Luxury uptake of phosphorus in Nannochloropsis salina: Effect of P concentration and light on P uptake in batch and continuous cultures

Nannochloropsis is commonly recognized as a valuable biomass source for the production of both biofuels and high value nutraceuticals compounds. Phosphorus is one of the main nutrients affecting microalgal growth and composition. In this work, the effect of using higher P concentrations in cultivation of Nannochloropsis salina was studied showing an increase of the phosphate uptake rate related with the higher P availability in the medium. This enhanced uptake was preferentially stored in the cells rather than being used for growth, indicating the activation of a luxury uptake phenomenon. The intracellular P storage in N. salina was measured and the presence of polyphosphate granules was detected. The kinetic of accumulation and consumption of internal phosphorus was quantified in batch cultures, as a function of P concentration and light intensity. Finally, the effect of P, also in combination with different light supply rates was analyzed in continuous steady-state experiments, showing that operating in this mode strongly influences not only the biomass productivity, but also the nutrient uptake.