Brown Rot Fungus Poria Placenta Research Articles

The Impact of Paraffin-Thermal Modification of Beech Wood on Its Biological, Physical and Mechanical Properties

The European beech (Fagus sylvatica L.) wood was thermally modified in the presence of paraffin at the temperatures of 190 or 210 °C for 1, 2, 3 or 4 h. A significant increase in its resistance to the brown-rot fungus Poria placenta (by 71.4%–98.4%) and the white-rot fungus Trametes versicolor (by 50.1%–99.5%) was observed as a result of all modification modes. However, an increase in the resistance of beech wood surfaces to the mold Aspergillus niger was achieved only under more severe modification regimes taking 4 h at 190 or 210 °C. Water resistance of paraffin-thermally modified beech wood improved—soaking reduced by 30.2%–35.8% and volume swelling by 26.8%–62.9% after 336 h of exposure in water. On the contrary, its mechanical properties worsened—impact bending strength decreased by 17.8%–48.3% and Brinell hardness by 2.4%–63.9%.

MICROSCOPIC INVESTIGATIONS CONCERNING IN SITU OXALATE FORMATION BY THE BROWN-ROT FUNGUS PORIA PLACENTA

MICROSCOPIC INVESTIGATIONS CONCERNING IN SITU OXALATE FORMATION BY THE BROWN-ROT FUNGUS PORIA PLACENTA

Feasibility study of utilization of commercially available polyurethane resins to develop non-biocidal wood preservation treatments

Evaluation of commercially available polyurethane resins used up to now for coating applications to develop non-biocidal wood preservation treatments has been conducted. A simple method of vacuum impregnation of these resins into beech wood (Fagus sylvatica L.) and pine wood (Pinus sylvestris L.) samples followed by varied curing processes at ambient temperature, 103, and 200 °C has been performed. Based on the analysis of weight percent gain before and after leaching, treatment resistance to leaching, anti-swelling efficiency, wettability and decay durability measured for treated and untreated blocks after leaching with the white-rot fungus Coriolus versicolor for both wood species and the brown-rot fungi Poria placenta and Gloeophyllum trabeum for pine wood, it can be concluded that such treatment can be considered as potential valuable non-biocidal treatments.

Biological resistance of pine wood treated with nano-sized zinc oxide and zinc borate against brown-rot fungi

In this work, the biological resistance of Scots pine (Pinus sylvestris L.) wood impregnated with nano-sized zinc oxide and zinc borate against the fungi Daedalea quercina, Poria placenta and Serpula lacrymans was evaluated. It can be concluded that nano-sized zinc oxide inhibited the biological degradation of pine wood against Serpula lacrymans, while it was ineffective against the brown-rot fungus Poria placenta. Pine wood treated with nano-sized zinc borate exhibited higher biological resistance against the fungi Serpula lacrymans and Poria placenta.

Hydrogel-based boron salt formulations for wood preservation

Mixing boron with two thermoreversible hydrogels, obtained from an amphiphilic tripeptide and a carbamate derivative of glycerol, respectively, allows the formation of a supramolecular network that incorporates boron and significant amounts of water upon gelification of the solution when the temperature decreases. Hydrogels obtained from these gelators were impregnated in pine sapwood blocks using vacuum pressure treatment and subjected to leaching. Results indicated that incorporation of boron salts in the hydrogel network effectively protected the wood from degradation caused by the brown rot fungus Poria placenta and from attack by termites also even after leaching. It is believed that these hydrogels fill the tracheid cell walls and lumens, limiting the leachability of boron salts when the wood is humidified.

Chaetochromones A and B, Two New Polyketides from the Fungus Chaetomium indicum (CBS.860.68)

Chaetochromones A (1) and B (2), two novel polyketides, were isolated from the crude extract of fungus Chaetomium indicum (CBS.860.68) together with three known analogues PI-3(3), PI-4 (4) and SB236050 (5). The structures of these compounds were determined by HRESI-MS and NMR experiments. Chaetochromones A (1) and B (2) are a member of the polyketides family, which might originate from a similar biogenetic pathway as the known compounds PI-3 (3), PI-4 (4) and SB236050 (5). The biological activities of these secondary metabolites were evaluated against eight plant pathogens, including Alternaria alternata, Ilyonectria radicicola, Trichoderma viride pers, Aspergillus niger, Fusarium verticillioide, Irpex lacteus (Fr.), Poria placenta (Fr.) Cooke and Coriolus versicolor (L.) Quél. Compound 1 displayed moderate inhibitory rate (>60%) against the brown rot fungus Poria placenta (Fr.) Cooke, which causes significant wood decay. In addition, the cytotoxic activities against three cancer cell lines A549, MDA-MB-231, PANC-1 were also tested, without any inhibitory activities being detected.

Selected Wood Properties of Prunus Africana (Hook) Grown in Kenya as Possible Reasons for its High Natural Durability

Studies were carried out on the influence of Prunus africana heartwood extractives on the growth of selected wood decay fungi. Also, wood chemical and mineral content, dimensional stability and anatomical features of P. africana were studied. Heartwood extractives were tested in 100 ppm and 500 ppm concentrations on white, brown rot, and blue stain fungi and growth inhibition was determined as a factor of time. Dimensional stability was determined by computing the swelling coefficient after the blocks were saturated with moisture. Klason lignin, Kurschner cellulose, extractive and ash contents were determined by standard procedures. Infrared analyses were performed using Perkin Elmer FTIR spectrometer. Microscopic examination was peiformed using an environmental scanning electron microscope. The results showed that the wood is dimensionally stable, and contains 12.7 % extractives, 37.6 % cellulose and 30.4 % lignin. Extractives deposited in vessels are highly soluble in dichloromethane and mainly composed of terpenes. Extractives were able to inhibit the growth of white rot fungi Coriolus versicolor, brown rot fungi Poria placenta and blue stain fungi Aureobasidium pullulans at different concentrations tested and could explain the high durability of Prunus africana wood species.

Hydrogels obtained from an original catanionic system for efficient formulation of boron wood-preservatives

A new catanionic system associating amphiphilic carnosine (βAlaHisC8) and lauric acid forms supramolecular hydrogel at a very low concentration. This gel was investigated and we checked the validity of the concept of hydrogel utilization to reduce boron leachability and to develop new wood protection treatments. Impregnation with 5% aqueous borax solution (w/w) and 0.3% gelator agent (w/w) fosters improvement in the resistance of Scots pine sapwood subjected to water leaching toward the brown-rot fungus Poria placenta, while samples treated with 5% aqueous borax solution were partially degraded by the fungus. These results clearly indicate the effectiveness of hydrogel to retain boron in wood.

Effect of heat treatment intensity on wood chemical composition and decay durability of Pinus patula

Heat treatment is an effective method to improve biological resistance of low natural durability wood species. The aim of this study was to enhance the decay resistance of Pinus patula, an African low natural durability softwood species, via wood thermal modification technique. Heat treatment was performed on wood specimens under inert conditions at different heat treatment intensities to reach mass losses of 5, 10 and 15%. Heat treated specimens were exposed to fungal decay using the brown rot fungus Poria placenta. The wood chemical and elemental composition was determined as well as extractives toxicity before and after wood thermal modification to understand the reasons of durability improvement. The treated specimens exhibited a significant increase in their durability against wood decay in line with the severity of the treatment. Wood holocellulose was found to be distinctly more sensitive to the heating process than the lignin constituent. In addition, obvious correlations were observed between weight losses recorded after fungal exposure and both holocellulose decrease and lignin ratio increase. The same correlations were observed with the elemental composition changes allowing using the observed differences for predicting of wood durability conferred by heat treatment. Furthermore, no significant differences were observed between the toxicity of Pinus patula wood extractives before and after its thermal modification.

Use of wood elemental composition to predict heat treatment intensity and decay resistance of different softwood and hardwood species

Heat treatment is an attractive alternative to improve decay resistance of low natural durability wood species. Decay resistance is strongly correlated to thermal degradations of wood cell wall components. Some recent studies proposed the use of wood elemental composition as a valuable marker to predict final properties of the material. These results, initially obtained with pine, have been extended to different softwood and hardwood species to check validity of the method using equipment specially designed to measure mass losses during thermal treatment. Heat treatment was performed on two softwood species (pine and silver fir) and three hardwood species (poplar, beech and ash) at 230 °C under nitrogen for different times to reach mass losses of 5, 10 and 15%. Heat-treated specimens were exposed to fungal decay using the brown rot fungus Poria placenta and the weight losses due to fungal degradation determined as well as initial wood elemental composition. Correlations between weight losses recorded after fungal exposure and elemental composition indicated that carbon content and O/C ratio can be used to predict wood durability conferred by heat treatment. Moreover, it was observed that for given curing conditions thermo-degradation patterns differed considerably according to the wood species. The sole analysis of wood physical properties like its density, thermal conductivity and diffusivity cannot allow explaining the observed differences, which should also depend on thermally activated chemical processes depending on wood chemical composition.

Effects of polyvinyl alcohol on leachability and efficacy of boron wood preservatives against fungal decay and termite attack

In this study, the use of polyvinyl alcohol (PVA) as boron fixative agent was investigated. Two levels of PVA (2.5 and 4%) were evaluated with disodium octaborate tetrahydrate (DOT) at three concentrations (1, 2 and 4% boric acid equivalent (BAE)) using a double vacuum impregnation process on Scots pine sapwood specimens. Leaching was performed according to a laboratory leaching procedure. Boron analysis using atomic absorption spectrometer showed a significant reduction in boron leachability for the samples treated with both concentrations of PVA when compared to the stand-alone boron treatment leading to boron retentions capable of preventing wood biological degradations. Decay resistance of the leached specimens was evaluated using the brown rot fungus Poria placenta. Even if complete protection was not fully achieved, an improvement in decay resistance was observed for the samples treated with DOT in presence of PVA. This leak of efficacy was attributed to a decrease in the biological activity of the complexed boron against fungi. Durability of treated wood against termite attack, evaluated using Reticulitermes santonensis, indicated a significant enhancement for the samples treated in presence of the fixative agent compared to the pure boron treatment.

Effects of monoglycerides on leachability and efficacy of boron wood preservatives against decay and termites

Borates are well known for their ability to protect wood against fungal and insects attacks. However, their use in outdoor applications is limited due to their high leachability from treated wood. In this study, monoglycerides were investigated as fixative agents to reduce boron depletion from Scots pine using a double vacuum impregnation process involving impregnation with disodium octaborate tetrahydrate (DOT) followed by a second impregnation with the fixative agent. Significant reduction in boron leachability in samples treated with monoglycerides was observed compared to the standalone boron treated specimens. Evaluation of decay resistance of treated blocks using the brown rot fungus Poria placenta indicated a slight increase of durability, while resistance to termites attacks was strongly improved as demonstrated by the low weight losses and the high termites mortality levels observed. Monoglycerides could therefore be valuable additives to reduce boron depletion for outdoor applications in which wood is exposed to natural leaching conditions.

Prediction of the decay resistance of heat treated wood on the basis of its elemental composition

The effect of heat treatment temperature on the elemental composition of Scots pine sapwood ( Pinus sylvestris) has been investigated in the range of temperatures between 220 and 250 °C. The results revealed an important increase of carbon content, while oxygen content significantly decreases. Independently of the heat treatment temperature, elemental composition is strongly correlated with the mass losses due to thermal degradations. Carbon content as well as O/C ratio seem to represent valuable markers to estimate wood degradation after heat treatment. Heat treated specimens were exposed to fungal decay using the brown rot fungus Poria placenta and the weight losses due to fungal degradation were determined. Correlations between weight losses recorded after fungal exposure and elemental composition indicated that carbon content or O/C ratio can be used to predict wood durability conferred by heat treatment allowing us to envisage the development of a proper method to evaluate the quality of heat treated wood and predict its durability. These results also confirm that chemical modifications of wood cell wall polymers are the main factors responsible for wood durability improvement against fungal decay after heat treatment.

Non-destructive prediction of decay resistance of pinus sylvestris heartwood by near infrared spectroscopy

Restrictions on the use of wood preservatives have increased interest in the utilization of the natural durability of wood. In Scandinavia Scots pine (Pinus sylvestris L.) is an important commercial tree species. Its heartwood has traditionally been used in constructions exposed to risk of decay. In a laboratory experiment Scots pine wood specimens sampled from inner heartwood, outer heartwood and sapwood were exposed to the brown rot fungus Poria placenta. Outer heartwood was found to be more resistant than inner heartwood and sapwood. Near infrared spectroscopy (NIR) spectra obtained on solid wood before decay testing were used in multivariate calibrations to predict decay resistance of heartwood. Results from multiple test set validated partial least squares regression models showed that resistance to decay in Scots pine heartwood could be predicted with satisfying precision using NIR spectroscopy. As NIR spectra were collected on solid wood, development of the method for industrial use is potentially possible.

The effect of oxidative pretreatment on cellulose degradation by Poria placenta and Trichoderma reesei cellulases

The possible role of hydrogen peroxide in brown-rot decay was investigated by studying the effects of pretreatment of spruce wood and microcrystalline Avicel cellulose with H2O2 and Fe2+ (Fenton's reagent) on the subsequent enzymatic hydrolysis of the substrates. A crude endoglucanase preparation from the brown-rot fungus Poria placenta, a purified endoglucanase from Trichoderma reesei and a commercial Trichoderma cellulase were used as enzymes. Avicel cellulose and spruce dust were depolymerized in the H2O2/Fe2+ treatment. Mainly hemicelluloses were lost in the treatment of spruce dust. The effect of the pretreatment on subsequent enzymatic hydrolysis was found to depend on the nature of the substrate and the enzyme preparation used. Pretreatment with H2O2/Fe2+ clearly increased the amount of enzymatic hydrolysis of spruce dust with both the endoglucanases and the commercial cellulase. In all cases the amount of hydrolysis was increased about threefold. The hydrolysis of Avicel with the endoglucanases was also enhanced, whereas the hydrolysis with the commercial cellulase was decreased.

Effect of carbon source on the production of oxalic acid and hydrogen peroxide by brown-rot fungus Poria placenta

Oxalic acid and hydrogen peroxide have been suggested to be essential in the degradation of wood carbohydrates by brown-rot fungi. The production of oxalic acid, hydrogen peroxide and endo-β-1,4-glucanase activity by the brown-rot fungus Poria placenta was studied on crystalline cellulose, amorphous cellulose and glucose media. Oxalic acid and hydrogen peroxide by P. placenta were clearly produced on culture media containing either crystalline or amorphous cellulose. Oxalic acid and hydrogen peroxide were formed simultaneously and highest amounts of oxalic acid (1.0 g l −1) and hydrogen peroxide (39.5 μM) were obtained on amorphous cellulose after 3 weeks cultivation. On glucose medium the amounts were low. The endoglucanase activity was observed to increase during the cultivation and was most pronounced on glucose medium and thus indicated the constitutive characteristics of the brown-rot cellulases.

Immunological characterization of lignocellulose degradation

Polyclonal antibodies produced to the brown-rot fungus Poria placenta have been used with fluorescence microscopy to detect fungal hyphae colonizing wood. In addition, an enzyme-linked immunosorbent assay (ELISA) has been used to detect and quantify the extent of fungal decay in wood. ELISA values correlated with percent weight loss associated with fungal degradation and the assay was able to detect fungal colonization ten days after inoculation in solid wood. Monoclonal antibodies to extracellular metabolites of P. placenta have been produced and are being characterized. Monoclonal antibodies have also been produced to native and partially deglycosylated Mn2 peroxidase. The use of immunological probes to monitor and characterize the decay process is discussed.

Wood decay by basidiomycetes: Extracellular tripartite membranous structures

Decay of pine-wood by the brown-rot fungi Poria placenta, Fomitopsis pinicola, Serpula lacrimans, Paxillus panuoides and the white-rot fungi Trametes versicolor, Trametes hirsuta, Sporotrichum pulverulentum was investigated with the transmission electron microscope. Material stained with ruthenium red showed extracellular, tripartite structures associated with all fungi throughout all stages of wood decay. These structures surrounded the intensely stained fungal cell wall, were partly embedded in an extracellular slime and were contiguous with the wood cell wall. Besides brown-rot fungi with filter paper activity S. pulverulentum showed similar tripartite structures, however these were branched and extended from the fungal cell wall into the lumen of the wood cell. The origin, formation and function of these extracellular structures are discussed.

Osmiophilic particles as a typical aspect of brown and white rot systems in transmission electron microscope studies

Transmission electron microscope investigations of wood decay by the brown rot fungi Poria placenta and Serpula lacrimans and the white rot fungi Trametes versicolor and Sporotrichum pulverulentum showed that the distribution of the osmiophilic particles in brown-rotted and white-rotted wood conformed to that previously established for other species. When pinewood is degraded by brown rot fungi osmiophilic particles are densely distributed in all cell wall layers. This distribution correlates with the rapid depolymerisation of carbohydrates over the entire cell wall. In white-rotted pinewood osmiophilic particles are found on the surfaces of the cell wall and of cell wall remnants but never within the cell walls. That osmiophilic particles within and around hyphae outside degraded woodblocks and even in and on hyphae 40 mm from the wood suggests that they are not degradation products of a wood component but are produced by the fungus. However their aggregation in regions of strong wood decay suggests that they are associated with this process. Contrary to the literature brown rot fungi have been found capable of lignin metabolism causing complete disintegration of wood cell walls, middle lamella and the cell corners.