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    Evaluation of hydrogen production by Rhodobacter sphaeroides OU001 and its hupSL deficient mutant using acetate and malate as carbon sources
    (PERGAMON-ELSEVIER SCIENCE LTD, 2009) Kars, Goekhan; Gunduz, Ufuk; Yucel, Meral; Rakhely, Gabor; Kovacs, Kornel L.; Eroglu, Inci
    Rhodobacter sphaeroides O.U.001 is one of the candidates for photobiological hydrogen production among purple non-sulfur bacteria. Hydrogen is produced by Mo-nitrogenase from organic acids such as malate or lactate. A hupSL in frame deletion mutant strain was constructed without using any antibiotic resistance gene. The hydrogen production potential of the R. sphaeroides O.U.001 and its newly constructed hupSL deleted mutant strain in acetate media was evaluated and compared with malate containing media. The hupSL(-) R. sphaeroides produced 2.42 l H-2/l culture and 0.25 l H-2/l culture in 15 mM malate and 30 mM acetate containing media, respectively, as compared to the wild type cells which evolved 1.97 l H-2/l culture and 0.21 l H-2/l culture in malate and acetate containing media, correspondingly. According to the results, hupSL- R. sphaeroides is a better hydrogen producer but acetate alone does not seem to be an efficient carbon source for photo-heterotrophic H-2 production by R. sphaeroides. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.
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    Towards a super H-2 producer: Improvements in photofermentative biohydrogen production by genetic manipulations
    (PERGAMON-ELSEVIER SCIENCE LTD, 2010) Kars, Goekhan; Gunduz, Ufuk
    Photofermentative hydrogen production by purple non-sulfur bacteria is a potential candidate among biological hydrogen production methods. Hydrogen is produced under anaerobic conditions in light using different organic substrates as carbon source. The hydrogen evolution occurs mainly through the catalytic activity of the nitrogenases under non-repressive concentrations of ammonia. However, total hydrogen production is constrained due to several reasons in purple non-sulfur (PNS) bacteria, such as consumption of hydrogen by uptake hydrogenase, inefficient hydrogen production capacity of nitrogenase, limited electron flow to the nitrogenase, sensitivity of nitrogenase towards ammonia, etc. Hence, PNS bacteria need to be manipulated genetically to overcome these limitations and to make the process practically feasible. This review focuses on various approaches for the genetic improvement of biohydrogen production by PNS bacteria. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.