Working principle of biological fermentation tank
The biological fermentation tank uses an air nozzle to atomize high-speed air. The air is dispersed in bubbles. On the aerated side, the average density of the liquid is reduced, and on the non-aerated side, the density of the liquid is reduced, so that there is a difference in density with the liquid on the aerated side, and a liquid circulation is formed in the fermentation tank.
There are many forms of biological fermentation tanks, but the more common ones are internal circulation tube type, external circulation tube type, tension cylinder type and vertical partition type. The outside of the tank is designed with an external circulation type circulation tube, and the inside of the tank is designed with two internal circulation tubes.
In the biological fermentation tank, the liquid level in the tank is below the circulation tube outlet and above the circulation tube outlet. The advantages of the biological fermentation tank are low energy consumption, small effect of frying and fish filleting in the liquid, and simple structure. At the same energy consumption, its oxygen transmission capacity is much higher than that of conventional fermentation tanks.
The main advantages of biological fermentation tanks
1. The structure of the biological fermentation tank is simple, the basic principle is not complicated, and the energy consumption is higher than that of the paddle reactor with a paddle reactor
2. The production depends on the directional circulation of the gas. Non-centrifugal pump-type mechanical equipment, the flow pattern is determined, the liquid circulation is strong, there are no moving parts inside, the shear stress is small, and the energy dissipation is very uniform. Compared with traditional fermentation tanks for organisms, this is especially important for shear-sensitive materials
3. The gas and liquid flow range of the fermentation tank is wide
4. The gas supply efficiency of the biological fermentation tank is high. The air in the riser can be greater than the air in the bubbling reactor, which is beneficial. Aerobic reaction
5. Fluidization may be solid particles, or heavy particles may be completely suspended
Sterilization method of biological fermentation tank
Before sterilizing the biological fermentation tank, the air filter connected to the biological fermentation tank should usually be sterilized with steam and blown dry with air. When sterilizing the tank, first drain and flush the sewage in the feed pipeline, then pump the prepared culture medium into the fermentation tank, and start the agitator for sterilization.
For sterilization of biological fermentation tanks, first open each exhaust valve, introduce steam into the jacket or coil for preheating, and wait until the tank temperature rises to 80~90, and gradually close the exhaust valve. Then, directly pass steam into the fermentation tank from the air inlet, discharge port, and sampling port, so that the tank temperature rises to 118~120, and the tank pressure of the fermentation tank is maintained at 0.09~0.1Mpa (gauge pressure), and maintain for about 30min.
Sterilization of empty fermentation tanks is the sterilization of the fermentation tank body. During air sterilization, the tank pressure is generally maintained at 0.15~0.2Mpa, the tank temperature is 125~130, and it is maintained for 30~45min; the total steam pressure is required to be no less than 0.3~0.35Mpa, and the steam pressure is required to be no less than 0.25~0.3MPa.
In-situ sterilization refers to sterilization without changing the structure of the tank in production, and generally online steam sterilization is used. Offline sterilization can be understood as removing the fermentation tank for sterilization, and small fermentation tanks can be moved to the sterilization box for sterilization.
Important parameter control
PH
In the fermentation process, the reproduction, growth and production of byproducts of microbial cells are affected by pH, so the pH value in the fermentation broth is one of the important parameters in the fermentation process. In order to enable microorganisms to reproduce and grow within the optimal pH range and ultimately synthesize the target metabolites, the pH value in the fermentation process must be strictly controlled.
Dissolved Oxygen (DO)
Dissolved oxygen is one of the key parameters in aerobic fermentation systems in the fermentation of microorganisms and cells, which can directly affect the stability and production cost of fermentation. Oxygen is not easily soluble in water, and the fermentation broth and microbial metabolites in the laboratory fermenter will reduce the solubility of oxygen in the fermentation process. Therefore, controlling dissolved oxygen is not only to increase the beneficial metabolites in fermentation, but also a good solution for reducing costs and increasing efficiency in experiments.
Temperature
Another reason why laboratory glass fermenters are favored by laboratory fermentation users is that their glass material has good electrical and thermal properties, which is an advantage that metal materials cannot match.
The temperature of the fermenter will affect many parts of the fermentation process, such as affecting the reaction rate of enzymes, changing the synthesis direction of bacterial metabolites, affecting microbial metabolism, etc.
Too high a temperature will accelerate the metabolism of the strain and the aging of the bacteria, and may even kill the strain directly. Too low a temperature will slow down the metabolism of the bacteria, and the synthesis rate of the product will also decrease, thus affecting production.
Some strains will change their metabolic pathways at different temperatures, and the corresponding products will also be different. The optimal fermentation temperature of the fermenter is not only beneficial to the growth of bacteria, but also helps the synthesis of metabolites.
However, the intoxication temperature of the same microorganism is different, and the culture conditions require different conditions. Therefore, how to maintain the normal and stable temperature of the laboratory fermenter is an important part of fermentation.
Stirring
Magnetic stirring application: Suitable for scientific research institutes and microbiological laboratories and production of enterprises. It is an ideal equipment for precision fermentation testing and production. It is also suitable for the screening of microbial fermentation medium formulas and long-term microbial fermentation.
Fully automatic mechanical stirring fermentation tank application: Suitable for various
mechanical stirring fermentation tank application: Suitable for various microbial fermentations. The equipment has the characteristics of good stability and easy operation. Users can choose the corresponding structure and shape according to the fermentation process. Multi-fermentation contains seed tanks and fermentation tanks.
The basic structure of the stirring fermentation tank is to install a stirring shaft that goes deep into the tank on the top or bottom of the tank body. Two to four stirring paddles will be equipped on the shaft. The stirring is to better mix the materials in the tank, which is conducive to the contact between solids and nutrients, and is sufficient to facilitate nutrient absorption and the dispersion of metabolites.
In addition, stirring can also disperse the air entering the tank evenly, increase the gas-liquid contact area in the laboratory fermentation tank, and is conducive to the mixing of oxygen and fermentation liquid.
Defoaming
During fermentation, due to the large amount of protein in the fermentation liquid, foam will be generated under conditions such as ventilation and stirring. This is a common phenomenon. However, if the foam increases until it spreads to the entire tank, the fermentation liquid will be out of the fermentation tank, thereby increasing the possibility of contamination.
The defoaming system in the laboratory fermenter is also an important link to ensure the normal fermentation, and it is a very necessary part. First of all, in the early stage, it is necessary to ensure that the amount of liquid in the tank does not exceed three-quarters of the internal space of the fermenter. On the one hand, the remaining space is to give room for the rising page after fermentation ventilation, and on the other hand, it is also to leave buffer time for defoaming.
Laboratory fermentation tanks usually use mechanical defoaming and defoaming agents to defoam.
Mechanical defoaming only works on large bubbles generated at the beginning of fermentation, and has no effect on flowing foam. Therefore, it is mainly used with auxiliary defoaming agents. For automatic defoaming fermentation tanks, there is usually a circuit formed by a set of defoaming electrodes and grounding columns on the tank cover. When the foam rises to the position of the defoaming electrodes, an electrical signal will be formed between the defoaming electrodes, and an early warning switch will be issued. The signal system indicates that the foam in the tank has increased and a defoaming agent needs to be added.
Inoculation volume
The appropriate inoculation amount can help the bacteria in the tank to reproduce and ferment the product quickly, and it can also reduce the growth of impurities. However, too much or too little will affect the normal reproduction of the product. When the inoculation amount is too large, the excessive bacteria will easily lead to insufficient volume in the fermentation tank, and the synthesis of a large number of metabolites will be hindered.
If the inoculation amount is too small, there will be insufficient culture in the fermentation liquid, the fermentation time will be delayed, and the production efficiency of the fermentation tank will be greatly reduced. Correct inoculation amount.
The determination of the inoculation amount is actually to confirm the volume of the inoculated liquid and the subsequent culture liquid volume according to the specified percentage.
