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Behavior of different monocomponent endoglucanases on the accessibility and reactivity of dissolving-grade pulps for viscose process
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), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
2010 (English)In: Enzyme and microbial technology, ISSN 0141-0229, E-ISSN 1879-0909, Vol. 47, 355-362 p.Article in journal (Refereed) Published
Abstract [en]

Three different commercial monocomponent endoglucanases, with and without a cellulose-binding domain (CBD) and differences in their glycosidic hydrolysis mechanisms, were compared with respect to their ability to enhance the accessibility and reactivity of dissolving-grade pulps for viscose production. Hardwood (eucalyptus) and softwood (mixture of Norway spruce and Scots pine) commercial dried and never-dried bleached sulfite dissolving pulps were used for this purpose. The effects of the enzymatic treatments on pulps were studied by reactivity, according to Fock's method, and viscosity measurements, and recording of molecular weight distributions. Among the different assayed enzymes, endoglucanase with a CBD and an inverting hydrolysis mechanism was found to be the most effective in increasing the reactivity of both pulps. Simultaneously, the viscosity decreased, being more marked for softwood dissolving pulp. A narrower molecular weight distribution, with a great reduction in the amount of long-chain cellulose molecules was observed in both pulps, being more pronounced for softwood dissolving pulp. By contrast, endoglucanase without a CBD and a retaining hydrolysis mechanism showed a barley enhancement of the studied properties. The effects of the different endoglucanase treatments were more pronounced when never-dried dissolving pulps were used.

Place, publisher, year, edition, pages
2010. Vol. 47, 355-362 p.
Keyword [en]
Hardwood, Softwood, Dissolving-grade pulp, Endoglucanase (EG), Cellulose-binding domain (CBD), Reactivity, Viscosity, Molecular weight distribution (MWD)
National Category
Paper, Pulp and Fiber Technology
Identifiers
URN: urn:nbn:se:kth:diva-26984DOI: 10.1016/j.enzmictec.2010.07.016ISI: 000284346000008Scopus ID: 2-s2.0-77957868876OAI: oai:DiVA.org:kth-26984DiVA: diva2:373634
Note
QC 20101201Available from: 2010-12-01 Created: 2010-12-01 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Conversion of Wood and Non-wood Paper-grade Pulps to Dissolving-grade Pulps
Open this publication in new window or tab >>Conversion of Wood and Non-wood Paper-grade Pulps to Dissolving-grade Pulps
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Dissolving-grade pulps are commonly used for the production of cellulose derivatives and regenerated cellulose. To obtain products of high quality, these so-called "special" pulps must fulfill certain requirements, such as high cellulose content, low hemicellulose content, a uniform molecular weight distribution and high cellulose reactivity. Most, if not all, of the commercial dissolving pulps accomplish these demands to a certain extent. Nevertheless, achieving high cellulose accessibility as well as solvent and reagent reactivity is not an easy task due to the compact and complex structure presented by the cellulose.

In the first part of this work, three commercial monocomponent endoglucanases were investigated with the purpose of enhancing the cellulose accessibility and reactivity of a hardwood dissolving pulp. A monocomponent endoglucanase with a cellulose-binding domain (CBD) was shown to significantly improve the cellulose reactivity. The positive effect of this enzyme on dissolving-grade pulps was also observed on paper-grade pulps.

The main focus of the forest industry is the production of paper-grade pulps. Paper-grade pulps are mostly produced by the kraft process. In contrast, dissolving-grade pulps are produced by the sulfite and prehydrolysis kraft processes due to the high purity required for these pulps. The kraft process is known for being the most efficient process in terms of energy and chemical recovery, which makes the production costs of paper-grade pulps lower than those of sulfite dissolving-grade pulps. Besides, the production of dissolving pulps present, among others, higher capital and chemical costs than paper-grade pulps.

Therefore, the viability of converting paper-grade pulps into dissolving pulps is brought into a question. However, this task is not simple because paper-grade pulps contain a lower cellulose content and a higher hemicellulose content than dissolving pulps. They also present lower cellulose reactivity and an inhomogeneous molecular weight distribution. As a consequence, the second part of this work focused on the study of the feasibility of converting kraft pulps into dissolving pulps. Several sequences of treatments of hardwoods and non-wood pulps were investigated. The best sequence for each suitable pulp was developed, and the parameters involved were optimized. After several attempts, it was demonstrated that pulps from birch, eucalypt and sisal fulfill the requirements of a commercial dissolving pulp for the viscose process after being subjected to a sequence of treatments that included two commercial enzymes, a xylanase and a monocomponent endoglucanase, and alkali extraction steps.

 

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. 57 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2010:46
National Category
Wood Science
Identifiers
urn:nbn:se:kth:diva-26967 (URN)978-91-7415-777-2 (ISBN)
Public defence
2010-12-03, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC 20101201Available from: 2010-12-01 Created: 2010-11-30 Last updated: 2010-12-01Bibliographically approved

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