Metal tolerance potential of filamentous fungi isolated from soils irrigated with untreated municipal effluent

Abstract

Considering the importance of filamentous fungi for bioremediation of wastewater and contaminated soils, this study was planned to investigate the metal tolerance potential of indigenous filamentous fungi. Nineteen fungal strains were isolated from soils irrigated with untreated municipal/industrial effluent using dilution technique and 10 prominent isolates were used for metal tolerance. The isolated fungal isolates were screened for metal tolerance index (MTI) at I mM cadmium (Cd), nickel (Ni) and copper (Cu) concentrations and for minimum inhibitory concentration (MIC) and metal tolerance by growing on potato dextrose agar plates amended with varying amounts of Cd, Cu and Ni. Seven out of 10 isolated fungi belonged to the genera Aspergillus and three belonged to Curvularia, Acrimonium and Pithyum. The results revealed that the order of tolerance of isolates for metals was Cd > Cu > Ni and Aspergillus sp. were more tolerant than other fungi. Tolerance ranged from 900 – 9218 mg L-1 for Cd, followed by 381 - 1780 mg L-1 for Cu and 293-1580 mg L-1for Ni. The isolated fungi exhibiting great tolerance to metals (Cd, Cu and Ni) can be used successfully for bioremediation of metals from contaminated soil and wastewaters.

Keywords

• Heavy metal contamination
• metal tolerance
• minimum inhibitory concentration
• tolerance index