Xylanase and beta-Xylosidase from Penicillium janczewskii: Production, Physico-chemical Properties, and Application of the Crude Extract to Pulp Biobleaching
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Extracellular xylanase and beta-xylosidase production by a Penicillium janczewskii strain were investigated in liquid cultures with xylan from oat spelts under different physical and chemical conditions. The selected conditions for optimized production of xylanase and beta-xylosidase were 7 days, pH 6.5, at 30 degrees C and 8 days, pH 5.0, at 25 degrees C, respectively. The xylanase exhibited optimal activity in pH 5.0 at 50 degrees C and the beta-xylosidase in pH 4.0 at 75 degrees C. The xylanase was more stable at pH 6.0 to 9.5, while the beta-xylosidase remained stable at pH ranging from 1.6 to 5.5. The xylanase half-life (T-50) at 40, 50, and 60 degrees C was 183, 15, and 3 min, respectively. beta-xylosidase half-life was 144, 8, and 4 min at 50, 65, and 75 degrees C, respectively. When applied to the biobleaching of Eucalyptus kraft pulp, xylanase dosages of 2 and 4 U/g dried pulp reduced, respectively, kappa number by 3.0 and 3.3 units after 1 h treatment, demonstrating that the use of P. janczewskii xylanases in this process is quite promising. The pulp viscosity was not altered, confirming the absence of cellulolytic enzymes in the fungal extract.