| 1. |
- del Rio, Jose C., et al.
(författare)
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Highly Acylated (Acetylated and/or p-Coumaroylated) Native Lignins from Diverse Herbaceous Plants
- 2008
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Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 56:20, s. 9525-9534
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Tidskriftsartikel (refereegranskat)abstract
- The structure of lignins isolated from the herbaceous plants sisal (Agave sisalana), kenaf (Hibiscus cannabinus), abaca (Musa textilis) and curaua (Ananas erectifolius) has been studied upon spectroscopic (2D-NMR) and chemical degradative (derivatization followed by reductive cleavage) methods. The analyses demonstrate that the structure of the lignins from these plants is highly remarkable, being extensively acylated at the gamma-carbon of the lignin side chain (up to 80% acylation) with acetate and/or p-coumarate groups and preferentially over syringyl units. Whereas the lignins from sisal and kenaf are gamma-acylated exclusively with acetate groups, the lignins from abaca and curaua are esterified with acetate and p-coumnarate groups. The structures of all these highly acylated lignins are characterized by a very high syringyl/guaiacyl ratio, a large predominance of beta-O-4' linkages (up to 94% of all linkages), and a strikingly low proportion of traditional beta-beta' linkages, which indeed are completely absent in the lignins from abaca and curaua. The occurrence of beta-beta' homocoupling and cross-coupling products of sinapyl acetate in the lignins from sisal and kenaf indicates that sinapyl alcohol is acetylated at the monomer stage and that, therefore, sinapyl acetate should be considered as a real monolignol involved in the lignification reactions.
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| 2. |
- del Rio, Jose C., et al.
(författare)
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Structural Characterization of the Lignin from Jute (Corchorus capsularis) Fibers
- 2009
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Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 57:21, s. 10271-10281
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Tidskriftsartikel (refereegranskat)abstract
- The structural characteristics of the lignin from jute (Corchorus capsularis) fibers, which are used for high-quality paper pulp production, were studied. The lignin content (13.3% Klason lignin) was high compared to other nonwoody bast fibers used for pulp production. The lignin structure was characterized by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), 2D-NMR, and thioacidolysis. Upon Py-GC/MS, jute fibers released predominantly products from syringylpropanoid units with the S/G ratio being 2.1 and a H/G/S composition of 2:33:65. 2D-NMR of the milled wood lignin (MWL) isolated from jute fibers showed a predominance of beta-O-4' aryl ether linkages (72% of total side chains), followed by beta-beta' resinol-type linkages (16% of total side chains) and lower amounts of beta-5' phenylcoumaran (4%) and beta-1' spirodienone-type (4%) linkages and cinnamyl end groups (4%). The high predominance of the S-lignin units, together with the high proportion of beta-O-4' aryl ether linkages, which are easily cleaved during alkaline cooking, are advantageous for pulping. On the other hand, a small percentage (ca. 4%) of the lignin side chain was found to be acetylated at the gamma-carbon, predominantly over syringyl units. The analysis of desulphurated thioacidolysis dimers provided additional information on the relative abundances of the various carbon-carbon and diaryl ether bonds and the type of units (syringyl or guaiacyl) involved in each of the above linkage types. Interestingly, the major part of the beta-beta' dimers included two syringyl units, indicating that most of the beta-beta' substructures identified in the HSQC spectra were of the syringaresinol type (pinoresinol being absent), as already observed in the lignin of other angiosperms.
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| 3. |
- Du, Xueyu, et al.
(författare)
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Analysis of lignin-carbohydrate and lignin-lignin linkages after hydrolase treatment of xylan-lignin, glucomannan-lignin and glucan-lignin complexes from spruce wood
- 2014
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Ingår i: Planta. - : Springer Science and Business Media LLC. - 0032-0935 .- 1432-2048. ; 239:5, s. 1079-1090
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Tidskriftsartikel (refereegranskat)abstract
- Xylan-lignin (XL), glucomannan-lignin (GML) and glucan-lignin (GL) complexes were isolated from spruce wood, hydrolyzed with xylanase or endoglucanase/beta-glucosidase, and analyzed by analytical pyrolysis and 2D-NMR. The enzymatic hydrolysis removed most of the polysaccharide moieties in the complexes, and the lignin content and relative abundance of lignin-carbohydrate linkages increased. Analytical pyrolysis confirmed the action of the enzymatic hydrolysis, with strong decreases of levoglucosane and other carbohydrate-derived products. Unexpectedly it also revealed that the hydrolase treatment alters the pattern of lignin breakdown products, resulting in higher amounts of coniferyl alcohol. From the anomeric carbohydrate signals in the 2D-NMR spectra, phenyl glycoside linkages (undetectable in the original complexes) could be identified in the hydrolyzed GML complex. Lower amounts of glucuronosyl and benzyl ether linkages were also observed after the hydrolysis. From the 2D-NMR spectra of the hydrolyzed complexes, it was concluded that the lignin in GML is less condensed than in XL due to its higher content in beta-O-4' ether substructures (62 % of side chains in GML vs 53 % in XL) accompanied by more coniferyl alcohol end units (16 vs 13 %). In contrast, the XL lignin has more pinoresinols (11 vs 6 %) and dibenzodioxocins (9 vs 2 %) than the GML (and both have similar to 13 % phenylcoumarans and 1 % spirodienones). Direct 2D-NMR analysis of the hydrolyzed GL complex was not possible due to its low solubility. However, after sample acetylation, an even less condensed lignin than in the GML complex was found (with up to 72 % beta-O-4' substructures and only 1 % pinoresinols). The study provides evidence for the existence of structurally different lignins associated to hemicelluloses (xylan and glucomannan) and cellulose in spruce wood and, at the same time, offers information on some of the chemical linkages between the above polymers.
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| 4. |
- Du, Xueyu, et al.
(författare)
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Lignin-carbohydrate and lignin-lignin linkages in different lignin-carbohydrate complexes from spruce wood
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In order to characterize lignin-carbohydrate (LC) and lignin-lignin (LL) linkages in different lignin-carbohydrate complexes (LCCs), the glucan-lignin (GL), glucomannan-lignin (GML) and xylan-lignin (XL) isolated from spruce wood have been enzymatically hydrolyzed, using endoglucanase plus b-glucosidase (for GL and GML) or xylanase (for XL), followed by 2D HSQC NMR and Py-GC/MS analysis. It has been found that the enzymatic hydrolysis removed effectively most of the polysaccharide parts in the LCCs and thus enriched the lignin contents and LCC linkages so that various LC and LL linkages could be well demonstrated by the 2D HSQC NMR analysis. Three typical LC linkages, i.e. benzyl ether, γ-ester and phenyl glycoside, have been directly observed in the enzymatically hydrolyzed GML (En-GML) and enzymatically hydrolyzed XL (En-XL). There are two types of benzyl ether linkages, with primary and secondary OH from carbohydrates. There are three types of carbohydrate units linked with lignin by the phenyl glycoside bonds in the En-GML while only one type is found in the En-XL. It seems that mannose and galactose are among the sugar units involved in the linkages since their relative amounts in the sugar compositions increased after the enzymatic hydrolysis. From the LL linkages observed in the 2D HSQC NMR spectra, it was revealed that the lignin existing in GML is less condensed than the lignin from XL due to a higher percentage of β-O-4 sub-structure found in the former (75 % vs. 66 %). On the other hand, more other substructures have been found present in the lignin from XL than GML, e.g. phenylcoumaran (17 % vs. 15 %), dibenzodioxocin (9 % vs. 5 %), resinol (11 % vs. 6 %), and spirodienone (2 % vs. 1 %), implying more condensed lignin structures present in the XL. From the Py-GC/MS analysis, the relative amounts of guaiacol and coniferyl alcohol fragments over the acetoguaiacone fragment, an internal marker, were largely increased after the enzymatic hydrolysis, supporting the presences of even higher amounts of the phenyl glucoside LC linkages in the original LCCs since some of the linkages should have been cleaved during the enzymatic hydrolysis. The NMR analysis of the En-GL was not successful probably due to the attachment of the enzymes onto the GL structure or the existence of the remained crystalline cellulose structures.
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| 5. |
- Du, Xueyu, et al.
(författare)
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Understanding Pulp Delignification by Laccase-Mediator Systems through Isolation and Characterization of Lignin-Carbohydrate Complexes
- 2013
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 14:9, s. 3073-3080
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Tidskriftsartikel (refereegranskat)abstract
- The effects and mechanism of pulp delignificabon by laccases in the presence of redox mediators have been investigated on unbleached eucalyptus kraft pulp treated with laccases from Pycnoporus cinnabarinus (PcL) and Myceliophthora thermophila (MtL) and 1-hydroxybenzotriazole (HBT) and methyl syringate (MeS) as mediators, respectively. Determination of the corrected kappa number in eucalyptus pulps after the enzymatic treatments revealed that the PcL-HBT system exhibited a more remarkable delignification effect than the MtL-MeS system. To obtain further insight, lignin-carbohydrate complexes were fractionated and subsequently characterized by nuclear magnetic resonance, thioacidolysis (followed by gas chromatography and size exclusion chromatography), and pyrolysis-gas chromatography-mass spectrometry (pyrolysis-GC-MS) analyses before and after the enzymatic treatments and their controls. We can conclude that the laccase mediator treatments altered the lignin structures in such a way that more lignin was recovered in the xylan-lignin fractions, as shown by Klason lignin estimation, with smaller amounts of both syringyl (5) and guaiacyl (G) uncondensed units, as shown by thioacidolysis and gas chromatography, especially after the PcL-HBT treatment. The laccase mediator treatment produced oxidation at C alpha and cleavage of C alpha and C beta bonds in pulp lignin, as shown by pyrolysis-GC-MS. The general mechanism of residual lignin degradation in the pulp by laccase-mediator treatments is discussed in light of the results obtained.
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| 6. |
- Prasetyo, Endry Nugroho, et al.
(författare)
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Polymerization of lignosulfonates by the laccase-HBT (1-hydroxybenzotriazole) system improves dispersibility
- 2010
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 101:14, s. 5054-5062
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Tidskriftsartikel (refereegranskat)abstract
- The ability of laccases from Trametes villosa (TvL), Myceliophthora thermophila (MtL), Trametes hirsuta (ThL) and Bacillus subtilis (BsL) to improve the dispersion properties of calcium lignosulfonates 398 in the presence of HBT as a mediator was investigated. Size exclusion chromatography showed an extensive increase in molecular weight of the samples incubated with TvL and ThL by 107% and 572% from 28400 Da after 17 h of incubation, respectively. Interestingly, FTIR spectroscopy. C-13 NMR and Py-GC/MS analysis of the treated samples suggested no substantial changes in the aromatic signal of the lignosulfonates, a good indication of the ability of TvL/ThL-HBT systems to limit their effect on functional groups without degrading the lignin backbone. Further, the enzymatic treatments led to a general increase in the dispersion properties, indeed a welcome development for its application in polymer blends. (C) 2010 Elsevier Ltd. All rights reserved.
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| 7. |
- Rencoret, Jorge, et al.
(författare)
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Structural characterization of milled wood lignins from different eucalypt species
- 2008
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Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 62:5, s. 514-526
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Tidskriftsartikel (refereegranskat)abstract
- The chemical structure of milled-wood lignins from Eucalyptus globulus, E. nitens, E. maidenii, E. grandis, and E. dunnii was investigated. The lignins were characterized by analytical pyrolysis, thioacidolysis, and 2D-NMR that confirmed the predominance of syringyl over guaiacyl units and only showed traces of p-hydroxyphenyl units. E. globulus lignin had the highest syringyl content. The heteronuclear single quantum correlation (HSQC) NMR spectra yielded information about relative abundances of inter-unit linkages in the whole polymer. All the lignins showed a predominance of beta-O-4' ether linkages (66-72% of total side-chains), followed by beta-beta' resinol-type linkages (16-19%) and lower amounts of beta-5' phenylcoumarin-type (3-7%) and beta-1' spirodienone-type linkages (1-4%). The analysis of desulfurated thioacidolysis dimers provided additional information on the relative abundances of the various carbon-carbon and diaryl ether bonds, and the type of units ( syringyl or guaiacyl) involved in each of the above linkage types. Interestingly, 93-94% of the total beta-beta' dimers included two syringyl units indicating that most of the beta-beta' substructures identified in the HSQC spectra were of the syringaresinol type. Moreover, three isomers of a major trimeric compound were found which were tentatively identified as arising from a beta-beta' syringaresinol substructure attached to a guaiacyl unit through a 4-O-5' linkage.
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| 8. |
- Ruthes, Andrea C., et al.
(författare)
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Comparative Recalcitrance and Extractability of Cell Wall Polysaccharides from Cereal (Wheat, Rye, and Barley) Brans Using Subcritical Water
- 2020
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 8:18, s. 7192-7204
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Tidskriftsartikel (refereegranskat)abstract
- Cereal brans constitute an unexploited source of valuable cell wall polysaccharides and phenolics. Sequential subcritical water extraction (SWE) of wheat, barley, and rye bran enables the isolation of cell wall polysaccharides with targeted molecular structures. The extracts switched from glucan-rich to higher contents of feruloylated arabinoxylan (F-AX) with extraction time, resulting in significant radical scavenging activity. Structurally, wheat and rye F-AXs exhibited mostly single C(O)-3 arabinose substitutions, whereas barley bran F-AX showed a complex substitution pattern. The recalcitrance of the insoluble residues after SWE was revealed by the enrichment of F-AX populations with disubstituted arabinose units and the presence of hydroxycinnamic acids, lignin, and proteins. This study demonstrates the versatility of SWE to extract cell wall polysaccharides from cereal brans with tailored molecular structures and radical scavenging activity for potential use in food and biomedical applications.
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| 9. |
- Vanholme, Bartel, et al.
(författare)
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Accumulation of N-Acetylglucosamine Oligomers in the Plant Cell Wall Affects Plant Architecture in a Dose-Dependent and Conditional Manner
- 2014
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 165:1, s. 290-308
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Tidskriftsartikel (refereegranskat)abstract
- To study the effect of short N-acetylglucosamine (GlcNAc) oligosaccharides on the physiology of plants, N-ACETYLGLUCOSAMINYLTRANSFERASE (NodC) of Azorhizobium caulinodans was expressed in Arabidopsis (Arabidopsis thaliana). The corresponding enzyme catalyzes the polymerization of GlcNAc and, accordingly, beta-1,4-GlcNAc oligomers accumulated in the plant. A phenotype characterized by difficulties in developing an inflorescence stem was visible when plants were grown for several weeks under short-day conditions before transfer to long-day conditions. In addition, a positive correlation between the oligomer concentration and the penetrance of the phenotype was demonstrated. Although NodC overexpression lines produced less cell wall compared with wildtype plants under nonpermissive conditions, no indications were found for changes in the amount of the major cell wall polymers. The effect on the cell wall was reflected at the transcriptome level. In addition to genes encoding cell wall-modifying enzymes, a whole set of genes encoding membrane- coupled receptor-like kinases were differentially expressed upon GlcNAc accumulation, many of which encoded proteins with an extracellular Domain of Unknown Function26. Although stress-related genes were also differentially expressed, the observed response differed from that of a classical chitin response. This is in line with the fact that the produced chitin oligomers were too small to activate the chitin receptor-mediated signal cascade. Based on our observations, we propose a model in which the oligosaccharides modify the architecture of the cell wall by acting as competitors in carbohydrate-carbohydrate or carbohydrate-protein interactions, thereby affecting noncovalent interactions in the cell wall or at the interface between the cell wall and the plasma membrane.
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