Abstract: In the present study, we investigated the effect of a covalent conjugate between soybean protein isolate (SPI) and Pleurotus eryngii polysaccharide (PEP) conjugate on cell viability, neutral red phagocytosis activity, nitric oxide content, and the secretion and mRNA expression of cytokines in RAW264.7 cells. Untreated cells as well as those treated with lipopolysaccharides (LPS), PEP or an SPI-PEP physical mixture were used as controls. The results showed that SPI and PEP as well as their conjugate and mixture at concentrations of 0–50 μg/mL had no significant effect (P > 0.05) on the cell proliferation rate. The conjugate increased neutral red phagocysis activity, NO production and the secretion and mRNA expression of tumor necrosis factor α, interleukin 1β (IL-1β) and IL-6 at 100 μg/mL. In conclusion, soybean protein isolate-Pleurotus eryngii polysaccharide conjugate could enhance immune functions in RAW264.7 cells in a dose-dependent manner. The glycosylation modification of soybean protein can provide a basis for the deep processing and development of cereal proteins.

Key words: soybean protein isolate, soybean protein isolate-Pleurotus eryngii polysaccharide conjugate, RAW264.7 cells, immunoregulation, dose-dependent effect