Cadmium-induced oxidative stress tolerance in cadmium resistant Aspergillus foetidus: its possible role in cadmium bioremediation

•Cd-resistant Aspergillus foetidus isolated from wastewater.•Cd tolerance limit, uptake & antioxidative enzyme activities evaluated.•Test strain could grow & biosorb Cd at unusually high Cd doses.•Modulation of antioxidative enzymes to counteract high Cd toxicity.•A useful strain for bioremediation of Cd from aquatic systems.

Toxic effects of cadmium (Cd) were examined on a cadmium-resistant strain of Aspergillus foetidus isolated from wastewater. The Cd removal potential was analyzed. The results indicated that the strain could tolerate up to 25 mM and 63 mM Cd in liquid and solid Czapek-Dox media, respectively. It efficiently removed Cd from liquid growth media and industrial wastewater by mycelial biosorption. The strain produced oxalic acid for the purpose of Cd bioleaching as confirmed by the presence of cadmium oxalate crystals on the mycelial surface. Intracellular proline contents and the antioxidative enzyme activities increased up to a certain level to detoxify the overproduced free radicals. These data indicate that the strain has inherent mechanisms to grow in Cd contaminated environment, tolerate high Cd doses and high Cd uptake potential which are pre-requisite for acting as a suitable candidate for Cd bioremediation.