BLEACHING OF HARDWOOD KRAFT PULP WITH MANGANESE PEROXIDASE SECRETED FROM PHANEROCHAETE SORDIDA YK-624

In vitro bleaching of an unbleached hardwood kraft pulp was performed with manganese peroxidase (MnP) from the fungus Phanerochaete sordida YK-624. When the kraft pulp was treated with partially purified MnP in the presence of MnSO4, Tween 80, and sodium malonate with continuous addition of H2O2 at 37 degrees C for 24 h, the pulp brightness increased by about 10 points and the kappa number decreased by about 6 points compared with untreated pulp. The pulp brightness was also increased by 43 points to 75.5% by multiple (six) treatments with MnP combined with alkaline extraction. Our results indicate that in vitro degradation of residual lignin in hardwood kraft pulp with MnP is possible.