Marlow Foods Ltd. says its Quorn brand of meat-free foods and Mycoscent brand of low-sodium flavorings are made from mycoprotein, though its usage differs from the dictionary definition. Proteins, including albumin, contain no dietary fiber, but their website claims mycoprotein to be a good source of it.
According to Marlow's website, "Mycoprotein is derived from Fusarium venenatum, from the fungi family, as are truffles, morel and other mushrooms, originally discovered growing in a field in Buckinghamshire in the United Kingdom." The specific fungus had previously been misidentified as Fusarium graminearum, which is often found in soil but can be found parasitizing wheat and other cereals.
See Quorn for information on the manufacture of the Marlow Foods product, and the controversy surrounding its U.S. introduction.