Abstract:The liquid culture conditions were optimized for maximal production of mycelial biomass and exopolysaccharide by Paecilomyces japonica.The effects of medium composition，C/N ratio and physical parameters were investigated.From these experiments，30 g/L glucose，20 g/L yeast extract，0.5 g/L KH2PO4，and 0.1 g/L MgSO4in distilled water were found to be the most suitable carbon，nitrogen，and mineral sources，respectively. The optimal temperature，initial pH，agitation，and aeration were determined to be 27℃，uncontrolled pH，400 r/min and for 7d，respectively.Under these optimal conditions，the maximum mycelial growth and polysaccharides production were 2.51 g/L and 23.5 g/L，respectively.