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Abstract: 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 0.9wt% sodium chloride solutions was up to 1085gg−1 and 87gg−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 &y& Elsevier]

Abstract: Hemicelluloses are types of plant cell wall polysaccharides, and the world''s second most abundant renewable polymers after cellulose in lignocellulosic materials. They represent a type of hetero-polysaccharide with complex structure containing glucose, xylose, mannose, galactose, arabinose, rhamnose, glucuronic acid, and galacturonic acid in various amounts, depending on the source. Hemicelluloses are usually bonded to other cell-wall components such as cellulose, cell-wall proteins, lignin, and phenolic compounds by covalent and hydrogen bonds, and by ionic and hydrophobic interactions. This paper provides a review on hemicelluloses from lignocellulosic materials, especially in regard to their isolation and purification methods, and bioconversion. Current isolation and purification strategies are summarized, including: alkali peroxide extraction, organic solvent extraction, steam explosion, ultrasound-assisted extraction, microwave-assisted extraction, column chromatography, and membrane separation. In addition, the bioconversion of hemicelluloses including pretreatment, enzymatic hydrolysis, and fermentation are discussed. [Copyright &y& Elsevier]

Abstract: Water and alkali-soluble polysaccharides, isolated by sequential extractions with distilled water, 0.5% and 1% NaOH, 60% ethanol containing 1% NaOH, and 3%, 5% and 8% NaOH, were prepared at 60°C for 3h from dewaxed bamboo Phyllostachys incarnata Wen. The yields of the seven fractions together accounted for 80.1% of total available hemicellulosic polysaccharides. Sugar composition studies showed that the water-soluble polysaccharides consisted mainly of glucose units, while xylose, arabinose and glucuronic acid were the major sugars in alkali-soluble hemicelluloses. Moreover, the molecular weights of these polymers varied between 3760 and 36,000g/mol as revealed by GPC. Furthermore, the structure of the hemicellulosic fraction extracted with 3% NaOH was determined by 1H and 13C NMR spectroscopy along with 2D HSQC. It was found that the bamboo hemicelluloses were O-acetyl-(4-O-methylglucurono)-arabinoxylans, and the structural element could be identified as below: 1,4-β-D-[2-O-Ac][2,3-di-O-Ac][4-O-Me-α-D-GlcpA-(1→2)][α-L-Araf-(1→2)(1→3)]-xylp. [Copyright &y& Elsevier]

Abstract: Sequential treatments of dewaxed Caragana korshinskii with dimethyl sulfoxide and dioxane-triethylamine (9:1, v/v) at 80°C for 5h, saturated barium hydroxide, 1M potassium hydroxide and 1M sodium hydroxide at 50°C for 5h, and 3M potassium hydroxide at 50°C for 4h released 9.9%, 12.1%, 19.2%, 27.7%, 13.2% and 12.9% of the original hemicelluloses, respectively. The DMSO-soluble and four alkali-soluble hemicellulosic fractions contained higher amounts of xylose (73.6–91.5%), but were lower in rhamnose (0.5–2.3%) and arabinose (2.8–17.6%) than dioxane-triethylamine (9:1, v/v) soluble hemicellulosic fraction, in which xylose (37.9%), rhamnose (25.9%) and arabinose (25.0%) were the major sugar components. In comparison, the molecular-weight analysis showed that hemicelluloses were substantially degraded with a value of 13,930gmol−1 under the organic alkaline extraction condition (dioxane-triethylamine, 9:1) used, whereas saturated Ba(OH)2 treatment favored the solubilization of macromolecular hemicelluloses (69,910gmol−1). It is confirmed that the hemicelluloses from C. korshinskii are (1→4)-linked β-d-xylans with l-arabinofuranosyl group attached based on both 1H and 13C NMR spectra. [Copyright &y& Elsevier]

Abstract: Water- and alkali-soluble hemicelluloses isolated from dewaxed sugarcane bagasse were sub-fractionated on DEAE-cellulose-52 chromatography and obtained six hemicellulosic sub-fractions by eluting with water, 0.1M and 0.3M NaCl aqueous solution, respectively. Sugar composition and molecular weight analysis revealed that the lower molecular weight (14,180–43,590gmol−1) and more branches of hemicelluloses could be extracted by the hot water, which are rich in glucose, galactose, and xylose, while the higher molecular weight (75,430–138,170gmol−1) and more linear hemicelluloses were able to be dissolved into 1% NaOH aqueous solution, which are rich in xylose, principally resulting from l-arabino-(4-O-methyl-glucurono)-d-xylans. In addition, it was found that with increasing the concentration of NaCl (aqueous), the hemicellulosic sub-fractions with both higher arabinose to xylose ratio and higher molecular weight were eluted. Based on the FT-IR, sugar composition and 1H and 13C NMR comparative studies, the alkali-soluble hemicellulosic sub-fractions had a classical structure, with a backbone of β-(1→4)-linked xylosyl residue substituted with arabinose at C–2 and/or C–3 of main chain, whereas the difference may occur in the distribution of branches along the xylan backbone. [Copyright &y& Elsevier]

Abstract: In this work the application of different hemicellulosic derivatives including different degrees of substitution (DS) cationic hemicelluloses and carboxymethyl hemicelluloses in sulfate kraft pulp were investigated in detail. It was found that cationic hemicelluloses and carboxymethyl hemicelluloses could improve the physical properties of hand sheets, while the cooperation of cationic hemicelluloses and carboxymethyl hemicelluloses could enhance sharply the physical properties of hand sheets. When the dosages of cationic hemicelluloses with DS of 0.37 and carboxymethyl hemicelluloses with DS of 0.35 were 1.0% and 1.0% (based on dry pulp weight), respectively, the physical properties of hand sheets was significantly improved, breaking lengthen and tear index of hand sheets increased by 21.1% and 54.6% compared with the control hand sheets without any additives added. The fiber intertexture of the hand sheets was observed by SEM. The results indicated that hemicelluloses could be used as the source for the production of wet-end additives in papermaking, which might represent an important strategy for sustainable use of the agricultural residue. [Copyright &y& Elsevier]

Abstract: Hemicellulose-based hydrophobic biomaterials with degrees of substitution ranging from 0.46 to 1.54 were synthesized under mild conditions in homogeneous media (N,N-dimethylformamide–lithium chloride) by reacting the native wheat straw hemicellulosic polymers with lauroyl chloride using 4-dimethylaminopyridine as a catalyst. Other catalysts such as N-bromosuccinimide, N-methyl pyrrolidine, N-methyl pyrrolidinone, and pyridine were also investigated. Under optimum reaction conditions (2equiv of lauroyl chloride and triethylamine per hydroxyl group, 5% 4-dimethylaminopyridine, 40°C, 35min), a high DS value of 1.54 was obtained. The biomaterials were characterized by FT-IR spectroscopy and 13C NMR spectroscopy as well as by thermal analysis. The results showed that the lauroylation occurred preferably at the C-3 hydroxyl group of β-d-Xylp units in the hemicelluloses, and the thermal stability of the hydrophobic polymers increased by esterification. [Copyright &y& Elsevier]

Abstract: A series of novel water-soluble hemicellulosic derivatives, containing carbamoylethyl and carboxyethyl groups, were heterogeneously synthesized from wheat-straw hemicelluloses with acrylamide (AA) under alkaline conditions. The factors such as reaction temperature, reaction time, molar ratio of catalysis to xylose unit in hemicelluloses and molar ratio of acrylamide to xylose unit in hemicelluloses, were investigated. The average degree of substitution (DS) was calculated by 1H NMR spectroscopy. DS values up to 0.23 in a one-step synthesis of hemicelluloses derivatives were obtained. Under optimum conditions (60°C, NaOH to xylose unit in hemicelluloses molar ratio of 0.8, AA to xylose unit in hemicelluloses molar ratio of 8.0, reaction time of 1h) an expected ratio of carbamoylethyl group to carboxyethyl group of 4.8 in the hemicellulosic derivatives was obtained. The structural features of the hemicellulosic derivatives were characterized by FTIR, NMR spectroscopy, and by elemental analysis. The current work provides a facile method for the synthesis of hemicellulose derivatives with bifunctional groups, which could be used as wet-end additives in the papermaking industry. [Copyright &y& Elsevier]

Wood auto-hydrolysates (WAH) are obtained in the pulping process by the hydrothermal extraction, which contains lots of hemicelluloses and slight lignin. WAH and chitosan (CS) were introduced into this study to construct WAH-based films by the casting method. The FT-IR results revealed the crosslinking interaction between WAH and CS due to the Millard reaction. The morphology, transmittance, thermal properties and mechanical properties of composite WAH/CS films were investigated. As the results showed, the tensile strength, light transmittances and thermal stability of the WAH-based composite films increased with the increment of WAH/CS content ratio. In addition, the results of oxygen transfer rate (OTR) and water vapor permeability (WVP) suggested that the OTR and WVP values of the films decreased due to the addition of CS. The maximum value of tensile strengths of the composite films achieved 71.2 MPa and the OTR of the films was low as 0.16 cm3·μm·m−2·24 h−1·kPa−1, these properties are better than those of other hemicelluloses composite films. These results suggested that the barrier composite films based on WAH and CS will become attractive in the food packaging application for great mechanical properties, good transmittance and low oxygen transfer rate. [ABSTRACT FROM AUTHOR]

Highlights: [•] Rod-like chitin nanowhiskers were produced successfully by acid treatment. [•] Hydrogels were prepared by freeze–thaw technique with the three polymers. [•] The designed hydrogels had higher thermal stability and compressive strength. [•] The hydrogels could be a promising candidate for tissue engineering applications. [ABSTRACT FROM AUTHOR]

In recent years, deep eutectic solvents (DESs) are used for enhancing the enzymatic digestibility and lignin fractionation in pretreatment, while hemicellulosic fraction receives scant attention. Herein, we report a novel approach of applying alkaline deep eutectic solvents (ADESs) for dissociating hemicelluloses from woody biomass. Among these ADESs, choline chloride-monoethanolamine (C-M) was the most efficacious medium for deconstructing the recalcitrant structure of poplar and 63.3% of hemicelluloses was obtained at 80 °C. Structure analysis showed that the ADESs-extracted hemicelluloses retained partial of O -acetyl groups. Different ADESs could be used to obtain hemicelluloses with various degrees of branching. Furthermore, the enzymatic digestibility of cellulose was significantly increased by 6.6 times compared to that of the untreated poplar under the optimum conditions (C-M, 140 °C). This work provides a view on the dissociation behavior of hemicelluloses during ADESs pretreatment, which would be beneficial for devising DESs toward effective fractionation and comprehensive utilization of biomass. • Four alkaline deep eutectic solvents (ADESs) were applied to deconstruct poplar. • Choline chloride-monoethanolamine (C-M) caused the highest hemicellulose yields. • The dissociation behavior of hemicelluloses was elucidated. • Cellulose digestibility was increased by 6.6 times after C-M pretreatment. [ABSTRACT FROM AUTHOR]

Abstract: Hemicelluloses isolated from sugarcane bagasse were converted to carboxymethyl hemicelluloses (CMH) by carboxymethylation using sodium monochloroacetate and sodium hydroxide in ethanol/water medium. The reaction was performed under various temperatures, times, times of alkaline activation, the ways of the addition of alkali, and the amounts of sodium hydroxide and sodium monochloroacetate. The product had the maximum degree of substitution (DS) of 0.56. The structure of the resulting polymers was characterized with Fourier transform infrared (FT-IR) and 13C nuclear magnetic resonance (NMR) spectroscopies. Destructive methods such as thermal analysis and non-destructive techniques such as gel permeation chromatography (GPC) were used to characterize the carboxymethyl hemicellulose preparations. It was found that a significant degradation of the polymers occurred during carboxymethylation. The thermal stability of carboxymethyl hemicelluloses was higher than that of the native hemicelluloses. [Copyright &y& Elsevier]

Selective fractionation of hemicelluloses is of great significance for realizing high-value application of hemicelluloses and comprehensive utilization of lignocellulosic biomass. Tetramethylammonium hydroxide (TMAH) solvent has been confirmed as a promising solvent to selectively fractionate hemicelluloses from holocellulose. Herein, TMAH solvent was adopted to pretreat poplar thermomechanical pulp (PTMP) for the selective fractionation of hemicelluloses and enhancement of enzymatic hydrolysis performance of residues. The maximal hemicelluloses yield (65.0 %) and excellent cellulose retention rate (93.3 %) were achieved after pretreatment by the 25 wt% TMAH solvent, while the delignification was only 33.9 %. The hemicelluloses fractions could be selectively fractionated with high molecular weights (109,800–118,500 g/mol), the contents of Klason lignin in them were low (3.2–5.9 %), and the dominating structure of them was 4- O -methylglucurono- β -D-xylan. Compared to the H 2 SO 4 and NaOH methods, the hemicelluloses fractionated by TMAH method exhibited higher yields, more complete structures and higher molecular weights. Furthermore, the crystalline structure of cellulose practically remained stable, and the highest yield of enzymatic hydrolysis glucose was 57.5 %, which was 3.3 times of that of PTMP. The fractionation effectiveness of TMAH solvent was not significantly reduced after repeatedly recycling. This work demonstrated TMAH solvent could selectively fractionate hemicelluloses from PTMP and efficiently promote sustainable poplar-based biorefinery. • TMAH could selectively fractionate hemicelluloses from PTMP at room temperature. • Hemicelluloses showed a relatively good homogeneity in the form of macromolecules. • The contents of Klason lignin in hemicelluloses fractions were low (3.2–5.9 %). • The residues represented excellent cellulose retention rates (>93.3 %). • TMAH solvent exhibited recyclability for hemicelluloses fractionation. [ABSTRACT FROM AUTHOR]

• Electroactive carboxyl terminated aniline pentamer was synthesized. • Conductive hemicellulose hydrogels (CHHs) were manufactured by one-pot reaction. • CHHs possessed a stable macro-porous structure and tunable swelling behavior. • Conductivity of CHHs tuned by carboxyl terminated aniline pentamer contents. The conductive hemicellulose hydrogels (CHHs) were achieved by incorporating carboxyl terminated aniline pentamer (CTAP) into the hydrophilic xylan-rich hemicellulose networks with epichlorohydrin. CHHs were obtained by facile one-pot reaction in water at ambient temperature. The successful synthesis of CTAP was confirmed by FT-IR, 1H NMR, and UV–vis spectra. All the hydrogels reached their equilibrium-swollen state within 12 h. The morphology and the thermal stability of CHHs were adjusted by the addition of CTAP. The conductivities of CHHs could also be tuned from 8.92 × 10−5 to 2.11 × 10−3 S/m by adding the blending amounts of the CTAP from 0 to 50% mass ratio while simultaneously altering the equilibrium swelling ratio from 28.1 to 15.8. CHHs showed homogeneous porous structure, tunable swelling behavior, controllable conductivity, and good thermal stability. These results highlight that CHHs are attractive candidates to be used in biomedical applications. [ABSTRACT FROM AUTHOR]

Eucalyptus wood was pretreated with an integrated process based on hydrothermal and alkaline pretreatments. The structural changes of hemicelluloses during the pretreatments and the components of the hydrolysates were comprehensively characterized. Sugar and spectral analyses indicated that the hemicelluloses remained in the residues obtained at hydrothermal pretreatment under low temperatures were mainly composed of a (1 → 4)- β -D-Xyl p backbone with 4- O -methyl- α -D-glucuronic acids attached at O -2 of the xylose together with various monosaccharides of rhamnose, arabinose, galactose, glucose, and mannose. The pretreatments resulted in serious degradation of hemicelluloses at high pretreatment temperatures. The distribution changes of the hemicelluloses in the cell walls during the integrated pretreatments were detected by Confocal Raman Microscopy, which revealed that the dissolution of hemicelluloses in different morphological regions was inhomogeneous, and the a large portion of hemicelluloses were removed from the secondary cell wall regions during the pretreatments. Unlabelled Image • Hydrothermal and alkaline pretreatments were proposed to treat Eucalyptus wood. • The H 0 and H 170 have a linear backbone of (1 → 4)- β -D-Xyl p residues. • The dissolution of hemicelluloses in different morphological regions was uneven. • The hemicelluloses were dissolved mostly from the secondary cell wall regions. [ABSTRACT FROM AUTHOR]

[Display omitted] • TMAH could rapidly and massively fractionate hemicelluloses at room temperature. • The hemicellulosic fractionation effect of TMAH was better than that of NaOH. • The yield of hemicelluloses fractionated with TMAH solvent could reach 81.9 %. • TMAH treatment is a feasible and promising method to fractionate hemicelluloses. The fractionation of hemicelluloses is a promising method to improve the comprehensive utilization of lignocellulosic biomass. However, the effective fractionation of hemicelluloses is always limited by the structural complexity and easy degradability. In this study, tetramethylammonium hydroxide (TMAH) was developed to fractionate hemicelluloses from poplar holocellulose with high molecular weights and high yields at room temperature. Approximately 90% of hemicelluloses could be dissolved at room temperature in 1 h, and the yield was up to 81.9%. Compared with the fractionation using NaOH solution, the hemicelluloses isolated by TMAH solvent showed a more complete structure and higher purity. Meanwhile, the retention rate of cellulose after treatment with TMAH was up to 90.2%, and the crystal structure of cellulose in the residues was practically unchanged. Moreover, the TMAH solvent could be recycled to fractionate hemicelluloses. The work provides an elegant and significantly efficient method towards hemicelluloses fractionation and cellulose purification. [ABSTRACT FROM AUTHOR]

Bamboo (Phyllostachys pubescens) is a promising high-performance material because of its large planting areas, fast growth, good adaptability, high ultimate strength and stiffness. Hemicelluloses in bamboo have been focused and studied, however, less effort has been dedicated to study on the components, distributions and structures of hemicelluloses in different cells for explaining the mechanism of bamboo growth. Here, we obtained dimethyl sulfoxide (DMSO)-soluble and alkali (NaOH)-soluble hemicelluloses from bamboo fibers (BF) and parenchyma cells (PC), which were separated from bamboo (Phyllostachys pubescens) by their density difference. Molecular weight analysis revealed that the molecular weights of DMSO-soluble and alkali-soluble hemicelluloses isolated from PC were higher than those isolated from BF. Chemical compositions and cell morphology was characterized by field emission scanning electron microscope (FE-SEM), high-performance anion exchange chromatography (HPAEC), and confocal Raman microscope (CRM). The results showed that the content of cellulose (36.32 %) was higher in BF with thicker wall, while the content of lignin and hemicelluloses (36.33 % and 19.39 %, respectively) was higher in PC with thinner wall. The Fourier transform infrared (FT-IR) spectra and nuclear magnetic resonance (NMR) technique analyses indicated that bamboo hemicelluloses were composed of O -acetyl- α - L -arabino-4- O -methylglucurono- β -(1→4)- D -xylan and β -(1→3) (1→4)-glucan. 1H NMR showed that the acetylation degree of H D -Fiber (0.069) was lower than that of H D -Parenchyma (0.127). Particularly, the hemicelluloses isolated from BF were acetylated only on C3 position, while hemicelluloses isolated from PC were acetylated both on C2 and C3 positions. This work presents a novel understanding about hemicelluloses structures of different cell types in bamboo and holds promises for the high-value added utilization of bamboo in the fields of food-related productions and biorefinery. [Display omitted] • Hemicelluloses isolated from bamboo fibers and parenchyma cells were firstly investigated. • Hemicelluloses from parenchyma cells were acetylated on C2 and C3 position. • Hemicelluloses from bamboo fibers were acetylated only on C3 position. • The major structure of hemicelluloses is O -acetyl- α - L -arabino-4- O -methylglucurono-(1→4)- β - D -xylan. • The second major structure of hemicelluloses is β -(1→3) (1→4)-glucan. [ABSTRACT FROM AUTHOR]

The hemicelluloses were isolated with 10% KOH at 25 °C from dewaxed and delignified bamboo powder. The alkali-soluble hemicelluloses from Sinocalamus affinis were fractionated by ammonium sulphate precipitation method. The bamboo alkali-soluble hemicelluloses yielded seven hemicellulosic fractions obtained at 0, 5, 15, 25, 40, 55, and 70% saturation with ammonium sulphate. It was found that the more branched hemicelluloses were precipitated at higher ammonium sulphate concentrations (55 and 70%), the more linear hemicelluloses were precipitated at lower ammonium sulphate concentrations (0, 5, 15, 25, and 40%). The molecular weights of hemicellulosic fractions become lower from 35,270 (H 0 ) to 18,680 (H 70 ) g mol −1 with the increasing concentrations of saturated ammonium sulphate from 0 to 70%. Based on the FT-IR, 1 H, 13 C and 2D HSQC NMR studies, the alkali-soluble hemicelluloses were 4- O -methyl-glucuronoarabinoxylans composed of the (1 → 4)-linked β- d -xylopyranosyl backbone with branches at O -3 of α-L-arabinofuranosyl or at O -2 of 4- O -methyl-α- d -glucuronic acid. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cholinium amino acids-based DESs were designed to fractionate hemicellulose. • Integration of water into DESs enhanced hemicellulose removal. • Effect of water in DESs on structural features of hemicellulose were revealed. • DES aqueous mixtures showed reusability in hemicellulose extraction. Novel and green cholinium amino acids-based deep eutectic solvents (DESs) and their aqueous mixtures were synthesized and employed in deconstructing poplar for hemicellulose fractionation. The effects of water content in DESs on hemicellulose dissociation and structural features were comprehensively investigated, along with the reusability of DESs for treatment. The integration of water into DESs could facilitate hemicellulose fractionation, and the cholinium lysine: urea with 5 wt% water (CL: U-5) demonstrated the best performance with a hemicellulose yield of 59.2%. Further structure analysis revealed that hemicelluloses with various branching degrees and molecular weights were obtained with varying water content of DESs. Furthermore, the CL: U-5 had recyclability and reusability with a 40.5% hemicellulose yield obtained after reused three times. The novel and eco-friendly cholinium amino acids-based DESs treatment provides an effective and sustainable strategy for hemicellulose fractionation from woody biomass. [ABSTRACT FROM AUTHOR]

Eucalyptus was sequentially extracted with 70% ethanol containing 0.4, 1.0, 2.0, 3.0, and 5.0% NaOH for 2 h at 80 °C. The chemical composition and structural features of the hemicellulosic fractions obtained were comparatively characterized by the combination of high-performance anion-exchange chromatography, gel permeation chromatography, Fourier transform infrared, and nuclear magnetic resonance spectroscopies. Furthermore, the main component distribution and their changes in cell wall were investigated by confocal Raman microscopy. Based on the Fourier transform infrared and nuclear magnetic resonance analyses, the hemicelluloses extracted from Eucalyptus mainly have a linear backbone of (1 → 4)-linked-β- d -xylopyranosyl residues decorated with branch at O -2 of 4- O -methyl-α-glucuronic acid unit. Raman analysis revealed that the dissolution of hemicelluloses was different in the morphological regions, and the hemicelluloses released mainly originated from the secondary wall. The information obtained from the study conducted by combining chemical characterization with ultrastructure provides important basis for studying the mechanism of the alkali treatment. [ABSTRACT FROM AUTHOR]

Exploration of lignocellulosic biomass provides a sustainable and eco-friendly route for producing liquid fuels, materials, and chemicals. However, direct utilization of lignocelluloses is limited by the stable and complicated cross-linking structure of the plant cell wall. Hydrothermal pretreatment (HTP) is a green and cost-effective technology because it can disrupt lignin-carbohydrate complex (LCC) linkages, dissolve hemicelluloses and lignin, and redistribute lignin in the cell wall layers without utilization of any chemicals. Thus, HTP is expected to achieve industrial scale in second-generation biorefineries and circular bioeconomies. This review analyzed the deconstruction of lignocelluloses by HTP, with particular emphasis on the formation mechanism of hemicellulose degradation products and the structural evolution of hemicelluloses and lignin accompanying HTP. Meanwhile, the formation mechanism of pseudolignin and its effect on the enzymatic hydrolysis of cellulose as well as strategies for inhibiting lignin recondensation were discussed. • Reviewing the hydrothermal deconstruction of lignocelluloses. • Potential degradation products in hydrolysates are focused. • Formation of pseudolignin and its inhibition on enzymolysis are discussed. • Tracking the structural changes of hemicelluloses and lignin during the treatment. • Strategies to suppress the acid-catalyzed condensation of lignin are summarized. [ABSTRACT FROM AUTHOR]

Acidic deep eutectic solvents (DESs) are promising media for lignin valorization and cellulose conversion due to their good ability in efficient deconstruction of plant cell wall. However, hemicellulose extraction from lignocellulose using acidic DESs remains a challenge. Herein, novel and green Brønsted acidic DESs (BDESs) were synthesized from natural organic acids and common polyols and successively adopted to deconstruct corncob for mild fractionation of hemicelluloses. Oxalic acid (OA)-based BDESs were preferred for corncob processing due to the high solubility of xylan. The results revealed that the suitable acidity of DESs and mild temperature effectively avoided the over-degradation of hemicelluloses. The chemical composition and structural features of the recovered hemicelluloses were investigated systematically. Moreover, after ethylene glycol (EG)-OA BDES was recycled and reused three times, the extraction still resulted in a satisfactory hemicellulose yield. The novel and eco-friendly processing offers a practical and sustainable route for hemicellulose extraction in acidic condition. [Display omitted] • Novel Brønsted acidic deep eutectic solvents (BDESs) were designed and prepared. • BDESs processing facilitated the hemicellulose recovery at mild conditions. • Effects of BDESs on composition and structure of hemicelluloses were revealed. • Ethylene glycol-oxalic acid was reused with a satisfactory hemicellulose yield. [ABSTRACT FROM AUTHOR]

Abstract: The dewaxed sample from Triploid of Populus tomentosa Carr. was extracted by using organic alkaline solvent (Dimethylformamide, DMF) via hydrothermal pretreatment. Neutral sugar compositions and molecular weight analysis demonstrated that the hemicellulosic fractions with a higher Uro/Xyl ratio, namely the more branched hemicelluloses, had higher molecular weights. Interestingly, these results were different from the previous report, in which the ratio of Uro/Xyl in the water-soluble hemicellulosic fraction was more than that of the alkali-soluble hemicellulosic fraction. Spectroscopy (FTIR, 1H NMR, 13C NMR, and HSQC) analysis indicated that the hemicellulosic fractions were mainly composed of (1→4)-linked α-d-glucan from starch and (1→4)-linked β-d-xylan attached with minor amounts of branched sugars from hemicelluloses. In addition, thermal analysis implied that linear hemicelluloses showed more thermal stability than the branched ones during pyrolysis. [Copyright &y& Elsevier]