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Distribution and characterization of discolouring substances in Norway spruce (Picea abies L.Karst) pulp wood stored under water-sprinkling
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry.
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2006 (English)In: Holzforschung, ISSN 0018-3830, Vol. 60, no 1, 93-98 p.Article in journal (Refereed) Published
Abstract [en]

Discolouration of wood raw material during wet storage has a notable negative effect on the quality of the final product. In this study, fluorescence microscopy was used to investigate the spatial distribution of discolouring substances in water-sprinkled Norway spruce pulpwood. Water-sprinkled wood was characterised by the presence of discolouring substances on the pit membranes of wood cells. In vitro model studies on the interaction between a model bark substance (tannic acid) and torus constituents support the hypothesis that pectic structures facilitate the allocation of bark substances on pit membranes. Applied pectinase or tannase could not remove the discolouring substances from pit membranes. Manganese peroxidase had a minor but documented effect. The effect of manganese peroxidase, as well as HCl/vanillin labelling, indicated that the discolouring substance may be condensed tannins.

Place, publisher, year, edition, pages
2006. Vol. 60, no 1, 93-98 p.
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-93938DOI: 10.1515/HF.2006.016OAI: oai:DiVA.org:uu-93938DiVA: diva2:167587
Available from: 2006-01-12 Created: 2006-01-12 Last updated: 2013-07-24Bibliographically approved
In thesis
1. Biochemical Study and Technical Applications of Fungal Pectinase
Open this publication in new window or tab >>Biochemical Study and Technical Applications of Fungal Pectinase
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Pectinases are a group of enzymes produced by bacteria, fungi, higher plants and animals. Pectinases can modify and degrade pectins, a class of heterogeneous and multifunctional polysaccharides present in middle lamellae and primary cell walls of plants. Pectins have been showed to play diverse roles in cell physiology, growth, adhesion and separation. Pectinases are used technically in the processing of fiber production and fruit juice or wine making. We have studied the mechanisms and applications of pectinases, especially in retting, a microbiological process where bast fibers in flax and other bast fiber cultivars are released from each other and from the woody core.

A strong correlation was found between the ability to perform retting and the degradation of sparsely esterified pectin, a substrate of polygalacturonase. This led to the conclusion that polygalacturonase plays a key role in the enzymatic retting of flax. We purified and characterized an extracellular polygalacturonase produced by Rhizopus oryzae, a very potent retting organism. The purified enzyme which appeared to be the single active component in retting, has non-methylated polygalacturonan as its preferred substrate. Peptide sequences indicate that the enzyme, like another polygalacturonase (EC., belongs to glycosyl hydrolase family 28. It contains, however, an N-terminal sequence absent from other fungal pectinases, but present in an enzyme from the phytopathogenic bacterium, Ralstonia solanacearum.

Our finding that removal of calcium ions from the plant material by pre-incubation in dilute acid in enzymatic retting could reduce enzyme consumption by several orders of magnitude, improves the economical feasibility of the enzymatic retting process. Comparisons with different acids showed that the action was mainly pH dependent.

Pectinases were employed as analytical tools in a study of stored wood discoloration and, together with cellulases, in a mechanical process for making pulp from flax and hemp in paper production.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 47 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 137
Biochemistry, Pectin, pectinase, polygalacturonan, polygalacturonase, retting, flax, enzymatic retting, pre-incubation, discoloration, pulping, Biokemi
National Category
Biochemistry and Molecular Biology
urn:nbn:se:uu:diva-6295 (URN)91-554-6441-6 (ISBN)
Public defence
2006-02-03, Room B22, BMC, Husargatan 3, Uppsala, 10:30
Available from: 2006-01-12 Created: 2006-01-12Bibliographically approved

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Johansson, Gunnar
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