Are you talking about the actual stalk of the plant or the cobs? Cobs are good mushroom substrate, not prone to bacterial contamination but probablly would do best with some bran to
boost the nutrition level otherwise I doubt you'd get consistent yields. Because of the high sugar content pasteurized corn stalks probably contaminate easily.Wheat oat barely or rice
straw are all probably better candidates, But yes you could certainly use corn waste for mushroom production.