Structural characterization of a soluble polysaccharide SSPS1 from soy whey and its immunoregulatory activity in macrophages

A soluble soybean polysaccharide SSPS1 with a molecular weight of 2737 kDa was extracted and purified from soy whey. SSPS1 was composed of glucose (97.3 %) and a small amount of mannose (2.7 %). Structural analysis results suggested that SSPS1 had a → 6)-α-d-Glcp-(1 → glucan structure, with a trace amount of α-d-Glcp-(1 → connected to the main chain via O-3. In vitro immunological experiments suggested that SSPS1 enhanced the growth rate and phagocytic activity of RAW 264.7 macrophages. In addition, SSPS1 stimulated the secretion of cytokines (TNF-α, INF-β, IL-6 and IL-1β) as well as nitric oxide (NO) production through upregulating the expression of the related genes and proteins in RAW 264.7 cells. This study provided a new method for efficient utilization of soy whey, and the results indicate that SSPS1 extracted from soy whey could be used as a novel immunomodulator.