Scientists Make Bacteria-Dyed Jeans

Oct. 15 -- There were stonewashed jeans, then acidwashed jeans. Now scientists have developed jeans colored by vats of active bacteria.

Bacteria have been adapted before to help create the indigo dye used to color jeans. But just as the plant-derived dyes carry a trace of red pigment, the bacteria-produced dye also contained some of the unfashionable red hue. Power and his colleagues recently found a way to tweak the organism Escherichia coli to eliminate the trace of red in its pigment, leaving a deep true blue.

"We created a natural ation process that produces exactly what the fashion industry describes as the indigo look," says Scott Power, a research fellow at Genencor International in Palo Alto, Calif.

The bacteria, itself, doesn't turn the dye blue. Instead it converts sugar (usually corn syrup) into a reddish amino acid called tryptophan. Genencor spliced a gene into the bacteria to eliminate the red tones and create a substance called indoxl, which spontaneously turns blue when exposed to air. They call the color "bioindigo."

"It's a lot like producing beer," said Power.

A 'Green' Way to Make Indigo

The research was done using funding from Levi Strauss, and Genencor produced 400,000 square yards of bacteria-dyed jean material. But Levi Strauss indicates they won't be buying bioindigo jeans any time soon.

"Most indigo is now manufactured in China where environmental regulations aren't as steep," explains Jack Huttner, vice president for corporate communications and public affairs at Genencor. "Our process is cost effective, but it's not cost competitive to materials coming from China."

Indigo, the deep blue dye most commonly applied to jeans, was first derived from plants such as woad and dyer's knotweed. Levi Strauss used the dye in the 19th century in his tear-free clothes designed for farmers and gold miners. By the early 1900s, manufacturers began using a chemical process that drew dye from coal or oil, but that process can cause environmental damage.