Characterization of cell growth and photobiological H2 production of Chlamydomonas reinhardtii in ASSF industry wastewater

Abstract Photobiological H 2 production in microalgae is a promising approach for the development of alternative clean and renewable energy. As a unicellular green alga, Chlamydomonas reinhardtii is regarded as an ideal candidate for sustainable photo-H 2 production. However, growth and photo-H 2 producing are still expensive and energy extensive. Wastewater has been suggested as an economical resource for microalgae growth and biofuels production. In this study, we characterized the cell growth and photo-H 2 production of C. reinhardtii CC503 cultured in waste water from pressing process of fermented sweet sorghum stalks during Advanced Solid State Fermentation (ASSF). The maximal cells concentration reached 8.9 × 10 6  cells/mL in ASSF wastewater medium (AWM) with the fastest growth rate of 0.19 × 10 6  cells/h, compared to 18.2 × 10 6  cells/mL and 0.36 × 10 6  cells/h in TAP medium and to 1.3 × 10 6  cells/mL and 0.02 × 10 6  cells/h in BGII medium respectively. The optimized concentration of wastewater for algae cells growth was determined to be 13.3% (7.5 folds dilution), under which, surprisingly the photosynthetic H 2 evolution was increased by more than 700% compared to the cells grown in TAP medium. This system appears to be a good strategy for the development of an economical microalgal photobiological H 2 production scheme. Finally, the possible mechanism for such an H 2 enhancement was identified as the reduction of PSII activity in AWM grown cells.