Browsing by Author "Bromfield, Lucinda"

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    Factors affecting the attachment of Metallosphaera hakonensis during the colonisation of low grade mineral sulphide heaps
    (2011) Bromfield, Lucinda; Van Hille, Rob
    This thesis pertains to the extraction of copper via heap bioleaching, focussing specifically on the bioleaching of the mineral sulphide, chalcopyrite (CuFeS2). Industrial heap bioleaching offers an attractive alternative to conventional extraction methods, such as smelting, for processing low grade ores. There remain a number of operational challenges associated with bioleaching heaps, such as the lag time before efficient extraction is achieved and ineffective heap inoculation, as well as the difficulty in controlling the conditions within the heap.
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    A modified pH drift assay for inorganic carbon accumulation and external carbonic anhydrase activity in microalgae
    (Springer, 2014-01) van Hille, Rob; Fagan, Marijke A; Bromfield, Lucinda; Pott, Robert
    The threat of global warming due to CO2 emissions has stimulated research into carbon sequestration and emissions reduction technologies. Alkaline scrubbing allows CO2 to be captured as bicarbonate, which can be photochemically fixed by microalgae. The carbon concentrating mechanism (CCM), of which external carbonic anhydrase is a key component, allows the organisms to utilise this bicarbonate. In order to select a suitable strain for this application, a screening tool is required. The current method for determining carbonic anhydrase activity, the Wilbur and Anderson assay, was found to be unsuitable as a screening tool as the associated error was unacceptably large and tests on whole cells were inconclusive. This paper presents the development of a new, whole cell assay to measure inorganic carbon uptake and external carbonic anhydrase activity, based on classical pH drift experiments. Spirulina platensis was successfully used to develop a correlation between the specific carbon uptake (C) and the specific pH change (dpH). The relationship is described by: C (mmol C (g dry algae)-1 h-1) = 0.064 × (dpH). Inhibitor and salt dissociation tests validated the activity and presence of external carbonic anhydrase, and allowed correlation between the Wilbur and Anderson assay and the new whole cell assay. Screening tests were conducted on Spirulina platensis, Scenedesmus sp., Chlorella vulgaris and Dunaliella salina which were found to have carbon uptake rates of 5.76, 5.86, 3.86 and 2.15 mmol C (g dry algae)-1 h-1 respectively. These results corresponded to the species’ known bicarbonate utilisation abilities and validated the use of the assay as a screening tool.