N-1 perfusion refers to the use of an XCell™ ATF device to achieve high cell density in the seed train step before the production bioreactor (N),  achieving a more rapid and robust process while maintaining an existing Fed-batch based production scheme. 


N-1 perfusion refers to the intensification of cell growth in the step prior to the production bioreactor (N). This process intensification is done using perfusion in the N-1 bioreactor to attain high cell density and viability. This allows seeding the production bioreactor at a higher starting cell density and shortening the production bioreactor run time. This can dramatically increase the facility output without direct change to the core production process.  A robust cell retention device is required to attain a high cell density inoculum for the production bioreactor.

Benefits of N-1 perfusion include:

  • Increased Fed-batch process efficiency
  • Time and cost savings
  • Reduced operational risk
  • Smaller bioreactor footprint

High cell density perfusion can impact Fed-batch production to shorten process time in two ways.

1. High cell density seeding of the production bioreactor (N) - the XCell™ ATF System is attached to the N-1 bioreactor

2. Removal of the N-1 bioreactor, if the N-2 bioreactor can provide enough cells for the production bioreactor (N) - the XCell™ ATF System is attached to the N-2 bioreactor


XCell™ ATF Cell Retention System
  • Continuous, provides clarified harvest ready for capture chromatography
  • Efficient, delivers 100% cell retention, increases productivity
  • Convenient single-use format reduces implementation time by up to 80%
  • Intensified, generates high cell concentration and viability
  • Flexible, connects to any bioreactor and can be used in a variety of applications
  • Gentle, reduces cell stress, increases cell viability and productivity
  • Easy to use, reduces setup time and user training
  • Scalable, adapts from development-scale to production-scale
  • Self-cleaning, reduces biofilm build up on the hollow fiber filter

Learn more about the XCell™ ATF System

Higher seeding densities achieved through use of the XCell™ ATF System helped reduce production reactor time from 14 days to 8 days.

Viable Cell Density (VCD) and Viability

Production Fed-Batch: Cells were inoculated directly from n-1 perfusion bioreactor at 0.5E6 and 10E6 cells/mL seeding densities. 

mAb Titer

Comparable titer was observed at high seeding density production Fed-batch bioreactor, in shorter time.

Specific Productivity

The cell specific productivities are very similar (~6.3 pg/cell/day) for both 0.5E6 and 10E6 cells/mL seeding densities in production Fed-batch.

See poster

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