Hollow fiber membrane, what are the applications and advantages in filtration?

What is a hollow fiber membrane?

Hollow fiber membrane (HFM) is a synthetic translucent barrier material composed of countless tiny hollow fibers. These fine fibers are characterized by their internal hollow channels and are covered with micropores. They screen the particles flowing through them by the size of the micropores, allowing only molecules of a certain size or smaller to pass through, a process based on the molecular weight cut-off (MWCO) standard. Since it was first developed for reverse osmosis in the 1960s, the application of hollow fiber membranes has expanded to water treatment, desalination, cell culture, and medicine and tissue engineering. In commercial applications, this membrane is usually integrated into the filter element, providing an effective means for the precise separation of liquids.

What is the filtration principle of hollow fiber columns?

The working principle of hollow fiber column components is based on membrane filtration technology. In short, hollow fiber columns are made of membranes used for filtration into hollow columns. When the filtrate flows through the middle of the hollow fiber membrane, the tangential flow filtration (TFF) technology is used to achieve effective separation of large molecules and small molecules. TFF allows substances to flow parallel to the membrane surface instead of directly through the membrane, thereby reducing the risk of blockage and improving filtration efficiency.

When the fluid passes through, the pores of the membrane only allow molecules of a certain size to pass through, while larger molecules or particles are retained. This separation process usually involves physical size screening, and can also involve selective separation of chemical affinity. The size of the pores on the membrane determines what substances can pass through. The diameter of these pores is usually in the range of a few nanometers to a few microns, which can be customized according to the needs of the application. For applications that require the removal of bacteria and viruses, hollow fiber membranes can have pores small enough to provide microfiltration or ultrafiltration functions.

 

Introduction to hollow fiber column components

The components of the hollow fiber column include:

1. Hollow fiber membrane: This is the core part of the hollow fiber column, which is composed of multiple hollow fiber membranes made of mPES material and is responsible for the separation of substances during the filtration process. Hollow fiber membranes are mostly asymmetric structures, consisting of a fine surface layer and a porous support layer.

2. Housing: Made of corrosion-resistant transparent polysulfone material, it is used to protect the internal fibers and maintain the integrity of the structure.

3. Feed/retentate port: Made of white polysulfone, located at the top/bottom of the column, used to guide fluid in and out of the fiber column.

4. Permeate port: Made of white polysulfone, located on the side of the column, where the filtered liquid leaves the membrane.

5. End caps: Close both ends of the fiber bundle to ensure that the fluid can only pass through the inside of the hollow fiber.

6. Internal seals: Made of polyurethane/epoxy resin, wrapping each hollow fiber column, providing a support site for the hollow fiber column, and completely isolating the feed flow channel and the permeate flow channel.

7. O-rings/seals: Made of silicone, to ensure that there is no fluid leakage in the column and maintain the integrity of the closed system.

These components of the hollow fiber column work together to ensure the efficiency and reliability of the filtration process, suitable for a variety of industrial and laboratory applications.

 

What are the advantages of hollow fibers?

1. High flow rate and high loading capacity.

Hollow fiber membranes have a high surface area to volume ratio, which means that they can process large amounts of fluid in a small space. Specifically, they can: (1) increase processing capacity: In equipment of the same volume, hollow fiber membranes can process more fluids because of their larger surface area, which is particularly important for industrial applications that require processing large amounts of fluid. (2) improve separation efficiency: a larger surface area means more opportunities for fluid to contact the membrane, and more frequent and effective material exchange during the separation process. This not only improves separation efficiency, but also ensures the quality and purity of the final product.

2. Mild and low shear force.

Hollow fiber membranes have a screen-free open tubular flow channel structure, which avoids irregular and violent turbulence during the circulation of biological fluids, so they have lower shear force. Mild conditions can effectively prevent the aggregation and conformational changes of biological macromolecules such as proteins, which is beneficial to protecting the integrity of macromolecules such as viral proteins and improving the activity yield of target samples.

In some biopharmaceutical production processes, the TFF step has special requirements, resulting in low recovery rates, including blockage, excessive stress, shear sensitivity of the target molecule, or high viscosity.

3. Simple operation and easy production.

Hollow fiber membrane columns are designed to achieve simpler and faster drug development and production by minimizing equipment operation steps such as wetting and sterilization. Disposable membrane columns eliminate the need for cleaning solutions and cleaning validation.

4. Renewability.

Hollow fiber columns can be cleaned and regenerated using 0.5M NaOH. By simply circulating the NaOH solution through the hollow fiber column, the residues attached to the membrane surface can be efficiently removed, thereby quickly restoring its original filtration efficiency, thus avoiding the high cost of frequent membrane replacement.

5. Reliable linear amplification performance.

The hollow fiber tubular flow path is simple, the fluid flow pressure drop loss is small, and the TMP membrane pressure is uniform along the flow path, which is conducive to improving the overall membrane area utilization. The mature tubular flow path fluid mechanics model provides a perfect theoretical basis for direct linear amplification and ensures the success rate of process amplification.

 

Typical Applications of Hollow Fiber Columns

Hollow fiber columns play a vital role in the biotechnology and pharmaceutical industries, and their application areas are wide, mainly including:

1. Purification and concentration of vaccines: Hollow fiber columns can concentrate vaccine preparations and increase their concentration in the final product, while removing unwanted small molecule impurities through dialysis to improve the purity and safety of vaccines.

2. Purification and concentration of viral vectors: In gene therapy and vaccine development, high purity of viral vectors is a must. Hollow fiber columns can efficiently separate viral vectors through physical size sorting, retain their integrity and activity, and remove small molecules through dialysis to improve purification efficiency.

3. Clarification and filtration of cells and bacteria in fermentation broth: Hollow fiber columns can quickly remove cells and bacteria from the biological mixture produced by fermentation, clear turbidity, and provide clean starting materials for subsequent extraction and purification steps.

4. Recovery and washing of cells and bacteria: After the cell culture and microbial fermentation process, cells need to be recovered for further analysis or product extraction. Hollow fiber columns can effectively collect cells and remove impurities from the culture medium while providing a gentle washing environment to maintain cell integrity.

5. Protein concentration and dialysis: Hollow fiber columns are particularly important in protein engineering. They can not only concentrate protein solutions, but also remove salts and other small molecule impurities, which is crucial for the development and production of protein drugs.

These application areas demonstrate the versatility and efficiency of hollow fiber columns in modern bioprocesses, thus playing a key role in the preparation, cleaning and processing of biological products.