Isolation and characterization of a unicellular marine green alga exhibiting high activity in dark hydrogen production.

Abstract

Dark hydrogen production by a newly isolated marine green alga, Chlamydomonas MGA 161 was studied. This alga was a halotolerant, not a halophilic type, and grew well in both natural and artificial seawater media. From an experiment with cycloheximide addition, it was found that the hydrogenase reaction in this alga was not a rate-limiting step of dark hydrogen evolution. Starch accumulation increased at a low NH4Cl concentration (0.5mM), at a low temperature (20°C), or at a high NaCl concentration (7%). Hydrogen evolution was correlated with starch degradation rather than starch accumulation, and the molar yield of hydrogen from starch-glucose was very high, at about 2 (mol H2/mol glucose). A comparison of the distribution pattern of fermentation products in various green algae, showed a unique fermentation pattern for Chlamydomonas MGA 161, with high hydrogen evolution but almost no formate.