Characterization and antioxidant activity of an acidic exopolysaccharide from Lactobacillus plantarum JLAU103

An acidic exopolysaccharide (EPS) designated as EPS103 was isolated, purified and characterized from Lactobacillus plantarum JLAU103. EPS103 had a relatively lower molecular weight of 12.4 KDa and was consisted of arabinose, rhamnose, fucose, xylose, mannose, fructose, galactose, and glucose in an approximate molar ratio of 4.05: 6.04: 6.29: 5.22: 1.47: 5.21: 2.24: 1.83. A specific spectrogram of acidic polysaccharide was obtained by FT-IR analysis, and both α- and β-type configurations were presented in EPS103 based on the nuclear magnetic resonance spectroscopy. Microstructural analysis of EPS103 demonstrated a smooth and glittering cube structure, and presence of many homogeneous rod-shaped lumps. Comprehensive study of in vitro antioxidant activity indicated that EPS103 possess strong scavenging abilities against hydroxyl, ABTS, and DPPH radicals with the maximum of 80.4%, 65.5%, and 60.5%, respectively, at 10 mg/mL concentration. Furthermore, EPS103 also showed strong ferrous ions chelating activity and oxygen radical absorbance capacity. These results together indicated that the EPS103 isolated from L. plantarum JLAU103 has great potential for use as a natural antioxidant or functional additive in foods industry.