Physicochemical Characterization of an Exopolysaccharide Produced by a Newly Isolated Weissella cibaria

A high molecular weight (3037 kDa) dextran-like polysaccharide was purified from the culture broth of a probiotic Weissella cibaria. Dry weight of the exopolysaccharides (EPS) obtained after ethanol precipitation was 6.35 g/L by using sucrose as carbon source and was further purified by phenol:chloroform:isoamyl alcohol (25:24:1) extraction and acetone precipitation to white powder with 52 % recovery. Rheological characterization revealed that it has a pseudoplastic behaviour and showed a temperature tolerance of up to 280 °C in thermogravimetric analysis. Fourier transform infrared (FTIR) spectra showed the characteristic peaks of polysaccharide such as hydroxyl group, α-pyranose, asymmetrical C–H stretching vibration of methyl group and carbonyl hydrogens of d-glucopyranose. The 1H nuclear magnetic resonance (NMR) spectrum showed resonances of hydrogen corresponding to the glucosyl residue, a repeat unit of the biopolymer. The cell viability analysis of normal L6 cells treated with the Weissella EPS showed that it is noncytotoxic even up to the 500-μg/mL level. A 0.2 % (w/v) supplementation of EPS in 2 % (w/v) wheat starch preparation could reduce the degree of syneresis up to 45 % and up to 75 % with 1 % EPS.