Improved production of mycelial biomass and ganoderic acid by submerged culture of Ganoderma lucidum SB97 using complex media

Abstract

This study aimed at improving the medium composition for efficient and economical production of mycelial biomass and ganoderic acid (GA) in the submerged culture of Ganoderma lucidum SB97. The effect of various carbon and nitrogen sources on the performance of mycelial growth and GA production by G. lucidum SB97 was investigated. First, the suitable carbon and nitrogen source was determined in shaker flask by the single-factor tests. Second, response surface methodology based on central composite design was applied to explore the optimal medium composition in a 7-l stirred fermentor. Glucose and peptone were advantageous to the formation of mycelial biomass, whereas corn flour and soybean powder were favorable to the accumulation of GA content. The optimal medium composition for GA production was identified as 16 g/l of glucose, 2.93 g/l of peptone, 20.93 g/l of corn flour and 6.44 g/l of soybean powder. Confirmatory experiment of GA production (496 ± 10.4 mg/l) under optimized medium composition showed good agreement with the predicted value (469.3 mg/l). Cultivated with the optimized complex media in a 50-1 stirred fermentor, the mycelial biomass (21.53 ± 0.38 g/l), GA content (23.04 ± 1.27 mg/g-dry cell weight (DCW)), GA production (496 ± 10.4 mg/l), GA productivity (110.2 mg/(l day)) and the maximal specific GA production rate (1.85 × 10 −3 h −1) increased by 18%, 39%, 64%, 46% and 67%, respectively, compared with that of using the semi-synthetic media. This study also demonstrated that the complex media were superior to the semi-synthetic media in avoiding the negative effect of catabolite repression on production of secondary metabolite. Furthermore, the proposed complex media strategy to suit the metabolic characteristics of cell could be applied to other secondary metabolites production from higher fungus in large scale submerged culture.