Modifying fibers in order to upgrade them to dissolving grade involves several changes. Paper grade pulps can be used to yield this kind of raw materials, if the necessary modifications are carried out. Classic processes are capable of producing these changes. However, these classic processes present many drawbacks. In this direction biotechnology, and particularly enzymes, are attracting an increasing interest due to the special features they present. Enzymes (glycosidases) are applied in this work on an alkaline TCF bleached sisal pulp. A xylanase and a cellulase preparation, both commercial, are applied on this pulp in order to evaluate their potential as catalysts for carrying out the previously stated upgrade. The main objective is to remove hemicelluloses present in starting pulp, which are an undesirable impurity in final product. Other modifications are as well profitable, such as increases in cellulose reactivity, a key parameter in dissolving pulps quality. After application, it is observed that final pulps present a lower content in hemicelluloses, a higher reactivity as well as other positive modifications