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Wood is an abundant and renewable feedstock for pulping and biorefining, but the aromatic polymer lignin greatly limits its efficient use. Sulis et al. recently reported a multiplex CRISPR editing strategy targeting multiple lignin biosynthetic genes to achieve combined lignin modifications, improve wood properties, and make pulping more sustainable. [ABSTRACT FROM AUTHOR]

This study proposes an efficient biorefining strategy for co-producing of bioethanol, furfural, and lignin nanoparticles (LNPs) from birch wood based on acid hydrotropic fractionation. Birch was fractionated into glucan-rich washed water-insoluble solids (WIS) fraction and xylose-rich spent liquor (SL) fraction with a low p -toluenesulfonic acid (p -TsOH) concentration of 15% (w/v). The obtained WIS was utilized to produce 75.5 g/L ethanol (76.3% ethanol yield based on initial sugars in the enzymatic hydrolysate) through separate hydrolysis and fermentation. Meanwhile, the xylose-rich SL was concentrated and catalyzed by dehydration to produce furfural with tetrahydrofuran (THF) as a co-solvent. The furfural concentration of 27.3 g/L (78.2% theoretical yield) was achieved from the 3-fold concentrated SL (without lignin precipitation) with a 3:1 THF-SL ratio at 160 °C for 7 min. The enzymatic hydrolysis solid residue of WIS was further fractionated by p -TsOH to prepare LNPs with an average particle size of 37.4 nm. The mass balance showed that 6.5 t oven-dry birch wood produced 1.0 t ethanol, 0.61 t furfural and 0.63 t LNPs. [ABSTRACT FROM AUTHOR]

One of the key strategies for valorizing kraft lignin (KL) into value-added products such as bio-based adhesives is to perform solvent fractionation of KL to produce lignin with improved homogeneity. Understanding the structure and properties of fractionated KL will aid in the selection of the best samples for certain applications. In this study, acetone-fractionated KL from softwood and hardwood was characterized to understand its chemical structure, elemental composition, molecular weight, and thermal properties. The results revealed that acetone-insoluble KL (AIKL) fractions from softwood and hardwood have greater molecular weight, polydispersity, glass temperature, carbohydrate content, aliphatic hydroxyl groups, and a variety of native wood lignin side chains. In contrast, acetone-soluble KL (ASKL) fractions have a significantly lower molecular weight and polydispersity, a lower glass-transition temperature, a more condensed structure, more aromatic hydroxyl groups, and fewer native wood lignin side chains. In addition, the ASKL samples demonstrated stronger adhesive force and work of adhesion toward phenol–formaldehyde (PF) and urea–formaldehyde (UF) resins than the AIKL samples, regardless of the lignin source. These findings suggest that ASKL has great potential as a substitute for phenol in PF resins and as a green additive to reinforce UF resins. [Display omitted] [ABSTRACT FROM AUTHOR]

Lignin is the most naturally abundant source of aromatics for phenolic chemicals, bioenergy sources, and functional materials. Recent works are devoted to the acid-catalyzed organosolv extraction for improving the lignin valorization. However, β –aryl ethers are mostly cleaved to form carbon–carbon bonds under the acidic condition. In this work, lignin isolated with methanolic hydrochloric acid (MHL) was compared with conventional milled wood lignin (MWL). The methanol incorporated into lignin as α –OCH 3 to prevent the cleavage of β –aryl ethers. As a result, the yield of MHL was over 12 times that of MWL. The MHL appeared a regular granular structure with an average diameter of 100 nm. Analysis of 13C–1H HSQC NMR spectra showed that MHL contained 42.6 % β –O–4 linkages whereas 35.9 % for the MWL, as well as 6.5 % β –5 and 3.2 % β – β , which was less than MWL. Moreover, 13C NMR spectroscopy confirmed that MHL was mainly isolated by the cleavage of the associated carbohydrates rather than the degradation of β –aryl ether bonds. Therefore, MHL can be utilized more as a native lignin representative than MWL for studying the physicochemical properties and the interior structures of the protolignin. • Lignin was isolated by methanolic hydrochloric acid treatment (MHL). • The methanol prevented the formation of C C bonds facilitating lignin isolation. • MHL contains higher β –aryl ether with less α –carbonyl than MWL. • The yield of MHL was 12 times more than that of MWL. • MHL is a more suitable lignin model than MWL for lignin structure analysis. [ABSTRACT FROM AUTHOR]

As a renewable biological macromolecule with aromatic structure, lignin can serve as matrix substance to maintain cell wall integrity and is regarded as the natural biomass recalcitrance. Substantial differences in the cell wall lignin topochemistry between opposite (Ow) and compression wood (Cw) trachieds in Pinus bungeana Zucc. were visualized during [Emim][OAc] pretreatment at room temperature. The ionic liqiuds treatment induced a more obvious wall swelling for highly lignified Cw tracheids than that of Ow, while dynamic Raman spectra analysis indicated the higher lignin and carbohydrates removal for Ow tracheids. Raman imaging further revealed that both lignin and carbohydrates were dissolved simultaneously within the middle lamella and secondary wall of Ow and pretreatment has little effects on Cw tracheids wall. Moreover, it was demonstrated that lignin composition was the key factor to affect the composition dissolution. In particular, lignin G-units were selectively removed from cell corner middle lamella (52.3 %) and secondary wall (62.0 %) of Ow tracheids. When cotton fiber, as a reference was treated under the same conditions, lattice conversion moving from cellulose I to II occurred. The findings confirmed the important role of lignin compostion in the dissolution behavior of carbohydrate dominant tracheids wall. • Obvious swelling behavior for highly lignified Cw tracheids. • Simultaneous dissolution of carbohydrates and lignin within Sow and middle lamella. • The lignin G-units were selectively dissolved from Ccml and Sow. [ABSTRACT FROM AUTHOR]

An integrated pretreatment that realizing effective fractionation and targeted valorization can guarantee the implementability to future biorefinery scenario. In the present study, a stepwise approach using acetic acid-catalyzed hydrothermal pretreatment (AAP) and rapid ball-milling process was successfully developed for producing high-yield of xylo-oligosaccharides (XOS), fermentable glucose and native lignin from poplar wood. It was found that the AAP removed the most hemicelluloses, releasing the highest yield (36.16%) of XOS at 160 °C for 1 h. Subsequent rapid ball-milling pretreatment for 10 min led to a remarkable increase in the saccharification efficiency from 40.68% to 91.35%. Meanwhile, the residual lignin fractions exhibited abundant β- O -4 linkages, which are beneficial to catalytic hydrogenolysis of these lignin fractions into the aromatic chemicals. Considering the integrated process could effectively produce XOS, fermentable glucose, and the residual lignin with well-preserved structures, the proposed process is a promising and efficient deconstruction strategy in current biorefinery scenario. [Display omitted] [ABSTRACT FROM AUTHOR]

The efficient utilization of lignin in 3D printing had attracted increasing attention using this abundant and eco-friendly material. However, the large-scale utilization of lignin in 3D printing remains a great challenge due to its inherent brittleness and non-thermoplasticity. In this study, thermoplastic polyurethane (TPU) was introduced to regulate the rheological properties of lignin for 3D printing. The Lignin/TPU composite of 3D printing exhibited a smooth surface, non-plastic, warm wood touch, and natural color at 50 wt% lignin loading. To further improve the mechanical properties of the composite, carbon fiber (CF) was added to the Lignin/TPU composite. The resulting CF/Lignin/TPU composites possessed 1.7 times higher tensile strength and 2.4 times higher elongation at break compared to Lignin/TPU composite. Meanwhile, the smooth surface of filament and dense interlayer bonds of printed specimens are also achieved. This work provides new insights to realize the high-value utilization of lignin and expands the practical application of lignin in 3D printing. [Display omitted] • TPU imparts lignin flexibility and thermoplastic properties. • Up to 50 wt% lignin composites available for 3D printing • The addition of carbon fiber enhances the mechanical properties of the composite. • Excellent interlayer bonding properties of 3D printed specimens after CF addition [ABSTRACT FROM AUTHOR]

The current study investigates for the first time the physico-chemical performances of lignins from cactus waste seeds (CWS) and spent coffee (SC) in comparison to previously isolated lignins from sugar byproducts (bagasse (SCB) and beet pulp (SBP)). In this work, lignin-phenol formaldehyde (LPF) resins were formulated using various lignin loadings (5–30 wt%), characterized and applied in the manufacturing of plywood panels. Several characterization techniques were applied to identify the chemical and morphological properties, thermal stability, and phenolic content of the extracted lignins, as well as the bonding strength and wood failure of the formulated resins. Results showed that the CWS and SC could be considered as an important source for lignin recovery with a considerable yield of 15.46 % and 27.08 % and an important hydroxyl phenolic content of 1.26 mmol/g and 1.36 mmol/g for CWS and SC, respectively. Interestingly, 20 wt% of extracted lignins in PF adhesives were the optimal formulation showing an improved modulus of elasticity (MOE) of about 3505, 3536 and 3515 N/mm2, and a higher modulus of rupture (MOR) of about 55, 55 and 56 N/mm2 for panels containing CWS, SC and SCB-lignins, respectively, over the reference panels (MOE = 3198 N/mm2 and MOR = 48 N/mm2). Additionally, formaldehyde emission from plywood remarkably decreases by up to 20 % when lignin was incorporated into the PF matrix. Herein, the treatment of the CWS and SC for the extraction of alkali lignin and its application showed a new route to produce high added-value products from underused residues. [ABSTRACT FROM AUTHOR]

With the increasing demands on sustainability in the material science and engineering landscape, the use of wood, a renewable and biodegradable material, for new material development has drawn increasing attentions in the materials science community. To promote the development of new wood-based materials, it is critical to understanding not only wood's hierarchical structure from molecule to macroscale level, but also the interactions of wood with other materials and chemicals upon modification and functionalization. In this review, we discuss the recent advances in the Raman imaging technique, a new approach that combines spectroscopy and microscopy, in wood characterization and structural evolution monitoring during functionalization. We introduce the principles of Raman spectroscopy and common Raman instrumentations. We survey the use of traditional Raman spectroscopy for lignocellulosic material characterizations including cellulose crystallinity determination, holocellulose discrimination, and lignin substructure evaluation. We briefly review the recent studies on wood property enhancement and functional wood-based material development through wood modification including thermal treatment, acetylation, furfurylation, methacrylation, delignification. Subsequently, we highlight the use of the Raman imaging for visualization, spatial and temporal distribution of wood cell wall structure, as well as the microstructure evolution upon functionalization. Finally, we discuss the future prospects of the field. [ABSTRACT FROM AUTHOR]

Cracking, warping, and decaying stemming from wood's poor dimensional stability and durability are the most annoying issues of natural wood. There is an urgent need to address these issues, of which, sustainable and green chemical treatments are favorably welcomed. Herein, we developed a facile method through the incorporation of environmentally friendly biopolymer lignin into wood cells for wood dimensional stability and durability enhancement. Enzymatic hydrolysis lignin (EHL) was dissolved into various solvents followed by impregnation and drying to incorporate lignin into wood cells. Impregnation treatment was developed to incorporate into wood to improve its dimensional stability, durability, and micromechanics. The anti-swelling efficiency reached up to 99.4 %, the moisture absorption decreased down to 0.55 %, the mass loss after brown rot decay decreased to 7.22 %, and the cell wall elasticity as well as hardness increased 8.7 % and 10.3 %, respectively. Analyses acquired from scanning electron microscopy, fluorescent microscopy, and Raman imaging revealed that the EHL was successfully colonized in cell lumen as well as in cell walls, thus improved wood dimensional stability and durability. Moreover, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirmed EHL interaction with the cell wall components, thus the wood mechanical property was not impaired significantly, whereas nanoindentation data indicated even slight mechanical enhancement on the cell walls. This facile approach can improve the wood properties in multiple aspects and remarkably enhance the outdoor performance of modified wood products. In addition, using lignin as a natural modifying agent to improve wood performance will have a great positive impact on the environment. [ABSTRACT FROM AUTHOR]

A simple strategy was introduced to develop fluorescent wood with the ability to alter its color when exposed to both visible and ultraviolet lights. Injecting a combination of europium and dysprosium doped aluminate (EDA; 7–12 nm) nanoparticles and polyester resin (PET) into a lignin-modified wood (LMW) produced a translucent smart wooden window with fluorescence and afterglow emission properties. In order to prevent formation of aggregates and improve the preparation process of transparent woods, EDA must be properly disseminated in the polyester matrix. We analyzed the fluorescent wood samples using a variety of spectroscopic and microscopic methods, including energy-dispersive X-ray (EDX), scanning electron microscopy (SEM), photoluminescence spectra, and hardness tests. We found that the photoluminescent woods had an excitation peak at 365 nm and emission peaks at 437 nm and 517 nm. The translucent luminous woods showed rapid and reversible emission response to ultraviolet light. Fluorescence emission was detected for samples with lower EDA content, and afterglow emission was detected for wood samples with higher EDA content. Increases in EDA content were associated with improvements in water resistance and ultraviolet radiation protection in the EDA@PET-infiltrated wood. [ABSTRACT FROM AUTHOR]

[Display omitted] • Crosslinking with glyoxal led to networks formed by amide, imine, and ether bonds in the lignin structure. • DETA- and EDA-aminated lignin comprised higher nitrogen content. • Green adhesives were developed by the crosslinking of HKL fractions. • DETA-aminated acetone-insoluble fraction exhibited higher shear strength. • Aminated acetone-soluble fraction satisfied the standard for interior application. Hardwood kraft lignin from the pulping industry is burned or discarded. Its valorization was conducted by subjecting fractionation, amination with ethylenediamine, diethylenetriamine, and monoethanolamine, and crosslinking with formaldehyde or glyoxal to obtain bio-based wood adhesives. Acetone-soluble and insoluble hardwood kraft lignin were prepared and subjected to amination and then crosslinking. Fourier transform infrared, 13C NMR, 15N NMR, and X-ray photoelectron spectroscopy results revealed successful amination with amide, imine, and ether bonds and crosslinking of all samples. Hardwood kraft lignin aminated with diethylenetriamine/ethylenediamine and crosslinked using glyoxal exhibited excellent results in comparison with samples crosslinked using formaldehyde. Acetone-insoluble hardwood kraft lignin aminated and crosslinked using diethylenetriamine and formaldehyde, respectively, exhibited excellent adhesion strength with plywood, satisfying the requirements of the Korean standards. The amination and crosslinking of industrial waste hardwood kraft lignin constitute a beneficial valorization method. [ABSTRACT FROM AUTHOR]

The pre-hydrolysis liquor (PHL) produced during pulp dissolution and biomass refining is mainly composed of hemicellulose and lignin, and it is a potential source for production of value-added materials and platform chemicals; however, their utilization has been a serious challenge. In this study, we proposed a green and simple strategy to simultaneously prepare size-controlled functional lignin nanoparticles (LNPs) and levulinic acid (LA) from PHL as the raw material. The as-prepared LNPs exhibited remarkable stability thanks to the presence of saccharides with abundant oxygen-containing groups and surface charges, which prevented aggregation and maintained long-term storage stability. Trace amounts of the LNPs (≤ 0.2 wt%) could stabilize various Pickering emulsions, even with oil-to-water ratios as high as 5:5 (v /v). Subsequently, the remaining PHL was directly used to produce LA without adding a catalyst; under optimal conditions (160 °C and 1 h), the yield of LA was 56.3 % based on the dry saccharide content in the raw PHL. More importantly, p -toluenesulfonic acid (p -TsOH), the only reactive reagent used during the entire preparation process, including the two preparation steps of the LNPs and LA, was reusable, and the recovery rate was >70 % after five cycles. Overall, this green and simple strategy effectively and comprehensively utilized the PHL and showed potential for producing biobased nanomaterials and platform chemicals. [Display omitted] [ABSTRACT FROM AUTHOR]

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 AlCl 3 -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. [Display omitted] • The microcosmic distribution and changes of lignin were visualized investigated. • Structural changes of lignin during the integrated HTP-DES process were illustrated. • Synergistic HTP-DES method was developed for fractionation of lignin. • High yields of tailored lignin nanoparticles were obtained. • Possible chemical variations of lignin during the synergistic HTP-DES were investigated. [ABSTRACT FROM AUTHOR]

In the present study, lignin and lignin-carbohydrate complex (LCC) constituting the cell wall structure of sesame hulls were investigated to explore novel techniques of dehulling. Milled wood lignin (MWL), Björkman LCC, and acid-soluble LCC (LCC-AcOH) were extracted from sesame hulls and characterized by carbohydrate composition analysis, molecular weight analysis, UV–vis spectroscopy, FT-IR, thermal analysis, Py-GC/MS, 2D HSQC NMR, and 31P NMR. The results showed that rhamnose accounted for the largest proportion of the lignin and LCC fractions, followed by glucose. Björkman LCC had the largest molecular weight, MWL had the smallest molecular weight, and LCC-AcOH had the largest polydispersity index. The lignin of sesame hulls consisted of syringyl (S), guaiacyl (G), p -hydroxyphenyl (H), and caffeyl alcohol (C) units. The most abundant monomer was guaiacyl (G), followed by caffeyl alcohol (C). C-type lignin is a new type of lignin that is different from the three traditional lignin monomers. The major lignin-linked bonds in the MWL and LCC-AcOH were β-O-4′ and β-β′, and β-5′ bonds were present in the Björkman LCC. The major LCC chemical bonds in the three fractions were PhGly. These findings will provide the factual basis for exploring different dehulling methods to enhance the quality of sesame products. • Lignin and LCC were isolated from the sesame hull firstly. • G/S-lignin and C-lignin were present in the sesame hulls. • The lignin-carbohydrate bonds in MWL, LCC-AcOH, and LCC were only PhGly. • The content of G-type lignin in sesame hulls was the highest, followed by C-type. [ABSTRACT FROM AUTHOR]

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 β- O -4, β-β, β- 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. • The synergistic HTP-DES pretreatment can effectively prepare XOS and LNPs from EU wood. • XOS with high yield (33.88%) can be prepared under relatively mild condition. • The effects of pretreatments on the structural changes of lignin were investigated. • LNPs fraction has a homogeneous and narrow size distribution (ranged from 60 nm to 110 nm). [ABSTRACT FROM AUTHOR]

To reveal the existence of p -hydroxyphenyl (H) units in compressed wood lignin, four different milled wood lignins were extracted using Pinus massoniana Lamb compressed wood, Pinus massoniana Lamb normal wood, and sugarcane bagasse as raw materials. Then, three dehydrogenation polymers (DHPs) were synthesized using coniferyl/ p -coumaryl alcohol as raw materials to reveal the interunit linkages of H units. The lignin and DHP samples were systematically characterized by 1H, 13C, 2D HSQC, and 31P NMR techniques. Compared with the opposite wood milled wood lignin (OW-MWL) and the normal wood milled wood lignin (NW-MWL), the compressed wood milled wood lignin (CW-MWL) contained a large amount of H units, and the H/G ratio and the p -hydroxyphenyl OH group contents were 0.15 and 1.09 mmol/g, respectively. Through the characterization of CW-MWL and DHPs, it was revealed that p -hydroxyphenyl units mainly coupled with other units by β-O-4, β-β, and β-5 linkages. Compared to the sugarcane bagasse milled wood lignin, it was clearly demonstrated that the H unit rather than p -coumarate ester occurred in CW-MWL. This study comprehensively explored the structural characteristics and linkages of H units in compress wood lignin, and provided useful information for revealing the participation of H units in the construction of lignin macromolecules. • More p -hydroxyphenyl unit was quantified in the compressed wood lignin. • More p -hydroxyphenyl units lead to a decrease of β-O-4 and β-5 linkages. • The main interunit linkage of G-DHP, H-DHP, and GH-DHP were β-O-4, β-β, β-5. • The p -hydroxyphenyl unit was presented as β-O-4, β-β, β-5 in the compressed lignin. [ABSTRACT FROM AUTHOR]

The rational design of sound absorption boards made of wood materials is an exciting area of research. This article describes a simple and inexpensive method to increase the sound absorptions capacity of Malas hardwood (Homalium foetidum Roxb.) using ammonium persulfate treatment. The reaction parameters such as the concentration of ammonium persulfate and reaction time were optimized. The results of X-ray photoelectron spectroscopy, X-ray diffraction, attenuated total reflectance–Fourier transforms infrared spectroscopy, and scanning electron microscopy demonstrated that ammonium persulfate could significantly affect carbohydrate polymers and lignin of wood by improving oxygen functionalities. The quantitative analysis of carbohydrate polymers (hemicellulose and cellulose) and lignin were evaluated. These changes in carbohydrate polymers and lignin enhanced the air permeability (83.6%) and average sound absorption coefficient at each frequency range 500–1000 Hz (2.6%), 1000–2000 Hz (4.9%), 2000–4000 Hz (17.4%), and overall 500˗6400 Hz (20.8%) compared to the control samples. These results could be beneficial for new research and wood-based sound absorption materials to regulate the acoustic environment in houses. • Ammonium persulfate changes carbohydrate polymers and lignin. • The modified biopolymers enhanced the porosity (1.2%) and gas permeability (83.6%). • The average sound absorption coefficient increases 20.8% at 5–6.4 kHz. • The ammonium persulfate method is facile and inexpensive. [ABSTRACT FROM AUTHOR]

Given the current scarcity of wood fiber resources, it is imperative to investigate the potential of employing weak alkaline hydrogen peroxide for bleaching high-yield pulp (HYP) to meet the increasing demands for paper and paperboard. This work presents an investigation into the characteristics of triploid poplar chemi-thermomechanical pulp (CTMP) hydrogen peroxide bleaching, including the brightness, bleaching yield, bulk, physical strength, and contents of carbohydrates and lignin. The findings show that partial substitution of MgO for NaOH as an alkali source could improve the yield and bulk of the bleached CTMP. When the substitution ratio of MgO for NaOH reached 75 %, the brightness of 74.62 % ISO for the bleached pulp dropped by only 0.47 percent points but the bulk of 2.21 cm3/g increased by 5.74 % compared to those of the control, respectively. Meanwhile, the yield of the bleached CTMP could reach 93.45 %, 5.07 percent points higher than that of the control. The results would be of benefit to the HYP enterprises concerned. • Substitution of MgO for NaOH fulfilled the criteria for achieving good brightness. • Substitution of MgO for NaOH improved the yield of bleached CTMP and bulk. • Adding MgO increased the content of carbohydrate and lignin in the bleached pulp. • The surface lignin content would increase with raising the ratio of MgO-to-NaOH. [ABSTRACT FROM AUTHOR]

Five deep eutectic solvents (DES) were evaluated to disrupt Paulownia wood structure to produce bioethanol and lignin. The DES formulated with choline chloride:lactic acid provided the most promising result. Temperature (110–130 °C), residence time (30–120 min), molar ratio (1:2–1:9), and liquid-to-solid ratio (8–15 mL/g) were optimized for cellulose recuperation (93% retained in the solid phase) and lignin removal (94% delignification yield). The spent solid was used for bioethanol production, achieving up to 43.6 g ethanol/L (89.7% ethanol yield). Lignin (84% of purity) was isolated from the black liquor and thoroughly characterized by FTIR, 1H NMR, TGA-DTG and SEM, while the liquor after lignin precipitation was chemically characterized for monomers/oligomers, total phenolic content, antioxidant activity and phytochemical profile (highlighting the presence of 25.06, 10.21 and 2.51 mg of syringaldehyde, vanillin and 3,4-dihydroxibenzoic acid per g of initial biomass). Overall, this study show that DES pre-treatment is a promising strategy for simultaneous lignin extraction and cellulose digestibility enhancement. • DES pretreatment enabled the removal of 94% of lignin and recovery of 93% glucan. • 0.1% NaOH washing of the solid improved enzymatic susceptibility from 44% to 93%. • 89.7% ethanol yield (43.61 g/L) was reached from pretreated Paulownia wood. • Isolated lignin (purity ≈84%) was characterized by FTIR, 1H NMR, TGA-DTG and SEM. • 9.31 kg of xylan and 3.03 kg of phenolics (per 100 kg Paulownia) were recovered. [ABSTRACT FROM AUTHOR]

Superheated steam treatment has been shown to be an efficient strategy for enhancing the dimensional stability of compressed wood. This study evaluated the hygroscopic behavior of surface compressed (SC) wood subjected to superheated steam treatment (SHTSC wood) at varying steam pressures (0.1 MPa, 0.3 MPa, 0.5 MPa, and 0.7 MPa). As the steam pressure increased, the equilibrium moisture content (EMC) of SHTSC wood showed a gradual decrease throughout the hygroscopic range, indicating improved hygroscopic stability. The reduction in EMC for SC wood was associated with a decrease in polylayer moisture content (M s) from 0% to 95% RH, while the EMC reduction for SHTSC wood was attributed to the combined effect of diminished monolayer (M h) and M s. The superheated steam treatment resulted in a range of chemical alterations in the SHTSC wood, including a decrease in hemicelluloses content and the quantity of sorption sites (–OH, C–O groups). Concurrently, there was a relative augmentation in the content of cellulose and extractives, alongside a heightened degree of lignin cross-linking. Furthermore, the superheated steam treatment also affected the cellular structure of the SHTSC wood, resulting in an increased ratio of macropores to mesopores, as well as the formation of microcracks within the cell wall. These changes became more pronounced as the steam pressure elevated, contributing to the reduced hygroscopic characteristics and improved dimensional stability of SHTSC wood. • The hygroscopic behavior of surface compressed wood subjected to superheated steam treatment was revealed. • High superheated steam pressure was more conducive to improve the hygroscopic stability. • Changes of chemical components and cellular structure in SHTSC wood were the main reasons for improved hygroscopicity. [ABSTRACT FROM AUTHOR]

Lignin and cellulose are crucial component in secondary cell walls (SCW), while the detailed biosynthesis pathway for these two elements and their regulatory mechanisms in Ginkgo biloba are unclear. Here, we conducted a comparative transcriptome in seven wood-forming tissues to explore SCW formation mechanism. Seven genes (3 CCRs (cinnamoyl-CoA reductases: GbCCR1–5 , GbCCR1–1 , GbCCR1–2), 2 CSEs (caffeoylshikimate esterases: GbCSE2 , GbCSE5), 1 PER (peroxidase: GbPER43–2), and 1 PAL (phenylalanine ammonia-lyase: GbPAL2)) were identified as candidates in encoding constitutive enzymes for tissue-specific lignin biosynthesis. While three genes (FRK (fructokinase: GbFRK), otsB (trehalose 6-phosphate phosphatase: GbTPP6), and HXK (hexokinase: GbHXK1)) were identified as candidates in cellulose biosynthesis. A weighted co-expression network analysis (WGCNA) revealed that 16 transcription factors (TFs) involved in tissue-specific lignin biosynthesis, which were co-expressed with 35 deferentially expressed genes encoding structural gene in lignin monomer biosynthesis for seven wood-forming tissues. Further, 16 TFs were predicted to be associated with abiotic stress and development, of which, 5 bHLHs were co-expressed with 6 candidate genes previously identified in lignin biosynthesis. Self-activation assay showed that 3 bHLHs were transcriptional activators. Yeast one-hybrid (Y1H) proved that GbbHLH112 exhibited direct binding to the GbPER43–2 promoters, leading to the activation of GbPER43–2 expression, supporting our identification for candidates in lignin biosynthesis. Our finding provided basic reference in exploring tissue-specific lignin biosynthesis, which will enhance additional research of transcription factor regulation mechanisms in Ginkgo's wood lignin biosynthesis. • Seven genes were considered as candidate structural genes in tissue-specific lignin biosynthesis. • GbFRK , GbTPP6 , and GbHXK were good candidates in cellulose biosynthesis. • WGCNA revealed 16 TFs related to lignin biosynthesis. • 3 bHLHs were transcriptional activators involved in lignin biosynthesis. • GbbHLH112 can bind to the promoter of GbPER43–2 , leading to the activation of GbPER43–2 expression in lignin biosynthesis. [ABSTRACT FROM AUTHOR]

Wood materials incorporating new properties are of great interest, especially for advanced applications such as sustainable optics and photonics. In this work we describe a wood functionalization approach, comprising the incorporation of artificial chemiluminescent systems (phenyl oxalate ester‑hydrogen peroxide-fluorophore, and luminol-ferricyanide), resulting in light-emitting wood. By a detailed characterisation of the light emission features we point out the complex interaction between wood scaffold and chemiluminescent systems, especially the quenching effect of wood extractives (for the TCPO-H 2 O 2 -fluorophore system) and lignin (for the luminol-ferricyanide system). Moreover, we take advantage of the intrinsic anisotropic porosity and capillarity of wood tissue to study the chemiluminescent front propagation. Our results may inspire the development of novel light-emitting wood materials for a variety of applications, from fundamental studies of water uptake in wood to sensors and even design elements. [Display omitted] [ABSTRACT FROM AUTHOR]

Ultraviolet (UV)-induced discoloration and cracking pose formidable challenges for thermally modified wood (TMW) when used in outdoor applications. Herein, we propose a novel pretreatment strategy using deep eutectic solvent (DES) to enhance the weathering resistance of TMW. DES-assisted TMW (DES-TMW) was prepared by coating wood with choline chloride/citric acid (CA) DES, followed by thermal modification. During the DES-assisted thermal modification process, the cross-linking of the lignin network in DES-TMW was increased as a result of lignin self-polymerization, cross-linking with autologous molecules and furfural, as well as esterified connections caused by CA. This in-situ modification reduces the quantity of photosensitive phenolic hydroxyl groups within lignin by forming cross-linked structures, reducing phenoxy free radical generation during the weathering and obstructing chromophores production pathways, thus enhancing the photostability of lignin. Consequently, the DES-TMW exhibited remarkable resistance to discoloration and cracking compared to TMW. These findings provide evidence that our strategy can effectively enhance the photostability of wood, thereby contributing to the development and production of sustainable outdoor wood products capable of withstanding changing weather conditions. [Display omitted] • Eco-friendly DES-assisted method for photostable thermally modified wood (TMW). • In-situ lignin modification during treatment created stable cross-linked structures. • DES-assisted method inhibited chromophore formation and photodegradation of lignin. • DES-assisted TMW (DES-TMW) showed excellent resistance to color change and cracking. [ABSTRACT FROM AUTHOR]

In order to explore the influence of wood types on formation of polycyclic aromatic hydrocarbons (PAHs) in traditional smoked and grilled meat products, the effect of lignin in woods on formation of PAHs was investigated in meat model systems. The results showed that PAHs formation was much dependent on the heating conditions. The addition of lignin led to significantly increased PAHs, which being connected with lignin structure. In comparison, the formation of PAHs was more facilitated by lignin with G structure than that with G/S structure. However, further study of adding lignin precursors demonstrated that lignin precursors with S structure were more favorable to the formation of PAHs than those with G structure. It was proposed that the relative content and activity of G/S structure of lignin in wood played a significant role in the formation of PAHs, which might provide theoretical reference for inhibition of PAHs fundamentally. • The influence of wood types on PAHs formation was investigated focused on the effect of lignin. • The PAHs formation was more facilitated by lignin dominated with G structure than that with G/S structure. • The relative content and activity of G/S structure of lignin in wood were vital for PAHs formation. [ABSTRACT FROM AUTHOR]

Superhydrophobic coatings are developed rapidly due to the eye-catching versatility, but still suffer from problems of insufficient environmental protection, poor heat resistance, and weak UV resistance. Here, a stable and versatile lignin/calcium carbonate (CaCO 3)/chitosan (CS) superhydrophobic coating on the wood (beech) could be successfully prepared by simple one-step spay. In the coating system, enzymolysis lignin was employed as the main materials to construct surface rough structure, which was enhanced with both CaCO 3 and CS, methyltrimethoxysilane (MTMS) and hexadecyltrimethoxysilane (HDTMS) as the hydrophobic modifiers and polydimethylsiloxane (PDMS) as the adhesive. The resulted coating shows good superhydrophobicity (water contact angle of 161.1° and sliding angle of 8°), as well as excellent heat resistance (superhydrophobicity still maintaining under 200 °C), UV resistance (10 h of high-intensity UV irradiation). In addition, when PU sponge was used as the substrate, the stable oil-water separation could be achieved. In view of the good performance and simple preparation, the superhydrophobic coating displays a good application prospect. • The system has superhydrophobicity and excellent abrasive resistance. • The ingenious combination of calcium carbonate and lignin is the key to its excellent abrasive resistance. • The system shows superior functionality on different substrates. [ABSTRACT FROM AUTHOR]

This study aims to delve into the impact of long-term multi-strain pretreatment on the thermochemical characteristics of paulownia. The nine-month experimental analysis reveals that the fourth month marks a crucial turning point in the pretreatment process. From Stage I (0–4 months) to Stage II (4–9 months), the pyrolysis temperature range continuously narrows, reducing a maximum of 31.47%. The char yield initially increased by 10.25% and then decreased by 6.95%. Calorific value showed a slow initial decline of 3.98–4.08%, followed by a subsequent increase of 7.66%. The ignition point continued to rise by 5.61%− 5.78%. The compositional experimental results indicate that in the first stage, strain primarily depolymerize the high-polymer lignin, resulting in a decrease in calorific value. The increase in the relative content of syringyl lignin (S) contributes to the rise in char yield. In Stage II, the S units are converted into guaiacyl lignin (G), which has a lower char yield, while the exposed hemicellulose and cellulose undergo severe erosion. The relative content of lignin and enzymatic products with stubborn structures increases, leading to an increase in calorific value. However, the higher breaking temperature of bonds in these structures results in a continuous increase in the ignition point. This study clearly establishes that after nine months of pretreatment, the paulownia exhibits characteristics of rapid pyrolysis, high calorific value and ignition point, which provides a reliable basis for uncovering the potential reuses of paulownia. • Various fungi and bacteria were used to pretreat paulownia. • The multi-strain pretreatment time was up to nine months. • The fourth month marks a crucial turning point in the pretreatment process. • After pretreatment, the pyrolysis temperature range was shortened by 31.47%. • Calorific value decreased in Stage I and increased in Stage II. [ABSTRACT FROM AUTHOR]

A series of novel waterborne lignin-based epoxy resin emulsions (WLEPs) were successfully synthesized, and then the WLEPs were cured with polyamide (PA) to give formaldehyde-free wood adhesives with high-performance. The chemical structures and properties of WLEP emulsions were determined. The effects of the emulsifiers on thermal and mechanical properties of the adhesives were investigated, and the potential application of WLEPs in the formulation of plywood were also evaluated. The results demonstrated that the WLEP dispersions presented excellent storage stability (>180 days) with their viscosities range from 110 mPa·s to 470 mPa·s and particle sizes in the range of 321–696 nm, which were beneficial for the fluidity and permeability of the wood adhesives. Furthermore, the thermal and mechanical properties of adhesives could be tuned effectively by controlling the length of PEG chains. The adhesive bearing PEG 6000 exhibited the highest tensile strength of 24.0 MPa and Young's modulus of 1439 MPa. Notably, the plywood prepared with the resulting adhesives displayed good bonding performance, especially water resistance, which were much higher than the national standard requirement for exterior-grade plywood type I. These results indicated that the WLEPs could be used as sustainable alternatives for traditional formaldehyde-based wood adhesives in practical applications. [Display omitted] • A series of waterborne lignin-based epoxy resin emulsions (WLEPs) with excellent storage stability were successfully synthesized without using any solvent. • The adhesives based on WLEPs exhibited good fluidity, wettability and permeability on wood surface. • The thermal and mechanical properties of adhesives can be easily tuned by adjusting the flexible segments. • The plywood prepared with the resulting adhesives demonstrated good bonding performance, especially water resistance, exceeded the national standard requirement for exterior-grade plywood type I. [ABSTRACT FROM AUTHOR]

When wood is used as a stressed component of building materials, the parts most prone to failure are the upper and lower surfaces which can be called the weak structure. In a hydrothermal environment, lignin and hemicellulose in wood readily soften and dissolve, thus leading to their designation as the weak structure. The weak structures results in the wood having a low strength. In this paper, the sandwich beam material can be obtained by two steps from the skin self-reinforcement method, whereby the weak structure of the wood surface was removed by the delignification, and then the wood surface was densified. The authenticity of the sandwich structure is proved by a scanning electron microscope (SEM) and density profile analysis. When the moisture content (MC) is 10 %–12 % and the mass loss ratio is 23.04 %, the optimal resilience of the sandwich beam is only 1 %, the maximum modulus of rupture (MOR) and modulus of elasticity (MOE) are 1.42 and 2.1 times greater than those of natural wood, respectively. This finding shows that our method strengthens the weak structure of natural wood, which has good flexural performance and springback ratio. [Display omitted] [ABSTRACT FROM AUTHOR]

A deep understanding of the inherent roles of wood polymers such as cellulose, hemicelluloses, and lignin in the hierarchical structure of wood is of key importance for advancing functional wood-based materials but is currently lacking. To address this gap, we clarified the underexplored contributions of wood polymer assemblies to the structural support and compressive properties of wood by chemically removing polysaccharides or lignin from wood blocks of a conifer Cryptomeria japonica. Compositional and structural evaluations revealed that cellulose, hemicelluloses, and lignin contributed to the dimensional stability of wood, especially that the polysaccharide network at cell corners sustained the honeycomb cell structure. Wood polymer assemblies featuring the anatomical structure of wood were also evaluated in terms of compressive properties. The modulus and strength reflected the density and anisotropy, whereas fracture behavior was well characterized by each wood polymer assembly through the classification of stress–strain curves based on principal component analysis. The difference in fracture behaviors indicated that the rigid lignin and flexible cellulose assemblies, possibly mediated by hemicelluloses, complementarily determine the unique compressive response of wood. These findings enable the adjustment of wood functionality and the selection of composite components for wood modification while inspiring the development of novel wood applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Adhesives are used extensively in the wood industry. As resource and environmental issues become increasingly severe, the development of green and sustainable biomass-based adhesives has attracted increasing attention. In this work, a green wood adhesive is developed from poly(vinyl alcohol) and lignin with molecular designs of lignin extending beyond those in nature. The lignin undergoes extraction from corncob residue, aldehydration, and phenolisation (phenol, resorcinol, and catechol) to significantly increase the phenolic hydroxyl groups (over 7.92 mmol/g), which has the effect of enhancing the hydrogen bonding force between the adhesive and the wood, thereby greatly improving adhesive performance. Compared with pure PVA, polyphenol lignin-containing PVA showed improved adhesion strength and hydrophobicity. PVA/resorcinol-lignin has the significantly improved wood lap shear strength (6.27 MPa, 77.6 % improvement) and hydrophobicity (almost 100 % increase in wet shear strength). This research not only provides a green and high-performance alternative raw material for wood adhesives but also broadens the path for large-scale application of biomass. • The content of phenolic hydroxyl groups of the modified lignin reaches 7.92 mmol/g. • A higher content of phenolic hydroxyl groups shows an enhanced adhesive strength. • The resorcinol structure exhibited higher adhesion strength than catechol. • PVA/resorcinol-lignin exhibits a high wood lap shear strength of 6.27 MPa. [ABSTRACT FROM AUTHOR]

We report a facile synthesis for lignin/titanium dioxide (TiO 2) nanoparticles (LT NPs) at room temperature by confining assembly of lignin macromolecules. The LT NPs had a uniform nanosize distribution (average diameter ∼ 68 nm) and were directly employed as multifunctional nanofillers to reinforce a waterborne polyurethane wood coating (WBC). X-ray diffraction, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy revealed the mechanism by which formed TiO 2 confined lignin assembly. The LT NPs considerably increased the tensile strength of a WBC film from 16.3 MPa to 28.1 MPa. The WBC–LT NPs exhibited excellent ultraviolet (UV) A and UVB blocking performances of 87 % and 98 %, respectively, while maintaining 94 % transmittance in the visible region. Incorporating LT NPs into the WBC enhanced the coating performance (the hardness, adhesion, and abrasion resistance) on wood substrates. A quantitative color and texture analysis revealed that the LT NPs increased the decorativeness of actual wooden products. After nearly 1800 h of UV irradiation, wood coated with the WBC–LT NPs exhibited good color stability, where the original color remained unchanged or even became brighter. In this study, value-added valorization of lignin is enabled by using organic–inorganic nanofillers and insights are gained into developing multifunctional WBCs. [ABSTRACT FROM AUTHOR]

Thermoplastic materials can be obtained through solvent free wood esterification with fatty acid using trifluoroacetic anhydride (TFAA) as promoter. This study aims to investigate the mechanism of wood thermoplasticization mechanism by understanding the role of each wood component in esterification. High accessibility for acylation was found in cellulose indicated by the highest weight percent gain (WPG), followed by lignin and hemicelluloses. However, significant chemical structural changes were recorded for each spruce wood components observed by Fourier-transform infrared spectroscopy (FTIR) and cross-polarization/magic angle spinning solid state nuclear magnetic resonance (CP/MAS 13C NMR), promoting thus the improvement of their thermal properties detected by (thermogravimetric analysis) TGA and (differential scanning calorimeter) DSC. Cellulose as a major component wood played an important role in wood plasticization, indicated by the low softening temperature before degradation recorded by (thermomechanical analysis) TMA. Hemicelluloses presenting lower WPG, showed the same effect as cellulose on thermoplasticization supported by the low softening temperature observed by TMA and (scanning electron microscope) SEM. Acylated lignin did not show thermoplastic properties, but resulted in important hydrophobic aspects of materials. [Display omitted] • Thermoplasticization mechanism of wood was investigated by acylation of its pure wood components. • Significant chemical structure was observed for each wood components. • Cellulose play an important role in wood thermoplasticization • Hemicellulose presenting lower WPG, showed the same thermoplasticity as cellulose • Lignin did not show thermoplastic properties, but resulted in important hydrophobic aspects of materials [ABSTRACT FROM AUTHOR]

• SWCNHs were used with wood flame retardancy for the first time. • The small amount of flame retardant used achieves a high level of flame retardancy. • Combination of flame retardant and delignification for high properties. Fir wood is widely used in construction, however its thermal degradability and flammability pose significant challenges to its safe use. In this work, we used a new carbonaceous nanomaterial called single-walled carbon nanohorns (SWCNHs), in combination with lignin and potassium carbonate to prepare a composite flame retardant and investigated the effect of different pretreatments on the flame retardant effect of fir wood. After delignification pretreatment and vacuum impregnation of fir wood with the flame retardant, the pk 1 -HRR and the pk 2 -HRR decreased by 37.59 % and 25.07 %, THP decreased by 55.71 %, TSP decreased by 59.81 %, COP significantly decreased by 74.02 %, char residual weight increased by 14.11 % compared with new wood (NW), and LOI reached 28.8 %. And the composite flame retardant forms a char layer during burning, which acts as a protective layer. This provides new insights into the application of SWCNHs in wood flame retardancy. [Display omitted] [ABSTRACT FROM AUTHOR]

With the high phenolic hydroxyl content and excellent bioactivity, low molecular weight lignin (LMW-Lignin) holds tremendous potential for various applications in energy storage and antibacterial materials. However, conventional sources of lignin currently available are characterized by large molecular weights, and many of their active functional groups remain unreleased, limiting their exploitation for potential applications. In this study, we investigated the inhibition effect of methanol on the recondensation of lignin fragments under a hydrothermal system of methanol/sodium hydroxide, using eucalyptus wood flour as the raw material. Our findings revealed that, in the hydrothermal alkaline system,·OCH 3 free radicals formed from methanol can effectively target and react with the active sites (C α and C β) on the dissolved lignin side chains, resulting in the formation of stable methoxyl structures and preventing the formation of C-C bonds and polycondensation of dissolved lignin. Optimized conditions, including 20% CH 3 OH (methanol content), 14% NaOH (sodium hydroxide content), and a reaction temperature of 160 ℃, led to a weight-average molecular weight of 1478 for the lignin product, with a yield of 62.90%. • LMW-Lignin was prepared through a one-step process using eucalyptus powder as raw material. • The lignin with molecular weight of 1478 was obtained by adding methnol prevents the aggreation of lignin in an alkaline environment. • The inhibition effect of methanol on the recondensation of lignin fragments was investigated. [ABSTRACT FROM AUTHOR]

Heat treatment increases the decay resistance of wood by decreasing its hygroscopicity, but the wood material remains degradable by fungi. This study investigated the degradation of heat-treated wood by brown rot fungi, with the aim of identifying fungal-induced hygroscopicity changes that facilitate degradation. Scots pine sapwood samples were modified under superheated steam at 200 and 230 °C and then exposed to Coniophora puteana and Rhodonia placenta in a stacked-sample decay test to produce samples in different stages of decay. Sorption isotherms were measured starting in desorption from the undried, decaying state to investigate their hygroscopic properties. Although there were substantial differences in degradative ability between the two fungi, the results revealed that decay by both species increased the hygroscopicity of wood in the decaying state, particularly at high relative humidity. The effect was stronger in the heat-treated samples, which showed a steep increase in moisture content at low decay mass losses. The reference samples showed decreased hygroscopicity in absorption from the dry state, while the heat-treated samples still showed an increase at low mass losses. Near infrared spectroscopy showed that the early stages of decay were characterised by the degradation of hemicellulose and chemical changes to cellulose and lignin, which may explain the increase in hygroscopicity. The results provide a new perspective on brown rot decay and offer insight into the degradation of heat-treated wood. • Heat-treated and reference samples were degraded by brown rot fungi. • Sorption isotherms were measured starting in desorption from the undried state. • Brown rot degradation increased moisture content in desorption in all samples. • Moisture content of heat-treated samples showed an increase also in absorption. • Near infrared spectroscopy indicated changes in hemicellulose, cellulose and lignin. [ABSTRACT FROM AUTHOR]

Lignin, the second most abundant organic polymer on earth, is one of the primary causes of the viscoelastic behavior of plants. An accurate characterization of its viscoelastic properties is essential for predicting the time-dependent response of natural materials, including wood and plant fibers, and for advancing lignin-based materials and their production methods, such as 3D printing of biocomposites. To enrich the still rather sparse knowledge on the viscoelasticity of lignin, we re-evaluate nanoindentation relaxation tests performed on five hot-pressed technical lignins extracted from different feedstocks, using three different extraction methods. The viscoelastic indentation problem is addressed using the method of functional equations combined with the homogenization theory to account for the production-induced porosity. This evaluation procedure allows for quantitatively assessing the viscoelastic properties of lignin, which can be very accurately described by an isochoric four-parameter Burgers model. Remarkably, the viscoelastic properties of all tested lignins are practically identical and independent of the feedstock and the extraction processes. [Display omitted] • The viscoelastic nature of lignin is deciphered experimentally for the first time. • Nanoindentation relaxation tests assessed via micromechanics and functional equations. • Lignin is viscoelastic and exhibits pronounced short-term viscous deformations. • Neither feedstocks nor extraction processes affect lignin's viscoelastic properties. [ABSTRACT FROM AUTHOR]

Tension wood is a type of defect of wood, however, it has some especial character and structure. In this study, cellulase lignin structures in normal and tension wood of Poplar 107 (Populus × euramericana cv. '74/76') were compared using ultraviolet (UV), Fourier transform infrared (FT-IR), Raman and magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC) and elemental analysis. The results showed that the lignins in both normal and tension wood were dominated by syringyl units, followed by guaiacyl and p -hydroxyphenyl units. The FT-IR result presented that the relative intensity of syringyl units in normal and tension wood were 0.87 and 0.90. The contents of aliphatic hydroxyl, methoxyl, condensed phenolic hydroxyl and carboxyl of lignin in tension wood were higher than those of phenolic hydroxyl groups and β-5. The contents of β-O-4, β-β and β-1 in tension wood were similar with those in normal wood. The average per-C 9 -unit formulae of the lignin in normal and tension wood of Poplar 107 were C 9 H 7.21 O 1.79 (OH) 1.17_x0001_ (OCH 3) 1.55 and C 9 H 7.23 O 1.76 (OH) 1.25_x0001_ (OCH 3) 1.62 , respectively. [ABSTRACT FROM AUTHOR]

The research on hardwood lignin is quite limited for lignin-based adhesives due to its heterogeneity and chemical complexity compared with those of softwood and non-wood lignin. Herein, a novel approach of producing entirely bio-based and nontoxic wood adhesives by self-crosslinking of industrial hardwood kraft lignin (HKL) is presented to replace formaldehyde-based resin adhesives. The key issues of converting HKL to bio-wood adhesive are their low reactivity for crosslinking capacity and high heterogeneity. For this, HKL extracted from industrial black liquor was acetone fractionated to reduce its heterogeneity, resulting in acetone-soluble HKL (AS-HKL) and acetone-insoluble HKL (AI-HKL), which were then glyoxylated to facilitate crosslinking and form a three-dimensional network structure. Lignin samples were analyzed by gel permeation chromatography (GPC), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), 31P nuclear magnetic resonance (31P NMR), solid state 13C cross-polarization/magic angle spinning (13C CP/MAS) NMR, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The adhesive strength of lignin-based adhesives was evaluated by determining the tensile shear strength of plywood. In this current research the chemical structure changes especially the crosslinked structure and adhesion performance were investigated. Results showed that the self-crosslinking was successfully formed by ether bonds formation between glyoxalated lignin. Also, the self-crosslinked acetone insoluble hardwood kraft lignin fractionation (AI-HKL) showed the best adhesion performance. FTIR, XPS and 13C CP/MAS NMR spectra revealed new peaks and ether bonds in the glyoxylated lignin. Therefore, these results indicate a successful self-crosslinking of the hardwood kraft lignin after acetone fractionation and glyoxalation for adhesives via network formation. The glyoxalated AI-HKL (AI-HKL–GLY) exhibited the highest viscosity and provided the best plywood adhesion strength (0.8 MPa) among the adhesives, and showed a good potential as wood adhesives. Thus, the results suggest that the self-crosslinking of hardwood kraft lignin after a proper fractionation and glyoxalation is a promising approach of developing lignin-based bio-adhesives for wood bonding. [Display omitted] • Totally green adhesives were developed by self-crosslinking of fractionated and glyoxalated hardwood kraft lignin. • Self-crosslinking was successfully formed by ether bonds between the glyoxalated lignin. • The self-crosslinked lignin showed better thermal stability than the control. • The self-crosslinked lignin from acetone insoluble fraction showed the best adhesion in plywood. [ABSTRACT FROM AUTHOR]

Renewable resources such as wood are an important candidate towards the replacement of fossil-based materials with bio-based materials. Lignin, comprising up to 40% of woody biomass, has shown great potential in the preparation of nanoparticles (LNPs), which can be used in diverse material applications. Typically, LNPs are prepared from technical lignins, deriving from pulping processes. Their formation is thought to be driven by the hydroxyl content and molecular weight of lignin. However, other equally important parameters are the monolignol composition and the concentration of lignin used. In this study, we used native-like lignin fractions from hardwood and softwood to investigate the impact of lignin structure on LNP formation. We identified a synergistic effect between π-π stacking and hydroxyl group content in nanoparticle formation. Our LNPs exhibited different morphologies, including compact, collapsed spheres, and 'snowman' aggregates. The results described herein provide an in-depth perspective on the formation and structure-property relationship of LNPs from native-like lignin fractions. With this study we aim to promote biorefinery concepts, in which the lignin structure is preserved during extraction. • Lignin was extracted from softwood and hardwood using a green and mild protocol. • Native-like lignin populations were used for nanoparticle preparation. • Lignin nanoparticles were prepared with the anti-solvent precipitation method. • Properties of lignin populations were correlated to nanoparticle morphology. [ABSTRACT FROM AUTHOR]

In this study, the efficient extraction of lignin from wood meal using a deep eutectic system (DESys) was explored, and the obtained lignin was characterized. The impact of various factors, such as the type of DESys components, extraction time, temperature, water content, and solid-liquid ratio, on the lignin extraction process was systematically investigated. The results indicated that a DESys with a carboxylic acid as the HBD provided the highest lignin extraction efficiency. The obtained lignin was characterized in terms of its molecular weight distribution, elemental composition, functional groups, crystalline structure, and thermal stability. The results showed that the lignin obtained by DESys-based extraction had similar properties to lignin extracted using traditional method. Additionally, the study examined the utilization of the residue left after lignin extraction for the adsorption of cationic pollutants, such as the cationic dye neutral red (NR). The residue was found to contain carboxyl groups, which enabled it to adsorb NR efficiently. The kinetic and thermodynamic models suggested that the adsorption was a chemisorption process. Furthermore, the residue showed selective adsorption for cationic dye over anionic dye. This selectivity was attributed to interactions between the residue's functional groups and the cationic dye molecule. Overall, this study provided a sustainable and comprehensive approach to lignin extraction from lignocellulosic biomass using DESys. It also demonstrated the potential of using the residue from the extraction process for the removal of cationic pollutants from wastewater, showcasing a multi-faceted approach to the valorization of lignocellulosic materials. [Display omitted] • DESys was formed by directly combining HBA and HBD with wood meal. • Lignin extraction yield was significantly improved. • Physicochemical properties of the extracted lignin were preserved. • The extracted lignin residue was utilized for highly efficient neutral red adsorption. [ABSTRACT FROM AUTHOR]

Although dye-decolourising peroxidases (DyPs) are well-known for lignin degradation, a comprehensive understanding of their mechanism remains unclear. Therefore, studying the mechanism of lignin degradation by DyPs is necessary for industrial applications and enzyme engineering. In this study, a dye-decolourising peroxidase (CsDyP) gene from C. serinivorans was heterologously expressed and studied for its lignin degradation potential. Molecular docking analysis predicted the binding of 2, 2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), veratryl alcohol (VA), 2, 6-dimethylphenol (2, 6- DMP), guaiacol (GUA), and lignin to the substrate-binding pocket of CsDyP. Evaluation of the enzymatic properties showed that CsDyP requires pH 4.0 and 30 °C for optimal activity and has a high affinity for ABTS. In addition, CsDyP is stable over a wide range of temperatures and pH and can tolerate 5.0 mM organic solvents. Low NaCl concentrations promoted CsDyP activity. Further, CsDyP significantly reduced the chemical oxygen demand decolourised alkali lignin (AL) and milled wood lignin (MWL). CsDyP targets the β-O-4, C O, and C C bonds linking lignin's G, S, and H units to depolymerize and produce aromatic compounds. Overall, this study delivers valuable insights into the lignin degradation mechanism of CsDyP, which can benefit its industrial applications and lignin valorization. [ABSTRACT FROM AUTHOR]

As a wood containing many ordered cell cavities and blood vessels, eucalyptus is an ideal precursor material in preparing hierarchical porous carbon electrodes for Zn-air batteries. However, insufficient micro-mesoporous and minor active sites inhibit the application of wood-directly derived carbon materials in Zn-air batteries. Hence, a simple and cost-effective formic acid pretreatment method was proposed to prepare nitrogen-doped bulk phase catalysts with abundant micro-mesoporous and enough high active sites from eucalyptus. Formic acid pretreatment selectively removed part of lignin and hemicelluloses, thus generating abundant nanopores and contributing to the introduction of more nitrogen active sites. Moreover, the obtained bulk carbon had high mechanical strength and wonderful electrical conductivity, containing cross-linked networks and natural ion transport channels. Benefiting from the above advantages, the bulk carbon catalyst could be directly used as self-supported cathode, and the resulting Zn-air batteries achieved a long cycle life of more than 300 h. This work provides a simple and feasible method for the development of biomass-derived hierarchical bulk-phase porous carbons for energy-related applications. • Hierarchical porous nitrogen doped bulk carbon derived from eucalyptus by formic acid pretreatment. • The bulk carbon with a large number of nanopores has high mechanical strength and high electrical conductivity. • A high number density of graphite N and pyridine N is introduced in carbon lead to favorable ORR activity. • The Zn-air battery with bulk FA-CN achieves a long cycle life of more than 300 h at 10 mA cm−2. [ABSTRACT FROM AUTHOR]

[Display omitted] • An integrated and eco-friendly biorefinery was proposed. • XOS, glucose and the residual lignin were obtained with high yield. • Genetically modified poplar was a potential feedstock for biorefinery. • The LPC-CSE has higher oxygen content and specific capacitance. • The LPC supercapacitor exhibits an excellent cycling performance. 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 β- 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. [ABSTRACT FROM AUTHOR]

• Heat treatment led to structural changes in wood cell wall compounds. • Structural changes didn't affect the elastic modulus but decreased the creep modulus at treating temperature higher than 160 °C. • At treating temperature of 160 °C, an improved creep performance. • At relative humidity of 90%, heat treatment led to an improvement in creep behavior. In this study, wood was heat treated at temperatures of 160, 175 and 190 °C and creep behavior of modified wood at various moisture contents was assessed. Fourier-transform infrared spectroscopy (FTIR) was conducted to find a relation between creep behavior and structural changes, aiming to develop their applications for construction purposes. FTIR results showed fundamental structural changes: removal of extractives, hemicelluloses and amorphous parts of cellulose and partial degradation of lignin. Creep results showed that unlike elastic short-term modulus, creep modulus decreased at treating temperature higher than 160 °C. Treated samples at 160 °C had an improved creep performance in moist conditions, attributable to lower degradation of cell wall components and to the lower hygroscopicity. [ABSTRACT FROM AUTHOR]

This study evaluated the solubility of low-processed wood fibers produced from a low temperature acid hydrotropic fractionation (AHF) in an ionic liquid (IL) 1,5-diazabicyclo[4.3.0]non-5-enium acetate (DBNH[OAc]. Unbleached wood fibers produced from AHF using p -Toluenesulfonic acid (p -TsOH) with or without post-treatments with lignin and hemicelluloses content up to 15% and 25%, respectively, were dissolved directly into the IL DBNH[OAc]. Post-AHF treatments using dilute alkaline and glycerol swelled the cellulose and partially removed residual lignin resulting in improved dissolution. Semi-quantitative 2D HSQC NMR analyses revealed that the undissolved wood fiber residues were enriched with G units and condensed S units (S cond), demonstrating, as expected, that G units and condensed lignin substructures have a negative effect on dissolution in DBNH[OAc]. Therefore, AHF with rapid fractionation at low temperatures offers a promising advantage over existing high temperature pulp dissolving fiber (PDF) processes in terms of reducing energy input, lowering lignin content as well as reducing lignin condensation for producing man-made cellulosic fibers (MMCF). [ABSTRACT FROM AUTHOR]

Magnetic porous carbon materials as peroxymonosulfate (PMS) activators for sulfadiazine degradation were derived from metal-organic frameworks (MOFs) grown in-situ on the cellulose of wood through the one-step pyrolysis method. The cellulose was obtained by treating wood powder with sodium chlorite to remove lignin, and Fe-MOFs (MIL-101(Fe)) nanoparticles were in-situ grown on the cellulose through hydrothermal reaction. The delignification of wood effectively enhanced the in-situ growth of MIL-101(Fe) on the wood tracheid skeleton, increased the specific surface area of magnetic porous carbon material (Fe@PC-50) after pyrolysis, and improved the performance of Fe@PC-50 as a PMS activator for the degradation of sulfadiazine. With the presence of 0.04 g L−1 Fe@PC-50 and 0.12 g L−1 PMS, the degradation percentage of sulfadiazine (20 mg L−1) could reach 100 % within 15 min, indicating excellent catalytic activity. Quenching tests and electron paramagnetic resonance (EPR) indicated that both free and non-free radicals played important roles in PMS activation. X-ray photoelectron spectroscopy (XPS) suggested that Fe0 and Fe 3 C were the possible important active sites for sulfadiazine degradation. This work offered an effective method to synthesize PMS activators from biomass/MOF materials for water treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

The depolymerization of lignin into dicarboxylic acids (DCA) by the Fenton oxidation process is a promising approach to valorising lignin. However, Fenton oxidation is challenging due to the demand for acidic reaction conditions and homogeneous Fe2+ catalysts, which cannot be recovered. Herein, we fabricated a biochar-based solid-acid catalyst (SBC) from the pyrolysis of rice straw biomass followed by H 2 SO 4 treatment. This novel catalyst achieved an enhanced catalytic performance in the activation of H 2 O 2 under circumneutral pH, visible-light irradiation and Fe-free conditions. Under optimum conditions, a cumulative yield of 40.1 μ mol. g c a t − 1 . h − 1 of malonic, maleic, fumaric, succinic and gallic acid was obtained using 40 mM H 2 O 2 , 1 g/L catalyst loading and 4 h reaction time, which is comparable to yields reported in the literature under elevated temperatures and pressures. The activity of SBC stems from the synergy of oxygenated surface functional groups and persistent free radicals (PFRs), which can chemisorb and subsequently activate H 2 O 2 and dissolved O 2 to yield •OH and 1O 2. Addition of NaN 3 scavenger for 1O 2 enhanced the cumulative DCA yields to 282.4 μ mol. g c a t − 1 .h−1, suggesting that 1O 2 is the main reactive oxygen species in the reaction. Finally, the SBC catalysts remained stable at the said reaction conditions and could be recycled without significant deactivation. After five cycles, the lignin conversion and cumulative DCA yields decreased by 19.7% and 23% respectively. These results show that Fe-free, visible-light Fenton-like catalytic oxidation of lignin with acid-modified biochars is a promising way to produce high-value platform chemicals. [Display omitted] • Catalytic metal-free Fenton-like oxidation of alkali lignin was studied. • Carbonaceous solid acid catalysts were produced from pyrolysis of rice straw biomass. • Persistent free radicals on biochars could act as electron donors to activate H 2 O 2 into.•OH and •O 2 −. • Acetonitrile-water mixture was the best solvent for the reaction. • Malonic, malic and succinic acid were the major dicarboxylic acid products from the reaction. [ABSTRACT FROM AUTHOR]

• Degree of cellulose crystallinity during natural weathering periods can specify the performance of wood. • A kinetic study on surface photo-degradation determine the service time of wood materials in exterior uses. • Thermal treatment can delay color change of wood due to upgraded lignin and crystalline structure of cellulose. • Thermal treatment improved the hydrophobicity and crystallinity index of wood. • Natural weathering changed wettability and morphological properties of the wood surface. The hygroscopic behavior of wood-based materials is undoubtedly influential on the material surfaces exposed to climatic conditions. The paper aims to kinetically investigate the photo-degradation and surface characteristics of thermally-treated spruce wood at 185 °C and un-treated (reference) sample through 2 years of natural weathering. Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy and X-ray diffraction (XRD) were employed to investigate the chemical changes occurred in lignin and crystalline structure of cellulose as a function of outdoor exposure. Detailed measurements of morphological and surface changes were evaluated during exposing periods. Surface wettability and roughness as well as cracks were increased for all samples due to weathering as the exposure time extended. Prominently, the color changes (ΔE) and photo-chemical reactions were found to be negligible in short-time weathering thanks to thermal modification. In the long–term exposing, more OH-bonds caused by lignin leaching out resulted in presence of cracks and the affinity for water on reference sample. Degree of crystallinity significantly decreased by 12.7% in thermally treated wood and 18.3% in reference sample after long-term weathering while, the crystallinity index of thermally-treated wood increased to 4.7% in 6-month weathering. Hence, the amorphous structures and chromophores groups appeared on the reference wood at a faster and more intense rate during exposing time. Thermal treatment delayed photo-yellowing as well as color change of wood due to up-graded lignin and cellulose crystallinity through a photo-stable structure. Accordingly, kinetic studies ascertained the service-time of wood products in exterior uses. [ABSTRACT FROM AUTHOR]