Date

2023-1-26

Author

Hoşafcı, Ertan

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The aim of this thesis study is to investigate factors affecting hydrogen (H2) and poly-hydroxybutyrate (PHB) production via photofermentation using two strains of Rhodobacter capsulatus species. To this purpose, three experimental designs were set up, namely Set 1, Set 2 and Set 3. In Set 1, various approaches in pretreatment of bacterial biomass were investigated. For R. capsulatus Wild Type (WT) strain, employment of different pretreatment methods did not make a significant difference, where an average of 29.6% of cell dry weight (cdw) PHB was observed. For mutant R. capsulatus YO3 strain, effect of drying was observed to be significant, with non-dried biomass samples yielding 40.1% of cdw average PHB compared to 28.2% of cdw for dried samples. It was concluded that YO3 should be adopted as the strain to be used in the following sets to be conducted and should not be subjected to drying. In Set 2, effect of increasing sodium (Na+) concentration was investigated as a potential stress condition, using two different substrate types, namely acetate and sucrose. As an indirect result of Na+ increase up to 4000 mgNa+/L, increasing pH was observed to be a significant stress condition. Maximum PHB accumulation was observed as 57.7 ± 5.2% and 3.3 ± 0.4% of cdw for acetate and sucrose, respectively. Maximum hydrogen productivities were observed as 0.58 ± 0.03 mmol/L·h and 0.73 ± 0.06 mmol/L·h, respectively for acetate and sucrose-containing reactors. In Set 3, effect of pH as a stress condition was investigated in high and low Na+ conditions. Maximum PHB accumulation was observed to be 57.5 ± 0.2% of cdw at 8.50 pH and 33.6 ± 2.0% of cdw at 7.70 pH for low and high Na+ conditions, respectively. Maximum hydrogen productivity was observed as 0.42 ± 0.01 mmol/L·h at pH 7.00.

Subject Keywords

Rhodobacter capsulatus, PHB Production, Hydrogen Production, Sodium Accumulation, Effect of pH

URI

https://hdl.handle.net/11511/102572

Collections

Graduate School of Natural and Applied Sciences, Thesis