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Let's Learn The Basics Of Fermentation Tanks Together!

Technical Knowledge 2022-04-26 17:13:29
There is no agitator in the fermentation tank for bacteria and cells, and there is a guide tube in the center, which divides the fermented mash into an ascending area (inside the guide tube) and a descending area (outside the guide tube). Air nozzles, or annular air distribution pipes, are installed in the lower part of the ascending area, and there are many nozzle holes below the air distribution pipes.

Pressurized sterile air is injected into the fermentation broth through nozzles or nozzle holes, and the air speed injected from the air nozzle can reach 250~300 (m/s), sterile air is sprayed into the rising pipe at high speed, and the air bubbles are divided into small pieces by the turbulent action of the gas-liquid mixture, which is in close contact with the fermentation liquid in the guide tube to supply dissolved oxygen in the fermentation liquid.

Due to the reduced density of the gas-liquid mixture formed in the guide tube and the jet kinetic energy of the compressed air, the liquid in the guide tube moves upward; After reaching the upper liquid level of the reactor, a part of the gas bubbles are broken, and the carbon dioxide is discharged into the upper space of the reactor, and the fermentation liquid that discharges part of the gas flows from the top of the guide tube to the outside of the guide tube, the fermentation liquid outside the diversion cylinder has a small gas hold-up rate and an increase in density, and the fermentation liquid decreases, and enters the rising pipe again to form a circulating flow to realize mixing and dissolved oxygen mass transfer.

Features of Fermentation Tanks

(1) The reaction solution is evenly distributed: Uniform mixing of gas-liquid-solid three-phase and good mixing and dispersion of solution components are common requirements of bioreactors, because flow, mixing and residence time distribution are all affected. For many aerated fermentations with intermittent or continuous feeding, the substrate and dissolved oxygen are dispersed as uniformly as possible to ensure that the concentration of the substrate everywhere in the fermenter falls within the range of 0.1% to 1%. Dissolved oxygen is 10% to 30%. This is beneficial for the growth and product production of aerobic biological cells. In addition, it is necessary to avoid the formation of a stable foam layer on the liquid surface of the fermenter, so as to avoid the accumulation of biological cells on it and damage or even death. There are also medium components, especially starchy granular materials that are easy to settle, and should be able to be suspended and dispersed. Airlift loop reactors can meet these requirements well.

(2) Higher dissolved oxygen rate and dissolved oxygen efficiency: The airlift reactor has a high gas-holdup and a specific gas-liquid contact interface, so it has a high mass transfer rate and dissolved oxygen efficiency. The volumetric oxygen efficiency is usually higher than that of the mechanical stirring fermentation tank, the kLd can reach 2000h, and the dissolved oxygen power consumption is relatively low.

3) The shear force is small, and the fermenter has little damage to biological cells: Since the airlift bioreactor has no mechanical stirring impeller, the shear damage to the cells can be reduced to a lower level, which is especially suitable for the cultivation of plant cells and tissues.

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