Chiang Mai Journal of Science

In this study, factors affecting H2 production by the unicellular green alga Chlamydomonas reinhardtii CC-125 were investigated. It was found that the cell density, O2 concentration and nutrient deprivation in media play important roles in H2 production by C. reinhardtii CC-125. C. reinhardtii CC-125 at a cell age of 36 hours with an optical density at 750 nm of 0.8 shows the highest H2 production rate. Similar to other microorganisms, higher O2 concentrations decrease H2 production. However, hydrogenase activity in C. reinhardtii CC-125 seems to show high O2 tolerance, with an O2I50 of 16.87 ± 0.81%. Under atmospheric air, maximum H2 production of 100.90 ± 7.92 and 107.47 ± 3.72 mL L-1 was found in cells incubated in sulfur-deprived and sulfur-nitrogen-deprived media, respectively, after 7 days of incubation. The deprivation of both sulfur and nitrogen prolongs H2 production in this algal strain.