Escherichia coli fermentation tank capable of stably measuring carbon dioxide concentration

Abstract

The invention relates to an Escherichia coli fermentation tank capable of stably measuring carbon dioxide concentration, the Escherichia coli fermentation tank comprises a tank body, a stirring device and a carbon dioxide electrode, the stirring device and the carbon dioxide electrode are both arranged at the top of the tank body, and the stirring device is arranged at the center of the top of the tank body and comprises a power device and a stirring assembly; the power output end of the power device vertically and downwards overhangs into the tank body, the stirring assembly is in transmission connection with the power output end of the power device, the carbon dioxide electrode comprises an installation end and a measurement end, the installation end is fixedly installed at the position, close to the edge, of the top of the tank body, and the measurement end vertically and downwards overhangs into the tank body; the measuring kettle is installed in the tank body, the measuring end of the carbon dioxide electrode can extend into the measuring kettle, and the liquid taking device ensures that fermentation liquid in the measuring kettle submerges the measuring end during measurement. On the premise that normal stirring of fermentation liquor in the tank body is not adjusted, the damage rate of liquid wave flow to a gas permeable membrane is reduced, and the sensitivity and accuracy of electrode detection are ensured.

Description

Technical Field

[0001] The invention relates to the field of bioengineering equipment, in particular to an Escherichia coli fermentation tank capable of stably measuring carbon dioxide concentration. Background Art

[0002] Fermentation-based L-phenylalanine production utilizes genetically engineered Escherichia coli to convert glucose into L-phenylalanine. In this process, glucose serves as the primary carbon source, providing the building blocks for bacterial growth, respiratory metabolism, and product synthesis. Respiratory metabolism generates significant amounts of carbon dioxide. When carbon dioxide concentrations in the fermentation broth reach a certain level, it can affect bacterial growth and metabolism, thereby impacting product synthesis. Therefore, controlling the carbon dioxide concentration in the fermentation broth is crucial for maintaining optimal bacterial growth and metabolism, enhancing product synthesis, and maintaining a high glucose conversion rate.

[0003] To control the carbon dioxide concentration in the fermentation broth, the first thing to do is to measure the carbon dioxide concentration. The more mature method currently is to install a carbon dioxide electrode in the fermentation tank for measurement. The principle of the carbon dioxide electrode is that it is separated from the fermentation broth by a chamber with a gas permeable membrane, and the chamber is filled with electrolyte. Carbon dioxide gas diffuses into the electrolyte inside the electrode through the gas permeable membrane, reaching equilibrium with the bicarbonate ions, thereby changing the pH value of the electrolyte. The internal pH electrode measures this pH change and converts it into a signal related to the carbon dioxide concentration.

[0004] Ideally, a CO2 electrode can accurately measure the CO2 concentration in a fermentation broth. However, the actual operating conditions in a biofermenter are complex and subject to numerous interferences. A major challenge is the high-frequency stirring that often accompanies the fermenter's operation. The primary function of stirring is to thoroughly mix the culture medium, microbial cells, oxygen, and other additives (such as nutrients and pH regulators) within the fermenter, ensuring the uniformity of the fermentation broth. This uniformity is crucial for maintaining the stability and consistency of the fermentation process. Therefore, stirring is generally essential in biofermenters. However, stirring poses several challenges to CO2 electrodes: First, stirring causes the fermentation broth to flow vigorously. The impact of this liquid wave can rupture or deform the gas permeable membrane, thereby affecting the electrode's sensitivity and accuracy. Second, this impact can destabilize the gas permeable membrane on the electrode surface, causing fluctuations in the measurement signal. Furthermore, this liquid wave can accelerate the flow of liquid around the electrode, resulting in a discrepancy between the local CO2 concentration and the actual concentration in the fermentation broth. Summary of the Invention

[0005] In response to the defects of the existing technology, the technical problem to be solved by the present invention is to provide an Escherichia coli fermentation tank that can stably measure the carbon dioxide concentration. Without adjusting the normal stirring of the fermentation liquid in the tank, the probability of liquid wave flow damaging the gas permeability membrane is reduced, thereby ensuring the sensitivity and accuracy of electrode detection.

[0006] In order to solve the above technical problems, the present invention proposes to adopt the following technical solutions:

[0007] Disclosed is an Escherichia coli fermentation tank capable of stably measuring carbon dioxide concentration, comprising a tank body, a stirring device and a carbon dioxide electrode, wherein the stirring device and the carbon dioxide electrode are both arranged on the top of the tank body, with the stirring device arranged at the center of the top of the tank body; the stirring device comprises a power device and a stirring assembly, wherein a power output end of the power device vertically hangs down into the interior of the tank body, and the stirring assembly is transmission-connected to the power output end of the power device; the carbon dioxide electrode comprises a mounting end and a measuring end, wherein the mounting end is fixedly mounted on the top of the tank body near the edge, and the measuring end hangs down vertically into the interior of the tank body; the invention also comprises a measuring pot and a liquid collecting device, wherein the measuring pot is mounted in the tank body, and the measuring end of the carbon dioxide electrode can be inserted into the measuring pot, and the liquid collecting device ensures that the fermentation liquid in the measuring pot submerges the measuring end during measurement.

[0008] Since the measuring pot surrounds the measuring end of the CO2 electrode, it can block the liquid flow caused by stirring of the fermentation liquid, thereby protecting the gas permeable membrane of the CO2 electrode. The liquid collection device is used to keep the tank containing fermentation liquid, ensuring stable and reliable measurement during the fermentation process.

[0009] Preferably, the liquid extraction device includes a lifting assembly, the lifting assembly including a fixed part and a movable part, the fixed part being fixed to the top of the tank body, the movable part being movable up and down relative to the fixed part, and the measuring pot being fixedly mounted on the movable part. The lifting assembly allows the measuring pot to change its position relative to the CO2 electrode, and during this change, the fermentation liquid around the CO2 electrode can be relatively merged or isolated from the fermentation liquid in the tank body, ensuring that the CO2 concentration of the fermentation liquid around the CO2 electrode changes with the fermentation liquid in the tank body.

[0010] Furthermore, the measuring end of the CO2 electrode is located above the fermentation liquid level within the tank, and the measuring jug is barrel-shaped, with a closed bottom and an open top. In this solution, the measuring jug is driven by a lifting assembly to extract the test liquid from the fermentation liquid. When the measuring jug is immersed in the fermentation liquid and stirred by a stirring device, the fermentation liquid exchanges with the test liquid in the measuring jug, ensuring consistency between the concentration of the measured liquid in the measuring jug and that of the fermentation liquid.

[0011] Preferably, the measuring end of the CO2 electrode is located below the level of the fermentation liquid in the tank, and the measuring pot includes a wall portion that can surround the CO2 electrode, with both the top and bottom ends of the measuring pot being open. In this solution, when the CO2 concentration needs to be measured, the measuring pot is lowered to surround the measuring end of the CO2 electrode. At this time, the liquid fluctuations around the CO2 electrode are isolated by the wall portion of the measuring pot. Measurement is then performed after the liquid level around the gas permeable membrane in the measuring pot stabilizes. This prevents the gas permeable membrane from being unstable due to the impact of liquid waves during the measurement process, resulting in fluctuations in the measurement signal, and effectively improves the measurement stability of the CO2 electrode.

[0012] Preferably, the liquid extraction device includes a liquid inlet pipe, a pump body, and a liquid outlet pipe. One end of the liquid inlet pipe is mounted on the tank body and communicates with the interior of the tank body, the other end of the liquid inlet pipe is connected to the water suction port of the pump body, one end of the liquid outlet pipe is connected to the measuring pot, and the other end of the liquid outlet pipe is connected to the water pumping port of the pump body. The pump body uses a diaphragm pump to avoid contamination of the test liquid during transportation. This design allows the fermentation liquid to be circulated in real time in the measuring pot. On the one hand, the carbon dioxide electrode does not need to be extended into the stirred fermentation liquid, preventing the stirred liquid from damaging the gas permeability of the membrane. Secondly, the real-time circulation of the liquid ensures a uniform concentration of the measured liquid, further improving the accuracy of the measurement.

[0013] Furthermore, the liquid outlet tube includes a straight tube portion and a reducing tube portion. The straight tube portion is connected to the water inlet of the pump body, and the reducing tube portion connects the straight tube portion to the measuring pot. The diameter of the reducing tube portion near the measuring pot is larger than that of the reducing tube portion near the straight tube portion. The design of the reducing tube portion gradually slows the flow rate of the test liquid within the tube, thereby reducing the flow rate of the liquid inside the measuring pot, further reducing the impact of the liquid on the gas permeation membrane, and improving the measurement stability of the carbon dioxide electrode.

[0014] Preferably, the measuring pot includes a pot body and a slow-down bucket, wherein a liquid inlet is provided at the bottom of the pot body, a primary slow-down port is provided at the bottom of the slow-down bucket, and a secondary slow-down port is provided at the top of the slow-down bucket, wherein the diameter of the secondary slow-down port is larger than the diameter of the primary slow-down port, the primary slow-down port is connected to the reducing pipe portion, and the secondary slow-down port is connected to the liquid inlet. Such a design further reduces the flow rate of the liquid inside the measuring pot.

[0015] Furthermore, the axis of the carbon dioxide electrode is offset from the axis of the liquid inlet. This staggered design prevents the gushing test liquid from directly hitting the gas permeable membrane, thus avoiding damage to the gas permeable membrane.

[0016] Specifically, the measuring pot also includes a baffle, which is arranged between the liquid inlet and the carbon dioxide electrode to separate the pot body into two chambers. The bottom of the baffle is connected to the bottom of the pot body, and the top of the baffle does not exceed the top of the pot body. The carbon dioxide electrode and the liquid inlet are respectively located in the two chambers, and the measuring end of the carbon dioxide electrode is higher than the baffle. The baffle is designed to block the test liquid surging from the slow bucket and prevent the surging liquid from impacting the gas permeation membrane. When the chamber on the liquid inlet side is filled, the test liquid will overflow the baffle and enter the chamber on the carbon dioxide electrode side. When the test liquid fills both sides of the baffle, the liquid level will tend to rise steadily and gradually submerge the measuring end of the carbon dioxide electrode. The stable liquid level can also further improve the stability of data measurement.

[0017] Preferably, the measuring pot further includes a drain port, which is positioned near the center of the tank body and connects the measuring pot to the tank body. The height of the drain port is no less than the height of the carbon dioxide electrode's measuring end. The drain port's height above the electrode's measuring end ensures that the electrode is fully immersed in the test liquid, preventing premature loss of the test liquid that could render the electrode incapable of detection. This design allows for timely reflux of the test liquid, reduces the total circulation volume of the tested liquid, and minimizes the impact of the circulating liquid on the fermentation progress.

[0018] In summary, the E. coli fermentation tank that can stably measure the carbon dioxide concentration reduces the probability of liquid wave flow damaging the gas permeable membrane without adjusting the normal stirring of the fermentation liquid in the tank, thereby ensuring the sensitivity and accuracy of electrode detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1 It is a schematic cross-sectional structure diagram of the first embodiment of the technical solution;

[0021] Figure 2 It is a cross-sectional structural diagram of the second embodiment of the technical solution;

[0022] Figure 3 It is a schematic diagram of the lifting assembly structure of the first and second implementation methods of the technical solution;

[0023] Figure 4 It is a structural diagram of the third embodiment of the technical solution;

[0024] Figure 5 It is a schematic cross-sectional view of a third embodiment of the technical solution;

[0025] Figure 6 is the Figure 5 An enlarged schematic diagram of icon A in FIG.

[0026] Figure 7 This is a schematic structural diagram of a measuring pot according to a third embodiment of the technical solution;

[0027] in,

[0028] Tank body 1, stirring device 2, power device 21, stirring assembly 22, carbon dioxide electrode 3, mounting end 31, measuring end 32, measuring pot 4, pot body 41, liquid inlet 411, slow-down bucket 42, primary slow-down port 421, secondary slow-down port 422, baffle 43, liquid discharge port 44, liquid extraction device 5, lifting assembly 51, fixing part 52, moving part 53, liquid inlet pipe 54, pump body 55, liquid outlet pipe 56, straight pipe section 561, reducing pipe section 562. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0030] A fermentation tank for Escherichia coli capable of stably measuring carbon dioxide concentration comprises a tank body 1, a stirring device 2 and a carbon dioxide electrode 3, wherein the stirring device 2 and the carbon dioxide electrode 3 are both arranged on the top of the tank body 1, and the stirring device 2 is arranged at the center of the top of the tank body 1. The stirring device 2 comprises a power device 21 and a stirring assembly 22, wherein the power output end of the power device 21 vertically overhangs downward into the interior of the tank body 1, and the stirring assembly 22 is transmission-connected to the power output end of the power device 21, and the carbon dioxide electrode 3 comprises a mounting end 31 and a measuring end 32, wherein the mounting end 31 is fixedly mounted at the top of the tank body 1 near the edge, and the measuring end 32 vertically overhangs downward into the interior of the tank body 1, and further comprises a measuring pot 4 and a liquid taking device 5, wherein the measuring pot 4 is mounted in the tank body 1, and the measuring end 32 of the carbon dioxide electrode 3 can be extended into the measuring pot 4, and the liquid taking device 5 ensures that the fermentation liquid in the measuring pot 4 submerges the measuring end 32 during measurement.

[0031] Since the measuring pot 4 surrounds the measuring end 32 of the carbon dioxide electrode 3, the measuring pot 4 can block the liquid flow generated by the stirring of the fermentation liquid, thereby protecting the gas permeation membrane of the carbon dioxide electrode 3. The liquid collection device 5 is used to keep the fermentation liquid in the tank body 1 to ensure stable and reliable measurement during the fermentation process.

[0032] like Figure 1As shown in the figure, as a first embodiment of the technical solution, the liquid extraction device 5 includes a lifting assembly 51, which includes a fixed part 52 and a movable part 53. The fixed part 52 is fixed to the top of the tank body 1, and the movable part 53 can move up and down relative to the fixed part 52. The measuring pot 4 is fixedly mounted on the movable part 53. The lifting assembly 51 allows the position of the measuring pot 4 relative to the carbon dioxide electrode 3 to change. During the change, the fermentation liquid around the carbon dioxide electrode 3 can be relatively merged or isolated from the fermentation liquid in the tank body 1, ensuring that the carbon dioxide concentration of the fermentation liquid around the carbon dioxide electrode 3 changes with the fermentation liquid in the tank body 1.

[0033] The shape of the measuring pot 4 is further designed, and the measuring end 32 of the carbon dioxide electrode 3 is located above the fermentation liquid level in the tank body 1. The measuring pot 4 is in the shape of a barrel with a closed bottom and an open top. In this solution, the measuring pot 4 is driven by the lifting component 51 to extract the test liquid from the fermentation liquid. When the measuring pot 4 is immersed in the fermentation liquid and stirred by the stirring device 2, the fermentation liquid will be exchanged with the test liquid in the measuring pot 4 to ensure the consistency between the concentration of the measured liquid in the measuring pot 4 and the concentration of the fermentation liquid. Although the measuring pot 4 with a closed bottom has a simple structure, it is difficult to sink into the fermentation liquid to extract the test liquid when there is no liquid in the measuring pot 4. Figure 3 As shown, in this solution, the movable part 53 is a supporting part provided with a sliding screw seat, and the fixed part 52 is a motor arranged on the top of the tank body 1. The power output end of the motor is provided with a sliding screw, and the sliding screw is installed in the sliding screw seat. The motor drives the sliding screw to rotate in the sliding screw seat, providing a force for the measuring pot 4 to move up and down, so that the empty measuring pot 4 can be completely immersed in the fermentation liquid.

[0034] like Figure 2 As shown, as a second embodiment of the technical solution, the measuring end 32 of the carbon dioxide electrode 3 is located below the fermentation liquid level in the tank body 1, and the measuring pot 4 includes a wall portion that can surround the carbon dioxide electrode 3, and the top and bottom ends of the measuring pot 4 are open. In this solution, when it is necessary to detect the carbon dioxide concentration, the measuring pot 4 sinks and surrounds the detection end of the carbon dioxide electrode 3. At this time, the liquid fluctuations around the carbon dioxide electrode 3 are isolated by the wall portion of the measuring pot 4. The measurement is performed after the liquid level around the gas permeable membrane in the measuring pot 4 stabilizes. This prevents the gas permeable membrane from being unstable due to the impact of liquid waves during the detection process, resulting in fluctuations in the measurement signal, and effectively improves the measurement stability of the carbon dioxide electrode 3.

[0035] like Figure 4 as well as Figure 5As shown, as a third embodiment of the technical solution, the liquid collection device 5 includes a liquid inlet pipe 54, a pump body 55, and a liquid outlet pipe 56. One end of the liquid inlet pipe 54 is installed on the tank body 1 and communicates with the interior of the tank body 1. The other end of the liquid inlet pipe 54 is connected to the water suction port of the pump body 55. One end of the liquid outlet pipe 56 is connected to the measuring pot 4, and the other end of the liquid outlet pipe 56 is connected to the water pumping port of the pump body 55. The pump body 55 uses a diaphragm pump to avoid contamination of the test liquid during transportation. This design can circulate the fermentation liquid in the measuring pot 4 in real time. On the one hand, the carbon dioxide electrode 3 does not need to be extended into the stirred fermentation liquid, avoiding the stirred liquid from damaging the gas permeability of the membrane; secondly, the real-time circulation of the liquid ensures that the concentration of the measured liquid is uniform, further improving the accuracy of the measurement. However, both the first and second embodiments have the problem of not being able to measure the concentration in the fermentation liquid in real time. Compared with the third embodiment, the ease of use is poor and the volume of data read per unit time is too small, which cannot effectively form an effective and smooth concentration change curve for reference.

[0036] like Figure 6 As shown, to reduce the flow rate of the liquid inside the pipe, the liquid outlet pipe 56 includes a straight pipe portion 561 and a reducing pipe portion 562. The straight pipe portion 561 is connected to the water intake of the pump body 55, and the reducing pipe portion 562 connects the straight pipe portion 561 to the measuring pot 4. The diameter of the reducing pipe portion 562 near the measuring pot 4 is larger than that near the straight pipe portion 561. The design of the reducing pipe portion 562 can gradually slow the flow rate of the test liquid in the pipe, thereby reducing the flow rate of the liquid inside the measuring pot 4, further reducing the impact of the liquid on the gas permeation membrane, and improving the measurement stability of the carbon dioxide electrode 3.

[0037] In order to reduce the flow rate of the liquid entering the measuring pot 4, the measuring pot 4 includes a pot body 41 and a slow-down bucket 42. The bottom of the pot body 41 is provided with a liquid inlet 411, the slow-down bucket 42 is provided with a primary slow-down port 421 at the bottom, and the slow-down bucket 42 is provided with a secondary slow-down port 422 at the top. The diameter of the secondary slow-down port 422 is larger than the diameter of the primary slow-down port 421. The primary slow-down port 421 is connected to the reducing pipe portion 562, and the secondary slow-down port 422 is connected to the liquid inlet 411. This design further reduces the flow rate of the liquid inside the measuring pot 4.

[0038] To prevent damage to the gas permeable membrane, the axis of the carbon dioxide electrode 3 is offset from the axis of the liquid inlet 411. The staggered design prevents the gushing test liquid from directly hitting the gas permeable membrane, thus avoiding damage to the gas permeable membrane.

[0039] like Figure 7As shown, specifically, the measuring pot 4 also includes a baffle 43, which is arranged between the liquid inlet 411 and the carbon dioxide electrode 3 to separate the pot body 41 into two chambers. The bottom of the baffle 43 is connected to the bottom of the pot body 41, and the top of the baffle 43 does not exceed the top of the pot body 41. The carbon dioxide electrode 3 and the liquid inlet 411 are respectively located in the two chambers, and the measuring end 32 of the carbon dioxide electrode 3 is higher than the baffle 43. The design of the baffle can block the test liquid surging from the slow-down bucket 42 and prevent the surging liquid from impacting the gas permeation membrane. When the chamber on the side of the liquid inlet 411 is filled, the test liquid will overflow the baffle 43 and enter the chamber on the side of the carbon dioxide electrode 3. When the test liquid fills both sides of the baffle 43, the liquid level will tend to rise steadily and gradually submerge the measuring end 32 of the carbon dioxide electrode 3. The stable liquid level can also further improve the stability of data measurement.

[0040] The measuring pot 4 also includes a drain port 44, which is located near the center of the tank body 1 and connects the measuring pot 4 to the tank body 1. The height of the drain port 44 is no lower than the level of the measuring end 32 of the carbon dioxide electrode 3. The height of the drain port 44 above the electrode measuring end 32 ensures that the electrode is completely immersed in the test liquid, preventing premature loss of liquid that could cause the electrode to fail to detect. This design allows for timely reflux of the test liquid, reduces the total circulation volume of the tested liquid, and minimizes the impact of the circulating liquid on the fermentation progress.

[0041] In summary, the E. coli fermentation tank that can stably measure the carbon dioxide concentration reduces the probability of liquid wave flow damaging the gas permeable membrane without adjusting the normal stirring of the fermentation liquid in the tank, thereby ensuring the sensitivity and accuracy of electrode detection.

[0042] In short, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An Escherichia coli fermentation tank capable of stably measuring carbon dioxide concentration, comprising a tank body, a stirring device, and a carbon dioxide electrode, wherein the stirring device and the carbon dioxide electrode are both arranged on the top of the tank body, the stirring device being arranged at the center of the top of the tank body, the stirring device comprising a power device and a stirring assembly, the power output end of the power device vertically overhanging downward into the interior of the tank body, the stirring assembly being transmission-connected to the power output end of the power device, the carbon dioxide electrode comprising a mounting end and a measuring end, the mounting end being fixedly mounted on the top of the tank body near the edge, and the measuring end vertically overhanging downward into the interior of the tank body, characterized in that: It also includes a measuring pot and a liquid taking device. The measuring pot is installed in the tank body, and the measuring end of the carbon dioxide electrode can be extended into the measuring pot. The liquid taking device ensures that the fermentation liquid in the measuring pot does not exceed the measuring end during measurement.

2. The E. coli fermenter capable of stably measuring carbon dioxide concentration according to claim 1, characterized in that: The liquid taking device includes a lifting assembly, which includes a fixed part and a moving part. The fixed part is fixed on the top of the tank body, and the moving part can move up and down relative to the fixed part. The measuring pot is fixedly installed on the moving part.

3. The E. coli fermenter capable of stably measuring carbon dioxide concentration according to claim 2, characterized in that: The measuring end of the carbon dioxide electrode is located above the fermentation liquid level in the tank body, and the measuring pot is in the shape of a barrel with a closed bottom and an open top.

4. The E. coli fermenter capable of stably measuring carbon dioxide concentration according to claim 2, characterized in that: The measuring end of the carbon dioxide electrode is located below the fermentation liquid level in the tank body. The measuring pot includes a wall portion that can surround the carbon dioxide electrode. Both the top and bottom ends of the measuring pot are open.

5. The E. coli fermenter capable of stably measuring carbon dioxide concentration according to claim 1, characterized in that: The liquid taking device includes a liquid inlet pipe, a pump body and a liquid outlet pipe. One end of the liquid inlet pipe is installed on the tank body and communicates with the inside of the tank body. The other end of the liquid inlet pipe is connected to the water suction port of the pump body. One end of the liquid outlet pipe is connected to the measuring pot, and the other end of the liquid outlet pipe is connected to the water pumping port of the pump body.

6. The E. coli fermenter capable of stably measuring carbon dioxide concentration according to claim 5, characterized in that: The liquid outlet pipe includes a straight pipe portion and a reducing pipe portion. The straight pipe portion is connected to the water pump port of the pump body. The reducing pipe connects the straight pipe portion and the measuring pot. The diameter of the reducing pipe near the measuring pot is larger than that near the straight pipe portion.

7. The E. coli fermenter capable of stably measuring carbon dioxide concentration according to claim 6, characterized in that: The measuring pot includes a pot body and a slow-down bucket. A liquid inlet is provided at the bottom of the pot body, a primary slow-down port is provided at the bottom of the slow-down bucket, and a secondary slow-down port is provided at the top of the slow-down bucket. The diameter of the secondary slow-down port is larger than the diameter of the primary slow-down port. The primary slow-down port is connected to a reducing pipe, and the secondary slow-down port is connected to the liquid inlet.

8. The E. coli fermenter capable of stably measuring carbon dioxide concentration according to claim 7, characterized in that: The axis of the carbon dioxide electrode and the axis of the liquid inlet are offset.

9. The E. coli fermenter capable of stably measuring carbon dioxide concentration according to claim 8, characterized in that: The measuring pot also includes a baffle, which is arranged between the liquid inlet and the carbon dioxide electrode to separate the pot body into two chambers. The bottom of the baffle is connected to the bottom of the pot body, and the top of the baffle does not exceed the top of the pot body. The carbon dioxide electrode and the liquid inlet are respectively located in the two chambers, and the measuring end of the carbon dioxide electrode is higher than the baffle.

10. The E. coli fermenter capable of stably measuring carbon dioxide concentration according to claim 5, characterized in that: The measuring pot further comprises a liquid discharge port, which is arranged on a side close to the center of the tank body and connects the measuring pot and the tank body. The level of the liquid discharge port is not lower than the level of the carbon dioxide electrode measuring end.

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