Insights into the contributions of hemicelluloses to assembly and mechanical properties of cellulose networks.

In order to explore the contributions of hemicelluloses to the assembly and mechanical properties of cellulose networks, the bacterial cellulose (BC) composites containing xylan and glucomannan were prepared to mimic the polysaccharides network of plant cell walls. Both polysaccharides could induce the change of diameters of cellulose ribbons and influence the crystallization of cellulose. Besides, small-angle X-ray scattering (SAXS) demonstrated that xylan inhibited the assembly of microfibrils into cellulose ribbons, while glucomannan promoted the packing of microfibrils. The changes of cellulose crystalline structure and assembly pattern of cellulose contributed to the lower tensile strength and higher strain at break of the BC composites as compared with the BC. The results provide a profound insight into the structure-property relationships of cellulose networks affected by hemicelluloses, which could be conducive to the development of cellulose biomaterials.

Mild pretreatment with Brønsted acidic deep eutectic solvents for fractionating ß-O-4 linkage-rich lignin with high sunscreen performance and evaluation of enzymatic saccharification synergism.

Herein, a mild fractionation method by employing polyol-based Brønsted acidic DESs (BDESs) was proposed to extract lignin with well-preserved ß-O-4 substructures and to enhance fermentable sugar yields simultaneously. For ethylene glycol-oxalic acid (EG-OA), more than 53 % of lignin was obtained and superb carbohydrate digestibility (i.e., glucose and xylose yields were reached to 94.6 % and 87.7 %, respectively) was achieved after pretreatment. Remarkably, detailed structural studies revealed that the polyol was incorporated into lignin, which stabilized reactive carbocation intermediates formed during BDESs treatment and prevented undesired recondensation reactions. This lignin protection mechanism was shown to play a key role in enzymatic hydrolysis enhancement and lignin valorization. The resultant ß-O-4 linkage-rich lignin fractions were attractive for natural sunscreen applications due to their lighter color and excellent UV-blocking performance. Overall, this work proposed a sustainable and economically practical lignin-first biorefinery approach that is beneficial for achieving comprehensive valorization of lignocellulose.

Multifunctional hybrid hydrogel with transparency, conductivity, and self-adhesion for soft sensors using hemicellulose-decorated polypyrrole as a conductive matrix.

Polymers with high conductivity and cross-linking ability are ideal materials for the preparation of conductive hydrogels for application in wearable electronic devices. However, the fabrication of conductive polymer-incorporated hydrogels with good synergistic properties remains a great challenge due to the hydrophobicity and opacity of conjugated π conductive polymers. In this study, a multifunctional hybrid hydrogel was prepared by incorporating hemicellulose-decorated polypyrrole (H/PPY), polyvinyl alcohol (PVA), and tannic acid (TA) into a polyacrylamide (PAM) network. The addition of excess ammonium persulfate (APS) in the process of gelation not only initiated the polymerization of PAM but also resulted in the change of the hydrogel from opaque to transparent by continuously breaking and reducing the size of the PPY particles. The hybrid hydrogel exhibited high transparency and conductivity, good adhesion ability and mechanical performance, and high resistance strain sensitivity and could accurately monitor the strain signals of the index finger and elbow flexion and pulse beat during rest and exercise, which has promising potential for use in wearable or implantable smart sensor devices, electronic skins, and artificial intelligence applications.

Efficient fractionation of woody biomass hemicelluloses using cholinium amino acids-based deep eutectic solvents and their aqueous mixtures.

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.

Novel, recyclable Brønsted acidic deep eutectic solvent for mild fractionation of hemicelluloses.

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.

Alkaline deep eutectic solvents as novel and effective pretreatment media for hemicellulose dissociation and enzymatic hydrolysis enhancement.

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.

Synthesis of a Lignin-Fe/Mn Binary Oxide Blend Nanocomposite and Its Adsorption Capacity for Methylene Blue.

A high-performance modified lignin adsorbent was prepared through coprecipitation of ferrous, ferric, and permanganate with lignin in sodium hydroxide solution. The structural characteristics of the synthesized lignin-Fe/Mn binary oxide blend nanocomposite (L-F/M) and its performance on the methylene blue (MB) removal from aqueous solution were evaluated. Influence factors of adsorption effects were analyzed including pH, contact time, dye concentration, temperature, and thermodynamics. The pseudo-second-order kinetic model well described the adsorption kinetics, and the adsorption isotherms best fitted the Langmuir model with a maximum adsorption capacity of 252.05 mg g-1 at 298 K. The adsorption mechanism showed that the L-F/M introduced the metallic element and negative charges to the lignin surface, which improved the adherence of MB via hydrogen bonding, electrostatic interaction, and coordination. Moreover, the removal ratio of MB maintained 81.2% after being used in five adsorption-desorption cycles. Results indicated that the L-F/M obtained was an efficient candidate for dye wastewater treatment.

Synthesis of hemicellulose hydrogels with tunable conductivity and swelling behavior through facile one-pot reaction.

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.

Structure and distribution changes of Eucalyptus hemicelluloses during hydrothermal and alkaline pretreatments.

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)-ß-D-Xylp 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.