Pulp bleaching using laccase from Trametes versicolor under high temperature and alkaline conditions.

Kraft pulp was delignified using laccase produced by the white rot fungus Trametes versicolor immobilized in solid support under specific conditions. The stability tests showed that this enzyme was stable for 6 h at 55 degrees C and pH 8.0, allowing its use under pH and temperature conditions very close to those used in industrial bleaching. In this work, unbleached hardwood Kraft pulp was submitted to prebleaching using 2 U laccase/g pulp basis. Reaction time, temperature, and pH of the enzymatic treatment were investigated. Good results regarding Kappa number reduction, selectivities, and high viscosities were obtained when prebleaching was performed for 1 h at temperature of 55 degrees C and pH 8.0 followed by alkaline extraction and ECF bleaching sequences.