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New method for the quantitative preparation of lignin-carbohydrate complex from unbleached softwood kraft pulp: Lignin-polysaccharide networks I
KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.ORCID-id: 0000-0002-8614-6291
KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.ORCID-id: 0000-0001-8817-2031
KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
2003 (Engelska)Ingår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 57, nr 1, s. 69-74Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

A new method for the quantitative preparation of pulp representative lignin-carbohydrate complexes (LCC) has been developed, in which LCC has been systematically prepared at quantitative yield, fractionated and qualitatively determined. At least 90% of residual lignin in softwood kraft pulp is proposed to be chemically bonded to carbohydrates. A major part of LCC (92%) in softwood kraft pulp was observed between lignin, xylan and glucomannan, whereas a minor part (8%) was linked to cellulose. Half of the hemicelullosic LCC is a lignin-glucomannan complex. The other half is lignin-xylan complex and xylan-lignin-glucomannan complex. Thus, part of the residual lignin in softwood kraft pulp crosslinks xylan and glucomannan. The proposed linkages are of covalent type. At most 10% of the residual lignin is not bonded covalently to carbohydrates.

Ort, förlag, år, upplaga, sidor
2003. Vol. 57, nr 1, s. 69-74
Nyckelord [en]
Endoglucanase, Lignin-carbohydrate complex (LCC), Residual lignin
Nationell ämneskategori
Pappers-, massa- och fiberteknik
Identifikatorer
URN: urn:nbn:se:kth:diva-7817DOI: 10.1515/HF.2003.011ISI: 000181276300011Scopus ID: 2-s2.0-0037280451OAI: oai:DiVA.org:kth-7817DiVA, id: diva2:12953
Anmärkning
QC 20100923Tillgänglig från: 2005-10-20 Skapad: 2005-10-20 Senast uppdaterad: 2022-10-11Bibliografiskt granskad
Ingår i avhandling
1. Lignin polysaccharide networks in softwood and chemical pulps: characterisation, structure and reactivity
Öppna denna publikation i ny flik eller fönster >>Lignin polysaccharide networks in softwood and chemical pulps: characterisation, structure and reactivity
2005 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

The chemical interactions between the main wood components i.e., cellulose, hemicelluloses and lignin are of fundamental importance for understanding the chemical aspects of wood formation and its reactivity during fibre processing e.g during chemical pulping of wood. Future progress in the development of new high value products from wood will greatly depend on a detailed knowledge of how the fibre elements interact with each other in the biological material. The existence of covalent bonds between lignin and carbohydrates (LCC) has been one of the most controversial issues in the field of wood chemistry. Only until recently, the existence of such bonds has in its entirety been shown by way of indirect analyses, normally suffering from low yields obtained at rather drastic conditions. Furthermore, previous studies on LCC have been targeted on studying the specific lignin carbohydrate linkage and less emphasis has been put on the whole LCC networks. Detailed structural studies of entire LCC are therefore of importance in understanding the chemistry involved in wood formation and wood reactivity.

The aim of this study was to isolate intact LCC from wood and corresponding chemical pulps made from it in quantitative yield and to clarify their detailed chemical structure. For the first time, a method for the quantitative analysis of lignin-carbohydrate complexes (LCCs) in softwood is presented and it could be concluded that no carbohydrate-free lignin was present in these wood fibres. From mildly ball-milled wood, all lignin was isolated as LCCs in a sequence involving a partial enzymatic hydrolysis of cellulose, subsequent swelling and quantitative dissolution, into 4 major fractions; a galactoglucomannan-lignin-pectin LCC (GalGlcMan-L-P) containing ~8% of the wood lignin, a glucane LCC (Glc-L) containing ~4% of the wood lignin, a xylan-lignin-glucomannan network LCC (Xyl-L-GlcMan) (with a predominance of xylan over glucomannan) containing ~40% of the wood and a glucomannan-lignin-xylan network LCC (GlcMan-L-Xyl) (with a predominance of glucomannan over xylan) containing ~48% of the wood lignin.

From unbleached kraft pulps, 85 - 90% of residual lignin was found to be chemically bonded to carbohydrates. The effect of the degree of delignification on the LCC types during kraft pulping and during subsequent oxygen stage was studied in order to understand the role of LCC for the stability of residual lignin. For both processes, high delignification rates were observed for the xylan-rich LCC and cellulose-rich LCC fractions, whereas the glucomannan-rich LCC was relatively stable. After a severe oxygen stage, almost all the residual lignin was isolated in the latter complex.

Thioacidolysis in combination with gas chromatography was used to determine the content of β-O-4 structures in the lignin. Periodate oxidation and methanol determinations were used to quantify the phenolic hydroxyl groups, whereas size exclusion chromatography (SEC) of the thioacidolysis fractions was used to monitor any differences between the original molecular size distribution and that after the delignification processes. Major differences between the various LCC fractions were observed, clearly indicating that two different forms of lignin are present in the wood fibre wall. These forms are linked to glucomannan and xylan respectively. The xylan linked lignin was found to consist largely of β-O-4 structures indicating a rather linear coupling mode, whereas the glucomannan linked lignin was more heterogeneous with respect to the known lignin inter-unit linkage types. Based on these findings, a modified arrangement of the fibre wall polymers is suggested. From acid sulfite pulp (Kappa number 11) residual lignin was isolated at ~80% yield on LCC basis. About 60% was linked to xylan, 30% to glucomannan and 10% to glucans. These values differ greatly from those obtained for softwood pulped to a similar kappa number by the Kraft method. Model compound studies indicated that the benzyl ether type of LC linkage were likely to survive cleavage at the acidic sulfite pulping conditions

Ort, förlag, år, upplaga, sidor
Stockholm: KTH, 2005. s. 58
Serie
Trita-FPT-Report, ISSN 1652-2443 ; 2005:30
Nationell ämneskategori
Pappers-, massa- och fiberteknik
Identifikatorer
urn:nbn:se:kth:diva-458 (URN)
Disputation
2005-10-28, STFI-salen, Drottning Kristinasväg 61, Stockholm, 10:00
Opponent
Handledare
Anmärkning
QC 20101026Tillgänglig från: 2005-10-20 Skapad: 2005-10-20 Senast uppdaterad: 2022-06-26Bibliografiskt granskad

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Lawoko, MartinHenriksson, GunnarGellerstedt, Göran
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