Comparison of dye decolorization efficiencies of indigenous fungal isolates

Abstract

Different physicochemical cultural conditions were optimized for azo dye removal by using Acid Red 151 as a model dye, being of high consumer demand and usage during the present study. The three fungal strains having the dye removal abilities, Aspergillus niger SA1, Aspergillus flavus SA2 and Aspergillus terreus SA3 were selected and processed for different optimization studies in shake flask fermentations. Aspergillus nidulans minimal media proved to be most effective for utmost decolorization of AR 151 dye. The effect of inoculum size on dye decolorization efficiency of fungal strains showed that, best level decolorization was observed with 2% inoculum in all three fungal isolates. Effect of different concentration of Acid Red 151 dye ranging from 50 to 200 ppm on the selected fungal strains showed decolorization of AR 151 dye up to their maximal limits (200 ppm) to more than 60%. However, highest percentage of decolorization was shown by A. flavus SA2 (92.56%) with lower concentration of dye (50 ppm) and increase in concentration of dye showed a negative effect on decolorization percentage of all the tested fungal strains. There was significant decolorization (>60%) from all fungal strains with different pH ranging from 3 to 10. However, optimum pH for all the three fungal strains was found to be pH 7. There was an influence of temperature on decolorization as maximum decolorization was observed by all the three strains at 30°C (>85%) and it reduced with lower and higher temperatures. Maximum decolorization was observed at 0.5 - 1 M nitrogen concentration by all the three strains, where higher concentration had a negative effect. Similar results were observed for increase in concentration of carbon source as there was increasing trend of  decolorization efficiencies of all the fungal strains.

Key words: AR 151, decolorization, pH, temperature, indigenous fungus.