Try to prolong photo-hydrogen production of Rhodopseudomonas palustris NifAnQ for long-term operation under continuous condition

• Main Authors: Fa-Yi Sung, 宋法逸
• Other Authors: 李季眉
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/68208752262720161889

碩士 === 國立中興大學 === 環境工程學系所 === 102 === Environmental concerns, energy shortage, and consequently increasing energy costs result in the need to produce sustainable and renewable fuels. As Hydrogen has high energy density (142 MJ/Kg), a sustainable platform of hydrogen utilization can be established if it can be generated sustainably and used safely, as well as being stored and transported efficiently. There are various ways to produce hydrogen, among which photosynthetic hydrogen production by purple non-sufur photosynthetic bacteria (PNSB) is one of the favorable methods for biohydrogen production because of its high substrate conversion efficiency and its capability of utilizing abundant substrates. The most serious problem of photohydrogen production is that hydrogen production is inhibited by high ammonium concentration. The hydrogen production center of PNSB, the nitrogenase, is regulated by NifA protein. High ammonium concentration will inhibit NifA protein activities, and hence inhibit the transcription of nitrogenase gene and its expression. As a result, no hydrogen can be produced. The mutant of Rhodopseudomonas palustris WP3-5, Rhodopseudomonas palustris NifAnQ was constructed by molecule biotechnology. This mutant can tolerate high ammonium concentration. In this study, this mutant was employed to treat dark-fermentation effluent as substrate to recover hydrogen energy. The dark-fermentation effluent is rich in organic acid including acetate (1~6 g/L), lactate(1 g/L), butyrate(0.4~0.6 g/L), and high ammonium concentration(135 mg/L). This study treats the effluent as continuous culture condition’s substrate. To stabilize the pH value in the reactor, a continuous monitoring system was set up to prevent non-toxic form from transforming to toxic form of ammonium. At a high level of ammonium concentration with acetate and butyrate being carbon sources, the mutant photobioreactor operated continuously at HRT = 12 hr ; the maximum hydrogen concentration and hydrogen production rate are 74% and 172 mL-H2/day. At a high level of ammonium concentration with lactate being carbon source, it was proven that the wild type photobioreactor could not generate hydrogen. This study proved that mutant photobioreactor can operate under continuous culture condition with high ammonium concentration synthetic wastewater, and it can generate hydrogen continuously over 57 days. This demonstrates that the mutant photobioreactor has the capacity to treat effluent with high ammonium concentration to recover most of hydrogen energy.