LAUSR

This study investigated the determination of hydrogen production by three H2-producing microorganisms (Thermotoga maritima, Thermococcus kodakarensis KOD1 and Enterobacter cloacae) cultured in 116-mL serum bottles. A gas pressure manometer was used to measure total pressure in the serum-bottle headspace. It was demonstrated that total pressure is the sum of the saturation pressure of water, the pressure expansion of gases, and the partial pressures of H2 () and CO2 (). A linear relationship was established between the partial pressure of H2 measured by gas chromatography and the sum of the partial pressures of H2 and CO2 measured by the manometer. When pH of culture medium was not controlled (pH decreased from 7 to 5), the ratio was close to stoichiometric H2/CO2 yield ratio of the most plausible metabolic pathways of each strain. values were 1.7, 1.9 and 0.9 for T. maritima, T. kodakarensis and E. cloacae, respectively. In these experimental conditions, can be deduced from total pressure measured by manometer.