Indigo dye, a natural organic compound with a distinctive blue colour obtained from Indigofera tinctoria plant, is a good alternative to the synthetic dyes that are toxic to humans and environment. It is economically important because it is largely used for dyeing cloths and also used as hair dye. Traditionally, indigo dye extraction process is time consuming, involving considerable human resources in the oxidation step to obtain good quality & quantity of dyes, which might result in occupational health hazards. To address this, an eco-friendly dye extraction process through the microbial fermentation of the indigo plant biomass in a specially designed cement tank was developed. After fermentation, the plant debris is removed and the fermented liquid is oxidized using specially designed mechanical agitator / propeller. The precipitated indigo settles down at the bottom of the tank, collected as slurry, filtered, boiled, and sun dried as indigo cake. This new method minimizes the time of extraction and augments the quantity & quality of dyes.
