Effect of recombinant xylanase pretreatment on bleachability of wheat pulp.

Wheat straw pulp was pretreated with recombined xylanase that was produced from Tyichoderma reesei Rutc-30 through gene recombination for reducing environment pollution, and the optimum pretreatment conditions of wheat pulp with recombined xylanase were as follows: pH 6.0, temperature 50℃, pulp consistency 7 %, time 1h, enzyme dosage 5 μmol/(min·g). Comparing with original pulp and control pulp, the Kappa number of pulp treated at optimum pretreatment conditions decreased by 27.98 % and 18.71 %, respectively. The chlorine dosage could be decreased by 50 % after pretreatment following sodium hypochlorite bleaching compared with control pulp at close brightness (72.6 %, ISO). The crystallinity of cellulose slightly increased from 60.0 % to 63.5 % after recombinant xylanase pretreatment. The SEM images of pulp further explained why the chlorine dosage could be saved after recombinant xylanase pretreatment and reduced effluent pollution load.