Microaerobic hydrogen production by photosynthetic bacteria in a double-phase photobioreactor

The rate of hydrogen production by the marine nonsulfur photosynthetic bacterium, Rhodovulum sp., increased with increasing light intensity. A light intensity of 1800 W/m(2) hydrogen production rate was achieved at the rate of 9.4 micromol/mg dry weight/h. The hydrogen production of this strain was enhanced by the addition of a small amount of oxygen (12 micromol O(2)/reactor). Intracellular ATP content was most efficiently accumulated under microaerobic, dark conditions. Hydrogen production rate by Rhodovulum sp. was investigated using a double-phase photobioreactor consisting of light and dark compartments. This rate was compared with data obtained using a conventional photobioreactor. Rhodovulum sp. produced hydrogen at a rate of 0.38+/-0.03 micromol/mg dry weight/h under microaerobic conditions using the double-phase photobioreactor. The hydrogen production rate was four times greater under microaerobic conditions, as compared with anaerobic conditions using either type of photobioreactor. Hydrogen production using a double-phase photobioreactor was demonstrated continuously at the same rate for 150 h.