Structure of the levan elaborated by Streptococcus salivarius strain 51: an application of chemical-ionisation mass-spectrometry.

The polysaccharide elaborated by Streptococcus salivarius strain 51 contains beta-D-fructofuranose residues linked through positions 2 and 6, as well as 1, 2, and 6. The approximate numbers of terminal, non-reducing D-fructofuranose residues and those linked through positions 2 and 6, and through 1, 2, and 6 in the average repeating-unit are 1, 7, and 1, respectively. The branches through the beta-(2 leads to 1)-linkage contain up to at least four D-fructofuranose residues. Chemical-ionisation mass-spectrometry aids the assignment of structures to O-acetyl-O-methylalditols obtained in methylation analysis.