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Enhancing Our Understanding of Brown Rot Mechanisms through Catalytic Pretreatment and Cellulase Cocktail
2018 - IRG/WP 18-10909
A catalytic mechanism, described as the “chelator-mediated Fenton” (CMF) mechanism, is proposed to mimic the non-enzymatic action of brown rot fungi. A CMF treatment was used together with an enzymatic cocktail to study how wood was deconstructed and solubilized. This was done in-part to determine if the treatment mimicked the action of brown rot fungi, but also to explore improved treatment processes for bioprocessing of woody biomass. Our data suggest that the CMF mechanism is highly efficient in overcoming the lignin recalcitrance barrier to solubilize wood. Multiple pulses (up to 4 pulses) of CMF treatment were able to solubilize a majority of both the lignin and cellulose of wood at room temperature, using a hydrogen peroxide concentration of only 1%. Using a single pulse of the CMF system as a pretreatment allowed more wood residue to be retained, and enzymatic action on this pretreated wood was enhanced compared to control wood. In separate experiments, significantly greater solubilization of both sugars and lignin occurred when a single-pulse CMF pretreatment was used prior to enzymatic action than by enzymatic action alone on unmodified wood. This work suggests a key reason why the brown rot fungi have abandoned many of their extracellular enzymes to produce only a select suite of cellulases, which the fungus employs after prior modification of the cell wall using a CMF mechanism. This research further suggests that the CMF mechanism may have potential to be adapted for bioprocessing of woody biomass to produce sustainable fuels and bioproducts in the future.
S Tabor, L Orjuela, D Contreras, G Alfredsen, J Jellison, S Renneckar, B Goodell

Non-enzymatic Gloeophyllum trabeum decay mechanisms: Further study
2001 - IRG/WP 01-10395
Information will be presented on the mechanisms involved in, and potential application of, non-enzymatic wood decay by brown rot decay fungi. Specifically, the hypothesized role of low molecular weight phenolate derivatives will be discussed in relation to non-enzymatic degradation of wood. The mechanism of binding of iron by cellulose, and binding and reduction of iron by fungal derivatives and model compounds is examined. Positive and negative aspects of potential application of these compounds in the generation of free radicals will be discussed.
B Goodell, J Jellison

Detection of semi-quantitative and qualitative enzymatic activities of blue-stain fungi
2000 - IRG/WP 00-10347
Blue-stain, produced in forests, continues to be a problem in countries of moderate climate. In forestry, in certain geographical areas of Spain, it has been observed that anti-sapstain products have not always been efficient, as their fungicidal effectiveness varies on occasion, depending on the species of wood and microbiota that exist in the region. It is not always easy to identify the species causing this damage. Therefore, the object of this study was the grouping of diverse isolates according to the detection of simple enzymatic activities, following a simple and rapid method of application such as API-ZYM. 36 strains of Ceratocystis spp, isolated from divers species of Pinus spp., have been tested. The results were contrasted with the activities detected in the same conditions in Pullularia pullulans and Sclerophoma pityophila. To do this, these strains were inoculated in culture broths with a basic saline Eggins and Pugh medium, to which 1% sawdust of Pinus sylvestris was added in one trial. Another test was made with a mixture of the most frequent monosaccharides in woody cell-walls (glucose, mannose, galactose, arabinose, and xylose) at 1%. After 20 days of incubation, the extracts were centrifuged, and inoculated in microtubes series of API-ZYM. The analysis of the principal components, carried out with the results obtained, showed that the sawdust induces enzymatic activities implicated in the degradation of polysaccharides such as in a-mannosidase, a-galactosidase, b-glucuronidase, b-glucosidase and b-galactosidase, which appeared as the most weighty specific factors in the dispersion of data on the first two principal axes. Different strains of Ceratocystis also showed similar or greater activity than those of P. pullulans and S. pityophila, which suggests that the latter might be more virulent than the rest of the strains assayed.
M T De Troya, F Llinares, D Muñoz-Mingarro, M J Pozuelo, N Acero, C Rodríguez-Borrajo, A M Navarrete

Enzyme systems of bacterial isolates from ponded logs - Potentials of pectin and/or starch degradation
2000 - IRG/WP 00-10378
This paper deals with the degradation potentials of wood constituents by the bacterial isolates from ponded logs. The potentials to degrade pectin as a constituent of pit-tori as well as starch existing in ray parenchyma cells in the areas of sap- and transition wood with the isolates were examined. The pectinase activity was investigated by means of the degradation degree of a carrot strip used as a single carbon source in a liquid medium. The amylase activity was studied by the colour change on the iodostarch reaction in an agar medium containing soluble starch as a single carbon source. The results suggested that these substrates were degraded sequentially by plural bacterial species that invaded in the logs during ponding.
S Doi, S Ohta

Reaction of osmium tetroxide with a diphenolic compound as a model substance for demethylated lignin
1986 - IRG/WP 1303
By using caffeic acid as a model substance for diphenolic moieties of demethylated lignin it was found that electron dense particles called by the authors "osmiophilic particles" in former papers are reaction products of OsO4 with the model substance. By these products it is possible to indicate the enzymatic demethylation of lignin taking place during wood decay. The appearance of the electron dense particles in decay patterns described in earlier papers is briefly summarized.
K Messner, E Srebotnik

Evidence for the participation of the osmiophilic particles in the enzymatic demethylation of lignin
1984 - IRG/WP 1239
Transmission electron microscopic observations of the white-rot fungi Trametes hirsuta and Phanerochaete chrysosporium grown on a series of wood pulp with a graded lignin content and mycelium from the clarified centre of an agar-medium containing lignin (E1-effluent from the bleaching process) showed that osmiophilic particles are only induced by native lignin. Taking into account that the osmiophilic particles are also produced by brown-rot fungi the conclusion is drawn that they take part in the enzymatic demethylation of lignin. Their distribution over surfaces embeded in a slimy matrix correlates with their appearance in wood.
K Messner, H Stachelberger

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

An alternative method for the determination of lignocellulolytic enzymatic activities of white rot fungi
1998 - IRG/WP 98-10261
Some lignocellulolytic activities of wood decay fungi can be evaluated in an indirect way through the study of the decolorization that white rot fungi produces in culture media in the presence of dyes. In this assay, ten dyes were selected, which were added in concentrations of 0.00 1% - 0.003% (P/V) to four-day cultures of Trametes versicolor containing 1% of beech sawdust in a basal salt medium. After the addition of the dye and at seven-day intervals, aliquots were taken in aseptic conditions in order to determine the following parameters: pH, loss of colour, and laccase and Mn-peroxidase activity. All of the cultures and determinations were carried out in triplicate and contrasted with noninoculated controls, as well as with controls that were inoculated, but with no stain added. The results obtained showed that the fungi produced decolorization in all of the cases. The linear regression analysis of the data of residual color (as absorbance), contrasted with the lignocellulolytic activities, showed significant regression coefficientes (p<0.05) in the cultures with Methyl Red, Safranine, Crystal Violet and Blue Eosin. In an additional experiment, sonicated and non-sonicated extract were incubated with Methyl Red solutions (significant regression coefficient) and Bromophenol Blue (non-significant regression coefficient), independently, for three hours. The results showed that there are no notable differences between the sonicated samples and those that were not sonicated in a medium with Methyl Red, whereas in a medium with Bromophenol Blue, decolorization was produced only in the presence of the sonicated extract. This would indicate that the decolorization of Methyl Red can be carried out by extracellular components of the culture, while Bromophenol Blue requires the action of intracellular components to become degraded. This might explain the significant correlation mentioned earlier.On the other hand, the nature of the dyes may influence the magnitude of the activities described: thus it is seen that with Bromophenol Purpel and Crystal Violet, significantly higher values of activities than those of the control without a dye are obtained, while with Malachite Green, the activity is significantly lower.
D Muñoz-Mingarro, F Llinares, F Rubio, M Yuste, C Rodríguez-Borrajo, J Jiménez, M T De Troya

Enzymatic study of Ceratocystis sp., blue-stain fungi on Pinus nigra
1999 - IRG/WP 99-10315
One of the main problems that the forest exploitation industry has with Pinus nigra wood is the blue-stain fungi, whose causing agent is unknown. Therefore, the objective of this work has been to study, through enzymatic tests of the isolated cultures, if these fungi infect Pinus nigra in any specific way. After the incubations, isolates of Ceratocystis were obtained. These were cultured in a saline medium with sawdust of Pinus nigra and Pinus sylvestris, which were used as reference species. At different incubation times, carboxymethylcellulase, xylanase, cellobiohydrolase, laccase and manganese peroxidase were determinated. The results obtained show that the cellulolytic enzymes and laccase have higher activity on Pinus nigra sawdust than on Scots pine, while the Mn peroxidase showed higher values on the sawdust of the latter. Likewise, the cultures were developed in the same saline base medium with different monosacarides (glucose, galactose, mannose, xylose and arabinose), and in determining the residual sugar content, a marked prefrence for the consumption of pentoses in respect to the glucose was observed. The enzymatic activity tests carried out by APY ZYM also showed qualitative and semiquantitative differences between the isolated fungi and other Ceratocystis species tested, so, in addition to the above results, this could indicate a certain specificity of these fungi for this wood species.
M T De Troya, F Rubio, D Muñoz-Mingarro, F Llinares, C Rodríguez-Borrajo, M Yuste, M J Pozuelo, J I Fernández-Golfín

In situ testing the influence of melamine resins on the enzymatic activity of basidiomycetes
1999 - IRG/WP 99-30194
Waterbased methanol etherificated melamine formaldehyde resins have the potential to increase the resistance of impregnated wood against wood destroying fungi. The mechanism of the increased wood durability is not clear yet. In the present paper the possible interference of melamine resins with wood degrading enzymes of Coniophora puteana and Trametes versicolor was investigated as a possible contribution to the increased wood durability. An in situ photometric assay was used to measure the enzymatic activity against Walseth cellulose, pine sapwood as well as lignin and xylan preparations.
D Lukowsky, F Büschelberger, O Schmidt

Investigation of new wood preservation formulations based on synergies between antioxidant, 2-HPNO and Propiconazole
2006 - IRG/WP 06-30401
Wood degradation by fungi is a complex phenomenon taking place in part through oxidative reactions involving many oxidizing agents like free radicals and hydroperoxide. In order to develop novel and more environmentally benign preservative systems, mixtures of Propiconazole and antioxidants with different stabilization mechanisms were investigated to detect possible synergies allowing to reduce the quantity of biocide to prevent wood biodegradation. Results obtained showed that the nature of the antioxidant had an important effect on the potential synergies. The most interesting results were obtained with 2-HPNO and hindered amine and to a weaker extend with H-donors like hindered phenol.
B Bakhsous, S Dumarçay, E Gelhaye, P Gérardin

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

Aislamiento, identificación y evaluación enzimática de hongos de pudrición de madera de la Región de los Lagos
2008 - IRG/WP 08-10680
So far, systematic investigations have not been developed to determine the fungal diversity associated with wood in Chile. In addition, little is known about the mycoflora capabilities or their enzymatic processes in biotechnology although different research has hinted at the great potential of these microorganisms in various industrial processes. The aim of this work is to isolate, identify and enzymatically evaluate wood decay fungi present in national parks located in Chile’s Región de los Lagos. The research will be divided into three stages: isolation, identification and qualitative enzymatic evaluation of the microorganisms. A classification of the identified fungi according to the enzymatic activity observed (cellulotic, hemicelullotic, peroxidase, or laccase activities) is expected to be generated. This paper contains the research methodology and literature review of this project. En la actualidad no se han desarrollado investigaciones sistemáticas que permitan determinar la diversidad fúngica presente en maderas de Chile. Así mismo, el conocimiento acerca de sus capacidades enzimáticas y aplicabilidad en procesos biotecnológicos ha sido parcialmente desarrollado. No obstante lo anterior, diversos antecedentes muestran un gran potencial de estos microorganismos en diferentes procesos industriales. El objetivo de este trabajo es aislar, identificar y evaluar enzimáticamente los hongos de pudrición obtenidos de maderas presentes en parques nacionales ubicados en la región de los Lagos en Chile. La investigación, para el logro del objetivo planteado, será dividida en tres etapas: aislación, identificación y evaluación enzimática cualitativa de los microorganismos. A partir de este trabajo se espera conocer la micoflora existente en la zona bajo estudio. Así como también clasificar, según la actividad enzimática observada, las especies de hongos identificados.
R Ortiz, J Navarrete, C Oviedo, R Blanchette

Chemical mediated depolymerization of cotton cellulose for the understanding of non-enzymatic fungal decay
2010 - IRG/WP 10-10731
Small, low molecular weight non-enzymatic compounds have been linked to the early stages of brown rot decay as the enzymes involved with holocellulose degradation are found to be too large to penetrate the S3 layer of intact wood cells. The most pronounced of these which were analyzed in this study are hydrogen peroxide, iron, and oxalic. The compounds related to the Fenton reaction: the combination of hydrogen peroxide and iron caused marked lowering of the degree of polymerization in the cotton cellulose after treatment. This was the case for both iron ions; Fe3+ and Fe2+. A 10mM solution of oxalic acid also showed significant depolymerizing effect on cotton cellulose, whereas diluting the oxalic acid with sodium oxalate to obtain a pH gradient, showed that this decreased the effect reducing of oxalic acid. In addition an organic iron chelator, EDTA, was tested but was found to inhibit depolymerization when in solution with chemicals related to Fenton chemistry. Manganese was tested to see if other metals than iron could generate an significant impact on the degree of polymerization of cotton cellulose and the metal showed good depolymerizing properties as a substitute for iron. We conclude that low molecular weight metabolites are capable of effectively depolymerizing cellulose during incipient decay by brown-rot fungi.
A C Steenkjær Hastrup, B Jensen, F Green III

Wood decay enzymatic ability of Fusarium circinatum
2012 - IRG/WP 12-10777
There exists pathogens that attack standing trees of forests, and do not usually thrive once the tree is felled. However, occasionally they can be present in a latent state in the wood and can spread and affect new areas with economic, ecological and social consequences. Fusarium circinatum is a fungus that causes “pitch canker” in pine species, and is considered a quarantine organism within the European Union. Some studies have reported that this fungus can survive in wood wastes, however no studies to show what kind of substrates, and if the affected wood losses its physico-mechanical properties. In this paper has been studied the possible degradative capacity of Fusarium circinatum on Pinus radiata. Two tests were carried out, one to determine weight loss of wood with varying degrees of nutritional richness, and another to determine the lignocellulolytic activities of two isolates of Fusarium circinatum. The results showed that both presented hemicellulolytic and cellulolytic activities, but not ligninolytic. This degradative ability could affect the quality of felled wood and consequently adversely affect the industrial sector.
M T Troya, F Llinares, Y Serrano, M Conde

Scanning Transmission X-ray Microscopy as a tool for examining chemical changes in wood cell walls due to enzymatic activity
2014 - IRG/WP 14-20556
As development of techniques for examining enzymatic activity on solid, complex biological materials, is considered to be an important factor in further development of enzyme applications and for understanding the decay of plant materials, this study explores applicability of Scanning Transmission X-ray Microscope (STXM) for determining chemical changes in enzymatically treated samples at the cell wall level. STXM was an instrument of choice for the study due to its capability to differentiate organic compounds at a spatial resolution comparable to an electron microscope. By treating aspen slivers with solutions of either individual or mixtures of enzymes, we confirm the synergistic activity of laccase and xylanase enzymes, and indicate possibility of penetration of small enzymes into the cell wall structures.
D Jeremic, R Goacher, R Yan, C Karunakaran, E R Master

Possible targets of wood modification in brown rot degradation
2014 - IRG/WP 14-40676
Wood modification protects wood from fungal degradation in a non-toxic manner. However, the mechanisms behind the decay resistance in modified wood are currently unknown. The aim of this study was to discuss the i) colonisation, ii) nutrient recognition, iii) transcription, iv) depolymerisation and v) hydrolysis steps in the brown rot degradation progress and explore whether they are inhibited by wood modification, based on new and previously published data from our group. In previous studies, it has been shown that fungi were able to colonise modified wood, to recognise it as a source of nutrients and express genes associated with cellulose degradation while growing on modified wood. In this study, Fenton derived hydroxyl radicals (∙OH) and brown rot cellulases were able to degrade modified wood. We conclude that the five degradation steps discussed in this paper are unlikely targets for wood modification and that wood modification rather inhibits a step that in a schematic overview of the brown rot degradation process is downstream from transcription but upstream of depolymerisation and hydrolysis.
R Ringman, A Pilgård, G Alfredsen, B Goodell, K Richter

A novel enzymatic treatment as a new approach for wood protection
2015 - IRG/WP 15-40701
Wood durability is a worldwide concern and most treatments tend to fail with regard to their efficacy along the time. Weather conditions lead to a loss of the treatment substances into the surrounding environment and, in consequence, generate also a public health concern. Recently, the employment of oxidative enzymes, such as laccases, has been proposed as a tool for lignocellulosics modification in order to change wood surface by anchoring compounds that confer new properties to wood. Among the advantages of this strategy, it can be highlighted the fact of the formation of covalent bonds between the wood and the compounds of interest. Consequently, future leaching of the linked substances is expected to be avoided and treatments could be long-lasting and safer for the environment. Therefore, enzymatic grafting appears to be a promising methodology for the modification of chemical wood composition and properties. In this work, a grafting strategy is proposed for providing resistance against wood decay fungi to wood. For this purpose, experimental conditions of the grafting were studied regarding time of reaction, enzyme dose, substrate dose, temperature and operational mode. Kraft lignin was used as a phenolic substrate to model the grafting due to its biocidal properties and to the fact that grafting degree could be determined indirectly by means of colorimetric measurements. In addition, it represents a residue of the paper industry, so, this strategy allows also the exploitation of a waste. Time of reaction has appeared to be the main factor when the grafting is carried out in aqueous solution. However, in this study it has been proved that the best results of the grafting are achieved when the reaction occurs out of the aqueous medium. Washing with hot water of the treated wood veneers was also performed, to remove substrates not attached, and has revealed a good linkage of the lignin onto wood. Finally, preliminary durability assays with Coniophora puteana were carried out and have shown good prospective applications for this type of wood treatments.
C Fernández-Costas, S Palanti, M Ángeles Sanromán, D Moldes

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

Wood properties modification by an enzymatic assisted treatment with phenolic extractives
2016 - IRG/WP 16-30696
Extractives of sawdust and bark from P. pinaster and, condensed tannins (CTs) from P. radiata bark were used to treat beech and pine veneers in combination with an oxidative enzyme, in order to stably graft such extractives onto the veneers. First, the antifungal activity of P. pinaster phenolic extractives against wood decay fungi was studied. These extractives were also used to hydrophobize pine and beech wood by means of the treatment with laccase enzyme. The same treatment was performed with CTs from P. radiata and chemically derivatized CTs (HPTs) to modify the physiochemical properties of beech wood. Sawdust extractives of P. pinaster showed a high growth inhibition of P. ostreatus and C. puteana. Besides the biological activity, the treatment with laccase and the mentioned phenolic extractives provided stable hydrophobic properties to pine and beech wood. The chemical derivatization of CTs enhanced the hydrophobic properties of native CTs. After the inclusion of such HPTs in the enzymatic treatment of wood veneers, a higher resistance to water absorption was obtained. Thus, the stable graft of P.pinaster phenolic extractives onto wood provided biological and hydrophobic properties. The chemical derivatization of natural phenolic extractives improved their chemical and biological properties which opens a new perspective for future applications of these compounds.
D Filgueira, C Fernández-Costas, D E García, D Moldes

Investigation of enzymatic effect on pit membranes by light and scanning electron microscopy
2016 - IRG/WP 16-40721
Spruce wood, one of the refractory wood species has pit membranes, which has an influence on the permeability of wood providing liquid flow between the wood cells. However, these membranes tend to close under the fiber saturated point (FSD), which makes impregnation more difficult. In this study spruce sapwood samples were treated with two different commercial enzymes to improve the permeability of spruce sapwood. Bioprep 3000 L and Viscozyme L, which are mostly used in the textile industry, are alkaline pectinase enzymes as well as acidic pectinase enzymes, respectively. Following enzymatic treatment, wood samples were analyzed under by light microscopy (LM) and scanning electron microscopy (SEM). Primarily, all enzyme treated and untreated wood samples were stained with toluidine blue. The pectin material was coloured red with toluidine blue stain. However, enzymatic treatment caused red coloration loss along with expansion and rupturing of pit membranes. According to these results, pit membranes are known to be destroyed. As expected, the acidic pectinase enzyme degraded torus more so than the alkaline enzyme.
S Durmaz, Ü C Yildiz, M Öztürk, B Serdar

New perspectives for wood protection: enzyme-based treatments
2016 - IRG/WP 16-40742
Wood protection research is continuously looking for more benign and effective treatments. One of the main concerns deals with the toxicity of the active compounds employed in the formulations of the preservatives, since they could become a health and environmental issue. Secondly, long-lasting treatments are preferred in order to increase the service life of the treated wood. Weathering conditions are responsible of constant leaching of the formulations and most treatments tend to fail with regard to their efficacy along the time due to this phenomenon. In this paper, enzymatic treatment of the wood is proposed as an alternative to the conventional treatments. The main advantage of this novel approach is the covalent fixation of the active compounds to the wood surface. On the contrary, traditionally wood treatments are based on a simple impregnation of wood and they do not ensure a suitable retention of the formulations along the time. It is also a versatile tool which could be applied with a huge range of actives compounds. In the present work, enzymatic grafting is shown with two different active compounds: Kraft lignin and wood extracts. As enzyme, a laccase from Myceliophtora thermophila was chosen due to its ability to oxidize phenolic substrates. Then, stable anchoring of this grafting was assessed and mini-blocks of wood were treated following this procedure to test its efficacy against wood-degrading fungi. Enzymatic grafting was demonstrated to improve resistance to leaching according to the European Standard EN 84. In this way, compounds that have low biocidal activity (when compared with available commercial formulations) become highly effective because of the low lixiviation. Finally, durability assays were accomplished in order to test the real effectiveness of the enzymatic treatments against fungi. From the different treatments studies, enzymatic treatments with the extractives from Pinus spp. have appeared to have a great potential to increase wood durability, reducing the mass losses until only a 4% of the initial mass.
C Fernández-Costas, S Palanti, M Á Sanromán, D Moldes

Different levels of acetylation lead to groupwise upregulation of non-enzymatic wood degradation genes of Rhodonia placenta during initial brown-rot decay
2020 - IRG/WP 20-10958
Rhodonia placenta, often used as a model fungus to represent brown rot fungi, uses a two-stepped degradation mechanism to degrade wood. Regarding the overcoming of wood protection systems the initial degradation phase seems to be the crucial point. A new laboratory test enables the separation of the non-enzymatic oxidative and the enzymatic degradation phases, which has previously been proven challenging. In this study this new method was used to investigate gene expression of ten genes, presumably involved in non-enzymatic oxidative degradation. Therefore, R. placenta was grown on untreated and to three different levels acetylated Scots pine (Pinus sylvestris L.) samples. Gene expression was analyzed via qPCR. Results showed a groupwise upregulation of genes involved in the non-enzymatic oxidative degradation phase, according to increasing weight percentage gain (WPG). However, not all genes thought to be involved in initial brown-rot decay showed an upregulation.
M Kölle, R Ringman, A Pilgård