The hyperthermophilic bacterium, Thermotoga neapolitana, has potential for use in biological hydrogen (H 2) production. The objectives of this study were to (1) determine the fermentation stoichiometry of Thermotoga neapolitana and examine H 2 production at various growth temperatures, (2) investigate the effect of oxygen (O 2) on H 2 production, and (3) determine the cause of glucose consumption inhibition. Batch fermentation experiments were conducted at temperatures of 60, 65, 70, 77, and 85°C to determine product yield coefficients and volumetric productivity rates. Yield coefficients did not show significant changes with respect to growth temperature and the rate of H 2 production reached maximum levels in both the 77°C and 85°C experiments. The fermentation stoichiometry for T. neapolitana at 85°C was 3.8 mol H 2, 2 mol CO 2, 1.8 mol acetate, and 0.1 mol lactate produced per mol of glucose consumed. Under microaerobic conditions H 2 production did not increase when compared to anaerobic conditions, which supports other evidence in the literature that T. neapolitana does not produce H 2 through microaerobic metabolism. Glucose consumption was inhibited by a decrease in pH. When pH was adjusted with buffer addition cultures completely consumed available glucose.
- Thermotoga neapolitana