Highly cadmium tolerant fungi: their tolerance and removal potential

Background: Soil and effluent of lead and zinc industries contain high concentration of cadmium. The present study was conducted to isolate tolerant fungal strains from cadmium - polluted sites in Zanjan province, Iran. Methods: Cadmium tolerance and bioremediation capacity of seven isolates including Aspergilus versicolor, Aspergillus fumigatus, Paecilomyces sp.9, Paecilomyces sp.G, Terichoderma sp, Microsporum sp, Cladosporium sp were determined. Results: Minimum inhibitory concentration values among 1,000-4,000 mg l(-1) proved great ability of isolated strains to survive in cadmium polluted environments. The most tolerant fungi, Aspergilus versicolor, showed tolerance index of 0.8 in 100 mg l(-1) cadmium agar media. Fungal resistance against cadmium is depended directly on strain's biological function. A. versicolor was found to bioaccumulate over7 mg of cadmium per 1 g of mycelium, followed by 5.878, 5.243, and 5.075, 4.557 by Paecilomyces sp, Aspergilus fumigatus, Microsporum sp and Terichoderma sp, respectively. Conclusion: It can be noted that tolerance of the strains appears to be independent from bioaccumulation capacity. Finally, the results indicated that A. versicolor could be a prospective candidate for bioremediation processes.