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The aim of this study was to determine the changes occurring in the wood cellulose of the fast-growing poplar (Populus deltoides × maximowiczii) under the influence of steam explosion (SE) pretreatment. Cellulose from native wood and after pretreatment at 160 and 205 °C was isolated. Cellulose polymerization degree by size exclusion chromatography (SEC) and cellulose crystallinity index by Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) were determined. The profiles of sugars in the native wood and in the solid fraction after pretreatment (using the acid hydrolysis method) were also determined. In addition, the profile of monosaccharides in the liquid fraction obtained after steam explosion and in the liquid fraction after acid hydrolysis of the oligosaccharides were investigated using high-performance liquid chromatography (HPLC). This allowed to determine the change in the yield of hexoses and pentoses in the studied material. The behavior of cellulose in wood subjected to steam explosion at 160 and 205 °C and isolated by the Kürschner–Hoffer method was studied by determining the absorption bands of FTIR-ATR spectra. The lateral order index (LOI) of cellulose was calculated from the ratio of the intensity of the corresponding absorption bands A1422/A896 cm−1. Total crystallinity index (TCI) of cellulose was calculated from the ratio of the intensity of absorption bands A1372/A2900 cm−1. TCI of Kürschner-Hoffer cellulose isolated from wood subjected to steam explosion at 160 and 205 °C decreased by 5.6 and 5.0%, respectively, with regard to the applied temperature. LOI increased in cellulose isolated from wood subjected to steam explosion at 160 °C (by 0.7%) and at 205 °C (by 19.2%) in relation to the index of cellulose isolated from native wood. Kürschner–Hoffer cellulose isolated from wood subjected to steam explosion at 160 and 205 °C exhibited, respectively, a reduced degree of polymerization of about 11% and about 8%. Polydispersity index in Kürschner–Hoffer cellulose was 1% lower after both pretreatments than native sample. [ABSTRACT FROM AUTHOR]

Production of biofuel from lignocellulosic biomass is relatively low due to the limited knowledge about natural cell wall loosening and cellulolytic processes in plants. Industrial separation of cellulose fiber mass from lignin, its saccharification and alcoholic fermentation is still cost-ineffective and environmentally unfriendly. Assuming that the green transformation is inevitable and that new sources of raw materials for biofuels are needed, we decided to study cell death—a natural process occurring in plants in the context of reducing the recalcitrance of lignocellulose for the production of second-generation bioethanol. "Members of the enzyme families responsible for lysigenous aerenchyma formation were identified during the root hypoxia stress in Arabidopsis thaliana cell death mutants. The cell death regulatory genes, LESION SIMULATING DISEASE 1 (LSD1), PHYTOALEXIN DEFICIENT 4 (PAD4) and ENHANCED DISEASE SUSCEPTIBILITY 1 (EDS1) conditionally regulate the cell wall when suppressed in transgenic aspen. During four years of growth in the field, the following effects were observed: lignin content was reduced, the cellulose fiber polymerization degree increased and the growth itself was unaffected. The wood of transgenic trees was more efficient as a substrate for saccharification, alcoholic fermentation and bioethanol production. The presented results may trigger the development of novel biotechnologies in the biofuel industry. [ABSTRACT FROM AUTHOR]

The thermal modification of wood in a nitrogen atmosphere shapes the functional properties of wood. The aim of this research was to determine the influence of different levels of temperature and the duration of thermal modification on the mechanical properties of the black poplar (Populus nigra L.). Black poplar was thermally modified in nitrogen atmosphere in the temperature range from 160 °C to 220 °C (6 levels) for 2 h to 8 h (4 levels), resulting in a total of 24 treatments. The effect of these treatments on compressive strength parallel to the grain (CS), modulus of rupture (MOR), and modulus of elasticity during bending (MOE) were analyzed. Thermal modification influenced the mechanical properties of black poplar wood. After thermal modification occurred in a nitrogen atmosphere, an increase in compressive strength was noticeable for all variants of black poplar wood modification. The highest 16% increase in CS was obtained for the modification carried out at the temperature of 160 °C and for 2 h. An increase was also found for MOE when modified under mild conditions, while a decrease occurred for variants at higher temperatures, i.e., for 200 °C and 220 °C. The study showed that for all modification variants, there was a decrease in MOR alongside the increase in modification temperature and time. [ABSTRACT FROM AUTHOR]

The wood of five European species: black poplar (Populus nigra L.), European beech (Fagus sylvatica L.), European ash (Fraxinus excelsior L.), European oak (Quercus robur L.), and Scots pine (Pinus sylvestris L.) was subjected to thermal modification in nitrogen atmosphere at 190 °C during 6 h. Native and modified wood was varnished and oiled in industrial conditions. Thermally modified (TM) wood was characterized by a greater absorption of varnish and oil when applying the first layer to the surface, which finally resulted in higher application values compared to native wood. In particular, after varnishing, there was a significant increase in gloss and radical change of colour. Regardless of the wood species, finishing process (varnishing, oiling), the ΔE values were close to or higher than 6, which proves high colour changes. Modified poplar, ash, and oak after varnishing had a different colour (ΔE higher than 12). The surface colour changes as a result of UV photoaging was individual, depending on the wood species and the method of finishing. In the case of the thickness of varnish coatings, the wood structure was important, i.e., on ring-porous hardwood and softwood they were thicker. In the case of wood species with a lower density, i.e., black poplar and pine, the thermal modification in nitrogen atmosphere process did not reduce the resistance of the varnish coat, and in the case of species with a higher density (oak, ash, beech) it decreased by one level. Thermal modification reduced the Brinell hardness of wood with wide rays (oak and beech) by 11%. The applied process of surface finishing by double varnishing or oiling did not significantly change the hardness of tested wood. [ABSTRACT FROM AUTHOR]

The influence of bacterial cellulose gel film pretreatment methods on the efficiency of enzymatic hydrolysis was investigated. An increase in the efficiency of enzymatic hydrolysis due to liquid hot water pretreatment or steam explosion was shown. The glucose yield of 88% was obtained from raw, non-purified, bacterial cellulose treated at 130 °C. The results confirm the potential of bacterial cellulose gel film as a source for liquid biofuel production. [ABSTRACT FROM AUTHOR]

Black poplar (Populus nigra L.) was subjected to thermal modification in superheated steam. The modification was performed at 160 °C, 190 °C, and 220 °C for 2 h. The equilibrium moisture content of the black poplar wood was examined when it was exposed to 76% ± 2% relative humidity at a temperature of 20 °C ± 2 °C. The thermal modification of the poplar wood changed its moisture-exchange-related physical properties to a large extent. The effects of temperature on individual properties (density, mass loss, hygroscopicity, swelling, and water absorption) were diverse, and the intensity of these effects increased with increasing temperature of the thermal treatment process. In most cases, no significant differences were observed between the changes in properties of the sapwood and the heartwood. [ABSTRACT FROM AUTHOR]

Attenuated total reflectance (ATR) infrared (IR) spectroscopy analyses were performed with silver/white birch (Betula pendula/B. pubescens) and Scots pine (Pinus sylvestris) chips pretreated under alkaline (from 1 to 8% NaOH charge on wood dry solids) conditions to determine the suitability of this method in quickly determining chemical changes caused by varying treatment conditions on wood chemical structure. In addition to the alkali charge, pretreatment conditions varied with respect to temperature (130 and 150 °C) and treatment time (from 30 to 120 min). The spectral data of pretreated wood samples were compared to those of untreated reference samples, and the effects of the pretreatments conducted were determined based on these data. Results indicated that the most essential phenomena taking place during alkaline pretreatments could be detected by applying this simple and rapid spectral method requiring only a small sample amount. Such information included, for example, the cleavage of common lignin and carbohydrate bonds together with the significant removal of organics, especially hemicelluloses during pretreatments. [ABSTRACT FROM AUTHOR]

The main goal of this paper was to clarify to what extent extractives and wood structure determine the surface properties of hardwoods, mainly tropical. The role of wood extractives relative to properties, such as wettability and free surface energy, has been confirmed. The most significant seemed to be cyclohexane extractives. It was further found that in the case of tested tropical wood species, the extractives contents were high. Moreover the important role of axial parenchyma in wood wettability was established. It was established that multiple regression analysis could be useful in understanding wood properties as the result of the complex structure of wood. The obtained data is crucial from a practical point of view for its disclosure of those wood species that require surface modification prior to varnish coating. [ABSTRACT FROM AUTHOR]

The following paper presents an environmental examination and the results of the selected analyses of archaeological waterlogged oak wood (Quercus sp.) obtained from excavations carried out at the early medieval site of Czermno in eastern Poland near the Ukrainian border. Due to the good state of preservation of the wood tissue (De Jong's classification class III - maximum moisture content Umax < 185%) and its deposition in near anaerobic layers (reed peat and calcareous gyttja) an attempt was made to obtain the DNA sequence from samples acquired from the uncovered historical construction. In the course of the research, a DNA sequence was obtained from one sample derived from the trial pit W4/2014, the radiocarbon dated to 776-982 calAD. A comparison of the DNA data extracted from the historical wood to two sequences obtained from the trees (Quercus robur L.) growing near the site of Czermno, indicates clear similarities between each of them. The DNA sequence obtained from the archaeological oak wood confirms the assumption that proximate anaerobic layers, under specific conditions, can inhibit the degradation of DNA structure. [ABSTRACT FROM AUTHOR]

The main objective of this research was to investigate tropical wood sorptive properties. For selected tropical wood species (courbaril, ipe, light red meranti, merbau, tatajuba, and teak), the equilibrium moisture content was determined at 20 °C and 9, 30, 55, 70, and 97% relative humidity. The experimentally determined values were analysed using the Hailwood-Horrobin sorption model to compute the fibre saturation point and mono- and multi-layer sorption. There were significant differences in the sorption behaviour of different wood species. Generally, the fibre saturation point of tropical wood species is lower than in wood species from moderate climate zones. The lowest values of fibre saturation point were found for ipe (18.7%), courbaril (20.4%), and tatajuba (20.5%). Furthermore, chloroform-ethanol extractives content was correlated with multilayer sorption and the fibre saturation point, such that a higher content of chloroform-ethanol extractives was associated with a lower equilibrium moisture content. Therefore, chemisorption was not influenced by chloroform-ethanol extractives. Ethanol extracts showed an influence on monomolecular-bound water. [ABSTRACT FROM AUTHOR]

X-ray fluorescence (XRF) analysis of six metals: chromium, manganese, iron, nickel, copper and zinc (possible inhibitors of enzymatic hydrolysis of wood) in samples of two poplar species, Populus trichocarpa and Populus maximowiczii, was performed in order to check which of them collect more of the metallic inhibitors during tree growth and steam explosion pretreatment. The XRF point scan (for solid and ashed wood) and mapping (for stem cross-sections) options were used. Samples of the different parts - stem, branches, leaves and bark were studied. Steam explosion at 130°C, 160°C and 190°C was performed on both species and the influence of steam on the chosen metals content was analysed. On the basis of the results, P. trichocarpa is the species which accumulates a higher amount of the metals during tree growth and P. maximowiczii - during steam explosion. [ABSTRACT FROM AUTHOR]

Alkaline pre-treatments were performed for the production of organicscontaining effluents from silver/white birch (Betula pendula/pubescens) and Scots pine (Pinus sylvestris) chips prior to chemical pulping. Pretreatment conditions were varied with respect to time (from 30 min to 120 min), temperature (130 °C and 150 °C), and alkali charge (1, 2, 3, 4, 6, and 8% of NaOH on oven-dried wood). The analytical data (total content, weight average molar mass, and molar mass distribution) on dissolved lignin were subjected to principal component analysis to examine the relationship between molar mass and molar mass distributions in lignin removed from different wood species under varying alkaline pre-treatment conditions. Using this method, differences between the wood species and effects of the various pre-treatment process variables (i.e., time, temperature, and alkali charge) were determined. [ABSTRACT FROM AUTHOR]

The article presents the results of a test on the resistance of Neolithic waterlogged beech wood (Fagus sylvatica L.) to destruction by subterranean Reticulitermes lucifugus Rossi. Methodology consistent with the ASTM D 3345-08 Standard was applied in the experiment. In the coercion test, the modern beech wood was destroyed at an intermediate stage between light attack and moderate attack with penetration, whereas the pine sapwood was heavily damaged. Under the same conditions, the waterlogged beech wood was seriously damaged or completely destroyed by the termites. However, unlike the modern pine and beech wood, all the termites died after feeding on the waterlogged beech wood. In spite of the complete destruction of the waterlogged beech wood in the coercion test, it seems that under natural conditions where there is a possible choice between different wood species, the infestation by termites of waterlogged wood uncovered in archaeological work does not necessarily happen. Wood containing few nutritional substances and substantial lignin, as well as having a high moisture content facilitating the development of parasitic microorganisms, will deter termites. [ABSTRACT FROM AUTHOR]

The PHYTOALEXIN DEFICIENT 4 ( PAD 4) gene in A rabidopsis thaliana ( AtPAD 4) is involved in the regulation of plant - pathogen interactions. The role of PAD 4 in woody plants is not known; therefore, we characterized its function in hybrid aspen and its role in reactive oxygen species ( ROS)-dependent signalling and wood development. Three independent transgenic lines with different suppression levels of poplar PAD expression were generated. All these lines displayed deregulated ROS metabolism, which was manifested by an increased H 2 O 2 level in the leaves and shoots, and higher activities of manganese superoxide dismutase ( MnSOD) and catalase ( CAT) in the leaves in comparison to the wild-type plants. However, no changes in non-photochemical quenching ( NPQ) between the transgenic lines and wild type were observed in the leaves. Moreover, changes in the ROS metabolism in the pad4 transgenic lines positively correlated with wood formation. A higher rate of cell division, decreased tracheid average size and numbers, and increased cell wall thickness were observed. The results presented here suggest that the P opulus tremula × tremuloides PAD gene might be involved in the regulation of cellular ROS homeostasis and in the cell division - cell death balance that is associated with wood development. [ABSTRACT FROM AUTHOR]

Thermal modification of wood in nitrogen atmosphere permits its usability value to be improved. The aim of the research was to determine the impact of technological modification parameters at different levels on the colour of black poplar (Populus nigra L.). Black poplar was thermally modified in nitrogen atmosphere at a range of temperatures from 160 °C to 220 °C, at times between 2 h and 8 h. The parameters of wood colour were measured according to the CIE L*a*b* colour space model. The changes in a* and b* had a non-linear profile. The maximum value of a* for black poplar wood was achieved after a modification at the temperature of 200 °C, while the maximum value of the b* parameter was achieved after modification at 190 °C. Colour changes in the ΔE of black poplar after modification at 160 °C and 170 °C were similar, and the dynamics of changes increased after modification at the temperature of 180 °C. The highest value of ΔE, around 40, was observed after modification at the temperature of 220 °C and time of 8 h. There were no statistically significant differences between the ΔE for radial and tangential sections. Statistical analysis showed that modification temperature was responsible for the variability of the L* value in 90%, and in ca. 70% for the changes in parameters a* and b*. The influence of the modification time on the colour parameters was minor—below 4%. The influence of the interaction between modification temperature and time on the colour parameters was below 10%. As a consequence, in the case of ΔE of black poplar wood, the influence of temperature was at a level of ca. 80%. On the other hand, the influence of time and the interaction between temperature and time of modification was low—below 3%. [ABSTRACT FROM AUTHOR]

Black poplar (Populus nigra L.) was thermally modified in nitrogen atmosphere. The effects of the modification process on poplar wood were evaluated for temperatures: 160 °C, 190 °C, and 220 °C applied for 2 h; and 160 °C and 190 °C for 6 h. The percentual impact of temperature and time of modification on the properties of modified wood was analysed. The study permitted the identification correlations between the chemical composition and selected physical properties of thermally modified poplar wood. The dimensional stability of poplar wood was improved after thermal modification in nitrogen. The higher the temperature of modification, the lower the equilibrium moisture content (EMC) of black poplar. At the temperature of 220 °C, EMC was two times lower than the EMC of non-modified black poplar. It is also possible to reduce the dimensional changes of wood two-fold (at the modification temperature of 220 °C), both in radial and tangential directions, independently of the acclimatization conditions (from 34% to 98% relative humidity, RH). Similar correlations have been found for wood that has been soaked in water. Higher modification temperatures and longer processing times contributed to a lower swelling anisotropy (SA). [ABSTRACT FROM AUTHOR]