Web Bit 5-1: Industrious Enzymes
By Richard Robinson
Enzymes, it has been said, make the impossible possible and the difficult easy. This is certainly true in the cell, where enzymes catalyze nearly every reaction necessary for life, and it is true in an increasing number of industries as well, where enzymes are used to accomplish tasks that were previously difficult, or even impossible. Industrial enzyme manufacture is now a multimillion-dollar business, and new applications are developed yearly.
Virtually every laundry detergent now contains enzymes. The most versatile ones contain amylases (for carbohydrates), lipases (for fats), proteases (for proteins), and cellulases (for cellulose). Amylases are also used to make sweet corn syrup from tasteless corn starch, while proteases and lipases convert insoluble meat byproducts into a tasty broth that improves the flavor of pet food kibble. Enzymes can sterilize medical equipment too sensitive for the autoclave, and can loosen the skin of a peach so it slips off in a chef's hands. Even the ancient and tradition-bound French wine industry has benefited from modern enzyme technology. Pre-treating wine corks with phenol oxidase prevents release of phenols in the wine, which otherwise can leach into the wine, causing off tastes and economic losses of millions of dollars each year.
In almost every case, the enzymes used are purified from bacterial cultures. While the genes for many of these enzymes originated in bacteria, others come from fungi or protists, and are transferred using recombinant DNA techniques. Most have been genetically engineered to increase production, stability, or ease of handling.
Cellulase is perhaps the single greatest success story in the world of industrial enzymes, and stone-washed jeans are its most important product. Most of us naturally assume that "stone-washed" means exactly what it says–that the denim is pummeled with stones as it goes through the wash. And this is precisely how it was done, from the introduction of stone-washed jeans in the early 1980s, up until about 1990. Stone washing has some severe drawbacks, however–the stones abrade the machines as well as the denim, some percent of each load of jeans is ruined by too much abrasion, and the worn pumice stones present a significant disposal problem.
Cellulase has none of these problems. Cotton is pure cellulose, and cellulase attacks cellulose, breaking it down, and thereby weakening the surface of the fabric in the same way that stoning does. Derived from the fungus Trichoderma reesei and cloned into bacteria, cellulase is now used to treat virtually every pair of "stone-washed" jeans sold in the world. Cellulases are currently used not only for "biostoning" but for creating other types of finishes as well, across a range of temperatures and pHs. With their ability to break down plant fibers, cellulases also have applications in waste processing. Since alcohols are their main product, cellulases have found some promising uses in the fledgling "biofuels" industry, in which corn and other agricultural products provide the raw materials for alcohol-based fuels.
So the next time you slip on a pair of jeans that are soft, comfortable, and slightly faded straight off the store shelf, don't think stones, no matter what the label says. Instead, remember those industrious enzymes. Not only are they catalyzing change in one industry after another–they also make for a pretty nice pair of jeans.