Hydrogen and poly-beta hydroxy butyric acid production and expression analyses of related genes in rhodobacter capsulatus at different acetate concentrations

Özsoy, Burcu
Hydrogen, which is a clean energy source, is one of the alternatives for fossil fuels. Biological hydrogen production is one of the hydrogen production methods. Rhodobacter capsulatus is a photosynthetic bacterium that produces hydrogen via photofermentation. R. capsulatus can also synthesize some valuable by-products such as Poly-beta- hydroxy butyric acid (PHB), which is a biodegradable bioplastic. In a two stage biohydrogen production system, which is combination of dark fermentation and photofermentation, dark fermentor effluents are used for photofermentation by R.capsulatus. Dark fermentor effluents usually contain high amount of acetate. High amount of acetate may decrease the efficiency of hydrogen production by causing high amount of PHB production. Therefore, it is significant to determine optimum acetate concentration for photofermentation. In this study, the effects of acetate concentration on hydrogen and PHB production by R.capsulatus were investigated by growing bacteria at various acetate concentrations (10 mM-65 mM). In addition, gene expression analysis was performed to investigate the effects of acetate at transcriptional level. For this purpose, expression levels of the genes that encode nitrogenase which is the enzyme that catalyzes hydrogen production and PHB synthase, which is the key enzyme of the PHB synthesis pathway, are examined. Optimum acetate concentration for photofermentation with high hydrogen yield and low PHB amount was determined to be in the range 25 mM-50 mM. nifD expression was found to be high at optimum acetate concentrations and phaC expression was found to be the highest at 65 mM.


Expression analysis of nitrogenase genes in rhodobacter sphaeroides o.u.001 grown under different physiological conditions
Akköse, Sevilay; Gündüz, Ufuk; Department of Biology (2008)
Hydrogen has an extensive potential as a clean and renewable energy source. Photosynthetic, non-sulphur, purple bacteria, Rhodobacter sphaeroides O.U.001 produces molecular hydrogen by nitrogenase enzyme. Nitrogenase enzyme is encoded by nifHDK genes and expression of the structural genes, nifHDK, is controlled by NifA which is encoded by nifA gene. The transcription of nifA is under the control of Ntr system and product of prrA gene. Relationship between the genes that have roles in nitrogenase synthesis s...
Hydrogen Production By R. Capsulatus On Dark Fermenter Effluent Of Potato Steam Peel Hydrolysate
Afsar, N.; Ozgur, E.; Gurgan, M.; de Vrije, T.; YÜCEL, MUSTAFA; Gündüz, Ufuk; Eroglu, I. (2009-05-13)
Biohydrogen is a promising energy source since it is clean and renewable. The HYVOLUTION project (EU 6th Framework Programme) is aimed to develop an integrated process in which biomass is utilized for the biohydrogen production in two steps. In the first step biomass is fermented to acetate, lactate, CO2 and hydrogen by an extreme thermophile (Caldicellulosiruptor saccharolyticus). In the second step, acetate and lactate is converted to hydrogen and CO2 by photofermentation with purple nonsulfur bacteria. ...
Biohydrogen production by Rhodobacter capsulatus on acetate at fluctuating temperatures
Ozgur, Ebru; Uyar, Basar; Ozturk, Yavuz; Yucel, Meral; Gündüz, Ufuk; Eroglu, Inci (2010-03-01)
Hydrogen is a clean energy alternative to fossil fuels. Photosynthetic bacteria produce hydrogen from organic compounds under anaerobic, nitrogen-limiting conditions through a light-dependent electron transfer process. In this study, the hydrogen production efficiency of phototrophic bacteria, Rhodobacter capsulatus and its Hup mutant strain (an uptake hydrogenase deleted strain) were tested on different initial acetate concentrations at fluctuating temperatures with indoor and outdoor photobioreactors. Ace...
Novel bimetallic mesoporous catalysts for hydrogen production through steam reforming of ethanol
Şener, Canan; Doğu, Timur; Doğu, Gülşen; Department of Chemical Engineering (2012)
Hydrogen is considered as an alternative clean energy source due to the depletion of fossil fuels and related environmental problems. Steam reforming of bio-ethanol, has excellent potential for hydrogen production, with CO2 neutrality. Ni, Pd and Pt are the most active metals for steam reforming of ethanol. Improving catalytic activity of supported Ni catalyst by incorporating small amount of Pd or Pt is a successful method for increasing activity and stability of the catalyst. Development of active and sta...
Hydrogen production from ethanol over mesoporous alumina based catalysts and microwave reactor applications
Gündüz, Seval; Doğu, Timur; Department of Chemical Engineering (2014)
Due to fast depletion of fossil fuel resources and related environmental impact of CO2 emissions, the interest in hydrogen as a clean energy carrier has recently increased. Hydrogen production from bio-ethanol, which already contains large amount of water, by steam reforming process, has shown excellent potential with CO2 neutrality and renewability. Steam reforming of ethanol (SRE) process has a highly complex reaction network including numerous side reactions which decrease hydrogen yield and have a negat...
Citation Formats
B. Özsoy, “Hydrogen and poly-beta hydroxy butyric acid production and expression analyses of related genes in rhodobacter capsulatus at different acetate concentrations,” M.S. - Master of Science, Middle East Technical University, 2012.