Weak Iron Oxidation by Sulfobacillus thermosulfidooxidans Maintains a Favorable Redox Potential for Chalcopyrite Bioleaching

• Bioleaching is an emerging technology, describing the microbially assisted dissolution of sulfidicores that provides a more environmentally friendly alternative to many traditional metal extractionmethods, such as roasting or smelting. Industrial interest increases steadily and today, circa 15-20%of the world’s copper production can be traced back to this method. However, bioleaching of theworld’s most abundant copper mineral chalcopyrite suffers from low dissolution rates, oftenattributed to passivating layers, which need to be overcome to use this technology to its full potential.To prevent these passivating layers from forming, leaching needs to occur at a lowoxidation/reduction potential (ORP), but chemical redox control in bioleaching heaps is difficult andcostly. As an alternative, selected weak iron-oxidizers could be employed that are incapable ofscavenging exceedingly low concentrations of iron and therefore, raise the ORP just above the onsetof bioleaching, but not high enough to allow for the occurrence of passivation. In this study, wereport that microbial iron oxidation by Sulfobacillus thermosulfidooxidans meets these specifications.Chalcopyrite concentrate bioleaching experiments with S. thermosulfidooxidans as the sole ironoxidizer exhibited significantly lower redox potentials and higher release of copper compared tocommunities containing the strong iron oxidizer Leptospirillum ferriphilum. Transcriptomic responseto single and co-culture of these two iron oxidizers was studied and revealed a greatly decreasednumber of mRNA transcripts ascribed to iron oxidation in S. thermosulfidooxidans when cultured inthe presence of L. ferriphilum. This allowed for the identification of genes potentially responsible forS. thermosulfidooxidans’ weaker iron oxidation to be studied in the future, as well as underlined theneed for mechanisms to control the microbial population in bioleaching heaps

Subject headings

NATURVETENSKAP  -- Biologi -- Mikrobiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Microbiology (hsv//eng)

Keyword

redox control

microbial

bioleaching

chalcopyrite

iron oxidation

sulfobacillus

leptospirillum

Mikrobiologi

Microbiology

Publication and Content Type

ref (subject category)

art (subject category)