Purification, characterization and antioxidant activity of the exopolysaccharide from Weissella cibaria SJ14 isolated from Sichuan paocai

In the present study, an exopolysaccharide (EPS)-producing strain SJ14 isolated from Sichuan paocai was identified as Weissella cibaria, with a typical ropy phenotype. W. cibaria SJ14 possessed good capabilities of acid production, salt tolerance, and nitrite depletion. The crude polysaccharides were obtained from the culture supernatant of strain SJ14 and further fractionated by DEAE-Sepharose Fast Flow ion-exchange and Sephadex G-100 size-exclusion chromatography. Consequently, two acidic EPS fractions (EPS-1 and EPS-3) were obtained with the average molecular weights of 7.12 × 104 and 3.01 × 104 Da, respectively. They were heteropolysaccharides, among which EPS-1 were rich in mannose, and composed of mannose, glucose, galactose, arabinose, xylose, and rhamnose in a molar ratio of 23.79: 4.80: 1.66: 1.00: 0.21: 0.09, whereas EPS-3 consisted of galactose, mannose, glucose, and arabinose in a molar ratio of 7.47: 3.69: 1.00: 0.85 were rich in galactose. Two EPS fractions also exhibited potential antioxidant properties in vitro, showing strong scavenging activities on three kinds of free radicals and reducing power, and the antioxidant activities of EPS-1 were significantly stronger than that of EPS-3.