The interest upon products obtained from fungi has increased during the recent years. Among the most noticeable, nutraceuticals, enzymes, and natural drugs occupy a privileged position. Fungal biomass for the obtainment of those products can be produced either by solid-state fermentation (SSF) or submersed fermentation. SSF has been employed for the production of spawn on pretreated wheat grains with the objective of increasing the fungal polysaccharide (glucomannans) contents. Among the important factors for the production of spawn, time of cooking, time of resting after grain cooking, consequently grain moisture, substrate pH, temperature of incubation, and initial inoculum amount are among the most significant. For wheat grains, cooking time of 21 min followed by a 24-min resting time has been shown as optimal for the production of glucomannans by the fungus Agaricus subrufescens (=Agaricus brasiliensis). Amendments of CaSO(4) (up to 3 %) and CaCO(3) (up to 1 %) had an important influence on the substrate pH. In general, better results for glucomannan production were obtained when no supplement was added or when up to 0.25 % CaCO(3) (pH 6.6) has been added to the mix. Our results demonstrate that the inoculum amount necessary for the best polysaccharide levels is around 10.3 %, while the best temperature is around 27.2 °C. Besides using the spawn for its main purpose, it could potentially and alternatively be used as nutraceutical due to the high levels of glucomannan observed (6.89 %), a compound technically proven to be a potent immunostimulatory and antitumoral agent.