Understanding the Options

Microbial Cell Culture Clarification:
Intracellular Protein (cytoplasmic or periplasmic)

Intracellular Protein Clarification: Cell Harvest

• Cell recovery from the fermenter broth, elimination of waste fluid in the filtrate
• High solids content in feed stream, which makes centrifugation a viable technology option
• Feed stream quality can vary depending on cell type and culture conditions

Recommended Filter	Filter Characteristics
TFF with Microfiltration Membrane Prostak Open-Channel Modules with 0.22 µm or 0.1 µm Durapore Membrane	Open-channel design ideal for fluids containing high cell densities and solids High flux at low transmembrane pressure Robust construction allows multiple use Validated for multiple SIP cycles Selection of 0.22 µm or 0.1 µm membrane depends on particle size distribution in feed solution. Choice should be based upon small-scale testing.

Lysate Clarification

• Removal of debris, particles and colloids generated during the lysis step, and product recovery in filtrate fluid
• Feed stream quality can vary depending on cell culture type and lysis conditions
• Challenging separation due to large amount of particles and wide range in size
• Typically requires several process steps in series (primary clarification then polishing filtration)
• Centrifugation is a viable option as first separation step, but still requires downstream polishing filtration

Recommended Filter	Filter Characteristics
Primary Clarification -- TFF Prostak Open-Channel Modules with 0.22 µm or 0.1 µm Durapore Membrane	Open-channel design ideal for fluids with high solids levels High flux at low transmembrane pressure Robust construction allows multiple use Validated for multiple SIP cycles Selection of 0.22 µm or 0.1 µm membrane depends on particle size distribution in feed solution. Choice should be based upon small-scale testing.
Pellicon V Screen Cassettes with 0.22 µm or 0.1 µm Durapore Membrane, or 1,000 kD Biomax Membrane	More suited for lower cell density and solid content fluids Suspended screen in feed channel allows higher turbulence enhancing separation process Complete range of devices for easy scale-up Selection of 0.22 µm, 0.1 µm or 1,000 kD membrane depends on particle size distribution in feed solution. Choice should be based upon small-scale testing.
Polishing Filtration – Depth Filtration Triple-layer Millistak+ HC Filters (Grade A1HC or B1HC) Disc Filters Pod Filters	Triple-layer configuration includes a membrane bottom layer to enhance filter loading capacity and retention Higher filtrate quality allows smaller size requirements for downstream sterilizing-grade filtration step Unique design enables the compression of multiple process steps into one, lowering overall filtration costs The selection of Grade A1HC or B1HC depends on the fluid particle size distribution and should be based on small-scale testing.

Sterile Filtration: Bioburden Reduction

• Reduces bioburden
• Protects downstream chromatography and UF/DF steps
• Maintains yield of dilute protein and preserves purity
• Sterilizing-grade filtration required

Recommended Filter	Filter Characteristics
Single-layer Durapore 0.22 µm PVDF Filters Cartridge Filters Optiseal Cartridge Filters Opticap Capsule Filters Optiseal Capsule Fitlers	Sterilizing-grade PVDF membrane won’t bind valuable protein 100% Integrity tested to ensure proven performance Can be integrity testable on-site Although 0.22 µm is typical for this application, Durapore filters are available in several pore sizes and, in single-layer or multi-layer configurations to accommodate the needs of each user, the degree of protection required for the downstream process and the plugging characteristics of the fluid. Choice should be based on small-scale testing.
Millipore Express SHC 0.5 µm + 0.2 µm PES Filters Cartridge Filters Opticap Capsules Optiscale Capsules	Sterilizing-grade PES membrane providing broad chemical compatibility across a wide pH range (1–14) Robust construction validated for multiple SIP cycles 100% integrity tested to ensure quality Asymmetric pore structure delivers extremely high flow rates at low pressure drop Can be integrity tested on-site Although double-layer 0.5 µm + 0.2 µm (SHC) is typical for this application, single-layer 0.2 µm (SHF) is also available. The degree of protection required for the downstream process and the plugging characteristics of the fluid will guide this selection. Choice should be based on small-scale testing.