A growth medium for fungus is obtained by: (a) treating a mixture of lignocellulosic biomass and water with at least one oxidizing agent and steam at a temperature in a range of from about 130 C to about 220 C for a period from about 5 seconds to about 10 hours; (b) periodically measuring a pH of the mixture for substantially an entire duration of the treating step; and (c) as necessary, based on the pH of the mixture measured in step (b), adjusting the pH of the mixture into a range of from about pH 4.5 to about pH 7.5 by adding abase to the mixture. A method for producing the growth medium for fungi and a method for cultivating fungi are also provided.