Biochemical characterization of a lead-tolerant strain of Aspergillus foetidus: An implication of bioremediation of lead from liquid media

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The fungus Aspergillus foetidus isolated from wastewater treatment center, Kalyani was identified primarily as a lead (Pb+2) tolerant strain by supplementation experiments with high concentrations of Pb and confirmed the fungal strain as, A. foetidus MTCC 8876 after identification from the Microbial Type Culture Collection and Gene Bank (MTCC), Institute of Microbial Technology (IMTECH), Chandigarh, India. Growth studies in liquid Czapek-Dox (CD) media with different Pb treatments showed an initial growth increase up to 200 mg L−1 Pb treatment followed by gradual decrease at higher Pb doses. Protein and thiol leakage during growth experiments in CD broth containing Pb+2 may be due to disturbance in membrane structure as was further evident from lipid peroxidation induced by Pb. The strain was efficient in removing Pb from the liquid growth medium by mycelial biosorption. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopic (EDS) analysis confirmed the presence of tightly bound Pb as insoluble crystals outside fungal mycelia. Intracellular proline level and activities of the antioxidative enzymes increased up to a certain level to detoxify malondialdehyde and H2O2 produced by Pb toxicity. These data indicate that the test strain has some inherent mechanisms to tolerate unusually high Pb doses and high Pb uptake potential, pre-requisite for acting as a suitable candidate for Pb bioremediation from contaminated aqua-environment.