part of an on-going study to determine the fate of copper, chromium and arsenic during aging and decay of CCA-treated wood, we detected Cr(III) and Cr(VI) in situ in CCA-treated southern yellow pine lumber. The redox states of Cr were determined using synchrotron X-ray fluorescence spectroscopy (SXRF). An SXRF microprobe was used to to detect Cr redox states by measuring X-ray absorption near-edge structure (XANES). The ratio of Cr(III) to Cr(VI) was determined (1) on the surface and interior of lumber two years after CCA treatment and (2) in lumber during decay by a CCA-tolerant fungus, Meruliporia incrassata TFFH-294. The XANES spectrum for Cr(VI) has a strong pre-edge feature that is not present in the spectrum for Cr(III). Only the Cr(III) XANES spectrum was detected on the surface and in the interior of the wood, indicating total reduction of Cr(VI). The XANES spectrum for Cr(III) was detected in wood after 12 week decay by Meruliporia incrassata TFFH-294, indicating that the fungus does not oxidize Cr(III) to Cr(VI) during the decay process. We are currently using XANES spectroscopy to detect and map in situ redox states of As in CCA-treated wood.
B Illman, S Bajt, T L Highley

Effect of felling time related to lunar calendar on the durability of wood and bamboo -Fungal degradation during above ground exposure test for 2 years- (Preliminary report)
2005 - IRG/WP 05-20311
Current study was carried out to know whether the felling time of trees and bamboos based on lunar calendar affects natural durability of felled wood-bamboo or not. Each of one sugi (Cryptomeria japonica) tree of 28 years old and one Moso bamboo (Phyllostachys heterocycla) of around 3 years old was cut 12 times between February and December in 2003. Six sets of sugi tree and bamboo were felled in a day during “Hassen” period and the other 6 sets of them were also felled in a nearby non-“Hassen” day. There is a belief that “Hassen” should be avoided to perform destructive works such as cutting trees. “Hassen” lasting 12 days based on lunar calendar appears 6 times every year. After felling sample trees and bamboos, these specimens were subject to outdoor exposure at above ground level for 2 years. Properties of specimens such as moisture contents, mould and fungal resistance were examined periodically for 2 years. There was no clear difference in the degree of mould growth on the surface between specimens felled in a “Hassen” day and those felled in a non-“Hassen” day in the same month. The felling seasons, however, influenced the growth of mould on the surface of wood and bamboo clearly, which has been traditionally known in many cases. Fungal degradation evaluated by visual observation and the depth of pin penetration using Pilodyn during 2 years exposure was not affected by not only “Hassen” or non-“Hassen” also seasons when tree and bamboo felled.
K Yamamoto, S Uesugi, K Kawakami

Wood-based composites exposed to fungal degradation: Laboratory results
2001 - IRG/WP 01-40215
Oriented strandboard (OSB) and laminated veneer lumber (LVL) are widely used as residential construction materials. The durability of OSB and LVL against biological degradation has not been studied comprehensively. The objective of this research was to investigate the durability of OSB and LVL when exposed to wood decay fungi. Fourteen brown-rot and eight white-rot wood decay fungi were screened for their capacity to degrade OSB and LVL. Samples were evaluated for decay by weight loss measurements using the American Society for Testing and Materials D1413-76 soil block test method. Results revealed that the brown-rot fungus Gloeophyllum trabeum (Mad-617) and the white-rot fungus Trametes versicolor (Mad-697) degraded OSB to a greater extent than solid southern yellow pine wood. Both fungi degraded LVL to a much lesser extent than OSB. Our findings provide valuable information on the durability of OSB and LVL, to predict serviceability and protection requirements of these construction materials.
V W Yang, B Illman, L A Ferge, R J Ross

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

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

Effect of some resin treatments on fungal degradation reactions
1999 - IRG/WP 99-10318
The effect of impregnation of wood with vegetable oil, tall oil and two water soluble on fungal degradation reactions was assessed by hydrolysis and enzyme activity measurements. The experiments were carried out by using isolated enzyme preparations and a living brown-rot fungus Poria placenta. The results indicate that the inhibitory effect of treatments was clearly directec towards the enzymatic hydrolyzability of the hemicellulosic and cellulosic components of wood cell wall. The water soluble resins and tall oil treatments significantly decreased the ability of isolated enzyme preparation to hydrolyse treated wood substrate. The inhibitory effect of these treatments was focused on the degardation of arabinoxylan and cellulose components of the wood cell wall. The vegetable oil treatment did not significantly prevent the enzymatic hydrolysis of wood substrate. The resin and tall oil treatments seemed also to interfere the production and/or mode of action of hydrolytic degradation pathway of living brown-rot fungus P. placenta.
A-C Ritschkoff, M Rättö, A J Nurmi, H Kokko, A O Rapp, H Militz

The influence of staining fungi on the decay resistance of wood treated with alkylammonium compounds
1984 - IRG/WP 3308
Although found to be very effective in laboratory tests, alkylammonium compounds (AAC's) have failed to perform as well in field stake tests. Examination of leachability showed that this was not the cause. The present study investigated the possibility that staining fungi, (which have been observed to rapidly infect the field stakes), degrade the AAC wood preservative. Soil-blocks were treated with alkyldimethylbenzylammonium chloride, and sterilized, using gamma radiation. Half of the blocks were exposed to a mixed suspension of staining fungi, which had previously been isolated and identified from failed dialkyldimethylammonium chloride-treated stakes. After incubation for ten weeks they were conditioned, and one half leached in a static seven day leaching cycle. Half of the blocks not exposed to the staining fungi were also leached in a similar manner. All the blocks were then sterilized prior to exposing to one of three decay fungi, Lentinus lepideus, Gloeophyllum trabeum and Poria placenta. Following the test, Lentinus lepideus was found to be least tolerant to the AAC wood preservative, while Poria placenta was the most tolerant fungus. The Poria pre-exposure of the soil blocks to staining fungi greatly increased the toxic threshold and toxic limits of AAC to both Gloeophyllum trabeum and Poria placenta. The increases were almost independent of leaching, suggesting that degradation of the AAC is taking place rather than rupture of the AAC-wood substrate bonding. The increase in the toxic threshold to ca 9 kg/m³ would clearly have caused failure of the stake material in test at Westham Island, since the maximum concentration in that test was only ca 10 kg/m³.
J N R Ruddick

Fungal detoxification of organotin biocides
1985 - IRG/WP 1258
The ability of a range of wood decaying fungi to inactivate bis(tri-n-butyltin) oxide (TnBTO) in the extracellular growth medium, in stationary liquid culture was determined. A distinction between the ability to tolerate the fungicide and to inactivate it was made: the white-rot organism Coriolus versicolor being the most efficient inactivator. In an attempt to determine the extracellular agents responsible for any detoxification, Coriolus versicolor was shown to produce significantly greater levels of extracellular free radicals/peroxidase. Preliminary tests have shown the nature of the associated anion on the fungicide effects the susceptibility of tributyltin compounds to free radical attack in a chemical system. The ability of an free radical scavenger to reduce detoxification in such a system has also been demonstrated.
P S Belford, D J Dickinson

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

Degradation of resin constituents in various wood species by the white rot fungus Bjerkandera sp. strain BOS55
1999 - IRG/WP 99-10301
In previous studies, the white-rot fungus Bjerkandera sp. strain BOS55 was shown to cause extensive degradation of lipophilic extractives (resin) in Scots pine wood. Further research was carried out in order to investigate the ability of Bjerkandera sp. for reducing resinous constituents in various softwood (Douglas fir, larch and spruce) and hardwood species (birch, beech and poplar). The greatest resin reduction occurred in beech (79% in two weeks). High levels of resin elimination were also observed in softwood species like spruce (36%) or Scots pine (35%), as well as in hardwood species like poplar (32%) or birch (24%). In contrast, Bjerkandera sp. only caused a negligible loss of resin components in Douglas fir wood chips. HPLC analysis of acetone extracts from control and fungal-treated samples showed a rapid elimination of triglycerides, diglycerides, free fatty acids and sterols. Toxic constituents in softwood species like resin acids were partially removed in Scots pine, spruce and larch (29-34% in two weeks).
J Dorado, T A Van Beek, F W Claassen, R Sierra-Alvarez

Effect of fungal degradation on the chemical composition of acetylated beech wood
2003 - IRG/WP 03-40267
This study investigated the impact of fungal attack on the chemical composition of acetylated wood. Beech wood acetylated to different degrees was exposed to decay by the white-rot fungus Trametes versicolor under solid-state fermentation conditions. Laboratory soil-bed assays were also conducted to study the degradation of acetylated wood by soft rot fungi and other soil-inhabiting microorganisms. Changes in the chemical composition of untreated wood and acetylated wood following exposure to fungal attack were examined by wet chemical analysis, as well as FT-IR and CP/MAS 13C-NMR spectral methods.
H Militz, Dong-won Son, L Gómez-Hernández, R Sierra-Alvarez

Fungal degradation of wood treated with metal-based preservatives. Part 1: Fungal tolerance
1996 - IRG/WP 96-10163
In recent years, concerns have arisen about the leaching of heavy metals from wood treated with chromated copper arsenate (CCA), particularly because of the large amount of CCA treated wood that will be discarded in the coming years. The long term objectives of this work are to determine the fate of copper, chromium and arsenic with the aging and potential decay of CCA-treated wood, and to develop strategies for recycling and remediation of disposed wood. In this study, we determined the ability of various decay fungi to decompose southern yellow pine wood treated with CCA or other metal-based preservatives. Isolates of Meruliporia incrassata and an isolate of Antrodia radiculosa caused the highest weight losses in CCA-treated southern yellow pine. One isolate of Meruliporia incrassata produced similar weight losses in CCA-treated and untreated southern pine after 10 weeks. Pine samples treated with very high levels of copper sulphate were decayed by Meruliporia incrassata, but the fungus was unable to decay wood treated with copper napthenate or copper-8-quinolinolate.
B Illman, T L Highley

Fun with Soil Block Jars: Teaching fungal wood decay in the classroom
2006 - IRG/WP 06-10574
In this world of increasing complexity and technological advancements, it is ever more important to raise scientifically literate children. The National Science Foundation Teaching Fellowship Program (NSF GK-12) at the University of Maine provides an opportunity for advanced graduate students in science, mathematics and engineering to bring their knowledge, as well as the latest equipment, to students in local area schools. Our goal was to provide an environment where students could begin to think critically about fungi and their role in the degradation process, as well as the overarching importance of the scientific method as a tool of discovery. Students participated in a major soil block jar survey of local fungi, from initial culturing of the organisms from the wild through the final harvest and data analysis. The process of testing the wood-decaying capacity of these fungi provided an interesting and informative way of furthering student’s knowledge of the scientific method while introducing them to the concepts associated with fungal wood decay.
C Howell, L Gott, B Meehan

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

The chemistry of wood degradation by Basidiomycetes studied in a van Krevelen diagram
2013 - IRG/WP 13-10805
The atomic composition ratios of decayed wood by Basidiomycetes are mapped in a van Krevelen diagram. It is shown that the wood residue after decay is chemically reduced, rather than oxidized. A previously developed and verified theoretical model for thermal wood modification, relating atomic composition ratios to moisture sorption and fungal resistance properties has tentatively been applied to wood modification by Basidiomycetes-attack. It is argued that some of the reaction mechanisms, activated by heat during thermal modification, may also become activated in wood under fungal attack.
W Willems, H Militz

Application of a model for the prediction of fungal degradation of thermally modified beech timber by Trametes versicolor
2013 - IRG/WP 13-40622
Colour measurement technology is found to be feasible for characterization of the property changes of thermally modified timber (TMT). In opposite to time-consuming and expensive laboratory tests a non-destructive test represents an improvement for the manufacturer of TMT. Therefore the aim of this study was to develop a method which allows sorting the different treatment intensities after the manufacturing process separately from each other, so as to help the manufacturers to ensure product quality. For TMT of beech wood a correlation of process-related decrease in mass to L*b*-colour-values was proved. Furthermore, linked to higher treatment intensities the fungal-related mass loss of TMT decreased. Fungal tests with Trametes versicolor indicated that the individual changes of the specimens need to be considered during the sorting of the durability classes. Therefore the development of the method of quality assurance is not directed to the production batches and thus determined averages, but by correlations of the parameters. With a selected model, parameters, e.g. durability, were calculated as a function of colour values. But the prediction of durability classes of TMT, based on colour values was feasible only to a limited amount of samples. The prediction of a durability class 2 or 1 seems to be feasible for treatment intensity of temperatures ≥ 220 °C.
Clauder, L., Richter S., Unger, W., Pfriem, A

Foundation piles: analysis of beech wood decay in service life conditions
2016 - IRG/WP 16-10858
Wood piles foundation system was largely used over decades. Thus, numerous buildings over the world are based on this constructive system. In the context of reduction of CO2 emissions in the building field of constructions, substitution of concrete by wood as material for foundation piles seems to be a promising alternative. However, fluctuation of the water table level in soil may promote fungal decay of the wood foundation piles in service. Thus, wood used as foundation pile was often treated with high toxicity chemical products. To promote the use of wood in pile foundation on the basis on its natural durability, diagnostic and prediction methodology of the wood decay needed to be improved. Mesocosm decaying experiments were carried out on beech wood mini-stakes. Influence of a water gradient occurring in wood on its strength loss was evaluated. Compression parallel to the grain (fc,o), fungal colonization of wood, near infrared spectroscopy and enzymatic activities measurements were used to decipher wood decay. However, none of these factors was fully accurate when considered alone. Indeed, degradation pattern seemed to be patchy due to high heterogeneity of the wood and repartition of microorganisms in soil. It turned out that no optimal correlation could be found after an one factor analysis. At the contrary, multivariate analysis allowed an accurate clustering of the wood samples. This approach discriminated between samples with identical fc,o value but that differed by their enzymatic activities and cell wall polymer contents. Finally, a predictive model of the fc,o was built. The model had the potential to predict the fc,o of a wood foundation pile from on-site measurements. Relative part of the enzymatic activity in the wood decay dynamic is also discussed.
Q Kleindienst, A Besserer, M-L Antoine, C Perrin, J-F Bocquet, L Bléron

Production of reactive oxygen species in the presence of oxidized iron and oxalate under conditions mimicking brown-rot fungal degradation of wood
2016 - IRG/WP 16-10861
The biochemical role of oxalate in the fungal solubilization of iron is well known, but additional information is needed on the role that oxalate plays in the brown-rot decay of lignocellulose. In this study iron sequestration from iron and iron oxide-hydroxides was assessed with regard to the function of a chelator-mediated Fenton (CMF) reaction and the generation of reactive oxygen species (ROS). The reactions conducted at the lowest pH condition (pH 2.0) and oxalate concentration (15μM) generated the greatest amount of FeII, suggesting that pH, rather than oxalate concentration may have a greater impact on Fenton reactions, and specifically the CMF reaction. Moreover, iron oxide-hydroxides that were pre-incubated with oxalate prior to the CMF reaction, generated more ROS than the iron oxide-hydroxides without oxalate incubation. This indicates that an enhanced CMF reaction was promoted by iron sequestration due to oxalate incubation, and also supports previous research showing a pH-dependent iron transfer from oxalate to chelators produced by fungi. Although Fenton reactions were enhanced at low pH, the iron transfer reaction was enhanced at higher pH. In a decay environment, this would limit damaging Fenton reactions from occurring in the low pH environment directly surrounding the fungal hyphae.
Yuan Zhu, Liangpeng Zhuang, B Goodell, Jinzhen Cao, J Mahaney

Fungal decay of archaeological waterlogged oak timber: role of the mineral content
2016 - IRG/WP 16-10873
In service, wood foundation poles are subjected to water level fluctuation in soil. While wood is saturated by water only bacterial decay occurs. When oxygen content increases and moisture content decreases, severe fungal attack may occur. To evaluate the long term fungal durability of wood foundation pole in the context of service, 300 years waterlogged archaeological wood poles were used. The oak wood was characterized and subjected to fungal degradation in controlled conditions. Upper part of the pole was only subjected to water. It was analysed separately of the buried part. Before fungal attack, mechanical resistance of wood was similar to current oak. Global chemical composition showed only small alterations in wood polymer contents. Extractive and ashes amounts exhibited the highest differences when compared to current oak. Transmitted infrared spectroscopy showed that cell wall carbohydrates content was decreased at low level in archaeological samples compare to current heartwood. The ashes composition analysis of archaeological wood samples revealed unusual high level of iron and calcium. Scanning electron microscopy with microanalysis analysis showed that wood anatomy was altered. Minerals were homogeneously localized in wood structures. When subjected to fungal degradation, archaeological woods were more degraded by white and brown rots than current oak heartwood samples. Role of iron in oxalate mediated Fenton degradation mechanism was investigated. In archaeological wood samples degraded by Poria placenta and Coniophora puteana high number of crystal structures surrounding hyphae were observed and identified as calcium oxalate. The possible inhibitory role of high iron content on Trametes versicolor wood degradation is also discussed. Finally, this work point the role of metal cations adsorbed in wood during the fungal degradation of the material.
A Besserer, M Letellier, E Fredon, Q Kleindienst, M-L Antoine, C Perrin, J Lallemand, C Rose, M-C Trouy

Estimation of wood degradation determined by visual inspection, mechanical testing and DNA characterisation – report after 3 years of exposure
2016 - IRG/WP 16-30700
The influence of two separate treatments, thermal modification and alkaline copper quaternary (ACQ, Silvanolin©) treatment, on fungal decay, visual disfigurement, deterioration in mechanical properties and fungal community structure was assessed on Norway spruce (Picea abies) and compared with the performance of two naturally more resistant tree species native to North America: Douglas fir (Pseudotsuga menziesii) and Western red cedar (Thuja plicata). Wood samples were exposed to environmental conditions and collected annually over three years. Samples were visually examined and rated for decay and disfigurement then evaluated to failure in three-point loading to determine flexural properties and, finally, DNA was extracted from the samples and analyzed to determine the fungal community present. As expected, there were substantial differences in visual ratings, fungal colonization and flexural properties. Further assessments are planned.
N Thaler, T Martinović, M Bajc, D Finžgar, H Kraigher, A Sinha, J J Morrell, M Humar

Effects of wollastonite nanofibers on biological resistance of historical paper against Aspergillus niger
2017 - IRG/WP 17-10878
Effect of wollastonite nanofibers on biological resistance of historical paper against Aspergillus niger was studied. Specimens from A4 papers were also prepared for comparison purposes. Paper specimens were dipped in aqueous nanowollastonite (NW) with 10, 20, 30, and 40% concentrations and compared with control specimens. In order the nanofibers be fixed on paper specimens, 5% of polyvinyl acetate (PVA) resin was added to all nanosuspensions. Moreover, in order to find out the effect of PVA on fungal growth, a separate set of specimens was prepared dipped in a 5% resin solution, without nanowollastonite content. Results clearly demonstrated the preventing effect of wollastonite nanofibers on the growth of A. niger, resulting in significant decrease in weight loss as NW-content increased. It was concluded that as to the mineral, non-toxic, and non-acidic nature of wollastonite, it can effectively be used for paper preservation and conservation purposes. In this regard, NW-content of 20% is recommended to the industry to both achieve a high level of protection against A. niger, and keep the preservation costs to the minimum level.
H R Taghiyari, A Kalantari, A Ershad-Langroudi, A Kalantari

The Protective Effect of Different Tree Bark Extractives against Decay Fungi
2017 - IRG/WP 17-30707
There are various modification methods which increase the resistance of wooden materials. Due to recent environmental regulations, there is a need for new and environmentally-friendly wood preservatives. In this study, six different tree bark extractives were evaluated for their wood resistance against fungal degradation. For this purpose, the white rot fungi (Tramates versicolour) and brown rot fungi (Coniophera puteana) were used to determine the level of resistance of the tree bark extractives. The tree bark extractives demonstrated high resistance to fungi decay. Different tree bark extractives prevented fungus degradation for both fungi. SEM images also exhibited this phenomenon. The wood samples treated with extractives were covered with less hyphae as compared to the control samples. The tree bark extractives can be evaluated in a wood protection area.
Ö Özgenç, S Durmaz

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