Harnessing Renewable Lignocellulosic Potential for Sustainable Wastewater Purification.

Utilizing renewable lignocellulosic resources for wastewater remediation is crucial to achieving sustainable social development. However, the resulting by-products and the synthetic process characterized by complexity, high cost, and environmental pollution limit the further development of lignocellulose-based materials. Here, we developed a sustainable strategy that involved a new functional deep eutectic solvent (DES) to deconstruct industrial xylose residue into cellulose-rich residue with carboxyl groups, lignin with carboxyl and quaternary ammonium salt groups, and DES effluent rich in lignin fragments. Subsequently, these fractions equipped with customized functionality were used to produce efficient wastewater remediation materials in cost-effective and environmentally sound manners, namely, photocatalyst prepared by carboxyl-modified cellulose residue, biochar-based adsorbent originated from modified lignin, and flocculant synthesized by self-catalytic in situ copolymerization of residual DES effluent at room temperature. Under the no-waste principle, this strategy upgraded the whole components of waste lignocellulose into high-value-added wastewater remediation materials with excellent universality. These materials in coordination with each other can stepwise purify high-hazardous mineral processing wastewater into drinkable water, including the removal of 99.81% of suspended solids, almost all various heavy metal ions, and 97.09% chemical oxygen demand, respectively. This work provided promising solutions and blueprints for lignocellulosic resources to alleviate water shortages while also advancing the global goal of carbon neutrality.

Promoting the disassemble and enzymatic saccharification of bamboo shoot shells via efficient hydrated alkaline deep eutectic solvent pretreatment.

Pretreatment is a key process restricting the development of biorefinery. This work developed a pretreatment process based on an ethanolamine/acetamide alkaline deep eutectic solvent (ADES). Under microwave assistance, pure ADES pretreatment at 100 °C for 10 min achieved 95.9 % delignification and 95.2 % hemicellulose removal of bamboo shoot shells (BSS). Further, when 75 % water was added to pure DES to prepare hydrated DES (75 %-HADES), impressive delignification (93.2 %), hemicellulose removal (92.2 %) and cellulose recovery (94.8 %) were still achieved. The cellulose digestibility of the 75 %-HADES pretreated solid residue was significantly increased from 12.2 % (the control) to 91.2 %. Meanwhile, the structural features of hemicellulose and lignin macromolecules fractionated by 75 %-HADES pretreatment were well preserved, offering opportunities for downstream utilization. Overall, this work proposes an effective pretreatment strategy with the potential to enable the utilization of all major components of bamboo shoot shells.

Structural elucidation and targeted valorization of untractable lignin from pre-hydrolysis liquor of xylose production via a simple and robust separation approach.

Effective separation of lignin macromolecules from the xylose pre-hydrolysates (XPH) during the xylose production, thus optimizing the separation and purification process of xylose, is of great significance for reducing the production costs, achieving the high value-added utilization of lignin and increasing the industrial revenue. In this study, a simple and robust method (pH adjustment) for the separation of lignin from XPH was proposed and systematically compared with the conventional acid-promoted lignin precipitation method. The results showed that the lignin removal ratio (up to 60.34 %) of this simple method was higher than that of the conventional method, and the proposed method eliminated the necessity of heating and specialized equipment, which greatly reduced the separation cost. Meanwhile, this simple method does not destroy the components in XPH (especially xylose), ensuring the yield of the target product. On the other hand, the obtained lignin was nano-scale with less condensed structures, which also possessed small molecular weights with narrow distribution, excellent antioxidant activity (8-14 times higher than commercial antioxidants) and UV protection properties. In conclusion, the proposed simple separation method could effectively separate lignin from XPH at low cost, and the obtained lignin had potential commercial applications, which would further enhance the overall profitability of industrial production.

Green and sustainable production of high-purity lignin microparticles with well-preserved substructure and enhanced anti-UV/oxidant activity using peroxide-promoted alkaline deep eutectic solvent.

Deep eutectic solvents (DESs) have emerged as promising and eco-friendly solvents for the efficient extraction of lignin from biomass due to their low cost and environmental benefits. Nevertheless, the prevalent use of acidic DESs in lignin extraction often results in excessive depolymerization and recondensation of lignin, thereby impeding its downstream applications. In this study, we developed a range of alkaline DESs (ADESs), both pure and peroxide-containing, for the extraction of high-quality lignin from bamboo. Moreover, carbon dioxide (CO2) was employed for the precipitation and regeneration of the extracted lignin. The obtained lignin fractions were comprehensively characterized in terms of yield, purity, morphology, solubility, structural features, and anti-UV/oxidant activity. The results showed that the monoethanolamine-based ADES demonstrated superior performance among the pure ADESs. Structural analysis confirmed the well-preserved substructures of lignin fractions obtained using ADESs, with ß-O-4 bond retention ranging from 49.8 % to 68.4 %. The incorporation of a suitable amount of peroxide improved lignin yield, morphology, solubility, and anti-UV/oxidant activity. Additionally, the anti-UV/oxidant activity of lignin exhibited a positive correlation with its phenolic hydroxyl content. This study provides a valuable reference for the green and sustainable production and valorization of lignin within the existing biorefinery framework.

Fractionation and evaluation of light-colored lignin extracted from bamboo shoot shells using hydrated deep eutectic solvents.

In this study, light-colored lignin was extracted from bamboo shoot shells (BSS) using a hydrated deep eutectic solvent (DES) pretreatment. The hydrated DES used in pretreatment consist of formic acid, benzyl triethylammonium chloride (BTEAC) and water. The pretreatment using a hydrated DES containing 30% water (H30) demonstrate efficient delignification (82.9%). Additionally, the hydrated DES protected the ß-O-4 linkage from excessive cleavage and recondensation as well as keep the light-colored of lignin. Moreover, the hydrated DES extracted lignin exhibits superior antioxidant performance and tyrosinase inhibitory capacity compared to the control. Notably, incorporating 5% lignin of H30-extracted lignin into a commercial suncream led to a remarkable enhancement of the SPF value, elevating from 14.8 to 32.6. In summary, the proposed hydrated DES pretreatment method offers significant benefits for extracting light-colored lignin, thereby promoting the multifunctional application of lignin in cosmetics.

Conversion of control and genetically-modified poplar into multi-scale products using integrated pretreatments.

In this work, a green and robust pretreatment which integrated acetic acid-catalyzed hydrothermal and wet mechanical pretreatment, was developed to efficiently produce high yield (up to 40.12%) of xylooligosaccharides and digestible substrates from Caffeoyl Shikimate Esterase down-regulated and control poplar wood. Subsequently, superhigh yield (more than 95%) of glucose and residual lignin were obtained after a moderate enzymatic hydrolysis. The residual lignin fraction exhibited a well-preserved ß-O-4 linkages (42.06/100Ar) and high S/G ratio (6.42). Subsequently, lignin-derived porous carbon was successfully synthesized, and it exhibited a high specific capacitance of 273.8 F g-1 at 1.0 A g-1 and long cycling stability (remained 98.5% after 10,000 cycles at 5.0 A g-1) compared to control poplar wood, demonstrating that special advantage of this genetically-modified poplar in this integrated process. This work developed an energy-saving and eco-friendly pretreatment technology as a waste-free route for converting different lignocellulosic biomass to multiple products.

Molecular insights into the evolution of woody plant decay in the gut of termites.

Plant cell walls represent the most abundant pool of organic carbon in terrestrial ecosystems but are highly recalcitrant to utilization by microbes and herbivores owing to the physical and chemical barrier provided by lignin biopolymers. Termites are a paradigmatic example of an organism's having evolved the ability to substantially degrade lignified woody plants, yet atomic-scale characterization of lignin depolymerization by termites remains elusive. We report that the phylogenetically derived termite Nasutitermes sp. efficiently degrades lignin via substantial depletion of major interunit linkages and methoxyls by combining isotope-labeled feeding experiments and solution-state and solid-state nuclear magnetic resonance spectroscopy. Exploring the evolutionary origin of lignin depolymerization in termites, we reveal that the early-diverging woodroach Cryptocercus darwini has limited capability in degrading lignocellulose, leaving most polysaccharides intact. Conversely, the phylogenetically basal lineages of "lower" termites are able to disrupt the lignin-polysaccharide inter- and intramolecular bonding while leaving lignin largely intact. These findings advance knowledge on the elusive but efficient delignification in natural systems with implications for next-generation ligninolytic agents.

Enhancing saccharification of bamboo shoot shells by rapid one-pot pretreatment of hydrated deep eutectic solvent.

In this work, a rapid one-pot hydrated deep eutectic solvent (DES) pretreatment was proposed to facilitate the conversion of carbohydrates from lignocellulosic biomass to monosaccharides. Specifically, the pure and hydrated DES based on benzyl triethylammonium chloride (BTEAC), formic acid (FA) and water was used to pretreat bamboo shoot shells (BSS) by microwave heating. The pretreated solid residues were enzymatically saccharified to produce fermentable sugars, and the hydrolyzed carbohydrates and lignin remained in the hydrolyzate. The results showed that the yield of monosaccharides from the hydrated DES hydrolyzate (193.7-228.4 g/kg) was significantly higher than that (45.9-66.1 g/kg) of pure DES. The 30% hydrated DES pretreatment achieved the best glucose yield (89.03%) and a total monosaccharides yield of 555.4 g/kg, which corresponded to a conversion ratio of carbohydrates to monosaccharides of 87.0%. The proposed process is a robust method for the efficiently convert carbohydrates from BSS into monosaccharides.

Enhancing thermal conductivity and toughness of cellulose nanofibril/boron nitride nanosheet composites.

Generally, the thermal conductivity (TC) of composite based on cellulose nanofibrils (CNF) is improved by adding thermal conductive filler, which inevitably leads to the loss of its mechanical properties. In this work, it is the first to simultaneously improve the toughness and TC of CNF/boron nitride nanosheets (BNNS) composite from the perspective of thermal conductive filler addition and CNF crystal change. The hydrophilic-modified BNNSs were successfully prepared by xylose-assisted ball-milling prior to adding into CNF. Compared with that of CNF film (1.34 W/(m·K)), the in-plane TC of CNF/BNNS composite (12.68 W/(m·K)) increased significantly by 846 % with loading 30 % BNNS. Afterwards, both toughness (8.0 MJ·m-3, increased ~250 %) and TC (14.7 W/(m·K), increased ~16 %) of CNF/BNNS composite were further enhanced significantly by mercerization with 12.5 % NaOH solution. The simultaneously improvement of toughness and TC is unprecedented in related studies, which contributes to the effective preparation of thermal management materials.

Structural elucidation and targeted valorization of poplar lignin from the synergistic hydrothermal-deep eutectic solvent pretreatment.

Elucidating the structural variations of lignin during the pretreatment is very important for lignin valorization. Herein, poplar wood was pretreated with an integrated process, which was composed of AlCl3-catalyzed hydrothermal pretreatment (HTP, 130-150 °C, 1.0 h) and mild deep-eutectic solvents (DES, 100 °C, 10 min) delignification for recycling lignin fractions. Confocal Raman Microscopy (CRM) was developed to visually monitor the delignification process during the HTP-DES pretreatment. NMR characterizations (2D-HSQC and 31P NMR) and elemental analysis demonstrated that the lignin fractions had undergone the following structural changes, such as dehydration, depolymerization, condensation. Molecular weights (GPC), microstructure (SEM and TEM), and antioxidant activity (DPPH analysis) of the lignins revealed that the DES delignification resulted in homogeneous lignin fragments (1.32 < PDI < 1.58) and facilitated the rapid assemblage of lignin nanoparticles (LNPs) with controllable nanoscale sizes (30-210 nm) and excellent antioxidant activity. These findings will enhance the understanding of structural transformations of the lignin during the integrated process and maximize the lignin valorization in a current biorefinery process.

Efficient fractionation of bamboo residue by autohydrolysis and deep eutectic solvents pretreatment.

Bamboo processing residue, which is rich in parenchyma cells, was treated as huge waste in bamboo processing industry, such as reassemble bamboo and bamboo flooring. Herein, autohydrolysis and rapid different deep eutectic solvents (DES) delignification strategy were consecutively performed to remove hemicelluloses and lignin from bamboo processing residue. The xylooligosaccharides (XOS) with high yield (34.35%) was achieved in the autohydrolysis process. Results showed that alkaline DES pretreatment resulted in the highest glucose yield (88.22%) and relatively high delignification rate (83.75%) as well as well-preserved lignin structures. However, the lignin fractions obtained under acidic DES conditions were tending to assemble into lignin nanoparticles (LNPs) and having excellent antioxidant activity as compared to those obtained from alkaline DES system. In brief, the combination of autohydrolysis and rapid DES delignification can achieve orientated fractionation of the components from the industrialized bamboo.

Structure of corn bran hemicelluloses isolated with aqueous ethanol solutions and their potential to produce furfural.

The alkali-soluble hemicelluloses extracted with 10% KOH solution from corn bran were further isolated with different concentrations of aqueous ethanol solutions. Herein 92.2% of the original hemicelluloses can be obtained and the cellulase enzymatic hydrolysis rate of the alkali treated corn bran can reach to 97.2%. The corn bran hemicelluloses were mainly glucuronoarabinoxylan, in which xylose (48.4-53.8%) and arabinose (27.8-33.2%) were the main components. More linear hemicelluloses with high molecular weight tended to be precipitated in low concentration aqueous ethanol solutions. Furthermore, the relationship between the structural features of these alkali-soluble corn bran hemicelluloses and their furfural yield was investigated in MIBK (methyl isobutyl ketone)/H2O biphasic system. Results showed that the hemicelluloses with high xylose content are benefit to the furfural production, and the highest furfural yield of 67.7% was obtained.

A synergistic hydrothermal-deep eutectic solvents (DES) pretreatment for acquiring xylooligosaccharides and lignin nanoparticles from Eucommia ulmoides wood.

To achieve an effective deconstruction for preparation of xylooligosaccharides (XOS) and lignin nanoparticles (LNPs) from Eucommia ulmoides, a synergistic pretreatment was successfully developed. Herein, the hemicelluloses were preferentially dissociated in acetic acid-catalyzed hydrothermal pretreatment (HTP) for preparation of XOS, and the hydrothermally-pretreated substrate was then subjected to deep eutectic solvents (DES) delignification for fabrication of LNPs. Results showed that the optimal yield (33.88% based on xylan) of XOS is obtained under the given HTP condition (170 °C, 0.5 h). NMR characterization showed that the linkages of lignin were mainly composed of ß-O-4, ß-ß, ß-5, etc. Besides, GPC analysis showed that the molecular weight of DES lignin fractions was lower (1130-1200 g/mol) than those of corresponding parent lignin fractions (8500-9620 g/mol). Further TEM characterization indicated that the optimal LNPs fraction has a narrow size distribution and the corresponding size is ranged from 60 to 110 nm. In short, the synergistic pretreatment could be used as a green and cost-effective approach for the development of bio-based chemicals and biomaterials from Eucommia ulmoides biomass.

Ultrafast alkaline deep eutectic solvent pretreatment for enhancing enzymatic saccharification and lignin fractionation from industrial xylose residue.

An aspirational pretreatment method for efficient fractionation and tailored valorization of large industrial biomass can ensure the realizability of sustainable biorefinery strategies. In this study, an ultrafast alkaline deep eutectic solvents (DES) pretreatment strategy was developed to efficiently extract the lignin nanoparticles and retain cellulose residues that could be readily enzymatic saccharified to obtain fermentative glucose for the bioenergy production from industrial xylose residue. Results showed that the DES pretreatment had excellent delignification performance and the regenerated DES lignin nanoparticles exhibited well-preserved structures and excellent antioxidant activity, as well as low molecular weights and relatively uniform size distribution, which could facilitate downstream catalytic degradation for production of chemicals and preparation of lignin-based materials. Under the optimal condition (DES pretreatment: 80 °C, 10 min; saccharification: 10 FPU/g, 5 wt%, 100 mg/g Tween 80), the glucose yield of 90.12% could be achieved, which was dramatically increased compared to raw materials.

Exploration of deep eutectic solvent-based biphasic system for furfural production and enhancing enzymatic hydrolysis: Chemical, topochemical, and morphological changes.

Developing a biorefinery process for a highly integrated valorization and fractionation of lignocellulose is crucial for its utilization. Herein, a biphasic system comprising choline chloride/lactic acid and 2-methyltetrahydrofuran with Al2(SO4)3 and H2SO4 as catalysts was applied to pretreat Eucalyptus. Results showed that under the optimized conditions (150 °C, 30 min, 0.2 M Al2(SO4)3, 0.075 M H2SO4), the furfural yield and enzymatic hydrolysis efficiency could reach 54.7% and 97.0%, respectively. The efficient cellulose conversion was attributed to remarkable removal of lignin (91.0%) and hemicelluloses (100.0%), thereby causing the disruption of cell wall structure and enhancement of cellulose accessibility. Meanwhile, confocal Raman microscope and atomic force microscope displayed that the pretreatment resulted in the decreasing intensities of carbohydrates and lignin different regions of cell walls, and exposing of the embedded microfibers from noncellulosic polymers. Overall, the deep eutectic solvent-based biphasic system displayed high performance for effective utilization of carbohydrate components in lignocellulose.

Effects of P-Coumarate 3-Hydroxylase Downregulation on the Compositional and Structural Characteristics of Lignin and Hemicelluloses in Poplar Wood (Populus alba × Populus glandulosa).

Elucidating the chemical and structural characteristics of hemicelluloses and lignin in the p-coumarate 3-hydroxylase (C3H) down-regulated poplar wood will be beneficial to the upstream gene validation and downstream biomass conversion of this kind of transgenic poplar. Herein, the representative hemicelluloses and lignin with unaltered structures were prepared from control (CK) and C3H down-regulated 84K poplars. Modern analytical techniques, such as 13C NMR, 2D-HSQC NMR, and gel chromatography (GPC), were performed to better delineate the structural changes of hemicelluloses and lignin caused by transgenesis. Results showed that both the hemicelluloses (H-CK and H-C3H) extracted from control and C3H down-regulated poplar wood have a chain backbone of (1→4)-ß-D-Xylan with 4-O-Me-α-D-GlcpA as side chain, and the branch degree of the H-C3H is higher than that of H-CK. With regarding to the lignin macromolecules, NMR results demonstrated that the syringyl/guaiacyl (S/G) ratio and dominant substructure ß-O-4 linkages in C3H down-regulated poplar were lower than those of control poplar wood. By contrast, native lignin from C3H down-regulated poplar wood exhibited higher contents of p-hydroxybenzoate (PB) and p-hydroxyphenyl (H) units. In short, C3H down-regulation resulted in the chemical and structural changes of the hemicelluloses and lignin in these poplar wood. The identified structures will facilitate the downstream utilization and applications of lignocellulosic materials in the biorefinery strategy. Furthermore, this study could provide some illuminating results for genetic breeding on the improvement of wood properties and efficient utilization of poplar wood.

Short-time deep eutectic solvents pretreatment enhanced production of fermentable sugars and tailored lignin nanoparticles from abaca.

Deep eutectic solvents (DES) pretreatment is a promising approach to decrease "biomass recalcitrance" and boost the cellulose bioconversion as well as lignin valorization. In this study, a short-time DES pretreatment strategy was performed to enhance the production of high-yield fermentable sugars and tailored lignin nanoparticles (LNPs) from abaca. The glucose yield reached 92.4% under the optimal pretreatment condition (110 °C, 30 min), which was dramatically increased in comparison with that (9.5%) of control abaca. Simultaneously, nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC) techniques indicated that the removed and regenerated DES lignin fractions displayed depolymerized structures and have relatively low molecular weight with relatively homogeneous morphology and narrow size distribution. Transmission electron microscope (TEM) analysis indicated that these lignin fractions are LNPs and the size of the optimal LNPs fraction is ranged from 30 nm to 50 nm. Moreover, all the DES lignin exhibited excellent antioxidant activities as compared to the commercial antioxidant butylated hydroxytoluene (BHT), which can be used as a promising natural antioxidant in industry. In short, this study demonstrated that the short-time DES pretreatment will improve the enzymatic digestibility and facilitate the controllable production and valorization of LNPs from abaca biomass, which will further promote the economic and overall benefits of biorefinery.

A synergistic hydrothermal-deep eutectic solvent (DES) pretreatment for rapid fractionation and targeted valorization of hemicelluloses and cellulose from poplar wood.

A synergistic pretreatment that realizing effective fractionation and targeted valorization can guarantee the implementability to future biorefinery scenario. In the present study, a stepwise approach using hydrothermal and deep eutectic solvents (DES) pretreatment was developed to preferentially dissociate hemicelluloses and further remove lignin from poplar, while retaining a cellulose-rich substrate that can be easily digested via enzymatic saccharification to obtain glucose. Results showed that the hydrothermal filtrate is mainly composed of xylooligosaccharide (XOS), monosaccharides, byproducts, and xylan-type hemicelluloses, which have homogenous structures and uniform molecular weights distribution as well as excellent antioxidant activity. Subsequent DES pretreatment further removed the lignin barriers, leading to a remarkable increase in the saccharification efficiency from 15.72% to 96.33% under optimum conditions for enzymatic hydrolysis. In short, the integrated pretreatment is effective for dissociating and chemical conversion of poplar wood, which was reasonable to promote the frontier of highly available biorefinery.

The effects of mild Lewis acids-catalyzed ethanol pretreatment on the structural variations of lignin and cellulose conversion in balsa wood.

Ethanol organosolv pretreatment is a green and effective deconstruction process for main components in lignocellulose biomass. Herein, balsa wood was firstly subjected to a modified ethanol/water solution (EWS) pretreatment with different Lewis acids catalysts (AlCl3, CuCl2, FeCl3) at 140-180 °C. The delignification ratios and structural characteristics of the dissociated lignin, enzymatic hydrolysis of cellulose in the pretreated substrates as well as the degradation products from hemicellulose during the pretreatment process were comprehensively investigated. Results showed that dissociation and depolymerization of lignin fragments was robust in AlCl3-catalyzed pretreatment than those by CuCl2 and FeCl3-catalyzed pretreatment. In detail, the results showed that the optimal delignification ratio and removal of the hemicelluloses occurred in AlCl3-catalyzed pretreatment. Moreover, the structural characterizations of lignin fractions by 2D-HSQC, 31P NMR and GPC also revealed that the obtained lignin has the advantages of small and homogeneous molecules as well as abundant functional groups. As a result of adequate removal of hemicellulose and lignin, the enzymatic digestibility of cellulose in the pretreated residue was significantly elevated. In short, the above findings are also in line with the concept of maximizing the utilization of bioresources, which will be beneficial for value-added applications of balsa wood in the biorefinery.