Outdoor cultivation of Chlamydomonas reinhardtii on different nitrogen sources

In the frame of the Photofuel project, which aims to obtain biofuels by a direct to fuel approach using photosynthetic microorganisms, wild-type strains were cultivated at the University of Florence as a growth reference for the genetically improved strains. Four wild type Chlamydomonas reinhardtii strains were tested, two with normal cell walls (CC124 and CC1690) and two wall-less mutants (CC400 and CC1883). CC1690 and CC1883 can grow using nitrate as nitrogen source, while CC124 and CC400 are unable to use nitrate. The four strains were grown under laboratory conditions using ammonium, urea and nitrate (for those able to use it). Following the good performances obtained in the laboratory trials, the four wild-type strains were cultivated outdoors on the different nitrogen sources. Batch cultures were carried out during spring and autumn in 10-L GWP® photobioreactors bubbled with an air:CO2 mixture using ammonium (the four strains), nitrate (CC1690 and CC1883), or urea (CC1883) as nitrogen source. All the strains showed a good growth and similar biomass production per unit radiation was achieved when the strains were cultivated on ammonium. Using nitrate or urea the strains showed productivities similar to those obtained on ammonium. The main problems observed were contamination and fouling. Acknowledgment: This research was funded by the European Union’s Horizon 2020 research and innovation programme under grant agreement No 640720 (Photofuel).