10. Solid-State Fermentation: Special Physiology of Fungi

The evolution of higher fungi and actinomycetes took place on solid growth substrates, so these microorganisms are perfectly adapted to grow in a solid environment. This implies that their cultivation in liquid culture may impair their metabolic efficiencies. However, conventional technology for the production of valuable fungal products is liquid submerged fermentation. In recent times, solid-state fermentation has become an alternative industrial production system to produce enzymes, primary and secondary metabolites. There are several advantages in employing many solid-state fermentation processes over the conventional submerged fermentation ones, like higher yields of secondary metabolites or enzymes. Moreover, certain enzymes and secondary metabolites can only be produced in solid-state fermentation. The main advantages of this culture system are related to the special physiology displayed by fungi when growing in solid culture. This chapter describes and analyzes recent advances in our understanding of this special physiology (the physiology of solid medium) and the underlying molecular mechanisms. It is also discussed how this knowledge can be applied to create novel technological advances.