A study published in Nature Chemical Biology reports an environmentally
friendly method of producing indigo dye from genetically engineered
bacteria. Indigo is widely used to give denim its characteristic blue color,
and this biological approach to its synthesis and application avoids the
need for harsh chemicals.

Indigo is made naturally by certain plants and has been extracted for use as
a blue dye for millennia. However, modern demand for the dye requires
chemical synthesis at a large industrial scale. This process uses multiple
hazardous chemicals, which can be harmful to the environment.

As a 'green' approach to making indigo, John Dueber and colleagues used
engineered bacteria that produce a related compound called indoxyl. Indoxyl
itself is unstable, but the researchers identified an enzyme that can
stabilize indoxyl by linking it to a sugar molecule. When added to bacteria,
this enzyme produces indican, which can be easily isolated and kept for
long-term storage. Later, at the time of dyeing, a different enzyme turns
indican into the familiar indigo directly on the cloth.

[www.natureasia.com]