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 lˉ 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 lˉ 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.