A ‘Green’ Way to Make Indigo
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.”