Efficient Hydrogen photoproduction by synchronously grown cells of a marine cyanobacterium, Synechococcus sp. Miami BG 043511, under high cell density conditions

Abstract

The capability of hydrogen photoproduction under high cell density conditions was examined using synchronously grown cells of nitrogen‐fixing Synechococcus sp. Miami BG 043511. Optimum hydrogen yield was obtained when vessels (25 ml) contained 0.2 to 0.3 mg chlorophyll ^a in 3‐mL cell suspension. During a 24‐h incubation period, an initial phase of hydrogen and carbon dioxide production and a subsequent phase of carbon dioxide uptake and oxygen accumulated as major products after 24 h. after the initial 24‐h. After the initial 24‐h incubation, as high as 7.4 and 3.7 L (at standard condition) of hydrogen and oxygen, respectively, accumulated in vessels with 22‐ml gas phase. This indicated that the pressure in the flask increased to 1.5 atmosphere. Energy conversion efficiency based on photosynthetically active radiation (25 W/m²) was about 2.6%. However, increased pressure somehow reduced the duration of hydrogen production. Duration of hydrogen and oxygen production was prolonged by periodical (24‐h interval) gas replacement during incubation. © 1994 John Wiley & Sons, Inc.