In vitro bleaching of an unbleached hardwood kraft pulp was performed with manganese peroxidase from fungus Phanerochaete sordida strain YK-624. When the kraft pulp was treated with a partly purified MnP in the presence of MnSO 4 , Tween 80 and sodium malonate with continuous H 2 O 2 addition at 37ºC for 24 h, pulp brightness increased by about 15 points and the kappa number decreased by about 6 points in comparison with untreated pulp. When the pulp was treated without the additon of MnSO 4 , the pulp brightness increased by about 10 points in the presence of 2 mM oxalate, a good manganese chelator and reducing reagent, while the brightness did not significantly increase in the presence of 50 mM malonate. To establish a totally chlorine-free bleaching process, oxygenbleached kraft pulp (OKP) was treated with four-stage bleaching process consisting of sequential MnP treatment, alkaline extraction, MnP treatment and hydrogen peroxide treatment stage. Full bleached kraft pulp (brightness 91%, yield 97%) could be obtained from OKP by the combination of enzyme treatment and hydrogen peroxide bleaching. To improve in vitro bleaching of the kraft pulp with MnP, the characterization of various MnPs from some white-rot fungi was examined. MnP from Ganoderma sp. YK-505 was superior to MnPs from P. sordida YK-624 and P. chrysosporium in stabilities against high temperature and high concentration of H 2 O 2 . MnP from Ganoderma sp. YK-505 differed in pHactivity profile from other MnPs. These results suggest that MnP from Ganoderma sp. YK-505 has different structure from those other fungi, and may be useful for biotechnological applications and studies of the relationship between structure and function.The kraft process, at present the most common commercial chemical delignification method, produces a dark pulp because of the color of residual modified lignin residues.These residues are normally bleached or removed in multistage bleaching procedures using a combination of chlorination and alkaline-extraction stepes. The effluent from

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