Continuous process for producing sterile substrate for solid state fermentation with fungi with the steps: a) providing a vegetable raw material which consists of at least 40% by weight, based on its dry weight, of lignocellulose and hemicellulose, the raw material being formed from particles with an average size of less than 10 mm, b) mixing the plant raw material with water to form a mass with a solids content of 40 to 75% by weight, c) heating and mixing the water-containing mass from step b) for at least 3 hours at a temperature of 30 to 50° C in order to activate the microbiome present on the substrate, d) mixing the substrate obtained in step c) with water to form a suspension with a solids content of 5 to 15% by weight, e) heating the suspension from step d) to a temperature of 70 to 99°C at atmospheric pressure for a period of 5 to 60 minutes in order to condition the solid/raw material in the suspension (swell, pasteurize), f) the suspension from step e) is then subjected to a comminution and mechanical pulping process and pumped through two double-pipe apparatus and a pressure vessel, g) heating the suspension from step f) in a continuous process to 100 to 121 °C at up to 2 bar pressure, holding at these conditions for 10 to 30 minutes, then recooling in countercurrent to below 100°C, h) separating the water from the recooled suspension using a continuously operating filter device, whereby a sterile substrate with a solids content of 30 to 50% by weight is obtained and returning the water separated in step g) to step d), i) evaporating water from the substrate obtained in step h) at a reduced pressure of 20 to 100 mbar until the substrate has a water content of 45 to 55% by weight, based on the total weight of the substrate, j) inoculating the sterile substrate obtained in step i) with pure fungal cultures, optionally adding additives to promote fungal growth, cooling the substrate with water to 25°C or less and adjusting the water content in the substrate to 56 to 69% wt. k) portioning and packaging the inoculated substrate and moving it to growing rooms, and l) Fermentation at a substrate core temperature of 22-28°C or less, a relative air humidity in the room of at least 88% and a CO 2 partial pressure in the room of max. 0.03 bar. a) providing a vegetable raw material which consists of at least 40% by weight, based on its dry weight, of lignocellulose and hemicellulose, the raw material being formed from particles with an average size of less than 10 mm, b) mixing the plant raw material with water to form a mass with a solids content of 40 to 75% by weight, c) heating and mixing the water-containing mass from step b) for at least 3 hours at a temperature of 30 to 50° C in order to activate the microbiome present on the substrate, d) mixing the substrate obtained in step c) with water to form a suspension with a solids content of 5 to 15% by weight, e) heating the suspension from step d) to a temperature of 70 to 99°C at atmospheric pressure for a period of 5 to 60 minutes in order to condition the solid/raw material in the suspension (swell, pasteurize), f) the suspension from step e) is then subjected to a comminution and mechanical pulping process and pumped through two double-pipe apparatus and a pressure vessel, g) heating the suspension from step f) in a continuous process to 100 to 121 °C at up to 2 bar pressure, holding at these conditions for 10 to 30 minutes, then recooling in countercurrent to below 100°C, h) separating the water from the recooled suspension using a continuously operating filter device, whereby a sterile substrate with a solids content of 30 to 50% by weight is obtained and returning the water separated in step g) to step d), i) evaporating water from the substrate obtained in step h) at a reduced pressure of 20 to 100 mbar until the substrate has a water content of 45 to 55% by weight, based on the total weight of the substrate, j) inoculating the sterile substrate obtained in step i) with pure fungal cultures, optionally adding additives to promote fungal growth, cooling the substrate with water to 25°C or less and adjusting the water content in the substrate to 56 to 69% wt. k) portioning and packaging the inoculated substrate and moving it to growing rooms, and l) Fermentation at a substrate core temperature of 22-28°C or less, a relative air humidity in the room of at least 88% and a CO 2 partial pressure in the room of max. 0.03 bar.