Biobleaching effects of crude xylanase from Streptomyces griseorubens LH-3 on eucalyptus kraft pulp

In this work, a xylanase-producing strain, Streptomyces griseorubens LH-3, was cultured, and the crude xylanase was prepared. Analysis of its enzymatic properties revealed that the crude xylanase possessed good thermal stability at temperatures below 60 oC, exhibited a wide pH range from 4.0 to 9.0, and was cellulase-free. This crude enzyme was used to treat eucalyptus kraft pulp, and the release of chromophores was the highest at the dosage of 20 IU g-1 dry pulp. Compared with the untreated group, biobleaching of eucalyptus kraft pulp with this enzyme increased the brightness of the pulp by 12.9% and reduced the Kappa number by 27.4%. Biobleaching of eucalyptus kraft pulp with this enzyme obtained the same final pulp brightness compared with that of the control; however, hydrogen peroxide consumption was reduced by 17% and the yield and viscosity of the pulp was increased by 1.47% and 1.53%, respectively. This crude xylanase has promising potential for industrial applications.