Synergistic and Antagonistic Effects on Metal Bioremediation with Increasing Metal Complexity in a Hexa-metal Environment by Aspergillus fumigatus

Abstract

In the present study, Aspergillus fumigatus (Genbank accession no. KX365202), was used for heavy metal removal in a hexa-metal system containing mixture of six heavy metals (Cu, Cr, Cd, Ni, Pb and Zn). The total concentration of the heavy metals was kept at 30 mg L−1. The experimental sets were designed based on the relative abundance of the heavy metals present in the wastewater of Delhi-NCR region. Toxicity of the heavy metals to the fungus varied with different metal combinations. Combination of Pb and Cr proved to be most toxic followed by that of Pb, Cr, Cu, Zn and Ni. Biomass production of 2.90 g L−1 was found in control whereas the combination Pb and Cr produced the lowest biomass (1.59 g L−1). In the presence of six metals, heavy metal removal pattern was Ni = Cd > Cu > Pb > Zn > Cr. SEM studies showed broken fungal hyphae in presence of hexa-metal stress. TEM–EDX studies showed that among the six heavy metals, Cu, Pb and Cd were adsorbed on the cell surface whereas Ni, Cr and Zn were accumulated inside as well outside of the cell. This system could be useful in treating water with multiple heavy metal contaminants.