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Biohydrogen Production by the Thermophilic Bacterium Caldicellulosiruptor saccharolyticus: Current Status and Perspectives

Laboratory of Microbiology, Wageningen University, Dreijenplein 10, 6703 HB Wageningen, The Netherlands
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Life 2013, 3(1), 52-85; https://doi.org/10.3390/life3010052
Received: 5 December 2012 / Revised: 6 January 2013 / Accepted: 7 January 2013 / Published: 17 January 2013
(This article belongs to the Special Issue Extremophiles and Extreme Environments)
Caldicellulosiruptor saccharolyticus is one of the most thermophilic cellulolytic organisms known to date. This Gram-positive anaerobic bacterium ferments a broad spectrum of mono-, di- and polysaccharides to mainly acetate, CO2 and hydrogen. With hydrogen yields approaching the theoretical limit for dark fermentation of 4 mol hydrogen per mol hexose, this organism has proven itself to be an excellent candidate for biological hydrogen production. This review provides an overview of the research on C. saccharolyticus with respect to the hydrolytic capability, sugar metabolism, hydrogen formation, mechanisms involved in hydrogen inhibition, and the regulation of the redox and carbon metabolism. Analysis of currently available fermentation data reveal decreased hydrogen yields under non-ideal cultivation conditions, which are mainly associated with the accumulation of hydrogen in the liquid phase. Thermodynamic considerations concerning the reactions involved in hydrogen formation are discussed with respect to the dissolved hydrogen concentration. Novel cultivation data demonstrate the sensitivity of C. saccharolyticus to increased hydrogen levels regarding substrate load and nitrogen limitation. In addition, special attention is given to the rhamnose metabolism, which represents an unusual type of redox balancing. Finally, several approaches are suggested to improve biohydrogen production by C. saccharolyticus. View Full-Text
Keywords: Caldicellulosiruptor saccharolyticus; biohydrogen; dark fermentation; cellulolytic thermophile; thermodynamics; rhamnose metabolism; pyrophosphate; redox balance; hydrogen inhibition; regulation Caldicellulosiruptor saccharolyticus; biohydrogen; dark fermentation; cellulolytic thermophile; thermodynamics; rhamnose metabolism; pyrophosphate; redox balance; hydrogen inhibition; regulation
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Bielen, A.A.M.; Verhaart, M.R.A.; Van der Oost, J.; Kengen, S.W.M. Biohydrogen Production by the Thermophilic Bacterium Caldicellulosiruptor saccharolyticus: Current Status and Perspectives. Life 2013, 3, 52-85.

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