Fungal pretreatment of Eucalyptus wood can strongly decrease the amount of lipophilic extractives during chlorine free graft pulping

Modern environmentally sound trends in manufacturing of bleached paper pulp involve development of totally chlorine free (TCF) bleaching and zero liquid affluent (ZLE) processes. Lipophilic extractives are among the most problematic wood constituents for both TCF and ZLE processes, since they tend to accumulate in circuits resulting in new manufacturing ("pitch" deposits) and environmental troubles. The extractive-degrading fungi Bjerkandera adusta, Phlebia radiata, Pleurotus pulmonarius and Poria subvermispora were assayed to remove these compounds from Eucalyptus globulus wood using solid-state fermentation conditions. The pretreated chips were subjected to laboratory kraft pulping to assess the effectiveness of the treatment. Evaluation of extractive removal was carried out by gas chromatography-mass spectrometry of extracts from the pretreated wood and the pulps and black liquors after cooking. As a result of the fungal pretreatment, up to 75% decreased levels of problematic compounds (including free and esterified sitosterol) were found in pulps and liquors. Moreover, a significant reduction of potential acute toxicity was found in black liquors from wood pretreated with three of the fungi. The bio-pulps were TCF-bleached, refined and handsheet properties evaluated to select the most advantageous fungi from the point of view of their industrial applicability in environmentally sound pulp manufacturing processes.