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A method for studying effects on lignin-polysaccharide networks during degradation and technical processing of wood
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.ORCID iD: 0000-0001-8135-588X
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
(English)Manuscript (preprint) (Other academic)
Identifiers
URN: urn:nbn:se:kth:diva-149642OAI: oai:DiVA.org:kth-149642DiVA: diva2:740453
Note

QS 2014

Available from: 2014-08-25 Created: 2014-08-25 Last updated: 2014-09-03Bibliographically approved
In thesis
1. A biomimicking approach for hemicellulose processing
Open this publication in new window or tab >>A biomimicking approach for hemicellulose processing
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Lignocellulose can become the best opportunity for the society to reduce its dependency on the harmful petroleum based products as well as to produce clean energy. In each part of the production cycle, biomass based products have a better environmental profiles than their petroleum based counterparts. Woody biomass has a vast availability, but it suffers from recalcitrance that is mostly caused by lignin that is functioning as a matrix, surrounding and binding the carbohydrates that are currently the most valuable of the wood components.

Lignin-carbohydrate (LC) bonds are believed to be a key element in this recalcitrance and research has shown that these types of bonds are common in wood. These bonds are important in an economical point of view as well, as e.g. residual lignin structures in pulp (lignins bonded to the cellulose and hemicelluloses) require expensive bleaching sequences for their removal.

The LC-structures can also be exploited technically as we now have demonstrated. We developed a method that utilizes phenolic end groups that are bonded to different hemicelluloses for cross-linking. The enzyme laccase was used for the cross-linking to create a cost-efficient processing scheme to both isolate and increase the molecular weight of the hemicelluloses. Membrane filtration was used as the key separation technique, which enables the establishment of industrial scale production. The final product had improved mechanical and thermal properties and could be used e.g. as barrier film component in renewable packaging. Nanocomposite formation with nanofibrillated cellulose was also studied. This improved the film properties further. The complexes are also possible to use as model compounds for lignin-carbohydrate complexes in wood.

This technique can also be seen to mimick the lignification and lignin-carbohydrate network formation phenomena in plants enabling the formation of entire networks of wood components. Our results suggests that the side chains of hemicellulose might play an important role in network formation and that hemicellulose molecules can carry more than one lignin phenolic end group to fulfill this capability.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. 50 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2014:30
Keyword
Mechanical pulping, Hemicellulose, Cross-linking, Lignin-carbohydrate-complex
National Category
Polymer Technologies
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-148586 (URN)978-91-7595-221-5 (ISBN)
Public defence
2014-09-05, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 621-2008-4177Knut and Alice Wallenberg FoundationVinnova, 2011-03387
Note

QC 20140825

Available from: 2014-08-25 Created: 2014-08-08 Last updated: 2014-08-25Bibliographically approved
2. Pretreatment and Enzymatic Treatment of Spruce: A functional designed wood components separation for a future biorefinery
Open this publication in new window or tab >>Pretreatment and Enzymatic Treatment of Spruce: A functional designed wood components separation for a future biorefinery
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The three main components of wood, namely, cellulose, hemicellulose, and lignin, can be used in various areas. However, since lignin covalently crosslinks with wood polysaccharides creating networks that is an obstacle for extraction, direct extraction of different wood components in high yield is not an easy matter. One potential approach to overcome such obstacles is to treat the wood with specific enzymes that degrade the networks by specific catalysis. However, the structure of wood is so compact that the penetration of the wood fibers by large enzyme molecules is hindered. Thus, the pretreatment of wood prior to the application of enzymes is necessary, for “opening” the structure.

One pretreatment method that was performed in this thesis is based on kraft pulping, which is a well-established and industrialized technique. For untreated wood, the wood fibers cannot be attacked by the enzymes. A relatively mild pretreatment was sufficient for wood polysaccharides hydrolyzed by a culture filtrate. A methanol-alkali mixture extraction was subsequently applied to the samples that were pretreated with two types of hemicellulases, Gamanase and Pulpzyme HC, respectively. The extraction yield increased after enzymatic treatment, and the polymers that were extracted from monocomponent enzyme-treated wood had a higher degree of polymerization. Experiments with in vitro prepared lignin polysaccharide networks suggested that the increased extraction was due to the enzymatic untying. However, the relatively large loss of hemicellulose, particularly including (galacto)glucomannan (GGM), represents a problem with this technique. To improve the carbohydrate yield, sodium borohydride (NaBH4), polysulfide and anthraquinone were used, which increased the yields from 76.6% to 89.6%, 81.3% and 80.0%, respectively, after extended impregnation (EI). The additives also increased the extraction yield from approximately 9 to 12% w/w wood. Gamanase treatment prior to the extraction increased the extraction yield to 14% w/w wood.

Sodium dithionite (Na2S2O4) is an alternative reducing agent for the preservation of hemicelluloses because it is less expensive than metal hydrides and only contains sodium and sulfur, which will not introduce new elements to the recovery system. Moreover, Na2S2O4has the potential to be generated from black liquor. Na2S2O4 has some preservation effect on hemicelluloses, and the presence of Na2S2O4 also contributed to delignification. The extraction yield increased to approximately 15% w/w wood. Furthermore, Na2S2O4 has been applied in the kraft pulping process of spruce. The yield and viscosity increased, while the Klason lignin content and kappa number decreased, which represents a beneficial characteristic for kraft pulp. The brightness and tensile strength of the resulting sheets also improved. However, the direct addition of Na2S2O4 to white liquor led to greater reject content. This problem was solved by pre-impregnation with Na2S2O4 and/or mild steam explosion (STEX) prior to the kraft pulping process. Following Na2S2O4 pre-impregnation and mild STEX, the obtained kraft pulp had substantially better properties compared with the properties exhibited after direct addition of Na2S2O4 to the white liquor.

The wood structure opening efficiency of mild STEX alone was also tested. The accessibility of the wood structure to enzymes was obtained even at very modest STEX conditions, according to a reducing sugar analysis, and was not observed in untreated wood chips, which were used as a reference. The mechanical effect of STEX appears to be of great importance at lower temperatures, and both chemical and mechanical effects occur at higher STEX temperatures. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. 59 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2014:28
Keyword
kraft cooking; extended impregnation; enzymes; chemo-enzymatic separation process; peeling reaction; sodium borohydride; polysulfide; anthraquinone; sodium dithionite; mild steam explosion; biorefinery.
National Category
Chemical Engineering Polymer Chemistry Paper, Pulp and Fiber Technology
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-150395 (URN)978-91-7595-206-2 (ISBN)
Public defence
2014-09-24, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Knut and Alice Wallenberg Foundation, 8102
Note

QC 20140903

Available from: 2014-09-03 Created: 2014-09-02 Last updated: 2014-09-03Bibliographically approved

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