Utilisation of native microbes from a spent chalcocite test heap

A variety of acidophilic iron and/or sulphur-oxidising microbes capable of growth on several substrates (chalcopyrite, pyrite, ferrous ion, sulphur, glucose) in the range 30–60 °C were recovered from a spent chalcocite/chalcopyrite/pyrite heap. Several isolates exhibited tolerance to salt, up to 5 g/L NaCl, and to the metals nickel, cobalt, zinc and copper at up to 50 g/L.Leaching tests on chalcopyrite concentrate indicated higher copper yields when native isolates were employed, compared with the laboratory reference strains Acidithiobacillus ferrooxidans (DSM 583) and Sulfobacillus thermosulfidooxidans (DSM 9293). After 30 days, several native isolates had leached 20–30% more copper than the abiotic controls during experiments conducted at 45 °C. The results demonstrate that the native isolates are potential bioleaching candidates, adapted to diverse growth conditions.