The effect of limited proteolysis (digestion) of a commercial cellulase preparation (Ecostone((R)) L350) on backstaining with indigo was investigated. The influence of protease (papain) concentration on limited proteolysis of cellulase preparation was studied, applying different ratios of papain/cellulase (w/w). Changes in adsorption on Avicel cellulose of the non-digested compared with the papain-digested Ecostone((R)) L350 were examined using the Langmuir adsorption isotherm. The non-digested Ecostone((R)) L350 exhibited stronger interaction to Avicel cellulose compared with the digested form, while the maximum efficiency of cellulase adsorption to Avicel cellulose decreased after digestion. When papain-digested Ecostone((R)) L350 was applied on cotton fabrics during the dyeing procedure with indigo, a reduction of indigo backstaining was obtained compared with the non-digested Ecostone((R)) L350. (C) 2004 Society of Chemical Industry.