Characterization and Antioxidant Activity of Exopolysaccharides Produced by Lysobacter soyae sp. nov Isolated from the Root of Glycine max L.

Microbial exopolysaccharides (EPSs) have attracted attention from several fields due to their high industrial applicability. In the present study, rhizosphere strain CJ11 ^T was isolated from the root of Glycine max L. in Goyang-si, Republic of Korea, and a novel exopolysaccharide was purified from the Lysobacter sp. CJ11 ^T fermentation broth. The exopolysaccharide's average molecular weight was 0.93 × 10 ⁵ Da. Its monosaccharide composition included 72.2% mannose, 17.2% glucose, 7.8% galactose, and 2.8% arabinose. Fourier-transform infrared spectroscopy identified the exopolysaccharide carbohydrate polymer functional groups, and the structural properties were investigated using nuclear magnetic resonance. In addition, a microstructure of lyophilized EPS was determined by scanning electron microscopy. Using thermogravimetric analysis, the degradation of the exopolysaccharide produced by strain CJ11 ^T was determined to be 210 °C. The exopolysaccharide at a concentration of 4 mg/mL exhibited 2,2-diphenyl-1-picrylhydrazyl free-radical-scavenging activity of 73.47%. Phylogenetic analysis based on the 16S rRNA gene sequencing results revealed that strain CJ11 ^T was a novel isolate for which the name Lysobacter soyae sp. nov is proposed.