| Summary: | 碩士 === 國立中興大學 === 環境工程學系所 === 97 === Hydrogen is a clean and highly efficient fuel that produces water instead of CO2 after combustion comparing with fossil fuel. Among various H2 production technologies, the biological approach as a sustainable and environmental friendly method has received much attention since several waste materials can be used for hydrogen production. The microorganisms with the ability of hydrogen production can be divided into anaerobic fermentation and photosynthetic bacteria. Purple non-sulfur bacteria as one kind of photosynthetic bacteria, can use sunlight as energy source and volatile fatty acids (VFAs) as electron donor to produce hydrogen at high production rate without oxygen inhibition problem. Moreover, they also contain the ability of accumulating poly-hydroxybutyrate (PHB) under unbalanced growth, which is similar to biohydrogen production. This may cause the competition of reduced power between two mechanisms. For better hydrogen or PHB yield control, to clarify the relationship between PHB accumulation and hydrogen production is an important issue. Therefore, the aim of this research was mainly to explore their correlation under different incubation conditions using a series of batch experiments. The applied strain was Rhodopseudomonas palustris WP3-5, and the investigated factors included initial substrate concentration, pH and substrate sorts.
When the initial acetate concentrations were 3.0 mM, 7.8 mM and 13.3 mM, the final hydrogen production volumes were 74.0 mL, 112.0 mL and 162.6 mL, respectively. The hydrogen accumulative volume increased as the initial acetate concentration increased. However, PHB content in the cell did not have an obvious variation even if the initial substrate concentration was different. The maximum PHB content in each substrate condition was 10%.
In the results of various substrates effect, butyrate was the best electron donor for hydrogen production. The cumulative volume was 201.0 mL, and H2 yield was 1.10 mole H2/mole butyrate. Malate and lactate were not the suitable substrates for PHB accumulation, and the highest content were 0.00% and 3.85% respectively.
The optimum pH for growth was 6 when acetate as the substrate. High pH was not suitable for biomass growth. While pH value was above 9 or below 5, the biomass growth was completely inhibited. The best pH value for hydrogen production was 8, and the hydrogen accumulative volume was 84.3 mL. However, the best H2 yield was 6.8 after calculation (1.10 mole H2/mole acetate). The maximum PHB content was measured at pH values of 6.8 and 8.0.
|
|---|
