Tangential flow filtration system and method

Abstract

A tangential flow filtration system and method are disclosed. The system includes a tangential flow filtration device, an inlet pump in fluid communication with an inlet of the tangential flow filtration device, and a backflow control device in fluid communication with a backflow port of the tangential flow filtration device.

Description

Technical Field

[0001] This application relates to a tangential flow filtration system and method. The system and method of this application are robust, easy to operate and scale up, and can achieve stable volumetric concentration factors. Background Technology

[0002] Tangential flow filtration (SFL) is a membrane separation process that separates target products based on molecular weight, molecular size, and other characteristics. In traditional SFL, the fermentation broth is circulated back to the inlet storage tank through a reflux port during concentration. The permeate end continuously filters out fermentation broth free of the target protein to achieve the set volumetric concentration factor. This process requires increasing the transmembrane pressure (TMP) to improve concentration efficiency. However, the shear forces on the pump and membrane surface affect the stability of the target product over a long period. To address this, single-pass tangential flow filtration (SP-TFF) increases the retention time between the fermentation broth and the membrane by extending the channel length, achieving the set volumetric concentration factor at a relatively lower transmembrane pressure. Compared to traditional SFL systems, SP-TFF is suitable for continuous flow processes, reduces the scale of storage tanks required for production scale-up, and minimizes the impact of the circulation system on protein stability.

[0003] However, single-pass tangential flow filtration still presents problems. For example, based on the Millipore SP-TFF device, during the concentration of fermentation broth through single-pass tangential flow filtration, the increase in transmembrane pressure manifests as an increase in both the inlet and reflux pressures. For pressure control, the increase in reflux pressure leads to a decrease in the volumetric concentration factor as the pressure increases. To maintain stable transmembrane pressure and volumetric concentration factor, Xiao Zhe (Research on Tangential Flow and Transmembrane Pressure Control of Hollow Fiber Ultrafiltration Membrane System, Guangdong Chemical Industry, 2011, Vol. 38, No. 8, Serial No. 220) proposed installing a pressure sensor at both the reflux port and the permeate port to calculate the system's transmembrane pressure. A pneumatic regulating valve is then installed at the reflux port, and the required transmembrane pressure value is obtained by adjusting the opening of this valve. However, if a regulating valve or flow-limiting valve is used to control and adjust the reflux port pressure to maintain a stable volumetric concentration factor, continuous adjustment and monitoring are required throughout the process, making the operation complex. This results in unstable volumetric concentration factors, hindering scale-up production and optimization of process parameters. During the concentration of fermentation broth, as the sample loading amount increases, complex components in the fermentation broth will form an adsorption layer on the membrane surface, thereby reducing the system flux under unit pressure and thus affecting the stability of the volume concentration factor.

[0004] In addition, water flux testing is required before tangential flow filtration. For multi-stage ultrafiltration membrane packs, existing technologies involve changing the flow path (converting from series to parallel) or separating each membrane stage and testing the water flux of each stage separately. Such water flux testing is cumbersome and inefficient.

[0005] Clearly, there is still a need in the art for a robust, easy-to-operate, and scalable tangential flow filtration system and method that yields stable transmembrane pressure and volumetric concentration factor. Simultaneously, there is still a need in the art for an efficient / convenient method for testing water flux in large-scale tangential flow filtration production. Summary of the Invention

[0006] To address the aforementioned technical problems, one aspect of this application provides a tangential flow filtration system, comprising a tangential flow filtration device, an inlet pump communicating with the inlet fluid of the tangential flow filtration device, and a return flow control device communicating with the return flow port fluid of the tangential flow filtration device.

[0007] In one embodiment of this application, the reflux control device includes a reflux pump and / or a reflux end valve. In another embodiment, the reflux control device includes a reflux pump and a reflux end valve, which are connected in parallel or interchangeable. In yet another embodiment, the reflux control device includes either a reflux pump or a reflux end valve, which are interchangeable. In one embodiment, the switching between the reflux pump and the reflux end valve is achieved by adjusting the pipeline connectivity. In one embodiment, the reflux pump and the reflux end valve are connected in parallel, and liquid flow is controlled by opening, adjusting, or closing the reflux pump and / or the reflux end valve. In one embodiment, the interchangeability of the reflux pump and the reflux end valve is a physical replacement, including, for example, disassembly and installation. In one embodiment, the tangential flow filtration system further includes a liquid storage device in fluid communication with the inlet pump and a collection device in fluid communication with the reflux control device. In one embodiment, the liquid storage device is a storage bottle or a storage tank. In one embodiment of this application, the collection device is a collection bottle or collection tank. In one embodiment of this application, the storage device contains a liquid selected from the following: sample and buffer solution. In one embodiment of this application, the sample is a perfused culture sample. In one embodiment of this application, the sample is a protein solution. In one embodiment of this application, the protein is an antibody. In one embodiment of this application, the antibody is a monoclonal antibody. In one embodiment of this application, the sample is fermentation broth supernatant. In another embodiment of this application, the fermentation broth supernatant is selected from animal cell fermentation broth supernatant, plant cell fermentation broth supernatant, or microbial cell fermentation broth supernatant. In another embodiment of this application, the fermentation broth supernatant is the fermentation broth supernatant of Chinese hamster ovary cells or mouse myeloma cells integrated with exogenous genes. In another embodiment of this application, the fermentation broth supernatant is selected from: cell culture supernatant after batch fed-batch culture and clarification process, or cell culture filtrate after perfusion culture. In one embodiment of this application, the buffer solution is selected from equilibration buffer, regeneration buffer, rinsing buffer, disinfection buffer, or preservation solution.

[0008] In one embodiment of this application, the tangential flow filtration device is a single-pass tangential flow filtration device. In one embodiment of this application, the tangential flow filtration device includes one or more ultrafiltration membrane packages. In one embodiment of this application, the tangential flow filtration device includes multiple ultrafiltration membrane packages connected in series. In one embodiment of this application, the tangential flow filtration device includes three ultrafiltration membrane packages connected in series. In one embodiment of this application, the membrane ratio of the three ultrafiltration membrane packages is 1:1:1. In one embodiment of this application, the inlet pump and the return pump are independently selected from diaphragm pumps or peristaltic pumps. In another embodiment of this application, the inlet pump is a diaphragm pump and the return pump is a peristaltic pump. In one embodiment of this application, the return valve is a regulating valve. In one embodiment of this application, the return valve is a pressure valve.

[0009] Another aspect of this application provides a method for determining tangential flow filtration parameters, comprising: a) determining an upper limit for the transmembrane pressure of a first-stage membrane; b) constructing a tangential flow filtration system, including a tangential flow filtration device, an inlet pump in fluid communication with the inlet of the tangential flow filtration device, and a reflux control device in fluid communication with the reflux port of the tangential flow filtration device; c) determining an upper limit for the inlet flux; and d) determining an upper limit for the volumetric concentration factor.

[0010] In one embodiment of this application, the upper limit of the first-stage membrane transmembrane pressure is determined based on the system steady state. In one embodiment of this application, the system steady state is a condition that avoids severe polarization of the membrane surface, which could lead to changes in permeate flux. In one embodiment of this application, determining the upper limit of the first-stage membrane transmembrane pressure includes determining the maximum first-stage membrane transmembrane pressure achievable before polarization occurs in the first-stage membrane. In one embodiment of this application, the upper limit of the first-stage membrane transmembrane pressure varies with differences in the tangential flow filtration device and the sample being processed. In one embodiment of this application, the upper limit of the first-stage membrane transmembrane pressure is 12 psi. In one embodiment of this application, determining the upper limit of the first-stage membrane transmembrane pressure further includes constructing a tangential flow filtration system including a tangential flow filtration device comprising a first-stage membrane. In one embodiment of this application, the first-stage membrane in step a) is the same as the first-stage membrane in the tangential flow filtration device in step b). In one embodiment of this application, the tangential flow filtration system further includes an inlet pump in fluid communication with the inlet of the tangential flow filtration device, and a reflux control device in fluid communication with the reflux port of the tangential flow filtration device. In one embodiment of this application, the reflux control device includes a reflux end valve.

[0011] In one embodiment of this application, the upper limit of the inlet flux is determined based on the actual system load and the upper limit of the first-stage membrane transmembrane pressure. In another embodiment of this application, the upper limit of the inlet flux is determined based on the maximum inlet flux determined to maintain a stable system state. In yet another embodiment of this application, determining the upper limit of the inlet flux includes determining the maximum inlet flux that achieves the actual system load at a fixed volumetric concentration factor, without exceeding the upper limit of the first-stage membrane transmembrane pressure.

[0012] In one embodiment of this application, the upper limit of the volumetric concentration factor is determined based on the actual system load and the upper limit of the first-stage membrane transmembrane pressure. In another embodiment, the upper limit of the volumetric concentration factor is determined based on the maximum volumetric concentration factor determined to maintain a stable system state. In another embodiment, determining the upper limit of the volumetric concentration factor includes determining the maximum volumetric concentration factor that achieves the actual system load at a fixed inlet flux, without exceeding the upper limit of the first-stage membrane transmembrane pressure. In another embodiment, the lower limit of the volumetric concentration factor is also determined. In one embodiment, the lower limit of the volumetric concentration factor is determined based on large-scale production requirements. In yet another embodiment, the lower limit of the volumetric concentration factor is determined based on the concentration factor required for large-scale production.

[0013] In one embodiment of this application, the method further includes determining a system load limit. In one embodiment of this application, the system load limit is determined based on a first-stage membrane transmembrane pressure limit.

[0014] In one embodiment of this application, a system water flux test is also included. In one embodiment of this application, the system water flux test is performed before steps a) and / or c). In one embodiment of this application, the system water flux test includes measuring the system water flux of the tangential flow filter and comparing it with a reference system water flux. In one embodiment of this application, the reference system water flux is the initial system water flux of the tangential flow filter or the system water flux measured during previous use. In one embodiment of this application, when the reference system water flux is the initial system water flux, the system water flux decreases by no more than 20% compared to the reference system water flux. In one embodiment of this application, when the reference system water flux is the system water flux measured during previous use, the system water flux decreases by no more than 10% compared to the reference system water flux.

[0015] Another aspect of this application provides a method for performing tangential flow filtration, comprising: a) constructing a tangential flow filtration system, including a tangential flow filtration device, an inlet pump in fluid communication with the inlet of the tangential flow filtration device, and a return flow control device in fluid communication with the return outlet of the tangential flow filtration device; b) setting parameters; and c) operating the system.

[0016] In one embodiment of this application, a system water flux test is also included. In one embodiment of this application, the system water flux test is performed before step b) or step c).

[0017] In one embodiment of this application, the parameters include actual system load, upper limit of transmembrane pressure of the first-stage membrane, inlet flux, and volumetric concentration factor.

[0018] Another aspect of this application provides a method for testing system water flux, comprising: a) constructing a tangential flow filtration system including a tangential flow filtration device comprising a multi-stage ultrafiltration membrane package; b) adding water and operating the tangential flow filtration system; c) adjusting the inlet pressure and the outlet pressure; and d) determining the system water flux.

[0019] In one embodiment of this application, the multi-stage ultrafiltration membrane pack is a series-connected multi-stage ultrafiltration membrane pack. In another embodiment of this application, the multi-stage ultrafiltration membrane pack is a series-connected three-stage ultrafiltration membrane pack. In another embodiment of this application, the membrane ratio of the three-stage ultrafiltration membrane pack is 1:1:1.

[0020] In one embodiment of this application, the tangential flow filtration system further includes an inlet pump communicating with the inlet fluid of the tangential flow filtration device, and a return end valve communicating with the return port fluid of the tangential flow filtration device.

[0021] In another embodiment of this application, the tangential flow filtration system includes a tangential flow filter device, an inlet pump communicating with the inlet fluid of the tangential flow filter device, and a return flow control device communicating with the return flow port of the tangential flow filter device. In one embodiment of this application, when performing a system water flux test, the return flow control device includes a return flow valve and an optional return flow pump, wherein the inlet pressure is adjusted by the inlet pump and the outlet pressure is adjusted by the return flow valve.

[0022] In one embodiment of this application, the inlet and outlet pressures are adjusted to determine the system transmembrane pressure. In one embodiment of this application, the system transmembrane pressure is not less than 0.5 bar. In one embodiment of this application, the system transmembrane pressure is 0.5-1.0 bar. In one embodiment of this application, the system transmembrane pressure is approximately 0.8 bar.

[0023] Compared with existing technologies, the tangential flow filtration system and method of this application are easy to operate and scale up, can precisely control the parameters of the tangential flow filtration system, and can achieve stable transmembrane pressure and volumetric concentration factor. Furthermore, the system water flux testing method of this application can obtain data results efficiently and conveniently. Attached Figure Description

[0024] The present application will now be described in more detail with reference to the accompanying drawings, in which:

[0025] Figure 1a This is a schematic diagram of one embodiment of the tangential flow filtration system of this application. It shows a storage bottle, an inlet pump, a single-pass tangential flow filtration device, a return pump, a return valve, a collection bottle, and piping connecting the above components, including a pressure gauge.

[0026] Figure 1b is a schematic diagram of one embodiment of the single-pass tangential flow filtration device of this application. It shows a first-stage membrane, a second-stage membrane, a third-stage membrane, and piping connecting the above components, the piping including a pressure gauge.

[0027] Figure 2a This shows the changing trends of TMP and volume concentration factor with the amount of sample loaded under the reflux valve control mode.

[0028] Figure 2b This shows the pressure change trend of the SP-TFF system under the reflux valve control mode.

[0029] Figure 3a This shows the variation trend of TMP and volumetric concentration factor with sample loading under a dual-pump control system.

[0030] Figure 3b This shows the pressure change trend of the SP-TFF system under the dual-pump control system.

[0031] Figure 4 This describes how water flux changes with the system's total mass per unit volume (TMP).

[0032] Figure 5 The simulation aimed to determine the relationship between Qp and TMP of the first-stage membrane under different inlet fluxes.

[0033] Figure 6 The simulation aimed to determine the relationship between Qp and TMP of the third-stage membrane under different inlet fluxes.

[0034] Figure 7a It describes how stress changes over time.

[0035] Figure 7b It refers to the changes in flow velocity at the through end and outlet.

[0036] Figure 7c It describes the changes in volume concentration factor and transmembrane pressure of each membrane stage and the system.

[0037] Figure 8 The trend of TMP with loading is a 4-fold volumetric concentration system.

[0038] Figure 9 The trend of TMP with loading is a 6-fold volumetric concentration system.

[0039] Figure 10The trend of TMP with loading is 8-fold volume concentration system.

[0040] Figure 11 This shows the trend of system TMP with load under an inlet flux of 36 LMH.

[0041] Figure 12 This is the trend of system TMP with load under an inlet flux of 33LMH.

[0042] Figure 13 This shows the trend of system TMP with load under an inlet flux of 30 LMH. Detailed Implementation

[0043] definition

[0044] In this application, "single-pass tangential flow filtration (SP-TFF)" refers to tangential flow filtration technology where the liquid passes through the tangential flow filtration device in one pass rather than through a recirculation process. "Single-pass tangential flow filtration device" refers to a device used for single-pass tangential flow filtration, and the selection of its model is within the conventional skills of those skilled in the art.

[0045] In this application, "system transmembrane pressure" is equal to the sum of the inlet pressure and the outlet pressure divided by 2, minus the sum of the pressures at each permeation end.

[0046] In this application, the "first-stage membrane transmembrane pressure" is equal to the sum of the inlet pressure and the return port 1 pressure divided by 2 minus the permeate end 1 pressure.

[0047] In this application, the "second-stage membrane transmembrane pressure" is equal to the sum of the pressure at reflux port 1 and the pressure at reflux port 2 divided by 2 and minus the pressure at the permeation end 2.

[0048] In this application, the "third-stage membrane transmembrane pressure" is equal to the sum of the pressure at the return port 2 and the outlet pressure divided by 2 minus the pressure at the permeate end 3.

[0049] In this application, "membrane area" refers to the sum of the total areas of all levels of membranes in the membrane package.

[0050] In this application, "membrane ratio" refers to the ratio of the areas of membranes at each stage in a multi-stage membrane system.

[0051] In this application, "inlet flux" equals the liquid flow rate through the inlet divided by the membrane area, and its unit is LMH (L / h*m). 2 ).

[0052] In this application, the return port of the last stage membrane is also referred to as the "outlet". The "outlet flux" is equal to the total volume of liquid passing through the outlet divided by the membrane area and then divided by the transit time; its unit is LMH (L / h*m). 2 ).

[0053] In this application, "permeable end flux (Qp)" is equal to the liquid flow rate through the permeable end divided by the membrane area corresponding to that permeable end, and its unit is LMH (L / h*m). 2 )

[0054] In this application, "system water flux (NWP)" refers to the volume of water passing through each stage of the membrane per unit time, per unit membrane area, and per unit pressure, and its unit is L / h*m. 2 *psi.

[0055] In this application, "volume concentration factor (VCF)" refers to the factor by which the volume is reduced during a concentration operation, which is equal to the inlet flux divided by the outlet flux.

[0056] In this application, "system steady state" means that the pressure and corresponding flow velocity distribution of each membrane in the system are in a stable state, that is, the pressure and flow velocity of each membrane do not increase or decrease significantly.

[0057] In this application, "system capacity" refers to the processing capacity of the tangential flow filtration system, expressed as the volume of liquid processed per unit membrane area (L / m²). 2 ).

[0058] In this application, "actual system load" is equal to the volume of the sample to be filtered divided by the membrane area.

[0059] In one of the implementation methods, such as Figure 1a As shown, the tangential flow filtration system uses a single-pass tangential flow filtration device. During operation, liquid from the storage bottle enters the inlet pump through a pipeline, is pumped by the inlet pump, and then enters the single-pass tangential flow filtration device through the inlet pipeline. The permeate exits the single-pass tangential flow filtration device through the permeate end, and the retentate exits the single-pass tangential flow filtration device through the return port. Then, when the return pump is activated and the return valve is closed to prevent liquid from passing through the return valve, the retentate enters the return pump through a pipeline. Finally, the retentate is pumped by the return pump through a pipeline into the collection bottle. When the return valve pressure regulation function is activated and the return pump is closed to prevent liquid from passing through the return pump, the retentate enters the return valve through a pipeline. Finally, the retentate passes through the return valve through a pipeline into the collection bottle.

[0060] In one of the implementation methods, such as Figure 1b As shown, the tangential flow filtration system adopts a single-pass tangential flow filtration device, which includes three ultrafiltration membrane packages connected in series. During operation, the liquid enters the inlet of the first-stage membrane through the pipeline. The permeate leaves the first-stage membrane through the permeate end 1, and the retentate leaves the first-stage membrane through the return port 1 and enters the inlet of the second-stage membrane through the pipeline. The permeate leaves the second-stage membrane through the permeate end 2, and the retentate leaves the second-stage membrane through the return port 2 and enters the inlet of the third-stage membrane through the pipeline. The permeate leaves the third-stage membrane through the permeate end 3, and the retentate leaves the third-stage membrane through the outlet.

[0061] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0062] Example 1

[0063] System water flux (NWP)

[0064] To obtain water flux data for the three-stage membrane series system more quickly, a method for testing the overall water flux of the three-stage membrane series system was adopted. This involved controlling the inlet pump and the return valve to achieve different transmembrane pressures and monitoring the robustness of the system water flux under different transmembrane pressure conditions.

[0065] A single-pass tangential flow filtration system was constructed, in which a Millipore SP-TFF system (Pellicon3 Cassette P3C030C00, Ultracel 30kDa, C-channel, membrane ratio 1:1:1) was used as the single-pass tangential flow filtration device. An inlet pump (diaphragm pump, QF150S (Quattro)) was installed at the inlet of the device, and a reflux valve was installed at its outlet. The reservoir, inlet pump, single-pass tangential flow filtration device, reflux valve and collection bottle were connected in sequence by pipelines. Pressure gauges were installed at the inlet, the reflux port of each stage of membrane and the permeate port.

[0066] Deionized water was pumped in using the inlet pump. The inlet pressure was adjusted to 0.6 bar using the inlet pump, and the outlet pressure was adjusted to 0 bar using the reflux valve, resulting in a transmembrane pressure of 0.3 bar. The system was run for 5 minutes. After the membrane pressures and water temperature stabilized, the permeate velocity, outlet velocity, inlet pressure, outlet pressure, permeate pressure, and water temperature were recorded. The NWP was then calculated using the following formula:

[0067]

[0068] Where P = permeate flow rate; K = temperature correction factor; Pin = inlet pressure; Pout = outlet pressure; Pp = permeate pressure; and A = membrane area.

[0069] NWP Temperature Correction Factor K

[0070] T(°F) T(℃) K T(°F) T(℃) K T(°F) T(℃) K 125.6 52 0.595 96.8 36 0.793 68.0 20 1.125 123.8 51 0.605 95.0 35 0.808 66.2 19 1.152 122.0 50 0.615 93.2 34 0.852 64.4 18 1.181 120.2 49 0.625 91.4 33 0.842 62.2 17 1.212 118.4 48 0.636 89.6 32 0.859 60.8 16 1.243 116.6 47 0.647 87.8 31 0.877 59.0 15 1.276 114.8 46 0.658 86.0 30 0.896 57.2 14 1.310 113.0 45 0.670 84.2 29 0.915 55.4 13 1.346 111.2 44 0.682 82.4 28 0.935 53.6 12 1.383 109.4 43 0.694 80.6 27 0.956 51.8 11 1.422 107.6 42 0.707 78.8 26 0.978 50.0 10 1.463 105.8 41 0.720 77.0 25 1.000 48.2 9 1.506 104.0 40 0.734 75.2 24 1.023 46.4 8 1.551 102.2 39 0.748 73.4 23 1.047 44.6 7 1.598 100.4 38 0.762 71.6 22 1.072 42.8 6 1.648 98.6 37 0.777 69.8 21 1.098 41.0 5 1.699

[0071] Then, adjust the outlet pressure sequentially to 2, 3, 4, 5, and 6 psi via the reflux valve, and then adjust the inlet pressure via the inlet pump to achieve a transmembrane pressure of 0.3 bar. If the outlet flow rate drops to 0, the outlet pressure will no longer increase. Repeat each measurement twice.

[0072] Then, the above process is repeated, except that the transmembrane pressure of the control system is controlled at 0.5 bar, 0.8 bar and 1.0 bar respectively.

[0073] The results are as follows Figure 4 As shown, the higher the transmembrane pressure, the more stable the system water flux test results. However, if the outlet pressure is not controlled and is 0, the water flux data deviates significantly from other data, approaching 10%. To ensure the robustness of this method in testing system water flux, the outlet pressure needs to be controlled to be greater than 0. Considering the acceptable range of a 10% deviation across multiple measurements, the system transmembrane pressure range used in the system water flux test is 0.5–1.0 bar.

[0074] Currently, traditional methods for testing the water flux of ultrafiltration membrane packs involve testing the water flux of a single membrane stage. However, testing the water flux of a multi-stage system requires changing the connection mode of the three membrane stages from a series configuration to a parallel configuration before using conventional testing methods. Alternatively, the three-stage series system can be disassembled and the water flux tested stage by stage. This invention, for the first time, uses a method to test the water flux of the entire three-stage membrane series system without changing the connection mode of the three membrane stages or testing the water flux of each individual membrane stage. This allows for a single system water flux test, simplifying the testing process and obtaining water flux data more quickly.

[0075] Example 2

[0076] Comparison of the effects of dual-pump control strategy and return-side valve control strategy

[0077] A single-pass tangential flow filtration system was constructed, in which a Millipore SP-TFF system (Pellicon3 Cassette P3C030C00, Ultracel 30kDa, C-channel, membrane ratio 1:1:1) was used as the single-pass tangential flow filtration device. An inlet pump (diaphragm pump, QF150S (Quattro)) was installed at the inlet of the device, and a parallel reflux pump (peristaltic pump, BT100-2J (Longer Pump)) and a reflux valve were installed at the outlet. The reservoir, inlet pump, single-pass tangential flow filtration device, reflux pump, reflux valve and collection bottle were connected in sequence by pipelines. Pressure gauges were installed at the inlet and the reflux ports and permeate ports of each stage of the membrane.

[0078] (1) Backflow valve control strategy

[0079] Disinfect the system by rinsing with 0.1M NaOH at an inlet flux of 100 L / m³. 2 The system then cycles for 60 minutes.

[0080] As described in Example 1, the system water flux was tested (using a system transmembrane pressure of 0.8 bar). The system was then equilibrated with an inlet flux of 100 LMH using equilibration buffer (50 mM Tris-HAc, 150 mM NaCl, pH 7.4) at a rate of 20 L / m³. 2 After volumetric flushing, the pH and conductivity of the effluent were measured until they equaled the equilibrium buffer to confirm the equilibration of the three-stage ultrafiltration membrane pack. The pressure adjustment function of the reflux valve was then opened, and the reflux pump was closed to prevent liquid from passing through it. The sample (supernatant from mouse myeloma cell fermentation broth, obtained through perfusion culture and clarification) was pumped into the system. The system was started, and the inlet pump speed was adjusted to the preset inlet flux (36 LMH). After running for 5 minutes, the reflux valve was adjusted to the predetermined outlet pressure (3 psi; according to previous development data, maintaining an outlet pressure of 3 psi at this point allows the system to achieve a 4-fold volumetric concentration factor). The inlet flow rate, outlet flow rate, inlet pressure, reflux port 1 pressure, reflux port 2 pressure, outlet pressure, permeate port 1 pressure, permeate port 2 pressure, and permeate port 3 pressure were recorded over time. The transmembrane pressure and volumetric concentration factor of the system and each stage of the membrane were calculated. The results are shown below. Figure 2a and 2b As shown.

[0081] (2) Dual-pump control strategy

[0082] After sterilizing, measuring NWP, and equilibrating the three-stage ultrafiltration membrane pack as described in (1), turn on the reflux pump and close the reflux valve to prevent liquid from passing through it. Pump the same sample into the system and run it. Adjust the inlet pump speed to the preset inlet flux (36 LMH). After running for 5 minutes, adjust the reflux pump to the preset outlet flux (9 LMH) to achieve a volume concentration factor of 4. Record the inlet flow rate, outlet flow rate, inlet pressure, reflux port 1 pressure, reflux port 2 pressure, outlet pressure, permeate port 1 pressure, permeate port 2 pressure, and permeate port 3 pressure over time. Calculate the transmembrane pressure and volume concentration factor of the system and each stage of the membrane. The results are as follows: Figure 3a and 3b As shown.

[0083] In the reflux valve control strategy, controlling the outlet pressure leads to drastic changes in the volumetric concentration ratio. This outlet pressure control is based on adjustments made from prior development data. To control a specific concentration ratio, the outlet pressure needs to be kept around a certain value. However, in reality, setting the outlet pressure in this way results in a higher concentration ratio than the preset value. This is an uncertainty introduced by the reflux valve control strategy—a discrepancy between the developed data and actual operating conditions. Therefore, the reflux valve control strategy needs to be adjusted according to the actual volumetric concentration ratio, as the prior development data cannot provide a reliable reference for actual production. Furthermore, attempting to lower the system pressure as it increases leads to drastic changes in the volumetric concentration ratio. Reflux valve control complicates production control, requiring constant adjustments to the outlet pressure based on changes in the concentration ratio. In contrast, the dual-pump control strategy simplifies the control process. It eliminates the need for constant adjustments to the reflux port pressure based on changes in the concentration ratio; long-term stable control of the volumetric concentration ratio and pressure can be achieved simply by setting up the reflux pump.

[0084] Example 3

[0085] The sample was 200L of fermentation broth (supernatant of fermentation broth from Chinese hamster ovary cells, which integrate exogenous genes to express monoclonal antibodies, obtained through batch feeding culture and clarification processes; the concentration of monoclonal antibodies in the fermentation broth supernatant was 0.2mg / mL). In order to achieve continuous downstream production, the optimal range of inlet throughput and volumetric concentration factor was obtained to reduce the volume of fermentation broth, reduce the scale of downstream production of 200L, and at the same time reduce the amount of downstream affinity packing material used to reduce costs.

[0086] Phase 1: Determining the upper limit of the first-stage membrane transmembrane pressure

[0087] In a three-stage ultrafiltration membrane system, the first-stage membrane treatment has the largest feed volume, while the third-stage membrane treatment has the highest feed concentration. Therefore, this simulation experiment focuses on these two extreme cases to find the upper limits of the first-stage and third-stage transmembrane pressures that prevent severe polarization on the membrane surface and thus keep the system in a stable state.

[0088] Except for the use of a single-stage ultrafiltration membrane pack (P3C030C00, Ultracel 30kDa, C-channel), the same single-pass tangential flow filtration system as in Example 2 is used.

[0089] Optimizing TMP for the simulated first-stage membrane: Plotting TMP-Qp curves. Samples were used to simulate the feed solution treated by the first-stage membrane. After sterilization, NWP measurement, and equilibration of the system as described in Example 2, the reflux valve pressure regulation function was turned on and the reflux pump was turned off to prevent liquid from passing through the reflux pump. The sample was pumped into the system, allowing the system to circulate under the current sample. The inlet pump speed was adjusted to the preset inlet flux (240 LMH). After running for 5 minutes, the reflux port pressure was adjusted by changing the reflux valve to change the transmembrane pressure from the preset lower pressure to the highest pressure (3, 5, 10, 15, 20, and 25 psi from lower to highest). The permeate flow rate was recorded at different transmembrane pressures, and the permeate flux was calculated. The inlet flux was then adjusted to the next preset value (180, 120, and 60 LMH), and the above steps were repeated. The results of transmembrane pressure and permeate flux at different inlet fluxes are shown below. Figure 5 As shown.

[0090] Optimizing TMP for the simulated third-stage membrane: Plotting TMP-Qp curves. A sample concentrated to 3 times its original concentration was used to simulate the feed solution for the third-stage membrane encapsulation. The same procedures as for simulating the first-stage membrane TMP optimization were followed. The results are as follows: Figure 6 As shown.

[0091] In a single-pass tangential flow filtration system, the inlet fluxes and concentration factors of the treated feed solutions differ between the first and third stage membranes, leading to a decrease in the flux of the third stage membrane. The transmembrane pressure (TMP) of the third stage membrane is lower than that of the first and second stages, but since the feed solution treated by the third stage membranes has already passed through the first and second stages, the first stage membrane's transmembrane pressure is reached first, based on system pressure changes. Therefore, the first stage membrane's transmembrane pressure is used as the criterion for judging membrane surface polarization and protein adsorption.

[0092] For the first-stage membrane, at each preset inlet flux, the permeate flux initially increases with increasing TMP. However, once a certain value is reached, even if TMP continues to rise, the permeate flux no longer increases due to increased membrane surface polarization and protein adsorption. A similar trend was observed for the third-stage membrane. Therefore, it is necessary to control the upper limit of TMP for the first-stage membrane, i.e., the system load endpoint. Figure 5 and 6 As shown, in order to reduce the polarization of the membrane surface and the adsorption of proteins, the upper limit of the transmembrane pressure of the first-stage membrane is set to 12 psi.

[0093] Phase Two: Determining the Upper Limit of Import Flux

[0094] To reduce the rate of impurity adsorption on the membrane substrate surface and maintain a relatively long processing capacity, we optimized the inlet flux of the membrane substrate. Increasing the inlet flux improves the membrane substrate's processing speed, and the duration of steady-state operation is used to assess the impurity adsorption on the membrane surface.

[0095] Using the same single-pass tangential flow filtration system as in Example 2, after sterilization, NWP measurement, and equilibration of the three-stage ultrafiltration membrane pack, the reflux pump was turned on and the reflux valve was closed to prevent liquid from passing through it. The sample was pumped into the system, and the inlet pump speed was adjusted to the preset inlet pressure (from low to high: 5, 8, 10, 12, 15, 18, and 20 psi). The system was run continuously for the same time interval (1800 s), and the inlet pressure, reflux port 1 pressure, reflux port 2 pressure, outlet pressure, inlet flow rate, permeate end 1 flow rate, permeate end 2 flow rate, permeate end 3 flow rate, and outlet flow rate were recorded over time. The inlet pressure was then adjusted to other preset pressure values ​​by adjusting the inlet pump speed, and the system was run continuously for the same time interval, recording the above parameters sequentially. The inlet flux, outlet flux, and volumetric concentration factor were calculated. The results are as follows: Figure 7a -c is shown.

[0096] The system's steady state is determined by the changes in inlet pressure and flow rate. When the inlet flux is increased to a pressure of 10 psi, corresponding to an inlet flux of 36 LMH, the system can maintain stable inlet pressure and flow rate for a relatively long period, indicating a stable system state. However, when the inlet pressure reaches 12 psi or higher, the inlet pressure and flow rate become unstable over time, and the volumetric concentration factor also becomes unstable, indicating an unstable system state. This demonstrates that once the inlet pressure reaches 12 psi, the system is no longer in a stable state, and a stable system state is beneficial for the system's feed throughput. Therefore, to maintain a stable system state, the inlet pressure should be set no higher than 10 psi, and the corresponding inlet flux should not exceed 36 LMH.

[0097] Phase Three:

[0098] (1) Relationship between volumetric concentration factor and system load

[0099] Based on the results of the second phase, we first selected a dual-pump system that maintained an inlet pressure of 10 psi for a relatively long period. The system termination conditions were based on the experiments from the first phase; in this embodiment, the system would terminate its processing when the first-stage membrane transmembrane pressure was 12 psi. Under these conditions, the relationship between the volumetric concentration factor and the system load was investigated.

[0100] Using the same single-pass tangential flow filtration system as in Example 2, after sterilizing, measuring NWP, and equilibrating the three-stage ultrafiltration membrane pack, the reflux pump was turned on and the reflux valve was closed to prevent liquid from passing through. The sample was pumped into the system, and the inlet pump speed was adjusted to maintain the inlet flux at 36 LMH. After running for 5 minutes, the reflux pump speed was adjusted again to maintain the outlet flux at 9 LMH (i.e., achieving 4 times VCF). This was continued until the sample was exhausted or the transmembrane pressure of the first-stage membrane reached 12 psi. During this period, the inlet pressure, reflux port 1 pressure, reflux port 2 pressure, outlet pressure, permeate flow rate at 1, permeate flow rate at 2, permeate flow rate at 3, and outlet flow rate were recorded at equal time intervals. The system load, inlet flux, outlet flux, volumetric concentration factor, and transmembrane pressure of each stage membrane were calculated. The above experiment was repeated, and the reflux pump speed was adjusted each time to maintain the outlet flux at 6 LMH and 4.5 LMH (achieving 6 times and 8 times VCF, respectively). The recorded data were plotted as follows: Figure 8 , 9 The curves shown in Figure 10 represent the volumetric concentration factor versus transmembrane pressure as a function of system load.

[0101] like Figure 8 , 9 As shown in Figure 10, at an inlet flux of 36 LMH, 4x, 6x, and 8x VCF can achieve approximately 150 L / m³, respectively. 2 Approximately 75L / m 2 and approximately 40L / m 2 The system load is determined by the volumetric concentration factor. The higher the volumetric concentration factor, the lower the system load.

[0102] (2) Relationship between inlet flux and system load

[0103] Based on the results of (1), we first selected a dual-pump system to maintain a relatively long duration of 6 times VCF, and the system termination conditions were given according to the first-stage experiments. In this embodiment, the system would terminate its processing under the condition that the transmembrane pressure of the first-stage membrane was 12 psi. Under this condition, the relationship between inlet flux and system load was investigated.

[0104] Using the same single-pass tangential flow filtration system as in Example 2, after sterilizing, measuring NWP, and equilibrating the three-stage ultrafiltration membrane pack, the reflux pump was turned on and the reflux valve was closed to prevent liquid from passing through. The sample was pumped into the system, and the inlet pump speed was adjusted to maintain the inlet flux at 36 LMH. After running for 5 minutes, the reflux pump speed was adjusted again to maintain the outlet flux at 6 LMH (i.e., achieving 6 times VCF). This was continued until the sample was exhausted or the transmembrane pressure of the first-stage membrane reached 12 psi. During this period, the inlet pressure, reflux port 1 pressure, reflux port 2 pressure, outlet pressure, permeate flow rate at 1, permeate flow rate at 2, permeate flow rate at 3, and outlet flow rate were recorded at equal intervals. The system load, inlet flux, outlet flux, volumetric concentration factor, and transmembrane pressure of each stage membrane were calculated. The above experiment was repeated, and each time the pump speeds of the inlet pump and reflux pump were adjusted simultaneously to maintain the inlet flux and outlet flux at 33 LMH and 5.5 LMH, respectively. Figure 12 ) and 30 LMH and 5 LMH Figure 13 Based on the recorded data, plot as follows: Figure 11 , 12 The curves shown in Figure 13 represent the volumetric concentration factor versus transmembrane pressure as a function of system load.

[0105] like Figure 11 , 12 As shown in Figure 13, at a VCF of 6, 36 LMH, 33 LMH, and 30 LMH can achieve approximately 75 L / m³. 2 Approximately 90L / m 2 and more than 100L / m 2 The system load is determined by the inlet throughput. The higher the inlet throughput, the lower the system load.

[0106] Based on the above experiments, the ultimate goal is to obtain the range of inlet flux and volumetric concentration factor that can achieve actual system load in a tangential flow filtration system.

[0107] The above are merely specific application examples of this application and do not constitute any limitation on the scope of protection of this application. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to list and describe all embodiments here. Any technical solutions similar to these obtained through equivalent transformations or substitutions fall within the scope of protection of this application.

Claims

1. A tangential flow filtration system comprising a tangential flow filtration device, an inlet pump in fluid communication with an inlet of the tangential flow filtration device, and a backflush control device in fluid communication with a backflush port of the tangential flow filtration device, the backflush control device comprising a backflush pump and a backflush end valve, the backflush pump and the backflush end valve being in parallel or switchable with each other.

2. The system of claim 1, the tangential flow filtration device being a single-pass tangential flow filtration device, and / or the inlet pump and the backflush pump being independently selected from a diaphragm pump or a peristaltic pump.

3. The system of claim 1, the tangential flow filtration device comprising one or more stages of ultrafiltration membrane packs.

4. The system of claim 3, the tangential flow filtration device comprising multiple stages of ultrafiltration membrane packs in series.

5. The system of claim 3, the tangential flow filtration device comprising three stages of ultrafiltration membrane packs in series.

6. The system of claim 1, further comprising a reservoir device in fluid communication with the inlet pump and a collection device in fluid communication with the backflush control device.

7. The system of claim 6, the reservoir device containing a liquid selected from the group consisting of a sample or a buffer.

8. The system of claim 7, the sample being a protein solution or a cell broth supernatant.

9. The system of claim 7, the sample being an animal cell broth supernatant.

10. The system of claim 7, the sample being a Chinese hamster ovary cell or a mouse myeloma cell broth supernatant.

11. A method of determining tangential flow filtration parameters comprising: a) determining an upper limit of a first stage membrane transmembrane pressure; b) constructing a tangential flow filtration system according to any one of claims 1-10; c) determining an upper limit of an inlet flux; and d) determining an upper limit of a volumetric concentration factor, wherein: a) comprises opening the backflush end valve and closing the backflush pump, adjusting the pump speed of the inlet pump, and determining the upper limit of the first stage membrane transmembrane pressure based on maintaining a steady state of the system; b) comprises opening the backflush pump and closing the backflush end valve, adjusting the pump speed of the inlet pump, and determining the upper limit of the inlet flux based on maintaining a steady state of the system; c) comprises opening the backflush pump and closing the backflush end valve, adjusting the pump speed of the inlet pump, and determining the upper limit of the volumetric concentration factor based on maintaining a steady state of the system.

12. The method of claim 11, the determination of step a) being based on a steady state of the system.

13. The method of claim 11, the determination of step a) further comprising constructing a tangential flow filtration system comprising a tangential flow filtration device comprising a first stage membrane, the first stage membrane being the same as the first stage membrane of the tangential flow filtration device of step b).

14. The method of claim 11, the determination of step c) being based on an actual system load and the upper limit of the first stage membrane transmembrane pressure determined in a).

15. The method of claim 11, the determination of step d) being based on an actual system load and the upper limit of the first stage membrane transmembrane pressure determined in a).

16. A method of performing tangential flow filtration comprising: a) constructing a tangential flow filtration system according to any one of claims 1-10; b) setting parameters; and c) performing tangential flow filtration. ​ c) operating the system.

17. The method of claim 16, wherein the parameters include actual system load, first stage membrane transmembrane pressure upper limit, inlet flux, and volumetric concentration factor.

18. A method for testing system water flux, comprising: a) constructing a tangential flow filtration system according to any one of claims 1-10, the tangential flow filtration device comprising a multi-stage ultrafiltration membrane pack; b) adding water and operating the tangential flow filtration system; c) adjusting the inlet pressure and the outlet pressure; and d) determining the system water flux, comprising opening the backflow end valve and closing the backflow pump, adjusting the pump speed of the inlet pump, recording the permeate end flow rate, the outlet flow rate, the inlet pressure, the outlet pressure, the permeate end pressure, and the water temperature, and calculating the system water flux using the following equation: wherein NWP = system water flux, P = permeate end flow rate; K = temperature correction factor; Pin = inlet pressure; Pout = outlet pressure; Pp = permeate end pressure; and A = membrane area.

19. The method of claim 18, wherein the multi-stage ultrafiltration membrane pack is a multi-stage ultrafiltration membrane pack in series.

20. The method of claim 19, wherein the multi-stage ultrafiltration membrane pack is a three-stage ultrafiltration membrane pack in series. ​

Images