Understanding the Options

Microbial Cell Culture Clarification:
Protein Refold Pool Clarification

Clarification

• Removal of haze formed during refold process after product protein solubilization
• Mostly small sub-micron particles
• Some fluid variability depending on refold process conditions

Recommended Filter

Filter Characteristics

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.