Extracellular Polymeric Substances (EPS) Extraction

The EPS was extracted according to a modified cation exchange resin (CER) method developed by Liang et al. (2010) Cells cultivated in the DM with NaCl concentrations of 0, 30, and 50 g/L were collected at logarithmic metaphase. Then, 40 mL of each cell suspension was harvested by centrifugation (5000 rpm, 5 min, 4°C), washed three times with ultrapure water, and resuspended to its initial volume with ultrapure water. The OD₆₀₀ of different samples was adjusted to be the same, and then the suspensions were transferred into 250-mL flasks with CER (70 g/g dry cells) added. The flasks were shaken in a thermostat at 150 rpm for 1 h at 4°C and left standing for 3 min to settle the CER. Subsequently, the suspension was centrifuged for 15 min (5000 rpm, 4°C), filtered through a 0.45-μm filter, and stored at −20°C for further analysis. The dry weight of cells was measured according to Standard Methods. The concentration of polysaccharides was determined by anthrone colorimetry (Raunkjær et al., 1994). The concentration of proteins was determined according to the method described in section “Determination of Antioxidant Enzyme Activities.”