Carrageenans and carrageenases: versatile polysaccharides and promising marine enzymes

Abstract

Carrageenans are sulfated polysaccharides isolated from marine red algae that share a common backbone of D-galactose alternately linked by α(1,3) and β(1,4) glycosidic linkages. They are classified based on the number and the position of the sulfate ester groups and the occurrence of a 3,6 anhydro-ring in the α-linked galactose. Accordingly the three most commercially exploited carrageenans are κ-, ι-, and λ-carrageenans. Because of their biocompatibility, exceptional physicochemical features and emulsifying, thickening, gelling and stabilizing abilities, they have found several industrial application, especially in food, pharmaceutical and cosmetic industries. Moreover, carrageenans can be degraded into lower molecular weight oligosaccharides, which have been reported to have promising pharmacological properties and potential therapeutic applications. Enzymes which degrade carrageenans are called carrageenases and are produced only by marine bacterial species. These enzymes all are endohydrolases that hydrolyze the internal β 1,4 linkages in carrageenans and produce a series of homologous even-numbered oligosaccharides with various biological and physiological activities including anti-tumor, anti-inflammation, anti-viral, anti-coagulation, etc. Carrageenase enzymes have also other applications related to the biomedical field, bioethanol production, prevention of red algal bloom, obtaining algal protoplasts, etc. In the first part of this review, general information regarding structure, physicochemical properties, biological activities and potential applications of carrageenans is summarized. The second part deals with research and development works on some aspects of carrageenase enzymes like the source, characterization, the kinetics and biochemical properties and their applications in various industries.