Xylanase pretreatment leads to enhanced soda pulping of wheat straw

Wheat straw was treated with a crude enzyme containing mainly xylanase prior to soda cooking. The enzyme was prepared from the culture filtration of Aspergillus niger strain An-76. The suitable conditions of pretreatment were xylanase dosage of 4 IU/g (on oven dry wheat straw), 48°C, 6–8 h, and pH 5.0, pretreated wheat straw was thorough washed after pretreatment. Xylanase pretreatment can improve pulpability of wheat straw effectively, and produce the pulps with lower kappa number (about 2 units lower), lower rejects and similar yields of screened-pulps under identical pulping conditions. The residual active alkali consistency of black liquor was increased by xylanase pretreatment. The brightness of bleached pulps from the xylanase pretreated wheat straw was about 3%ISO higher than that of the controls using identical bleaching sequence and conditions. The pulps, including unbleached pulps and bleached pulps, from the xylanase pretreated wheat straw had a higher tear index, a lower tensile index, and a lower burst index as compared to the control.