Nickel Tolerance and Accumulation by Filamentous Fungi From Sludge of Metal Finishing Industry

Industrialization, urbanization and increased vehicular traffic have resulted in increased contamination of our environment by heavy metals. The long persistence of heavy metals in nature has in turn resulted in development of metal resistant microbial strains. These strains are minimizing heavy metals toxicity, either by metal complexation or precipitation and other mechanisms. Characterization of fungal diversity was done in contaminated soil of the Wazirpur industrial area throughout the year. In this area highly acidic hazardous solid waste produced high concentration of heavy metals (Ni, Cu, Cr, Fe, Mn). Nickel toxicity is a major environmental concern. Due to long persistence of this waste in the environment without any treatment, many fungal isolates from the surrounding environment settle on the upper surface of waste. Few of them are capable of growing in the toxic conditions. More than 20 strains were isolated, most of them belonging to species of Aspergillus, Penicillium, Fusarium and Mucor genera. Seasonal variation in fungal diversity was significant. Four filamentous fungal isolates were found to be resistant for nickel (II) and a strain of Papulaspora sepedonoides reported first time for bioremediation of Ni (II) in this investigation, which is absorbing 62.33 μmol Ni gr⁻¹. These fungal isolates showed a high level (100–10000 mg kg⁻¹) of resistance for Ni (II) salt and removing Ni (II) from solution. Metal uptake varied with fungi. The toxicity also was influenced by different factors like pH and composition of growth medium.

Keywords:

• Heavy metal resistance
• persistance
• complexation
• seasonal variation
• uptake and hazardous

Acknowledgments

We gratefully acknowledge the University Grant Commission, India for scholarship in Ph.D. and financial grant for this research work. My special thanks goes to Dr. S. Lal, ITCC, Dept. of Plant Pathology, IARI, Pusa, New Delhi, India for her cooperation in identification of fungi and useful discussion.