Factors Affecting Hydrogen Production by Unicellular Green Alga Chlamydomonas reinhardtii CC-125

In this study, factors affecting H-2 production by the unicellular green alga Chlamydomonas reinhardtii CC-125 were investigated. It was found that the cell density, O-2 concentration and nutrient deprivation in media play important roles in H-2 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 H-2 production rate. Similar to other microorganisms, higher O-2 concentrations decrease H-2 production. However, hydrogenase activity in C. reinhardtii CC-125 seems to show high O-2 tolerance, with an O2I50 of 16.87 +/- 0.81%. Under atmospheric air, maximum H-2 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 H-2 production in this algal strain.