Structure-Function Relationship of a Gellan Family of Polysaccharide, S-198 Gum, Produced by Alcaligenes ATCC31853

Abstract

The structure-function relationship of a gellan family of polysaccharides, S-198 gum produced by Alcaligenes ATCC31853 was investigated in terms of rheological aspects. The flow curves of S-198 gum showed plastic behavior above 0.3%. Gelation did not occur in S-198 gum solution at low temperature (0˚C), even at 0.8%. Both the viscosity and the elastic modulus remained constant with increasing temperature up to 80˚C. The elastic modulus decreased a little with the addition of CaCl2 (6.8 mM), but then once again remained constant up to 80˚C. The highest elastic modulus was observed for deacylated gellan gum with the addition of CaCl 2 and increased slightly with increasing temperature up to 80˚C, which was considered to be a transition temperature, after which it decreased rapidly. The elastic modulus of S-198 gum in the presence of urea (4.0 M) was lower than that in aqueous solution at low temperature (0˚C), but remained constant with increasing temperature up to 80˚C. The intramolecular associations, (hydrogen bonding and van der Waals forces of attraction), of S-198 gum molecules in aqueous solutions were proposed. The gellan family of polysaccharides, S-198, S-88, S-657, rhamsan, welan and gellan gum, provided a good opportunity to investigate the structure-function relationship for polysaccharides.

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).…”

“…Study of solution behavior of microbial polysaccharides is essential for exploring their uses and commercial applications in various industries. Rheological characterization and analysis helps in elucidating the structure-function relationship of the compounds at molecular level in aqueous solvents (Tako et al, 2016).…”

“…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.…”

“…No change in viscosity and elastic modulus could be observed even if temperature was increased to 80°C. In presence of urea (4.0M), the elastic modulus of S-198 was found to be less than that of its aqueous solution (Tako et al, 2016). It can be developed in manufacture of water-based lubricants (Bhatia, 2016).…”

“…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).…”