Abstract

Metal pollution of the environment, especially at elevated concentrations, is known to adversely affect microbial activities. However, microorganisms are a versatile group, as they can adapt and grow under various extreme conditions including high metal concentrations. In the present study, fungal strains isolated from the oxidation pond of the University of Nigeria, Nsukka sewage treatment plant were evaluated for their tolerance for different concentrations of metal salts, namely, Cu, Zn and Mn. The fungi isolated and tested belonged to the genera Aspergillus, Penicillium and Cladosporium. The results revealed that metal tolerance by the isolates was highest for Zn, followed by Mn and then Cu and the isolates tolerated up to 1500 µg/ml of the salt. Tolerance for the metal ions was concentration as well as time dependent and also on the isolate tested. Aspergillus niger and Aspergillus fumigatus were the most tolerant of the metals and exhibited good growth at all metal salt concentrations tested. These fungal isolates showed a high level of tolerance for the metals tested, which makes them attractive potential candidates for further investigations regarding their ability to remove metals from contaminated wastewaters.

Key words: Metal tolerance, biomass, bioremediation, waste water, fungi.