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Evaluation of maintenance energy requirements in the cultivation of Scenedesmus obliquus: effect of light intensity and regime

Sforza, Eleonora, Urbani, Silvia, Bertucco, Alberto
Journal of applied phycology 2015 v.27 no.4 pp. 1453-1462
Scenedesmus obliquus, cell growth, energy balance, energy requirements, growth models, irradiation, latitude, light intensity, lipid content, microalgae, photoinhibition
Most relevant factors influencing microalgae growth are light availability and utilization. In view of maximizing the photosynthetic efficiency of a photobioreactor, the evaluation of maintenance energy is essential to understand the energy requirement for cell growth and it is also a key parameter of most mathematical growth models. In this work, steady-state continuous experiments were carried out in a flat-bed photobioreactor, at different light intensities and irradiation regimes, measuring growth rate, productivity, lipid content, and photosynthetic efficiency of Scenedesmus obliquus at non-limiting N and P condition. Energy balance was applied to measure the maintenance term as a function of irradiation, under both continuous and simulated seasonal irradiation at middle latitudes. The energy requirement for maintenance was found to be greater under high irradiances as a result of the photoinhibition effect. Experimental data were correlated following a substrate inhibition model. The nutrient uptakes were found to depend on growth rate and light intensity and to be affected by the maintenance requirement.