Degradation of Sargassum fusiforme polysaccharides by dielectric barrier discharge plasma and their physicochemical and immunomodulatory properties.

In this study, the effects of dielectric barrier discharge (DBD) plasma on the physicochemical properties and immunomodulatory activities of Sargassum fusiforme polysaccharides (SFP) were investigated. Results showed that the average molecular weight of SFP was reduced from 238 to 20 kDa within 90 min using DBD plasma. The contents of total sugar, reducing sugar and sulfate in the degraded polysaccharides after DBD plasma treatment for 90 min increased by 15.41 %, 150.35 % and 146.33 %, respectively, in comparison to the original SFP. Their protein and uronic acid contents decreased by 70.06 % and 18.75 %, respectively. DBD plasma treatment did not change the monosaccharide type of SFP, but it changed their monosaccharide composition, type of functional group and surface morphology. Furthermore, the treatment significantly improved the immunomodulatory activities of degraded polysaccharides. The polysaccharides with the best activity were obtained after treatment for 60 min (named DSFP-T60). Both SFP and DSFP-T60 significantly promoted the pinocytic capacity of RAW264.7 cells and inhibited the expression and production of nitric oxide, interleukin-6, tumor necrosis factor-α and interleukin-10. Moreover, the degraded polysaccharides showed stronger immunomodulatory activity than SFP. This study will lay a theoretical foundation for exploring a novel and efficient way to degrade polysaccharide with enhanced immunomodulatory activity.