The aim of this work was to explore the possibility of using sulfate-reducing bacteria for the retrieval of valuable metals from a bioleaching solution. Tests were conducted to determine whether the bacteria produced hydrogen sulfide that could be used to precipitate valuable metals from a bioleaching solution as sulfides. The approach consisted of continuous culture of sulfate-reducing bacteria to produce hydrogen sulfide in the first reactor and the subsequent metal precipitation in the second reactor. Batch and continuous experiments were carried out to determine the optimum process parameters. The advantage of this process was demonstrated including faster precipitation of valuable metals and the possibility of the metal precipitation in the form of sulfides. A new flow sheet for the separation of Ni and Cu by biogenic sulfide precipitation in the presence of magnesium was proposed. (C) 2008 Elsevier Ltd. All rights reserved