ABSTRACT
Nowadays, there is great interest in the development and use of natural food and additives derived from microorganisms, since they are more desirable than the synthetic ones produced by chemical processes. Solid-state fermentation (SSF) is de ned as the cultivation of microorganisms on solid, moist substrates in the absence of a free aqueous phase; that is, at average water activities (de ned as the relative humidity of the gaseous phase in equilibrium with the moist solid) signi cantly below 1 (Hölker and Lenz 2005). The low moisture content means that fermentation can only be carried out by a limited number of microorganisms, mainly yeasts and fungi, although some bacteria have also been used (Pandey et al. 2000a).
