Influence of culture conditions on the productivity and lutein content of the new strain Scenedesmus almeriensis

This paper presents the first characterization data of the lutein-rich microalgae Scenedesmus almeriensis, a new strain isolated within a farmer's greenhouse. The main objective is to determine the appropriate conditions for the culture of this microalgae and any factors that might enhance its lutein content. The maximum growth rate was determined first in batch cultures, resulting an initial estimate of 0.63 1/day. Then, the influence of environmental culture conditions such as temperature, pH, culture medium, external irradiance, and salinity were assessed operating in continuous mode at a dilution rate half the maximum previously determined. Finally, the possible interactions between irradiance and temperature were studied by means of a surface response analysis and the optimal conditions of irradiance and temperature were tested in a separate experiment. The results show that the medium proposed by [Mann JE, Myers J. On pigments, growth and photosynthesis of Phaeodactylum tricornutum. J Phycol 1968;4:349–55] was adequate for the growth of this strain and that increasing the initial nutrient concentration did not improve the performance of the cultures. Measurements of chlorophylls fluorescence showed that there was no photoinhibition even under the highest external irradiances tested (1700 μE/m2 s). The optimal pH was found to be 8.0. With regard to the temperature, this strain grew well in the range of 30–40 °C, being clearly distressed in the experiments carried out at 48 °C. Low to medium salinities, between 0 and 5 gNaCl/L, were appropriate to promote growth rate. A response surface analysis predicted a maximum biomass productivity of 0.7 g/L day at 33 °C and 1700 μE/m2 s, and a maximum lutein content of 0.54% d. wt. at 44 °C and 1233 μE/m2 s. The experimental confirmation of the optimal conditions for lutein resulted in a biomass productivity of 0.73 g/L day with a lutein content of 0.53% d. wt., and therefore a lutein productivity of 3.8 mg/L day. The biomass of S. almeriensis is a rich source of lutein, about ten fold richer than the commercial source of this compound, Marigold flowers. The high lutein content and growth rate and the capacity to endure harsh environmental conditions make S. almeriensis a promising source of lutein.