Integrative genomic and structural diversity of exopolysaccharides produced by Leuconostoc isolates from sugar beet factories

Exopolysaccharides (EPS) produced by Leuconostoc species are biopolymers that disrupt sugar beet processing in factories yet hold promise for biobased applications. To elucidate the molecular diversity and biosynthetic basis of EPS formation, nine factory-derived Leuconostoc isolates were examined using integrated structural, physicochemical, and genomic analyses. The glycosyl composition showed glucose as the dominant residue, confirming that most EPS are glucans. In addition, glycosyl linkage analysis identified 6-linked glucopyranosyl backbone, with varying amounts of 3-linked, 2,6-linked and 3,6-linked branching glucopyranosyl residues. L. mesenteroides BSDF62-9 EPS contained 9.66% 6-linked fructofuranosyl residues, indicating the presence of fructans, while L. citreum BSDF5-1 showed a higher proportion of 3-linked glucopyranosyl residues (12%), due to the presence of an alternansucrase. Physicochemical characterization revealed considerable variation in EPS molecular weight, ranging from 0.62 to 21.3 MDa, indicating profound size heterogeneity. Comparative genomics revealed substantial differences in glucansucrase and fructansucrase gene content, glycoside hydrolase families GH70 and GH68. L. citreum BSDF5-1 displayed a distinct CAZyme repertoire, while most L. suionicum isolates clustered tightly, indicating a conserved enzymatic toolkit. Furthermore, L. mesenteroides BSDF62-9 and L. suionicum BSDF2-6 encoded levansucrases and were grouped separately. Taken together, this integrative analysis links genotype with structural properties of EPS.