Optimization of Liquid Fermentation Conditions and Protein Nutrition Evaluation of Mycelium from the Caterpillar Medicinal Mushroom, Cordyceps militaris (Ascomycetes)

Cordyceps militaris is a well-known traditional Chinese medicinal mushroom. In this study, the mycelium of C. militaris was cultured using liquid fermentation technology and the culture medium components were optimized by the orthogonal test method. Our results showed that the optimal medium combination for the mycelium growth is 3% glucose, 3% peptone, 0.1% MgSO4, and 0.2% KH2PO4 The international general nutritional assessment method was applied to the overall evaluation of the protein nutrition value of submerged cultivated mycelium and fruit body of C. militaris. The protein contents in C. militaris mycelium and fruit body are 21.10% and 18.47%, respectively. The first limiting amino acids of C. militaris mycelium and fruit bodies are the sulfur-containing amino acids (methionine and cysteine), and the second limiting amino acid is isoleucine. The quality of amino acids from submerged cultivated mycelium and fruit body from C. militaris was also evaluated by amino acid score (AAS), chemical score (CS), essential amino acid index (EAAI), biological value (BV), nutritional index (NI), and score of ratio coefficient of amino acid (SRCAA). Our data demonstrate that AAS, CS, EAAI, BV, NI, and SRCAA scores of the submerged cultivated mycelium proteins are 62.41, 38.74, 88.37, 84.63, 18.61, and 25.57, respectively, whereas the fruit body proteins are 37.11, 34.59, 61.92, 55.79, 11.44, and 68.51, respectively. The protein content of C. militaris mycelium has higher nutrition value than that of fruit body protein, which holds the promise for future further development. Our study provides the optimal culture conditions and the essential nutritional information of medicinal species, C. militaris.