The rough crystal of exopolysaccharide produced by Enterococcus durans, a strain of lactic acid bacteria screened from the intestine of a cock in our laboratory, was purified by CM-cellulose column chromatography, DEAE-Sephadex A-25 ionexchange and Sephadex G-100 gel chromatography to give EPS-Ⅰ. The EPS-Ⅰ was eluted as a single peak in HPLC analysis, indicating the homogeneity of EPS-Ⅰ and free from low-molecular-weight polysaccharides. The molecular weight of the EPS-Ⅰ was determined as 42 000 by the light scattering method. The result of its elemental analysis was C 41.08% and H 7.23% without the elements of N, P and S. Monosaccharide analysis showed that it was composed of Glc and Man in a molar ratio of 4∶1. Sugar composition analysis, methylation analysis and 1H and 13C NMR spectroscopy revealed that the EPS-Ⅰ was composed of pentasaccharide repeating units. The sequence of sugar residues was determined by using two-dimensional NMR, including heteronuclear multiple-bond correlation(HMBC) and nuclear overhauser effect spectroscopy(NOESY). The structure of the pentasaccharide repeating unit of EPS-Ⅰ was given, a new excellular polysaccharide from lactic acid bacterium compared with other EPSs was reported.
