A microbial factory for bio-indigo synthesis: demonstration of sustainable denim dying

Abstract

Biotechnological production using genetically engineered bacteria has the potential to enable environmentally friendly manufacturing of indigo without toxic intermediates or by-products, as in the case of traditional chemical processes. The shikimate and tryptophan pathways of Escherichia coli were engineered to supply a high level of the key intermediate indole, which was then converted to indigo by a naphthalene dioxygenase. The final strain yielded up to 12 g L⁻¹ of indigo dye under optimised cultivation conditions. The indigo was then purified using a sustainable process and used for dying of cotton fibers.