An Investigation on Tolerance and Biosorption Potential of Aspergillus awamori ZU JQ 965830.1 to Cu(II)

Abstract

HE MINIMUM inhibitory concentration (MIC) value of ……A.awamori for Cu(II) was 3100mg/l and a complete inhibition of biomass production was observed at 800mg/l concentration of Cu(II). Slight changes were observed by SEM investigation in Cu(II)-stressed biomass. Quantification of Cu(II) was performed by EDAX. Transmission electron microscopy investigation (TEM) confirmed the involvement of extracellular adsorption, intracellular penetration through the cell wall and vacuolation. Cu(II) stress induced noticeable changes in the activities of polyphenol oxidase(PPO), glutathione reductase (GR) and peroxidase (POD) and in the concentration of total antioxidant, soluble protein and thiol. High performance liquid chromatography analysis (HPLC) revealed that Cu(II) stress stimulated the production of oxalic acid .Maximum Cu(II) uptake capacity was achieved at pH 4.0, initial metal ion concentration 500mg/l and biomass dosage 1g/l. Maximum Cu(II) uptake capacities were reached after 180 min for live biomass and 30 min for dead biomass. Fourier transform infrared spectroscopy (FTIR) results gave an indicateion of chelation between oxygen-, nitrogen-, phosphorus-and especially sulphur-containing ligands of biomass with metal ions. X-ray diffraction analysis (XRD) revealed the presence of CuSO 4 .H 2 O in live and dead biomass. EDAX confirmed the occurrence of sulphur, oxygen and Cu(II) in the cell wall.Keywords: Aspergillus awamor;, Cu(II), Stress, Antioxidant enzymes, Biosorption.Several inorganic and organic compounds such as heavy metals, fuels and petroleum industry products cause soil and water contamination. For this reason, research focused toward better decontamination methods and the development of new technologies is imperative (Velásquez & Dussan, 2009).Remediation methods for heavy metals differ from those for organic compounds. As compared to organic compounds, metals are non-biodegradable (Gupta & Rastogi, 2008). Therefore, biomobilization is a valid concept in the management of metal pollution. Some metal ions, like Cu(II) and Zn(II) are essential for biological processes, but other nonessential metals like Cd(II) and Hg(II) are considered highly toxic elements to nearly all organisms even at low MANAL T. EL-SAYED Egypt. J. Microbiol. 48(2013) 24concentrations (Guelfi et al., 2003). However, Cu(II) is toxic to most organisms at elevated concentrations, largely through enzyme inhibition and oxidation of membrane components as a result of the ability of Cu(II) to generate toxic hydroxyl radicals (Melo et al., 2004). Membrane damage then leads to rapid leakage of ions and other low molecular weight compounds (Soares et al., 2003).Various techniques such as precipitation, coagulation, ion exchange, reverse osmosis, evaporation, filtration, electrochemical treatment and oxidation and reduction have been employed to remove toxic heavy metals from industrial wastewaters. Most of these techniques are ineffective or extremely expensive in terms of energy and reagent consumption, especially when concentrations of diss...