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Pine-wood (Pinus sylvestris L.) was thermally modified at temperatures of 160°C and 200°C for 2, 6 and 10 hour periods, respectively. The severe conditions of the heat treatment resulted in decreased mechanical properties (compressive strength and modulus of elasticity) and a decrease in the degree of cellulose polymerization. A comparison of selected mechanical properties and the degree of cellulose polymerization indicated that there was a relationship between them and the temperature and duration of the heat treatment. [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]

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]

This paper presents the effect of water extracts from the leaves of various Mentha spp. on the growth of selected fungi causing the gray decay of wood. The study determined which of the Mentha spp. extracts used had the best effect on inhibiting the development of fungi on various substrates including pine wood. The best results in the complete inhibition of fungi growth on an agar medium were obtained for the M. × piperita 'Almira' extract. Biocidal properties were not achieved on wood samples, although it was noticed that at doses of extracts of 600 g/m2 and higher, the growth of fungi in the initial stages of cultivation was clearly inhibited. Chemical substances in the obtained extracts were characterized by gas chromatography. Oxygen monoterpenes were the dominant group of substances, substances belonging to sesquiterpene hydrocarbons, monoterpene hydrocarbons containing oxygen sesquiterpenes, and one substance belonging to non-terpene hydrocarbons were also identified. [ABSTRACT FROM AUTHOR]

In the paper, three different physico-chemical pretreatment methods in relation to bioethanol production were compared. The wood of fast-growing poplar species (Populus deltoides x maximowiczii and Populus trichocarpa Torr. & A. Gray ex Hook) and corn stover were used as a feedstock. The chemical composition and enzymatic hydrolysis efficiency of the biomass before and after pretreatments were compared. On the basis of the results, it was concluded that the applied pretreatments changed the chemical composition of the raw materials. In the case of the acid and LHW (liquid hot water pretreatment) methods, up to 93.7% of hemicelluloses (especially pentosans) were removed. From among the selected pretreatment methods, the LHW and alkaline methods occurred to be the most interesting. Nevertheless, from the bioethanol production point of view, the LHW process of Populus deltoides x maximowiczii wood was the best because after enzymatic hydrolysis, high amounts of glucose (up to 600.9 mg/g pretreated biomass) and minor amounts of xylose (up to 37.9 mg/g pretreated biomass) were produced. Moreover, based on the chemical composition and sugar profile analysis, it was proved that the Populus trichocarpa wood also has a high potential for bioethanol production. [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 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]

In this paper, the influence of physicochemical pretreatment methods on the chemical composition, enzymatic hydrolysis efficiency and porosity of fast-growing Populus trichocarpa wood was compared. Among the pretreatment methods, the liquid hot water (LHW) and steam explosion (SE) were used, which were performed at three different temperatures (160 °C, 175 °C and 190 °C) and two residence times (15 min and 1 h). The chemical composition, enzymatic hydrolysis and porosity analysis were done for native wood and solid fraction obtained after LHW and SE pretreatments. The porosity analysis was performed by inverse size exclusion chromatography method. Additionally, inhibitors of hydrolysis and fermentation processes in the liquid and solid fractions obtained after pretreatments were examined. Based on the results, it was found that the tested pretreatments caused the greatest changes in the chemical content of hemicelluloses. It was found that after LHW and SE pretreatments up to 99.1% or 94.0%, respectively, of hemicelluloses were removed from the obtained solid fraction. Moreover, the LHW and SE processes greatly enhanced the enzymatic digestibility of fast-growing poplar wood. The highest glucose yield was achieved after 15 min of SE pretreatment at 190 °C and was 676.4 mg/g pretreated biomass, while in the case of xylose the highest value (119.3 mg/g pretreated biomass) was obtained after 15 min of LHW pretreatment at 160 °C. Generally, after SE pretreatment process, more inhibitors were formed, and a greater effect of porous structure development was noticed than after LHW pretreatment. Despite this difference, the average glucose contents and yields after enzymatic hydrolysis of pretreated biomass were generally similar regardless of the pretreatment used. [ABSTRACT FROM AUTHOR]

o-Xylene, phenol and toluene were nitrated with 100% nitric acid on MoO3/SiO2, WO3/SiO2, TiO2/SiO2, and TiO2–WO3/SiO2 systems. Phenol and toluene were nitrated with yields higher than 90%, and the 10% and 15% MoO3/SiO2 catalysts were most active in the nitration of o-xylene. The most active catalysts exhibited the para-position selectivity of nitration. [ABSTRACT FROM AUTHOR]

This study examined how nutrients present in the growth environment of microorganisms forming a consortium of bacteria and yeasts, called a symbiotic culture of bacteria and yeast (SCOBY), affect the efficiency of cellulose synthesis and selected properties of the cellulose, such as gloss and color. The results showed that nitrogen-rich ingredients, such as peptone and green tea, increased the efficiency of polymer synthesis and determined the cellulose's gloss. This research showed that the qualitative characteristics of bacterial cellulose can be easily modified by the appropriate selection of the components of the culture media. [ABSTRACT FROM AUTHOR]

Preliminary studies are presented showing to what extent nutrients available in the growth environment of Kombucha microorganisms affect the physical and mechanical properties of synthesized cellulose. With an increase in the amount of sucrose in the growth medium and with the presence of additional nutrients, peptone and tea extract, the thickness and strength of the biopolymer increased, while elongation was reduced. The best physical and mechanical parameters were obtained for bacterial cellulose from cultures with the addition of 10% sucrose and 0.25% peptone content. The increase in elongation correlated with the decrease in the degree of polymerization, which means that in media rich in nutrients, the number of molecules building the polymer decreases. The presented data is important in order to select ingredients that will help synthesize bacterial cellulose with the desired physio-mechanical properties. [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]

Studies were undertaken of the influence of both the natural stabilizers present in wood (lignin and extractives) and synthetic antioxidants on the thermal ageing of cellulose. Among the synthetic antioxidants, butylated hydroxytoluene, propyl gallate and 6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline (ethoxyquin) were examined. In order to study the thermal ageing of cellulose with antioxidants, accelerated ageing tests were carried out under various conditions. The ageing tests were performed at a temperature of 95 °C in an air and nitrogen atmosphere in anhydrous conditions and at 65% relative air humidity. To study the degradation of the cellulose, size exclusion chromatography was used. The results revealed that ethoxyquin was the best synthetic stabilizer. In addition, butylated hydroxytoluene had stabilizing properties and slowed down the depolymerisation of the cellulose. In turn, the behaviour of the propyl gallate under elevated temperature conditions was the most interesting. This antioxidant, relating to the cellulose degradation process, showed inhibitory as well as catalytic properties under specific conditions. In the ageing conditions applied, the smallest decrease was observed in the average molar mass of the cellulose in the wood without extractives. The results indicate that in this case, lignin played a very important role as a hidden antioxidant. In the presence of the lignin, oxidative the cellulose depolymerisation process proceeded more slowly than with the participation of synthetic antioxidants. The extractives, under elevated temperature conditions, did not show stabilizing properties, and furthermore, they accelerated the degradation of the cellulose. [ABSTRACT FROM AUTHOR]

This study aimed to determine glucose and xylose content by acid hydrolysis of wood samples, both unmodified and thermally modified (modification time was 2, 6, 10 hours), using high performance liquid chromatography. Optimization of the hydrolysis process on the native ash wood samples showed that 3 h was the best time in the hydrolysis process. After that time, 58.8% of glucose and 20.8% of xylose were obtained. In turn, chromatographic analysis showed incomplete hydrolysis of ash wood samples, which were modified in a nitrogen atmosphere, especially at shorter times (2 and 6 h) of modification. With longer modification times (10 h), the hydrolysis of ash wood samples was completed. The above mentioned problem was caused mainly by the increase of cellulose crystallinity degree. The decrease of this parameter was observed only after 10 h of thermal modification, which would facilitate the process of acidic hydrolysis. Additionally, it was observed that the thermal modification of ash wood at 190 °C in a nitrogen atmosphere for 10 h caused a drastic decrease in the xylose content (from 20.8% to 8.0%) and only a slight decrease in the glucose content (from 58.8% to 54.9%). [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]