403 chapter twenty-nine It’s all about the marine carbohydrates Thangapandi Marudhupandi, Radhika Rajasree Santha Ravindranath, and Dhinakarasamy Inbakandan 29.1 Introduction Marine environments offer plenty of resources and a variety of natural products for the beneit of humans; research on marine carbohydrates is constantly discov- ering their novel properties to utilize them in various industrial applications (Figure 29.1 ). A carbohydrate is a biological molecule consisting of carbon, hydrogen, and oxygen atoms with the empirical formula C n H 2n O n . In general, based on the degree of polymerization, they are classiied as mono and disaccharides, oligosaccharides, and polysaccharides (Edwards and Garcia 2009). Marine carbohydrates can be classiied based on their source of isolation (marine animals, plants, and microbes), and they are considered as an extraordinary source of chem- ical diversity for drug discovery (Laurienzo 2010). In addition, research on marine carbohydrates has increas- ingly shown the utilization of their valuable properties to various industrial applications including cosmetics, food and agriculture, pharmaceuticals, nanotechnology, biotechnology and microbiology, industrial efluent treatment, and so on. In the context of this chapter we will discuss the recent advances and applications of car- bohydrates derived from the marine sources (microbes, plants, and animals). 29.2 Chitin and chitosan polymers Chitin is a long-chain biopolymer consisting of 2-acetamido-2-deoxy-(1-4)-β-d-glucopyranose residues ( N-acetyl-d-glucosamine units) and is found in the cell walls of fungi and microorganisms, exoskeletons of arthropods, cuticle of insects, and internal shells of cephalopods (Je and Kim 2012). Interestingly, chitin iso- morphs’ occurrence was observed in fungi, arthropods, and mollusks in the form of granules, sheets, or powders (Khor 2001), whereas chitin-based scaffolds of Poriferan (marine sponge) exhibited three-dimensional networks of tube-like interconnected ibers in Aplysina aerophoba (Brunner et al. 2009). Chitin is insoluble in water because of its strong intra and intermolecular hydrogen bonding (Je and Kim 2012). In contrast, chitosan (β-(1,4)-2-amino- 2-deoxy-d-glucose), which is a cationic polymer obtained by the deacetylation of chitin, can be dissolved in water by converting it into salts with different acids on the amino group of d-glucosamine units. Moreover, partially acetylated chitosan can be dissolved in water alone (Aiba 1989). Chitin and chitosan have been widely used in vari- ous ields due to their unique features such as, low cost, eco-friendliness, and biocompatibility (Cao et al. 2014). 29.2.1 Bioadsorbent potential of chitin and chitosan Growing human population and industrialization throughout the world have been increasing environ- mental pollution. Of the pollutants, heavy metals are considered the most problematic (Kandile et al. 2015). Currently, chitin and its derivatives are receiving Contents 29.1 Introduction ................................................................................................................................................................... 403 29.2 Chitin and chitosan polymers..................................................................................................................................... 403 29.2.1 Bioadsorbent potential of chitin and chitosan.............................................................................................. 403 29.2.2 Biomedical application of chitin and chitosan ............................................................................................. 404 29.3 Carbohydrates of marine mollusks and their biological applications .................................................................. 405 29.4 Polymers of sea cucumber and their medicinal property ...................................................................................... 406 29.5 Marine microbial polysaccharides and their biological activities ......................................................................... 406 29.6 Seaweed polysaccharides and their applications ..................................................................................................... 407 29.7 Summary........................................................................................................................................................................ 409 Acknowledgment ................................................................................................................................................................... 409 References................................................................................................................................................................................ 409