Microalgae biomass and lipid production potential, and mechanical stress compliance

In this work we report an experimental investigation concerning growth rates in small scale (volumes ranging from a few mL to 75 L) of freshwater and marine microalgae of the following species: Chlorella vulgaris, Nannochloropsis sp., Tetraselmis suecica, Botry- ococcus braunii and Scenedesmus dimorphus, in bubble column, draft tube, flat and wavy bottom thin layer photobioreactors. Investi- gated issues were: volume scale-up, presence of an external carbon source, and growth rate under an augmented CO2 concentration in the gas feed. Additionally, an investigation was carried out on the stress compliance of said microalgae to mechanical (shear) stress involved in pumping. Beyond confirming the key role of carbon (either CO2 or organic), nutrient and light supply in biomass and lipid productivity, our results point out the significant difference in mechanical stress sensitivity of the various strains under test.