EFFECT OF LACCASE AND XYLANASE PRETREATMENT ON DELIGNIFICATION AND BLEACHABILITY OF WHEAT STRAW PULP

摘要

The purpose of biobleaching is to reduce bleaching chemical dosage in the bleaching process, to decrease environmental pollution and to improve pulp properties by means of pulp enzymatic pretreatment. The effects of wheat straw pulp pretreatment with laccase/xylanase system （ LXS ） and recombinant xylanase (X) respectively on bleachability of pulp were compared in this paper. The results were indicated as follows. The kappa number of pulps after pretreatment with laccase/xylanase system or recombinant xylanase decreased, but the kappa number of pulp pretreated with LXS decreased obviously. It decreased by 32.64% and 6.47% respectively compared with original pulp and X pretreated pulp. The available chlorine dosage could be decreased by 50% after LXS or X pretreatment following bleaching process compared with control pulp at close brightness. The crystallinity of cellulose increased slightly after LXS and X pretreatment. The SEM images and XPS analysis of two enzyme treated pulps further explained theoretically the delignification difference between LXS and X pretreatment.