Abstract
Some 30 years ago, hydrogen production by photosynthetic microorganisms was envisaged as a system to convert solar energy. At that time, Mitsui carried out programs to survey microorganisms with high hydrogen production capability. One of the unique strains isolated is a unicellular cyanobacteria assigned to the genus Synechococcus (probably belongs to the genus Cyanothece, according to the current classification). This strain is an aerobic nitrogen fixer and exhibits hydrogen production in a nitrogenase-dependent process. Under argon atmosphere in the light, hydrogen and oxygen accumulated in the vessel at 2 to 1 ratio. When synchronized cells were used, the phases of hydrogen and oxygen production appeared in an alternative manner. During 24 h incubation, as high as 7.4 and 3.7 ml of hydrogen and oxygen accumulated in vessels with 22 ml gas phase. Energy conversion efficiency based on PAR (25 W/m2) was about 2.6%.
