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Extraction of Polymeric Hemicelluloses from Spruce 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.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Hemicelluloses are one of the three main components of spruce wood and constitute about 20% of the wood material. During mechanical pulping, 5–10% of the hemicelluloses are accumulated in waste waters, whereas during chemical pulping 70–80% of the hemicelluloses are lost in process liquors. The concept of integrated forest biorefinery involves the development of methods to extract these hemicelluloses prior to pulping in order to produce value-­added products besides pulp. This thesis describes some of the feasible possibilities of extracting hemicelluloses from wood at a high molecular weight prior to pulping in addition to presenting a deeper understanding of their degradation under mild treatment conditions.

A major obstacle for the efficient extraction of hemicelluloses is the recalcitrance due to the network of lignin and polysaccharides. This network can be loosely opened by the use of enzymes and this improves the extraction of hemicelluloses. A chemical impregnation of the wood chips was performed to enhance the accessibility of the cell wall to enzymes. The ability of different additives to stabilize the hemicelluloses against peeling during the alkaline impregnation stage was also investigated in order to obtain a better yield in subsequent extraction.

Increasing the surface area and decreasing the mass transport length could also improve the yield of hemicelluloses extracted from wood. This was achieved with a mild mechanical pre-­treatment of wood chips using an impressafiner and a fiberizer. Polymers mainly consisting of galactoglucomannan with an average molecular weight of 30 kDa were extracted from fiberized wood with water.

Different pre-­treatment and extraction methods were combined to demonstrate the concept of material biorefinery based on wood.

The kinetics of degradation of spruce galactoglucomannan were studied under alkaline conditions. It was degraded in two phases at two different rates. A kinetic model was developed to fit the experimental data and to estimate the activation energies. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , 50 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:4
National Category
Engineering and Technology
Research subject
Fibre and Polymer Science
Identifiers
URN: urn:nbn:se:kth:diva-158966OAI: oai:DiVA.org:kth-158966DiVA: diva2:781407
Public defence
2015-02-06, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20150119

Available from: 2015-01-19 Created: 2015-01-16 Last updated: 2015-01-19Bibliographically approved
List of papers
1. Stabilisation of polysaccharides during alkaline pretreatment of wood combined with enzyme-supported extractions in a biorefinery
Open this publication in new window or tab >>Stabilisation of polysaccharides during alkaline pretreatment of wood combined with enzyme-supported extractions in a biorefinery
2015 (English)In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 35, no 2, 91-101 p.Article in journal (Refereed) Published
Abstract [en]

Specific enzymes have been demonstrated to increase the possibilities for extracting wood polymers. Enzymatic treatment requires an open wood structure, which was achieved by extended impregnation of the wood. However, some of the hemicelluloses, primarily glucomannan, and lignin were lost during the impregnation. To improve the carbohydrate yield, three glucomannan modification agents: sodium borohydride, polysulphide and anthraquinone, were used, which increased the yields of the impregnated materials from 76.6% to 89.6%, 81.3% and 80.0%, respectively. Through the use of additives, most of the glucomannan could be retained in the wood while still allowing the enzymes to penetrate the wood and attack the polymers. The additives also increased the extraction yield from 9 to 12% w/w wood. Gamanase treatment prior to the extraction increased the extraction yield to 14%. Of the three stabilising agents, sodium borohydride was the most efficient, providing the highest extraction yields.

Keyword
extended impregnation, peeling reaction, sodium borohydride (NaBH4), polysulphide (PS), anthraquinone (AQ), extraction, biorefinery
National Category
Polymer Technologies
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-150392 (URN)10.1080/02773813.2013.875041 (DOI)000345585100001 ()2-s2.0-84913587206 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation, 8102
Note

Updated from manuscript to article in journal.

QC 20150115

Available from: 2014-09-02 Created: 2014-09-02 Last updated: 2017-12-05Bibliographically approved
2. Extraction of polymers from enzyme-treated softwood
Open this publication in new window or tab >>Extraction of polymers from enzyme-treated softwood
Show others...
2011 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 6, no 4, 4606-4614 p.Article in journal (Refereed) Published
Abstract [en]

In a biorefinery context it is an advantage to fractionate and extract different wood components in a relatively pure form. However, one major obstacle for efficient extraction of wood polymers (lignin, polysaccharides etc.) is the covalent lignin-polysaccharide networks present in lignified cell walls. Enzymatic catalysis might be a useful tool for a controlled degradation of these networks, thereby enhancing the extraction of high molecular weight polymers. In this work, a methanol-alkali mixture was used to extract two different wood samples treated with endoxylanase and gammanase, respectively. Wood chips were pretreated with alkali prior to enzymatic treatment to enhance the cell-wall accessibility to enzymes. Extractions were also carried out on non-enzyme-treated samples to evaluate the enzymatic effects. Results showed that the enzymatic treatment increased the extraction yield, with gammanase as the more efficient of the two enzymes. Furthermore, polymers extracted from xylanase-treated wood had a higher degree of polymerization than the reference.

National Category
Engineering and Technology
Research subject
SRA - Production
Identifiers
urn:nbn:se:kth:diva-49731 (URN)000298119500071 ()2-s2.0-84863040860 (Scopus ID)
Funder
XPRES - Initiative for excellence in production research
Note
QC 20111130Available from: 2011-11-29 Created: 2011-11-29 Last updated: 2017-12-08Bibliographically approved
3. Extraction of hemicelluloses from fiberized spruce wood
Open this publication in new window or tab >>Extraction of hemicelluloses from fiberized spruce wood
2015 (English)In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 117, 19-24 p.Article in journal (Refereed) Published
Abstract [en]

A novel mechanical pre-treatment method was used to separate the wood chips into fiber bundles in order to extract high molecular weight wood polymers. The mechanical pre-treatment involved chip compression in a conical plug-screw followed by defibration in a fiberizer. The fiberized wood was treated with hot water at various combinations of time and temperature in order to analyze the extraction yield of hemicelluloses at different conditions. Nearly 6 mg/g wood of galactoglucomannan was obtained at 90◦C/120min which was about three times more than what could be extracted from wood chips. The extracted carbohydrates had molecular weight ranging up to 60 kDa. About 10% of each of the extracted material had a molecular weight above 30 kDa. The extraction liquor could also be reused for consecutive extractions with successive increase in the extraction yield of hemicelluloses. 

Keyword
Spruce (Picea abies), Mechanical pre-treatment, Fiberized wood, Hemicelluloses, Galactoglucomannan
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-158963 (URN)10.1016/j.carbpol.2014.09.050 (DOI)000346263800003 ()2-s2.0-84922311559 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20150116

Available from: 2015-01-16 Created: 2015-01-16 Last updated: 2017-12-05Bibliographically approved

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