Bioaccumulation of Fe3+ by bacteria isolated from soil and fermented foods for use in bioremediation processes

It is known that in areas where mining activity exist, a great ecological imbalance with accumulation of iron particles in the soil can occur, which in high concentrations damages cellular structures of plants and microorganisms. Bacteria resistant to high concentrations of iron with the ability to reduce Fe can make it bioavailable as an electron acceptor. The aim of this work was to select bacteria resistant to Fe and to evaluate the accumulation of this element in the bacterial biomass of selected strains. Of 183 isolates tested using three different iron concentrations (0.005, 0.5 and 1 g/L) in culture medium chemically defined, 12 bacterial strains showed better growth in 1 g/L of iron. The three best isolates (Bacillus simplex UFLA CESB127, B. subtilis UFLA SCF590 and Acetobacter tropicalis UFLA DR6.2) were selected for further experiments. The selection of physical factors was performed using the Plackett-Burman design in order to assess the effect of the parameters on the accumulation of iron, followed by a central composite rotational design. A pH valuev of 3.5 and iron concentration of 0.750 g/L presented the best conditions for the accumulation of iron by bacterial isolates. After the optimization step, the bioaccumulation of Fe was 99.22%. The validation confirmed the model of the experimental results. These results indicate the potential use of these isolates in the removal of iron, which in turn may be a promising alternative to conventional methods of treatment of contaminated soils.