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Browsing by Author "Harrison, Susan T L"

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Analysis of the microbial community associated with a bioprocess system for bioremediation of thiocyanate- and cyanide-laden mine water effluents

Author: Huddy, Rob ; Kantor, Rose ; Van Zyl, Wynand ; Van Hille, Robert P ; Banfield, Jill ; Harrison, Susan T L Date: Nov 2015 Gold extraction by cyanidation from refractory gold ores results in the formation of thiocyanate- and cyanide-contaminated wastewater effluents that must be treated before recycle or discard. Activated sludge processes, such as ASTER™, can ... Read more
Attachment of Acidithiobacillus ferrooxidans and Leptospirillum ferriphilum cultured under varying conditions to pyrite, chalcopyrite, low-grade ore and quartz in a packed column reactor

Author: Africa, Cindy-Jade ; van Hille, Robert P ; Harrison, Susan T L Date: 2012 The attachment of Acidithiobacillus ferrooxidans and Leptospirillum ferriphilum spp. grown on ferrous medium or adapted to a pyrite mineral concentrate to four mineral substrata, namely, chalcopyrite and pyrite concentrates, a low-grade ... Read more
Development of a method to assay the microbial population in heap bioleaching operations

Author: Coram-Uliana, Nicolette J ; van Hille, Robert P ; Kohr, William J ; Harrison, Susan T L Date: 2005 Heap bioleaching is an economically viable approach to the mining of low-grade ores. Oxidation is microbially assisted, involving a consortium of microorganisms that together span the mesophilic to extreme thermophilic range of temperatures ... Read more
Effect of cell permeability and dehydrogenase expression on octane activation by CYP153A6-based whole cell Escherichia coli catalysts

Author: White, Bronwyn E ; Fenner, Caryn J ; Smit, Martha S ; Harrison, Susan T L Date: 20 Sep 2017 Background: The regeneration of cofactors and the supply of alkane substrate are key considerations for the biocatalytic activation of hydrocarbons by cytochrome P450s. This study focused on the biotransformation of n-octane to 1-octanol using ... Read more
Effect of culture conditions on the competition between lactate oxidisers and fermenters in a biological sulfate reduction system

Author: Oyekola, Oluwaseun O ; Harrison, Susan T L ; van Hille, Robert P Date: 2012 Kinetic constants (μmax and Ks) describing the predominance of lactate oxidation and fermentation were determined in chemostat cultures. The kinetics of sulfate reduction and lactate utilization were determined from 0.5 to 5 d residence times ... Read more c b n d
Effect of culture conditions on the competitive interaction between lactate oxidizers and fermenters in a biological sulfate reduction system

Author: Oyekola, Oluwaseun O ; Harrison, Susan T L ; Van Hille, Robert P Date: 2012 Kinetic constants (lmax and Ks) describing the predominance of lactate oxidation and fermentation were determined in chemostat cultures. The kinetics of sulfate reduction and lactate utilization were determined from 0.5 to 5 d residence times ... Read more
Effect of inoculum size on the rates of whole ore colonisation of mesophilic, moderate thermophilic and thermophilic acidophiles

Author: Tupikina, Olga V ; Minnaar, Susanna H ; Rautenbach, George F ; Dew, David W ; Harrison, Susan T L Date: 2012 Bioheap leaching of low grade copper sulphides has been applied successfully at the commercial scale for the extraction of copper from secondary sulphide minerals. It is important to optimise the inoculation of heaps in order to minimise the ... Read more
The effect of nitrogen limitation on lipid productivity and cell composition in Chlorella vulgaris

Author: Griffiths, Melinda J ; van Hille, Robert P ; Harrison, Susan T L Date: 2014 Chlorella vulgaris accumulates lipid under nitrogen limitation, but at the expense of biomass productivity. Due to this tradeoff, improved lipid productivity may be compromised, despite higher lipid content. To determine the optimal degree ... Read more
The effect of nitrogen limitation on lipid productivity and cell composition in Chlorella vulgaris

Author: Griffiths, Melinda J ; van Hille, Robert P ; Harrison, Susan T L Date: 2014 Chlorella vulgaris accumulates lipid under nitrogen limitation, but at the expense of biomass productivity. Due to this tradeoff, improved lipid productivity may be compromised, despite higher lipid content. To determine the optimal degree ... Read more
The effect of nutrient supplementation on growth and leaching performance of bioleaching bacteria

Author: van Hille, Robert P ; Bromfield, L V ; Botha, S S ; Jones, G ; van Zyl, A W ; Harrison, Susan T L Date: 2009 Heap bioleaching operations are often faced with extended and unpredictable lag periods after inoculation, prior to the establishment of a stable oxidising environment, during which the heap is fully colonised or the inoculum overcomes the ... Read more
Effect of sulphate concentration on the community structure and activity of sulphate reducing bacteria

Author: Oyekola, Oluwaseun O ; van Hille, Rob ; Harrison, Susan T L Date: 2007 This study investigated the effect of sulphate concentration and residence time on the performance of anaerobic sulphate reduction by a mixed sulphate reducing bacteria (SRB) culture using lactate as the sole carbon source and electron ... Read more
Enhancing ARD mitigation by application of benign tailings to reduce the permeability of waste rock dumps

Author: Kotsiopoulos, Thanos ; Harrison, Susan T L Date: Nov 2015 ARD mitigation is considered by reducing the permeability of acid-generating coal interburden waste rock dumps. Fine desulfurised benign tailings were used to conceal exposed surface active sites from air, water and more aggressive sulfur- ... Read more
Evaluation of the ASTERTM process in the presence of suspended solids

Author: van Zyl, Andries W ; Huddy, Robert ; Harrison, Susan T L ; van Hille, Robert P Date: 2014 The ability to recycle and reuse process water is a major contributing factor toward increased sustainability in the mining industry. However, the presence of toxic compounds has prevented this in most bioleaching operations. The ASTERTM ... Read more
Feasibility for value addition to sucrose in South Africa through conversion to platform chemicals

Author: Jegede, Kemi Date: 2018 The world sugar price is constantly changing in response to supply and demand and is currently very low as compared to the prices it is sold at domestically in South Africa. The drop in the worldwide price of sugar is due to its oversupply ... Read more
The generation of toxic reactive oxygen species (ROS) from mechanically activated sulphide concentrates and its effect on thermophilic bioleaching.

Author: Jones, Gavin C ; Corin, Kirsten C ; van Hille, Robert P ; Harrison, Susan T L Date: 2011 Two types of laboratory mills, planetary and vibratory, were used to activate sulphide mineral concentrates mechanically before thermophilic (bio)leaching. These samples were analysed in terms of particle size, surface area, density, SEM, XRD ... Read more
Improving the production of a thermostable amidase through optimising IPTG induction in a highly dense culture of recombinant Escherichia coli.

Author: Olaofe, Oluwafemi A ; Burton, Stephanie G ; Cowan, Don A ; Harrison, Susan T L Date: 2010 The production of a novel thermostable amidase (EC 3.5.1.4) from Geobacillus pallidus RAPc8 using recombinant Escherichia coli BL21 (DE3) was investigated. Volumetric and specific enzyme activities were investigated in relation to inducer ... Read more
In situ investigation and visualisation of microbial attachment and colonisation in a heap bioleach environment: the novel biofilm reactor

Author: Africa, Cindy-Jade ; Harrison, Susan T L ; Becker, Megan ; van Hille, Robert P Date: 2010 In this paper, the development of a novel means of investigating the attachment and subsequent biofilm formation of mineral bioleaching micro-organisms to mineral surfaces in situ is described. The protocol was developed to investigate the ... Read more
The influence of microbial physiology on biocatalyst activity and efficiency in the terminal hydroxylation of n-octane using Escherichia coli expressing the alkane hydroxylase, CYP153A6

Author: Olaofe, Oluwafemi A ; Fenner, Caryn J ; Gudiminchi, Rama Krishna ; Smit, Martha S ; Harrison, Susan T L Date: 2013 Biocatalyst improvement through molecular and recombinant means should be complemented with efficient process design to facilitate process feasibility and improve process economics. This study focused on understanding the bioprocess limitations ... Read more c b
Interference by pigment in the estimation of microalgal biomass concentration by optical density

Author: Griffiths, Melinda J ; Garcin, Clive ; van Hille, Robert P ; Harrison, Susan T L Date: 2011 Optical density is used as a convenient indirect measurement of biomass concentration in microbial cell suspensions. Absorbance of light by a suspension can be related directly to cell density using a suitable standard curve. However, ... Read more c b n d
Investigating heap leaching – the effect of feed iron concentration on bioleaching performance

Author: van Hille, Robert P ; van Zyl, Andries W ; Spurr, Nicholas R L ; Harrison, Susan T L Date: 2010 This paper describes an investigation into the effect of iron concentration in the leach solution on the bioleaching of a low grade copper ore, where chalcopyrite was the dominant copper sulphide. The concentration of dissolved iron is primarily ... Read more

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