Structure and properties of the exopolysaccharide produced by Streptococcus macedonicus Sc136

Streptococcus macedonicus is a Gram positive lactic acid bacterium that is part of the starter flora present in Greek sheep and goat cheeses. The S. m acedonicus Sc136 strain produces a high-molecular-mass, highly texturizing exopolysaccharide composed of D-glucose, D-galactose, and N-acetyl-D-glucos amine in the molar ratio of 3:2:1. The structure of the exopolysaccharide p roduced by S. macedonicus Sc136 was determined by chemical analysis, mass s pectrometry, and nuclear magnetic resonance spectroscopy. The repeating uni t was shown to be: [GRAPHICS] The polysaccharide sidechain beta -D-Galf-(1-->6)-beta -D-Glcp-(1-->6)-beta -D-GlcpNAc is a key factor in the highly texturizing properties of the S.m acedonicus Sc136 exopolysaccharide, Finally, the trisaccharide sequence bet a -D-GlcpNAc-(1-->3)-beta -D-Galp-(1-->4)-beta -D-Glcp corresponds to the i nternal backbone of the lacto-N-tetraose and lacto-N-neotetraose units, whi ch serve as a structural basis for the large majority of human milk oligosa ccharides, an additional property offering an important potential for the d evelopment of improved infant nutrition products.