Bioaccumulation of heavy metals on adapted Aspergillus foetidus
- PDF / 809,854 Bytes
- 10 Pages / 595.276 x 790.866 pts Page_size
- 19 Downloads / 259 Views
Bioaccumulation of heavy metals on adapted Aspergillus foetidus W. Ge · D. Zamri · H. Mineyama · M. Valix
Received: 13 May 2010 / Accepted: 15 March 2011 / Published online: 2 April 2011 © Springer Science+Business Media, LLC 2011
Abstract The development of the organisms extracellular and intracellular mechanisms for the uptake of heavy metals were conducted by using the natural detoxification strategies of the organism to toxicity. Aspergillus foetidus was used as a test case organism to examine these processes. Aspergillus foetidus was adapted to multi-metals (Al, Co, Cr, Cu, Fe, Mg, Mn, Ni and Zn) by a sequential method for tolerance development. The detoxification strategies of A. foetidus occurred by two mechanisms. The first mechanism is the production of extracellular metabolites that is capable of adsorbing and precipitating the metal ions on the cell surface. The second mechanism for the detoxification of metals is the intracellular binding of heavy metals to thiol containing compounds such as GSH and sequestering these metal– thiol complexes into sub-cellular compartments or vacuoles. These detoxification strategies resulted in adapted organisms with tolerance to multi-heavy metals concentrations and significantly higher metal uptake with adaptation. Keywords Bioaccumulation · Aspergillus foetidus · Multi-heavy metals · Adaptation · Intracellular and extracellular mechanisms
1 Introduction The capability of micro-organisms to sequester heavy metals from dilute waste water solutions has been a subject of extensive investigation (Akar and Tunali 2005; Schiewer and Volesky 2000; Volesky 1997). Organisms including bacteria, W. Ge · D. Zamri · H. Mineyama · M. Valix () School of Chemical and Biomolecular Engineering, The University of Sydney, Sydney NSW 2006, Australia e-mail: [email protected]
fungi, yeast and algae have been used to accumulate heavy metals by bioaccumulation in live cells and by biosorption in dead organism mycelia (Aksu and Karabayur 2008; Gonen and Aksu 2007; Naja et al. 2008; Volesky 2003, 2007). Bioaccumulation has the advantage of reduced unit processes including separate biomass cultivation, harvesting, drying, processing and storage (Aksu and Donmez 2005). The effectiveness of the micro-organisms in these processes, however is disadvantaged by the abiotic stress or toxicity of the pollutants that are being accumulated. Toxic metal ions form complexes with cellular membrane, which causes the loss of organisms integrity and impairs their function (Yilmazer and Saracoglu 2009). High concentrations of heavy metals are therefore deemed difficult or impossible to treat by bioaccumulation. Recent studies on the use of heavy metal tolerant organisms have had some success in efficient bioaccumulation of high concentrations of heavy metals. These have been developed by adaptation in laboratories (de Siloniz et al. 2002; Kocberber and Donmez 2007; Yilmazer and Saracoglu 2009), isolated from polluted environments (Kocberber and Donmez 2007) and by genetic engineering (Deng and Wils
Data Loading...
