Mushroom-growing medium

A process for preparing a cellulosic medium for growing mushrooms, which comprises the steps of

• (a) fermenting a liquid mixture containing sources of soluble carbon and nitrogen under aerobic conditions, the ratio of the nitrogen source to the carbon source being 11-13 parts of nitrogen source per 100 parts of soluble carbon source such as to result in a drop in pH of the mixture to about 4.0-6.0 during the fermentation,
• (b) mixing the fermented liquid mixture with an amount of water sufficient to reduce the nitrogen content of the mixture to about 0.1-0.5% based on the weight of the mixture and calculated from the initial content of nitrogen in the added source thereof,
• (c) incorporating into the fermented liquid mixture a source of calcium ions in the proportion of about 0.005-0.08 parts by weight of calcium ions per part by weight of cellulosic material,
• (d) heating the fermented liquid mixture to a temperature of about 65.degree.-80.degree. C.,
• (e) contacting the fermented liquid mixture with cellulosic material, and
• (f) holding the cellulosic material at a pH of about 6.5-7.5 and at a temperature and for a time sufficient to allow substantial reduction of organisms detrimental to mushroom culture.