Degradation of wood polysaccharides by fungal glycoside hydrolases

Abstract

The enzymatic degradation of wood polysaccharides such as cellulose and hemicellulose is an important process in nature. In addition, cellulases and hemicellulases can be used in industrial applications. Fuel ethanol can potentially be produced from wood by enzymatic hydrolysis of cellulose followed by yeast fermentation of the formed sugars.



In this thesis, fungal glycoside hydrolases, cellulases and hemicellulases were studied with the aim of increasing our knowledge of the mechanisms involved in the enzymatic hydrolysis of cellulose and lignocellulose. The focus was mainly on cellulases from the filamentous fungus Trichoderma reesei. However, lignocellulose also contains hemicellulose and studies of hemicellulases are included



In Paper I-IV the mechanisms involved in cellulose degradation were investigated. Features of enzymatic cellulose hydrolysis such as synergism, decreasing hydrolysis rate during hydrolysis and the effect of adding surfactants to the hydrolysis mixture were studied. The observed decrease in hydrolysis rate by T. reesei Cel7A could be explained by unproductive binding of enzymes to the substrate. Furthermore, an extension of the existing model explaining end-exo synergism is presented and discussed. The use of surfactant to increase efficiency of the enzymatic cellulose hydrolysis is evaluated and a mechanism explaining the effect of surfactant is discussed. In addition, the major components of the cellulase system from the filamentous fungus Penicillium brasilianum was purified and characterised.



This thesis elucidates the need to use complex polysaccharide substrate in order to understand the mechanisms of degradation of natural complex substrates. O-acetyl-galactoglucomannan, the major softwood hemicellulose, isolated from spruce wood was used to study enzyme specificity and other biochemical properties (Paper V). Moreover, the function of the carbohydrate-binding module of the T. reesei b-mannanase Man5A was investigated (Paper VI). It was concluded that the carbohydrate-binding module of Man5A bound to cellulose but had an important function in potentiate the mannan hydrolysis of substrates containing both mannan and cellulose.



The majority of fungal glycoside hydrolases are glycoproteins. In Paper VII the N- glycosylation of T. reesei Cel7B was investigated using mass-spectrometry. N-glycosylation sites on the catalytic module were identified and it was shown that large parts of the observed heterogeneity of the enzyme preparation was caused by heterogeneity in N-glycan structures.

• author: Eriksson, Torny
• supervisor: [unknown] [unknown]
• opponent: Prof Tenkanen, Maija, Dept of Applied Chemistry and Microbiology, University of Helsinki, Helsinki, Finland
• organization: Biochemistry and Structural Biology
• publishing date: 2003
• type: Thesis
• publication status: published
• subject: Biological Sciences
• keywords: Penicillium brasilianum, ethanol, cellulose, wood polysaccharides, Man5A hemicellulase, cellulase, endoglucanase, cellobiohydrolase, Cel7B, Cel7A, Trichoderma reesei, glycoside hydrolase, Plant biochemistry, Växtbiokemi
• pages: 168 pages
• defense location: Kemicentrum hörsal A, Sölvegatan 39, Lund
• defense date: 2003-04-11 10:15:00
• ISBN: 91-7422-018-7
• language: English
• LU publication?: yes
• additional info: Article: I. A Model Explaining Declining Rate in Hydrolysis of Lignocellulose Substrates with Cellobiohydrolase I (Cel7A) and Endoglucanase I (Cel7B) of Trichoderma reeseiTorny Eriksson, Johan Karlsson and Folke TjerneldApplied Biochemistry and Biotechnology (2002) Article: II. Mechanism of Surfactant Effect in Enzymatic Hydrolysis of LignocelluloseTorny Eriksson, Johan Börjesson and Folke TjerneldEnzyme and Microbial Technology (2002) Article: III. The effect of Tween 20 on simultaneous saccharification and fermentation (SSF) of Softwood to EthanolMalek Alkasrawi, Torny Eriksson, Johan Börejsson, Anders Wingren, Mats Galbe, Folke Tjerneld and Guido ZacchiSubmitted to Enzyme and Microbial Technology (2002) Article: IV. Purification and characterization of five cellulases and one xylanase from Penicillium brasilianum IBT 20888Henning Jørgensen, Torny Eriksson, Johan Börjesson, Folke Tjerneld, Lisbeth OlssonSubmitted to Enzyme and Microbial Technology (2002) Article: V. Degradation of glucomannan and O-acetyl-galactoglucomannan by mannoside- and glucoside-hydrolasesJon Lundqvist, Per Hägglund, Torny Eriksson, Per Persson, Dominik Stoll,Matti Siika-aho, Lo Gorton and Henrik StålbrandManuscript Article: VI. A cellulose-binding module of the Trichoderma reesei b-mannanase Man5A increases the mannan-hydrolysis of complex substratesPer Hägglund, Torny Eriksson, Anna Collén, Wim Nerinckx, Marc Claeyssens and Henrik StålbrandJournal of Biotehnology (2002) Article: VII. N-Glycosylation of homologously expressed Trichoderma reesei Cel7B catalytic moduleTorny Eriksson Ingeborg Stals, Anna Collen, Folke Tjerneld, Marc Claeyssens, Henrik Stålbrand and Harry BrumerManuscript
• id: a42f4c58-3e50-41b9-87ac-a3c37465f8bc (old id 465563)
• date added to LUP: 2016-04-04 11:06:33
• date last changed: 2018-11-21 21:02:42