Solid fermentation tanks correspond to liquid fermentation tanks. Solid fermentation refers to a fermentation process where the fermentation medium is solid, and it remains in a solid state after fermentation is completed. Therefore, a solid fermentation tank is a vessel that provides the site and conditions for completing solid fermentation. Solid fermentation requires a certain level of humidity and uniformity, so the setting of humidity control and a stirring system are key controls in solid fermentation.
Solid fermentation has advantages such as simple operation, low energy consumption, easy control of the fermentation process, relatively low requirements for sterility, and a low probability of large-scale contamination. After raw materials for solid fermentation tanks undergo pre-processing such as steaming and sterilization, they are made into solid materials with a certain moisture content, inoculated with pre-cultured strains, and then fermented.
After fermentation is mature, the material is discharged in a timely manner and subjected to appropriate treatment, or the product is extracted. It has relatively high efficiency, and the extraction process is simple and controllable.
Solid fermentation tanks can be divided into vertical fermentation tanks and horizontal fermentation tanks. The specific selection between a vertical or horizontal fermentation tank needs to be determined according to the specific state of the culture medium.
Solid fermentation tanks can maintain the temperature required for fermentation through constant temperature control via jackets. Sterilization can be conducted either inside the tank or before the materials enter the tank for fermentation. Humidity regulation is generally monitored by a humidity controller, which adjusts and maintains constant humidity within the range of 0–100% through aseptic water spraying (mist) devices and moisture evaporation devices, with real-time display via humidity sensor devices.
Ventilation control is also a key point for solid fermentation tanks. The ventilation must be sterile, and both the air volume and velocity should be adjustable. The stirring system is the most critical control point of a solid fermentation tank. Since solid-state fermentation requires uniform inoculation and the materials are not easily mixed, the stirring design must ensure uniform mixing of the materials and even distribution of strains after inoculation. Inoculation is typically performed via spraying. Stirring forms include mechanical stirring and synchronous stirring of the tank body and mechanical agitator. The stirring system adopts top direct-connected mechanical or horizontal shaft stirring, with mechanical seals for the kettle, various high-performance stirring paddles, defoaming paddles, AC speed-regulating motors, and stepless speed adjustment. Glass windows are provided for easy observation of the internal state of the tank.
Various process interfaces include: temperature and humidity interfaces, aseptic sampling ports, specially designed large discharge ports, liquid strain inoculation ports, feeding ports, pressure gauge ports, air inlets, air outlets, and upper/lower jacket ports, etc.
