Bioproduction, purification, and application of polysialic acid.

Polysialic acid (PSA) is a negatively charged linear homopolymer linked by N-acetylneuraminic acid and widely present in vertebrates and some pathogens. PSA, commonly found on cell surfaces as glycoproteins and glycolipids, plays important roles in intercellular adhesion, cell migration, and formation and remodeling of the neural system by regulating the adhesive property of nerve cell adhesion molecules. PSA with a molecular weight that can reach as high as 260 kDa also belongs to the group II capsule polysaccharide of neonatal meningitis-causing Escherichia coli K1. To date, much effort has been devoted to developing the biotechnological production of PSA. As a non-glycosaminoglycan, PSA is a non-immunogenic and biodegradable polysaccharide that can be used as a biomaterial in protein polysialylation, tissue engineering, and drug delivery. PSA can also combine with other macromolecules to form multifunctional composites. In this mini-review, the production, purification, and application of PSA are summarized to provide a basis for further PSA applications.