Synergistic effect of UV radiation and nutrient limitation on Chlorella fusca (Chlorophyta) cultures grown in outdoor cylindrical photobioreactors

18 páginas.- Irene Malpartida... et al.

This study assessed the interactive effects of UVR and nutrient depletion on Chlorella fusca cultures on the production and accumulation of particular biomolecules. To accomplish this, algae were grown for 5 d in outdoor thin-layer cascade cultivators under 3 nutrient treatments (full nutrients, -N and -S) and then transferred to outdoor cylindrical photobioreactors for another 5 d. Cultures were then exposed to full solar radiation (PAB) and decreased UVR. During the last 5 d, bio-optical properties, photosynthetic activity, pigments, biochemical composition and oxidative stress were assessed. Initially, nutrient depletion caused changes in productivity and cell number in a manner that affected biochemical composition. After 3 d, the percentage of lipids in the cultures under N deprivation reached values appropriate for being used as feed or food additives or for energy applications (35% of lipid content), regardless of the light conditions. A longer exposure (5 d) resulted in interactive effects of light and nutrient conditions. Specifically, PAB increased lipid content in all cases (1.3- to 2.3-fold), but particularly under S deprivation. Longer exposure to PAB also increased oxidative stress in UVR and nutrient-limited treatments (-N and -S). These results showed that the benefits expected from nutrient depletion (increase in biomolecule content e.g. lipids, carbohydrates and pigments) were modulated by the negative effects of algal UVR acclimation costs.

We acknowledge the financial and technical (use of PAM fluorometers) support by Walz to the GAP 9 Workshop ‘Influence of the pulsed-supply of nitrogen on primary productivity in phytoplankton and marine macrophytes: an experimental approach’. We also thank Redox, the University of Málaga, Ministry of Economy and Competitiveness of Spanish Government (Acción Complementaria CTM2011-15659-E) and the Spanish Institute of Oceanography. The participation of E.N. was also supported by the Spanish Ministry of Economy and Competitiveness of Spanish Government (Ref. BFU2010-22053).

Peer reviewed