From among 419 wood-rotting fungi 10 were selected by the Poly R decolorization test, and their ability to bleach hardwood kraft pulp was assayed. Of the 10 selected, 6 fungi (i.e., Phanerochaete crassa WD1694 and F150; Pleurotus pulmonarius PSC-H, PSC-M, and PSC-T; and Pleurotus species A119) showed much higher bleaching ability than Phanerochaete chrysosporium BKMF1767 or Trametes vervicolor WD1670, both of which are well-known high ligninolytic fungi. P. crassa WD1694 had the highest bleaching ability among the selected strains, and it increased the pulp brightness from 28 to 54, with a corresponding decrease in kappa number from 16 to 6 after 10 days of cultivation and alkali extraction. MnP was a predominant ligninolytic enzyme of P. crassa WD1694 during the biobleaching.
