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Effect of environmental conditions on the growth and activity of chemolithotrophic sulphur-oxidising bacteria

Candy, Rachel (2014) Effect of environmental conditions on the growth and activity of chemolithotrophic sulphur-oxidising bacteria. PhD thesis, Murdoch University.

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Quantifying the extent and rate of sulphur oxidation in systems catalysed by chemolithotrophic bacteria is inherently difficult due to the presence of solid phase sulphur. The absence of reliable measurements on the extent and rate of sulphur oxidation hinders investigations into the effects that water quality has on the catalysis caused by these organisms. This absence severely hampers attempts to optimise sulphur oxidation in base metal extraction systems and minimise environmental problems associated with acid mine drainage. This study examined the catalysed oxidation of elemental sulphur and soluble reduced sulphur species in an attempt to circumvent the difficulties arising from a solid phase substrate and to provide an understanding of how solution parameters, such as pH and ionic strength, affect the catalytic processes.

Complete oxidation of elemental sulphur and sulphur species result in the formation of sulphuric acid and cause the acidification of the medium. This phenomenon was first examined to determine the conditions under which a proton balance could be used to quantify the conversion of insoluble elemental sulphur to sulphuric acid. Results from these experiments showed that a proton balance can provide estimates of the rate and extent of elemental and solid phase sulphur oxidation but the limiting factor is the performance of the glass electrodes now universally used to determine the activity of the proton in solution. The impact of environmental variables on chemolithotrophic cells growing on sulphur substrates was also examined in this project. The influence of pH, ionic strength and CO2 partial pressures on bacterial yields and sulphur oxidation rates were examined using a number of culturing techniques, including open and closed batch cultures and a reactor system operated at fixed pH values.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Engineering and Information Technology
Supervisor(s): Ralph, David and Hughes, Leonie
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