Electronic Theses and Dissertations (PhDs)

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Browsing Electronic Theses and Dissertations (PhDs) by Author "Mol, Michael"

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    Parageobacillus thermoglucosidasius and the water-gas shift reaction: Investigating the influences of gas composition and H2- uptake hydrogenases
    (University of the Witwatersrand, Johannesburg, 2024) Mol, Michael; Maayer, De
    H2 gas is an increasingly important commercial reagent in a range of industries, including as a potential fuel and energy carrier. Production of H2 gas is carried out almost exclusively reliant on fossil fuel reformation through a relatively limited set of environmentally harmful processes. Pressing environmental concerns and the shift in climate policies towards greater incorporation of cleaner H2 gas production strategies and the implementation of H2 as a more sustainable and environmentally friendly alternative energy vector have necessitated development of renewable and cleaner H2 production processes. Chapter one discusses available literature on the present applications, predominant production processes and emerging alternative production strategies of H2 gas, with particular focus on the applicability and mechanism of biological H2 gas production by the thermophile, Parageobacillus thermoglucosidasius, via the water-gas shift reaction. The application of P. thermoglucosidasius to produce H2 gas is presently in its formative laboratory-scale stage of development. Although progress has been made at a fundamental level, various aspects of P. thermoglucosidasius H2 gas metabolism, remain uncharacterised or poorly understood. In Chapter two, the potential influences of two putative H2-uptake hydrogenases, encoded on the genome of a P. thermoglucosidasius strain previously identified to conduct the hydrogenogenic biological water-gas shift reaction was explored through knock- out mutagenesis. Furthermore, in Chapter three, to establish the practical implementation of pertinent and inexpensive gas feedstocks for the water-gas shift reaction, we explored the influences of various industrial mimetic gas feedstock compositions on the H2 gas evolution-, metabolic- and growth-profiles of P. thermoglucosidasius. Considering the highly variable compositions of industrial off-gases, which may contain oxygen and the highly sensitive nature of this system to oxygen, we further explored the impacts of varied volumetric and temporal oxygen perturbations on the system. Aside from hydrogen production, P. thermoglucosidasius and closely related thermophilic taxa from the genera Parageobacillus and Saccharococcus represent appealing targets for various other biotechnological developments. In Chapter four, we performed a comprehensive comparative genomic and phylogenomic analysis to further explore the biotechnological potential of Parageobacillus and Saccharococcus spp. for a range of whole cell applications as well as a source of industrially relevant thermostable enzymes