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1.
ChemSusChem ; 2020 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-32419330

RESUMO

Lignin depolymerization into aromatic monomers with high yields and selectivity is essential for the economic feasibility of biorefinery. However, the relationships between lignin structure and its reactivity for upgradeability are still poorly understood, in large part due to the difficulty in quantitative characterization of lignin structural properties. To overcome these shortcomings, we use advanced NMR technologies (2D HSQC and 31 P) to accurately quantify lignin functionalities. Diverse lignin samples prepared from Eucalyptus grandis with varying ß-O-4 linkages were subjected to Pd/C-catalyzed hydrogenolysis for efficient C-O bond cleavage to achieve theoretical monomer yields. Strong correlations were observed between the yield of monomeric aromatic compounds and the structural features of lignin, including the contents of ß-O-4 linkages and phenolic hydroxyl groups. Notably, a combined yield of up to 44.1 wt% was obtained from ß-aryl ether rich in native lignin, whilst much lower yields were obtained from technical lignins which were low in ß-aryl ether contents. This work quantitatively demonstrates that the lignin reactivity for acquiring aromatic monomer yields varies depending on the lignin fractionation processess.

2.
ChemSusChem ; 2020 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-32291938

RESUMO

As a skeleton component of plants, lignin is an organic macromolecule polymer that can be regenerated and naturally degraded. Annually, plant growth produces about 150 billion tons of lignin. In industrial processes such as paper and biomass-refining industry, large amounts of lignin are formed as by-products. Most of technical lignins are directly combusted to obtain heat, which not only is a waste of organic matter but also leads to environmental pollution and other issues. Interestingly, lignin can be used as slow-release carriers and coating materials for fertilizers due to its excellent slow release properties as well as chelating and other functionalities. Preparation of lignin-based slow/controlled release fertilizers can be achieved by sustainable chemical (ammoxidation, Mannich reaction, and other chemical modifications), coating (without or with chemical modification), and chelation modifications. This Review systematically summarizes the methods, mechanisms, and application of the above methods for preparing lignin-based slow/controlled release fertilizers. Although the evaluation standards and methods of lignin-based slow/controlled release fertilizers are not perfect, it is believed that more and more scholars will pay more attention to them to accelerate the development and application of lignin-based slow/controlled release fertilizers, so as to improve their relevant standards. In short, there is an urgent need to improve the preparation process of lignin-based slow/controlled release fertilizers and application as lignin-based slow/controlled release fertilizers to production practice as soon as possible.

3.
Carbohydr Polym ; 238: 116212, 2020 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-32299557

RESUMO

In this study, the cellulose and hemicelluloses in heartwood, sapwood, and bark of E. urophylla × E. grandis were comprehensively investigated. The ultrastructural topochemistry of carbohydrates in cell walls was examined in situ by confocal Raman microscopy. Cellulose and alkali-extractable hemicelluloses samples were isolated from different tissues and comparatively characterized by compositional carbohydrate analyses, determination of molecular weights, FT-IR spectroscopy, and XRD and NMR techniques. It was found that among all of the samples, heartwood cellulose had the highest molecular weight as well as the lowest degree of crystallinity. Meanwhile the hemicelluloses in heartwood had higher xylose content, lower degree of branching, slightly lower molecular weights but narrower polydispersity than those in sapwood. The eucalyptus hemicelluloses mainly consisted of (1→4)-ß-D-xylan backbone with glucuronic acid side chains. Furthermore, the hemicelluloses isolated from sapwood had a higher degree of substitution with terminal galactose than those isolated from heartwood and bark.

4.
ChemSusChem ; 2020 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-32118355

RESUMO

The valorization of lignin to replace phenol is significant in the production of phenolic resins. However, a great challenge is to produce lignin-based resin (LR) with a suitable viscosity and high substitution rate of lignin to phenol. In this study, LRs were produced using hardwood technical lignin derived from the pulping industry. Structural analysis of the LRs indicated that the unsubstituted para and ortho carbon atoms of the aromatic ring influenced the curing temperature and activation energy of the resins. The curing kinetics and thermal decomposition study implied that urea and methylene groups in cured LRs were significant factors that affected the thermal stability negatively. The prepared LRs showed desirable features if used as adhesives to make plywood. This is the first approach in which a substitution rate of up to 65 % is achieved for low-reactive-site hardwood lignin, which provides a solution to the challenge of the simultaneous realization of the high addition of lignin and the adaptive viscosity of resins.

5.
Bioresour Technol ; 299: 122685, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31918970

RESUMO

Different pretreatments strategies have been developed over the years mainly to enhance enzymatic cellulose degradation. In the new biorefinery era, a more holistic view on pretreatment is required to secure optimal use of the whole biomass. Hydrothermal pretreatment technology is regarded as very promising for lignocellulose biomass fractionation biorefinery and to be implemented at the industrial scale for biorefineries of second generation and circular bioeconomy, since it does not require no chemical inputs other than liquid water or steam and heat. This review focuses on the fundamentals of hydrothermal pretreatment, structure changes of biomass during this pretreatment, multiproduct strategies in terms of biorefinery, reactor technology and engineering aspects from batch to continuous operation. The treatise includes a case study of hydrothermal biomass pretreatment at pilot plant scale and integrated process design.


Assuntos
Lignina , Vapor , Biomassa , Celulose , Fracionamento Químico , Engenharia , Hidrólise
6.
Bioresour Technol ; 297: 122471, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31787511

RESUMO

Hereon, tobacco stalk was deconstructed by lyophilization, ball-milling, ultrasound-assisted alkali extraction, hydrothermal pretreatment (HTP), and alkali presoaking, respectively, followed by dilute alkali cooking to both improve its enzymatic digestibility and isolate the hemicellulosic streams. It was found that a maximum cellulose saccharification rate of 93.5% was achieved from the integrated substrate by ball-milling and dilute alkali cooking, which was 4.4-fold higher than that from the raw material. Interestingly, in this case, 76.9% of hemicelluloses were simultaneously recovered during the integrated treatment. Structural determination indicated that the hemicelluloses released from tobacco stalk by dilute alkali cooking were mixed polysaccharides, and the (1 â†’ 4)-linked ß-D-Xylp backbone branched with L-Araf units at O-2/O-3 and 4-O-Me-α-D-GlcpA units at O-2 of the xylose residues was the main structure. In comparison, ultrasound-assisted alkali extraction, ball-milling, and HTP favored the extraction of hemicelluloses with less branched structure and lower molecular weights in the following alkali cooking.


Assuntos
Celulose , Tabaco , Hidrólise , Peso Molecular , Polissacarídeos
7.
Int J Biol Macromol ; 144: 596-602, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31837367

RESUMO

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 ß-O-4 linkages and abundant hydroxycinnamic acids (mainly p-coumaric acid). In addition, partial cleavage of ß-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 ß-O-4 bond is vulnerable in the catalytic degradation process of lignin, the lignin with abundant ß-O-4 linkages is beneficial to the downstream conversion of lignin into aromatic chemicals.

8.
Artigo em Inglês | MEDLINE | ID: mdl-31746521

RESUMO

Lithium-sulfur (Li-S) batteries are highly regarded as the next-generation energy storage devices because of their ultrahigh theoretical energy density of 2600 Wh kg -1 . Sulfurized polyacrylonitrile (SPAN) is considered as a promising sulfur cathode to substitute conventional carbon/sulfur (C/S) composite to afford higher Columbic efficiency, improved cycling stability, and potential high-energy-density Li-SPAN batteries which attract growing attentions. However, unstable Li metal anode critically threatens the actual performances of Li-SPAN batteries with limited lifespan and safety hazards . Considering Li metal can react with almost all kinds of electrolyte to generate a protective solid electrolyt e interphase ( SEI ), electrolyte r egulation is widely accepted as a vital and feasible strategy to protect Li metal anode in rechargeable batteries . In this review, basic principles and current challenges of Li-SPAN batteries are firstly addressed. Recent advances on electrolyte regulation towards stable Li metal anode in Li-SPAN batteries are summarized to afford design strategies of solvents, lithium salts, additives, and gel electrolyte. Finally, prospects for future electrolyte design and Li anode protection in Li-SPAN batteries are also discussed.

9.
Int J Biol Macromol ; 138: 519-527, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31348970

RESUMO

Understanding the distribution and structural features of lignin in heartwood, sapwood, and bark of terrestrial plants is important to optimize the industrial utilization of lignocellulose. In this work, the lignins in heartwood, sapwood, and bark of Eucalyptus urophylla × E. grandis were comparatively studied. Confocal Raman microscopy was used to probe the heterogeneity of lignin distribution in situ. The swollen residual enzyme lignin samples were isolated and systematically characterized to determine the structural differences. The results showed that the content and molecular weights of lignin gradually decreased in the order of heartwood, sapwood, and bark. The S/G ratios of heartwood lignin (3.45) and sapwood lignin (2.74) suggested the increase of deposited S-type lignin with the maturity of wood. The bark lignin exhibited a high frequency of ß-O-4' linkages and showed a unique substructural pattern with the absence of spirodienone substructures and p-hydroxycinnamyl alcohol end-groups.


Assuntos
Eucalyptus/química , Lignina/química , Casca de Planta/química , Madeira/química , Lignina/isolamento & purificação , Estrutura Molecular , Peso Molecular , Especificidade de Órgãos , Compostos Fitoquímicos/química , Compostos Fitoquímicos/isolamento & purificação , Termogravimetria
10.
Carbohydr Polym ; 222: 115008, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31320085

RESUMO

Amino cellulose (AC) is a cellulose derivative with biodegradability, biocompatibility, and excellent film-forming property, but AC film exhibits poor mechanical property and thermal stability. To improve the performance of AC film and further promote application, a novel composite film prepared from AC and bisphenol A-type-benzoxazine (BATB) are reported. In this paper, AC and BATB were firstly synthesized and characterized, then AC-BATB composite films were prepared with different weight ratios (AC/BATB) and temperatures by the synergistic interactions of chemical cross-linking and hydrogen bonds. Based on the results of tensile test and thermal analysis, BATB played a vital role in improving the mechanical and thermal properties of composite films, and the enhancement effect was more remarkable at elevated temperature. The maximum tensile strength and tensile modulus of composite films were 2.86 times and 7.26 times higher than that of AC control film, thus promoting the functional application of composite films.

11.
Int J Biol Macromol ; 134: 122-130, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31071408

RESUMO

A facile and green route is introduced to fabricate antimicrobial composite films in this article from xylan (XL) and hydroxyethyl cellulose (HEC) with citric acid (CA) and polyethylene glycol 400 (PEG-400) as crosslinker and plasticizer, respectively. XL was obtained by precipitating wood hydrolysate (WH) produced during pulping process with ethanol. Antimicrobial activity was constructed by incorporating ß-cyclodextrin/sodium benzoate (ß-CD/NaBz) complex into the composite matrix. The interactions, including hydrogen bonds and covalent bonds, between the polymers were confirmed by FT-IR spectroscopy. Morphology and crystallinity of composite films at different curing time were investigated by AFM and XRD, respectively. The composite film cured for 40 min exhibits tensile strength up to 62.3 MPa and oxygen permeability (OP) as low as 1.0 cm3·µm m-2·d-1·kPa-1. Finally, the antimicrobial test against Staphylococcus aureus reveals superior antimicrobial activity of composite films with complex. In conclusion, the XL/HEC antimicrobial film has great potential in the field of sustainable food packing materials.


Assuntos
Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Materiais Biocompatíveis/química , Materiais Biocompatíveis/farmacologia , Embalagem de Alimentos , Membranas Artificiais , Xilanos/química , Fenômenos Químicos , Fenômenos Mecânicos , Microscopia de Força Atômica , Estrutura Molecular , Solubilidade , Análise Espectral
12.
Bioresour Technol ; 285: 121335, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31003204

RESUMO

Reductive catalytic fractionation (RCF) has emerged as a new biorefinery paradigm for the fractionation and sequential utilization of entire components of biomass. Herein, we investigated the RCF of bamboo, a highly abundant herbaceous feedstock, in the presence of Pd/C catalyst. The lignin fraction in bamboo was preferentially depolymerized into well-defined low-molecular-weight phenols, with leaving carbohydrates pulp as a solid residue. In the soluble fraction, four major phenolic compounds, e.g., methyl coumarate/ferulate derived from hydroxycinnamic units and propanol guaiacol/syringol derived from ß-O-4 units, were generated up to 41.7 wt% yield based on original lignin content. In the insoluble fraction, the carbohydrates of bamboo were recovered with high retentions of cellulose (68%) and hemicellulose (49%), which upon treatment with enzyme gave glucose (90%) and xylose (85%). Overall, the three major components of bamboo could efficient to be fractionated and converted into useful platform chemicals on the basis of this study.


Assuntos
Celulose , Lignina , Biomassa , Catálise , Fracionamento Químico
13.
Carbohydr Polym ; 205: 135-142, 2019 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-30446088

RESUMO

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 ß-(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.

14.
J Agric Food Chem ; 67(3): 968-974, 2019 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-30580517

RESUMO

In the present study, lignin from eucalyptus was extracted with 80% alkaline dioxane (0.05 M NaOH) from ball-milled wood and subsequently fractionated by gradient acid precipitation from the filtrate. Meanwhile, the residual lignin was prepared by a double enzymatic hydrolysis process. The yield of the lignin extracted by alkaline dioxane (LA-2) was 29.5%. The carbohydrate contents and molecular weights of the gradient acid precipitated lignin fractions gradually decreased from 4.90 to 1.36% and from 7770 to 5510 g/mol, respectively, with the decline of the pH value from 6 to 2. Results from two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance (NMR) and 31P NMR spectroscopy showed an evident reduction of ß- O-4 ' linkages with the pH value decrease, while the contents of aliphatic -OH, phenolic -OH, and carboxylic groups displayed an increasing trend. Moreover, the residual lignin exhibited the highest molecular weight (11690 g/mol), the most abundant ß- O-4 ' linkages (71.1%), and the highest S/G ratio (4.68).


Assuntos
Eucalyptus/química , Lignina/química , Extratos Vegetais/química , Álcalis/química , Dioxanos/química , Concentração de Íons de Hidrogênio , Hidrólise , Lignina/isolamento & purificação , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , Extratos Vegetais/isolamento & purificação , Madeira/química
15.
Materials (Basel) ; 11(11)2018 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-30428577

RESUMO

Wood auto-hydrolysates (WAH) are obtained in the pulping process by the hydrothermal extraction, which contains lots of hemicelluloses and slight lignin. WAH and chitosan (CS) were introduced into this study to construct WAH-based films by the casting method. The FT-IR results revealed the crosslinking interaction between WAH and CS due to the Millard reaction. The morphology, transmittance, thermal properties and mechanical properties of composite WAH/CS films were investigated. As the results showed, the tensile strength, light transmittances and thermal stability of the WAH-based composite films increased with the increment of WAH/CS content ratio. In addition, the results of oxygen transfer rate (OTR) and water vapor permeability (WVP) suggested that the OTR and WVP values of the films decreased due to the addition of CS. The maximum value of tensile strengths of the composite films achieved 71.2 MPa and the OTR of the films was low as 0.16 cm³·µm·m-2·24 h-1·kPa-1, these properties are better than those of other hemicelluloses composite films. These results suggested that the barrier composite films based on WAH and CS will become attractive in the food packaging application for great mechanical properties, good transmittance and low oxygen transfer rate.

16.
J Agric Food Chem ; 66(45): 11981-11989, 2018 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-30376319

RESUMO

The generation of pseudo-lignin as byproduct during the lignocellulose acidic pretreatment has been proposed for many years. However, the detailed formation mechanism is still unclear. Moreover, there is a lack of understanding in the initial reaction during the formation of humins (byproducts in furfural production) and acid-induced hydrothermal carbon (carbon material). In this work, the initial formation of these three substances were investigated. We first found the common feature of their formation process was that carbohydrate-hydrolyzed compounds could form black polymers by condensing in acidic media, but the difference was dependent on the reaction degree. Furthermore, the results revealed that oxidation was an accelerator for condensations during producing black polymers because oxidized compounds could enhance the acidity of the reaction system. However, condensations of oxidized compounds were more difficult to proceed. Meanwhile, during the initial stage, the dominating pathway was that furfural condensed with itself and isomerized xylose via aldol-condensation.


Assuntos
Ácidos/química , Carbono/química , Substâncias Húmicas/análise , Lignina/química , Isomerismo , Oxirredução , Temperatura
17.
J Agric Food Chem ; 66(22): 5433-5438, 2018 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-29745662

RESUMO

Eucommia ulmoides Oliver (EUO), a traditional Chinese herb, contains a variety of bioactive chemicals, including lignans, iridoids, phenolics, steroids, terpenoids, flavonoids, etc. These bioactive chemicals possess the effective function in nourishing the liver and kidneys and regulating blood pressure. The composition of bioactive chemicals extracted from EUO vary in the different functional parts (leaves, seeds, bark, and staminate flower) and planting models. The bioactive parts of EUO are widely used as raw materials for medicine and food, powdery extracts, herbal formulations, and tinctures. These capabilities hold potential for future development and commercial exploitation of the bioactive products from EUO.


Assuntos
Ração Animal/análise , Eucommiaceae/química , Extratos Vegetais/química , Animais , Suplementos Nutricionais/análise , Suplementos Nutricionais/estatística & dados numéricos , Tratamento Farmacológico , Eucommiaceae/metabolismo , Humanos , Extratos Vegetais/metabolismo , Extratos Vegetais/farmacologia
18.
Carbohydr Polym ; 195: 114-119, 2018 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-29804958

RESUMO

Effect of sonication on the extractability and physico-chemical properties of hemicelluloses from Eucalyptus grandis using 5% KOH solution at 50 °C for 3 h has been comparatively studied. The results showed that the yield of hemicelluloses increased from 2.6 to 19.6% as the ultrasonic time was extended from 5 to 35 min. The highest yield of hemicelluloses (95.2%) was achieved at 30 min ultrasonic time. Xylose was the dominant sugar (82.94-84.96%) of all the hemicellulosic fractions. Furthermore, the hemicelluloses obtained by ultrasound-assisted extractions had slightly lower molecular weights (74,510-66,770 g/mol) and thermal stabilities, but higher contents of xylose (83.95-84.96%). The increased yield of ultrasonically extracted hemicelluloses, which have preserved their main structural properties, confirmed the great potential of ultrasound-assisted extraction to separate hemicelluloses from Eucalyptus grandis at an industrial level.

19.
Carbohydr Polym ; 195: 303-310, 2018 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-29804981

RESUMO

Chemical structure determination of xylo-oligosaccharides obtained by common production pathway is difficult, since the products mixture must be separated and purified into individual chemicals. In the present study, gel permeation chromatography was used to efficiently separate and purify the xylo-oligosaccharides produced by biomass autohydrolysis for the chemical structural evaluation. Results showed that the separation obtained high purity (85.2-94.5%) xylo-oligosaccharides with individual component. The separated samples were further characterized by ESI-MS and NMR, which revealed that the samples were non-substituted xylobiose and acetylated xylo-oligosaccharides with degree of polymerization from 3 to 6. The combined 1H, 13C and two-dimensional proton-detected heteronuclear single quantum (2D HSQC) NMR spectra results suggested that acetyl groups only attached to the internal units of xylo-oligosaccharides after autohydrolysis, and no acetylated non-reducing ends were detected.

20.
Biotechnol Biofuels ; 11: 137, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29774050

RESUMO

Background: To increase the production of bioethanol, a two-step process based on hydrothermal and dilute alkaline treatment was applied to reduce the natural resistance of biomass. However, the process required a large amount of water and a long operation time due to the solid/liquid separation before the alkaline treatment, which led to decrease the pure economic profit for production of bioethanol. Therefore, four one-step processes based on order of hydrothermal and alkaline treatment have been developed to enhance concentration of glucose of wheat straw by enzymatic saccharification. The aim of the present study was to systematically evaluated effect for different one-step processes by analyzing the physicochemical properties (composition, structural change, crystallinity, surface morphology, and BET surface area) and enzymatic saccharification of the treated substrates. Results: In this study, hemicelluloses and lignins were removed from wheat straw and the morphologic structures were destroyed to various extents during the four one-step processes, which were favorable for cellulase absorption on cellulose. A positive correlation was also observed between the crystallinity and enzymatic saccharification rate of the substrate under the conditions given. The surface area of the substrate was positively related to the concentration of glucose in this study. As compared to the control (3.0 g/L) and treated substrates (11.2-14.6 g/L) obtained by the other three one-step processes, the substrate treated by one-step process based on successively hydrothermal and alkaline treatment had a maximum glucose concentration of 18.6 g/L, which was due to the high cellulose concentration and surface area for the substrate, accompanying with removal of large amounts of lignins and hemicelluloses. Conclusions: The present study demonstrated that the order of hydrothermal and alkaline treatment had significant effects on the physicochemical properties and enzymatic saccharification of wheat straw. The one-step process based on successively hydrothermal and alkaline treatment is a simple operating and economical feasible method for the production of glucose, which will be further converted into bioethanol.

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