BioProcess™ resin mixer is designed to efficiently prepare and handle chromatography resins for packing buffer management and resin packing procedures. To maintain product safety and prevent cross-contamination in biopharmaceutical processes, the BioProcess resin mixer can be cleaned using an automated cleaning-in-place (CIP) method with alkaline sodium hydroxide (NaOH). Our best practice approach minimizes manual handling, ensures full cleaning coverage, and delivers consistent results in approximately 6.5 min per cycle using 250 mM NaOH.
Introduction
In the biopharmaceutical industry, maintaining the highest standards of cleanliness is not just a regulatory requirement—it’s a cornerstone of product safety and process integrity. Equipment such as resin mixers, which can play a critical role in chromatography resin preparation, must be thoroughly cleaned to prevent cross-contamination of resin. Here, we highlight a procedure for effective cleaning of our BioProcess resin mixer, an automated mixer that can also be used as a slurry tank and plays a critical role in column packing processes.
Cleaning here refers to the physical removal of downstream purification resin residues before column packing, including resin buffers, CIP chemicals, and microbial contaminants. For hardware like the resin mixer, this can involve a combination of mechanical action, chemical agents, and rinsing protocols tailored to the materials and design of the equipment. By implementing robust cleaning protocols, you can ensure that equipment operates within safe and compliant parameters, supporting the production of high-quality biopharmaceuticals.
This article demonstrates the rinsing and cleaning performance of the resin mixer (Fig 1) when operated with our media handling unit using sodium hydroxide (NaOH) as the cleaning agent. The results showed complete cleaning coverage to give a residue-free surface, and consistent performance in approximately 6.5 min per cleaning cycle.
Background and approach
Because of the mixer’s internal geometry, including the helical agitator, filters, and spray balls, verifying that all internal surfaces can be effectively cleaned is a key part of process validation. To demonstrate this capability, we show how the mixer can be cleaned and operated using the media handling unit. The purpose was to confirm that the combination of these two systems provides complete cleaning coverage under defined operating conditions using sodium hydroxide as the cleaning agent.
The test used riboflavin (vitamin B2) as a fluorescent tracer, which is a reliable and established biomolecule for visually confirming that cleaning solution reaches all internal surfaces. When illuminated with UV light, any remaining riboflavin appears in bright green, making coverage easy to assess.
Fig 1. BioProcess resin mixer is an automated mixer system for chromatography resin handling in the biopharmaceutical industry.
MATERIALS AND METHODS
Prior to the cleaning procedure, the resin mixer was prepared according to the instructions for use. The following equipment was used for the setup:
| Equipment | Description |
| BioProcess resin mixer, 500 L | Controls the cleaning sequence through the preprogrammed resin mixer CIP unit operation, which manages valve openings, sequencing, and timing. |
| Media handling unit | Supplies and pumps the cleaning solution (250 mM NaOH) to the resin mixer under defined flow and pressure conditions. |
| Pressure monitor | Used to measure and record the pressure during pumping to the resin mixer. |
| UV inspection light | Used to illuminate internal surfaces and visualize riboflavin fluorescence before and after cleaning. |
| Turbine flow meter | Used to monitor flow rate during operation. |
| Riboflavin (vitamin B2) | Used as a fluorescent tracer for visual inspection under UV light. |
| Tanks for water and other chemicals |
Fig 2. Schematic of the CIP cleaning loop for the resin mixer using a media handling unit. Cleaning solution (250 mM NaOH) is supplied from a 500 L tank via a media handling unit set to 5 bar (72.5 psi, 0.5 MPa), then passed through a turbine flow meter before entering a manifold that directs flow to the CIP inlets. The tank top inlet B1 is connected directly to a separate outlet on the media handling unit manifold. The upper spray ball inlets B2 and B3 supply spray balls SB-1 and SB-2, respectively, for cleaning the upper regions of the mixer. The lower inlet B4 delivers solution through the air blow flow path. Drainage occurs through bottom valve outlet P1.
A 500 L tank was connected to the media handling unit via tubing. The media handling unit outlet was connected to a turbine flow meter, followed by two T-way connectors that distributed the cleaning agent to the respective CIP inlets on the resin mixer (Fig 2).
During operation, the media handling unit remained continuously active and maintained a pressure of 5 bar to supply the cleaning agent at a flow rate of 76 L/min. The resin mixer CIP unit operation controlled all process logic―including valve sequencing, timing and agitation, while the media handling unit provided a steady flow of 250 mM NaOH to the resin mixer.
The automated CIP cycle used in this setup consumed approximately 400 L of 250 mM NaOH per cleaning cycle. For waste collection, a capacity of 600 L is sufficient to collect both the discharged NaOH, and the subsequent rinse used to remove residual NaOH. In riboflavin verification tests, the full process from applying riboflavin to confirming a clean resin mixer takes under 30 min.
CIP resin mixer unit operation settings:
Agitator speed: 40 rpm
Filter cleaning:
- Cleaning agent: 250 mM NaOH
- Number of cycles: 2
- Duration per cycle: 30 s
Outlet flush duration: 30 s
Spray-ball cleaning:
- Cleaning agent: 250 mM NaOH
- Flow rate: 76 L/min
- Number of cycles: 3
- Duration per cycle: 30 s
Total time: 390 s (6.5 min).
Unit operation sequence:
| Step | Description |
| 1. Start sequence | The resin mixer target weight was set to 150 kg, triggering the opening of the tank top inlet valve B1. |
| 2. Tank filling | The mixer, initially empty, was filled with 250 mM NaOH through inlet B1 until the target weight was reached, providing sufficient volume to cover the underside of the agitator. |
| 3. Pressurization | When the target weight was reached, inlet B1 closed, and the system automatically pressurized to 0.2 bar (2.9 psi, 0.02 MPa) to begin the cleaning sequence. |
| 4. Filter adapter cleaning | Each bottom net adapter (three in total) was opened sequentially. NaOH was pushed through the nets and routed to waste via P2 → B6 → P1. |
| 5. CIP of airblow | Inlet B4 was activated. Cleaning solution was pumped through the air blow tubing and directed to waste via P2 → B6 → P1. |
| 6. Spray-ball cleaning | Inlets B2 and B3 were activated, delivering NaOH to spray balls SB1 and SB2 at a flow rate of 76 L/min, ensuring complete coverage of the upper internal surfaces. |
| 7. UV inspection | After cleaning, the resin mixer was inspected under UV light to verify complete removal of riboflavin. |
Results and key observations
UV inspection confirmed complete cleaning reach coverage throughout the BioProcess resin mixer. After cleaning, all critical areas, including the agitator and the net adapters, were fully cleaned and riboflavin-free.
Additional observations include:
- Successful CIP unit operation: The resin mixer—in combination with the media handling unit—ensures consistent flow and pressure throughout the process, delivering repeatable results.
- Efficient use of NaOH: Each cleaning cycle used approximately 400 L of 250 mM NaOH.
- Fast and automated: Each automated cleaning cycle was completed in 6.5 min, followed by a drain phase.
- Minimal manual handling: Reduced variability and a straightforward way to perform CIP.
Fig 3. Images from visual inspection inside the mixer before and after riboflavin contamination and subsequent cleaning using NaOH. Images labeled (A) before and (a) after, is through the adapter under the agitator; (B) and (b) is through the manhole above the agitator; (C) and (c) from the inside of the tank roof; (D) and (d) is above the agitator.
This activity demonstrated the cleaning capability of the media handling unit and mixer configuration, confirming that the setup achieves effective cleaning coverage and residue removal.
Conclusion
The BioProcess resin mixer, combined with the media handling unit, provides a fully automated, efficient, and robust cleaning process for chromatography resin preparation. This method supports compliance and facilitates high-quality biopharmaceutical production.
The setup described provides:
- Efficient use of low-molarity NaOH and minimal manual handling to ensure effective cleaning.
- Consistent, fast, and reproducible cleaning performance to aid you in compliance and support high-quality biopharmaceutical production.
Based on our results, the recommended cleaning method for the resin mixer is:
- Cleaning agent: NaOH, 250 mM
- Cycle time: 6.5 min
- Flow rate: 76 L/min at 5 bar (72.5 psi, 0.5 MPa) pressure
KEY QUESTIONS ANSWERED IN THIS STUDY
Q: What concentration of NaOH is recommended?
A: 250 mM NaOH.
Q: How long does one cleaning cycle take?
A: Approximately 6.5 min.
Q: How is cleaning coverage verified?
A: Using riboflavin tracer and UV light inspection.
Q: How much NaOH is used per CIP cycle?
A: Approximately 400 L of 250 mM NaOH per automated cleaning cycle.
Q: What waste tank capacity should I plan for?
A: Plan for at least 600 L. This covers the discharged NaOH (~ 400 L) plus subsequent rinse, providing a practical safety margin (exact needs depend on site setup and local procedures).
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