Isolation and Characterization of Metallo-resistant Fungi and their Role in Removal of Heavy metals from Contaminated soil

Abstract

Heavy metals are non-degradable continuously introduced to the environment in industrial effluents due to its enonnous use in various industrial process. A number of physical and chemical approaches are used to minimize release of these toxic pollutants to the environment however these methods are associated with certain limitation. On the other hand biological treatment like biosorption and bioleaching are showing promising results and can be efficient alternative to the physico-chemical methods of remediation. In this study heavy metal resistant fungus was isolated from metal contaminated soil and its role as bioremediation tool was investigated in biromediation process such as biosorption and bioleaching. Soil samples were collected from metal contaminated sites in Misri Shah and Darogha Wala areas, located in Lahore City, and analysed for the presence of various heavy metals. The heavy metals copper (Cu), lead (Pb), nickel (Ni), cobalt (Co), cadmium (Cd) and mercury (Hg) were detected in both Misri Shah and Darogh Wala soil sample. Among these metals, Cu, Pb and Ni were found in highest concentration following by Co, Cd and Hg. A total of 13 different fungal strains were isolated from DW and MS soil sample by selective enrichment. FMSl, FMS2 and FDW6 were selected among all the strain on the basis of high resistance and organic acid production in the presence of Cd and Hg. Strain FMS2 showed highest tolerance limit to Cd (12000 ppm) and Hg (350 ppm), followed by FMSI (3000 ppm & 200 ppm) and FDW6 (2000 ppm & 100 ppm). FMSI produced maximum organic acid with acid unitage (4.83) and molar concentration (0.72 M) followed by FDW6 with acid unit age (4.0) and molar concentration (0.67 M). Optimum growth temperature and pH was found as 30°C and 5.0-6.0, respectively, for all the strains. The carbon source optimization was perfonned for the best organic acid producer strain FMS 1 glucose, sucrose, lactose, dextrose, fructose, maltose and xylose. Maximum organic acid was produced with sucrose as carbon source (0. 075M), which was lower than acid produced in Potato dextrose broth (0.81). HPLC analysis of the cuI tural filtrate of FMS 1 showed the presence of gluconic acid. FMS 1 and FMS2 were investigated for its potential role in bioleaching and biosorption of metal ions from metals contaminated soil.