Characteristics of Metabolic Changes and Antioxidative Response in a Potential Zinc Tolerant Fungal Strain, Aspergillus terreus

Abstract

Heavy metal pollution is an alarming problem for the ecosystem. Zinc (Zn) is one of the most common heavy metal contaminant in the environment. In recent years different, abatement strategies are being implemented to control metal pollutants, amongst these, bioremediation has gained substantial focus. This paper detailed the Zn uptake and removal efficacies of a Zn tolerant fungal strain, Aspergillus terreus (minimum inhibitory concentration against Zn being 9100 ppm) which was capable of removing 75–35 % Zn from different Zn enriched media. However, the uptake and removal efficacies were found to be decreased with increasing Zn concentrations. FTIR spectra showed involvement of functional groups (present on outer surface of fungal cell wall) in Zn adsorption. Concurrently, Zn decreased the activities of two important metabolic enzymes, CMCase and α-amylase. Scanning electron micrographs clearly demonstrated the structural deformation of fungal hyphae due to Zn exposure. To combat the Zn stress A. terreus upregulated its antioxidative defense system, which is reflected through the significant upregulation of superoxide dismutase and catalase enzyme activities and metal responsive protein (metallothionein) with respect to control.