The effect of xylanase on the fine structure of a bleached kraft softwood pulp

Abstract In this paper, X 1 and X 2 (two different xylanases), were employed to pretreat oxygen-delignified kraft softwood pulp. X 2 could handle unwashed pulp, while X 1 needed washed pulp. Subsequently, the effects of two xylanases on the physical properties, microstructure and fiber characteristics of pulp were investigated. Compared to the ECF bleached pulp (OD 0 E p D 1 ), the brightness (86.9 %ISO), tensile index (28.4 N·m/g) and burst index (1.67 kPa·m 2 /g) of the ECF bleached pulp treated with X 2 xylanase (9 U/g) increased by 2.4 %ISO, 4.8 % and 24.6 %. After X 2 xylanase pretreatment, the fiber length of pulp decreased slightly, the content of fine fibers increased, and the water retention value increased. Due to the pretreatment of X 2 xylanase, some non-fibrous components and chromophores in the pulp were removed, and the intrinsic viscosity and average molecular weight of the pulp were reduced. The crystallinity of cellulose decreases by 1 %, the fiber surface becomes rough, and voids are created, the specific surface area increases, and the average pore size increases. These findings suggest that enzyme pretreatment is a green and highly effective approach that not only significantly enhances pulping performance but also demonstrates excellent adaptability to complex processing environments and it streamlines the traditional pulping process effectively.