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An efficient separation technology for hydrolysates towards a full valorization of bamboo is still a tough challenge, especially regarding the lignin and lignin-carbohydrate complexes (LCCs). The present study aimed to develop a facile approach using organic solvent extraction for efficiently fractionating the main components of bamboo hydrolysates. The high-purity lignin with only a trace of carbohydrates was first obtained by precipitation of the bamboo hydrolysate. The water-soluble lignin (WSL) fraction was extracted in organic solvent through a three-stage organic solvent extraction process, and the hemicellulosic sugars with increased purity were also collected. Furthermore, a thorough characterization including various NMR techniques (31P, 13C, and 2D-HSQC), GPC, and GC-MS was conducted to the obtained lignin-rich-fractions. It was found that the WSL fraction contained abundant functional groups and tremendous amount of LCC structures. As compared to native LCC of bamboo, the WSL fraction exhibited more typical LCC linkages, i.e. phenyl glycoside linkage, which is the main type of chemical linkage between lignin and carbohydrate in both LCC samples. The results demonstrate that organic phase extraction is a highly efficient protocol for the fractionation of hydrolysate and the isolation of LCC-rich streams possessing great potential applications. [ABSTRACT FROM AUTHOR]

Bamboo was fractionated using formic acid based on a one-step organosolv process under high pressure (at 145 °C for 45 min, 0.3 MPa) and at atmospheric pressure (at 101 °C for 120 min), respectively. High-pressure formic acid lignin, atmospheric formic acid lignin and milled wood lignin of bamboo were subjected to comprehensive structural characterization using gel permeation chromatography (GPC), Fourier transform infrared (FTIR) and solution-state NMR techniques ( 1 H, 13 C, 2D-HSQC, and 31 P-NMR spectroscopies). The results indicated that the formic acid fractionation under high pressure presents a quick and efficient delignification method by enhancing the cleavage of interunitary bonds in lignin (β-O-4′, β-β and β-5′), and dissolved lignin also occurred condensation reaction. As compared to atmospheric formic acid lignin, high-pressure formic acid lignin obtained showed higher purity and yield, and had relatively higher contents of phenolic and carboxylic groups. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomass exhibits a promising potential for production of carbon materials. Nitrogen and phosphorus co-doped carbon quantum dots (N,P-CQDs) were fabricated via (NH 4) 2 HPO 4 assisted hydrothermal treatment of cellulose pulp fibers. The as-prepared N,P-CQDs were characterized by HRTEM, FTIR, fluorescence and UV–vis, and then incorporated into g-C 3 N 4 (CN) through sonication and liquid deposition, forming N,P-CQDs/sonication treated g-C 3 N 4 (C-SCN) composites, which were then explored as photocatalysts. The photocatalytic ability of C-SCN towards model lignin was further analyzed. The results showed that, the fluorescence intensity and photoluminescence performance of N,P-CQDs were much higher than that of CQDs; the heterojunction was successfully constructed between the composites of N,P-CQDs and SCN; the incorporation of N,P-CQDs enhanced the visible light absorption, but reduced the band gap of the composite heterojunction; the resultant photocatalysts exhibited a good photocatalytic ability of model lignin via catalyze the fracture of β –O–4′ ether bond and C C bond, i.e., the photocatalytic degradation ratio reached up to 95.5 %; and the photocatalytic reaction generated some valuable organics such as phenyl formate, benzaldehyde, and benzoic acid. This study would promote the high value-added utilization of lignocellulosic resources especially in the transformation of lignin, conforming the concept of sustainable development. • Nitrogen and phosphorus co-doped CQDs was prepared from cellulose pulp. • N,P-CQDs exhibited a much better optical properties than CQDs. • N,P-CQDs/g-C 3 N 4 composites were fabricated and explored as photocatalysts. • N,P-CQDs enhanced photocatalytic capacity of CQDs/g-C 3 N 4 towards lignin model. • Some valuable chemicals were generated during the photocatalytic reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • A ternary DES was prepared, explored and compared with binary ones. • Microwave-assisted DES pretreatment was applied for lignin processing. • Lignin has been improved such as purity, dispersity and thermal stability. • The interaction between ternary DES and lignin was analyzed by MD simulation. • Dissolution mechanism of microwave-assisted ternary DES on lignin was proposed. Lignin is the most abundant natural aromatic macromolecule in the nature, but its high value-added utilization has been seriously hindered by the highly random and branched structures and the high difficulty in separation and purification. A microwave-assisted ternary deep eutectic solvent (DES) composed by formic acid, lactic acid and choline chloride was developed for lignin pretreatment. The effects of three types of DES on main characteristics of lignin were investigated, and the corresponding dissolution mechanism was proposed. The results showed that, the microwave-assisted ternary DES pretreatment showed an obvious improvement on main characteristics of regenerated lignin, e.g., a higher purity, lower molecular weight with reduced dispersity, improved thermal stability, higher phenolic hydroxyl content, and increased antioxidative activity in comparison with control. It is expected that the lignin macromolecular can be facile regulated and upgraded by the proposed ternary DES. [ABSTRACT FROM AUTHOR]

Lignin is the main factor inhibiting enzymatic hydrolysis of lignocellulosic biomass. Different pretreatments can alter chemical and structural characteristics of lignin, thus affecting its adsorption capacity of enzymes. Herein, enzymatic mild acid lignin (EMAL) was separated from poplar branch wood chips as substrates resulted from different combined pretreatments, and then characterized and adsorbed by enzymes, so as to study the effects of different pretreatments on enzyme adsorption capacity. The results showed that the phenolic hydroxyl content and C C bond number of lignin increased after hydrothermal pretreatment, which increased the unproductive adsorption of mixed enzymes through hydrophobic interaction and hydrogen bonds. Chemical pretreatment after hydrothermal pretreatment can further reduce the unproductive adsorption of lignin on mixed enzymes, improving the enzymatic hydrolysis of substrates. This study would help to unmask the adsorption of mixed enzymes on lignin resulted from combined pretreatments, and facilitate the rapid development of efficient pretreatment for lignocellulosic biomass. [Display omitted] • Effects of hydrothermal & chemi-mechanical pretreatment on lignin was studied. • Adsorption capacity and mechanism of mixed enzymes onto lignin were investigated. • Relationship between lignin characteristics and enzyme adsorption was studied. • Isothermal adsorption and adsorption kinetics of enzymes on lignin were analyzed. • Adsorption mechanism of enzymes on different lignin was revealed. [ABSTRACT FROM AUTHOR]

Lignin is the most abundant aromatic source in nature, whose efficient utilization has been recognized as a key challenge in biorefinery. Deep eutectic solvents (DES) exhibit excellent solubility for lignin, and are promising solvent for facilitating the lignin-first biorefinery and valorization of lignin. Herein, microwave-assisted carboxylic acid-based DES pretreatment was applied on corncob; the effects of the pretreatment on physical and chemical structures of lignin was investigated. The results showed that microwave-assisted DES pretreatment enhanced the deconstruction efficiency of corncob in terms of the high removal ratio and recovery yield of DES-lignin; Moreover, the resultant DES-lignin exhibited lower molecular weights and particle size than that from conventional DES pretreatment, and presented abundant phenolic OH groups. This study provide a highly efficient pretreatment approach for the agricultural residues and the sufficient understanding on structural and chemical characteristics of resultant DES-lignin will promote its subsequent conversion and application. [Display omitted] • Microwave-assisted carboxylic acid-based DES pretreatment was applied on corncob. • Microwave-assisted DES pretreatment enhanced deconstruction efficiency. • The pretreatment exhibited a high removal ratio of lignin and hemicelluloses. • The lignin had a good recovery yield, high purity, and good thermal stability. • The lignin had lower particle size & narrow distribution, and high reactivity. [ABSTRACT FROM AUTHOR]

In this work, poplar wood chips (PWCs) were subjected to autohydrolysis pretreatment with different levels of intensity, and the autohydrolyzed PWCs were used to make chemi-thermomechanical pulp (CTMP). The changes of the lignin structure of PWCs and the bleachability of the CTMP with autohydrolyzed PWCs as raw materials were both investigated. The results showed that the lignin structure changed to some extent in both CTMP pulping and the following bleaching process. The contents of conjugated carbonyl and quinone groups in the lignin structure were negatively correlated with the CTMP bleachability. Compared to the quinone groups, the conjugated carbonyl groups had a much greater impact on the bleachability. The present work would play a vital role for the application of autohydrolysis to the poplar CTMP pulping and the subsequent bleaching processes. [Display omitted] • Poplar wood chips (PWCs) were autohydrolyzed with different intensity levels. • Autohydrolyzed PWCs were used to make bleached chemi-thermomechanical pulp (CTMP). • Changes in lignin structure of PWCs and the CTMP bleachability were both explored. • Autohydrolysis was beneficial to the bleachability as the CHF did not exceed 10.77. • Conjugated carbonyl had bigger impact on CTMP bleachability than quinone group. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lignin-derived GQDs were prepared via phosphous acid-assisted hydrothermal process. • P-LGQDs have excellent electronic, optical properties, and pH-responsiveness. • P-LGQDs/g-C 3 N 4 shows good photocatalytic degradation ability for MB & model lignin. • Degradation products such as phenyl formate can be generated from model lignin. Value- added utilization of carbon-rich lignin has become an urgent and attractive research topic due to its abundance, low cost, and sustainability. How to convert lignin in an efficient and green strategy is the bottleneck limiting its valorization. Herein, a phosphorous acid (P) assisted hydrothermal process to produce lignin-derived graphene quantum dots (P-LGQDs) was developed. The as-prepared P-LGQDs was comprehensively characterized, and explored in photocatalysis. The P-LGQDs have a narrow particle size distribution, excellent electronic and optical properties, and a good pH-responsiveness. The P-LGQDs was further used to construct P-LGQDs/g-C 3 N 4 heterojunction, showing excellent photocatalytic degradation ability towards methylene blue and model lignin (94.6 % and 93.1 %, respectively). This present study offers a universal strategy for the value-added utilization and valorization of lignin. [ABSTRACT FROM AUTHOR]