After screening 14 strains exhibiting high xylanase activities, Penicillium canescens (CP1) and Penicillium janthinellum Biourge (CP2) strains were selected. The beta-xylanases produced had an optimum temperature and pH of 50 degrees C and 4.0, respectively. Using a bleaching sequence of D100EP, D80EP, and XD80EP, the effluent color obtained with XD80EP was lower for CP1 and CP2 than at the D-100 stage. The color was slightly higher at the XD80EP stage than with the D80EP sequence. In the final pulp obtained with XD80EP pretreatment, the viscosity increase and the Kappa number was similar to that of D100EP in the CP1 and CP2 strains. Brightness in the final pulp was slightly lower than that of control. The selectivity ratio was better for the CP1 and CP2 strains as compared to control. In the XD80EP stage using xylanase extract from CP1 with a pulp consistency of 8 to 15%, the Kappa number was not changed, but the viscosity, brightness, and selectivity ratio were improved proportional to the rise in consistency anc; delignification. Breaking length, burst and tear index, porosity, and elongation, in the final paper did not change after enzymatic treatment. AOX decreased (26%) in the D-80 stage effluent as compared with D-100, whereas in the XD80 stage diminished 42%. The enzymatic treatment with CP1 facilitates the lignin release, decreases the CL0(2) load by 20%, and reduces the AOX without any negative effects on the physical properties of the pulp and paper.