Production of techno-functional proteins and plant biostimulants from Nannochloropsis gaditana

Nannochloropsis gaditana is produced mainly for its lipid content and fatty acid profile. However, its protein content is comparable to or even higher than that of most conventional protein sources. In this work, the microalga N. gaditana BEA 1202B purchased from the Spanish Bank of Algae (BEA) was produced using 3.4 m3 tubular photobioreactors achieving a biomass productivity of 0.1 g L−1·day−1 and a protein content of 29.2 ± 4.5 % (d.w.). The biomass produced was used as a source of proteins; the protein recovery was optimised following a response surface methodology. Under optimal conditions, which were solubilisation at pH = 10.2 and precipitation at pH = 3.1, the protein recovery yield was 17.5 g·100 g−1. The extract exhibited a water-holding and an oil-holding capacity of 2.1 and 3.0 g g−1, respectively. The leftovers from protein extraction were assessed as plant biostimulants and demonstrated a positive effect on root development, weight gain, and chlorophyll retention. The process described in this work presents a sustainable and environmentally friendly approach to harness the potential of the microalga N. gaditana in producing high-value food proteins and plant biostimulants. The integration of this microalgal-based biorefinery concept could contribute to more sustainable agriculture and address the growing global demand for protein-rich products and plant promoters.