Modeling the bicarbonate uptake in Arthrospira maxima as a function of pH: batch and continuous experiments.

Microalgae industrial cultivation is still currently limited by high costs related to biomass production and harvesting. Among the others, the supply of CO2 by bubbling is one of the major costs related to CO2 insufflation in photobioreactors, due to the low solubility of CO2 and the slow uptake by microalgae, causing a consistent loss of the gas in the atmosphere. Hence, research efforts have been focused on the investigation of suitable alternative inorganic carbon sources. Some microalgae and cyanobacteria, called alkali halophilic species, are able to exploit bicarbonate ions for carbon fixation with efficiency comparable to that of CO2. Spirulina, one of the most cultivated microalgal species for industrial purposes, is able to use bicarbonate, and it was chosen as a model organism to describe the effect of bicarbonate on growth, accounting for the effect of pH on carbonate speciation. In this master thesis, Arthrospira maxima has been cultivated in continuous photobioreactors under different bicarbonate concentration, pH and under enriched CO2 bubbling. Experimental data were subsequently applied to implement a kinetic model for a numerical description of such a phenomenon.