Effect of different physico-chemical parameters for natural indigo production during fermentation of Indigofera plant biomass.

Natural indigo production from Indigofera plant biomass requires fermentation of biomass, oxidation of fermented broth, settling of oxidized product (indigo), filtration and recovery. In this study, we have investigated roles of physico-chemical parameters during fermentation with respect to product yield. The study showed that water-to-biomass ratio (1:10), fermentation duration (0, 6, 12, 18, 24 h), pH (6-7.5), dissolved oxygen concentration; DO (0.5-3 mg ml-1), oxidation reduction potential ORP (+50 to -300 mV) and temperature (25-40 °C) during fermentation, oxidation and dye recovery from the broth are directly or indirectly related to indigo yield. Biomass fermentation for 12 h at 40 °C incubation temperature yields the highest biogenic indigo (2.84 mg g-1) out of the different experimental conditions.