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The upturn of viscose fiber market has triggered an augmented dissolving pulp usage over the last decade. Dissolving pulp is feasible to obtain from kraft pulp after two essential steps including hemicellulose removal and subsequent pulp activation. Prerequisite of conversion being hemicellulose reduction can be gently done by using xylanase treatment prior to alkali extraction. Herein, the significance of xylanase treatment and the optimum xylanase dose required in conjunction with subsequent alkali extraction was investigated. An increase in xylanase dose prior to alkali extraction had no significant effect on pentosans while the Fock reactivity and viscosity both improved at the dose of 50AXU/g. Also, alkali extraction without xylanase pretreatment resulted in decreased Fock reactivity, alpha cellulose, brightness and viscosity of paper grade pulp. A moderate dose of xylanase prior to alkali extraction can thus be used to facilitate the hemicellulose removal while simultaneously protecting the native structure of cellulose., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Prehydrolysis of lignocellulose produces abundant hemicellulose-derived saccharides (HDS). To obtain pure HDS for application in food or pharmaceutical industries, the prehydrolysis liquor (PHL) must be refined to remove non-saccharide compounds (NSC) derived from lignin depolymerization and carbohydrate degradation. In this work, activated carbon (AC) adsorption was employed to purify HDS from NSC with emphasis on adsorption selectivity. The adsorption isotherms showed the priority of NSC to be absorbed over HDS at low AC level. However, increase of AC over 90% of NSC removal made adsorption non-selective due to competitive adsorption between NSC and HDS. Size exclusion chromatography showed that the adsorption of oligomeric HDS was dominant while monomeric HDS was inappreciable. The limited selectivity suggested that AC adsorption is infeasibility for HDS purification, but applicable as a pretreatment method., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

A combined process of lime treatment and mixed bed ion exchange was proposed to separate hemicellulose-derived saccharides (HDS) from prehydrolysis liquor (PHL) of lignocellulose as value added products. The optimization of lime treatment achieved up to 44.2% removal of non-saccharide organic compounds (NSOC), mainly colloidal substances, with negligible HDS degradation at 0.5% lime level and subsequent neutralization by phosphoric acid. The residual NSOC and calcium ions in lime-treated PHL were eliminated by mixed bed ion exchange. The breakthrough curves of HDS and NSOC showed selective retention toward NSOC, leading to 75% HDS recovery with 95% purity at 17 bed volumes of exchange capacity. In addition, macroporous resin showed higher exchange capacity than gel resin as indicated by the triple processing volume. The remarkable selectivity of the combined process suggested the feasibility for HDS separation from PHL., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

In the present study, a graded ethanol precipitation technique was employed to obtain hemicelluloses from the alkali-extracted corncob liquid. The relationship between the structural characteristics of alkali-soluble corncob hemicelluloses and the production of furfural was investigated by a heterogeneous process in a biphasic system. Results showed that alkali-soluble corncob hemicelluloses mainly consisted of glucuronoarabinoxylans and L-arabino-(4-O-methylglucurono)-D-xylans, and the drying way had less influence on the sugar composition, molecular weights and the functional groups of hemicelluloses obtained by the different ethanol concentration precipitation except for the thermal property, the amorphous structure and the ability for the furfural production. Furthermore, alkali-soluble corncob hemicelluloses with higher xylose content, lower branch degree, higher polydispersity and crystallinity contributed to the furfural production. A highest furfural yield of 45.41% with the xylose conversion efficiency of 99.06% and the furfural selectivity of 45.84% was obtained from the oven-dried hemicelluloses precipitated at the 30% (v/v) ethanol concentration., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

A modified process consisting of an initial mechanical refining (R) followed by a low-alkali (5.5% NaOH) cold caustic extraction (CCE) and finally an endoglucanase (EG) treatment (R-5.5%CCE-EG) was investigated for upgrading paper-grade pulp to dissolving pulp. Results showed that compared to the conventional process (9%CCE-EG), the modified process can decrease the alkali concentration (from 9% to 5.5%) to achieve a similar hemicelluloses removal while simultaneously enhancing the Fock reactivity (from 62.2% to 81.0%). The improved results were due to the fact that the mechanical refining resulted in favorable fiber morphological changes, including increased pore volume/size, water retention value and specific surface area. Consequently, the hemicelluloses removal was enhanced even under the subsequent low-alkali CCE condition. A synergic effect of refining, low alkali concentration and enzymatic activation was responsible for the higher reactivity of resulting dissolving pulp., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Prehydrolysis of wood biomass prior to kraft cooking provides a stream containing hemicellulose-derived saccharides (HDSs) but also undesired non-saccharide compounds (NSCs) that were resulted from lignin depolymerization and carbohydrate degradation. In this study, a combined process consisting of lime treatment, resin adsorption, and gel filtration was developed to separate HDSs from NSCs. The macro-lignin impurities that accounted for 32.2% of NSCs were removed by lime treatment at 1.2% dosage with negligible HDSs loss. The majority of NSCs, lignin-derived phenolics, were eliminated by mixed bed ion exchange resin, elevating NSCs removal to 94.0%. The remaining NSCs, furfural and hydroxymethylfurfural, were excluded from HDSs by gel filtration. Chemical composition analysis showed that xylooligosaccharides (XOS) with the degree of depolymerization from 2 to 6 accounted for 28% of the total purified HDSs., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Hemicelluloses removal is a prerequisite for the production of high-quality cellulose (also known as dissolving pulp), and further recovery and utilization of hemicelluloses, which can be considered as a typical Integrated Forest Biorefinery concept. In this paper, a process of combined mechanical refining and cold caustic extraction (CCE), which was applied to a softwood sulfite sample, was investigated. The results showed that the hemicelluloses removal efficiency and selectivity were higher for the combined treatment than that for the CCE alone. The combined treatment can thus decrease the alkali concentration (from 8% to 4%) to achieve a similar hemicelluloses removal. The improved results were due to the fact that the mechanical refining resulted in increases in pore volume and diameter, water retention value (WRV) and specific surface area (SSA), all of which can make positive contributions to the hemicelluloses removal in the subsequent CCE process., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Liquid hot water (LHW) extraction was used as a pretreatment method to separate the hemicellulose fraction from dried distiller's grain with solubles (DDGS) into liquid phase. Acid hydrolysis using 3.264 % w/w sulfuric acid at 130 °C was performed to convert polysaccharides in LHW extract to monosaccharides. The structure characterization of DDGS in anomeric carbon region based on proton NMR and heteronuclear single quantum coherence (HSQC) during acid hydrolysis was studied in this work. It reveals that the sugar units in DDGS hemicelluloses are constructed with (1-4)-β-D-xylopyranose and α-L-arabinofuranosyl residues. A kinetic model is included to explain the changing concentration of monomer, oligomer, and sugar units. The model was further tested based on the changing concentration of five carbon sugar units during hydrolysis.

Hemicelluloses removal is highly desirable in many biomass processes, including the pretreatment steps of the bioconversion for ethanol production, production of high-quality dissolving pulps. In this study, a sequential treatment consisting of pulp fractionation, followed by caustic treatment to remove hemicelluloses from a softwood sulfite pulp, was investigated. The long-fiber fraction obtained after pulp fractionation, had a lower hemicelluloses content and smaller specific surface area, but larger pore diameter than the short-fiber fraction. The fiber fractions were subsequently treated in a cold caustic extraction (CCE) or hot caustic extraction (HCE). Results showed that hemicelluloses removal in the long-fiber fraction was more pronounced than the short-fiber fraction in both CCE and HCE processes. Other parameters, such as hemicelluloses removal selectivity, yield were studied. The underlying explanations were given., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Adsorption of native eucalyptus heteropolysaccharides onto bleached softwood and hardwood kraft pulps and bleached CTMP was explored in this work to potentially improve the mechanical properties of the final furnish. It was found that adsorption of native heteropolysaccharides onto softwood kraft pulp was slightly higher than hardwood; however, heteropolysaccharides with low arabinose content were preferentially adsorbed onto the hardwood fibers. Adsorption onto CTMP was the lowest, although the general phenomenon of native absorption was rather low under the applied conditions. A strategy to increase the absorption required cationizing the heteropolysaccharides with 2,3-epoxy propyltrimethylamonium chloride that in general significantly increased the overall phenomenon, again with the same general tendencies as observed for the native adsorption., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Direct catalytic transformation of xylan-type hemicelluloses to furfural in the aqueous system and the biphasic system were comparatively investigated under mild conditions. Screening of several promising chlorides for conversion of beech xylan in the aqueous system revealed the Lewis acid SnCl4 was the most effective catalyst. Comparing to the single aqueous system, the bio-based 2-methyltetrahydrofuran (2-MTHF)/H2O biphasic system was more conducive to the synthesis of furfural, in which the highest furfural yield of 78.1% was achieved by using SnCl4 as catalysts under the optimized reaction conditions (150°C, 120 min). Additionally, the influences of xylan-type hemicelluloses with different chemical and structural features from beech, corncob and bagasse on the furfural production were studied. It was found that furfural yield to some extent was determined by the xylose content in hemicelluloses and also had relationships with the molecular weight of hemicelluloses and the degree of crystallization., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The conversion of xylose, water-insoluble hemicelluloses (WIH) and water-soluble fraction (WSF) of corncob to furfural was performed using montmorillonite with tin ions (Sn-MMT) containing double acid sites as a solid acid catalyst. The co-existence of Lewis acids and Brønsted acids in Sn-MMT was shown to improve the furfural yield and selectivity. 76.79% furfural yield and 82.45% furfural selectivity were obtained from xylose using Sn-MMT as a catalyst in a biphasic system with 2-s-butylphenol (SBP) as the organic extracting layer and dimethyl sulfoxide (DMSO) as the co-solvent in contact with an aqueous phase saturated with NaCl (SBP/NaCl-DMSO) at 180°C for 30min. Furthermore, Sn-MMT also demonstrated the excellent catalytic performance in the conversion of pentose-rich materials of corncob and 39.56% and 54.15% furfural yields can be directly obtained from WIH and WSF in the SBP/NaCl-DMSO system, respectively., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

This study aimed to produce furfural from waste aqueous hemicellulose solution of a hardwood kraft-based dissolving pulp production processing in a green method. The maximum furfural yield of 82.4% and the xylose conversion of 96.8% were achieved at 463K, 1.0g ZSM-5, 1.05g NaCl and organic solvent-to-aqueous phase ratio of 30:15 (V/V) for 3h. The furfural yield was just 51.5% when the same concentration of pure xylose solution was used. Under the optimized condition, furfural yield was still up to 67.1% even after the fifth reused of catalyst. Catalyst recycling study showed that ZSM-5 has a certain stability and can be efficiently reused., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Stimulus-responsive hydrogels, which can undergo significant physicochemical changes in response to various physical or chemical stimuli, have drawn wide attention in many fields. In this study, novel photoresponsive hydrogels prepared by free radical copolymerization of xylan-type hemicellulose methacrylate with 4-[(4-acryloyloxyphenyl)azo]benzoic acid (AOPAB) were investigated, which showed multiresponsive behaviors to pH, water/ethanol alternating solutions, and light. The swelling ratios of the prepared hydrogels in distilled water decreased from 9.8 to 2.2 g/g with AOPAB content increase from 2% to 16%. The hydrogel displayed rapid swelling and deswelling performance in water and ethanol alternating solutions. Additionally, under UV irradiation the trans-conformation of azobenzene in the hydrogel would generally convert into the cis-conformation and resulted in the hydrophilic/hydrophobic balance variation of the hydrogel. Therefore, the hydrogel loaded with vitamin B12 (VB12) showed a higher drug cumulative release rate under UV irradiation than that without UV irradiation.

In this study, an environmental-friendly hydrothermal pretreatment of Eucalyptus fiber followed with alkali post-treatment was developed to produce bioethanol efficiently. This biorefinery process allowed all major components of biomass being converted into high value-added products. The chemical and structural features of the residual hemicelluloses isolated with alkali from the hydrothermal pretreated Eucalyptus fiber, were comparatively investigated. Sugar and spectral analyses indicated that the hemicelluloses were mainly composed of glucuronoxylans, and especially hemicelluloses prepared at higher temperature (180°C) contained higher contents of glucomannans and α-glucan. Hydrothermal pretreatment resulted in a significant hydrolysis of the glycosidic linkages in xylan backbone, and thus the molecular weight of the hemicelluloses was significantly reduced from 56,520 to 7780g/mol with the increase of temperature. This suggested that a combination of hydrothermal pretreatment at low temperatures (100-140°C) and alkali post-treatment was an effective technique for isolating of hemicelluloses from Eucalyptus fiber., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Hemicelluloses from sugarcane bagasse were subjected to microwave-assisted acid hydrolysis at mild temperature to produce xylooligosaccharides (XOS). The hydrolysis was performed with dilute H2SO4 at 90°C and the influence of acid concentration (0.1-0.3M) and reaction time (20-40min) on the XOS production was ascertained with response surface methodology based on central composite design. The fitted models of XOS and xylose yields were in good agreement with the experimental results. Compared to hydrolysis time, acid concentration was a more significant coefficient in the production of XOS. A well-defined degree of polymerisation of XOS and the monomer in the hydrolysates were quantified. No sugar-degraded byproduct was detected. The maximum XOS yield of 290.2mgg(-1) was achieved by hydrolysis with 0.24M H2SO4 for 31min. The results indicated that the yields of xylose and the byproducts can be controlled by the acid concentration and reaction time in microwave-assisted acid hydrolysis., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The aim of this study was to evaluate the influence of mild alkaline pre-extraction on the hemicelluloses removal of rice straw. In addition, the performance of cellulose nanofibers (CNFs) addition on some physico-mechanical properties obtained from extracted and un-extracted (control) samples were investigated. An optimum compromise was found as operating conditions (10% soda, 50°C, and 90min) that provided moderate hemicelluloses removal (48.1%). The residual extracted rice straw particles were subjected to soda-anthraquinone pulping at 160°C for 30-60min with 6 to 18% active alkali charge. Compared with the control samples, the screened yield and Kappa number for extracted pulps decreased slightly. Extracted samples showed better air resistance compared with the un-extracted (control) pulps. However, pre-extraction was found to negatively impact on some mechanical properties such as decrease in burst and tensile indices while addition of CNFs and refining of fibers could improve the strength properties considerably. In general, the addition of CNFs in any concentrations considerably enhanced tensile and burst indices of the sheets in extracted and un-extracted conditions, compared with the unfilled ones. The improvement in mechanical properties was considered one of the key benefits brought by CNFs reinforcement. On the other hand, the stretch properties of the beaten pulps are higher than those of control samples. SEM observations showed that CNFs were deposited on the voids between the rice straw fibers., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Polysaccharide nanocrystals with a rodlike shape but with different dimensions and specific surface area were prepared from cotton and capim dourado cellulose, and with a plateletlike morphology from waxy maize starch granules. The rheological behavior of aqueous solutions of poly(ethylene oxide) (PEO) with different molecular weights when adding these nanoparticles was investigated evidencing specific interactions between PEO chains and nanocrystals. Because PEO also bears hydrophobic moieties, it was employed as a compatibilizing agent for the melt processing of polymer nanocomposites. The freeze-dried mixtures were used to prepare nanocomposite materials with a low density polyethylene matrix by extrusion. The thermal and mechanical behavior of ensuing nanocomposites was studied.

This work described the morphologic changes of corn stalk and the structural characterization of its hemicelluloses dissolved in yellow liquor at different cooking stages. The results showed that active oxygen cooking process was an efficient method to depolymerize the corn stalk into cellulose, hemicelluloses, and lignin as a pretreatment of biomass conversion. This cooking process can also be divided into three phases: bulk delignification, extended delignification, and residual delignification. During the heating-up period 57.67% of hemicelluloses and 62.31% of lignin were removed from the raw material. However, only 15% of hemicelluloses and 23.21% of lignin were removed during at temperature' period. The hemicelluloses from the corn stalk and yellow liquor were composed of (1→4)-β-D-xylopyranose backbones substituted with α-l-arabinofuranosyl, 4-O-methyl-α-D-glucuronic acid, and some methoxyl residues. The backbones of hemicelluloses were gradually cleaved during the cooking process. The acetyl groups substituted with xylopyranosyl residues were completely cleaved during the cooking process., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Hemicelluloses were extracted from holocellulose of bamboo by alkaline treatment. The phosphorylated poly(vinyl alcohol) (P-PVA) samples with various substitution degrees were prepared through the esterification of PVA and phosphoric acid. A series of hydrogels of semi-interpenetrating polymeric networks (semi-IPN) composed of hemicelluloses-g-poly(acrylic acid) (HM-g-PAA) and the phosphorylated poly(vinyl alcohol) (P-PVA) were prepared by radical polymerization using potassium persulphate (KPS) as initiator. The HM-g-PAA networks were crosslinked by N,N-methylenebisacrylamide (MBA) as a crosslinking agent in the presence of linear P-PVA. FT-IR results confirmed that the hydrogels comprised a porous crosslink structure of P-PVA and HM with side chains that carried carboxylate and phosphorylate groups. SEM observations indicated that the incorporation of P-PVA induced highly porous structure, and P-PVA was uniformly dispersed in the polymeric network. The interior network structures of the semi-IPN matrix became more porous with increasing P-PVA. The TGA results showed that the thermo-decomposing temperature and thermal stability were increased effectively for intruding the chain of P-PVA. The maximum equilibrium swelling ratio of hydrogels in distilled water and 0.9 wt% sodium chloride solutions was up to 1085 g g(-1) and 87 g g(-1), respectively. The compressive strength increased with increasing the MBA/HM and P-PVA/HM ratios, and decreased with the increment of AA/HM ratio., (Copyright © 2014 Elsevier B.V. All rights reserved.)

This work investigated the feasibility of recovering and concentrating sugars and acetic acid (HAc) from prehydrolysis liquor (PHL) of the kraft-based dissolving pulp process prior to fermentation of hemicellulosic sugars, by the combination of activated carbon adsorption, nanofiltration (NF) and reverse osmosis (RO) processes. To reduce the fouling PHL was subjected to adsorption on activated carbon, then the treated PHL (TPHL) passed through a nanofiltration (NF DK) membrane to retain the sugars, and the permeate of acetic acid rich solution was passed through a reverse osmosis membrane (RO SG). It was found that for NF process sugars were concentrated from 48 to 227g/L at a volume reduction factor (VRF) of 5 while 80 to 90% of acetic acid was permeated. For the reverse osmosis process, 68% of acetic acid retention was achieved at pH 4.3 and 500 psi pressure and the HAc concentration increased from 10 to 50g/L., (Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.)

Galactose units of spruce galactoglucomannan (GGM), guar galactomannan (GM), and tamarind (galacto)xyloglucan (XG) were selectively allylated. Firstly aldehyde functionalities were formed at the C-6 position via enzymatic oxidation by galactose oxidase. The formed aldehydes were further derivatized by an indium mediated Barbier-Grignard type reaction, resulting in the formation of homoallylic alcohols. In addition to allylic halides, the same reaction procedure was also applicable for GGM, when using propargyl bromide as halide. All reaction steps were done in water, thus the polysaccharides were modified in a one-pot reaction. The formation of the allylated, or propargylated, product was identified by MALDI-TOF-MS. All polysaccharide products were isolated and further characterized by GC-MS or NMR spectroscopy. By this chemo-enzymatic process, we have demonstrated a novel method for derivatization of GGM and other galactose-containing polysaccharides. The derivatized polysaccharides are potential platforms for further functionalizations., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

In order to establish the correlation between hemicelluloses removal and bioconversion efficiency of cellulose, fractionation process with increasing NaOH concentration selectively released the hemicellulosic polymers with increasing molecular weight and decreasing degree of substitution. Not only the initial hydrolysis rates also the concentrations of glucose and ethanol were significantly enhanced from 5.93 and 8.39 g/L to the range of 8.67-9.60 g/L and 11.53-13.71 g/L after alkaline treatment, respectively. However, the maximum conversions of cellulose to glucose (61.9%) and ethanol (64.6%) were achieved as 33.0% hemicelluloses was still remained. Excluding the negligible effect on the crystal transformation of cellulose, the improvement of bioconversion efficiency was resulted from the synergetical effects of surface exposure, multi-layers collapse and the hydrophilic property of the cellulosic substrate. It is critical task to balance these factors by the partial removal of hemicellulosic component, not complete., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The effect of five different wood particle size fractions between 0.5 and 12.5 mm on hot-water extraction of acetylated water-soluble hemicelluloses from spruce wood with a batch extraction setup at 170 °C was investigated. Extraction kinetics, with regard to particle size, was also studied. The purpose was to intensify the hemicellulose extraction for high molar mass hemicelluloses at high yield and purity. About 30% of the wood was dissolved and basically all the hemicelluloses could be extracted. The average molar masses of the extracted hemicelluloses decreased rapidly during the first 10 min of the extraction, but were not much affected by the difference in wood particle sizes. Smaller particles resulted in higher extraction rates. The reaction order was established to be of pseudo-first order for particles above 2mm and 1.5st order for particles smaller than 2mm. The effective diffusion coefficient was determined to be 9.11×10(-10) m(2)/s., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The potential of near infrared spectroscopy in conjunction with partial least squares regression to predict chemical composition of various wood species including softwoods and hardwoods was examined. Hot-water-soluble extractive, pentosan and cellulose content of various wood species were predicted with high coefficient of determination between the predicted and measured values, the ratio of performance to deviation, range error ratio, and low root mean square error of cross validation for cross-validation and root mean square error of prediction for test set validation. Hot-water-soluble extractive and cellulose content models were only suitable for quality control analysis, but pentosan content model had an excellent fit with the data and could be used in any application. All the results indicate that Fourier transform near infrared spectroscopy could be applied to predict the chemical composition of various wood species., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Two methods for separation of polymeric galactoglucomannans (GGMs) from a hot-water extract of spruce wood, i.e., membrane filtration and precipitation in ethanol-water, were compared. Filtration through a series of membranes with different pore sizes separated GGMs of different molar masses, from polymers to oligomers. Only polysaccharides were precipitated in ethanol-water. With the optimal water content of 5-15%, the precipitated amount was about 6% on wood basis. The average molar mass of the precipitated polysaccharides was 10-12kDa with a molar mass range of 4-20kDa. GGMs comprised about 80% of the precipitated hemicelluloses. Other precipitated polysaccharides were mainly arabinoglucuronoxylans and pectins (rhamnogalacturonans). Analysis of a lignin-free, ethanol-precipitated GGM preparation by (13)C NMR spectroscopy verified that it was structurally almost identical with a GGM-rich ethanol precipitate obtained from spruce wood by extraction at much milder conditions, 90°C for 60min., (Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.)

To test a biorefinery concept, the non-wood biomass of Eulaliopsis binata was treated with dilute acid prior to dissolving pulp production at 160 °C for 30 min. The pretreatment liquor (PL) contained 42.04 g/L sugars, of which 81.46% was xylose and only 2.91% was glucose. Furfural and hydroxymethylfurfural in PL were 0.37% and 0.06%, respectively. Chemical or enzymatic hydrolysis of carbohydrates could be omitted when producing bioethanol with PL because 87.32% of the total sugars were in the form of monosaccharides. Membrane filtration with a molecular-weight cut-off of 100 Da was employed to concentrate the sugars and a concentration of 170.49 g/L was achieved. A method of zero release of the PL is proposed, which consists of ethanol production from the concentrated PL and recycling the permeate stream into the pretreatment process., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

This work describes the structural changes of bagasse hemicelluloses during the cooking process involving active oxygen (O(2) and H(2)O(2)) and solid alkali (MgO). The hemicelluloses obtained from the bagasse raw material, pulp, and yellow liquor were analyzed by high-performance anion-exchange chromatography (HPAEC), gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FT-IR), and (1)H-(13)C 2D hetero-nuclear single quantum coherence spectroscopy (HSQC). The results revealed that the structure of the bagasse hemicelluloses was L-arabino-(4-O-methylglucurono)-D-xylan. Some sugar units in hemicelluloses were oxidized under the cooking conditions. Additionally, the backbones and the ester linkages of hemicelluloses were heavily cleaved during the cooking process., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Concentrated dilute acid hydrolysate was obtained from hot water extracts of Acer saccharum (sugar maple) and was fermented to ethanol by Pichia stipitis in a 1.3-L-benchtop bioreactor. The conditions under which the highest ethanol yield was achieved were when the air flow rate was set to 100 cm(3) and the agitation rate was set to 150 rpm resulting in an overall mass transfer coefficient (K(L)a) of 0.108 min(-1). A maximum ethanol concentration of 29.7 g/L was achieved after 120 h of fermentation; however, after 90 h of fermentation, the ethanol concentration was only slightly lower at 29.1 g/L with a yield of 0.39 g ethanol per gram of sugar consumed. Using the same air flow rate and adjusting the agitation rate resulted in lower ethanol yields of 0.25 g/g at 50 rpm and 0.30 g/g at 300 rpm. The time it takes to reach the maximum ethanol concentration was also affected by the agitation rate. The ethanol concentration continued to increase even after 130 h of fermentation when the agitation rate was set at 50 rpm, whereas the maximum ethanol concentration was reached after only 68.5 h at 300 rpm.

The prehydrolysis liquor (PHL) of the kraft-based dissolving pulp production process contains various amounts of hemicelluloses that can be utilized in the production of value-added products. In this work, a new process was proposed for removing the inhibitors of PHL via employing a flocculation concept to facilitate the utilization of hemicelluloses. Lignin, lignocelluloses/cationic polymer complexes, and possibly ethanol are the main products of this process. This process has been experimentally evaluated with an industrially produced PHL and cationic polymers. The results showed that 16% of lignin, 19% of acetic acid, 43% of furfural, and insignificant amount of sugars were removed from PHL via pretreating PHL with acid and lime at pH 7. Furthermore, by adding 0.4-0.5 mg g(-1) polydiallyldimethylammonium chloride (PDADMAC) or chitosan to the pretreated PHL, 12-14% acetic acid, 40-50% furfural, 5-6% monomeric sugars, and 25% oligomeric sugars were removed from the PHL. The complexes made from these components may be applied as organic fillers in various industries. Alternatively, by adding 1.2 or 1.4 mg g(-1) PDADMAC or chitosan to the pretreated PHL, 30 or 35% of lignin was removed, respectively, which induced complexes that could be used as a fuel source. The composition of the complexes formed was also determined in this work., (Copyright © 2012 American Institute of Chemical Engineers (AIChE).)

Intensive exploration and research in the past few decades on polysaccharide nanocrystals, the highly crystalline nanoscale materials derived from natural resources, mainly focused originally on their use as a reinforcing nanophase in nanocomposites. However, these investigations have led to the emergence of more diverse potential applications exploiting the functionality of these nanomaterials. Based on the construction strategies of functional nanomaterials, this article critically and comprehensively reviews the emerging polysaccharide nanocrystal-based functional nanomaterials with special applications, such as biomedical materials, biomimetic optical nanomaterials, bio-inspired mechanically adaptive nanomaterials, permselective nanostructured membranes, template for synthesizing inorganic nanoparticles, polymer electrolytes, emulsion nano-stabilizer and decontamination of organic pollutants. We focus on the preparation, unique properties and performances of the different polysaccharide nanocrystal materials. At the same time, the advantages, physicochemical properties and chemical modifications of polysaccharide nanocrystals are also comparatively discussed in view of materials development. Finally, the perspective and current challenges of polysaccharide nanocrystals in future functional nanomaterials are outlined.

Novel hydrophobic hemicelluloses possessing hydrophobic groups were prepared by the benzylation of wheat straw hemicelluloses with benzyl chloride under the presence of catalyst in an ethanol/water system. In particular, the progress of the benzylation reaction was studied as a function of the volume ratio of ethanol/water from 4:1 to 6:4, the molar ratio of NaOH/anhydroxylose unit in hemicelluloses from 0.6:1 to 1.5:1, the molar ratio of benzyl chloride/anhydroxylose unit in hemicelluloses from 0.5:1 to 2.0:1, reaction temperature 50-80 °C, and reaction time 4-20 h Benzylated hemicelluloses with the low degree of substitution from 0.09 to 0.35 were obtained depending on the experimental conditions. The incorporation of benzyl groups into the backbone of hemicelluloses was confirmed by FT-IR and (13)C NMR spectroscopies. The thermal stability increased after the modification of hemicelluloses due to the introduction of benzyl groups. The introduction of benzyl groups endows hemicelluloses with the hydrophobicity, which could be potentially applied in plastic industries., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

A portion of hemicelluloses and acetic acid can be pre-extracted with dilute sulfuric acid prior to the aspen chemithermomechanical pulp process. The streams collected from the second press-impregnation stage after acid pre-extraction contain a significant amount of acid pre-extracted hemicelluloses. Most of the total sugars obtained from the pressate were xylan, in which xylan was further hydrolyzed to sugar monomers under the acid pre-extraction condition. To fully understand the characteristics of hemicelluloses yielded prior to pulping, the pre-extracted hemicelluloses were separated and characterized by FT-IR, (1)H NMR, and thermogravimetric analysis in this study. Most of the FT-IR bonds from the hemicelluloses agreed well with the other two spectra of birch xylan and CA0050 xylan, except a new absorption at 1734 cm(-1) contributed to acetyl groups. The hemicelluloses obtained from acid pre-extraction began to decompose significantly at about 225 °C, slightly lower in comparison with organosolv and alkaline hemicelluloses reported in the literature.

Xylan-rich hemicelluloses-based hydrogel was developed as a novel porous bioadsorbent by graft co-polymerization of acrylic acid (AA) and xylan-rich hemicelluloses for adsorption of heavy metal ions (Pd(2+), Cd(2+), and Zn(2+)) from aqueous solutions. The chemical structure, the interaction between the hydrogel and metal ions, and the porous structure of xylan-rich hemicelluloses-g-AA hydrogel were revealed by Fourier transform infrared spectroscopy and scanning electron microscopy. The effects of AA and cross-linker dosage, pH value, contacting time, and initial concentration of metal ion on the adsorption capacity were studied. The adsorption equilibrium time was about 60 min from the adsorption kinetics study. The maximum adsorption capacities of Pd(2+), Cd(2+), and Zn(2+) were 859, 495, and 274 mg/g, respectively. Furthermore, xylan-rich hemicelluloses-g-AA hydrogel also exhibited highly efficient regeneration and metal ion recovery efficiency and can be reused without noticeable loss of adsorption capacity for Pd(2+), Cd(2+), and Zn(2+) after quite a number of repeated adsorption/desorption cycles.

In this study, a novel amphoteric macromolecule was synthesized by sequential incorporation of carboxymethyl and quaternary ammonium groups into the backbone of xylan-type hemicelluloses under microwave irradiation. The reaction parameters such as the molar ratio of reagent (NaOH or 3-epoxypropyltrimethylammonium chloride)/anhydroxylose unit in hemicelluloses, the temperature, and the reaction time were investigated to optimize the reaction condition. The maximum degrees of substitution (DS) of carboxymethyl and quaternary ammonium groups under the optimum reaction condition were 0.90 and 0.52, respectively, exhibiting a higher efficiency as compared to the conventional heating method. Moreover, the thermal stability and weight-average molecular weight of amphoteric hemicellulosic derivatives decreased as compared to the native hemicelluloses. The viscosity, elastic modulus, and loss modulus of the amphoteric biomacromolecules increased with the increasing DS of quaternary ammonium groups in aqueous solution due to stronger electrostatic attraction. This study provides an efficient and rapid method to prepare amphoteric biomacromolecules.

Laccases in combination with various chemical compounds have been tested with a view to obtain environmental friendly, high-value paper products from unbleached flax pulp, which is currently being assessed as a raw material for biotechnological innovation. With the aim of better understanding the effects of violuric acid (VA) and p-coumaric acid (PCA) on flax pulp, changes in the chemical composition of the two major fiber types it contains were assessed. Following classification, the initial pulp was split into two fractions according to fiber size, namely: bast (long) fibers and core (short) fibers. Fiber size was found to significantly influence the properties of pulp and it response to various laccase treatments. The laccase-PCA treatment substantially increased kappa number (KN) and color in both fiber fractions, which suggests grafting of the phenolic compound onto fibers. On the other hand, the laccase-VA treatment produced long fibers with a low lignin content (KN = 1.3) and a high brightness (5% points higher than for the control fraction), which testifies to its bleaching efficiency. Both biotreatments produced long fibers containing highly crystalline cellulose and caused HexA removal from global and short fibers. On the other hand, the laccase treatments caused no morphological changes in the fibers, the integrity of which was largely preserved. As shown here, laccase acts as polymerization agent with PCA and as delignification agent with VA; also, the two enzymes systems act differently on bast and core fibers., (Copyright © 2011 Wiley Periodicals, Inc.)

Ground spruce wood was extracted with water at 170 °C at four different pH levels (3.8, 4.0, 4.2 and 4.4) achieved by using phthalate buffers. Static batch extractions were carried out in an accelerated solvent extractor (ASE-300). The extracted non-cellulosic carbohydrates, predominantly galactoglucomannans (GGMs), were characterised mainly by sugar unit analysis and molar mass determination. Compared to extraction with plain water, extractions with phthalate buffer solutions gave similar yields of non-cellulosic carbohydrates, but gave up to 70% less monosaccharides, and consequently higher molar masses of extracted GGMs. Moreover, at these pH levels, the hydrolysis of acetyl groups were decreased by 40% compared to extraction with plain water, thus maintaining the water solubility of GGMs. It is concluded that hot water extraction of hemicelluloses in high-molar-mass form (average Mw about 10 kDa) from wood in good yields (8% of wood) demands appropriate control of pH, to a level of about 4., (Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.)

Hemicelluloses in industrially produced pre-hydrolysis liquor (PHL) were precipitated with ethanol. These PHL-derived hemicelluloses (PHL-EH) and a commercial, pure birch wood xylan sample (powder form) (BWX) were bleached using chlorine dioxide (D(0) and D(1)) and hydrogen peroxide (Ep) in the D(0)EpD(1) sequence, and the chemical compositions, molecular weights and charge densities of the treated samples were assessed. When applied to high-yield pulp (HYP) at 50 mg/g, 26 and 20 mg/g of the bleached PHL-EH and BWX, respectively, were adsorbed without significantly affecting paper properties. These results suggest that semi-bleached hemicelluloses could be used to increase the basis weight of paper products. Furthermore, an integrated process was proposed that converts the kraft-based dissolving pulp production process into a biorefinery unit with dissolving pulp, bleached hemicelluloses and lignin as main products., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Interest in xylan-rich hemicelluloses (XH) film is growing, and efforts have been made to prepare XH films with improved mechanical properties. This work described an effective approach to produce nanocomposite films with enhanced mechanical properties by incorporation of cellulose nanofibers (CNFs) into XH. Aqueous dispersions of XH (64-75 wt %), sorbitol (16-25 wt %), and CNF (0-20 wt %) were cast at a temperature of 23 °C and 50% relative humidity. The surface morphology of the films was revealed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The thermal properties and crystal structure of the films were evaluated by thermal analysis (TG) and X-ray diffraction (XRD). The surface of XH films with and without CNF was composed primarily of nanonodules, and CNFs were embedded in the XH matrix. Freeze-dried XH powder was amorphous, whereas the films with and without CNF showed a distinct peak at around 2θ = 18°, which suggested that XH molecules aggregated or reordered in the casting solution or during water evaporation. Furthermore, the nanocomposite films had improved thermal stability. XH film with 25 wt % plasticizer (sorbitol, based on dry XH weight) showed poor mechanical properties, whereas incorporation of CNF (5-20 wt %, based on the total dry mixture) into the film resulted in enhanced mechanical properties due to the high aspect ratio and mechanical strength of CNF and strong interactions between CNF and XH matrix. This effective method makes it possible to produce hemicellulose-based biomaterials of high quality.

Lignocellulose materials are potentially valuable resources for transformation into biofuels and bioproducts. However, their complicated structures make it difficult to fractionate them into cellulose, hemicelluloses, and lignin, which limits their utilization and economical conversion into value-added products. This study proposes a novel and feasible fractionation method based on complete dissolution of bagasse in 1-butyl-3-methylimidazolium chloride ([C(4)mim]Cl) followed by precipitation in acetone/water (9:1, v/v) and extraction with 3% NaOH solution. The ionic liquid [C(4)mim]Cl was easily recycled after concentration and treatment with acetonitrile. (1)H NMR analysis confirmed that there was no obvious difference between the recycled [C(4)mim]Cl and fresh material. Bagasse was fractionated with this method to 36.78% cellulose, 26.04% hemicelluloses, and 10.51% lignin, accounting for 47.17 and 33.85% of the original polysaccharides and 54.62% of the original lignin, respectively. The physicochemical properties of the isolated fractions were characterized by chemical analysis, high-performance anion exchange chromatography (HPAEC), gel permeation chromatography (GPC), Fourier transform infrared (FT-IR), and (1)H and 2D (13)C-(1)H correlation (HSQC) nuclear magnetic resonance spectroscopy. The results showed that the acetone-soluble lignin and alkaline lignin fractions had structures similar to those of milled wood lignin (MWL). The easy extraction of the noncellulose components from homogeneous bagasse solution and amorphous regenerated materials resulted in the relatively high purity of cellulosic fraction (>92%). The hemicellulosic fraction was mainly 4-O-methyl-D-glucuronoxylans with some α-L-arabinofuranosyl units substituted at C-2 and C-3.

Exploitation of biomaterials derived from renewable resources is an important approach to address environmental and resource problems in the world today. In this paper, novel ionic hydrogels based on xylan-rich hemicelluloses were prepared by free radical graft copolymerization of acrylic acid (AA) and xylan-rich hemicelluloses (XH) by using N,N-methylene-bis(acrylamide) (MBA) as cross-linker and ammonium persulfate/N,N,N',N'-tetramethylethylenediamine (APS/TMEDA) as redox initiator system. The network characteristics of the ionic hydrogels were investigated by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM), as well as by determination of mechanical properties, swelling, and stimuli responses to pH, salts, and organic solvents. The results showed that an increase in the MBA/XH or AA/XH ratio resulted in higher cross-linking density of the network and thus decreased the swelling ratio. Expansion of the network hydrogels took place at high pH, whereas shrinkage occurred at low pH or in salt solutions as well as in organic solvents. The ionic hydrogels had high water adsorption capacity and showed rapid and multiple responses to pH, ions, and organic solvents, which may allow their use in several areas such as adsorption, separation, and drug release systems.

Starch from bamboo Phyllostachys bambusoides f. shouzhu Yi evaluated by means of solid-state 13C CP/MAS NMR and X-ray diffraction showed a typical B-type pattern with a very low degree of crystallinity (10.9%). In addition to starch, alkali-soluble hemicelluloses were further fractionated by graded precipitation at ethanol concentrations of 0 (HA), 15, 30, 45, 60, and 75% (v/v). Chemical composition and structural features of the six hemicellulosic subfractions were investigated by a combination of sugar analysis, GPC, FT-IR, GC-MS, 1D (1H and 13C) and 2D (HSQC) NMR spectra, and thermal analysis. The results showed that the bamboo hemicelluloses were O-acetylated 4-O-methyl-glucuronoarabinoxylans (GAX) consisting of a linear (1→4)-β-D-xylopyranosyl backbone decorated with branches at O-3 of α-L-arabinofuranosyl (5-12 mol%) or at O-2 of 4-O-methylglucuronic acid units and acetyl groups (0.8-11 mol%). The molecular weights of these polysaccharides ranged between 13400 and 67500 g/mol, and the molar ratios of A/X and G/X increased with ascending ethanol concentrations. Moreover, xylo-oligosaccharides (XOS) with DP 1-6 were produced by enzymatic hydrolysis of hemicelluloses and the total yields of XOS were range of 21.5 to 40.6%. The structure-property relationships were also established in order to improve enzyme accessibility.

In this article, a facile, rapid, and efficient method was developed for the preparation of carboxymethyl hemicelluloses using microwave-induced organic reaction enhancement chemistry. The influences of the factors including reaction time, temperature, and the amount of sodium monochloroacetate and sodium hydroxide on the degree of substitution (DS) of the products were investigated. The rheological properties and the chemical structure of the resulting polymers were also studied. It was found that microwave irradiation could significantly promote the chemical reaction efficiency and accelerate the carboxymethylation of hemicelluloses with sodium monochloroacetate. Therefore, carboxymethyl hemicelluloses with higher DS of 1.02 could be obtained in much shorter time scales as compared to the conventional heating method. Results from rheological analysis indicated that carboxymethyl hemicellulose solutions exhibited shear-thinning behavior in the range of shear rates tested and showed lower viscosity and modulus in comparison with those of the native hemicelluloses due to lower molecular weight and the role of carboxymethyl groups in reducing the entanglements between hemicelluloses chains.

In this study the influence of the insoluble solids in nano-filtrated sugar maple hemicellulosic hydrolysate on the metabolic behavior of Pichia stiptis was investigated. The particle properties of hemicellulosic hydrolysate were analyzed. Phosphoric acid and ammonium (PA) were applied to remove the particles. The metabolic behavior and growth property of P. stipitis in particle--removed hydrolysate was measured. Results demonstrated that the average particle size and zeta potential of the untreated hydrolysate were 2266.9±78.2 nm and -6.09±0.49 mV. Xylose consumption and ethanol production rate were significantly decreased when particle content is greater than 1.63 g/L. Because the majority of particles (34 g/L) were removed from hydrolysates by phosphoric acid and ammonium treatment, the fermentability of the hydrolysate was significantly improved. These results indicated particles play an important role in hydrolysate inhibition effect., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

In this paper, we proposed a new modification for an ethanol-based pulping process, which would consist of the pre-hydrolysis (pre-extraction) of wood chips for removing hemicelluloses; the ethanol extraction of pre-hydrolyzed wood chips for removing lignin; and the post purification of cellulose, leading to the production of pure cellulose. We also experimentally evaluated the separation of hemicelluloses from the pre-hydrolysis liquor (PHL) obtained from a pulp mill. To remove lignin from the PHL, it was acidified to a pH of 2, which resulted in 47% lignin precipitation. The lignin separation from the acidified PHL was further improved via adding polyethylene oxide and poly aluminum chloride or adding ethyl acetate. To recover the hemicelluloses from the acidified PHL, ethanol was added to the acidified PHL with a volumetric ratio of 4 to 1. The isolated lignin and hemicelluloses were characterized by a Fourier transform infrared spectroscopy (FTIR) and a gas permeation chromatography (GPC)., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Generation of bioenergy, new functional polymers, or chemicals and biomaterials from hemicelluloses are important uses for biomass. In this paper, a novel functional biopolymer with carbon-carbon double bond and carboxyl groups was prepared by a homogeneous esterification of xylan-rich hemicelluloses (XH) with maleic anhydride in 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) ionic liquid using LiOH as catalyst. The biopolymers with degrees of substitution (DS) between 0.095 and 0.75 were accessible in a completely homogeneous system by changing reaction temperature, reaction time, the dosage of catalyst, and the molar ratio of maleic anhydride to anhydroxylose unit in XH. Results obtained from FT-IR and (13)C NMR spectroscopies confirmed the structure of hemicellulosic derivatives with carbon-carbon double bond and carboxyl groups, implying an efficient method to prepare a novel and important functional biopolymer for biomaterials.

Aqueous suspensions of polysaccharide (cellulose, chitin or starch) nanocrystals can be prepared by acid hydrolysis of biomass. The main problem with their practical use is related to the homogeneous dispersion of these nanoparticles within a polymeric matrix. Water is the preferred processing medium. A new and interesting way for the processing of polysaccharide nanocrystals-based nanocomposites is their transformation into a co-continuous material through long chain surface chemical modification. It involves the surface chemical modification of the nanoparticles based on the use of grafting agents bearing a reactive end group and a long compatibilizing tail.

The dewaxed cell walls of Populus gansuensis were delignified with NaClO(2) and then sequentially extracted with 0.25, 0.5, and 1.0 M KOH under a solid to liquid ratio of 1: 25 (g mL(-1)) at 25 degrees C for 10 h. The successive treatments together resulted in the dissolution of 83.7% of original hemicelluloses. The solubilized hemicellulosic fractions were further fractionated into six hemicellulosic subfractions by an iodine-complex precipitation technique. Their chemical and physical characteristics were determined by HPAEC, GPC, FT-IR, and (1)H and (13)C NMR spectroscopy. Neutral sugar composition and molecular weight analysis showed that, for each extract, the hemicellulosic subfractions that precipitated with aqueous potassium iodide-iodine had lower overall uronic acid/xylose (Uro/Xyl) ratios and higher molecular weights (M(w)) than those remaining in the solution. FT-IR, (1)H, and (13)C NMR spectroscopy analysis indicated that the alkali-soluble hemicelluloses of Populus gansuensis had a structure composed of the (1 --> 4)-linked beta-D-xylopyranosyl backbone with 4-O-methyl-alpha-D-glucuronic acid attached to O-2 of the xylose residues.

The two hemicellulosic fractions were subsequentially extracted with 5% and 8% NaOH aqueous solution at a solid to liquid ratio of 1:25 (g mL(-1)) at 50 degrees C for 3 h from the water, 1 and 3% NaOH-treated sugar cane bagasse, and subfractionated into six preparations by a graded ethanol precipitation method at concentrations of 15%, 30% and 60% (v/v). Sugar composition and molecular weight analysis showed that, with an increasing concentration of ethanol, hemicellulosic subfractions with both higher Ara/Xyl ratios and higher molecular weights were obtained. In other words, with an increasing ethanol concentration from 15% to 60%, the Ara/Xyl ratios increased from 0.043 in H(1) to 0.088 in H(3) and from 0.040 in H(4) to 0.088 in H(6), and the weight-average molecular weights of hemicellulosic subfractions increased from 42 430 (H(1)) to 85 510 (H(3)) g mol(-1) and from 46 130 (H(4)) to 64 070 (H(6)) g mol(-1), respectively. The results obtained by the analysis of Fourier transform infrared, sugar composition, and (1)H and (13)C nuclear magnetic spectroscopy showed that the alkali-soluble hemicelluloses had a backbone of xylose residues with a beta-(1-->4)-linkage and were branched mainly through arabinofuranosyl units at C-2 and/or C-3 of the main chain, whereas the differences may occur in the distribution of branches along the xylan backbone.

The sequential treatment of dewaxed sugarcane bagasse with H(2)O and 1 and 3% NaOH at a solid to liquid ratio of 1:25 (g mL(-1)) at 50 degrees C for 3 h yielded 74.9% of the original hemicelluloses. Each of the hemicellulosic fractions was successively subfractionated by graded precipitation at ethanol concentrations of 15, 30, and 60% (v/v). Chemical composition, physicochemical properties, and structures of eight precipitated hemicellulosic fractions were elucidated by a combination of sugar analysis, nitrobenzene oxidation of bound lignin, molecular determination, Fourier transform infrared (FT-IR), (1)H and (13)C nuclear magnetic spectroscopies, and thermal analysis. The results showed that the sequential treatments and graded precipitations were very effective on the fractionation of hemicelluloses from bagasse. Comparison of these hemicelluloses indicated that the smaller sized and more branched hemicelluloses were extracted by the hot water treatment; they are rich in glucose, probably originating from alpha-glucan and pectic polysaccharides. The larger molecular size and more linear hemicelluloses were dissolved by the alkali treatment; they are rich in xylose, principally resulting from l-arabino-(4-O-methylglucurono)-d-xylans. In addition, noticeable differences in the chemical composition and molecular weights were observed among the graded hemicellulosic subfractions from the water-soluble and alkali-soluble hemicelluloses. The Ara/Xyl ratio increased with the increment of ethanol concentration from 15 to 60%, and the arabinoxylans with higher Ara/Xyl ratios had higher molecular weights. There were no significant differences in the structural features of the precipitated hemicellulosic subfractions, which are mainly constituted of l-arabino-(4-O-methyl-d-glucurono)xylan, whereas the difference may occur in the distribution of branches along the xylan backbone.