Blue jeans can also join the trend of ecological clothing production thanks to a new discovery.
The classic indigo blue color of this universal garment in ancient times was extracted from various species of plants such asIsatis tinctoria or Polygonum tinctorum and also of animal species such as the snailHexaplex trunculusUntil 1900, "natural indigo" was the sole source of the dye. However, synthetic indigo quickly completely replaced natural indigo, and today almost all indigo is produced via chemical synthesis.
Natural or synthetic, indigo crystals adhere to the surface of the fabric. Its intense blue is very resistant to washing, but at the same time the crystals wear out, giving that characteristic effect of used pants.
The various steps required in the chemical coloring process are harmful to the environment and could prove to be "unviable" in the future, according to the authors of the study published in the journal Nature Chemical Biology.
Today 95% of the 45,000 tons of synthetic indigo used each year are used to dye the 4,000 million "blue jean" garments manufactured annually, according to figures cited in the study. For example, chemicals such as formaldehyde and hydrogen cyanide are used in the process, as well as the fact that “many factories (…) dump the dyeing materials into rivers, with a negative ecological impact”.
That is why scientists are in search of more environmentally friendly alternatives. The option: an E.coli bacteria
The coloration could come from a bacteria
The researchers conceived an E.coli bacterium; that, like the plant, it manufactures indoxil and to which a sugar molecule is added; before adding an enzyme that allows to obtain the indigo to dye the fabric.
However, to produce the five grams of indigo needed to dye a single jean would require "several liters of bacteria at this stage," so his lab is working to improve the process.
"The end product is identical," said one of the authors, John Dueber of the University of California.
With information from: