CN116179303A - Culture device and method based on gas preconfiguration and circulation supply - Google Patents

Abstract

The invention discloses a culture device and a method based on gas pre-preparation and cyclic supply, wherein the device comprises: the culture flask is communicated with the first pipeline, and the first pipeline is communicated with a liquid inlet and outlet system; the three-way valve is respectively communicated with the preassembled gas tank, the gas source through the gas metering pump and the culture bottle through the second pipeline; the preassembled air tank is communicated with the culture flask through a third pipeline; the culture bottle is connected with a turbidity sensor for detecting the turbidity of the liquid in the bottle; the preassembled gas tank is connected with a pressure sensor for detecting the pressure of the gas in the tank; the first electromagnetic valve is used for controlling the communication relation between the second pipeline and the third pipeline and each culture bottle respectively; the second electromagnetic valve is used for controlling the communication relation between the preassembled gas tank and the third pipeline; the invention realizes uninterrupted gas preparation and supply, and effectively improves the utilization rate of raw material gas; the automatic gas treatment, gas collection, culture solution addition and other functions can be realized under the unattended condition, so that the labor cost and the time cost are saved, and the culture efficiency is improved.

Description

Culture device and method based on gas preconfiguration and circulation supply

technical field

The invention relates to the technical field of microorganism cultivation, in particular to a cultivation device and method based on gas preconfiguration and circulation supply.

Background technique

The resource utilization of agricultural bulk waste such as straw is related to the sustainable development of agriculture, ecological environment and social economy. Biotransformation and synthesis technology is an effective means to realize the resource utilization of these wastes, but at present, biotransformation only focuses on the end products, and the exhaust gas such as CO2 has not been fully utilized, and this part of CO2 may account for the entire biomass carbon content. About 50%. Making full use of this half of the carbon is of great significance for realizing high-value waste conversion and carbon emission reduction.

The existing CO2 fermentation tail gas circulation culture device focuses on the treatment of the fermentation product CO2 tail gas. The CO2 tail gas is directly used for circulation culture after simple filtration. This method is relatively simple and effective, but there are the following problems:

1. The accuracy of gas supply is poor; when ventilating, various formula gases will not enter the fermentation system according to the set flow rate due to liquid level pressure, resulting in unstable gas supply and inaccurate ventilation; especially when multiple tanks are connected in parallel, due to aeration Head and liquid level difference problems often lead to large differences in aeration between different fermenters, and even cross-gas problems.

2. The scope of application is narrow; it is mainly suitable for the biotransformation process of the same fermentation tail gas and culture gas, and is mainly suitable for the biological cycle culture of microalgae. When it is applied to the scene that requires mixed gas culture, because its gas cycle only Contains single exhaust gas such as CO2, so additional gas supply facilities and equipment are required;

3. Manual on-duty is required; during the working process of the system, technical personnel are required to be on-site to adjust the specific parameters of each feeding and gas circulation according to the cultivation process to ensure the smooth progress of the cultivation process;

4. The tail gas is not suitable for direct use in circulation culture; the concentration of fermentation tail gas is generally high, and the proportion of other components mixed with it is not fixed, so it cannot be guaranteed that the proportion of each component in the gas is suitable for culture in circulation culture , especially when the concentration of a certain gas in the tail gas is too high (such as CO2), it may cause relatively adverse effects on the cultivation process.

Contents of the invention

In order to solve the above-mentioned technical problems, the present invention provides an automatic culture device and method based on gas preconfiguration and cyclic supply, which are applicable to various application scenarios.

In order to realize the above technical purpose, the technical solutions provided by the present invention include:

A culture device based on gas preconfiguration and circulation supply, including:

A number of culture bottles communicated through the first pipeline, and the first pipeline is also connected with an inlet and outlet liquid system;

A three-way valve, the three-way valve is connected to the pre-installed gas tank, the gas source through the gas metering pump, and the culture bottle through the second pipeline, and the gas concentration sensor is arranged on the second pipeline;

The pre-installed gas tank is also communicated with the culture bottle through a third pipeline, and a circulating pump is arranged on the third pipeline;

The culture bottle is connected with a turbidity sensor for detecting the turbidity of the liquid in the bottle, and a first liquid level sensor for detecting the height of the liquid in the bottle;

The pre-installed gas tank is connected with a pressure sensor to detect the gas pressure in the tank, and a second liquid level sensor to detect the liquid height in the tank;

The pre-installed gas tank is also provided with a first liquid outlet end and an exhaust end;

The first electromagnetic valve is used to control the communication relationship between the second pipeline and the third pipeline and each culture bottle;

The second solenoid valve is used to control the communication relationship between the pre-installed gas tank and the third pipeline;

Wherein, one end of the second pipeline connected to the culture bottle is located above the culture liquid level; one end of the first pipeline and the third pipeline connected to the culture bottle is located below the culture liquid level.

In some preferred embodiments, the liquid inlet and outlet system includes a liquid inlet and a second liquid outlet in parallel and communicated with the first pipeline; the liquid inlet and the second liquid outlet are respectively set There are solenoid valves and liquid metering pumps.

In some preferred embodiments, an aeration head is provided at one end of the third pipeline extending into the culture bottle.

In some preferred embodiments, an adjustable damper is provided on the third pipeline in front of the culture bottle and behind the first electromagnetic valve.

The present invention also provides a cultivation method based on gas preconfiguration and circulation supply, including:

S1. Add quantitative culture solution to several culture bottles through the liquid inlet and outlet system;

S2. The three-way valve conducts the pre-installed gas tank and the gas source, and adds a certain amount of raw material gas to the pre-installed gas tank through the gas source;

S3. The three-way valve conducts the pre-installed gas tank and the second pipeline, opens the first solenoid valve and the second solenoid valve, starts the circulation pump, and makes the gas flow through the pre-installed gas tank, the third pipeline, the culture bottle, and the second pipeline. Sequential circulation of pipelines and three-way valves;

S4. When the detection value of the gas concentration sensor reaches the predetermined value, turn off the circulation pump, open the exhaust end and collect the exhaust gas, close the exhaust end when the pressure in the tank returns to atmospheric pressure, and repeat steps S2-S4.

In some preferred embodiments, it also includes the steps of:

When the detection value of the turbidity sensor reaches the predetermined value, control the first electromagnetic valve to keep the third pipeline and the culture bottle connected, and close the conduction between the second pipeline and the culture bottle; the quantitative old culture solution is exported through the liquid inlet and outlet system , and supplement the same amount of new culture solution; after the supplement is completed, control the first solenoid valve to keep the third pipeline connected to the culture bottle, and open the second pipeline to the culture bottle.

In some preferred embodiments, it also includes the steps of:

When the second liquid level sensor detects that the liquid level in the pre-installed gas tank reaches the preset height, the liquid in the tank is led out through the first liquid outlet; when the pressure sensor detects that the gas pressure in the pre-installed gas tank reaches the preset value, it opens Vent to reduce tank pressure.

Beneficial effect

1. The present invention conducts batch processing of gas through pre-installed gas tanks and circulation pipelines, which can realize uninterrupted gas preparation and supply, and effectively improve the utilization rate of raw gas; According to the problem of the set flow supply, the uniform distribution of the gas in the liquid can be improved, especially under the condition that it cannot be stirred; 3. The damper can effectively balance the inlet pressure of each tank without significantly increasing the economic cost. Through simple means, the ventilation volume of each tank is consistent, ensuring continuous and stable operation; 4. By presetting the parameters of each sensor and coordinating with the circulation pipeline, automatic gas processing, gas collection, and culture can be realized under unattended conditions. Functions such as collection and addition of culture medium save labor costs and time costs and improve culture efficiency; 5. Modular components are used, which can be freely combined according to actual needs to achieve customized functions and processing capacity.

Description of drawings

Fig. 1 is a schematic structural diagram of a culture device based on gas pre-allocation and circulation supply in a preferred embodiment of the present invention;

Fig. 2 is a schematic flow chart of a culture method based on gas pre-allocation and cyclic supply in another preferred embodiment of the present invention;

In the figure: 1. culture bottle; 2. liquid inlet and outlet system; 3. three-way valve; 4. pre-installed gas tank; 5. gas source; 6. gas metering pump; 7. second pipeline; 8. gas concentration sensor ;9, the third pipeline; 10, circulation pump; 11, turbidity sensor; 12, the first pipeline; 13, the first liquid level sensor; 14, pressure sensor; 15, the second liquid level sensor; 16, the first 1. Outlet end; 17. Exhaust end; 18. First solenoid valve; 19. Second solenoid valve; 20. Safety valve; 21. Damper; 22. Liquid metering pump; 101. Aerator head; 201. Inlet Liquid end; 202, the second liquid outlet;

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further elaborated below in conjunction with the accompanying drawings. In describing the present invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", " The orientation or positional relationship indicated by "outside", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, so as to Specific orientation configurations and operations, therefore, are not to be construed as limitations on the invention.

As shown in Figure 1, this embodiment provides a culture device based on gas preconfiguration and circulation supply, including:

A number of culture bottles 1 communicated through the first pipeline 12, and the first pipeline 12 is also connected with the liquid inlet and outlet system 2; wherein, those skilled in the art can reasonably set specific culture bottles 1 according to the needs of the actual culture volume The quantity can also be made of pressure-resistant transparent materials or metal tanks according to the actual culture conditions. It can be installed on a base with functions such as constant temperature, light and stirring, and can increase the monitoring and control of pH, ion concentration and other indicators. other ancillary devices and equipment. The liquid inlet and outlet system 2 is for supplementing and/or collecting the culture fluid in the culture bottle 1, and its specific implementation can be set by those skilled in the art according to the common fluid replenishment and fluid outlet methods. In some preferred embodiments, a way to achieve liquid inlet and outlet by shunting is provided, including:

The liquid inlet and outlet system 2 includes a liquid inlet port 201 and a second liquid outlet port 202 which are respectively parallel and communicated with the first pipeline 12; the liquid inlet port 201 and the second liquid outlet port 202 are respectively provided with solenoid valves and liquid metering pump 22.

Three-way valve 3, the three-way valve 3 communicates with the pre-installed gas tank 4, the gas source 5 through the gas metering pump 6, and the culture bottle 1 through the second pipeline 7, and the second pipeline 7 is provided with There is a gas concentration sensor 8;

The pre-installed gas tank 4 is also communicated with the culture bottle 1 through the third pipeline 9, and the third pipeline 9 is provided with a circulation pump 10;

The culture bottle 1 is connected with a turbidity sensor 11 for detecting the turbidity of the liquid in the bottle, and a first liquid level sensor 13 for detecting the height of the liquid in the bottle;

The prepacked gas tank 4 is connected with a pressure sensor 14 for detecting the gas pressure in the tank, and a second liquid level sensor 15 for detecting the liquid height in the tank;

The pre-installed gas tank 4 is also provided with a first liquid outlet end 16 and an exhaust end 17; wherein, the first liquid outlet end 16 can control the liquid outlet process and the amount of liquid outlet through a solenoid valve; the exhaust end 17 includes a solenoid valve and a gas metering pump 6 connected with the solenoid valve, which is used to control the exhaust process and exhaust volume of the pre-installed gas tank 4 .

The first electromagnetic valve 18 is used to control the communication relationship between the second pipeline 7 and the third pipeline 9 and each culture bottle 1 respectively;

The second electromagnetic valve 19 is used to control the communication relationship between the pre-installed gas tank 4 and the third pipeline 9;

Wherein, one end of the second pipeline 7 connected to the culture bottle 1 is located above the culture liquid level; the ends of the first pipeline 12 and the third pipeline 9 connected to the culture bottle 1 are located below the culture liquid level. In some preferred embodiments, in order to increase the amount of gas aeration passed into the culture solution, it is considered to install an aeration head 101 at the end of the third pipeline 9 protruding into the culture bottle 1 .

In other preferred embodiments, in order to ensure that the air intake of each culture bottle 1 is consistent, an adjustable damper 21 can be provided on the third pipeline 9 in front of the culture bottle 1 and behind the first solenoid valve 18 .

It should be understood that, in order to collect and process the data of the above-mentioned various sensors, and set the opening and closing of each electromagnetic valve and pump device according to relevant parameters, the present invention should obviously also have a controller capable of realizing the above-mentioned functions. The controller is electrically connected with various sensors, electromagnetic valves and pump devices to realize the control of the entire cultivation process.

The working process and principle of the present embodiment are described as follows:

1. Initial state setting: Calculate the volume of culture solution to be added according to the volume of each culture bottle 1, and set the liquid level detection value of the first liquid level sensor 13 as the corresponding parameter; Calculate the raw material gas volume that needs to be added to the pre-installed gas tank 4, and set the gas flow parameters of the gas metering pump 6 and the parameters of the pressure sensor 14 in the pre-installed gas tank 4; According to the evolution of the cultivation process, the lower limit of the gas concentration that triggers the gas supply is set; the liquid level detection value of the second liquid level sensor 15 is set according to the volume of the pre-installed gas tank 4, to check the pre-installed gas tank 4 When the condensed liquid volume reaches the liquid level detection value of the second liquid level sensor 15, the liquid in the pre-installed gas tank 4 needs to be discharged.

2. The addition of the culture solution: the three-way valve 3 is connected to the second pipeline 7 and the pre-installed gas tank 4, the second solenoid valve 19 is connected, and the first solenoid valve 18 is connected to the second pipeline 7 and the culture bottle 1, Close the third pipeline 9 and the culture bottle 1, open the first liquid outlet 16, and add a preset volume of culture solution to each culture bottle 1 through the liquid inlet and outlet system 2; after the liquid addition is completed, close the first liquid outlet 16.

3. Pressure balance of the gas pipeline: open the exhaust port 17 on the pre-installed gas tank 4, balance the pressure inside and outside the tank, and collect the discharged gas and send it to the next-level processing device or storage device; close the pre-installed gas tank after the balance is completed. The exhaust port 17 on the gas tank 4.

4. Adding raw material gas: close the first solenoid valve 18, the second solenoid valve 19 and the circulation pump 10, the three-way valve 3 leads the gas source 5 and the pre-installed gas tank 4, and the gas metering pump 6 directs the pre-installed gas tank 4 Add the preset raw material gas volume;

5. Gas cycle cultivation: After gas filling is completed, the three-way valve 3 leads to the pre-installed gas tank 4 and the second pipeline 7, opens the second solenoid valve 19, and opens the first solenoid valve 18 to respectively lead to the second pipeline 7 and the third pipeline 9 and each culture bottle 1, start the circulation pump 10, at this moment, the gas will circulate between the culture bottle 1 and the prepacked gas tank 4.

6. Supplementation of raw material gas: when the gas concentration sensor 8 detects that the gas concentration is lower than the preset value, repeat 3-5;

7. Extraction of the culture solution: when the turbidity sensor 11 detects that the turbidity of the culture solution reaches a preset value, the first electromagnetic valve 18 closes the conduction between the second pipeline 7 and each culture bottle 1, and uses the inlet and outlet system 2 to extract A predetermined volume of old culture solution is added, and a corresponding volume of new culture solution is added. After the refilling is completed, the first solenoid valve 18 opens the second pipeline 7 to communicate with each culture bottle 1 .

8. Drainage of condensed water: according to the volume of the pre-installed gas tank 4, set the appropriate height of the condensed water level in the first liquid level sensor 13. When the condensed water in the pre-installed gas tank 4 reaches the preset height, open the second A liquid outlet 16 is used to discharge the condensed water in the tank, so as to prevent the condensed liquid from accumulating too much in the tank.

9. Pressure protection of pre-installed gas tank 4: When the pressure sensor 14 in the pre-installed gas tank 4 detects that the pressure in the tank is greater than the preset value, open the exhaust port 17 on the pre-installed gas tank 4 to balance the pressure inside and outside the tank, and The exhausted gas is collected and sent to the next-level processing device or storage device; after the balance is completed, the exhaust port 17 on the pre-installed gas tank 4 is closed. In some preferred embodiments, in order to prevent overpressure caused by failure of the pressure sensor 14 , a safety valve 20 may also be provided on the pre-installed gas tank 4 .

10. Premix configuration of formula gas: when the cultivation process requires the supply of raw material gas of various components, close the first solenoid valve 18, the second solenoid valve 19 and the circulation pump 10, and the three-way valve 3 leads the gas source 5 and The pre-installed gas tank 4 and the gas metering pump 6 respectively add different types of raw material gases with preset volumes into the pre-installed gas tank 4 to realize the precise configuration of the formula gas.

Example 2

This embodiment is developed on the basis of the above-mentioned embodiment 1, as shown in Figure 2, this embodiment provides a cultivation method based on gas pre-allocation and circulating supply, including:

S1. Add quantitative culture solution to several culture bottles 1 through the liquid inlet and outlet system 2;

S2. The three-way valve 3 connects the pre-installed gas tank 4 and the gas source 5, and adds a certain amount of raw material gas to the pre-installed gas tank 4 through the gas source 5;

S3, the three-way valve 3 conducts the pre-installed gas tank 4 and the second pipeline 7, opens the first solenoid valve 18 and the second solenoid valve 19, starts the circulation pump 10, and makes the gas flow through the pre-installed gas tank 4 and the third pipeline. The sequential circulation flow of road 9, culture bottle 1, second pipeline 7 and three-way valve 3;

S4. When the detection value of the gas concentration sensor 8 reaches a predetermined value, close the circulation pump 10, open the exhaust port 17 and collect the exhaust gas, close the exhaust port 17 when the pressure in the tank returns to atmospheric pressure, and repeat steps S2-S4.

In other preferred embodiments, a specific method for automatically controlling the import and export of old culture fluid and new culture fluid is also provided, including steps:

When the detection value of the turbidity sensor 11 reaches a predetermined value, the first electromagnetic valve 18 is controlled to keep the third pipeline 9 connected with the culture bottle 1, and the connection between the second pipeline 7 and the culture bottle 1 is closed; 2. Export a certain amount of old culture solution, and supplement the same amount of new culture solution; after the supplement is completed, control the first electromagnetic valve 18 to keep the third pipeline 9 and the culture bottle 1 open, and open the second pipeline 7 and the culture bottle 1 conduction.

In other preferred embodiments, a method for controlling the volume of liquid and gas in the pre-packed gas tank 4 is provided, specifically including steps:

When the second liquid level sensor 15 monitors that the liquid level in the pre-installed gas tank 4 reaches a preset level, the liquid in the tank is led out through the first liquid outlet 16; when the pressure sensor 14 monitors that the gas pressure in the pre-installed gas tank 4 reaches When preset, the exhaust port 17 is opened to reduce the pressure in the tank.

Example 3

This embodiment is developed on the basis of the above-mentioned embodiments 1 and 2. The cultivation method and device based on gas pre-allocation and circulation supply provided by the present invention are suitable for the distribution of concentration and ratio of one or more gases , used in the biological culture of bacteria, yeast, edible fungus, algae and other chemical reactions that require mixed gas preparation. Two examples of specific application scenarios are given below:

Application Scenario 1

The cultivation method and device for gas preconfiguration and circulation supply provided by the present invention can be used to prepare single gas with different concentrations for microalgae cultivation. Accurately prepare high-purity carbon dioxide (CO2) gas into different concentrations of 0.04%, 4% and 40%, so that one concentration can be turned on or off within a set time period for the cultivation of microalgae A; Set the requirements, turn on or off within the set time period, and carry out aerated culture of the microalgae culture solution in turn, and finally realize the cyclic supply of CO2 gas, efficient utilization and efficient growth of microalgae.

Application Scenario 2

The cultivation method and device for gas preconfiguration and circulation supply provided by the present invention can be used to mix various gases in proportion for microbial cultivation. Mix high-purity carbon dioxide (CO2) gas and hydrogen (H2) according to the required ratio for the cultivation of bacteria B. Realize the uninterrupted preparation and circulation supply of gas.

The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the industry should understand that the present invention is not limited by the above-mentioned embodiments. What are described in the above-mentioned embodiments and the description only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have Variations and improvements are possible, which fall within the scope of the claimed invention. The protection scope of the present invention is defined by the appended claims and their equivalents.

Claims (7)

1. Culture apparatus based on gas pre-preparation and cyclic supply, characterized by comprising:

a plurality of culture bottles (1) communicated through a first pipeline (12), wherein the first pipeline (12) is also communicated with a liquid inlet and outlet system (2);

the three-way valve (3), the three-way valve (3) is communicated with the preassembled gas tank (4) respectively, is communicated with the gas source (5) through the gas metering pump (6) and is also communicated with the culture flask (1) through the second pipeline (7), and the second pipeline (7) is provided with the gas concentration sensor (8);

the preassembled air tank (4) is also communicated with the culture flask (1) through a third pipeline (9), and a circulating pump (10) is arranged on the third pipeline (9);

the culture bottle (1) is connected with a turbidity sensor (11) for detecting the turbidity of the liquid in the bottle and a first liquid level sensor (13) for detecting the height of the liquid in the bottle;

the preassembled gas tank (4) is connected with a pressure sensor (14) for detecting the gas pressure in the tank and a second liquid level sensor (15) for detecting the liquid level in the tank;

the preassembled gas tank (4) is also provided with a first liquid outlet end (16) and an exhaust end (17);

a first electromagnetic valve (18) for controlling the communication relationship between the second pipeline (7) and the third pipeline (9) and each culture bottle (1);

a second electromagnetic valve (19) for controlling the communication relationship between the preassembled gas tank (4) and the third pipeline (9);

wherein one end of the second pipeline (7) communicated with the culture bottle (1) is positioned above the culture liquid level; one end of the first pipeline (12) and the third pipeline (9) which are communicated with the culture bottle (1) is positioned below the culture liquid level.

2. The gas-based pre-and recirculating feed culture device of claim 1, wherein: the liquid inlet and outlet system (2) comprises a liquid inlet end (201) and a second liquid outlet end (202) which are respectively parallel and communicated with the first pipeline (12); the liquid inlet end (201) and the second liquid outlet end (202) are respectively provided with an electromagnetic valve and a liquid metering pump (22).

3. The gas-based pre-and recirculating feed culture device of claim 1, wherein: one end of the third pipeline (9) extending into the culture flask (1) is provided with an aeration head (101).

4. The gas-based pre-and recirculating feed culture device of claim 1, wherein: an adjustable damper (21) is arranged on the third pipeline (9) in front of the culture bottle (1) and behind the first electromagnetic valve (18).

5. A culture method based on gas preparation and circulation supply by using the culture apparatus according to any one of claims 1 to 4, comprising:

s1, respectively adding quantitative culture solution into a plurality of culture bottles (1) through a liquid inlet and outlet system (2);

s2, a three-way valve (3) is used for conducting the preassembled air tank (4) and the air source (5), and quantitative raw material gas is added into the preassembled air tank (4) through the air source (5);

s3, a three-way valve (3) is used for conducting the preassembled gas tank (4) and the second pipeline (7), a first electromagnetic valve (18) and a second electromagnetic valve (19) are opened, and a circulating pump (10) is started to enable gas to circulate and flow in the order of the preassembled gas tank (4), the third pipeline (9), the culture bottle (1), the second pipeline (7) and the three-way valve (3);

s4, when the detection value of the gas concentration sensor (8) reaches a preset value, the circulating pump (10) is closed, the exhaust end (17) is opened, exhaust gas is collected, when the pressure in the tank is restored to the atmospheric pressure, the exhaust end (17) is closed, and the steps S2-S4 are repeatedly executed.

6. The gas-pre-mixing and circulation-feed-based cultivation method according to claim 5, further comprising the steps of:

when the detection value of the turbidity sensor (11) reaches a preset value, the first electromagnetic valve (18) is controlled to keep conducting the third pipeline (9) and the culture flask (1), and the second pipeline (7) is closed to conduct the culture flask (1); a fixed amount of old culture solution is led out through a liquid inlet and outlet system (2), and the same amount of new culture solution is supplemented; after the supplement is finished, the first electromagnetic valve (18) is controlled to keep conducting the third pipeline (9) and the culture flask (1), and the second pipeline (7) is opened to conduct with the culture flask (1).

7. The gas-pre-mixing and circulation-feed-based cultivation method according to claim 5, further comprising the steps of:

when the second liquid level sensor (15) monitors that the liquid level in the preassembled gas tank (4) reaches the preset level, the liquid in the tank is led out through the first liquid outlet end (16); when the pressure sensor (14) detects that the gas pressure in the preassembled gas tank (4) reaches a preset value, the exhaust end (17) is opened to reduce the pressure in the tank.

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