Volume 73, Issue 7

Synchrotron radiation X-ray diffraction (XRD) was applied to determine the cellulose content in 5-mm-thick sections of the annual rings of Japanese red pine ( Pinus densiflora ). Recent samples (air-dried in the last few years) and aged samples (250 years old) were investigated; the cellulose content in the S2 layer was measured by the transmission (Trs) method and that in the S1 and S3 layers by the reflection (Ref) method. Measurements were performed in the cellulose (004) Ref plane. The two XRD methods resulted in very different two-dimensional (2D) diffraction patterns, indicating differences in the cellulose characteristics. Azimuthal angle profiles showed cellulose chains measured by the Trs and the Ref methods oriented at about 9° and 75°, respectively, in terms of the longitudinal axis of the specimens. Moreover, 2 θ profiles obtained by the Ref method had full-width-at-half-maximum (FWHM) values ≈3.5 times greater than the corresponding Trs profiles, indicating large variations in the cellulose lattice spacing d 004 . The 250 years of aging had no effect on the cellulose contents.

The ratio of juvenile wood (jW) to mature wood (mW) is relevant for structural wood applications because of their different properties. Near infrared-hyperspectral imaging (NIR-HI) indicates after calibration, the spatial distribution of jW and mW, and this approach is less time consuming than the established micro X-ray densitometry (μXRD). In the present study, a comparative detection of the jW and mW of Pinus sylvestris L. was performed by NIR-HI and μXRD and the NIR-HI results were evaluated in combination with three chemometric approaches, namely, the principal component analysis (PCA), partitional k-means unsupervised classification (p-k-mUC) and partial least squares discriminant analysis (PLS-DA) in the range of 900–1700 nm. The best NIR-HI results can be obtained when the transition point of earlywood (EW) and latewood (LW) are assessed separately by PLS-DA. The presented results are useful for an automating data evaluation and simplified data collection.

The pits on parenchyma cell walls facilitate transfer of liquids between adjacent cells in the bamboo. To better understand the structure-function relationship of the pits, the structural characteristics of the pits in bamboo parenchyma cells need to be investigated. In this study, the pit structures were studied by field-emission environmental scanning electron microscopy (SEM). The samples included the native structure and the replica structure via resin castings. The results showed that the parenchyma cells possessed various shapes and the pits were diverse. Parenchyma cells exposed both simple and bordered pits. Pitting between vascular parenchyma cells (VPCs) was similar to that of the metaxylem vessel. In particular, a branched pit structure was found for the first time in the parenchyma cell.

Most of the wood bark produced by the forestry production is discarded in spite of containing many kinds of the phytochemical ingredients. The aim of the present study was to identify secondary metabolites from the bark of Larix kaempferi generated as waste material and evaluate their potential as cosmetic agents. Eighteen compounds, including a novel phenanthrene, 4,6,7-trihydroxyphenanthrene-2- O - β -D-glucopyranoside ( 16 ), were isolated from the bark of L. kaempferi and identified by matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) and nuclear magnetic resonance (NMR). In addition, the tyrosinase inhibitory activity of these compounds was evaluated. Procyanidin B7 ( 18 ) exhibited the most potent inhibition with IC 50 values of 31.0 μM and 61.8 μM when using L-tyrosine and L-dopa as the substrate, respectively, which were similar to those of the positive control, kojic acid. Interestingly, quercetin-3- O - α -L-rhamnopyranoside ( 10 ) was shown to possess the tyrosinase inhibition although the other series of 3-glycoylated flavonols were not active, suggesting that the rhamnosyl group at C-3 and the hydroxyl group at C-3ʹ played an indispensable role in the anti-tyrosinase activity. These findings indicate that a number of constituents from L. kaempferi bark may have potential as additives in cosmetics.

Dissolved matter (DM) in the oxygen delignification (O 2 Del) stage affects the lignin and carbohydrate degradation. To understand this topic better, laboratory O 2 Del experiments were conducted with controlled addition of either unoxidized dissolved matter (UnoxDM) originating from the cooking stage or oxidized dissolved matter (OxDM) recycled from the post-O 2 Del washing. The presence of UnoxDM decreased the delignification, while the presence of OxDM showed the opposite effect, both compared to a well-washed pulp and at the same alkali charge level. However, both types of DM had a negative impact on the carbohydrate degradation. The distribution between these DMs will affect the resulting lignin degradation, because the filtrate accompanying the fibers into the O 2 Del stage is a mixture of UnoxDM and OxDM. It is proposed that the positive impact on the delignification by OxDM is due to the high carbonate ion concentration in the filtrate. Further, the high content of thiosulfate ions in the UnoxDM was one of the reasons for the lower delignification in its presence.

The chemical changes in birch wood occurring at thermo-hydro treatment (THT) was studied at temperatures (T) of 150, 160 and 170°C by analytical pyrolysis [Py-gas chromatography/mass spectrometry/flame ionisation detector (GC/MS/FID)], elemental analysis and traditional wet-chemical analysis. THT wood (THTW) was also extracted with acetone. Mass losses (ML) due to THT and acetone extraction of THTW were considered for material balance calculations. The holocellulose and hemicellulose (HC) contents decrease with increasing THT temperature (THT T ), thus the apparent lignin content is elevated by ca. 20%. The HC degradation begins at 150°C, while that of α-cellulose modification at 170°C. Compared to unmodified birch, the THT 170°C material contains ca. 10% less α-cellulose and up to 40% less HC. The Py-GC/MS also indicates decreasing amounts of volatile products from polymeric carbohydrates (CHs) and lignin origin as a function of increasing THT T . The identified CH-based Py products of THT 170°C of non-extracted (ne) and extracted (e) materials resulted in 13 and 22% weight decrements, respectively, while the lignin-type Py products were reduced by 13 and 49%, respectively. With increasing THT T , the total content of CO 2 , water and methanol decreases, and the amount of unidentified compounds increases by 30%.

The fracture properties of thermally modified beech ( Fagus sylvatica ) wood (TMW) at 180° and 200°C were evaluated in mode II using the three-point end-notched flexure (3ENF) scheme assisted by three-dimensional (3D) stereovision equipment for obtaining displacements and strains. The compliance-based beam method (CBBM) provided the strain energy release rates ( G II ) of TMW and cohesive laws for both native wood (W) and TMW. Based on the CBBM and equivalent crack length approach (ECLA), G II was obtained directly from the force-deflection data. The thermal modification (TM) process reduced the compressive strength by 4.4% and increased the compressive elastic modulus by 38.3%, whereas G II was reduced substantially by 40.8% and 67.9% at TM 180°C and TM 200°C , respectively. TM also increased wood brittleness that was visible on the displacement slip reduction. The resulting mean cohesive models can be used for numerical analyses. The fracture properties of TMW have to be taken into consideration for constructional wood application, when cyclic loading may lead to microcracking and material fatigue.

The initial stage of cellulose degradation has been studied via in vitro assays of fungi isolated from rotten wood in a boreal forest. Among the 37 isolates, Antrodia sinuosa appeared to be an effective cellulose degrader and was selected for studying the initial degradation process. In the liquid cultivation with carboxymethylcellulose (CMC), the increase of the mycelial dry weight coincided with the pH decrease of the culture medium from pH 5.7 to 3.9, between the 3 rd and 6 th cultivation day. At the same time, the cellulolytic activity increased; the CMCase activity increased sharply and the reducing sugars reached their maximum concentration in the culture medium. It seems that the decreasing pH enables the cellulose degradation by A. sinuosa at an early stage of the process. The results of this study may be useful for a more efficient industrial application of biomass by means of brown-rot fungi.

Sugar-containing hydrolysates as byproducts of dissolving pulp production could be a source of alcohol production, but the presence of fermentation inhibitors hampers this utilization route. In the present study, nine types of phenolic inhibitors were found and their removal by ligninases gave satisfactory results. Laccase removed 73.1% of phenolic inhibitors and produced three new aromatic compounds, whereas the combination of laccase and lignin peroxidase (as a dual-enzyme treatment) resulted in a removal rate of 91.7% without new product formation. Xylose as the main sugar in the hydrolysate was retained with a 90% yield, regardless of the enzymatic treatment, which modified, however, the kinetics of yeast growth. Laccase improved cells’ maximum specific growth rate ( v max ) from 0.115 to 0.154 and reduced the saturation constant ( K s ) from 53.4 to 42.5, whereas the dual-enzyme system improved v max to 0.206 and reduced K s to 42.44. The greater v max and the smaller K s imply a better growth rate, and accordingly, the dual-enzyme system is better suited for removing phenolic inhibitors.

Bamboo fibers (BFs) are abundant but underutilized as reinforcing fibers in wood plastic composites (WPCs). BFs were investigated as reinforcing fibers for unsaturated polyester (UPE) composites (BF-UPE). The UPE was prepared from condensation polymerization of propylene glycol (PG), isophthalic acid (IPA) and maleic anhydride (MA). Acrylated epoxidized soybean oil (AESO) was used instead of styrene which is usually applied as a diluent in most of the commercial UPE resins. The properties of BF-UPE were compared with those of kenaf fibers-UPE (KF-UPE). BF-AESO-UPE composites had tensile strengths (TSs), which were comparable to those of BF-styrene-UPE composites, while their flexural strength (FS) and impact strength (IS) were higher than those of BF-styrene-UPE composites. The glass transition temperature ( T g ) of BF-AESO-UPE composites was lower than that of BF-styrene-UPE composites. BF-AESO-UPE composites had lower TS than KF-AESO-UPE composites, while their FS was comparable to that of KF-AESO-UPE composites.

The main aim of this investigation was to study the interaction of cationised xylans as antimicrobial substances with poly(ethylene terephthalate) (PET) model films, prepared by spin coating. A quartz crystal microbalance (QCM-D) with dissipation monitoring was applied as a nanogram sensitive balance to detect the amount of adsorbed cationised xylans. The xylan adsorption onto PET model films was studied as a function of pH and ionic strength. To improve the adsorption, positively charged polyethylenimid (PEI) and negatively charged polyvinyl-sulfonic acid (PVSA), as sodium salt, were applied as anchoring polymers. Surface free energies and hydrophilic/hydrophobic properties of surfaces were monitored by goniometry. Cationised xylans favourably deposited at pH 5, where beside electrostatic, physical interactions are possible, and adsorption may be driven by entropy gain. Higher ionic strengths of solutions also improved adsorption, due to the lower water solubilities of xylans. When intermediate layers of chosen anchoring polymers were applied on the PET surfaces, the binding of xylans as well as their coating durability were improved. Surface modifications presented in this work, provided important information regarding the adsorption/desorption phenomena between antimicrobial cationised xylans and synthetic PET surfaces. The latter is of great interest, when composing hydrophilic and antimicrobial PET surfaces for medical applications.