Volume 53, Issue 2

A literature survey was performed to find progress in techniques for monitoring penetration of synthetic resins in wood cell walls. Electron energy loss spectroscopy (EELS) in combination with transmission electron microscopy (TEM) was successfully applied for the high resolution examination of the distribution of a partly methylated hydroxymethyl melamine resin in Norway spruce ( Picea abies Karst.) earlywood cell walls. The nitrogen of the resin was found as clearly detectable signals in all layers of the lignified cell wall, thus allowing the quantification of resin which had penetrated into the different layers. Possible principles of decay protection of wood which has been upgraded with low concentrated aqueous solutions of modified hydroxymethyl melamine resins with medium to low hydroxymethyl/melamine ratios are discussed.

We investigated the ability of selected buffers to extract proteins and other materials from the surfaces and subsurfaces of ponderosa pine wafers colonized by selected wood stain fungi and potential bioprotectant bacteria. The effects of extraction conditions on enzyme activity were also analyzed. The addition of Tween 80 to the extraction media markedly enhanced total protein recovery as well as enzyme activity. Increasing the extraction time from 6 to 12 hours failed to increase total protein recovery, indicating that either most of the protein was removed earlier or proteases in the wood had attacked proteins liberated during extraction. Relatively short extractions using sodium acetate buffer amended with Tween 80, therefore, produced the best protein recovery and enzyme activity. These conditions can be used for extracting wood colonized by various combinations of stain fungi and bacterial bioprotectants to study the effects of the interaction on physiologic activities of the target fungi.

Isolates of the dry rot fungus, Serpula lacrymans , and of the morphologically similar wild merulius, S. himantioides , were investigated by amplified ribosomal DNA restriction analysis (ARDRA) of the internal transcribed spacer (ITS) region to prove this method as diagnosis tool for the economically important indoor rot fungi. The technique uses the polymerase chain reaction (PCR) to amplify the relatively variable sequences of the ITS region arranged between the highly conserved portions of the 18S and 28S RNA genes of the nuclear ribosomal DNA (rDNA) repeat unit. Subsequent digestion of the amplicon with restriction endonucleases may exhibit differences at species and subspecies level. Using the universal ITS 1/ITS 4 primer combination, the ITS region of all isolates of S. lacrymans and S. himantioides was amplified. The size of the amplified products was about 630bp in both species, as estimated from agarose gel electrophoresis. Digestion of the amplicon with the endonuclease pairs Alu I/ Hha I and Ava II/ Mbo II, respectively, revealed identical rDNA-ITS fragments for the isolates of both species, indicating their genetic relationship. On the other hand, digestion with Bgl I/ Hinf I and Hae III/ Taq I, respectively, separated the fungi by means of different fragment patterns. Thus, ARDRA-ITS proved to be suited for the identification of both fungi.

Novel microcosms were used to test separately the effects of aeration and humidity on the decay capacity, linear spread and survival of the dry rot fungus Serpula lacrymans . The application of a pumped air supply resulted in cessation of fungal activity in the microcosms at all but the lowest air flow rate. At this lowest rate marked growth tropisms were sometimes seen and linear growth of the fungus away from the air supply was accentuated. In both air flow and humidity experiments the loss of growth and decay capabilities was not always accompanied by a loss of viability. Larger scale growth chambers incorporating simulated flooring and plaster walling were developed in sealed aquarium tanks using both new and old building materials. Differences in growth rates and morphology of S. lacrymans were noted, with old materials generally being more favorable to the growth of the organism. Opening the growth chambers and applying a controlled air flow rapidly halted the spread of S. lacrymans resulting in the fungal mycelium shrivelling, discolouring and becoming susceptible to attack by moulds. Loss of viability of S. lacrymans in re-sealed chambers depended crucially on the instigation of a water-deprivation schedule. The results may have serious implications for the use of purely environmental strategies for the remedial treatment of outbreaks of the dry rot fungus in buildings.

One of the color substances, taiwanin A, was isolated from Taiwania ( Taiwania cryptomerioides Hayata) heartwood. According to the 13 C-NMR, 1 H-NMR, HSQC, HMBC, and NOE difference spectroscopy analyses, the diene structure of taiwanin A was reconfirmed to be the trans-trans formulation. In addition, it was proven that deep orange crystalline taiwanin A changed to white and pale yellow compounds, taiwanin C and taiwanin E, after light irradiation. The conversion mechanism of taiwanin A into taiwanin C and taiwanin E is also proposed and discussed in this study.

Natural wax-like materials were extracted from leaves and bark of Aleppo pine ( Pinus halepensis Mill.) by using toluene as organic solvent. Experimental water repellent formulations (WRFs) were prepared using 10% gum rosin as the resin constituent and 0%, 1% and 2% paraffin wax, pine needle/bark extracts or mixtures of paraffin wax and needle/bark extracts in proportion 1 : 1 as hydrophobic substance. All experimental WRFs applied to small, cross-sectional wood specimens of Scots pine ( Pinus sylvestris L.) and beech ( Fagus sylvatica L.). Wood specimens were impregnated by a simple immersion technique and the water repellent effectiveness (WRE) was assessed by using tangential swelling data. Toluene soluble extracts from needles and bark applied to wood provided hydrophobic properties to pine and beech wood specimens but to a lesser degree when compared to paraffin wax. Bark extracts appeared to be stronger hydrophobic materials than needle extracts. Both needle and bark extracts can be successful substitutes for paraffin wax in WRFs up to 50 %. The degree of protection provided by WRFs and the differences between treatments were smaller in pine heartwood and beech sapwood than in pine sapwood.

The deposition process of lignins within differentiating xylem walls of normal and compression wood of Buxus microphylla var. insularis Nakai was examined by visible-light microspectrophotometry coupled with the Wiesner and Mäule reactions. Buxus formed compression wood on the underside of the leaning stems. The secondary walls of the vessels and fibre tracheids in compression wood showed an intense lignification in the outer region of S 2 layer. The spectra of tissues after Mäule and Wiesner reactions showed absorption maxima of around 515 nm and 570 nm, respectively. In differentiating xylem cells of normal wood, lignin composed of both guaiacyl and syringyl units was deposited mainly during the S 2 thickening and after formation of the S 3 layer in fibre tracheids, whereas in vessels it was actively deposited mainly during the S 2 thickening. In compression wood, the deposition of the lignin composed of guaiacyl units was observed for a long period from the early stages of the S 2 thickening. Lignification was becoming particularly active at the outer portion of S 2 layer after completion of the S2 thickening in both vessels and fibre tracheids. On the other hand, the syringyl units were deposited mainly during the S 2 thickening in both cell types.

Manganese peroxidase preparations (MnP) from the white-rot fungus Nematoloma frowardii were able to release 14 CO 2 directly from 14 C-labeled milled wheat straw (MWS; total lignin fraction) and milled straw lignin (MSL; dioxane soluble part of MWS). Apart from the formation of 14 CO 2 (4–10 %) the treatment of insoluble MWS and MSL with MnP resulted in the formation of water-soluble 14 C-lignin fragments (lignin solubilization, 14–25%). Analyses with gel permeation chromatography (GPC) demonstrated the formation of lignin fragments with predominant molecular masses around 1 kDa. The extent of MWS mineralization and solubilization was enhanced in the presence of reduced glutathione (GSH) acting as thiol mediator, whereas MSL mineralization was not stimulated by GSH. The principle of direct extracellular mineralization of lignin catalyzed by the MnP system may make a significant contribution to the formation of carbon dioxide in lignincellulose containing habitats.

Quercus suber L. milled cork lignins obtained from extractive-free cork (MCL) and from saponified cork (MCL sap ) were characterized by thioacidolysis and KMnO 4 oxidation. These techniques and the previously used analytical pyrolysis revealed that cork contains a guaiacyl lignin (G lignin) with 94–96% guaiacyl-, ca. 3% syringyl-, and 2–3% of 4-hydroxyphenyl-propane units. The total yields of degradation products in thioacidolysis and KMnO 4 oxidation experiments were lower in comparison to those of a spruce milled wood lignin (MWL spruce ) suggesting a higher cross-linking in the G-lignin of cork. The higher frequency of “condensed” structures (having C-C or C-O-C linkages to aromatic rings) in cork lignin was also manifested in the relative abundance of various aromatic acids obtained by KMnO 4 oxidation. The cork lignin (MCL sap ) contains only low amounts (ca. 2%) of covalently bonded suberinic acids. Numerous free aliphatic suberinic acids were detected and identified in the ether soluble part of MCL sap . Ferulic acid was not liberated by thioacidolysis, pointing at an in situ acylation. We suggest that the major part of the aromatic domain in cork is a G-lignin but that it includes also another structural moiety with higher H-unit content and linked by thioacidolysis resistant bonds.

Matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was used to investigate the reaction products obtained by treatment of phenolic substances with the laccase-mediator system, consisting of the enzyme laccase and a low-molecular-weight substance, the so-called mediator. Two mediators, 2,2′-azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid diammonium salt (ABTS) and 1-hydroxybenzotriazole (HOBT), were employed. Polymerizing and depolymerizing properties of the LMS were investigated and assigned to specific components of the system, i. e. , laccase and mediator. The polymerizing action of laccase and the ABTS cation radical on phenols was demonstrated in addition to the depolymerizing effect of the LMS. The LMS causes polymerization of phenolic substrates in the initial phase of the reaction, but then degrades the initially formed polymers. The extensive breakdown of this oligomeric and polymeric material occurs exclusively in the presence of both components, mediator and laccase. Furthermore, it is also dependent on the type of polymer formed.

A chemiluminescence assay was used to measure the production of hydroxyl radicals (·OH) in aqueous solutions of hydrogen peroxide and iron-containing catalysts. Preliminary experiments evaluating assay sensitivity revealed that one of the required reagents, phthalhydrazide (PtH), interfered with the studied reactions. In addition, undesirable degradation of the chemiluminescent form of PtH was observed. By removing PtH from reaction solutions and modifying the published procedures, a successful non-intrusive method for measurement of ·OH was obtained. The modified assay was used to compare the rate of ·OH generation in solutions of H 2 O 2 , either FeSO 4 or Fe-EDTA and a substrate, lignosulfonate. This “biomimetic” pulp bleaching system is meant to simulate naturally occurring biological reactions utilized for degradation of lignins by wood-degrading fungi. Results from these experiments show that FeSO 4 produced more ·OH than Fe-EDTA. The improved non-intrusive chemiluminescence assay has proven to be an excellent tool for investigating the role of the ·OH in biomimetic pulp bleaching and potentially other systems.

The aim of this study was to investigate the surface composition and morphology of Chemithermomechanical pulp (CTMP) fibers from spruce. The fibers were exposed to a sequence of mild treatments such as washing, peroxide bleaching and extraction. The effects of treatments on fiber bulk composition and surface properties were investigated. All treatments did not significantly result in changes in total lignin and carbohydrate content. However, the extractives were stepwise removed. With the Electron Spectroscopy for Chemical Analysis (ESCA) technique, a gradual reduction of unoxidized carbon in the C1s resolved peak was shown, which was correlated to the removal of non-carbohydrates. Variations in surface topography among the analyzed samples were displayed with Atomic Force Microscopy (AFM) imaging of fibers in tapping mode. The wetting properties of all pulps were measured by Dynamic Contact Angle (DCA) on the single fibers. The advancing contact angle decreased and the hysteresis is also reduced, as a result of treatments. ESCA, AFM and contact angle analyses suggest that the extractives are distributed as globular particles at the fiber surface. Phase imaging AFM indicated the presence of lignin as irregular patches at the surface. A model of the CTMP fiber surface based on experimental findings in this work is proposed.

To assess the likely effects of silvicultural treatment on the wood quality of Nothofagus nervosa grown in the UK, and the possibilities of independent selection within seed origins for density and growth rate, ring width and wood density were analysed from pith to bark of 19 trees. Variations in vessel lumen size, vessel number mm −2 , and total lumen area mm −2 were analysed in ten trees. Since density increased by only 0.005g cm −3 per mm increase in ring width, silvicultural practices such as initial spacing and thinning are not likely to have a substantial effect on the wood density of rauli. Similarly, variation in density with cambial age was significant but relatively minor in the 40- and 60-year old trees of the present sample, suggesting that the rotation length is unlikely to have any practical influence on the density of rauli. Considerable between-tree differences in density were found which did not correspond to differences in ring width, suggesting it should be feasible to select independently for density and growth rate. These differences in density were associated with differences in both vessel lumen size and vessel number mm −2

The relationship between heat and mass transfer at wooden surface is investigated experimentally by drying 1.6 mm thick birch veneers in constant conditions in a laboratory-scale roller dryer. By intermediate weighing of the samples a drying curve is established for each specimen. The drying curves are formulated in a functional form to produce the drying rate as a function of wood moisture content. Based on that and the measured heat-transfer coefficient a correction factor is calculated for the mass transfer coefficient predicted by the boundary layer theory. The results show that the convective mass transfer coefficient for wooden surfaces substantially deviates from that given by the analogy between heat and mass transfer. The correction factor describing the internal resistance for evaporation is strongly dependent on wood temperature within the range 50–90°C, but for practical purposes not dependent on the average moisture content of the veneer (range 40–70%). The numerical value of the correction coefficient established is somewhat lower than published earlier by other researchers.

The relationship between the tangential Young's modulus and the transverse cell shape in coniferous early wood was investigated by using cell models constructed by power spectrum analysis. The calculated Young's moduli of the cell models explained qualitatively the change of the experimental Young's moduli with density as well as the difference in the experimental values among species. The calculated Young's moduli differed significantly among species depending on the cell model shapes when compared at the same density. With increasing element angle in the model, the Young's modulus greatly increased without a significant change in the density, especially at the larger ratios of the axial length of the tangential cell wall to that of the radial cell wall.

The objective of this study was to determine the effect of five different silvicultural strategies and wood type on mechanical and physical properties of loblolly pine ( Pinus taeda L.) particleboard and fiberboard. The furnish was prepared in an unconventional manner from innerwood and outerwood veneer for each stand. Modulus of rupture (MOR) differences between the stands were insignificant for particleboard. Some significant modulus of elastisity (MOE) differences existed between the stands for particleboard and fiberboard. Differences between the wood types were minimal for each stand. Innerwood yielded higher mean MOR, MOE, and internal bond (IB) values than outerwood for most of the stands. The differences between the stand and wood types for 2 and 24 h thickness swell and 2 and 24h water adsorption were very minimal. This research has shown that innerwood can produce particleboard and fiberboard panels with very comparable mechanical and physical properties to outerwood. The effect of the silvicultural strategy (i. e., stand) was minimal for most properties.