Protease-Treated and purified cellulase compositions and methods for reducing backstaining during enzymatic stonewashing

DETAILED DESCRIPTION OF THE INVENTION Denim that is stonewashed with a Trichoderma cellulase enzyme composition that has been subjected to a limited protease treatment and subsequent purification to remove the protease shows a dramatic reduction in the level of backstaining and a visible increase in the contrast between white and blue threads.
While the inventors do not wish to be held to any particular theory, one possible explanation for the apparently contradictory observations that, on the one hand protease is required in the washer (Clarkson et al) and that, on the other hand it need not be present (this invention), is that there are two separate and distinct mechanisms by which proteases may affect backstaining in a denim washing processes.
The first mechanism is that described by Clarkson et al, where the protease simply acts as a stain removing agent in the washer.
This mechanism is consistent with Clarkson's findings that proteases can remove redeposited dye even after it has stained the white denim in a prior cellulase treatment.
It is also consistent with the well known use of proteases as stain removers in detergent systems.
Not surprisingly, the dye-based stains created by cellulase proteins can be removed by one of the well known approaches for treating stains related to proteins: proteases.
Under this first mechanism, however, those skilled in the art would not expect proteases to be able to mitigate against backstaining in the washer if they are never put in the washer.
To explain the inventors' surprising finding that proteases seem to be able to do just that, the inventors suggest that there is a second mechanism that is more subtle and less obvious than the first.
In particular, the inventors believe that a limited-protease treatment changes the mode of action of cellulase enzymes causing them to make small, easily dispersed particles that do not backstain.
While it has been reported that proteases can render the cellobiohydrolase components present in the Trichoderma cellulase enzyme complex inactive against crystalline cellulose by cleaving off their natural cellulose binding domains, the inventors hypothesize that such a treatment may still leave the cellobiohydrolase enzymes capable of making small nicks in the cellulose which are not detectable on their own but, when used in combination with other components in the Trichoderma cellulase enzyme complex, i