Filing Date: 2005-06-30.-- Priority Data: EP 04015680.4 (2004-07-02)The invention provides polypeptides coding for new cellulases from rumen, particularly from rumen ecosystem. The invention also relates to functional fragments or functional derivatives thereof as well as to nucleic acids encoding the polypeptides of the invention, vectors and host cells containing said nucleic acids, a method for producing the polypeptides and the use of the polypeptides according to the present invention for various industrial purposes and medical treatments.