Beneficial Effects of Fungal Treatment before Pulping and Bleaching of Acacia mangium and Eucalyptus camaldulensis

Three white-rot fungi (Ceriporiopsis subvermispora (Pilát) Gilb. Ryvarden, Phanerochate chrysosporium Burds, andTrametes (Coriolus) versicolor (L.) Lloyd) were tested for their ability to modify/degrade lignin in cooking and bleaching. Both chipsand pulps of Acacia mangium Willd. and Eucalyptus camaldulensis Dehn. were pretreated with these white-rot fungi for differenttime periods (8, 12, and 16 days for chips; and 4, 8, and 12 days for pulps). For chip pretreatment, Kappa number decreased withthe increase of fungal treatment time, and the maximum reduction in Kappa number was 28% and 25% for acacia and eucalyptus,respectively, after 16 days of fungi inoculation. The variation in Kappa reduction was also found for different fungi species wheninoculated in the same wood species. Fungi treated pulps were also easy to delignify in oxygen delignification stage compared to thecontrol pulp without serious viscosity loss. In bleaching, the final brightness was higher in the case of FD0ED1 bleached pulps (asmuch as 8 ISO units) than OD0ED1 bleached pulps for both species. By FD0ED1 bleaching sequence, it was also possible to reach thefull brightness of pulp. Hand sheet properties were also improved significantly by fungi treatment prior to bleaching. Strengthproperties of hand sheets increased up to 20% by fungi treatment. Considering all the pulping and papermaking properties, theperformance of C. subvermispora was better compared to other fungi tested, and the response of fungi to eucalyptus was bettercompared to acacia.