Abstract: To affirm the optimized chemical constitution of submerged fermentation culture medium for Monascus exopolysaccharide（EPS）, the experiment was carried out with rice powder as the main substrate medium and by single factor, orthogonal and other experimental methods. The result shows that the best supplementary nitrogen source is soybean powder added to 10 mg/mL. The yield of EPS was inhibited by MnSO₄, CaCl₂, CuSO₄, FeCl₃, FeCl₂, ZnSO₄, and activated by KCl, KH₂PO₄, NaCl. In addition, all of these inorganic salts’ amount added are 0.15 mg/mL. Consequently, the fermentation mediums were optimized as follows: the powder of rice and the powder of soybean each account for 40 mg/mL and 10 mg/mL of the total amount. The dosages of KCl, KH₂PO₄ and NaCl were all 0.15 mg/mL. Under this condition, the yield of EPS reached 112.3 mg/mL on average, after culture age of 120 h. It is about twice the yield of liquid fermented polysaccharides based on rice flour alone.

Key words: Monascus, exopolysaccharide, liquid state fermentation, conditional optimization