Abstract: A substrate for mycelium growth containing proteins that is constituted by a single product that is sterile prior to the inoculation of the mycelium and is composed, in weight percentages, of the mixture of a water retaining-dispensing component a) in the amount of 16 to 30% by weight of the total weight of components a),b),c) and d), mixed with a buffering component b) in the amount of 25 to 50% by weight of the weight of the water retaining-dispensing component a). The substrate furthermore comprises a protein-containing component c) in the amount of 45 to 75% by weight and a growth-promoting component in the amount of 5 to 25% by weight both with respect to the total weight of components a),b),c) and d) and sufficient water to reach a moisture level between 55 and 60% with respect to the overall weight of the final substrate composition, the protein content of the substrate being preferably 4-20% by weight with respect to the overall weight of the final substrate composition.