Volume 54, Issue 5

Scots pine ( Pinus silvestris ) and Norway spruce (Picea abies) were dried in a laboratory kiln, using conventional schedules with temperatures up to 60°C as well as schedules reaching 110°C. The losses of terpenes, which completely dominate the fugitive emissions from kiln drying of softwoods, were estimated by extraction of pooled subsamples from each batch, before and after drying. The original contents of terpenes were found to be in the ranges of 0.4–0.5% in pine sapwood, 0.8–1.1% in pine heartwood, and 0.02–0.08% in spruce, all calculated relative to the dry weight of the wood. The emissions from pine corresponded to 25–50% of the original content and those from spruce to 10–50%. High temperature drying in the laboratory was accompanied by larger losses, but this tendency was not found in the full-scale drying of spruce. No consistent difference was found between timber from the north of Sweden and from the south. Sampling of the vent exhaust fumes did not give results of sufficient reliability to confirm the extraction analyses.

Antitermitic activities of catechin-metal complexes were investigated for further utilization of catechin as a termite control agent. Catechin (CA), heavy metal salts (NiCl 2 , CuCl 2 , ZnCl 2 ) and CA/metal mixtures with Ni(II), Cu(II) and Zn(II) were subjected to bioassays using a subterranean termite, Coptotermes formosanus Shiraki. The astringent properties of each system were assessed by measuring the weight of precipitate with bovine serum albumin (BSA). Changes in UV spectra of the CA/metal mixtures were also measured. CA caused less than 30% mortality after the 21-day test period, and had no BSA-precipitating capacity. The effects of heavy metals on CA activities varied with metal. CA/Ni(II) showed the highest termiticidal activity among tested materials, but exhibited no BSA-precipitating capacity and little change in UV spectrum. On the other hand, both CA/Cu(II) and CA/Zn(II) increased the BSA-precipitating capacity and UV absorption with time after preparing the CA/metal solutions, but their termiticidal activity was almost equal to CA. Termiticidal activity of CA was improved by the addition of Ni(II) but hardly changed by Cu(II) or Zn(II), while astringent properties of CA were hardly changed by addition of Ni(II) but improved by Cu(II) or Zn(II). Termiticidal activity was negatively correlated with astringent property.

Wood degradation, one-electron oxidation activity as assayed by ethylene production from 2-keto-4-thiomethylbutyric acid, and phenol oxidase activity were measured in cultures of six deuteromycete fungi, with glucose or wood as the carbon source. The four fungi that degraded Japanese beech wood had higher one-electron oxidation activities in wood-containing cultures than in glucose-containing cultures. These four fungi also had measurable phenol oxidase activity in wood-containing cultures, but not in glucose-containing cultures. The two mould fungi that did not significantly degrade wood had no phenol oxidase activity in either wood- or glucose-containing cultures. The one-electron oxidation activity in intact cultures of the soft-rot deuteromycetes was roughly related with the rate of weight loss during wood degradation in those cultures. However, there was no clear relationship between phenol oxidase activity and either one-electron oxidation activity or the rate of wood weight loss, either over time, or in total. Most of the one-electron oxidation activity resulted from phenol oxidase and hydroxyl radical. Most of the phenol oxidase activity resulted from laccase.

Field emission scanning electron microscopy and energy-dispersive X-ray microanalysis were used to investigate the generation of growth stress in connection with the deposition of cell wall materials along the innermost surface of radial walls during secondary wall formation of differentiating tracheids of Cryptomeria japonica . Samples were collected when the turgor pressure of the tree was low (16:00 h), and when the pressure was high (6:00 h). In samples collected at 16:00 h, cellulose microfibrils deposited on the innermost surface of radial walls were clearly evident and amorphous material was rarely found. Conversely, in samples collected at 6:00 h, cellulose microfibrils were rarely observed and the amorphous material was prevalent. Cellulose microfibrils were evident, however, after removing the amorphous material with chlorite. The concentration of potassium on the inner surface of radial walls was greater at 6:00 h than at 16:00 h. After chlorite treatment, the concentration of potassium measured in the samples collected at 6:00 h decreased to a level equivalent to that in samples collected at 16:00 h and thus potassium was found to be associated with the amorphous material on the cellulose microfibrils. The amorphous material is probably a matrix of hemicellulose and monolignol, material that is abundant on the inner surface of developing cell walls, especially during expansion (as a result of high turgor pressure) of differentiating tracheids. A matrix of hemicellulose and lignin deposited in the expanded gaps between cellulose microfibrils and daily expansion of the gaps probably produces an isotropic compressive stress (growth stress). This paper demonstrates periodicity in cell wall formation as a result of the cycles of compressive growth in the differentiating cell wall.

The dimensional stabilisation imparted to Maritime pine sapwood by chemical modification with hydrophobic organosilicon compounds was investigated. Modification was performed via esterification, using different chemically synthesised models bearing trimethylsilyl groups: 3-trimethylsilylpropanoic anhydride (I), 2-trimethylsilylmethylglutaric anhydride (II) and trimethylsilylethenone (III). Grafting was confirmed by infrared spectroscopy as well as 13 C and 29 Si NMR CP MAS analysis and was located into the wood cell walls. The dimensional stabilisation induced by I and II appeared to be stable during three oven-dry/water-soak cycles and, for a given number of hydroxyl blocked, to be superior to that imparted by acetylation. The graft from III, however, was found to hydrolyse progressively into an acetyl group via a metallotropic rearrangement. Further investigation on the hygroscopicity and swelling behaviour of modified wood from I and II indicated that dimensional stabilisation was attributable to a bulking effect rather than a change in substrate hygroscopicity. The bulky grafts from I and II were, in particular, thought to locally over-swell the wood cell wall, revealing regions with new water-accessible hydroxyl groups.

The paper describes an experiment to evaluate the effect of subtle changes to the amino acid composition of the growth medium on the production of volatile organic compounds (VOCs) by a Trichoderma aureoviride isolate and the consequent inhibition of wood decay fungi. A synthetic medium was produced to represent the C:N ratio and major amino acid content of Scots pine sapwood. Changes in the amino acid content of the medium produced very significant differences in the VOC output produced by the Trichoderma isolate and in the levels of inhibition of the target wood decay fungi. Principal component analysis of the VOC profiles indicated that aldehyde and ketone components were associated with the greatest inhibition of the target fungi. The implications of the results for the use of Trichoderma isolates as biological control agents of decay fungi in wood are discussed.

Standing bamboo culms have an attractive greenish skin. Once harvested, however, they turn yellow and the color starts to decay. These adverse properties limit their applications and degrade their performance. Chromated copper arsenate (CCA) based preservatives have been reported to be good protectors for preserving the green color of bamboo culms. An alkali pretreatment was required before applying CCA. However, the mechanism of alkali pretreatment on color conservation is not fully understood. In this study, morphology, wettability, chemical and pigment changes of moso bamboo ( Phyllostachys pubescens Mazel) were studied after treating with four alkali reagents. The results showed that 2% KOH effectively removed the waxes and capes of silica cells on moso bamboo surface and also increased the surface wettability much better than treatments with 4% K 2 CO 3 , 10% K 2 CO 3 , 4% Na 2 CO 3 , or 4% NaHCO 3 . The KOH pretreatment also results in a better penetration and reaction with the green color protector (5% Boliden K-33, type-B CCA), and subsequently preserved the green color appearance of moso bamboo.

Ten hemicellulosic preparations, obtained by treatments of the water-extracted maize stems with peroxymonosulfuric acid, peroxyformic acid, peracetic acid, and 2% hydrogen peroxide under the conditions given, respectively, were investigated by gel permeation chromatography and spectroscopic techniques such as Fourier transform infrared and carbon-13 nuclear magnetic resonance. Under an optimum extracting condition (2% H 2 O 2 , 45°C, 12 h, pH 11.5–12.0), the hemicelluloses obtained represented 63.3–64.7 % of the original hemicelluloses and had high weight-average molar mass between 69060 and 54740 g mol −1 . The most obvious feature was found that the alkaline peroxide treatment of the stems under the conditions used did not affect the overall structure of the hemicelluloses. The thermal stability of the hemicelluloses was found to increase slightly with increasing molar mass. All the hemicellulosic preparations were, however, to varying degree thermally unstable at temperature above 180°C.

Cellulases isolated from Trichoderma reesei and Phanerochaete chrysosporium were screened for hemicellulolytic, pectinolytic and cellulolytic activity using locust bean mannan, birchwood xylan, citrus fruit pectin and carboxymethylated cellulose (CMC) as substrates. The purpose of this work was to choose appropriate enzymes to include in a “miniature cellulase system” with minimal hemicellulase activity for the preparation of lignin-carbohydrate complexes (LCCs). The endoglucanases showed CMC activity whereas activity towards the substrate was not detected for the CBHs. Xylanase activity was observed for EG I and EG 38 whereas mannanase activity was observed for EG 44. None of the enzymes degraded pectin. The results suggest that CBH I, CBH II, CBH 58, EG II and EG III are good candidates for the effective preparation of LCCs. The possible biological function for the hemicellulolytic activity of cellulases is discussed.

On the basis of the proton NMR relaxation time dependencies on temperature and frequency in cellulose pulp a simple two-motion model of molecular dynamics has been proposed. The parameters, activation energies and correlation times, describing the model may be correlated with structure features such as level of crystallinity of cellulose with different origin , as well as degree of paper devastation.

Determining the structure of the plant polymer lignin is not feasible because of the heterogeneous structure of this polymer and the difficulties encountered in its extraction. Therefore, computational chemistry can provide information, which may otherwise be unavailable. Based on experimental results, computational chemistry was used to mimic the processes involved in lignin formation. Synthetic polymers also were prepared from the three major lignin precursors and their physical properties were shown to give good correlation with computational models constructed to represent these polymers. Both computational and experimental results, demonstrated that the higher the degree of methoxylation, the more flexible the polymer and this was shown to be dependent on the type of inter-unit linkage. Using the same experimentally derived parameters, a model was constructed to represent a generalised lignin. This model was shown to be a flexible, closely packed structure and this was attributed to the predominance of 8-O-4 linkages, which allowed closer stacking of the aromatic rings.

Vanillyl and veratryl alcohols were used as monomeric lignin model compounds in experiments aiming to enhance the understanding of the lignin oxidation mechanisms involved in the oxygen delignification in acidic media catalysed by [PMo 7 V 5 O 40 ] 8− (HPA-5) heteropolyanion. Based on the model compound experiments, the first step of lignin oxidation is suggested to be a one-electron oxidation by the catalyst. This step is followed by coupling reactions and/or by further oxidation by the catalyst. The ratio of coupling/oxidation reaction products depends on the oxidation conditions and decreases with temperature raise. The higher oxidation rate of vanillyl alcohol as compared to the veratryl alcohol in the reaction system O 2 /HPA-5 was explained by the redox properties of the catalyst. The insufficiently high redox potential of HPA-5 did not allow the efficient oxidation of veratryl alcohol. The former was oxidised by VO 2 + ions dissociated from the HPA-5 under the acidic conditions. The reactivity of different lignin structural units in the reaction system O 2 /HPA-5 was estimated by electrochemical methods using various lignin model compounds.

The dissociation of the phenolic groups in a polydisperse, low molecular weight kraft lignin (Indulin AT) was studied in alkaline aqueous solutions in the temperature interval 21–70 °C, using a UV-spectrophotometric method. It was found that at a constant concentration of hydroxide ions, the degree of dissociation was decreasing when the temperature was elevated. Dissociation curves and apparent p Κ 0 values were also calculated for the polydisperse sample at the same conditions, using the van't Hoff and the Poisson-Boltzmann equations. At degrees of dissociation exceeding α ≈ 0.4, the outcome of the theoretical approach showed to be in good agreement with the experimentally obtained results. Furthermore, calculations were performed for different molecular weights of kraft lignin and from this it was found that the apparent p Κ 0 is shifted to higher values by increasing molecular weight, due to an increased electrostatic attraction of the hydrogen ions, which is arising from a less curved surface. Predictions of the dissociation behavior at temperatures reached in the kraft process were performed and under these conditions, higher molecular weight lignin fragments seem never to reach the point of complete dissociation. It was also found that an increase in temperature results in phase separation in kraft lignin solutions with high ionic strengths and pH values close to the p Κ a of the phenolic groups.

A kraft lignin was leached from a softwood pulp and fractionated by ultrafiltration. The fractions were characterized in respect to phenolic group content, molecular weight distributions and self-diffusion coefficients. The 1 H-Pulsed Field Gradient (PFG) NMR self-diffusion measurements and the High-Pressure Size Exclusion Chromatography (HPSEC) analysis of the fractions, were seen to correlate fairly well. From the self-diffusion measurements, the mass-weighted median hydrodynamic radii of the diffusants in the fractions, were calculated assuming spherical fragments. Furthermore, the content of phenolic groups in the fractions, was found to decrease by increasing hydrodynamic radius and molecular weight, but the calculated median surface charge densities of the macromolecules, were determined to be constant in the range of oligomers up to at least 65 structural units.

Acetic acid pulps (AAPs) have been converted to amphiphiles by hydroxypropylation. The resulting hydroxypropyl derivatives (HP-AAPs) formed self-aggregates in water. The interaction of HP-AAP molecules was investigated by a viscometric method. The reduced viscosity ( η sp /c) of HP-AAP in both water and chloroform was increased remarkably above a concentration of 0.1%. This implies that HP-AAP molecules strongly interact with each other, caused by the hydrophobic interaction of residual lignins in water and by hydrogen bonding of polysaccharides in chloroform. The self-aggregates adsorb water-soluble fluorescent agents. The highest adsorption capacity was observed at the lowest pH among three pH conditions investigated. They also solubilized sparingly water-soluble fluorescent agents in water in larger amounts than did sodium dodecyl sulfate when used as a surfactant. These results suggest that the self-aggregates of HP-AAP adsorb low molecular mass compounds as inclusion compounds. To clarify the interaction of HP-AAP with biopolymers as high molecular mass compounds, the change in the activity of papain, a protease, in phosphate buffer (pH 6.2) was examined in the presence and absence of HP-AAP. HP-AAP acted as an inhibitor of papain at the initial stage of mixing. After mixing for 24 hours, however, the papain activity was revived and preserved for 6 days. In contrast, the papain activity vanished in the absence of HP-AAP after 24 hours because of autolysis. Therefore, HP-AAP protects papain against autolysis, resulting from tight complexation with the biopolymer.

Populus tremula * Populus tremuloides wood samples were subjected to three-stage pulping in formic acid media with hydrogen peroxide addition, according to the Milox process. By means of three incomplete, second-order, centered, factorial designs, the effects of selected operational variables on the composition and technical properties of pulps were assessed for optimization purposes. Under the best conditions assayed, a pulp with 2.30% lignin, 87.0 % cellulose and 3.25% xylan was obtained at 53.2% pulp yield. Good SCAN viscosity (826 ml/g), reduced Kappa number (9.0) and satisfactory alkaline resistance (R-10 = 89.0; R-18 = 91.0) proved the potentiality of the selected pulp for dissolving pulp production.

In order to examine the possible influences of temperature on the wood constituents, two groups of wood species namely softwood (needle leaf wood) and hardwood (broad leaf wood) were subjected to heat or steam treatment during large radial compression between 0°C and 200°C. Two well-defined softening regions are observed. Both species showed the glass transition T g of lignin at ~ 90°C and ~ 60°C for softwood and hardwood respectively and a second transition region at ~ 160°C. The softening behavior between the first and second transition in softwood is in contrast with the softening behavior of hardwood. This difference reflects the difference in the distribution of the relaxation process due to lignin, which suggests the difference in chemical structure of lignin between softwood and hardwood.