Biodegradation of dimethyl yellow by a locally isolated fungus from dye contaminated wastewater

Abstract

Fungal processes for the treatment of dye contaminated wastewater have the advantage of being cost-effective, environmentally friendly, and producing less sludge. This research was therefore aimed at isolating and characterizing fungus capable of decolourizing and utilizing azo dye (dimethyl yellow) as a sole carbon source using one-factor-at-a-time. Pour plating method was used to isolate the fungus on mineral salt media (MSM) following serial dilution. The isolate was then morphologically and molecularly identified as Aspergillus quadrilineatus strain BUK_BCH_BTE1 with the accession number OK178927 based on ITS1 and ITS2 rRNA gene sequence and molecular phylogenetic analysis. Characterization was conducted by studying the effect of temperature, incubation time, substrate concentration, pH, inoculum size and effect of heavy metals. The decolourization and growth of dimethyl yellow by the isolated Aspergillus quadrilineatus was optimal at substrate concentration of 200 μɡ/mL, temperature of 30 °C, 100–200 μL inoculum size, pH 5.0, and 72-h incubation time. The isolate was found to tolerate up to 4 ppm of Hg, Cu and Zn, with maximum inhibition shown by Cr and Ar. LC/MS analyses of the intermediate compounds produced during decolourization of dimethyl yellow suggested that in the fungal biodegradation of dimethyl yellow detected the formation of dimethyl yellow, 2,6-dichloro-p-benzoquinone, 1,2,3,5-tetrafluoro-4-nitrobenzene, and 3,4-dinitrobenzoic acid as metabolites. The finding from this study suggested that the isolate is a suitable candidate in bioremediation of coloured effluents particularly containing these compounds.

Keywords

• Metabolites
• Dyes
• Biodegradation
• Fungi
• Decolourization
• Industrial wastewater