Purification, characterization and immunostimulatory activity of a novel exopolysaccharide from Bacillus sp. H5.

Crude exopolysaccharides from extracellular polymeric substances produced by the marine bacterium Bacillus sp. H5 were fractionated using DEAE-Sepharose FF and Sephadex G-75 chromatography. The high molecular weight fraction (89.0 kD) from the neutral fraction was designated EPS5SH; it contained mannose, glucosamine, glucose, and galactose in a molar ratio of 1.00: 0.02: 0.07: 0.02. Infra-red, gas chromatography-mass spectrometry, electrospray ionisation-tandem mass spectrometry analysis and nuclear magnetic resonance revealed EPS5SH was a mannan with α-(1 → 4)-Manp, α-(1 → 2)-Manp, α-(1 → 4, 6)-Manp and β-terminal-Manp. Preliminary in vitro experiments revealed that EPS5SH significantly upregulated nitric oxide synthesis and release of pro-inflammatory factors in murine macrophage RAW264.7 cells. Western blot experiments verified the immunostimulatory effects of EPS5SH through the modulation of the NF-κB and MAPK signalling pathways. In conclusion, EPS5SH was a novel immunostimulatory mannan.