Hydrogen production of the hyperthermophilic eubacterium, Thermotoga neapolitana under N2 sparging condition.

Gas sparging was found to be a useful technique to reduce hydrogen partial pressure in the liquid phase to enhance the hydrogen yields of strictly anaerobically fermentative bacteria. The effect of nitrogen (N2) sparging on hydrogen yield was investigated in sterile and non-sterile conditions using a pure strain of the hyperthermophilic eubacteria, Thermotoga neapolitana with glucose or xylose as a carbon source. The maximum hydrogen accumulations reached 41% of the gaseous mixtures after 30–40 h. Two applications of N2 sparging after the H2 content in the headspace reached the maximum levels gave an increase of H2 production by 78% from 1.82 to 3.24 mol H2/mol glucose and by 56% from 1.41 to 2.20 mol H2/mol xylose. This result suggested that the removal of the produced H2 from the gas headspace of the limited-volume, closed culture vial when it achieves the maximum level of H2 tolerance of the bacterium is a necessary technique to improve its H2 yield.