To develop an integrated process of CO2- fixation and H-2 photoproduction by marine green microalga Platymonas subcordiformis, the impact of algal cells grown in CO2- supplemented air bubble column bioreactor was investigated on H-2 photoproduction regulated by carbonylcyanide m- chlorophenylhrazone. Highest cell growth ( 3.85 9 10(6) cells ml(-1)), starch content ( 0.25 +/- 0.08 mg per 10(6) cells) and hydrogen production ( 50 +/- 3 ml1(-1)) were achieved at 3% CO2-supplemented culture, which are respectively 1.4, 2.1, 1.5- fold of the air-supplemented culture. Improved H-2 production correlated well with the increase in starch accumulation. In this process, the algal cells have been recycled for stable H-2 production of 40 - 50 ml l(-1) over five cycles.