Enzyme-Assisted Extraction of Polysaccharides from Steam-Exploded Ganoderma lucidum and Its Yield, Structural Characterisation, and Immunomodulatory Activity

Polysaccharides are the primary bioactive constituents of Ganoderma lucidum. Nevertheless, the industrial potential of this species is constrained by the fact that yields are relatively low. The present study developed a technology and method of extracting polysaccharides from steam-exploded Ganoderma lucidum by enzymatic extraction, with the aim of increasing the yield. The yield of crude polysaccharide is 15.39%, which is 6.96 times that of the traditional water method (2.21%). A purified, homogeneous polysaccharide fraction, designated GLP-L, was isolated with a molecular weight of 5.59 × 106 Da. A detailed analysis of the chemical structure of the substance was conducted, and its immunomodulatory activity was thoroughly researched. A thorough investigation into the structural characteristics of GLP-L was conducted, yielding the following findings: GLP-L is composed of D-mannose (52.76 mol%), D-glucose (36.98 mol%), D-xylose (6.39 mol%), and D-galactose (3.87 mol%). The structure was characterised by methylation, nuclear magnetic resonance spectroscopy, and Fourier transform infrared spectroscopy. In the second step of the process, the following sequence of reactions occurs: 2)-β-D-Gal-(1→4)-α-D-Xylp-(1→3,4)-α-D-Manp-(1→6)-β-D-Glcp-(1→4)-β-D-Manp-(1→4)-α-D-Glcp-(1→. The effect of GLP-L on immunomodulatory activity was evaluated through the RAW264.7 macrophage model, with the results showing an enhancement in phagocytic activity, immune-related enzyme activities, nitric oxide production, and cytokine secretion. The enzyme-assisted extraction method was demonstrated to enhance the yield of Ganoderma lucidum polysaccharides, with the extract displaying noteworthy immunomodulatory activity. This provides a novel strategy for the production of polysaccharide immunomodulators.