Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Sydney, 2007. / Title from title screen (viewed may 17, 2007). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Biomedical Sciences, Faculty of Health Sciences. Degree awarded 2007; thesis submitted 2006. Includes bibliographical references. Also issued in print.

Thesis (M.Sc.) (Hons)--University of Western Sydney, 2008. / A thesis presented to the University of Western Sydney, College of Health and Science, School of Biomedical and Health Sciences, in fulfilment of the requirements for the degree of Master of Science (Honours). Includes bibliographies.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

No description available.

The enzymatic reduction of a high-valence form of metals to a low-valence reduced form has been proposed as a strategy to treat water contaminated with a range of metals and radionuclides. Metal reduction by sulphate reducing bacteria (SRB) is carried out either chemically (involving reduction by hydrogen sulphide) or enzymatically (involving redox enzymes such as the hydrogenases). While reduction of metal ions by hydrogen sulphide is well known, the enzymatic mechanism for metal reduction is poorly understood. The aims of this study were to investigate the role of SRB in facilitating platinum removal, and to investigate the role of a hydrogenase in platinum reduction in vitro. In order to avoid precipitation of platinum as platinum sulphide, a resting (non-growing) mixed SRB culture was used. The maximum initial concentration of platinum (IV), which SRB can effectively remove from solution was shown to be 50 mg.l⁻¹. Electron donor studies showed high platinum (IV) uptake in the presence of hydrogen, suggesting that platinum (IV) uptake from solution by SRB requires careful optimization with respect to the correct electron donor. Transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analysis indicated that platinum was being precipitated in the periplasm, a major area of hydrogenase activity in SRB. Purification of the hydrogenase by ammonium sulphate precipitation (65%), Toyopearl-Super Q 650S ion exchange and Sephacry 1 S-100 size exclusion chromatography revealed that the hydrogenase was monomeric with a molecular weight of 58 KDa, when analyzed by 12% SDS-PAGE. The purified hydrogenase showed optimal temperature and pH at 35°C and 7.5 respectively, and a poor thermal stability. In vitro investigation of platinum reduction by purified hydrogenase from mixed SRB culture showed that hydrogenase reduces platinum only in the presence of hydrogen. Major platinum (IV) reduction was observed when hydrogenase was incubated with cytochrome C₃ (physiological electron carrier in vivo) under hydrogen. The same observations were also noted with industrial effluent. Collectively these findings suggest that in vitro platinum reduction is mediated by hydrogenase with a concerted action of cytochrome C₃ required to shuttle the electron from hydrogenase.

No description available.

Thesis (PhD)--Stellenbosch University, 2012. / See full text for abstract. / Sien volteks vir opsomming