Immunostimulatory Activity and Structural Characteristics of Unusual Polysaccharides Isolated from Byproducts of the Corn Starch Industry
2024
Kim, S.M. | Shin, K.S.
Corn steep liquor (CSL) is a major byproduct of the corn steeping process in the wet milling industry. Until recently, most of the CSL has been primarily discarded in the ocean without any consideration for recycling. To develop new physiologically active polysaccharides from CSL, they were isolated by sequential ethanol precipitation and their immuno-stimulating activities and structural characteristics were examined. Crude polysaccharide (CBP-0) was isolated from CSL by 80% ethyl alcohol precipitation and then re-fractionated into CBP0.5S and CBP0.5P fractions through successive treatments using 50% and 33% ethanol solution. Peritoneal macrophages stimulated with CBP0.5S showed enhanced production of cytokines such as interleukin (IL)-6, IL-12, and tumor necrosis factor-α in a dose-dependent manner. CBP-0.5S was further purified to yield two subfractions (CBP0.5S-I and -II) by gel filtration using SuperdexTM 200 GL. Of these, CBP0.5S-I potently induced the production of immunostimulatory cytokines by macrophages. CBP0.5S-I was eluted as an almost single peak, with a molecular weight of 410 kDa. It was mainly made up of glucose (72.2%) and galactose (17.2%). Due to the high glucose content, CBP-0.5S-I was assumed to be a β-glucan type polysaccharide. However, methylation analysis showed that CBP-0.5S-I comprised unusual glycosidic linkages such as terminal-, 2-, 3-, and 3,4-linked glucopyranosides. These results suggest that the unusual linkage-containing glucans in CSL may contribute to its macrophage-stimulating activity.
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