lower phosphate concentration 5 mm rather than 20 mm but heterogeneity and low yield remain great problems indeed only one fermentation results in a 70 binding level typically it is much less less than 10 even at ph 6 8 this level of binding varies dramatically between different fermentation batches this hypothesis and a possible solution to the problem are then tested if negatively charged molecules are attaching non covalently to chondroitinase i thus decreasing its basicity it should be possible to remove these undesired molecules by using a strong high capacity anion exchange resin removal of the negatively charged molecules should then restore the basicity of the enzyme the enzyme could then be bound to a cation exchange resin and eluted therefrom in pure form at higher yields experiments demonstrate that this approach indeed provides a solution to the problem encountered with the isolation and purification of the recombinantly expressed chondroitinase i enzyme as is discussed below chondroitinase i is recombinantly expressed in two forms the enzyme is expressed with a signal peptide which is then cleaved to produce the mature enzyme the enzyme is also expressed without a signal peptide to produce directly the mature enzyme the two embodiments of this invention which will now be discussed are suitable for use in purifying either of these forms of the enzyme in the first embodiment of this invention the host cells which express the recombinant chondroitinase i enzyme are lysed by homogenization to release the enzyme into the supernatant the supernatant is then subjected to diafiltration to remove salts and other small molecules however this step only removes the free but not the bound form of the negatively charged molecules.