Study on the Enrichment Effect of Suillus luteus Polysaccharide on Intestinal Probiotics and the Immunomodulatory Activity

<i>Suillus luteus</i> is a highly prized edible fungus and demonstrates significant potential in the field of bioremediation, particularly for soil restoration and pollution mitigation. However, systematic research on the structural characteristics of the bioactive polysaccharides and regulatory effects on gut microbiota metabolism remains scarce. In this study, <i>S. luteus</i> polysaccharide (SLP) was obtained by hot water extraction and the structural characteristics were systematically determined, as well as the regulatory function on gut microbiota metabolism in a tumor-bearing mice model. Results showed that SLP exhibited an average molecular weight of approximately 1.90 × 10⁶ Da with Fuc:Man:Glc:Gal molar ratio of 0.37:1.00:0.72:0.54. The polysaccharide predominantly employed β-(1→4)-Man<i>p</i> as the backbone with α-(1→3)-Fuc<i>p</i>, α-(1→6)-Glc<i>p</i>, and α-(1→6)-Gal<i>p</i> as side chains. SLP administration of 200 mg/kg in tumor-bearing mice exerted enrichment effects of intestinal probiotics, including <i>Lactobacillus</i> and <i>Odoribacter</i>, which were associated with alterations in glyoxylate and dicarboxylic acid metabolism, ultimately enhancing CD4⁺ T cell immunity and resulting in a tumor suppression rate of 53.14%. This study provides a theoretical foundation and supporting data for the development of <i>S. luteus</i> polysaccharide in the functional food field.