Abstract
Both essential and nonessential metals form the basis of biological activities. However, all metals induce toxicity at certain levels depending on the tolerance of organisms to these metals. Therefore, it is important to identify novel microbial strains that can tolerate increasing concentrations of heavy metals. Microorganisms including fungi, remove heavy metals from soil through bioaccumulation and biosorption in an eco-friendly and cost-effective manner.
In this study, we used fungi Aspergillus niger, A. flavus, Fusarium solani, and Penicillium notatum to remove heavy metals. Effects of 4 different concentrations (125, 250, 500, and 1000 mg/l) of MnCl2, AlCl3, HgCl2 and ZnSO4 on the radial growth of the 4 tested fungi were examined. Toxicity of the metals to A. niger was HgCl2 > ZnSO4 > MnCl2 > AlCl3, A. flavus was HgCl2 > ZnSO4 > MnCl2 > AlCl3, F. solani was HgCl2 > ZnSO4 > MnCl2 > AlCl3 and P. notatum was HgCl2 > ZnSO4 > MnCl2 > AlCl3. Both living (bioaccumulation) and non-living (biosorption, alkali treated) fungal biomass effectively removed heavy metals.
Our results showed that the living biomass of F. solani and P. notatum removed 2.2-62.1 mg.g(-1) of AlCl3 and HgCl2 respectively. Treatment with alkali biomass can significantly consolidate the heavy metal adsorption well described in this study. Maximum adsorption of HgCl2, ZnSO4, MnCl2 and AlCl3 by the alkali biomass of P. notatum was 45.2-72.1, 67.3-75, 36.1-66.1, and 29.1-54.7 mg.g(-1) respectively. Thus, our results suggested that A. niger, A. flavus, F. solani, and P. notatum can be used for removing high concentrations of heavy metals from contaminated soil and wastewater. In our study all four heavy metals HgCl2, ZnSO4, MnCl2 and AlCl3 showed a serious damage on DNA especially with high concentration of metal. Total of 3 primers were screened with treated and untreated fungi.