Microwave-assisted extraction of polysaccharides from Arthrospira (Spirulina) platensis using the concept of green chemistry

The microalgae Spirulina (Arthrospira) platensis has captured attention in the biotechnology field, containing in its composition mainly proteins, carbohydrates, lipids and pigments that are compounds of interest in food, pharmaceutical and cosmetic industries. Branched polysaccharides are the most important among the polymeric components since this microalga and its extraction usually involve high costs with energy and toxic solvents. In this context, the aim of this work was to evaluate the efficiency of obtaining polysaccharides from microalgae A. platensis by a microwave-assisted process, using water as a solvent, following the principles of green chemistry, mainly solvent and energy saving. Different parameters were evaluated: extraction time (1 min of extraction in the microwave was fixed and a contact time of the microalgae with water after the exposure to the microwaves was studied - 0, 20, 40 and 60 min), microwave power (186, 310, 434, 558 and 620 W) and the biomass:solvent ratio (1:15, 1:25, 1:30, 1:35 and 1:45 w·v−1). The optimum extraction condition was obtained using only a treatment in the biomass for 20 min, to remove pigments and lipids before the extraction that was conducted in a microwave power of 434 W for 1 min, biomass:solvent ratio 1:30 w·v−1 and no further contact, obtaining 127 ± 5 mg of carbohydrate/g of biomass. Purified polysaccharide was composed of major glucose and rhamnose, a biomolecule very important given that it has wide applications in medical and food industries.