Annual outdoor cultivation of the diatom Thalassiosira weissflogii: productivity, limits and perspectives

Diatoms are a promising source of renewable biomass for production of energy and functional ingredients and food products. The eurythermal diatom Thalassiosira weissflogii shows great resistance and robustness, and can be considered a suitable candidate for outdoor cultivation. In this study we investigated the resilience of one strain of this species during one-year outdoor experimentation in inclined tubular photobioreator with a working volume of 40 L. Cells of T. weissflogii overcome temperature and irradiance fluctuations by adapting their growth rate at the different environmental conditions. Calculation of areal biomass productivity based on 30 cultures along the year showed a median value of 3.83 g m day with maximal values of biomass (6.8 g m day) and lipids (1.2 g m day) reached in February and July, respectively. We observed a decline in biomass productivity with temperature increase, whereas lipid content (10-20% of dry biomass) was not significantly affected by the environmental conditions as far as a high concentration of nutrients was maintained. The outdoor experimentation successfully proved one year-round production of biomass from a single diatom species in closed photobioreactor, making T. weissflogii a suitable candidate for guaranteeing stable annual productive cycles in outdoor plant.