Structural Characterization of Glucan Produced by Lactobacillus sake L-7 from Sausage

Abstract

A linear glucan was produced by Lactobacillus sake L-7 isolated from homemade sausage. Cultivation of the strain in Man–Rogosa–Sharpe (MRS) medium containing 50 g/L sucrose yielded 5.3 g/L of purified exopolysaccharide (EPS). The EPS was characterized by gas chromatography (GC), Fourier-transform infrared (FT-IR) spectroscopy, high-performance size-exclusion chromatography (HPSEC), nuclear magnetic resonance (NMR) spectroscopy, and scanning electron microscopy (SEM). The monosaccharide composition of the EPS was glucose, and its molecular weight was 1 × 107 Da. The FT-IR and NMR spectra revealed that the L-7 EPS was a linear glucan with α-(1 → 6) glucosidic bonds. SEM images of the dried EPS revealed a hollow tubular structure. The water solubility index and water holding capacity of L-7 EPS were 96 and 272%, respectively. The results of hydrolysis indicated that L-7 EPS was not susceptible to hydrolysis by physiological barriers and can be used as a soluble dietary fiber with health benefits. All these characteristics suggest that L-7 EPS might have potential applications in the food, cosmetic, and pharmaceutical industries.