Heavy metals resistance potential of some Aspergillus spp. isolated from Tannery wastewater

Abstract

Wastewater from three functional tanneries within sokoto  metropolis, Nigeria, was investigated to determine the  physicochemical properties as well as the distribution of fungal species in the untreated wastewater samples. Samples collected  were designated (a-c) representing three sampling points. The isolated fungal species were; Aspergillus niger, Aspergillus flavus, Aspergillus fumigatus, Aspergillus terreus, Aspergillus tamarii and Aspergillus oryzae. Of the fungal species, Aspergillus flavus was the most prevalent (17%) of the total count on the isolation plate, followed by Aspergillus niger (12%) and the least was Aspergillus oryzae. High levels of pH (9.6±1.7-9.9±1.2); electrical conductivity (4656 μs/cm ±886-5933μs/cm± 228); total dissolved solids (2024 mg/l±514-2934 mg/l±113) and nitrate (88.7 mg/l±2.2-94.7 mg/l±4.5) was observed in all the sampling points. The fungal species were screened for their ability to resist and grow in the presence of different concentrations of Pb (lead), Cr (chromium) and Cd (cadmium) in the laboratory. The result  revealed that the majority of the isolates were resistant to Pb and Cr, whereas to Cd, only a few were able to resist and grow. A. niger, A. flavus and A. terreus had the highest level of resistance and tolerance to all the heavy metals, with a strong growth often exceeding the control (PDB without test heavy metals). Therefore, it was concluded that these species of Aspergillus could be  performing an essential role in the mycoremediation of these  metals present in the tannery wastewater during their period of acclimatization through bioaccumulation.

Keywords: Aspergillus sp., Bioaccumulation, Mycoremediation, NESREA