Analysis of H2 to CO2 yield and physiological key parameters of Enterobacter aerogenes and Caldicellulosiruptor saccharolyticus

In our study two strains, Enterobacter aerogenes and Caldicellulosiruptor saccharolyticus, were chosen as model microorganisms for investigation of biohydrogen production. By using E. aerogenes, operated in repetitive batch mode, the highest cumulative volumetric hydrogen evolution rate was obtained at an initial glucose concentration of 13.7 g/L. Growing C. saccharolyticus in repetitive batch mode on xylose revealed that complex media resulted in higher volumetric hydrogen productivities but lower hydrogen yields than defined media. Chemostat culture investigations of E. aerogenes and C. saccharolyticus on glucose revealed that higher dilution rates resulted in higher biohydrogen productivities, but also in lower product yields. The highest hydrogen volumetric productivities were obtained with E. aerogenes, while the highest product to substrate yield (Y(H2/s)) and hydrogen to carbon dioxide yield (Y(H2/CO2)) were obtained with C. saccharolyticus. Y(H2/CO2) is an important physiological parameter, regarding a future integration of biohydrogen production into the 5th generation of biofuels.