Method for separating and purifying fidaxomicin by using double-column switching circulating chromatographic system

Abstract

The invention relates to a method for separating and purifying fidaxomicin by using a double-column switching circulating chromatographic system. The double-column switching circulating chromatographic system adopted by the scheme consists of a first chromatographic column, a second chromatographic column and a valve assembly, the first chromatographic column, the second chromatographic column and the valve assembly are connected through a pipeline, and the first chromatographic column and the second chromatographic column are filled with C8 reverse phase silica gel; the double-column circulating chromatography system is used for separating and purifying fidaxomicin raw materials, single impurities in the product can be controlled to be within 0.1%, the requirement for the product component content of the raw materials is low, and the purity gt of the finally collected product can be achieved; the yield is 99.5%, and the yield is more than 60%; the method effectively overcomes the defects of existing schemes such as crystallization, recrystallization, nanofiltration and the like.

Description

Technical Field

[0001] The patent of this invention relates to the technical field of chromatographic separation and purification, and specifically to a method for separating and purifying fidaxomicin using a double-column switching circulating chromatography system. Background Art

[0002] Fidaxomicin (CAS registration number 873857-62-6, chemical formula C 52 H 74 Cl2O 18 Fidaxomicin is a macrolide antibiotic with a novel mechanism of action. It selectively inhibits the RNA polymerase of Clostridium difficile, preventing bacterial DNA transcription and protein synthesis, thereby effectively reducing diarrheal symptoms and recurrence rates caused by C. difficile. This unique mechanism of action minimizes disruption to normal intestinal flora and helps maintain intestinal microecological balance.

[0003] In clinical use, the pharmacopoeia has high requirements for the purity of fidaxomicin and also sets limits on the content of single impurities. Currently available fidaxomicin purification methods, such as crystallization, recrystallization, and nanofiltration, all have some shortcomings. On the one hand, they have high requirements for raw materials (such as high purity requirements for raw materials, generally requiring at least 95% or more), and on the other hand, it is difficult to control the single impurities in the product to meet the requirements (single impurities are required to be within 0.1%. Since the properties of impurities are similar to those of the target substance, it is difficult to control each impurity within 0.1% with these existing methods). Industrial-scale chromatographic separation can produce products that meet the quality requirements, but due to the use of a single-column flushing mode, the sample load is small and the product concentration is dilute, resulting in high production costs. Therefore, it is of great significance to study an efficient and low-cost chromatographic purification process for fidaxomicin. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for separating and purifying fidaxomicin using a dual-column switching circulation chromatography system, which does not require high raw material purity and can control single impurities within 0.1%, and is suitable for large-scale production of fidaxomicin.

[0005] In order to solve the above technical problems, the present application adopts the following technical solution: a method for separating and purifying fidaxomicin using a dual-column switching circulating chromatography system, wherein the dual-column switching circulating chromatography system used in the method comprises a first chromatographic column, a second chromatographic column, and a valve assembly; the first chromatographic column, the second chromatographic column, and the valve assembly are connected by a pipeline, and the first chromatographic column and the second chromatographic column are both filled with C8 reverse-phase silica gel (also known as octaalkylsilane bonded silica gel, i.e., octyl group is chemically bonded to the surface of the silica gel);

[0006] The specific separation and purification steps include:

[0007] (1) Feeding: dissolving the raw material in a mixed solvent of acetonitrile and / or methanol and water to prepare a raw material solution, and flowing the obtained raw material solution into the chromatography system from the inlet of the first chromatography column;

[0008] (2) Circular elution: the eluent is flowed into the chromatographic system from the inlet of the first chromatographic column to elute the fidaxomicin concentration band from the first chromatographic column to the second chromatographic column; after a certain period of time, the valve of the system is switched, and the eluent is flowed into the chromatographic system from the inlet of the second chromatographic column to elute the fidaxomicin concentration band from the second chromatographic column to the first chromatographic column; after a certain period of time, the valve of the system is switched again, and the eluent is flowed into the chromatographic system from the inlet of the first chromatographic column to elute the fidaxomicin concentration band from the first chromatographic column to the second chromatographic column; the switching is repeated in this way. The first cycle is from the end of feeding to the moment of the first switching, the second cycle is from the end of the first switching to the moment of the start of the second switching, and so on. The time from the end of the (n-1)th switching to the start of the nth switching is the nth cycle; in each cycle, the fidaxomicin concentration band is always eluted from the upstream chromatographic column to the downstream chromatographic column, and then switched to the upstream to start the next cycle; in the last cycle, after the fidaxomicin concentration band is eluted from the upstream to the downstream, the system is no longer switched, but enters the product collection step;

[0009] (3) Product collection: elution chromatography system, collecting qualified fidaxomicin fractions from the outlet of the downstream chromatographic column, and / or

[0010] The valve of the system was switched to switch the fidaxomicin band upstream and the qualified fidaxomicin fraction was collected from the outlet of the upstream column.

[0011] Furthermore, the eluent is a mixed solvent of acetonitrile and / or methanol and water, the volume percentage of methanol and / or acetonitrile in the mixed solvent is less than 80%, and the volume percentage of water is greater than 20%.

[0012] Furthermore, the mass percentage of fidaxomicin in the fidaxomicin raw material is not less than 50%.

[0013] Furthermore, the fidaxomicin raw material solution is in a saturated state.

[0014] Furthermore, the feed volume of the fidaxomicin raw material solution is 0.5-1.5 times the column volume.

[0015] Furthermore, the eluent flow rate is set according to the system pressure so that the system pressure does not exceed 7 MPa.

[0016] Furthermore, in the process of the fidaxomicin concentration spectrum band flowing from the upstream chromatographic column to the downstream chromatographic column, a modifier with a water content higher than that of the eluent is added between the two chromatographic columns (to keep the elution ability of the modifier weaker than that of the eluent), and the flow rate of the modifier is 1.5-10% of the eluent flow rate.

[0017] Furthermore, the modifier is water or a modifier in which the water content is higher than that of the eluent.

[0018] Furthermore, detectors are connected to the tails of the two chromatographic columns to monitor the movement of the fidaxomicin concentration band; specifically, the detector at the tail of the upstream chromatographic column is used to monitor the trailing edge of the band flowing out of the upstream chromatographic column, and the detector at the tail of the downstream chromatographic column is used to monitor the leading edge of the band leaking out of the downstream chromatographic column.

[0019] Furthermore, during the elution of the fidaxomicin band from the upstream chromatographic column to the downstream chromatographic column, the upstream chromatographic column and the downstream chromatographic column are connected, and the waste liquid is discharged from the downstream chromatographic column.

[0020] Furthermore, during the time when the non-fidaxomicin band is eluted from the upstream chromatographic column to the downstream chromatographic column, the upstream chromatographic column and the downstream chromatographic column are not connected, and the waste liquid is directly discharged from the outlet of the upstream chromatographic column; that is, when the main fidaxomicin band has not yet flowed out of the upstream column, or after the main fidaxomicin band has flowed out of the upstream column, the waste liquid can be directly discharged from the outlet end of the upstream chromatographic column.

[0021] Advantages and beneficial effects of this application:

[0022] 1. This application is the first to use a dual-column circulating chromatography system to separate and purify fidaxomicin raw materials. This combination can increase the equivalent column length and the number of plates in the chromatographic separation process without increasing the system pressure, thereby improving product purity and yield while maintaining system stability.

[0023] 2. This application uses a dual-column circulating chromatography system to separate and purify the fidaxomicin raw material. During the separation process, a modifier is added to effectively inhibit the broadening of the fidaxomicin band, so that the target component is repeatedly enriched, which is more conducive to purification and separation from impurities, thereby improving the separation purity of the product.

[0024] 3. The present application adopts a double-column circulation chromatography system to separate and purify the raw material of fidaxomicin. The product separated by this method, wherein the content of fidaxomicin in the raw material of fidaxomicin is not less than 50%, while the existing technologies such as crystallization, recrystallization and nanofiltration have higher requirements on the purity of the raw material, generally requiring at least 95% or more. Obviously, the present application can separate raw materials with lower purity; In addition, the present application adopts a double-column circulation chromatography system to purify and separate the raw material of fidaxomicin, which can control the single impurity in the product to be within 0.1%; and since the properties of the impurities in the raw material of fidaxomicin are similar to those of the target substance, these existing technologies are not suitable for separation. It is difficult to control each impurity within 0.1% by the method; the present application achieves the above technical effects by adding a modifier and regulating the sequence of impurity separation in the chromatographic column. For example, during the process of eluting the fidaxomicin band from the upstream chromatographic column to the downstream chromatographic column, the upstream chromatographic column and the downstream chromatographic column are connected, and the waste liquid is discharged from the downstream chromatographic column; during the time when the non-fidaxomicin band is eluted from the upstream chromatographic column to the downstream chromatographic column, that is, when the main fidaxomicin band has not yet flowed out of the upstream column, or after the main fidaxomicin band has flowed out of the upstream column, the upstream chromatographic column and the downstream chromatographic column are not connected, and the waste liquid is directly discharged from the outlet of the upstream chromatographic column. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a structural schematic diagram of the first state of the dual-column circulating chromatographic separation system of the present application (the two chromatographic columns are connected, and the first chromatographic column is the upstream chromatographic column).

[0026] Figure 2 This is a structural schematic diagram of the second state of the dual-column circulating chromatographic separation system of the present application (the two chromatographic columns are connected, and the second chromatographic column is the upstream chromatographic column).

[0027] Figure 3 This is a structural diagram of the third state of the dual-column circulating chromatographic separation system of the present application (the two chromatographic columns are disconnected, and the waste liquid is discharged from the outlet of the first chromatographic column).

[0028] Figure 4 This is a structural diagram of the fourth state of the dual-column circulating chromatographic separation system of the present application (the two chromatographic columns are disconnected, and the waste liquid is discharged from the outlet of the second chromatographic column).

[0029] As shown in the figure, 1. first chromatographic column, 2. second chromatographic column, V. valve assembly, 3. pipeline, V1. first switching valve, V2. second switching valve, V3. sample collection valve, 4. elution pump, 5. raw material pump, 6. modification pump, D1. first detector, D2. second detector.

[0030] Figure 5 This is a high performance liquid chromatogram of the raw material solution used in the examples of this application.

[0031] Figure 6 HPLC chromatogram of the product collected in Example 1.

[0032] Figure 7 HPLC chromatogram of the product collected in Example 2.

[0033] Figure 8 HPLC chromatogram of the product collected in Example 3. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is described in detail below. On the reversed-phase silica gel column, the peak order of each component in the fidaxomicin raw material is the first impurity, fidaxomicin and the last impurity. The specific high-performance liquid phase analysis spectrum can be found in the attached Figure 5 Fidaxomicin was separated from the crude product of Fidaxomicin by using the double-column circulating chromatography separation method proposed in the present invention.

[0035] 1. Double column circulation chromatography separation system

[0036] The double column circulation chromatography separation system used in this application is as shown in the attached Figures 1-4As shown, the system includes a first chromatographic column 1, a second chromatographic column 2 and a valve assembly V; the first chromatographic column 1, the second chromatographic column 2 and the valve assembly V are connected by a pipeline 3, and the first chromatographic column 1 and the second chromatographic column 2 are both filled with C8 reverse phase silica gel; more specifically, the valve assembly V of the present application includes at least three valve assemblies, namely a first switching valve V1, a second switching valve V2 and a sample collection valve V3; wherein the two liquid outlets of the first switching valve V1 are respectively connected to the inlet ends of the first chromatographic column 1 and the second chromatographic column 2 to control the inflow position of the eluent, and the two liquid inlets of the second switching valve V2 are respectively connected to the outlet ends of the first chromatographic column and the second chromatographic column to selectively receive the effluent of column 1 (first chromatographic column) or column 2 (second chromatographic column); one liquid outlet of the second switching valve V2 is connected to a liquid inlet of the first switching valve, and the other liquid outlet is connected to the liquid inlet of the sample collection valve V3; it also includes at least three pumps, namely an elution pump 4, a raw material pump 5 and a modification pump 6, wherein the eluent The outlets of the desorption pump 4 and the raw material pump 5 are connected to the remaining liquid inlet of the first switching valve via a three-way joint, and are used for pumping in the eluent and the raw material liquid respectively. The modification pump 6 is used for pumping in the modifier, wherein the modification pump 6 is located on the pipeline 3 between the first switching valve V1 and the second switching valve V2; detectors are also provided on the pipelines at the outlet ends of the first chromatographic column 1 and the second chromatographic column 2, specifically, the first detector D1 is located on the pipeline at the outlet end of the first chromatographic column 1, and the second detector D2 is located on the pipeline at the outlet end of the second chromatographic column 2; specifically, the sample collection valve V3 is a multi-position selection valve, more specifically, the sample collection valve V3 has five ports, one of which is a liquid inlet, which is always connected to a liquid outlet of the second switching valve V2, and the remaining four ports are liquid outlets, which are selectively connected to the liquid inlet of the sample collection valve V3; by adopting this multi-position selection valve, the connected ports can be automatically selected according to time to achieve the purpose of segmented collection of the effluent.

[0037] like Figures 1-4 As shown, the elution pump 4 delivers a mixed solvent of methanol and / or acetonitrile and water, the feed pump delivers the raw material solution, and the modifier pump delivers the modifier. The first switching valve V1 and the second switching valve V2 are periodically switched to change the eluent and modifier addition locations. When recovering the product, the sample collection valve V3 is switched to collect the product bands in sections. By taking appropriate measures, this separation system can implement the dual-column chromatography separation method for separating and purifying fidaxomicin proposed in this application.

[0038] 2. Separation Steps

[0039] (1) Feeding: dissolving the fidaxomicin raw material in acetonitrile and / or a mixed solvent of methanol and water to prepare a raw material solution, which is then introduced into the system from the inlet of the first chromatographic column;

[0040] (2) Circular elution: The eluent (acetonitrile and / or methanol mixed with water) flows into the system from the inlet of the first chromatographic column, eluting the fidaxomicin concentration band from the first chromatographic column to the second chromatographic column; after a certain period of time, the system switches, and the eluent flows into the system from the inlet of the second chromatographic column, eluting the fidaxomicin concentration band from the second chromatographic column to the first chromatographic column; after a certain period of time, the system switches again, and the eluent flows into the system from the inlet of the first chromatographic column, eluting the fidaxomicin concentration band from the first chromatographic column to the second chromatographic column; and so on. The time from the end of the feed to the moment of the first switch is the first cycle, and the time from the end of the first switch to the moment of the second switch is the second cycle. Similarly, the time from the end of the (n-1)th switch to the start of the nth switch is the nth cycle. In each cycle, the fidaxomicin concentration band is always eluted from the upstream chromatographic column to the downstream chromatographic column, and then switches to the upstream to start the next cycle. In the last cycle, after the fidaxomicin concentration band is eluted from the upstream to the downstream, the system is no longer switched, but enters the product collection step.

[0041] (3) Product collection: elution system, collecting qualified fidaxomicin fractions from the downstream chromatographic column outlet

[0042] and / or

[0043] Switch the system, switch the fidaxomicin band to the upstream, and collect qualified fidaxomicin fractions from the outlet of the upstream column.

[0044] 3. Finished product inspection

[0045] The product purity was analyzed by high-performance liquid chromatography. Liquid chromatography conditions: Waters XBridge column (4.6 mm × 250 mm, 5 μm), detection wavelength 228 nm, column temperature 40°C. Mobile phase: water / methanol / acetonitrile (56 / 14 / 30, v / v / v).

[0046] The present invention is further illustrated below by means of specific examples. In the examples, the first and second chromatographic columns used in dual-column circulation chromatography had a diameter of 1 cm and a length of 25 cm, and were filled with commercially available C8 reverse-phase silica gel with a particle size of 10 μm. The eluent was a mixture of methanol and acetonitrile in water in a certain ratio. Fidaxomicin raw material was dissolved in the eluent to produce a raw material solution with a concentration of approximately 20 mg / mL.

[0047] Example 1

[0048] The stock liquid sample volume is 15mL, and the above-mentioned stock liquid is first pumped into the system; the eluent is methanol / acetonitrile / water (volume ratio 30 / 30 / 40), the flow rate is 4mL / min, the modifier is water, the flow rate is 0.2mL / min, and the above-mentioned eluent and modifier enter the double-column chromatography system with the above-mentioned respective flow rates. Under this flow rate, the total pressure of the double-column chromatography system is 5MPa; the switching cycle is 15min, and a total of 7 switches are made; finally, the fractions are collected to obtain qualified fidaxomicin, and the collected product is detected. The specific high performance liquid chromatogram corresponding to the product obtained in Example 1 is shown in the attached figure. Figure 6 It can be seen that the purity of the separated product collection is>99.5%, the content of any single impurity is less than 0.1%, and the yield is 75%; the diagram of the chromatographic system corresponding to this embodiment is shown in the attached figure. Figures 1-4 As shown in FIG, the chromatographic column that the eluent first enters each time is the upstream chromatographic column, and the chromatographic column that the eluent enters next is the downstream chromatographic column; as shown in FIG. Figure 1 As shown in the figure, in this state, the first chromatographic column is the upstream chromatographic column, and the second chromatographic column is the downstream chromatographic column. Figure 2 As shown, in this state, the first chromatographic column is the downstream chromatographic column, and the second chromatographic column is the upstream chromatographic column; Figures 1-2 Both are states where the two chromatographic columns are connected; Figure 3 The upstream chromatographic column and the downstream chromatographic column are not connected, and the waste liquid is directly discharged from the outlet of the upstream chromatographic column (the first chromatographic column). Figure 4 This is a state where the upstream column and the downstream column are not connected, and the waste liquid is directly discharged from the outlet of the upstream column (the second column).

[0049] Example 2

[0050] The loading volume of the raw material liquid is 20mL, and the above raw material liquid is pumped into the system first. The eluent is methanol / water (volume ratio 70 / 30), the flow rate is 3mL / min, the modifier is water, the flow rate is 0.15mL / min, and the above eluent and modifier enter the double-column chromatography system with the above-mentioned respective flow rates; at this flow rate, the total pressure of the system is 4.5MPa; the switching cycle is 16min, and a total of 7 switches are made. Finally, the fractions are collected to obtain qualified Fidaxomicin. By detecting the collected products, the specific high-performance liquid chromatogram corresponding to the product obtained in Example 2 is shown in the attached figure. Figure 7 It can be seen that the purity of the separated product collection is>99.5%, the content of any single impurity is less than 0.1%, and the yield is 60%; the diagram of the chromatographic system corresponding to this embodiment is shown in the attached figure. Figures 1-4 As shown in FIG, the chromatographic column that the eluent first enters each time is the upstream chromatographic column, and the chromatographic column that the eluent enters next is the downstream chromatographic column; as shown in FIG. Figure 1 As shown in the figure, in this state, the first chromatographic column is the upstream chromatographic column, and the second chromatographic column is the downstream chromatographic column. Figure 2As shown, in this state, the first chromatographic column is the downstream chromatographic column, and the second chromatographic column is the upstream chromatographic column; Figures 1-2 Both are states where two chromatographic columns are connected; Figure 3 The upstream chromatographic column and the downstream chromatographic column are not connected, and the waste liquid is directly discharged from the outlet of the upstream chromatographic column (the first chromatographic column). Figure 4 This is a state where the upstream column and the downstream column are not connected, and the waste liquid is directly discharged from the outlet of the upstream column (the second column).

[0051] Example 3

[0052] The raw material liquid sample volume is 15mL, and the above-mentioned raw material liquid is first pumped into the system. The eluent is acetonitrile / water (volume ratio 60 / 40), the flow rate is 4mL / min, the modifier is water, the flow rate is 0.2mL / min, and the above-mentioned eluent and modifier enter the double-column chromatography system with the above-mentioned respective flow rates. Under this flow rate, the total system pressure is 3.5MPa; the switching cycle is 17min, and a total of 9 switches are made. Finally, the fractions are collected to obtain qualified Fidaxomicin. The products collected are detected, and the HPLC chromatogram corresponding to the products obtained in the specific embodiment 3 is shown in the attached figure. Figure 8 It can be seen that the purity of the separated product collection is>99.5%, the content of any single impurity is less than 0.1%, and the yield is 70%; the diagram of the chromatographic system corresponding to this embodiment is shown in the attached figure. Figures 1-4 As shown in FIG, the chromatographic column that the eluent first enters each time is the upstream chromatographic column, and the chromatographic column that the eluent enters next is the downstream chromatographic column; as shown in FIG. Figure 1 As shown in the figure, in this state, the first chromatographic column is the upstream chromatographic column, and the second chromatographic column is the downstream chromatographic column. Figure 2 As shown, in this state, the first chromatographic column is the downstream chromatographic column, and the second chromatographic column is the upstream chromatographic column; Figures 1-2 Both are states where two chromatographic columns are connected; Figure 3 The upstream chromatographic column and the downstream chromatographic column are not connected, and the waste liquid is directly discharged from the outlet of the upstream chromatographic column (the first chromatographic column). Figure 4 This is a state where the upstream column and the downstream column are not connected, and the waste liquid is directly discharged from the outlet of the upstream column (the second column).

[0053] It can be seen from the test results of the above embodiments that Figures 1-4 This dual-column circulating chromatography system separates and purifies fidaxomicin raw materials, can control the single impurity content in the product to within 0.1%, and the product component content of the raw materials is required to be low. The purity of the final collected product can be achieved to be greater than 99.5%, with a yield of more than 60%. It effectively overcomes some shortcomings of existing solutions such as crystallization, recrystallization and nanofiltration.

Claims

1. A method for separating and purifying fidaxomicin using a dual-column switching circulation chromatography system, characterized in that: The dual-column switching circulation chromatography system used consists of a first chromatographic column, a second chromatographic column and a valve assembly; the first chromatographic column, the second chromatographic column and the valve assembly are connected by a pipeline, and the first chromatographic column and the second chromatographic column are both filled with C8 reverse phase silica gel; The specific separation and purification steps include: (1) Feeding: dissolving the raw material in a mixed solvent of acetonitrile and / or methanol and water to prepare a raw material solution, and flowing the obtained raw material solution into the chromatography system from the inlet of the first chromatography column; (2) Circular elution: the eluent is flowed into the chromatographic system from the inlet of the first chromatographic column to elute the fidaxomicin concentration band from the first chromatographic column to the second chromatographic column; after a certain period of time, the valve of the system is switched, and the eluent is flowed into the chromatographic system from the inlet of the second chromatographic column to elute the fidaxomicin concentration band from the second chromatographic column to the first chromatographic column; after a certain period of time, the valve of the system is switched again, and the eluent is flowed into the chromatographic system from the inlet of the first chromatographic column to elute the fidaxomicin concentration band from the first chromatographic column to the second chromatographic column; The switching is repeated in this way. The first cycle is from the end of feeding to the moment of the first switching, the second cycle is from the end of the first switching to the moment of the start of the second switching, and so on. The time from the end of the (n-1)th switching to the start of the nth switching is the nth cycle. In each cycle, the fidaxomicin concentration band is always eluted from the upstream chromatographic column to the downstream chromatographic column, and then switched to the upstream to start the next cycle. In the last cycle, after the fidaxomicin concentration band is eluted from the upstream to the downstream, the system is no longer switched, but enters the product collection step. (3) Product collection: elution chromatography system, collect qualified fidaxomicin fractions from the outlet of the downstream chromatographic column, and / or The valve of the system was switched to switch the fidaxomicin band upstream and the qualified fidaxomicin fraction was collected from the outlet of the upstream column.

2. The method for separating and purifying fidaxomicin using a dual-column switching circulation chromatography system according to claim 1, characterized in that: The eluent is a mixed solvent of acetonitrile and / or methanol and water, wherein the volume percentage of methanol and / or acetonitrile is less than 80%, and the volume percentage of water is greater than 20%.

3. The method for separating and purifying fidaxomicin using a dual-column switching circulation chromatography system according to claim 1, characterized in that: The mass percentage of fidaxomicin in the fidaxomicin raw material is not less than 50%.

4. The method for separating and purifying fidaxomicin using a dual-column switching circulation chromatography system according to claim 1, characterized in that: The raw material solution of fidaxomicin is a saturated solution.

5. The method for separating and purifying fidaxomicin using a dual-column switching circulation chromatography system according to claim 1, characterized in that: The feed volume of the fidaxomicin raw material solution is 0.5-1.5 times the column volume.

6. The method for separating and purifying fidaxomicin using a dual-column switching circulation chromatography system according to claim 1, characterized in that: The flow rate of the eluent is set according to the system pressure, and the system pressure does not exceed 7 MPa.

7. The method for separating and purifying fidaxomicin using a dual-column switching circulation chromatography system according to claim 1, characterized in that: When the fidaxomicin concentration band flows from the upstream chromatographic column to the downstream chromatographic column, a modifier having a higher water content than the eluent is added between the two chromatographic columns, and the flow rate of the modifier is 1.5-10% of the eluent flow rate.

8. The method for separating and purifying fidaxomicin using a dual-column switching circulation chromatography system according to claim 1, characterized in that: The tails of the two chromatographic columns are respectively connected to detectors for monitoring the movement of the fidaxomicin concentration band; specifically, the detector at the tail of the upstream chromatographic column is used to monitor the trailing edge of the band flowing out of the upstream chromatographic column, and the detector at the tail of the downstream chromatographic column is used to monitor the leading edge of the band leaking out of the downstream chromatographic column.

9. The method for separating and purifying fidaxomicin using a dual-column switching circulation chromatography system according to claim 1, characterized in that: During the process of eluting the fidaxomicin band from the upstream chromatographic column to the downstream chromatographic column, the upstream chromatographic column and the downstream chromatographic column are connected, and the waste liquid is discharged from the outlet of the downstream chromatographic column.

10. The method for separating and purifying fidaxomicin using a dual-column switching circulation chromatography system according to claim 1, characterized in that: During the time when the non-fidaxomicin band is eluted from the upstream chromatographic column to the downstream chromatographic column, the upstream chromatographic column and the downstream chromatographic column are not connected, and the waste liquid is directly discharged from the outlet of the upstream chromatographic column.

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