ABSTRACT
White-rot fungi and their enzymes are receiving increasing attention for
biotechnological applications in the pulp and paper industry as alternatives to
conventional bleaching. Laccase has been identified as one of the enzymes that plays
a major role in lignin degradation. Laccase only attacks phenolic subunits of lignin,
but its substrate range can be extended to non-phenolic subunits by the inclusion of a
mediator. The use of this enzyme was, therefore, not successful in pulp bleaching
trials until the discovery of mediators. Although the existence of natural mediators
has not been confirmed, various components have been identified that are able to act
as mediators. Improved methods of laccase production could benefit the industrial
utilisation of the enzyme. White-rot fungi constitutively produce low concentrations
of laccase, but higher concentrations can be obtained with the inclusion of inducers in
the cultivation media. The enzyme is mainly produced during the stationary growth
phase of the fungi, but various factors such as glucose, nitrogen and pH can influence
levels of laccase production. The enzyme does not only hold potential for biological
pulp bleaching operations, but also has application in bioremediation, the textile dye
industry as well as the food and beverage industries.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-02172004-154321 |
| Date | 23 March 2004 |
| Creators | van der Merwe, Johannes Jacobus |
| Contributors | DR J.F. WOLFAARDT, PROF J.C. DU PREEZ |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://lourie.uovs.ac.za//theses/available/etd-02172004-154321/restricted/ |
| Rights | mixed, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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