Search

To maximize the utilization of Abaca lignin in the current biorefinery, structural characteristics of native lignin from Abaca were firstly comprehensively investigated. Parallelly, effective delignification of Abaca was achieved by alkaline hydrogen peroxide (AHP) process, which facilitated the production of specialty paper in industry. The structural changes of lignin macromolecules during the AHP delignification were illustrated by comparing the structural differences of the released lignin fraction and corresponding native lignin, which were analyzed via the advanced analytical methods, such as 2D-HSQC NMR, 31P NMR, pyrolysis-GC/MS, and GPC techniques. It was found that Abaca lignin is a HGS-type lignin, which is overwhelmingly composed of β-O-4 linkages and abundant hydroxycinnamic acids (mainly p-coumaric acid). In addition, partial cleavage of β-O-4 linkages and p-coumarate in lignin occurred during the AHP delignification process. Meanwhile, AHP process also led to the elevation of H-type lignin units in AHPL. Considering that β-O-4 bond is vulnerable in the catalytic degradation process of lignin, the lignin with abundant β-O-4 linkages is beneficial to the downstream conversion of lignin into aromatic chemicals.

Elucidating the structural characteristics and changes of lignin during biorefining is considerably important for lignin valorization. To examine the structural transformations of lignin under deep...

The natural lignin macromolecule is structurally complex and heterogeneous polymers. Herein, to comprehend the dynamic structural characteristics of poplar (Populus tomentosa) lignin during the gro...

Making full use of the lignocellulose is of great significance to the current biorefinery enterprises. As a natural macromolecule polymer, lignin has a prominent potential as renewable feedstock to...

Efficient deconstruction of lignocellulose is vitally important for the biorefinery industry because lignin structures play a crucial role in the high value-added conversion of lignin. In this study, an integrated process based on hydrothermal pretreatment (HTP) and Kraft delignification was proposed to deconstruct lignocellulosic biomass. It was found that the HTP not only facilitated the production of xylo-oligosaccharides but also reduced the chemicals dosage of the following delignification. The structural characteristics of lignin obtained from the integrated process were investigated by NMR spectroscopy and gel-permeation chromatography. Additionally, double enzymatic lignins (DELs) isolated from different feedstocks were used as "model lignin" to delineate the structural transformations of lignin during H2 O2 , ClO2 , and O3 bleaching. Significant changes of the lignin structure were observed during the ClO2 bleaching process, including degradation of aromatic rings, enrichment in p-hydroxyphenyl units, and increase of carboxylic groups. A comparison of the structural characteristics of the bleached lignins indicated that HTP benefited the subsequent bleaching process. Enhanced knowledge of lignin chemistry during deconstruction and delignification could provide valuable insight into the current lignocellulose biorefinery.

In this study, a green and clean integrated process based on microwave-assisted hydrothermal pretreatment (MHTP) and subsequent alkali post-treatment was performed to isolate and characterize water- and alkali-soluble hemicelluloses (SHs and AHs) from Hybrid Pennisetum (HP) as well as to improve the enzymatic digestibility of HP. Meanwhile, part of hemicelluloses was degraded into the value-added xylo-oligosaccharides (XOS) during the MHTP process, which would be applied to the food and pharmaceuticals industries. State-of-the-art analytical techniques (e.g., HPLC, HPAEC, GPC, and 2D-HSQC) were used to investigate the main component streams (SHs, AHs, XOS, and glucose). Results showed that the structural characteristic of SHs and AHs was mainly composed of β-(1→4)-linked xylans. Additionally, the enzymatic digestibility of the cellulose-rich substrate (A190(10)) was 92.8%, which was 3.4 times higher than that of raw material (27.4%). In short, the proposed integrated process was considered as a promising biorefinery strategy for both hemicellulose-based products and bioethanol.

Lignin is the most abundant aromatic biomacromolecule on the earth, which is an attractive raw material for producing bio-based chemicals, materials, and fuels. However, the complexity, heterogeneity, and variability of the lignin structure always hinders the value-added application of different sources of raw materials. In this study, double enzymatic lignin (DEL) was isolated from balsa grown for different lengths of time to understand the structural variations of lignin macromolecules during the growth of balsa for the first time. Confocal Raman microscopy and component analysis were used to monitor the lignin accumulation in balsa. Meanwhile, the structural characteristics and chemical reactivity of DELs were synthetically characterized by advanced 2D-HSQC and 31P-NMR techniques. It was found that the balsa lignin is a typical hardwood lignin and it is overwhelmingly composed of C–O bonds (i.e., β-O-4 linkages), whose content is elevated with increasing tree-age. Interestingly, carbon–carbon linkages (e.g., β-β and β-5) in these DELs isolated from 3-and 5-year-old balsa are gradually disappearing. Considering the increasing molecular weight of DELs with tree-age, it was concluded that lignin macromolecules in balsa wood were gradually polymerized within the growth period. Furthermore, abundant C–O linkages with less C–C linkages in the DELs from 3 and 5-year-old balsa wood suggested that these feedstocks are promising in current lignin-first biorefinery and will facilitate the conversion of aromatic chemicals from the lignin macromolecule. In short, a comprehensive understanding of native lignin during the growth of balsa wood will not only advance the understanding of biosynthetic pathways of lignin biopolymer, but also facilitate the deconstruction and value-added applications of this kind of feedstock.

Herein, a two-step hydrothermal pretreatment combined with alkali extraction method was applied to deconstruct the poplar cell walls for enzymatic hydrolysis. Results revealed that 88.1 % of hemicelluloses and 77.6 % of lignin were removed during the integrated treatment performed at 180 °C and a maximum enzymatic hydrolysis efficiency of 96.1 % was achieved. Confocal Raman microscopy suggested that the removal of hemicelluloses from cell walls was inhomogeneous, and most hemicelluloses were released from the secondary wall. In addition, 35.2–56.8 % of hemicelluloses were isolated from the integrated treatment. Detailed structural analysis revealed that the water-soluble hemicelluloses possessed more branched structure than the alkali-soluble hemicelluloses and the hemicelluloses isolated from the poplar were mainly composed of a linear backbone of (1→4)-β- d -Xylp with 4-O-Me-α-d-GlcpA attached as side chains. This work provides an efficient pathway to transform poplar into fermentable sugars and hemicelluloses with considerable yield.

Lignin nanoparticles offer a way for a high value use of the renewable resources. However, there are few green and facile methods so far for producing lignin nanoparticles with both high yield and ...

To understand the structural features and transformations of hybrid Pennisetum (HP) lignin, an integrated treatment on the basis of microwave-assisted hydrothermal pretreatment (MHTP) (at 180–200 °...

Herein, the mechanochemical process combined diluted acid impregnation and ball-milling treatment was developed to overcome the recalcitrance of lignocellulose. The high-yield fermentable sugars (glucose and xylose) and impregnated enzymatic lignin (IEL) streams have been simultaneously obtained via mechanochemistry and enzymatic hydrolysis process. It was found that the mechanochemical pretreatment significantly facilitated the enzymatic hydrolysis of the treated substrates, releasing high yield (>90%) of fermentable sugars for further utilization. CP/MAS 13C NMR and solution-state 2D NMR techniques showed that the crystallinity index (CrI) and degree of polymerization (DP) of cellulose in the treated substrates were both decreased. In addition, detailed structural characterizations of the obtained IEL fractions were achieved by the state-of-the-art NMR and GPC techniques. Results showed that the IEL fractions presented similar structural features as compared to the corresponding native lignin (DEL). The study provides an efficient and clean pathway for the conversion of energy from lignocelluloses; meanwhile, the residual lignin with unchanged structures could serve as ideal feedstock for the liquid fuel, bio-based materials, and chemicals in the current biorefinery process.

The removal of heavy metals ions from wastewater by an economic, high-effective, and environmentally friendly method is particularly important. In this study, an effective lignin-based bio-adsorbent (SAPL-1.5), which contained specific functional groups and spatial cross-linking structures, was synthesized through chemical modification. SAPL-1.5 was comprehensively characterized by 31P, 1H, 13C NMR, and elemental analysis as compared to the raw lignin. The results showed that the chemical reactivity of lignin was significantly improved after phenolation process, and the adsorption groups were successfully grafted onto lignin macromolecule. In addition, the influences of pH, SAPL-1.5 dosage, contact time, and initial Pb (II) concentration on the adsorption performance was systematically investigated. The highest adsorption capacity reached to 130.2 mg/g (Pb (II), 140 mg/L), and a removal efficiency of 100% was achieved (Pb (II), 20 mg/L). Moreover, the adsorption isotherm and adsorption kinetics indicated that the results were fitting well with the Langmuir and pseudo-second-order model, respectively. Furthermore, the removal efficiency of SAPL-1.5 for Pb (II) (20 mg/mL) still maintained over 85% after 5 cycles. Therefore, the lignin-based material obtained could be considered as a promising potential adsorbent with a low cost, high performance and reutilization for its application in the wastewater treatment process. It is believed that the lignin-based bio-sorbent can enlarge the lignin valorization in the current biorefinery process.

Understanding of the fundamental chemistry of lignin macromolecules in lignocellulosic biomass will facilitate the further development of renewable biofuel and biomaterial production. In the present study, to thoroughly delineate the detailed structural characteristics of the native lignin in the three major Eucalyptus woods, MWL, CEL, and EHL preparations were sequentially isolated from the diverse Eucalyptus wood. Parallelly, a modified enzyme lignin (DEL) based on double ball-milling and enzymatic hydrolysis was also prepared with superhigh yield (102.5–109.5%) from same Eucalyptus wood. The structural characteristics of all the lignin preparations were elaborately investigated by HPAEC, GPC, and NMR techniques (2D-HSQC and 31P NMR). Results showed that the contents of different substructures (β-O-4, β-β, β-5, and β-1) and S/G ratios of lignin macromolecules varied among these Eucalyptus species. As compared to the β-O-4 content in the extracted lignins (MWLs and CELs, 44.5–60.2/100Ar), the residual li...

In this study, feather was used as the source of protein and combined with copper and boron salts to prepare wood preservatives with nano-hydroxyapatite or nano-graphene oxide as nano-carriers. The treatability of preservative formulations, the changes of chemical structure, micromorphology, crystallinity, thermal properties and chemical composition of wood cell walls during the impregnation and decay experiment were investigated by retention rate of the preservative, Fourier transform infrared spectroscopy (FT-IR), scanning electronic microscopy-energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), thermoanalysis (TG), and confocal Raman microscopy (CRM) techniques. Results revealed that the preservatives (particularly with nano-carrier) successfully penetrated wood blocks, verifying the enhanced effectiveness of protein-based preservative with nano-carrier formulations. Decay experiment demonstrated that the protein-based wood preservative can remarkably improve the decay resistance of the treated wood samples, and it is an effective, environmentally friendly wood preservative. Further analysis of these three preservative groups confirmed the excellent function of nano-hydroxyapatite as a nano-carrier, which can promote the chelation of preservatives with higher content of effective preservatives.

The alcoholic depolymerization and Mannich reaction were conducted to improve the chemical activity of biorefinery technical lignins and introduce amino groups into lignins, respectively. To understand the chemical structural transformations and examine the reaction mechanism, GPC and solution-state NMR techniques were performed. Element analysis was also used to quantify the amount of amine groups. The NMR characterization the depolymerized lignins indicated of the depolymerization, demethoxylation, and bond cleavage of linkages occurred during the depolymerization process. Results showed that the depolymerization temperature instead of the addition of capping reagents was the main factor for improving the reactivity of lignin under the given conditions. The Mannich reaction was very selective, primarily occurred at H3,5 and G5 positions, and the H units present a higher chemical reactivity. It is believed that the understanding of the fundamental chemistry of lignin during depolymerization and Mannich reaction process will contribute to the extension of high value-added applications of biorefinery lignin.

In this study, bamboo (Phyllostachys pubescens) was successfully deconstructed using an integrated process (autohydrolysis and subsequent delignification). Xylooligosaccharides, high-purity lignin, and digestible substrates for producing glucose can be consecutively collected during the integrated process. The structural change and fate of lignin during autohydrolysis process was deeply investigated. Additionally, the structural characteristics and active functional groups of the lignin fractions obtained by these delignification processes were thoroughly investigated by NMR (2D-HSQC and 31P NMR) and GPC techniques. The chemical compositions (S, G, and H) and major linkages (β-O-4, β-β, β-5, etc.) were thoroughly assigned and the frequencies of the major lignin linkages were quantitatively compared. Considering the structural characteristics and molecular weights of the lignin as well as enzymatic saccharification ratio of the substrate, the combination of autohydrolysis and organic base-catalyzed ethanol pretreatment was deemed as a promising biorefinery mode in the future based on bamboo feedstock.