Improvement of Cordyceps militaris Polysaccharides Production by a Sole Corn Steep Liquor Medium, and its Antioxidant Activity

The production of polysaccharides through submerged fermentation using a sole corn steep liquor (CSL) medium with Cordyceps militaris (C. militaris GDMCC 5270) has been successfully demonstrated. Single-factor experiments and orthogonal optimization of culture conditions were conducted for analysis. The results indicated that the optimal fermentation conditions for C. militaris polysaccharides (CMP) were 6% (6 mL/100 mL) corn steep liquor, a 7% (7 mL/100 mL) inoculation amount, and 0.10% inorganic salt (KH₂PO₄: MgSO₄ = 1:1). The fermentation yield of CMP was 1.185 g/L, which was 20.43% higher than that of the conventional group. Ultraviolet and FTIR spectroscopy analyses confirmed that CMP was a nucleic acid- and protein-free β-pyranose. Scanning electron microscopy (SEM) observations revealed that the CMP surface was rough, irregularly connected, and contains voids, exhibited a relatively compact polysaccharide structure. In vitro antioxidant assays demonstrated that CMP possessed significant antioxidant activity and could serve as a potential source of functional food. These results provide a novel approach to enhance the production of CMP using CSL as a medium, and explored promising biological activity and economic potential of Cordyceps militaris polysaccharides.