Application of Xylanase- producing Alkalophilic Bacillius in Bleaching Reed Pulp

Reed is abundant and renewable, with a high content of cellulose and hemicellulose, it is a potential material for pulping and paper- making. To reduce the pollution of discharged effluent, some new techniques, such as biobleaching and biopulping have been developed in the paper- making process. Xylan is the major component of plant cell walls and the most abundant pentosan in nature. Xylan contains (- 1,4- linked D- xylose backbones with arabinose, 4- O- methyl- D- glucuronic acid, and acetic acid substituents. Xylanase is widely applied in the pulp and paper industry in recent year. Biobleaching with xylanase can increase the brightness of pulp and reduce the amount of the bleach boosting agent while it can improve the properties of paper. Biobleaching with xylanase is an environmental friendly bleaching technology. Xylanase that are optimally active and stable at alkaline pH and elevated temperature have tremendous potential for application in enzyme- assisted bleaching of kraft pulps and other biotechnological process. The use of thermostable alkaline xylanase for enzyme- assisted pulp bleaching could greatly reduce the need for pH and temperature readjustment, thus offering technical and economic advantages.As traditional pulp and paper processing were carried out under alkaline conditions, many emphases were put on alkali stability and alkaline xylanase. In our previous study, three strains of alkalophilic bacteria were selected based on the degumming of ramie fibers and the brightness of ramie fibers were determined.In the present investigation, the xylanase produced by alkalophilic Bacillus NT- 9 was utilized to pretreat of bleaching reed pulp, and the physics and chemical properties of the reed pulp were studied. The results showed that the weight loss rate of reed pulp increased with the enzyme dosage in the conditions for enzyme dosage 5～ 25 IU· g- 1, pH 8.6 and 50 ℃ for 120 min, and the brightness of reed pulp also increased to some degree. X- ray diffraction revealed that the relative degree of crystallinity of reed pulp fibers had 2.43% decrement due to the enzyme effect, and the scanning electron micrograph confirmed that the morphological changes of fiber surface were evident after xylanase pretreatment.