Biohydrogen production in a combination of dark- and photo-fermentation co-culture

• Main Authors: Kuan-Yu Chen, 陳冠宇
• Other Authors: Chun-Hsiung Hung
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/61210361921568130339

碩士 === 國立中興大學 === 環境工程學系所 === 104 === Developing renewable energies is important. Among the renewable energies, hydrogen energy has high development potential. Various organisms have been used to produce hydrogen in recent years. At present, dark and photo fermentation are popular approaches in hydrogen energy production. Dark fermentation takes advantage of the capability of heterotrophic bacteria to ferment carbohydrates under anaerobic or anoxic conditions. Accordingly, this approach obtains energy in the redox reactions, thereby producing volatile fatty acids (VFAs), alcohols, and hydrogen. Photo fermentation exploits the capability of photosynthetic bacteria to convert carbohydrates to ADP and hydrogen with nitrogenase in light surroundings. When dark- and photo-fermentation techniques are combined, dark fermentation produces VFAs and other metabolic byproducts, which can be further converted to hydrogen by the purple non-sulfur bacteria. This method can enhance hydrogen production and energy conversion efficiency. Therefore, this study investigates the hydrogen production capability of combined dark- and photo-fermentation method by co-culturing the dark-fermentation bacteria and the purple non-sulfur bacteria. For dark-fermentation bacteria, the effect of whether a particular light can change the hydrogen production and metabolic byproducts is tested using Clostridium acetobutylicum (CHR5) and Clostridium pasteurianum (CH5). The CHR5 results show that the hydrogen production is decreased by 24%. The main byproducts are acetate and butyrate, and the concentration of the VFAs and the percentage of hydrogen are slightly decreased at a light intensity of 6000 lux. The CH5 results show no difference in hydrogen production, but the concentration of the acetate and butyrate and gas composition are distinctly changed with the same illumination. The test results with or without light still need further analysis. The hydrogen production performance in different glucose concentrations is tested. The results show that the maximum hydrogen production and hydrogen yield of CHR5 and CH5 are obtained in 15 g/L glucose concentration. For the purple non-sulfur bacteria, their capability to convert butyrate to hydrogen is tested. The results show that Rhodopseudomonas faecalis (SBR11), Rhodopseudomonas palustris (C6), Rhodopseudomonas palustris (G11), and Rhodopseudomonas palustris (An3) exhibit such capability. The cumulative hydrogen productions are 171.6, 142.9, 227.0, and 234.0 mL H2 L−1 cultures, respectively, at 1 g/L butyrate concentration after 320 h. In the batch test by combined dark and photo fermentation, CHR5 and CH5 are co-cultured with An3, G11, SBR11, and C6 to produce hydrogen in fixed conditions. The results show that hydrogen production is lesser in co-culture than in dark-fermentation bacteria alone. Moreover, the hydrogen production, gas composition, and metabolic byproducts in co-culture are similar to those in purple non-sulfur bacteria alone. This result may be due to that purple non-sulfur bacteria utilize the carbon source to produce hydrogen, thereby causing acidification. Given that the environment is unfavorable for dark-fermentation bacteria to produce hydrogen, the hydrogen production performance of co-culture decreases. Keywods: bio-hydrogen, combined dark and photo-fermentation, acidification