| Summary: | 碩士 === 國立成功大學 === 環境工程學系碩博士班 === 98 === 80% of global utilized energy comes from fossil fuels, and the energy shortage mainly comes from this dependence. Since the energy issue affects both economy and environment, the governments paid much attention on finding a clean and Sustainability energy. Hydrogen is considered as a clean and efficient energy among renewable energies.
Hydrogen can be produced from organic materials by anaerobic microorganism but the mechanism of fermentative hydrogen production is not clear. Thus, our research will focus on evaluation of fermentative biohydrogen with metabolic flux consideration by Clostridium tyrobutyricum.
In our study, the influent substrates were 12,000 mg/L glucose, temperature was maintained at 35℃, and pH was controlled at 6±0.05 by computer. The reactor was operated at different hydraulic retention times (HRT 18, 12, 8, 6, 4, 3, 2.5, 2 hr), and we collected gas production and water quality data under steady state at each HRT. Our result shows that maximum hydrogen production rate, maximum specific hydrogen production rate and maximum hydrogen concentration, 5.63 mmol H2/L*hr, 5.04 (H2mmoL/g dry weight*hr) and 80%, were all occurred at HRT 2 hr. However, maximum hydrogen yield, 1.42 mol H2/mol-glucose-applied, was observed at HRT 18 hr.
In addition, we used 4 balance systems, e.g. carbon balance, COD, O/R value and NADH, to evaluate the end products. The experimental errors of carbon and COD recovery rates were ±10% respectively. The recovery rate of O/R value was only 55%, because a meager part of end products could not be included in this calculation, the error was enlarged. Besides, the average of NADH balance was 97%.
Finally, we used CellNetAnalyzer to evaluate the rates of metabolic pathways at each HRT. The difference between produced and utilized ATP shows that ATP is shortage in the cell and there was a relationship between the values of shortage ATP and H2. This situation had a relationship with hydrogen yield which is unfavorable based on thermodynamic analysis.
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