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Researchers develop a greener alternative to ‘denim blue rivers’

Researchers at the University of California, Berkeley are striving to make the process of making blue jeans greener by engineering bacteria to produce the indigo dye responsible for jeans’ characteristic hue. John Dueber, a professor of bioengineering who co-led the research, recently published in the journal Nature Chemical Biology informs, “Indigo dying for denim is unfortunately a pretty dirty process.” The vast majority of jeans are dyed with synthetically produced indigo which is similar to the colour of the dye extracted from the Indigofera plant.

However, synthesising indigo dye requires a number of toxic chemicals, including formaldehyde, the dying process also follows suit. This creates a hydra headed monster which create enormous amount of pollution. In some parts of the world, ‘denim blue rivers’ contaminate and kill fish and affecting the health of the rivers/workers/residents. With production of over 40,000 tons of indigo each year, this is a major issue.

John and his team wanted to create an indigo that requires fewer chemicals to synthesise and doesn’t need to have as many chemicals added to it during the dying process. “In order to do that, we took inspiration from how plants actually naturally synthesise indigo,” he revealed. The team engineered a strain of E. coli bacteria to become a chemical factory and produce an indigo precursor. The precursor is stable and can be stored and used as and when needed.

Unlike traditional synthetic indigo, which requires chemical treatment to reduce and solubilise the indigo so it can crystalize in the cotton fibre, the E. coli-produced precursor only needs the addition of an enzyme. The final result is identical to traditional synthetic indigo dying, John disclosed. “We feel pretty confident that we could scale the process to larger volumes,” Dueber says. “But there’s always work to be done going from the lab scale to an industrial scale.”

Some eco-minded manufacturers are returning to natural indigo dye, which needs fewer chemicals but has not been used due to cost and scale constrains. In Tennessee, a company called Stony Creek Colors is encouraging farmers to grow indigo instead of tobacco, in hopes of a natural indigo revival.