Abstract
One of the main limitations for achieving an optimal growth in photosynthetic cultures grown in photobioreactors is the CO2 availability in the aqueous phase. The mass-transfer phenomenon leading to the absorption of this gas in the water is relatively slow compared with the CO2 fixation capabilities of high density microalgae cultures and so it can be a limiting step for cell growth, especially if just air is the carbon source. Additionally, alkaliphilic strains such as the cyanobacterium Synechocystis tolerate high pH environments, which can reduce the risk of biological contamination in the bioreactor. Indeed, this strain is capable of increasing the pH of the medium upto 11 units when no buffering system is used. However, alkaline media drop the HCO3- concentration available for the cells, thus reducing their potential growth. So it is useful to assess the impact of high pH media in the carbon fixation to evaluate its effect on the culture evolution.
A mathematical model is here presented that links the CO2 inlet in the photobioreactor with the carbon fixation mechanisms of Synechocystis. The influence of the temperature, the pH and the CO2 inlet concentration on the culture growth and hydrogen production will be assessed.
