Characterization of highly branched dextran produced by Leuconostoc citreum B-2 from pineapple fermented product.

A strain Leuconostoc citreum B-2 was isolated from homemade fermentation product of pineapple and its polysaccharide yield was 28.3g/L after cultivating the strain in Man-Rogosa-Sharpe (MRS) medium with 75g/L sucrose. The exopolysaccharide (EPS) was characterized by gas chromatography (GC), Fourier-transform infrared (FT-IR) spectra, high-performance size-exclusion chromatography (HPSEC), nuclear magnetic resonance (NMR) spectroscopy and scanning electron microscope (SEM) analysis in present study. The monosaccharide composition of EPS was glucose and molecular weight was 3.77×106Da. FT-IR and NMR spectra revealed that the B-2 EPS was composed of 75% α-(1→6) linked d-glucopyranose units existing in the main chain with 19% α-(1→3) branching and only a few α-(1→2) branching. The SEM of the dried EPS appeared irregular sheets with glittering surface and compact structure. Water solubility index and water holding capacity of B-2 EPS were 80% and 450%, respectively. All the mentioned characteristics suggested that the EPS has a potential application in the food, cosmetic and pharmaceuticals industry.