Photoautotrophic hydrogen production by nitrogen-deprived Chlamydomonas reinhardtii cultures

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 H-2 per one 1 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 mu E M-2 s(-1). When light was switched to 30 mu E 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 photo-bioreactor and maximal quantum efficiency of PSII of dark adapted cells together with JIP test were studied. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study demonstrates the possibility of phototrophic hydrogen production in C. reinhardtii under N-deprived conditions, indicating a potential strategy for sustainable hydrogen production. The implementation of a two-step illumination protocol can significantly enhance hydrogen production, and the relationship between PSII activity and hydrogen production in C. reinhardtii was investigated.