2.4. Purification by Ion Exchange Chromatography of Exopolysaccharides (EPS)

A cellulose DE-52 column (Ø26 mm × 0.3 m, 50μm) (newprobe, Beijing, China) equilibrated with distilled water was used to fractionate the DEPS solution in distilled water. The DEPS was prepared as a 10 mg mL⁻¹ polysaccharide solution that was added to the ion exchange column wall after it had been pre-equilibrated with distilled water. The column was eluted with distilled water, followed by 0.4, 0.8, and 2.0 mol L⁻¹ NaCl solution at 1 mL min⁻¹ in order. The elution volume of each phase was 100, 200, 200, and 100 mL, respectively. In each tube, 10 mL aliquots were collected, and the carbohydrate content was determined using the phenol sulfuric acid method [21].