Role of Light Intensity and Temperature in the Regulation of Hydrogen Photoproduction by the Marine Cyanobacterium Oscillatoria sp. Strain Miami BG7

Abstract

The effects of several key environmental factors on the development and control of hydrogen production in the marine blue-green alga (cyanobacterium) Oscillatoria sp. strain Miami BG7 were studied in relation to the potential application of this strain to a bio-solar energy technology. The production of cellular biomass capable of evolving hydrogen gas was strongly affected by light intensity, temperature, and the input of ammonia as a nutrient. Depletion of combined nitrogen from the growth media was a prerequisite for the initiation of hydrogen production. Maximum hydrogen-producing capability coincided with the end of the linear phase of growth. Hydrogen production exhibited considerable flexibility to environmental extremes. The rate of production saturated at low light intensities (i.e., 15 to 30 μEinsteins/m 2 per s), and no photoinhibition was observed at high light intensity (i.e., 1,000 μEinsteins/m 2 per s). The upper temperature limit for production was 46°C. Above the light compensation point for O 2 evolution H 2 production was inhibited. However, this problem was alleviated by two related phenomena. (i) The capacity of cells to evolve oxygen deteriorated with increasing culture age and nitrogen depletion, and (ii) the ability of these cells to produce oxygen in closed anaerobic hydrogen production systems was temporally limited.