A neutral exopolysaccharide produced in large amounts by
Lactobacillus fermentum TDS030603 was purified from culture supernatants and its structure determined by monosaccharide analysis, methylation analysis and
1H-NMR spectroscopy. Optimum conditions for the production of this exopolysaccharide by the above bacterial strain, when cultured using cheese whey medium or MRS broth, were also investigated. The exopolysaccharide was found to be composed of
D-galactose and
D-glucose in the molar ratio of 1:2.5 and to consist of one major as well as one minor saccharide, both of which contained a tetrasaccharide repeating unit consisting of two α and two β anomers. The major saccharide contained non-reducing glucopyranose, O-3 substituted glucopyranose, O-6 substituted galactopyranose and O-2,3 disubstituted glucopyranose. The minor saccharide consisted of non-reducing galactopyranose, O-3 substituted glucopyranose, O-6 substituted galactopyranose and O-2,3 disubstituted glucopyranose. The results suggest that these exopolysaccharides are novel saccharides that differ from previously reported products of
Lactobacillus fermentum strains. Their presence may contribute to the ropy properties of the medium.
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