Efficient bleaching of non-woody high-quality paper pulp using lacasse-mediator systems

aDepartment of Molecular Microbiology, CIB, Consejo Superior de Investigaciones Científicas (CSIC), Velázquez 144, E-28006 Madrid, Spain; bDepartment of Textile and Paper Engineering, ETSII, Polytechnic University of Catalunya (UPC), Colón 11, E-08222 Terrassa, Spain; cDepartment of Biogeochemistry, IRNAS, CSIC, PO Box 1052, E-41080, Seville, Spain; dCelulosas de Levante SA (CELESA), Ctra. C-237, km 4.5, E-43500 Tortosa, Spain

High-quality flax pulp was bleached in a totally-chlorine-free (TCF) sequence using a laccase-mediator system. Three fungal laccases (from Pycnoporus cinnabarinus, Trametes versicolor and Pleurotus eryngii) and two mediators, 2,2´-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) and 1-hydroxybenzotriazole (HBT), were compared. P. cinnabarinus and T. versicolor laccases in the presence of HBT gave the best results in terms of high brightness and low lignin content (kappa number). The former laccase also resulted in the best preservation of cellulose and the largest removal of residual lignin as revealed by analytical pyrolysis, and was selected for subsequent TCF bleaching. Up to 90% delignification and strong brightness increase were attained after a laccase-mediator treatment followed by H2O2 bleaching. This TCF sequence was further improved by applying H2O2 under pressurized O2. In this way, we obtained up to 82% ISO brightness (compared with 37% in the initial pulp, and 60% in the peroxide-bleached control) and very low kappa number (near 1). Good results were also found when the laccase-mediator treatment was performed in a bioreactor under pressurized oxygen. The pulp properties obtained, which could not be attained by conventional TCF bleaching of flax pulp, demonstrate the feasibility of enzymatic bleaching to substitute chlorine-containing reagents in manufacturing of these high-price paper pulps.

This study was supported by the European Commission (contract QLK3-99-590), the Spanish CICYT (FEDER project 2FD97-0896-C02, and projects AGL2002-00393, BIO2002-1166 and PPQ2000-1068-C02-02), the Comunidad de Madrid, and the CSIC network on “Bioremediation and Phytoremediation”.

Peer reviewed