Synthesis and antibacterial activity of quaternized curdlan

The quaternized curdlan with a high degree of substitution (DS) were synthesized using glycidyl trimethyl ammonium chloride in NaOH aqueous solution by two-step in this work. The structure, property and morphology of curdlan and quaternized curdlan were characterized by 1H NMR, 13C NMR, FTIR, XRD, GPC, TG and ultra-depth three-dimensional microscope. The DS were calculated from the integral area of 1H NMR spectroscopy. The influence of the molar ratio which is between the anhydroglucose unit (AGU) and the quaternized reagent (QR), and reaction time on the DS were studied. The quaternized curdlan with different DS had little difference in the molecular weight (M w), structure and thermal stability. The TGA results showed that the thermal stability of quaternized curdlan was lower than curdlan. Turbidity analysis method shows that the aqueous solution of quaternized curdlan has good stability. The antibacterial activity of quaternized curdlan was investigated by disc-diffusion methods, which revealed that the quaternized curdlan with high DS had antibacterial effect against Escherichia coli, Staphylococcus and Fusarium. The antimicrobial test results showed that the antibacterial activities of quaternized curdlans against Staphylococcus were much better than E. coli, and Fusarium were much better than Staphylococcus.