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Sterile Filtration

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Strengthen bioprocessing performance with assured sterile filtration

At Thermo Fisher Scientific, we understand that customers must manage and mitigate bioburden contamination risks as process fluids are prepared and used, intermediate steps are protected, and final fill is completed. Integrating sterile membrane solutions and single-use fluid management assemblies throughout the workflow helps manage bioburden risk more effectively and with greater intent.

Managing bioburden throughout the workflow

Mitigating bioburden risks is a part of each unit operation in the biomanufacturing process. As fluids are prepared, handled, and transferred across operations, buffers, media, and in-process solutions can carry microorganisms or support their growth as the process progresses. Integrating membrane filters helps reduce the risk of microbial contamination at every step of the operation.
 

0.2 µm sterilizing-grade filters are often used throughout manufacturing for bioburden reduction. Sterilizing-grade filtration is reserved for the final stage to avoid performing filter validation at each step.

When coordinated with fluid preparation, storage, and transfer activities within fluid management workflows, this approach helps identify and address filtration considerations earlier.

Supporting product quality at the sterilizing step

Membrane filtration of 0.2 micron or lower is used immediately prior to fill or further processing to manage viable microorganisms. At this step, filtration performance reflects the cumulative impact of upstream preparation, downstream handling, and prior bioburden management decisions.

 

Both bioburden reduction and sterilizing grade membrane filters are used as effective strategies for mitigating microbial risk. Factors, such as membrane material, differential pressure, and compatibility with the method used to sterilize the filter itself, whether by autoclaving, gamma irradiation, or chemical means, are considered when configuring this step.

Designing membrane filtration for scale

Selecting a suitable filter is a multi-step process. In early process development, a scale-down filter is used to establish baseline filtration characteristics. As the process moves into pilot and production runs and filter geometry changes, full-scale filter selection requires careful translation of the scale-down data into scale-up factors, filter configuration parameters, and appropriate connector choices.

Optimizing filter performance across filtration conditions

Understanding how operating conditions affect filtration behavior helps teams anticipate performance limits and plan more effectively.

Liquid filtration performance

Flow rate, differential pressure, and operating behavior are affected by fluid characteristics, operating parameters, and membrane construction. Membrane structure and pleat design are often reviewed to understand how throughput and pressure behavior may change under expected process conditions. Considering these variables together helps teams assess filtration behavior across operating windows.

Filter integrity testing in sterile filtration operations

Filter integrity testing follows regulatory requirements and risk considerations. Regulators are increasingly requiring pre-use, post-sterilization integrity testing (PUPSIT). Ease of testing is often dependent on effective membrane wetting. Careful consideration should be given to membrane material, sterilization method, and wetting protocols to minimize the risk of false failures.

Matching sterile filtration solutions to process needs

When selecting sterile filtration solutions, teams should account for multiple process requirements. Sterilizing and bioburden filtration steps often need to accommodate fluid characteristics, pressure behavior, operating expectations, and scale considerations simultaneously. Evaluating membrane chemistry, pore size, and format in the context of the workflow helps align filtration choices with the role of sterile filtration within broader bioprocess filtration strategies.

 

LifeASSURE membrane filters are applied across sterile and bioburden filtration steps, with a range of membrane materials, retention ratings, and configurations to address different process conditions. Several series incorporate Advanced Pleat Technology (APT), which is designed to increase usable membrane surface area while maintaining open flow paths between pleats.

 

Compare LifeASSURE membrane filters by material, rating, and typical applications to support process-driven selection.

Table 1. LifeASSURE membrane filters

 

 

LifeASSURE PDA filters

LifeASSURE PNA filters

 LifeASSURE PLA filters LifeASSURE PFS filters

Material description

Polyethersulfone (PES) 

Polyethersulfone (PES) 

Nylon 6,6 

 Polytetrafluoroethylene (PTFE) 

Water affinity

Hydrophilic 

Hydrophilic 

Hydrophilic 

 Hydrophobic

Membrane layers

Double-layer membrane filter

Single-layer membrane filter

Single-layer with multi-zone membrane filter

 Single-layer membrane filter

Advanced pleat technology

Yes

Yes

Yes

 Radial pleat

Rating

Sterilizing grade

Bioburden rated 

Bioburden rated 

 Sterilizing grade
Suggested applications Buffer, media feedstreams, serum and blood fractions, vaccines, biologics, high-purity deionized water and water for injection systems, pharmaceutical chemicals  Buffer, media feedstreams, serum and blood fractions, vaccines, biologics, high-purity deionized water and water for injection systems, pharmaceutical chemicals  Prefiltration and bioburden reduction, protection of sterilizing-grade membrane in pharmaceutical, biological, and bioprocessing industries Air and gases
Available pore sizes (µm) 0.10, 0.20  0.20, 0.45 0.20, 0.45, 0.65, 0.80  0.20
 

Explore LifeASSURE PDA Filter Cartridges
 

Explore LifeASSURE PDA Filter Capsules

 Explore LifeASSURE PNA Filter Cartridges

Explore LifeASSURE PLA Filter Cartridges
 

Explore LifeASSURE PLA Filter Capsules

Explore LifeASSURE PFS Filter Cartridges
 

Explore LifeASSURE PFS Filter Capsules

Configuring sterile filtration formats

Membrane Filter formats can be configured to align with the operational model of the process. Cartridge filters installed in reusable stainless-steel housings are often selected for fixed installations with established cleaning or sterilization practices. Single-use capsule formats are used when flexibility, simplified setup, or reduced handling steps are priorities, particularly in single-use workflows. Selecting between formats involves considering batch size, facility layout, equipment integration, and how filtration fits into routine operations.

Frequently asked questions

Filtration steps positioned as bioburden reduction are commonly applied throughout the bioprocess workflow to help reduce microorganisms and particulates in process fluids. Sterilizing-grade filtration is applied at the end of the process, prior to filling the drug substance or finished drug product, where defined membrane retention characteristics are used to control viable microorganisms.

Filter pore size is selected based on process risk, target microorganisms, and where the filtration step sits in the workflow. Sterilizing-grade filtration commonly uses nominal pore sizes, such as 0.2 µm, with 0.1 µm applied in specific cases where smaller organisms are a consideration. Larger pore sizes, such as 0.45 µm or above, are used for bioburden reduction earlier in the process.

Filter integrity testing is performed before use, after use, or at both points, depending on how the filtration step is designed and operated. Pre-use testing helps confirm that the filter is properly installed and undamaged before processing begins. Post-use testing is used to verify that filter integrity was maintained throughout the run. These checks support operational confidence by confirming expected filter performance under process conditions.

As processes scale, increases in batch volume, flow rate, and filtration time can change how membranes behave in operation across the workflow. Higher volumes may lead to greater pressure development, earlier operational limits, or longer exposure to process conditions. These factors can affect filter sizing, format selection, and operating parameters. Addressing scale-related considerations during process development helps teams anticipate how sterile and bioburden filtration steps will perform as processes move into manufacturing.

Discover filtration resources

Explore optional resources designed to support a deeper understanding of bioprocess filtration topics and decision-making considerations. Available materials include technical documents, webinars, and educational content that address practical applications, emerging trends, and process challenges across bioprocessing workflows. 

Explore the School of Purification

Gain practical insights into filtration, purification strategy, technology transfer, and emerging therapeutic applications.

 

Whether you are strengthening foundational knowledge or evaluating approaches for process development and manufacturing, the School of Purification supports ongoing learning across bioprocessing workflows.

Advance your sterile filtration strategy

Intended use of the products mentioned on this page vary. For specific intended use statements, please refer to the Instructions for Use for the product.