Scientists Make Bacteria-Dyed Jeans
Oct. 15, 2002 -- 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.
Escherichia coli produces the dye with almost no environmental side effects and Power holds out hope that an increasingly environmentally conscious consumer might someday pay for the bacteria-dyed jeans in the future.
"When the playing fields become more level I think environmentally produced clothes will have a better chance," he says.
Bug-Designed
Bacteria already leave their mark in other parts of the jean-making process.
Most jean companies, including Levis and Wrangler no longer use stones to make their stonewashed jeans. Instead the material is washed with bacteria-made enzymes that soften and fade the material with the same effect. Environmentalists were happy to see traditional stonewashing take backseat to enzymes since the old method required lots of energy to operate the washers and drained pumice stone resources from mines.
Bacteria-made enzymes are also used when bleaching genes to faded hues. Rather than using water to flush out bleach from the jeans, manufacturers first introduce bleach-eating enzymes. The enzymes consume most of the bleach in the jeans so minimal amounts are leached into water drainage systems.