Abstract

Response surface methodology (RSM) was used to optimize the critical medium ingredients of Ganoderma sinense. A central composite design (CCD) was employed to determine the maximum biomass and extracellular polysaccharide (EPS) yields at optimum levels for glucose, peptone and KH₂PO₄. A mathematical model was then developed to show the effect of each medium composition and their interactions on the production of mycelial biomass and EPS. The model predicted the maximum biomass yield of 12.58 g/l that appeared at glucose, peptone, KH₂PO₄ of 42.0 5.28 and 0.77 g/l, respectively; while a maximum of EPS yield of 309.6 mg/l appeared at glucose, peptone, KH₂PO₄ of 45.4 4.98 and 0.79 g/l, respectively. These predicted values were also verified by validation experiments. The excellent correlation between predicted and measured values of each model justifies the validity of both the response models. The results of bioreactor fermentation also show that the optimized culture medium enhanced both biomass (13.01± 0.36 g/l) and EPS (352 ± 7.9 mg/l) production by G.sinense in a large-scale fermentation process.

Key words: Ganoderma sinense, submerged culture, response surface methodology, central composite design, extracellular polysaccharide.