Isolation and characterization of the exopolysaccharide produced by Streptococcus thermophilus SFi20

This paper reports isolation, structural characterization and some physico- chemical properties in aqueous solution of the exopolysaccharide (EPS) prod uced by Streptococcus thermophilus strain SFi20. The yield of the purified EPS was found to be reproducible and close to the average value of 143 mg/l . The chemical structure, previously suggested, has been confirmed on the b asis of NMR data. Viscometric, chiro-optical and rheological measurements h ave been carried out with the aim of characterizing the conformational stat e of the polysaccharide in aqueous solution. All the data reported indicate that the EPS does not undergo a cooperative conformational transition unde r the investigated experimental conditions. Furthermore, the viscosity data and the viscoelastic behaviour suggest that the polymer is rather flexible and adopts a random coil conformation in aqueous solution. (C) 2001 Elsevi er Science B.V. All rights reserved.