Enhanced Release of Immunostimulating β-1,3-Glucan by Autodigestion of the Lingzhi Medicinal Mushroom, Ganoderma lingzhi (Agaricomycetes)

Ganoderma lingzhi is a widely used medicinal mushroom that has antioxidative effects, ameliorates insulin resistance, and improves quality of life in patients with metabolic syndrome. Potentiation of immunity is also a major function of G. lingzhi, and this has been applied in patients with cancer. Supplementing G. lingzhi into foods reduced the metastasis of cancer cells. beta-1,3-glucan is an important bioactive component of G. lingzhi. In this study we enhanced the solubilization of immunostimulating beta-1,3-glucan by autodigestion of G. lingzhi. Fruiting bodies of G. lingzhi were disrupted and susupended in distilled water, the autodigested at 37 degrees C for 24 hours. The resulting suspension was dried by spray drying. To assess the solubilization of beta-1,3-glucan by autodigestion, cold and hot water extracts and sodium hydroxide extracts of G. lingzhi were prepared with and without autodigestion. Sodium hydroxide extracts were neutralized and dialyzed against distilled water. The resulting soluble and precipitated fractions were collected. Chemical, biochemical, and immunochemical characteristics of the extracts were compared. The yields of cold water extracts of autodigested and native G. lingzhi were significantly lower than the other extracts. Glucose was the major sugar components of the hot water extract, cold alkali extract (CAS), and the cold hydroxide extract insoluble in neutral aqueous condition (CASP) of the autodigested and native G. lingzhi. Nuclear magnetic resonance analysis revealed branched beta-glucans in the hot water extract and CAS of the autodigested and native G, lingzhi. By contrast, the CASP of the autodigested and native G. lingzhi comprised mainly mixtures of linear alpha-1,3-glucans and linear beta-1,3-glucans. Immunostimulation by beta-1,3-glucan was examined by limulus factor G activation, dectin-1 binding, and anti-beta-glucan antibody binding. Comparing relative activity, immunostimulating beta-1,3-glucan was detected in the hot water extract, rather than the CAS, of autodigested and native G.lingzhi. Immunostimulating of beta-glucan was also detected in the cold water extract of the autodigested G. lingzhi. These findings demonstrate that autodigestion is a useful processing protocol for enhancing the usefulness of G. lingzhi as a functional food.