Figure 1.

Overview of the EPS biosynthetic pathways active in O. oeni and other LAB from fermented beverages. From top to bottom and right to left: (A) Dextran (α-glucan) and levan (β-fructan) synthesis from sucrose by external glycansucrases such as dextransucrase or levansucrase. (B) β-glucan synthesis involving UDP-glucose and the membrane spanning glycosyltransferase Gtf. (C) Heteropolysaccharide synthesis: the repeating unit is built via the involvement of priming glycosyltransferase and several other glycosyltransferases, a lipid carrier and activated substrates (UDP-oses). Then, the complete repeating unit is externalized by a flippase and is polymerized outside the cell before the release of the polymer. Gtase, glycosyltransferase.