Pycnoporus cinnabarinus and Daedaleopsis flavida, the two white rot fungal strains were considered very useful in the bleaching of unbleached kraft pulp. The reduction of kappa number and improvement of brightness of kraft pulp was evaluated during the solid state and submerged fermentation. P. cinnabarinus responsible for reduction of kappa number from 10.0 (10 days) to 8.3 (15 days) and 7.4 (30 days) during solid stated fermentation (SSF) while the brightness of the pulp which was initially 34% improved up to 58% in 30 days of incubation. The viscosity values were primarily 30.5 was reduced to 28.4 in 15 days and 27.1 in 30 days of incubations. The laccase enzyme of P. cinnabarinus caused for improvement of brightness from 33-55% and reduction of kappa number 10.2 to 7.3 and viscosity 28.4 to 25.3. The laccase of D. flavida was responsible for increase in brightness from 35-59% while reduction of kappa number 10.2 to 6.8 and viscosity 28.4 to 24.5. The influence of Dupont showed the reduction in kappa number from 10.8 to 0.98 and the hemicelluloses content was reduced from 42.7 to 19.8 in the last concentration (30g/100 Kg of pulp). With novozyme the lignin content was reduced from 0.130 to 0.085% in the 25g/100 Kg concentration. The kappa number was 14.4 in control reduced to 12.2 in the last concentration. The viscosity was reduced from 15.8 to 10.2 in final concentration after 60 minutes of incubation time. The energy and wood costs were drastically reduced in biological procedures. 

Keywords: Biobleaching; Unbleached Kraft Pulp; White Rot Fungi; Kappa Number; Viscosity; Pycnoporus cinnabarinus; Daedaleopsis flavida.