LED light tailoring in a planar photobioreactor for optimization of microalgae growth.

Microalgae are well known for their potential in producing valuable substances for nutraceutical and pharmaceutical industries, as well as a source of biofuel. Currently, the use of the photosynthetic capacity of microalgae is a new alternative for carbon dioxide bio-fixation. Therefore, the purpose of this work is to identify the best microalgae growth conditions, using an experimental planar photobioreactor (PBR) and LEDs with variable intensities as a light source. Two different illumination intensity levels were used during the experiment: 33 and 57 µE of PPFD (photosynthetically active radiation). A series of PBR variables such as temperature, pH, CO2 and oxygen levels, were monitored in real time. Optical density (OD) and dry weight were periodically evaluated in order to estimate the concentration of biomass in the culture. Microalgae growth under specific light conditions was evaluated and a strong correlation between the two was observed. Namely, given the biomass growth curve as a function of time, it is possible to identify a proportional relationship which relates light intensity to biomass density. Overall, the innovative approach of this work allowed to 1) successfully cultivate Scenedesmus obliquus in a closed photobioreactor under low photon flow; 2) establish a correlation between biomass concentration and LED intensity for this specific microalgae strain which can be used in future experiments in order to finely tune light intensity to the desired biomass density.