Extraction and fractionation of polysaccharides and B-phycoerythrin from the microalga Porphyridium cruentum by membrane technology

Porphyridium species are exploited for the production of exopolysaccharides and B-phycoerythrin, two high-value compounds. Extraction and purification of these two substances often involve antagonistic processes (precipitation with ethanol, isoelectric precipitation, aqueous two-phase systems, chromatography and ultrafiltration) that work better for one than for the other. We developed a two-step membrane process using polyethersulfone flat membranes with a filtration surface of 0.1 m2 to recover both B-phycoerythrin and soluble polysaccharides from Porphyridium biomass with high polysaccharide content. A first ultrafiltration at 300,000 yielded high molecular weight polysaccharides. The resulting 300,000 permeate was then run through a second, 10,000 membrane to recover BPE. This procedure enabled us to extract 48% of B-phycoerythrin free of polysaccharide with a purity index of 2.3.