The use of proteases in the leather and wool industries

The leather industry consumes a significant proportion of the world's enzyme production. Alkaline proteases are used to remove hair from hides. This process is far safer and more pleasant than the traditional methods involving sodium sulfide. Relatively large amounts of enzyme are required (0.1-1.0 % (w/w)) and the process must be closely controlled to avoid reducing the quality of the leather. After dehairing, hides which are to be used for producing soft leather clothing and goods are bated, a process, often involving pancreatic enzymes, that increases their suppleness and improves the softness of their appearance.

Proteases have been used, in the past, to 'shrinkproof' wool. Wool fibres are covered in overlapping scales pointing towards the fibre tip. These give the fibres highly directional frictional properties, movement in the direction away from the tip being favoured relative to movement towards it. This propensity for movement solely in the one direction may lead to shrinkage and many methods have been used in attempts to eliminate the problem (e.g., chemical oxidation or coating the fibres in polymer). A successful method involved the partial hydrolysis of the scale tips with the protease papain. This method also gave the wool a silky lustre and added to its value. The method was abandoned some years ago, primarily for economic reasons. It is not unreasonable to expect its use to be re-established now that cheaper enzyme sources are available.