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Physicochemical characterisation of the exopolysaccharides of Streptococcus thermophilus ST ‐143
Author(s) -
Mende Susann,
Dong Tingting,
Rathemacher Anne,
Rohm Harald,
Jaros Doris
Publication year - 2014
Publication title -
international journal of food science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.831
H-Index - 96
eISSN - 1365-2621
pISSN - 0950-5423
DOI - 10.1111/ijfs.12505
Subject(s) - streptococcus thermophilus , chemistry , polysaccharide , galactose , rhamnose , food science , intrinsic viscosity , fermentation , bacteria , lactic acid , rheology , chromatography , biochemistry , lactobacillus , polymer , organic chemistry , biology , materials science , composite material , genetics
Summary Exopolysaccharides (EPS) excreted by lactic acid bacteria used in the dairy environment are either liberated into the medium (free EPS) or remain attached to the cells (capsular EPS). After batch fermentation of Streptococcus thermophilus ST‐143 at pH 6.0, three EPS fractions were isolated and purified: free EPS (EPS f ), capsular‐derived EPS (EPS cd ) and the entire total EPS (EPS total ). EPS f and EPS cd were uncharged, consisted of rhamnose, galactose, glucose and N‐glucosamine in different amounts and showed a molecular mass of 2.6 × 10 6 Da (EPS f ) and, in case of EPS cd , 7.4 × 10 3 Da and 1.4 × 10 5 Da in a ratio of 9: 1. Intrinsic viscosity of the polymers was 1.14 mL mg −1 (EPS f ), 0.06 mL mg −1 (EPS cd ) but 1.23 mL mg −1 for EPS total . The higher functionality of the entire EPS that was also observed in shear rheology measurements indicates that the presence of small capsular‐derived EPS facilitates the entanglement of the larger polymeric carbohydrates of the EPS f fraction.