Comparative study of the oxygen tolerance of Chlorella pyrenoidosa and Chlamydomonas reinhardtii CC124 in photobiological hydrogen production

In this study, oxygen tolerance of five photohydrogen-producing green algal species, Chlamydomonas moewusii, Chlorella fusca, Chlorella pyrenoidosa, Chlamydomonas reinhardtii and Scenedesmus obliquus, were first evaluated comparatively. These green algae varied in O2-tolerance. C. pyrenoidosa exhibited notable O2-tolerance and was investigated comparatively to that of C. reinhardtii. We used an improved O2-tolerance detection method to eliminate the effects of O2 dissolving rate. Results showed that the O2I50 values of C. pyrenoidosa cells (in vivo) and cell lysate (in vitro) were 139% and 61% higher than those of C. reinhardtii, respectively. Furthermore, owing to the higher O2-tolerance, C. pyrenoidosa cells could evolve hydrogen at a higher threshold of O2 content in the photobiological hydrogen production process and kept releasing H2 for more than 260 h under continuous illumination compared to 60 h in C. reinhardtii did under the same conditions.