Hydrogen production by pure and mixed thermophilic cultures

Hydrogen, a carbon-free energy carrier producing H2O as the only by-product when it burns, is a clean, promising alternative to fossil fuel. In contrast to chemical and physical routes, biological production of hydrogen is economical, highly effective and pollution free. Dark fermentative hydrogen production has been carried out with a variety of substrates and with different pure and mixed cultures. Fermentations approaching the maximum theoretical yield, however, could not yet be achieved.

In this study, the performance of anaerobic hydrogen-producing monocultures of the extreme thermophiles Caldicellulosiruptor owensensis and C. kristjanssonii as well as cultures of thermophilic microflora enriched form local compost and wastewater sludge samples was investigated. Hydrogen production efficiencies were compared to that of the extreme thermophile C. saccharolyticus, which was used here as a benchmark organism. Some of the tested thermophiles were subsequently grown together in a continuous stirred tank reactor (CSTR) where the microbial population was analyzed at different HRTs through denaturing gradient gel electrophoresis (DGGE) of 16s rDNA. Our aim is to obtain a stable, efficient hydrogen-producing consortium that has not been naturally met before. This work is part of the Integrated Project, HYvolution, for non-thermal production of hydrogen from biomass, funded in the EU FP6.