| Summary: | The aim of this study is to investigate the potential of newly isolated strain <i>Leptospirillum</i> (<i>L.</i>) <i>ferriphilum</i> CC for bioleaching of pyrite and chalcopyrite in pure or mixed culture with other iron- and/or sulfur-oxidizing bacteria. In this paper, kinetics of ferrous iron (Fe<sup>2+</sup>) oxidation by newly isolated strain <i>Leptospirillum</i> (<i>L.</i>) <i>ferriphilum</i> CC was studied. The effect of initial Fe<sup>2+</sup> in the concentration range of 50–400 mM on bacterial growth and iron oxidation was studied. It was shown that microbial Fe<sup>2+</sup> oxidation was competitively inhibited by Fe<sup>3+</sup>. The influence of copper, zinc, nickel and cobalt ions on the oxidation of Fe<sup>2+</sup> by <i>L. ferriphilum</i> CC was also studied. Minimal inhibitory concentrations (MIC) for each metal ion were determined. The toxicity of the ions was found to be as follows: Co > Zn > Ni > Cu. The comparison of iron oxidation kinetic parameters of <i>L. ferriphilum CC</i> with other strains of <i>L. ferriphilum</i> indicates the high potential of strain <i>L. ferriphilum </i>CC for biogenic regeneration of concentrated ferric iron (Fe<sup>3+</sup>) in bioleaching processes of ores and ore concentrates. Bioleaching tests indicated that the newly isolated <i>L. ferriphilum</i> CC can be a prospective strain for the bioleaching of sulfide minerals in pure culture or in association with other iron- and/or sulfur-oxidizing bacteria.
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