Synthesis, characterization and antibacterial activity of sulfate-modified β-glucan.

Natural oat β-glucan (βG) exhibits potential biological activity but is constrained by structural limitations. This study extracted βG from oats and synthesized sulfated derivatives SβG1 and SβG2 with degrees of substitution (DS) of 0.62 and 1.07 by controlling pyridine‑sulfur trioxide complex (SO₃·Pyr) proportions. Techniques including gel permeation chromatography (GPC), Fourier transform infrared (FT-IR), and nuclear magnetic resonance (NMR) spectroscopy confirmed sulfation introduced sulfate groups primarily at the C6 hydroxyl. SβG1 demonstrated greater pH stability than SβG2 over pH 3-10. Antibacterial tests revealed SβG1's concentration-dependent inhibition against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), with stronger effects on S. aureus (60% inhibition at 1.5 mg/mL after 12 h). Molecular dynamics simulation indicated SβG1 binds DOPC/DOPG bacterial membranes via van der Waals forces, increasing the solvent-accessible surface area, reducing membrane rigidity, enhancing fluidity, and disrupting its integrity through widening bilayer spacing and inducing local bending.