Sulfation, characterization, antibacterial activity, and action mechanism of rice bran polysaccharides

In this study, the rice bran polysaccharide (RBP) was modified using the sulfur trioxide-pyridine complexation method. The effects of sulfation modification on the physicochemical properties, structure, bacterial inhibition, and inhibitory mechanism of the polysaccharide were investigated. Sulfated modification reduces the carbohydrate and protein content, increases the molecular weight, and changes the proportion of monosaccharides of RBP. UV–Vis, FT-IR, and NMR spectra confirmed that the modification was successful and the sulfation substitution occurred on hydroxyl groups at C-6. The sulfated rice bran polysaccharide (SRBP) inhibited all the five pathogenic bacterial strains, among which Staphylococcus aureus was the most sensitive, with an MIC of 4 mg/mL. Scanning electron microscopy images revealed that SRBP caused morphological damage and cell rupture of the bacterium, thereby causing an increase in nucleic acid and protein contents, conductivity, alkaline phosphatase, and Na+/K+-ATPase. Clearly, SRBP can act as an alternative derivative of natural antibacterial agents for industrial applications.