Photoautotrophic hydrogen production by Chlorella pyrenoidosa without sulfur-deprivation

In this study, a photoautotrophic hydrogen production of Chlorella pyrenoidosa was presented, with NaHCO3 (10 mM) instead of organic carbon and DCMU addition (10 μM) instead of sulfur-deprivation. The results showed that the algal O2 evolution was significantly inhibited by DCMU, and the earlier it was added the more serious the inhibition was. Overall, when DCMU was added within 9 h after illumination, the relative O2 concentrations could be regarded as anaerobic (<6%). Comparatively, the algal H2 photoproduction was also influenced by DCMU addition time, but with opposite trend to the O2 evolution. In summary, the highest H2 production occurred when DCMU was injected at 9 h, being fourfold of that in sulfur-deprived TAP medium (93.86 mL L−1 vs 23.12 mL L−1). Further study suggested that the higher H2 productivity might be mainly due to a relatively higher PSII photochemical activity.