Interacting effect of heliothermic factors on the growth rate of 3 Scenedesmus species

Within the framework of a microalgae screening program, three species of Scenedesmus (S. abundans, S. dimorphus and S. ecornis) were studied in batches and in non-nutrient limited conditions. For each species, the effects of light intensity (from 30 to 560 mu mole quanta. m(-2). s(-1)), temperature (from 10 to 35 degreesC) and daylength on the growth rate have been measured and mathematically formulated. The results obtained show that the three microalgae are mesophilic strains, with an optimal growth temperature of 30 degreesC for S. ecornis and 35 degreesC for the two other species. Interaction between temperature and light intensity on growth has been demonstrated for the three species. In the same way, a positive effect of daylength on the growth rates of Scenedesmus spp. has been recorded. Under optimal conditions, the maximum growth rates are respectively of 2,1 d(-1) for S. ecornis, 1,95 d(-1) for S. abundans and 1,5 d(-1) for S. dimorphus. Moreover, the effects of heliothermic factors on the growth rate of the three species have been reproduced satisfactorily by using three mathematical models. This study indicates that the three species of Scenedesmus are adapted to the climatic conditions of the Marrakech area. So, for application purposes, the large-scale culture of these species could be possible.