Gas chromatography/mass spectrometry study of enzymatic removal of sterols forming pitch deposits in TCF bleaching of eucalypt kraft pulp.

Abstract

In this work, the suitability of oxidative enzymes in efficiently removing free and conjugated (as esters and glycosides) sterols from Eucalyptus globulus pulp is revealed. The enzymatic treatment was applied as an additional stage of an industrial-type totally chlorine free (TCF) sequence (O-O-Q-PoP) for bleaching eucalypt kraft pulp. The pulp obtained after oxygen delignification was treated with a high-redox potential and thermostable fungal laccase from Pycnoporus cinnabarinus in the presence and absence of 1-hydroxybenzotriazole as a 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 lipophilic extractives in the pulps and the corresponding liquids was analyzed by gas chromatography and gas chromatography/mass spectrometry. Pulp and papermaking properties of the enzymatically-treated pulps were also evaluated.