Solid-state fermentation (SSF) can be carried out directly with abundant low-cost biomaterials (including starch, cellulose, lignin, hemicellulose, and chitin) with minimal or no pretreatment, and is thus relatively simple, uses less energy, and can provide unique microenvironments conducive to microbial growth and metabolic activities. Currently, SSF is undergoing a renewed surge of interest, primarily because of many advantages SSF affords. However, large-scale SSF processes are rarely used in Western countries because of some drawbacks including solids handling difficulties, heat and mass transfer limitations, and lack of kinetic and design data for process scale up. In Japan, however, continued development of SSF based on traditional food fermentations occurred, showing that SSF techniques could be used profitably to produce enzymes, fermented foods, and other chemicals.

In this study, a novel spouted-bed bioreactor (SBB) was developed for SSF to produce enzymes such as glucoamylase and phytase from solid substrates (rice, corn, lentiles, etc.) by filamentous fungi, Aspergillus niger and A. sojae. The SBB, which overcomes the drawbacks of conventional SSF carried out in tray and packed bed bioreactors, showed improved fermentation performance, including higher product titers, yields, and productivity. The SSF fermentation kinetics in the SBB, shake flasks, and a packed-bed bioreactor were studied and the results will be presented in this paper. The advantages of SSF over submerged fermentation also will be discussed.