Melissa K. Corbett

Saline-water bioleaching of chalcopyrite with thermophilic, iron(II)- and sulfur-oxidizing microorganisms

The application of thermoacidophiles for chalcopyrite (CuFeS2) bioleaching in hot, acidic, saline solution was investigated as a possible process route for rapid Cu extraction. The study comprised a discussion of protective mechanisms employed for the survival and/or adaptation of thermoacidophiles to osmotic stress, a compilation of chloride tolerances for three genera of thermoacidophiles applied in bioleaching and an experimental study of the activities of three species in a saline bioleaching system. The data showed that the oxidation rates of iron(II) and reduced inorganic sulfur compounds (tetrathionate) were reduced in the presence of chloride levels well below chloride concentrations in seawater, limiting the applicability of these microorganisms in the bioleaching of CuFeS2 in saline water.

Draft Genome Sequence of the Iron-Oxidizing, Acidophilic, and Halotolerant “Thiobacillus prosperus” Type Strain DSM 5130

ABSTRACT “Thiobacillus prosperus” is a halotolerant mesophilic acidophile that gains energy through iron and sulfur oxidation. Its physiology is poorly understood. Here, we describe the principal genomic features of the type strain of T. prosperus, DSM 5130. This is the first public genome sequence of an acidophilic halotolerant bacterium.

Draft Genome Sequence of the Iron-Oxidizing Acidophile Leptospirillum ferriphilum Type Strain DSM 14647

ABSTRACT The genomic features of the Leptospirillum ferriphilum type strain DSM 14647 are described here. An analysis of the predicted genes enriches our knowledge of the molecular basis of iron oxidation, improves our understanding of its role in industrial bioleaching, and suggests how it is adapted to live at extremely low pH.

Complete genome sequence of Acidihalobacter prosperus strain F5, an extremely acidophilic, iron- and sulfur-oxidizing halophile with potential industrial applicability in saline water bioleaching of chalcopyrite

Successful process development for the bioleaching of mineral ores, particularly the refractory copper sulfide ore chalcopyrite, remains a challenge in regions where freshwater is scarce and source water contains high concentrations of chloride ion. In this study, a pure isolate of Acidihalobacter prosperus strain F5 was characterized for its ability to leach base metals from sulfide ores (pyrite, chalcopyrite and pentlandite) at increasing chloride ion concentrations. F5 successfully released base metals from ores including pyrite and pentlandite at up to 30gL-1 chloride ion and chalcopyrite up to 18gL-1 chloride ion. In order to understand the genetic mechanisms of tolerance to high acid, saline and heavy metal stress the genome of F5 was sequenced and analysed. As well as being the first strain of Ac. prosperus to be isolated from Australia it is also the first complete genome of the Ac. prosperus species to be sequenced. The F5 genome contains genes involved in the biosynthesis of compatible solutes and genes encoding monovalent cation/proton antiporters and heavy metal transporters which could explain its abilities to tolerate high salinity, acidity and heavy metal stress. Genome analysis also confirmed the presence of genes involved in copper tolerance. The study demonstrates the potential biotechnological applicability of Ac. prosperus strain F5 for saline water bioleaching of mineral ores.

Incorporation of indigenous microorganisms increases leaching rates of rare earth elements from western australian monazite

A large number of microbial species commonly called phosphate solubilizing microorganisms (PSMs) are efficient at converting insoluble phosphate to soluble forms to prevent phosphorus limitation. This study examined the impact that PSMs had on a sterile and non-sterile monazite source and determined that they could be applied for bioleaching purposes to recover rare earth elements (REEs). On sterile monazite, Penicillum sp. released a total REE concentration of 12.32 mg L-1 after incubation for 8 days, however, this doubled when inoculated on to non-sterile ore (23.7 mg L-1). Similar results were recorded with Enterobacter aerogenes, Pantoea agglomerans and Pseudomonas putida. Abiotic controls leached a total REE level of 0.65 mg L-1. Examination of the leachate by HPLC identified several low molecular weight organic acids that corresponded with decreases in the media pH. The presence of a native consortia from the monazite ore combined with a known PSMs was more effective at leaching REEs from the monazite matrix than a single isolates or by the native population alone.