To develop an integrated process of CO(2)-fixation and H(2) photoproduction by marine green microalga Platymonas subcordiformis, the impact of algal cells grown in CO(2)-supplemented air bubble column bioreactor was investigated on H(2) photoproduction regulated by carbonylcyanide m-chlorophenylhrazone. Highest cell growth (3.85 x 10(6) cells ml(-1)), starch content (0.25 +/- 0.08 mg per 10(6)cells) and hydrogen production (50 +/- 3 ml l(-1)) were achieved at 3% CO(2)-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.