Photoautotrophic hydrogen production by nitrogen-deprived Chlamydomonas reinhardtii cultures

Abstract

In this study we have demonstrated the possibility of phototrophic hydrogen production in C. reinhardtii under N-deprived conditions. When tested under air + CO2, and Ar + CO2 N-deprived C. reinhardtii demonstrated decrease in PSII activity mainly due to over reduction of PQ, in addition no ascorbate accumulation was observed in cells. Under air + CO2 atmosphere cells accumulated excessive amounts of starch. When incubated under Ar + CO2 atmosphere cells accumulated starch as nitrogen replete cultures and no hydrogen production was observed. Hydrogen production (86 ml H2 per one l of culture) occurred under Ar + CO2 atmosphere when particular two-step illumination protocol was implicated. In oxygen producing and early oxygen consuming stage cells were illuminated under light intensity 169 μE m−2 s−1. When light was switched to 30 μE m−2 s−1, cultures quickly respired all oxygen and transient to anaerobic conditions with subsequent hydrogen production 2 h later. Actual quantum yield of C. reinhardtii cultures was measured in photobioreactor and maximal quantum efficiency of PSII of dark adapted cells together with JIP test were studied.