Uptake of reactive textile dyes by Aspergillus foetidus

An isolated fungus, Aspergillus foetidus was found to effectively decolorize media containing azo reactive dyes namely, Drimarene dyes. The extent of color removal was greater than 95% within 48 h of growth of the fungus. The entire color was found to be strongly bioadsorbed to the rapidly settling fungal biomass pellets without undergoing significant biotransformation. Our investigations reveal that the process of decolorization is concomitant with the exponential growth phase of the fungus and has requirement for a biodegradable substrate such as glucose. The fungus was also able to decolorize media containing mixture of dyes to an extent of 85% within 72 h of growth. Kinetic analyses of fungal decolorization indicate that the process is time dependent and follows first order kinetics with respect to initial concentration of dye. The rates of color uptake (k values) decrease to a significant extent with increasing initial concentrations of dye. The fungus was able to grow and decolorize media in the presence of 5 ppm of chromium and 1% sodium chloride. An alternate and cheaper carbon source such as starch supported the growth and decolorization process. These results suggest that dye uptake process mediated by A. foetidus has a potential for large-scale treatment of textile mill discharges.