A commercial (Cartazyme) and non-commercial (Asperzyme) xylanases were studied. Cartazyme stability in a 0-70% (v/v) methanol at 50 degrees C and 65 degrees C was carried out. No deactivation was found for Cartazyme in the presence of 15% methanol at 50 degrees C. Half-life activity decay (t(1/2)) of Cartazyme at 50 degrees C in 30%, 50% and 70% methanol solutions were 4.0 h, 2.3 h and 1.2 h, respectively. At 65 degrees C, which is the ozone-alkali-peroxide (ZEP) bleaching temperature, only significant results on Kappa number reduction and selectivity were only observed in 15% methanol (t(1/2) 30 min) at the Z stage. For the Asperzyme, a t(1/2) of 36.5 min at 50 degrees C was found. In the Z stage with Asperzyme in the presence of 25% of methanol, a 20% Kappa number reduction and an improvement of the ZEP sequence of the brightness of 3.1 points were obtained. These results were correlated with the xylanase stability.