Development and Optimization of Biotechnology Use in the Manufacture of Bleached Chemical Pulps, 2005 Engineering, Pulping & Environmental Conference

Xylanases and laccases were tested for the production of ECF bleached hardwood kraft pulps. The pre-treatment with a new acid-tolerant xylanase from Scytalidium acidophilum (pH 3, 50°C) led to a gain in final brightness of 1.1 point and of 0.8 point after the SO2 washing, or to a reduction of 13% in chlorine dioxide charges obtaining brightness levels equal to the reference ones (also possible after pretreatment at 65°C). The kappa number could also be reduced in a high extent (up to 50%) after pretreatment with a xylanase, a laccase from Pycnoporus cinnabarinus (mediator : NHA or HOBT) and an alkaline extraction, with a cumulative effect of the X, Lm and E stages. Higher brightness levels (up to 2.2 %ISO) were obtained for XmE and XLmE pretreated pulps after an ECF bleaching, associated to a reduction in chlorine dioxide charges of respectively 26 and 50%. A lower viscosity was measured for the pretreated pulps (up to 35%), resulting exclusively in a loss in the final burst index values.