Structural analysis by 13C-nuclear magnetic resonance spectroscopy of glucans elaborated by gum-producing bacteria isolated from palm wine

The linkages of the glucans produced by palm wine bacteria in sterile palm sap and in sucrose broth were determined using 13C nmr spectroscopy. The glucose units appeared to be linked α(-1–6) in the main chain. Therefore, the glucans are likely to be dextrans. There were branch linkages, and these differed between the genera of lactic acid bacteria (LAB) and even within one genus. However, branching by α(-1–3) was a feature common to all the dextrans of the three organisms employed. The dextran of Leuconostoc dextranicum appeared to branch mainly by α(1–3) linkages with minor α(1–4) ones; that of Leconostoc mesenteroides, mainly by α(-1–2) and that of the Lactobacillus spp. by only α(1–3) linkages. The organisms were found to elaborate more highly branched dextrans in sucrose broth than in palm sap probably due to nutrient differences, but the branch linkage types remained the same. The degree of branching did not appear to affect the viscosity. It was concluded that gums produced by palm wine glucan-producers were dextrans and that these different dextran-producing bacteria, in palm wine, each produced its own peculiar type of dextran in the beverage.