Cox, Simon Peter (1992) Iron oxidation and mineral oxidation by moderately thermophilic bacteria. PhD thesis, University of Warwick.

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Abstract

The microbial oxidation of minerals is a commercially important process. Until comparatively recently only one organism capable of mineral oxidation has been extensively studied - Thiobacillus ferrooxidans. Several new, potentially commercially important isolates were studied in comparison with T.ferrooxidans. This was done with regard to their iron and sulphur oxidation systems, which are vital to the process of mineral solubilisation, and their ability to solubilise the minerals pyrite or chalcopyrite. The study of the latter was undertaken with particular reference to mixed culture leaching.

The effect of growth substrate history on iron and sulphur oxidation varied between organisms. In particular, strain BC1 lost very little of its iron or sulphur oxidation capacity whether it was grown on either substrate. Conversely, the oxidation systems of T.ferrooxidans were directly influenced by growth substrate. SDS PAGE analysis and optical spectroscopy of T.ferrooxidans and strains BC1, LM2 and TH3 were used to investigate iron and sulphur oxidation systems and principally to indicate target components of these systems for further detailed study.

Further study of the iron oxidation system in strain BC1 showed that there was only one major chromophore, a membrane bound cytochrome aa_. This had absorption peaks at 443 nm, 560 nm and 604.5 nm. Spectra run at 77°K indicated a shoulder on the Soret peak at approximately 450 nm. Extensive investigation into the effect on the cytochrome aa_ of various detergents culminated in the solubilisation from the membrane of the terminal oxidase in an intact form. This allowed the mid-point redox potential of this cytochrome to be determined as +524 mV. The mid-point redox potentials of T.ferrooxidans cytochrome £ and fi. were determined as +317 mV and +497 mV respectively. SDS PAGE analysis indicated two proteins that could be involved in growth on ferrous iron, at 27 kD and 31 kD. One or both of these proteins appeared to contain very high levels of iron. High levels of iron were also found in fractions from column chromatography which contained cytochrome aa_.

Mineral oxidation studies showed that there was a slight increase in the rate of leaching of chalcopyrite in mixed cultures of strain BC1 and strain BC13 when compared to a pure culture of strain BC1, when the organisms where grown in shake flasks. In airlift reactor leaching of chalcopyrite the addition of strain BC13 to strain BC1 had several major effects. The pH in the mixed culture reactor was kept far more constant. Despite this, the leaching of copper from the mineral was not significantly altered in the mixed culture. However, a notable phenomenon in this mixed culture of strain BC1 and strain BC13 was the apparent reduction of the specific iron oxidation capacity of strain BC1 in comparison with its activity in pure culture.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QD Chemistry Q Science > QR Microbiology
Library of Congress Subject Headings (LCSH):	Thermophilic bacteria, Thiobacillus ferrooxidans, Iron -- Oxidation, Sulfur -- Oxidation, Pyrites, Chalcopyrite
Official Date:	1992
Dates:	Date Event 1992 UNSPECIFIED
Institution:	University of Warwick
Theses Department:	Department of Biological Sciences
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Norris, Paul R.
Sponsors:	Science and Engineering Research Council (Great Britain)
Extent:	xiii, 305 leaves : charts
Language:	eng

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