Impact of xylanase pre-treatment on peroxide bleaching stage of biokraft pulp

Biokraft pulping of aspen has been investigated. Wood chips were treated with CZ-3 and FP 90031-sp strains of white-rot fungus Ceriporiopsis subvermispora for 2 weeks. Afterwards, bleachability of the pulps in peroxide stage was evaluated. Two commercial xylanase enzymes were used for bleaching. Xylanase pre-treatment of pulps increased their ISO brightness properties by approximately 10%. Biokraft pulps were beaten more easily in comparison to the control kraft pulps. Meanwhile, a significant difference due to the fungal or enzymatic pre-treatments was not found in tensile or bursting strength properties of pulps. A strength correlation was found between freeness and alkaline solubility (S18) for pulps at equal beating conditions.