Systematic Optimization of Ganoderma lucidum Polysaccharide Fermentation: A Guidance for Industrialization

Ganoderma Lucidum Polysaccharide (GLP) is one of the main active components of G. lucidum and a promising prebiotic for various diseases. Maximizing the production of GLP and minimizing the cost is important for the widespread use of GLP in the food/feed and pharmaceutical industries. The purpose of the present study was to optimize the fermentation condition of a single G. lucidum strain (isolated from the fruiting body of G. lucidum mushroom purchased from Linyi (Shandong, China) for GLP production under submerged-liquid fermentation, with some inexpensive substrates. The one-factor-at-a-time method was used to test the effects of inoculum culture time, inoculum size, initial pH, temperature, fermentation time, and medium components, such as carbon source, nitrogen source, KH₂PO₄, MgSO₄, and nonionic surfactant, on GLP production. Then, the response surface methodology was used to optimize the fermentation condition. According to the results, the optimal fermentation condition and medium components for GLP were as follows: 70 h inoculum culture time, 10% inoculum size, temperature of 22°C, pH of 5.56, fermentation time of 105.06 h, 14.07 g/L of glucose, 5.93 g/L of corn meal, 4 g/L of KH₂PO₄, 3 g/L of MgSO₄, 17.5 g/L of soybean meal and 0.2 mL/L of tween 80. After optimization, the production of GLP was 1.90 g/L (containing 1.00 g/L intracellular polysaccharide and 0.90 g/L exopolysaccharide) and the biomass was 15.13 g/L. The G. lucidum strain obtained in this study is not a good producer of GLP, while its optimized medium contains inexpensive corn meal and soybean meal and shows efficient promotion in fermentation products. These results expanded the information on strains for GLP production and provided clues for reducing the cost of industrial GLP production by using inexpensive substrates, such as corn meal and soybean meal.