Enzymatic treatment of softwood kraft pulp at high and low consistency

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Title: Enzymatic treatment of softwood kraft pulp at high and low consistency
Author: Spönla, Elisa
Contributor: University of Helsinki, Faculty of Science
Publisher: Helsingin yliopisto
Date: 2020
URI: http://urn.fi/URN:NBN:fi:hulib-202008213810
Thesis level: master's thesis
Abstract: The aim of the thesis was to study enzymatic treatment as a way to modify paper grade pulp to be a suitable raw material for the future textile industry. Wood as a raw material is an environmentally friendly option for textile production but its sustainable exploitation is not easy. Currently, ionic liquids are assumed to enable a safe and sustainable process for the production of wood-based regenerated fibres. These processes commonly use dissolving pulp as their raw material but replacing dissolving pulp with a paper grade kraft pulp would decrease environmental impact and production expenses. In this work, molar mass distribution of softwood paper grade kraft pulp was selectively modified using enzymes. Enzymes were utilized instead of acids because of their favourable abilities to selectively modify targeted polymers and to increase fibre porosity. Enzymatic modifications of softwood kraft pulp were performed to decrease degree of polymerization of cellulose and lower the quantity of hemicellulose. Hydrolysis of cellulose was catalysed with endo-1,4-β-glucanase (endoglucanase) and hemicellulose was degraded using endo-1,4-β-mannanase and endo-1,4-β-xylanase. The treatments were carried out both at high (20%) and low (3%) pulp consistency to examine the synergistic effect of enzymatic and mechanical action arising in the high consistency treatment. Additionally, influence of different enzyme combinations on the pulp properties was studied. The modified pulp samples were characterized by determining intrinsic viscosity, molar mass distribution, yield loss, and its composition. The fibres were imaged with light microscopy. The degree of polymerization of the pulp cellulose was successfully decreased with a relatively small endoglucanase dose. The amount of hemicellulose was reduced by removing 11% of the total galactoglucomannan and 40% of the total arabinoglucuronoxylan. The high consistency treatments decreased intrinsic viscosity 1.9 times more on average than the low consistency treatments. The high consistency treatments were effective with low enzyme doses, easy to control, and reliably repeated. Therefore, enzymatic pulp treatment at high consistency seems to be a compatible way to modify paper grade kraft pulp to suitable raw material for textile production. Further studies related to pulp dissolution in ionic liquids, fibre spinning, and fibre regeneration should be concluded to confirm applicability of the modified fibres.
Subject: cellulose
enzymatic treatment
Discipline: none

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