Enhancement of polysaccharide production by optimization of culture conditions in shake flask submerged cultivation of Grifola umbellata

Grifola umbellata (Fries) is a traditional Chinese medicinal mushroom. In this paper, the effects of cultural condition on the mycelial growth and exopolysaccharide (EPS) production were studied. Glucose was the best carbon source for mycelia growth and EPS production. Yeast extract was the best nitrogen source for mycelia growth, whereas skim milk as nitrogen source can remarkably improve EPS production. The optimal medium constituents for EPS production were as follows: glucose 3%, skim milk 0.2%, 0.1% KH₂PO₄, 0.1% MgSO₄, 7H₂O and 0.005% vitamin B1. The initial pH value of 5 was the most efficient to EPS production. The G. umbellata culture with skim milk as nitrogen source displayed a much higher specific EPS yield of 112.35 mg/g, accounting for a 4.36 times increase compared to that with combined nitrogen source medium.