Exopolysaccharides enriched in rare sugars: bacterial sources, production, and applications

Abstract

Microbial extracellular polysaccharides (EPS), produced by a wide range of bacteria, are high molecular weight biopolymers, presenting an extreme diversity in terms of chemical structure and composition. They may be used in many applications, depending on their chemical and physical properties. A rather unexplored aspect is the presence of rare sugars in the composition of some EPS. Rare sugars, such as rhamnose or fucose, may provide EPS with additional biological properties compared to those composed of more common sugar monomers. This review gives a brief overview of these specific EPS and their producing bacteria. Cultivation conditions are summarized, demonstrating their impact on the EPS composition, together with downstream processing. Finally, their use in different areas, including cosmetics, food products, pharmaceuticals, and biomedical applications, are discussed.

The role of the tyrosine kinase Wzc (Sll0923) and the phosphatase Wzb (Slr0328) in the production of extracellular polymeric substances (EPS) by Synechocystis PCC 6803

“…Polysaccharide‐based biopolymers can provide a diverse and powerful platform to deliver a wide range of biological and functional properties to the industrial toolbox. However, and despite the overwhelming diversity of polymers synthesized by microorganisms, bacterial polysaccharides are still underrepresented in the market (Roca, Alves, Freitas, & Reis, ). Most cyanobacterial strains produce extracellular polymeric substances (EPS), mainly composed of heteropolysaccharides that can remain attached to the cell surface (CPS—capsular polysaccharides) or be released into the environment (RPS—released polysaccharides) (Pereira et al, ; Rossi & De Philippis, ).…”

Rheological Behavior and Pharmaceutical Applications of Bacterial Exopolysaccharides

“…At moderate concentration of sodium hydroxide, curdlan becomes completely soluble and assumes the structure of random coils. Similar ordered conformation is also observed when curdlan is added to other non-solvents such as 2-chloroethanol, dioxan or when water is added to dimethyl sulfoxide solution (Roca et al, 2015;Tako et al, 2016;Tako, 2015).…”

“…Hydrogen bond formation between the solvent molecules and polymer-solvent molecules led to ice-like structure and finally transition from liquid to gel state. L-rhamnosyl residues in deacetylated rhamsan participate in gel formation (Roca et al, 2015;Tako et al, 2016;Tako, 2015). Curdlan with higher degree of polymerisation (approximately DP of around 200) exhibited gel formation on heating.…”

“…Increasing temperature from 298K to 348K or high salt concentration did not affect the diutan gum viscosity. Resistance to thermal and salt effects is attributed to double helical structure, location and nature of side chains (Roca et al, 2015;BeMiller and Whistler, 2012;Sonebi, 2006;Xu et al, 2015;Fink, 2003).…”

“…Bacterial polysaccharides are currently being used as adjuvants in skin care regimens, preferably because of their positive effects on skin hydration and also their capability in stimulating cell renewal and biosynthesis of several skin constituents. Marine bacterial EPS have been investigated for their potential to be used as nanopatterned scaffolds, where attachment of specific ligands can promote cellular function and differentiation of embryonic stem cells (Roca et al, 2015;Lindstrom et al, 2012;Baruah et al, 2016;Venugopal, 2011;Camargo et al, 2012;Moscovici, 2011;Tako et al, 2016).…”