A solid fermentation tank refers to a biological reaction process using one or more microorganisms in a water-soluble solid substrate with a certain humidity, in the absence or near absence of free water. From the essence of biological reaction processes, solid-state fermentation is a biological reaction process with gas phase as the continuous phase. Solid state fermentation has the advantages of easy operation, low energy consumption, easy control of the fermentation process, relatively low requirements for sterility, and less likely to cause large-scale pollution. Fungi are microorganisms commonly used in solid-state fermentation because their hyphae, like plant roots, can grow on solid surfaces and penetrate into substrates, producing a variety of extracellular enzyme abilities. Compared to other single celled bacteria and yeast, they are more suitable for solid-state fermentation environments.

Working principle of solid fermentation tank:

Microorganisms grow in a moist and insoluble substrate for fermentation, and do not contain any free water during solid fermentation. As the amount of free water produced by microorganisms increases, the range of solid fermentation extends to viscous fermentation and suspended fermentation of solid particles. It can be assumed that the growth environment between each cell may not be the same. To improve cultivation efficiency, the method of increasing surface area is adopted. In laboratories, inclined test tubes, petri dishes, triangular flasks, and Kjeldahl flasks are generally used for cultivation, while factories mostly use curved plates, curtains, and ventilated koji tanks. Especially in the cultivation of molds, solid culture method is still used for koji making. Due to the selection of agricultural and sideline products such as bran as raw materials, which are inexpensive, have a large particle surface area, are loose and breathable, and are easily obtainable in large quantities, they are widely used in the brewing industry. However, due to the difficulties in large-scale surface culture technology, in fermentation production, liquid surface culture is mostly replaced by liquid deep culture method.