Bioactive polysaccharides from microalgae

Abstract Polysaccharides are macromolecules based on glycosidically linked combinations of up to 40 different monosaccharides, sometimes substituted by nonsugar groups such as alcohols, organic acids, or sulfates. Those from animals, terrestrial plants, marine macroalgae, and nonphotosynthetic microorganisms are widely exploited by industry as biological agents in various fields including agronomy, medicine, cosmetic, nutrition, and others. Microalgae and cyanobacteria are eukaryotic and prokaryotic unicellular photosynthetic organisms with a vast phylogenetic diversity that are known to produce large quantities of extracellular polysaccharides. Except for those from Porphyridium strains, polysaccharides from microalgae have been poorly investigated in the past for their biological activities, as the culture of these microorganisms was frequently a challenge. However, the recent development of technologies for production (photobioreactors) and treatment (downstream processes) of microalgal biomass give researchers access to original biopolymers with unique structures and compositions, making them very attractive for bioprospecting. This chapter aims to describe the state of the art in the field of bioactive polysaccharides from microalgae.