dextranase is preferably clarified by centrifuging or other means and is then mixed with a suitable quantity of tannic acid the ph of the solution is adjusted in most cases to 3 3 5 with hcl and mixed by gentle stirring for a period of time determined experimentally for a given broth generally a period of 1 2 1 hour is sufficient after mixing is complete the tannic acid and dextranase have formed a complex which precipitates and settles the clear supernatant liquid is drawn off and the precipitate is further isolated by centrifuging or otherwise the isolated complex is in the form of a gel composed of tannic acid dextranase and water along with other impurities the separated precipitate is washed with acetone by dispersing it in a comparatively large volume of acetone which dissolves the tannic acid and leaves the solid partially purified dextranase behind the solid is then separated preferably by centrifuging for a higher degree of purity the acetone wash can be repeated once or twice of more if necessary the residue is air dried further purification may be accomplished by extracting dextranase with water or aqueous buffers the aqueous extracts after treatment with charcoal to remove colour if desired may be freeze dried to give a friable powder other.