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Classification and structure of mammalian cell bioreactors

Data: 2020-11-19


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Classification and structure of mammalian cell bioreactors
Do you know the classification and structure of mammalian cell bioreactors? Let's take a look at them together.

   1. Stirred bioreactor

Agitated reactor relies on a stirring blade to provide the power of liquid phase stirring. It has a large operating range, good mixing and uniformity of concentration, so it is widely used in biological reactions.

But because animal cells are not protected by cell walls, they are very sensitive to shearing. Direct mechanical agitation can easily damage them. The traditional stirred reactor for microorganisms is obviously inappropriate for animal cell culture.

Therefore, the agitated reactors in animal cell culture have been improved, including improved oxygen supply, the form of agitating paddles, and the addition of accessories in the reactor.

  2. Improvement of oxygen supply method

Under normal circumstances, agitated reactors are often accompanied by bubbling to provide oxygen for cell growth. Because animal cells provide oxygen for the growth of splicing cells. Since animal cells are also very sensitive to the shearing of bubbling, people have done a lot of work on the improvement of oxygen supply.

Cage oxygen supply is one of the oxygen supply methods for agitated animal cell reactors, that is, bubbles are separated by wire mesh and do not directly contact the cells; the reactor can not only ensure the mixing effect but also have the smallest possible shear force, Meet the requirements of cell growth.

Reported an improved agitated animal cell reactor, the whole is pear-shaped, the stirring is placed at the bottom of the reactor, and a conical stainless steel wire mesh is installed outside the stirring shaft to rotate with the stirring shaft. 

The bubbling tube at the shaft center is bubbled inside the screen, and the cells outside the screen do not directly contact the bubbles.

  3. Improvement of mixing paddle

The form of agitating paddle has a great influence on cell growth. The improvement in this area mainly considers how to reduce the shear force experienced by the cells. Someone has made improvements to the form of the stirring paddles and added accessories to the reactor. 

Experiments have proved that the improved reactor is suitable for high-density culture of cells sensitive to shear forces. The reactor uses a double spiral ribbon stirring paddle, and three surface baffles are installed on the top flange cover.

The angle of each baffle relative to the radial direction is 30°, and it is inserted vertically into the liquid surface. The presence of the baffle reduces the vortex on the liquid surface. 

This reactor maintains a small shear force, and is used for the cultivation of insect cells in the experiment. The final culture density reaches 6×106 cells/mL, and the survival rate is above 98%.

  4. non-stirred bioreactor

The biggest disadvantage of the agitated bioreactor used for animal cell culture is that the shearing force is large and it is easy to damage the cells. Despite various improvements, this problem is still difficult to avoid. 

In contrast, the non-stirred reactor generates less shear force and shows a strong advantage in animal cell culture.

(1) Packed bed reactor filling is to fill the reactor with a certain material for cell growth. The nutrient solution is provided by circulatory perfusion and can be replenished continuously during the circulation process. 

The oxygen required for cell growth can also be carried by the circulating nutrient solution outside the reactor, so there will be no air bubbles to damage the cells. 

This type of reactor has low shear force and is suitable for high-density cell growth.

(2) Hollow fiber reactors Hollow fiber reactors are widely used for animal cell culture due to their low shear force. This type of reactor is composed of hollow fiber tubes. 

Each hollow fiber tube has an inner diameter of about 200 μm and a wall thickness of 50 to 70 μm. The wall of the tube is a porous membrane. 

Small molecules such as O2 and CO2 can diffuse freely through the membrane. Animal cells attach to the outer wall of the hollow fiber tube to grow, which can easily obtain oxygen.

(3) Airlift bioreactor The airlift bioreactor is also one of the commonly used equipment for high-density culture of animal cells, and it is characterized by simple structure and convenient operation. 

Someone used microcarrier culture technology in an airlift reactor to study the process conditions for high-density culture of Vero cells. 

It is proved that the microcarriers suspended in the airlift reactor are cultured with Vero cells. With the addition of a proper amount of protective agent and sufficient nutrient supply, the cells can normally grow to the surface of the microcarriers, and the final density can reach 1.13×106 cells/mL.