Bioactivity and applications of polysaccharides from marine microalgae

Marine microorganisms have been under research for the last decades, as sources of different biocompounds, each with various applications. Polysaccharides (PSs) are among these chemicals being produced and released by marine microalgae. These are very heterogeneous, including cyanobacteria and eukaryotic microalgae from several divisions/phyla, each of which with different characteristics. The PSs, sulfated or not, that they produce have already proved to be promising agents in various fields, such as food, feed, pharmaceutical, and biomedical. They can also be applied in wastewater and/or soil treatment and in some engineering areas, as naval engineering. After a brief introduction on the general types of biopolymers produced by marine microalgae and cyanobacteria, this chapter starts by presenting the species of these microorganisms and the types of PSs they produce, as well as the respective chemical composition; goes into the production of PSs and the effect of specific compounds; and focuses on the physicochemical properties of these PSs and their composition and structure, approaching the rheological properties relevant for their functions and behavior. The bioactivity of PSs and their applications are, next, presented, including therapeutic applications based on their antiviral and antibacterial activities, antioxidant properties, anti-inflammatory and immunomodulatory characteristics, antitumoral activity, and antilipidemic and antiglycemic properties, among others. The potential use of PSs from marine microalgae as it is or incorporated in health foods is also considered. The mechanisms behind their antiviral and antibacterial activities are explained. Toxicological and safety issues are also disclosed, and there is a brief mention of the bioavailability of PSs from microalgae. The chapter ends by listing some preclinical studies with this type of polymers.