Influence of Substrate Composition on Beta-Glucans Production and Growth of Ganoderma lucidum

Ganoderma lucidum is a medicinal mushroom known and used for centuries in China, claimed as beneficial for health due to the immunological effects provided by (1-3)Beta, (1-6)Beta-glucans present in its cell wall. Agricultural residues can be used as substrate for solid-state fermentation and turned into a product rich in Beta-glucans, that can be used for animal feeding, enhancing the immune response and, thus, reducing the utilization of antibiotics and other drugs. Therefore, colonization rate (growth), yield and concentration of (1-3)Beta, (1-6)Beta-glucans of different agricultural residues, such as soybean hulls, soybean residue and corn residue after solid state fermentation with G. lucidum were determined and evaluated according to their composition before fermentation. Specific growth rate (k) was higher for soybean hulls (k1 = 0.165) and corn residue (k3 = 0.161), but concentration of (1-3)Beta, (1-6)Beta-glucans was higher in soybean residue (234.09 mg g-1) and soybean hulls (180.32 mg g-1). Considering the nutritional composition of substrates, the concentration of (1-3)Beta, (1-6)Beta-glucan can be related to the ratio between fiber carbohydrates and total carbohydrates, demonstrating that fiber is an important feature regarding the production of Beta-glucans by the fungus. Also, colonization rate can be related to the total carbohydrates concentration and total carbohydrates/crude protein ratio, showing that carbohydrates and proteins have an important effect over the growth of the fungus. Soybean hulls showed to be the most feasible substrate for G. lucidum mycelia production presenting high concentration of (1-3)Beta, (1-6)Beta-glucans and colonization rate, with potential to be a dietary supplement for farm animals.