Characterization and Engineering Performance of the Allegro™ STR 2000 Single-Use Stirred Tank Bioreactor

Single-use bioreactors have only been cylindrical in design, until now.

Introduction

Stirred tank reactors (STRs) have become the prevalent choice for the commercial manufacture of therapeutic proteins from suspension cell lines.  Process performance in this scalable family of bioreactors is strongly influenced by the efficiency of bulk fluid mixing and the oxygen mass transfer coefficient (k_La). The success of traditional stainless steel STR systems lies in their direct impeller driven agitation that can deliver a wide range of specific power inputs to the fluid. The Allegro range of single-use stirred tank bioreactors has adopted this direct driven impeller technology, which allows a wide range of specific power inputs to be achieved. In addition, modifications to current design features utilized with other single-use bioreactor technologies in the market place today, have been implemented for increased ease of use and process assurance.

Performance characterization of the Allegro STR 2000 bioreactor in terms of mixing, mass transfer (oxygen mass transfer and CO₂ stripping efficiency), and temperature control demonstrates good performance at a wide range of agitation speeds. The Allegro STR range has been designed to provide a predictable scale-up performance modeling, therefore, the comparison of the mixing and mass transfer capabilities across the bioreactor range is presented with consistency from reactor to reactor at specified volume sizes. This information can help significantly in the selection of operating parameters during process transfer, including scale-up and scale-down, from bench-scale and stainless steel reactors. This leads to a reduction in the time required for additional development that may be needed for internal engineering performance modeling, and aids with conceptual understanding of how the cell line may perform during the process.

This information can help significantly in the selection of operating parameters during process transfer, including scale-up and scale-down, from bench-scale and stainless steel reactors. This leads to a reduction in the time required for additional development that may be needed for internal engineering performance modeling, and aids with conceptual understanding of how the cell line may perform during the process.

Material and Methods Equipment

• Allegro STR 2000 single-use bioreactor system (Pall)
• Allegro STR 1000 single-use bioreactor system (Pall)
• Allegro STR 200 single-use bioreactor system (Pall)
• Polarographic oxygen sensor InPro 6850i (Mettler-Toledo)
• pH sensor InPro 3250i (Mettler-Toledo)
• pCO₂ sensor InPro 5000i (Mettler-Toledo)
• M800 transmitter (Mettler-Toledo)
• National Instrument CompactDAQ using a multi-purpose Compact RIO I/O module
• Probe bellows (Pall)
• Kaye Validator (GE)
• Temperature control unit (TCU) (Pall)
• Chiller (MTA)

Materials

• Media simulant (Xing et al, 2009)
• 4 M NaOH (Sigma-Aldrich)
• 5 M HCl (Sigma-Aldrich)

Allegro STR Design

The Allegro STR range of bioreactors has been designed to provide scalable cell culture performance by incorporating the principals of successful scale up from traditional stainless steel reactor vessels, mainly by maintaining similar geometries across the range. The only exception to this is for the Allegro STR 2000 bioreactor, where the impeller size was maintained the same as the Allegro STR 1000 bioreactor, thus improving manual handling, operation and disposal of biocontainer, as well as achieving target k_L a and power with the smaller impeller aspect ratio. Despite the reduction in the size of the Allegro STR 2000 impeller relative to the volume, a high specific power input is still achieved, resulting in similar engineering performance parameters between the Allegro STR 2000, 1000 and 200 bioreactors. The key dimensions of the Allegro STR range are shown in Table 1.