Epsilon Open Archive

Abstract

Wood and wood fibre ultrastructure is of key importance for the pulp and paper making industry. In this thesis there has been a focus on development of methods for studying wood degrading enzymes. The methods have been used in different ways to render new information on wood and wood fibres. Wood degrading enzymes are chosen since they are tailor made to specifically degrade certain sub-structures in the wood bio-polymer, e.g. cellulose. In the first part an a-amino group of a carbohydrate binding module (CBM) from Phanerochaete chrysosporium cellulase Cel7D was covalently labelled with fluorescein isothiocyanate. The fluorescein labelled CBM showed specific binding only to cellulose and not to mannan and xylan. The labelled CBM was successfully used as a probe for detection of cellulose in lignocellulose material such as never dried spruce, birch wood and processed pulp fibres. Furthermore, the endoglucanase Cel5A from Trichoderma reesei and monocomponent endoglucanase from Aspergillus sp (Novozyme 476TM from Novozyme A/S) were evaluated as probes for the surface properties of soft- and hardwood chemical pulp fibres. The empirical kinetic degradation parameters correlated with the tensile index, relative bonded area and z-strength of paper. All paper properties showing a correlation with enzyme kinetic parameters were related to fibre-fibre interactions. Fluorescence labelling of the reducing end groups in pulp fibres was also used to further characterize the degradation. Finally, in vitro model studies as well as studies on intact wood samples were performed with different enzymes to characterize a fluorescent substance found in tori of water-sprinkled spruce logs. The model experiments showed that tannic acid can bind to pectin and that its presence inhibits pectinase action. Furthermore, it was shown that tannin acyl hydrolase can degrade tannic acid adsorbed to pectin. Neither pectinase nor tannase could, however, remove the discolouring substances from pit membranes in intact spruce samples. Manganese peroxidase had a minor but documented effect which, together with HCl/vanillin labelling experiments supported the conclusion that the discolouring substance corresponds to condensed tannin.