Enhancement of indigo dye yield from Indigofera plant biomass by using fungal elicitors during fermentation

摘要

Natural indigo dye from biogenic materials is an alternative to synthetic indigo that pollutes the environment. Indigo production from the Indigofera tinctoria plant is in practice since ancient time through biomass fermentation in water. Maximum indigo yield depends on complete release of indigo precursor indican from plant biomass during fermentation. In this study, we assessed the role of fungal elicitors on indigo dye yield during biomass fermentation using three strains namely; Aspergillus niger, Trichoderma reesei and Sclerotium rolfsii. Fungal extracts were prepared from fungal mycelia, raised separately on Potato DeXtrose agar medium and extracted in a buffer solution containing 1N HNO3 plus 1N NaOH. The extracts.were added to fermentation water in 1, 5 and 10% doses (v/v) separately during biomass fermentation keeping other parameters for fermentation and further processing for dye production fixed. Indigo yield with 10% A. niger extract was 1.56% (w/w), which was higher in comparison to control 0.45% (w/w). A. niger extract at 10% enhanced indigo yield up to 3.5 times compared to control, and 2.7 and 2.1 times, respectively to other two cultures [T. reesei (0.58% w/w) and S. rolfsii (0.93% w/w)] used at the same concentration.