A study of Acidithiobacillus ferrooxidans DSMZ 583 adaptation to heavy metals

In this study the ability of Acidithiobacillus ferrooxidans, with regard to the biorecovery of heavy metals in shake flask has been investigated. Adaptation experiments with the single metal ions Ni, Co, V, Mo, W and a mixture of the first four metal ions in the medium was developed through serial sub-culturing. Adaptation showed that A. ferrooxidans could tolerate up to 2.3 g/l Ni, 1.4 g/l Co, 1.4 g/l V, 0.045 g/l Mo and 0.005 g/l W, singly. In the presence of multi-metals considering a mixture of Ni-Co-V-Mo, the bacteria was able to tolerate up to 1.5 g/l Ni, 0.8 g/l Co, 0.8 g/l V and 0.05 g/l Mo in steps of 50-100 mg/l for Ni, Co and V, while for Mo and W with increments in concentration of 1-5 ppm, because of the high toxicity of these two metals to the bacteria. Adaptation of the bacterial strain was carried out in batch cultures by continually growing the bacteria in an environment containing increasing concentrations of the toxic metal such that a culture tolerant to the toxic metal proliferates. Effects of several variables such as pH, Eh, bacterial concentration in the solution as well as its resistance to heavy metals and ferrous and ferric iron concentration for the specific bacterial growth rate, were also investigated. This study showed that the various concentrations of Ni, Co and V had little effect on the oxidation of ferrous iron or the cell growth of A. ferrooxidans, whereas Mo and W ions were very inhibitory towards the Fe+2 oxidation ability of A. ferrooxidans.