Hydrogen production of the hyperthermophilic eubacterium, Thermotoga neapolitana under N-2 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 (N-2) 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 N-2 sparging after the H-2 content in the headspace reached the maximum levels gave an increase of H-2 production by 78% from 1.82 to 3.24 mol H-2/mol glucose and by 56% from 1.41 to 2.20 mol H-2/mol xylose. This result suggested that the removal of the produced H-2 from the gas headspace of the limited-volume. closed culture vial when it achieves the maximum level of H-2 tolerance of the bacterium is a necessary technique to improve its H-2 yield. (C) 2009 Elsevier Ltd. All rights reserved.