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Closed Access item Enzymatic removal of free and conjugated sterols forming pitch deposits in environmentally sound bleaching of eucalypt paper pulp

Authors:Gutiérrez Suárez, Ana
Río Andrade, José Carlos del
Ibarra, David
Rencoret, Jorge
Romero Sánchez, Javier
Speranza, Mariela
Camarero, Susana
Martínez Hernández, María Jesús
Martínez Ferrer, Ángel Tomás
Keywords:Pitch, Sterols, Paper pulp, Laccases
Issue Date:2006
Publisher:American Chemical Society
Citation:Environmental Science & Technology 40:3416-3422 (2006)
Abstract:Free and conjugated sterols are among the main compounds responsible for pitch deposition in the manufacture of wood chemical pulps, making difficult the implementation of totally chlorine free bleaching (TCF) and closure of bleach plant circuits. In this work, the suitability of oxidative enzymes in efficiently removing sterols from eucalypt pulps is revealed. The enzymatic treatment was applied as an additional stage of an industrial-type TCF sequence for bleaching eucalypt kraft pulp. The pulp obtained after oxygen delignification was treated with a highredox potential and thermostable fungal laccase using 1-hydroxybenzotriazole as an enzyme mediator. This pulp was further submitted to chelation and peroxide stages and compared with a control TCF pulp obtained using chemical reagents. The composition of the lipophilic extractives in the pulps and the corresponding liquids after the different stages was analyzed by gas chromatography and gas chromatography-mass spectrometry. Free sitosterol and sitosterol esters and glucosides, the major lipophilic compounds in eucalypt pulps, were completely removed during the laccase-mediator treatment. Only some intermediate products from sitosterol oxidation remained after the laccase stage, as well as in the final pulp. Pulp brightness was also improved due to the simultaneous removal of lignin by the laccase-mediator treatment.
Description:Instituto de Recursos Naturales y Agrobiología, CSIC, PO Box 1052, E-41080, Seville, Spain; Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28040 Madrid, Spain; CIT, ENCE, Carretera de Campañó s/n, E-36157 Ribeiro Vao, Pontevedra, Spain
URI:http://hdl.handle.net/10261/39907
???metadata.dc.identifier.doi???:http://dx.doi.org/10.1021/es052547p
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