Tesis doctoral de Gloria Andreu Terren
The present thesis has been performed in the research group cipagraf (grup de recerca paperer i grí fic) of the departament d¿enginyeria téxtil i paperera at the escola técnica superior d¿enginyeries industrial i aeroní utica de terrassa. One of the research topics of the group is the application of enzymes in pulp biobleaching processes and in the modification of cellulosic fibers. the implementation of enzymatic stages in paper pulp bleaching sequences is, at present, one of the main challenges of the research in the paper industry. The application of laccase-mediator systems can lead to a reduction of environmental impact and to cost optimization, as well as to the development of paper-derived products with novel and improved properties. The use of a renewable raw material -kenaf- is in accordance with the growing interest in the utilization of non-wood fibers for the production of new high-added value lignocellulosic products. Consequently, the present thesis is based on the use of enzymes for kenaf pulp bleaching. the enzymatic bleaching sequences studied involve different treatments with the laccase-mediator system (stage l). The two fungal enzymes used in this stage- pycnoporus cinnabarinus and trametes villosa laccases-have been assisted by different natural mediators (lignin-derived phenolic compounds) and a synthetic one. The enzymatic stage has been completed with different chemical bleaching stages (chelating, hydrogen peroxide and pressurized hydrogen peroxide). At the end of the sequences, kenaf fibers with high cellulose levels and brightness were obtained. The significance of the chemical nature of the mediator has been emphasized because the different phenoxy radicals formed in the enzymatic stage determine the oxidative capacity of the laccase-mediator system. in addition, the results obtained also show the role of the chemical composition of kenaf lignin in the enzymatic process. The laccase oxidative capacity increases in the presence of kenaf pulp, and the amount of hexenuronic acids present limits the degree of brightness. Nevertheless, for the enzymatic treatments, the final results are similar to or better than for a conventional chlorine-free treatment. The application of xilanases after the laccase-mediator stage has been shown to be efficient in hexenuronic acids removal, opening possible new improvements to the treatments reported in this work.
Datos académicos de la tesis doctoral «Blanqueig enzimÁ tic de pasta de kenaf emprant sistemes lacasa-mediador«
- Título de la tesis: Blanqueig enzimÁ tic de pasta de kenaf emprant sistemes lacasa-mediador
- Autor: Gloria Andreu Terren
- Universidad: Politécnica de catalunya
- Fecha de lectura de la tesis: 15/04/2013
Dirección y tribunal
- Director de la tesis
- Teresa Vidal Llucia
- Tribunal
- Presidente del tribunal: José Francisco Colom pastor
- Francisco ignacio Javier Pastor blasco (vocal)
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- (vocal)