A Zero-Waste Approach for the Production and Use of Arthrospira Platensis As a Protein Source in Foods and As a Plant Biostimulant in Agriculture

Food production will have to increase significantly to meet the nutritional needs of the global population. There is also an urgent need to increase the sustainability of food production. Microalgae are a potential sustainable alternative to conventional protein sources and they can also be used in other industries such as agriculture or aquaculture. In this work, the cyanobacterium Arthrospira platensis was produced in Almeria (Spain) in a pilot-scale reactor (80 m 2 ). The biomass produced was used as a protein source and a plant biostimulant following a biorefinery approach. Biomass productivity reached 5.6 g m −2 day −1 . The biomass was rich in proteins (67.8 g (100 g) −1 ) and pigments, namely chlorophyll (7.6 mg (100 g) −1 ) and phycocyanin (134.2 mg (100 g) −1 ). An isoelectric solubilisation/precipitation method assisted by ultrasound led to the recovery of a protein extract with a protein content of 91.3 g (100 g) −1 . The protein isolate was evaluated as a source of essential amino acids in tagliatelle, leading to an increase in the content of histidine, leucine, lysine, methionine, phenylalanine, threonine, and valine of 36.3, 75.2, 26.3, 30.0, 45.7, 57.8, and 70.0%, respectively. The protein content also increased from 9.6 to 13.9 g (100 g) −1 when the protein isolate was incorporated at a flour substitution level of 4%. The leftovers from the protein extraction were evaluated as plant biostimulants, for which auxin- and cytokinin-like effects were observed. Root development was especially promoted. The results demonstrated the feasibility of producing Spirulina during the winter in Europe and the potential simultaneous use of the biomass as a food ingredient and as a plant biostimulant.