Structural and Immunomodulatory Changes in Mycelial and Exopolysaccharides from Monascus purpureus M9 after Mutation of the α-1,3-Glucan Synthase Gene

The molecular structures and immunomodulatory effects of mycelial polysaccharides (MPSs) and exopolysaccharides (EPSs) from wild-type (WT) Monascus purpureus M9 and its α-1,3-glucan synthase gene (ags1) mutant strains (Δags1: gene deletion; ags1OE: gene overexpression) were compared in this study. Mycelial aggregation was reduced in Δags1 and increased in ags1OE, confirming the positive regulatory role of α-1,3-glucan. The EPS content was significantly higher in Δags1 and lower in ags1OE, whereas the MPS contents showed the opposite trend. The relative content of galactomannan in the MPSs and EPSs increased in the following order: ags1OE < WT < Δags1 and Δags1 < WT < ags1OE. In RAW 264.7 cells, MPSs and EPSs from both WT and mutant strains enhanced the cell viability and promoted NO and cytokine (interleukin-6 and tumor necrosis factor-α) secretion. Notably, Δags1-MPS and ags1OE-EPS exhibited enhanced immunomodulatory effects compared to those from WT, likely due to their higher galactomannan contents.