The gene for the cellulase enzyme was first isolated from the fungus Trichoderma reesei and then put into bacteria for mass production. Cellulases digest cellulose - the main component of cotton and other natural plant fibers. [Cellulose is a long, glucose polymer used as structural support in plant cell walls. We can't digest cellulase, but organisms like fungi and some bacteria can!].

Cellulases bind to the exposed cellulose on the exterior of each cotton fiber and break some of the molecular bonds. The process can be stringently controlled so that only the dye particles are loosened from the denim surface while the interior of the cotton fibers are left intact.

In the early days, one problem with biostoning was "back staining." Back staining happens when loosened dye particles redeposit onto the back surface of the fabric, causing discoloration. A reddening of the dyes sometimes occurred too. But maintaining the pH of the wash load between 6-8 has successfully controlled both problems. Today, biostoning can achieve the same effect as traditional stone washing but without the damaging abrasion of the fabric and equipment.

Biostoning is by far the most economical and environmentally friendly way to treat denim. Waste, pollution, quality variability, and imperfections are all reduced. And unlike pumice or acid, which get used up during the wash, enzymes can be recycled. A small dose of enzymes can replace several dozen pounds of pumice stones. So productivity can be increased by 30-50% because the room formerly taken up by the pumice stones in the washing machines can now be filled with more jeans. And there is no need for the time-consuming and expensive task of removing stone fragments from the jeans once the wash is done. There is also no pumice dust to endanger employee health or gritty sediment to dog drains. Nearly all jeans made today are finished by biostoning.

Cellulases and other enzymes used in the textile industry are available in a number of different varieties, each with its own special properties. This added dimension gives fashion designers the flexibility to create a wider range of shades and finishing effects. By selectively modifying the surface of the denim without damaging the fabric integrity, designers have a more liberal pallet to create new fashions possibilities For example, colorful logos can be printed onto metal buttons or leather labels without the fear of them being abraded away by pumice. And intricate designer accents made of non-cellulose fibers such as nylon or polyester will remain vibrant even after cellulase treatment.

So next time you sit down in your favorite pair of jeans to enjoy reading some biology, just remember: Even though the label says stone washed, stones aren't really used at all. Instead, when you see "stone washed," think of those industrious little enzymes made possible through the wonders of modern biology.