Composition and immunomodulatory activity of an arabinoxylan polysaccharide-rich extract of Agaricus subrufescens fermented rye

This study investigated bioactive carbohydrate-related compounds in rye grain overgrown with Agaricus subrufescens mycelia (ROM), using cytokine induction in chicken immune cells. We focused on polysaccharides, as they have been suggested to mediate immunomodulatory effects of rye and Agaricus subrufescens. Fractionation of rye and ROM and subsequent testing fractions on macrophage cell line HD11 showed that IL-12p40 production was mainly induced by hot water-soluble solids (HWSS) with ROM-HWSS more active than rye-HWSS. The bioactive HWSS consisted of polymers >10 kDa. Stimulation of chicken splenocytes further confirmed their immunomodulatory capacity. Rye- and ROM-HWSS >10 kDa mainly consisted of arabinoxylan and glucan with smaller and variable amounts of protein and ferulic acid. Polymeric arabinoxylan structures were confirmed to be present by enzymatic fingerprinting using pure xylanase. NaOH treatment (0.1 M) substantially reduced IL-12p40 induction by HWSS fractions and removed some ferulic ester groups, suggesting that feruloylated arabinoxylan structures contribute to IL-12p40 induction. Degradation of arabinoxylan and small amounts of glucan and fructan in the HWSS fractions with specific enzymes did not affect IL-12p40 induction. Protease, chitosanase and Driselase treatments reduced IL-12p40 induction in ROM-HWSS, suggesting that mycelial compounds (e.g., protein, chitosan and galactan/mannan) may (also) contribute to the bioactivity.