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Front. Microbiol. | doi: 10.3389/fmicb.2018.03059

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

 Stephan Christel1*,  Malte Herold2,  Soeren Bellenberg3, Antoine Buetti-Dinh4, 5, Mohamed El Hajjami6,  Igor Pivkin4, 5,  Wolfgang Sand3, 7, 8,  Paul Wilmes2, Ansgar Poetsch6, 9,  Mario A. Vera10 and  Mark Dopson1
  • 1Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, Sweden
  • 2University of Luxembourg, Luxembourg
  • 3Universität Duisburg-Essen, Germany
  • 4Università della Svizzera italiana, Switzerland
  • 5Swiss Institute of Bioinformatics (SIB), Switzerland
  • 6Ruhr-Universität Bochum, Germany
  • 7Donghua University, China
  • 8Freiberg University of Mining and Technology, Germany
  • 9Plymouth University, United Kingdom
  • 10Department of Hydraulic and Environmental Engineering, Pontificia Universidad Católica de Chile, Chile

Bioleaching is an emerging technology, describing the microbially assisted dissolution of sulfidic ores that provides a more environmentally friendly alternative to many traditional metal extraction methods, 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 the world’s most abundant copper mineral chalcopyrite suffers from low dissolution rates, often attributed 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 low oxidation/reduction potential (ORP), but chemical redox control in bioleaching heaps is difficult and costly. As an alternative, selected weak iron-oxidizers could be employed that are incapable of scavenging exceedingly low concentrations of iron and therefore, raise the ORP just above the onset of bioleaching, but not high enough to allow for the occurrence of passivation. In this study, we report that microbial iron oxidation by Sulfobacillus thermosulfidooxidans meets these specifications. Chalcopyrite concentrate bioleaching experiments with S. thermosulfidooxidans as the sole iron oxidizer exhibited significantly lower redox potentials and higher release of copper compared to communities containing the strong iron oxidizer Leptospirillum ferriphilum. Transcriptomic response to single and co-culture of these two iron oxidizers was studied and revealed a greatly decreased number of mRNA transcripts ascribed to iron oxidation in S. thermosulfidooxidans when cultured in the presence of L. ferriphilum. This allowed for the identification of genes potentially responsible for S. thermosulfidooxidans’ weaker iron oxidation to be studied in the future, as well as underlined the need for mechanisms to control the microbial population in bioleaching heaps.

Keywords: Redox control, Microbial, Chalcopyrite, Iron oxidation, bioleaching, Sulfobacillus, Leptospirillum

Received: 30 Aug 2018; Accepted: 27 Nov 2018.

Edited by:

MASAHIRO ITO, Faculty of Life Sciences, Toyo University, Japan

Reviewed by:

Sabrina Hedrich, Federal Institute For Geosciences and Natural Resources, Germany
Satoshi Wakai, Kobe University, Japan  

Copyright: © 2018 Christel, Herold, Bellenberg, Buetti-Dinh, El Hajjami, Pivkin, Sand, Wilmes, Poetsch, Vera and Dopson. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Mr. Stephan Christel, Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, Kalmar, Sweden, mail@stephanchristel.de