Isolation and characterization of dextran produced by Leuconostoc citreum NM105 from manchurian sauerkraut

A water-soluble exopolysaccharide (EPS) was produced by Leuconostoc ctireum NM105 from homemade manchurian sauerkraut. After culturing the strain in Man-Rogosa-Sharpe medium containing 5% sucrose at 25 °C for 48 h, the EPS was purified and a yield of 23.5 g/L was achieved. The EPS consisted exclusively of glucose and the weight-average molecular weight was 1.01 × 108 Da. The structural characterization of the purified EPS determined by FT-IR, 1H, 13C and two-dimensional NMR spectroscopy demonstrated that the glucan contained α-(1 → 6)-linked d-glucopyranose units, 2,6-linked d-glucopyranose units and terminal α-d-glucopyranose units at a ratio of 1:1:1. The microstructure of the dried dextran appeared a sheet-like smooth glittering and highly branched surface. The NM105 dextran showed high water solubility and excellent water retention. All the results suggested that the highly α-(1 → 2) branched dextran might have the potential to serve as valuable polymers applied in foods, cosmetics and other fields.