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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]

Effects of soaking aqueous ammonia pretreatment were considered for fast-growing poplar wood in the context of bioethanol production. The milled Populus trichocarpa wood with a particle size of 0.43 to 1.02 mm was pretreated at two temperatures (50 °C and 90 °C) and two concentrations of ammonia solution (15% and 20% w/w) for 20 h. The lignin content decreased by 46% in the biomass treated with the most severe conditions. After enzymatic hydrolysis, the sugar yield was analysed, and the results indicated that increased temperature and ammonia concentration during pretreatment resulted in higher glucose content. Additionally, changes in the degree of polymerization and available pore volume were investigated. [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]

This paper compares the acid and enzymatic hydrolysis in relation to bioethanol production. The pulp obtained from wood of the fast-growing poplar species (Populus deltoides x maximowiczii and Populus trichocarpa Torr. & A. Gray ex Hook) was used as a feedstock. The delignification process by the Kraft method was carried out with 19% and 26% of active alkali (NaOH and Na2S). The obtained sugars (xylose and glucose) were analyzed by a high-performance liquid chromatography. The results concluded that the enzymatic hydrolysis process is better than acid hydrolysis because a higher content of sugars (especially xylose) was obtained. Additionally, after the acid and enzymatic hydrolysis process from Populus trichocarpa pulp, more sugars were obtained than from the pulp of Populus deltoides × maximowiczii. The Kraft pulp from the wood of fast-growing poplar species is a good raw material for the production of glucose. However, in order to obtain a higher xylose content and finally increase the profitability of bioethanol production, a new method should be developed, or the Kraft method should be optimized. [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]

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]