The response surface optimization of exopolysaccharide produced by Y3 and its partial characterization.

Response surface methodology (RSM) was used to optimize the conditions of exopolysaccharides (EPSs) by Y3. The results indicated that the yield of EPS reached 4.52 ± 0.14 g/L with 10.30% (w/v) sucrose, 0.64% (w/v) yeast extract, liquid volume 141.5 mL, which was 2.40 times the original EPS yield. Y3 EPS contained 83.65 ± 0.16% of total sugars, 15.27 ± 0.26% of uronic acid, 0.78 ± 0.02% of protein and 0.30 ± 0.12% of sulfuric acid groups. Y3 EPS maintained a relatively low viscosity, with intrinsic viscosities of 306.58 mL/g (25 °C) and 200.91 mL/g (35 °C), respectively. The EPS had high water solubility index (WSI), high water holding capacity (WHC) and good emulsifying ability (EA). Meanwhile, the EPS could absorb metal ions such as Cu, Fe and Zn. In addition, Y3 EPS exhibited good antioxidant properties and coagulated skim milk with a concentration-dependent manner. These results indicated that Y3 EPS had applicable prospects in medicine, food, especially the dairy industry.