Enzymes as Catalysts

Making faded jeans

Jeans made from denim were originally designed as hard wearing trousers for use by cowboys in the USA. They were traditionally dyed with the natural blue dye indigo. This dye, an example of a vat dye, is precipitated within the fibres of the cellulose material during the dyeing process.

Stonewashed jeans . . .

Denim jeans have now, however, become a world wide leisure and fashion item. Some people prefer their jeans to have a worn 'stonewash' appearance. This can be achieved by rotating the fabric in a drum along with some stones. Hence the name stonewash. The stones break some of the fibres and release the indigo dye. The jeans now look faded

. . . without the stones

An alternative way of fading jeans uses the catalytic ability of the enzyme cellulase. The dyed material is soaked in the enzyme solution. The enzyme catalyses the hydrolysis of the cellulose fibre and so leads to the breakdown of fibres on the surface of the fabric and the subsequent loss of the indigo dye they have encapsulated.

A model of indigo. Grey=carbon; white=hydrogen; red=oxygen; blue=nitrogen.

Washing powders

Many biological washing powders contain enzymes to help with the removal of stains. The enzyme may be a protease to break down protein stains or a lipase to break down fats and oils (lipids). The breakdown of protein and fat molecules is called hydrolysis. This simply means reaction with water. The enzymes catalyse these hydrolysis reactions and so help with the removal of stains.