Prefilters & Bioburden Control

Multiple filters of different formats and sizes. On left of image are larger white T-line capsules while front center shows smaller white capsules for process development. Back center shows blue Opticap® XL capsules with cartridge filters on right side.

Prefilters are a cost-effective, proven technology used throughout bioprocessing to remove particulates, reduce bioburden and improve processing efficiency.

Our prefilter portfolio includes:

  • Milligard® PES membrane prefilters: gamma-compatible, bioburden reduction filters supported by the Emprove® Program, and are the best choice for most pharma and biopharma applications.
  • PolySep II ™ or Milligard® prefilters: autoclave compatible and may provide the performance you need for more challenging applications.

All prefilters are:

  • Offered in multiple pore sizes for efficient filtration of different process streams
  • Available in OptiScale® formats for efficient screening and scaling
  • Available in capsule and cartridge formats with multiple connection options for reliable scaling from bench- to production-scale processing

For help determining the right filter for your process, contact us.

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Two capsule filters connected by single use tubing with tubing extending from inlet of the Milligard® PES capsule on left to the sterilizing Millipore Express® capsule filter on right, and from the outlet of the Millipore Express® capsule to a sterile connector, which would connect to the next operation.

Milligard® PES Filters

Milligard® PES filters offer polyethersulfone (PES) membranes in three pore sizes. These prefilters increase the capacity of sterilizing filters or protect unit operations from particulate impurities. They can also be used as standalone bioburden reduction filters in processing steps that may not need a sterilizing filter.

Key Benefits

  • Validated bioburden reduction claims (1.2/0.2 µm nominal, 1.2/0.45 µm only)
  • Fast flow and high throughput
  • Available in gamma-compatible formats, that can be integrated into Mobius® single-use assemblies
  • Available in capsule and cartridge formats
  • Supported by the Emprove® Program

Membrane Pore size and Retention Specifications

For more detailed information on how Milligard® PES filters improve processing efficiency:

A white capsule and cartridge filters of different sizes. On left, lying down are 20 and 30 inch cartridge filters, with smaller cartridge filters standing upright. Capsules are standing upright on right side of image. while front center shows smaller white OptiScale® 47 capsules.

PolySep™ II filters

  • Mixed media of borosilicate glass microfiber and mixed esters of cellulose.
  • Pore sizes: 1.0/0.2/0.1 μm, 1.0/0.2 μm, 1.0/0.5 μm,  1.0/1.2 μm, 2.0/1.2 μm.
  • High capacity prefilters for removing particles from plugging, viscous, and challenging streams.
  • Available in both capsule and cartridge formats.

Milligard® filters

  • Mixed esters of cellulose on a polyester web.
  • Pore sizes: 0.2 μm, 0.5 μm, 1.2 μm, 0.5/0.2 μm, 1.2/0.5 μm.
  • High particle and retention capacity prefilters for use upstream of sterilizing filters.
  • Available in both capsule and cartridge formats.

Our Tech Note shows comparative performance of Milligard® PES filters with Polysep™ II and Milligard® filters.

Formats From Bench to Production Scale

Optiscale® capsules are designed to quickly assess performance or estimate area requirements for larger-scale processes.

Approximate filtration areas of capsule and cartridge filters. Refer to product specifications for complete information.


Milligard® PES, Milligard® and Polysep™ II filters are designed, developed, and manufactured in accordance with a Quality Management System approved by an accredited registering body to an ISO 9001 Quality Systems Standard, and supported by a certificate of quality.

Each Opticap® XL, XLT, T-line, Small Scale 300 capsule and cartridge filter is supported by a validation document for compliance with regulatory requirements. For traceability and easy identification, each filter is marked with identifying characteristics.

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