Adaptation of an iron oxidising culture to extremely high Fe concentration by a programmed fed-batch bioreactor

•Fed-batch operation has enabled a rapid starting-up of a Fe2+ biooxidation bioreactor.•Continuous operation was carried out with iron concentrations higher than 50 g·L−1.•pH values lower than 0.7 have been maintained in time without bacterial inhibition.•Adapted inoculum can be continuously generated to assist industrial bioreactors. Ferric iron plays a key role as a leaching agent. In ferric leaching, the generated ferrous iron can be biologically regenerated by biooxidation. In commercial applications, microbial growth usually limits operational conditions such as iron concentration and pH. Therefore, design and operation are often conditioned by strict restrictions of pulp density and need of addition of alkaline reagents. In the present work a mixed culture consisting mainly of Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans has been adapted to extremely high iron concentrations in comparison with the reported information in literature. For this purpose, a programmed fed-batch bioreactor has been used. A continuous stirred tank reactor was operated for testing the adapted culture. As a result, no biological inhibition was observed with iron concentrations up to 50 g·L−1 and pH of 0.7. By this methodology, an adapted inoculum can be continuously generated in order to assist industrial operations.