Parameters affecting the growth and hydrogen production of the green alga Chlamydomonas reinhardtii

The green alga Chlamydomonas reinhardtii has the ability to photosynthetically produce molecular hydrogen (H2) under anaerobic conditions. It offers a biological route to renewable H2 production from sunlight and water. Algal growth and H2 production kinetics must be understood in order to determine appropriate system parameters and develop photobioreactors. Algal biomass should be grown efficiently and economically to attain the high cell densities necessary for H2 production. The nutrient requirements and process conditions that encourage the growth of dense and healthy algal cultures were explored. Anaerobic conditions were imposed by sulphur deprivation, which requires an exchange of the algal growth medium by centrifugation or dilution. A tubular flow photobioreactor featuring a large surface-to-volume ratio was used to monitor and control the key parameters in the H2 production process, including pH, dissolved oxygen, optical density, temperature, agitation and light intensity. A cumulative H2 yield of 3.1 ± 0.3 ml/l of culture was measured.