Isolation, structural characterization and immunological activity of an exopolysaccharide produced by Bacillus...

A strain of Bacillus licheniformis 8-37-0-1 with high exopolysaccharide (EPS) production ability was isolated and identified based on morphological and physiological characteristics and phylogenetic analysis of 16S rDNA sequences. A new type of EPS was isolated from the strain fermentation broth by enzymolysis, isopropanol precipitation, anion-exchange, and gel-filtration chromatography. The new EPS was determined as homogeneous, with a molecular weight of 2.826 x 10(4), as determined by High-Performance Size-Exclusion Chromatography Multi-Angle Laser Light Scattering analysis. Its structural characteristics were investigated and elucidated by methylation analysis, partial acid hydrolysis, gas-liquid chromatography mass spectrometry, Fourier transform infrared, and nuclear magnetic resonance spectroscopy. Based on obtained data, the EPS was found to be a levan containing a (2-->6)-linked backbone with a single beta-d-fructose at the C-1 position every seven residue, on average, along the main chain. Preliminary in vitro tests revealed that EPS could significantly stimulate the proliferation of spleen lymphocyte.