Xylanolytic rich filtrates were obtained by A. niger sp in both submerged and solid-state culture using rice husk or wheat bran as the only carbon source. Filtrates obtained on rice husk showed the highest activities (~6500 and 5200 U g−1, respectively). Independent of carbon source, these filtrates were very stable in an acidic pH range (4–7) and mild temperatures, with high half-life time values (more than 7 h at 50 °C) in the corresponding inactivation kinetic models. Also the effect of different metallic ions and denaturing substances was verified finding that these enzymes are not metaloproteins, and metals as Hg2+ and Pb2+ caused the greatest loss of xylanolytic activity (not higher than 30%). Xylanases produced by this A. niger strain showed important features that make them potential candidates for applications on human and livestock food industries.