Elsabe Botes | University of the Free State (original) (raw)

Current by Elsabe Botes

Patents by Elsabe Botes

Papers by Elsabe Botes

High concentrations of uranium(VI) in the Witwatersrand Basin, South Africa from mining leachate ... more High concentrations of uranium(VI) in the Witwatersrand Basin, South Africa from mining leachate is a serious environmental concern. Treatment systems are often ineffective. Therefore, optimization of a bioremediation system that facilitates the bioreduction of U(VI) based on biostimulation of indigenous bacterial communities can be a viable alternative. Tolerance of the indigenous bacteria to high concentrations of U and the amount of citric acid required for U removal was optimized. Two bioreactor studies which showed effective U(VI) removal more than 99 % from low (0.0037 mg L(-1)) and high (10 mg L(-1)) concentrations of U to below the limit allowed by South African National Standards for drinking water (0.0015 mg L(-1)). The second bioreactor was able to successfully adapt even with increasing levels of U(VI) feed water up to 10 mg L(-1), provided that enough electron donor was available. Molecular biology analyses identified Desulfovibrio sp. and Geobacter sp. among known species, which are known to reduce U(VI). The mineralogical analysis determined that part of the uranium precipitated intracellularly, which meant that the remaining U(VI) was precipitated as U(IV) oxides and TEM-EDS also confirmed this analysis. This was predicted with the geochemical model from the chemical data, which demonstrated that the treated drainage was supersaturated with respect to uraninite > U4O9 > U3O8 > UO2(am). Therefore, the tolerance of the indigenous bacterial community could be optimized to remediate up to 10 mg L(-1), and the system can thus be upscaled and employed for remediation of U(VI) impacted sites.

Nanoparticles are very important materials for implementing nanotechnology in diverse areas and a... more Nanoparticles are very important materials for implementing nanotechnology in diverse areas and are abundant in nature as living organisms operate at a nanoscale. As nanoparticles exhibit interesting size-and shape-dependent physical and chemical properties, the synthesis of uniform nanoparticles with controlled sizes and shapes is of great importance. Nanoparticles are the end products of a wide variety of physical, chemical and biological processes, some of which are novel and radically different and others of which are quite commonplace. The ability to produce nanoparticles with specific shapes and controlled sizes could result in interesting new applications that can potentially be utilized in areas such as optics, electronics and the biomedical field. In the present study, we have demonstrated the ability of the thermophilic bacterium Thermus scotoductus SA-01 to synthesize gold nanoparticles and determined the effect of the physico-chemical parameters on particle synthesis. Furthermore, a protein purified from this bacterium is shown to be capable of reducing HAuCl 4 to form elemental nanoparticles in vitro. The protein was purified to homogeneity and identified through N-terminal sequencing as an ABC transporter, peptidebinding protein. It is speculated that this protein reduces Au(III) through an electron shuttle mechanism involving a cysteine disulphide bridge. Through manipulation of physico-chemical parameters, it was possible to vary nanoparticles in terms of number, shape and size. This is the first report of a transporter protein from a thermophile with the ability to produce nanoparticles in vitro thus expanding the limited knowledge around biological gold nanoparticle synthesis.

International Journal of Environmental Health Research, May 23, 2014

Geophagia is practised in many parts of the world and can be associated with medicinal treatments... more Geophagia is practised in many parts of the world and can be associated with medicinal treatments, ceremonial events and spiritual behaviours/practices. This is the first report on a systematic investigation and description of the bacterial diversity in soil regularly ingested by geophagic individuals using a culture-independent method. Diversity in 17 different mining sites was investigated using denaturing gradient gel electrophoresis. Genetic material from Pantoea, Stenotrophomonas, Listeria, Rhodococcus and Sphingomonads was present in most of the soil samples. Species from these genera are recognised, potential or immerging human pathogens, and are of special interest in immune-compromised individuals. Other genera able to produce a variety of bacteriocins and antimicrobial/antifungal substances inhibitory towards food borne pathogens (Dactylosporangium and Bacillus) and able to degrade a range of environmental pollutants and toxins (Duganella and Massilia) were also present. These essential insights provide the platform for adjusting culturing strategies to isolate specific bacteria, further phylogenetic studies and microbial mining prospect for bacterial species of possible economic importance.

Water SA, Jul 3, 2014

Hexavalent chromium (Cr 6+ ) contamination from a dolomite stone mine in Limpopo Province, South ... more Hexavalent chromium (Cr 6+ ) contamination from a dolomite stone mine in Limpopo Province, South Africa, has resulted in extensive groundwater contamination. In order to circumvent any further negative environmental impact at this site, an effective and sustainable treatment strategy for the removal of up to 6.49 mg/ℓ Cr 6+ from the groundwater was developed. Laboratory-scale, continuous up-flow bioreactors were constructed to evaluate reduction of Cr 6+ , with a residence time of 24 h, an efficiency porosity of 44% and a flow rate of 1.5 mℓ/min. Stoichiometrically balancing terminal electron acceptors in the feed water with a selected electron donor, directed reactor balance for complete Cr 6+ reduction. The microbial community shifted in relative dominance during operation to establish an optimal metal-reducing community, including Enterobacter cloacae, Flavobacterium sp. and Ralstonia sp., which achieved 100% reduction. Evaluation after reactor termination with SEM-EDX and XRD confirmed the establishment of biofilm on the reactor matrix, as well as trivalent chromium (Cr 3+ ) precipitation within the reactor. Due to gravitational force, high concentrations of Cr 3+ were found in the bottom third of the reactor. Based on the results from the laboratory investigation, a 24 000 ℓ fixed-film pilot bioreactor was designed and constructed at this site. Influent flow rates, electron donor injection and automated sampling were remotely controlled by a programmable logic controller (PLC). Similar to the laboratory column study, steady state conditions could be achieved and successful Cr 6+ reduction was evident. This is the first up-scaled, effective demonstration of a biological chromium(VI) bioremediation system in South Africa.

The relationship between the postgraduate supervisor and postgraduate student is commonly describ... more The relationship between the postgraduate supervisor and postgraduate student is commonly described in the literature because of the interesting and sometimes even complex dynamics involved in this process. However, the literature is not always very explicit about the specific expectations of those involved. The findings of a qualitative case study, completed at an American research intensive university (Indiana University, Indianapolis, Indiana, USA) are communicated in the article. Despite the complexity of the research supervision process, the expectations associated with the supervision process remains a unique experience of collaborative learning. A commitment is required from each of the role players to communicate expectations initially and continuously. Furthermore it was noted that an environment should be created for students in which they are respected as colleagues.

Journal of Biotechnology, 2010

Journal of Biotechnology, 2010

South African Journal of Science Vol 103, 2007

S OIL AND WATER SITES WERE SAMPLED AT a South African antimony mine with elevated levels of arsen... more S OIL AND WATER SITES WERE SAMPLED AT a South African antimony mine with elevated levels of arsenic due to the refining process. Enriched media yielded two pure bacterial cultures able to grow in both arsenite and arsenate. These were identified as Stenotrophomonas maltophilia SA Ant 15 and Serratia marcescens SA Ant 16. Stenotrophomonas maltophilia SA Ant 15 was resistant to 10 mmol l -1 arsenite and 20 mmol l -1 arsenate, whereas S. marcescens SA Ant 16 grew in 15 mmol l -1 arsenite and in up to 500 mmol l -1 arsenate, making it the most arsenic-resistant organism described to date. During growth, addition of arsenate or arsenite anions adversely affected biomass production and maximum specific growth rate and, in some instances, longer lag phases were induced. Reduction of arsenate to arsenite partly accounted for the high tolerance of the bacteria to arsenate. Our results suggest the use of these hyper-resistant bacteria as remediation agents in areas where arsenic contamination is prohibitively high.

Water Research Council Report No: 1029/1/04, 2004

High concentrations of uranium(VI) in the Witwatersrand Basin, South Africa from mining leachate ... more High concentrations of uranium(VI) in the Witwatersrand Basin, South Africa from mining leachate is a serious environmental concern. Treatment systems are often ineffective. Therefore, optimization of a bioremediation system that facilitates the bioreduction of U(VI) based on biostimulation of indigenous bacterial communities can be a viable alternative. Tolerance of the indigenous bacteria to high concentrations of U and the amount of citric acid required for U removal was optimized. Two bioreactor studies which showed effective U(VI) removal more than 99 % from low (0.0037 mg L(-1)) and high (10 mg L(-1)) concentrations of U to below the limit allowed by South African National Standards for drinking water (0.0015 mg L(-1)). The second bioreactor was able to successfully adapt even with increasing levels of U(VI) feed water up to 10 mg L(-1), provided that enough electron donor was available. Molecular biology analyses identified Desulfovibrio sp. and Geobacter sp. among known species, which are known to reduce U(VI). The mineralogical analysis determined that part of the uranium precipitated intracellularly, which meant that the remaining U(VI) was precipitated as U(IV) oxides and TEM-EDS also confirmed this analysis. This was predicted with the geochemical model from the chemical data, which demonstrated that the treated drainage was supersaturated with respect to uraninite > U4O9 > U3O8 > UO2(am). Therefore, the tolerance of the indigenous bacterial community could be optimized to remediate up to 10 mg L(-1), and the system can thus be upscaled and employed for remediation of U(VI) impacted sites.

Nanoparticles are very important materials for implementing nanotechnology in diverse areas and a... more Nanoparticles are very important materials for implementing nanotechnology in diverse areas and are abundant in nature as living organisms operate at a nanoscale. As nanoparticles exhibit interesting size-and shape-dependent physical and chemical properties, the synthesis of uniform nanoparticles with controlled sizes and shapes is of great importance. Nanoparticles are the end products of a wide variety of physical, chemical and biological processes, some of which are novel and radically different and others of which are quite commonplace. The ability to produce nanoparticles with specific shapes and controlled sizes could result in interesting new applications that can potentially be utilized in areas such as optics, electronics and the biomedical field. In the present study, we have demonstrated the ability of the thermophilic bacterium Thermus scotoductus SA-01 to synthesize gold nanoparticles and determined the effect of the physico-chemical parameters on particle synthesis. Furthermore, a protein purified from this bacterium is shown to be capable of reducing HAuCl 4 to form elemental nanoparticles in vitro. The protein was purified to homogeneity and identified through N-terminal sequencing as an ABC transporter, peptidebinding protein. It is speculated that this protein reduces Au(III) through an electron shuttle mechanism involving a cysteine disulphide bridge. Through manipulation of physico-chemical parameters, it was possible to vary nanoparticles in terms of number, shape and size. This is the first report of a transporter protein from a thermophile with the ability to produce nanoparticles in vitro thus expanding the limited knowledge around biological gold nanoparticle synthesis.

International Journal of Environmental Health Research, May 23, 2014

Geophagia is practised in many parts of the world and can be associated with medicinal treatments... more Geophagia is practised in many parts of the world and can be associated with medicinal treatments, ceremonial events and spiritual behaviours/practices. This is the first report on a systematic investigation and description of the bacterial diversity in soil regularly ingested by geophagic individuals using a culture-independent method. Diversity in 17 different mining sites was investigated using denaturing gradient gel electrophoresis. Genetic material from Pantoea, Stenotrophomonas, Listeria, Rhodococcus and Sphingomonads was present in most of the soil samples. Species from these genera are recognised, potential or immerging human pathogens, and are of special interest in immune-compromised individuals. Other genera able to produce a variety of bacteriocins and antimicrobial/antifungal substances inhibitory towards food borne pathogens (Dactylosporangium and Bacillus) and able to degrade a range of environmental pollutants and toxins (Duganella and Massilia) were also present. These essential insights provide the platform for adjusting culturing strategies to isolate specific bacteria, further phylogenetic studies and microbial mining prospect for bacterial species of possible economic importance.

Water SA, Jul 3, 2014

Hexavalent chromium (Cr 6+ ) contamination from a dolomite stone mine in Limpopo Province, South ... more Hexavalent chromium (Cr 6+ ) contamination from a dolomite stone mine in Limpopo Province, South Africa, has resulted in extensive groundwater contamination. In order to circumvent any further negative environmental impact at this site, an effective and sustainable treatment strategy for the removal of up to 6.49 mg/ℓ Cr 6+ from the groundwater was developed. Laboratory-scale, continuous up-flow bioreactors were constructed to evaluate reduction of Cr 6+ , with a residence time of 24 h, an efficiency porosity of 44% and a flow rate of 1.5 mℓ/min. Stoichiometrically balancing terminal electron acceptors in the feed water with a selected electron donor, directed reactor balance for complete Cr 6+ reduction. The microbial community shifted in relative dominance during operation to establish an optimal metal-reducing community, including Enterobacter cloacae, Flavobacterium sp. and Ralstonia sp., which achieved 100% reduction. Evaluation after reactor termination with SEM-EDX and XRD confirmed the establishment of biofilm on the reactor matrix, as well as trivalent chromium (Cr 3+ ) precipitation within the reactor. Due to gravitational force, high concentrations of Cr 3+ were found in the bottom third of the reactor. Based on the results from the laboratory investigation, a 24 000 ℓ fixed-film pilot bioreactor was designed and constructed at this site. Influent flow rates, electron donor injection and automated sampling were remotely controlled by a programmable logic controller (PLC). Similar to the laboratory column study, steady state conditions could be achieved and successful Cr 6+ reduction was evident. This is the first up-scaled, effective demonstration of a biological chromium(VI) bioremediation system in South Africa.

The relationship between the postgraduate supervisor and postgraduate student is commonly describ... more The relationship between the postgraduate supervisor and postgraduate student is commonly described in the literature because of the interesting and sometimes even complex dynamics involved in this process. However, the literature is not always very explicit about the specific expectations of those involved. The findings of a qualitative case study, completed at an American research intensive university (Indiana University, Indianapolis, Indiana, USA) are communicated in the article. Despite the complexity of the research supervision process, the expectations associated with the supervision process remains a unique experience of collaborative learning. A commitment is required from each of the role players to communicate expectations initially and continuously. Furthermore it was noted that an environment should be created for students in which they are respected as colleagues.

Journal of Biotechnology, 2010

Journal of Biotechnology, 2010

South African Journal of Science Vol 103, 2007

S OIL AND WATER SITES WERE SAMPLED AT a South African antimony mine with elevated levels of arsen... more S OIL AND WATER SITES WERE SAMPLED AT a South African antimony mine with elevated levels of arsenic due to the refining process. Enriched media yielded two pure bacterial cultures able to grow in both arsenite and arsenate. These were identified as Stenotrophomonas maltophilia SA Ant 15 and Serratia marcescens SA Ant 16. Stenotrophomonas maltophilia SA Ant 15 was resistant to 10 mmol l -1 arsenite and 20 mmol l -1 arsenate, whereas S. marcescens SA Ant 16 grew in 15 mmol l -1 arsenite and in up to 500 mmol l -1 arsenate, making it the most arsenic-resistant organism described to date. During growth, addition of arsenate or arsenite anions adversely affected biomass production and maximum specific growth rate and, in some instances, longer lag phases were induced. Reduction of arsenate to arsenite partly accounted for the high tolerance of the bacteria to arsenate. Our results suggest the use of these hyper-resistant bacteria as remediation agents in areas where arsenic contamination is prohibitively high.

Water Research Council Report No: 1029/1/04, 2004