Purification and Structure Study on Exopolysaccharides Produced by Lactobacillus paracasei KL1-Liu from Tibetan Kefir
To investigate the pure conditions of exopolysaccharides produced by Lactobacillus paracasei KL1-Liu from Tibetan Kefir, and to analyse the structure, we used Multi-level single-factor test to purify EPS by Sepharose CL-6B. And the purity of EPS was detected by UV scan and high performance liquid chromatogram (HPLC). EPS molecular weight and monosaccharide composition were determined by HPLC. Results: Adoption phosphate buffer gradient elution 0.02-0.10 mol/L, the velocity 0.25 mL/min, the sample concentration 1.0 mg/mL, the sample capacity 1.0 mL. Under this purification conditions, components EPSa and EPSb were obtained. The purities of EPSa and EPSb were 82.82% and 91.74% respectively, which were 1.4 and 1.5 times of the pre-purification. Purity Test results showed that EPSa and EPSb polysaccharide were single components, basically no nucleic acid and protein in them. Structural analysis revealed that the molecular weight of EPSa and EPSb were 4.60×104 Da and 2.12×104 Da detected by HPLC. EPSa monosaccharide components were glucose and rhamnose, and the molar ratio was 1:0.68. EPSb were composed of glucose, xylose and rhamnose, and the molar ratio was 1:0.77:0.69.