Suspension and flow dynamics of the AllegroTM stirred tank reactor

Microcarrier suspension performance and ensemble-averaged flow fields at the justsuspended condition are studied in a scale-down mimic of the Allegro STR single-use bioreactor range (abbreviated A-STR) and compared to an equivalent standard cylindrical configuration (abbreviated S-STR). Four commercial microcarriers were assessed to determine the required impeller agitation rate and corresponding power input per unit volume to achieve suspension - Cytodex(TM) 1, Cytodex(TM) 3, Cytopore(TM) 1, and Hillex((R)) II microcarriers. The A-STR operating in down-pumping mode (DP) achieved homogenous microcarrier suspension at considerably lower power input when compared to the other baffled configurations. For the A-STR (DP), the power input per unit volume demand was 67.8 % lower than the A-STR in up-pumping mode (UP), 77% lower than the S-STR (DP) and 66.8 % lower than the S-STR (UP). Flow structures investigated at the just-suspended condition, in the transitional regime, were in line with those previously presented in the turbulent regime at considerably higher Reynolds number. This indicates that the normalised flow structures presented in this work are representative of those in the commercial Allegro STR range, despite operating at significantly reduced scale and Reynolds number. Removal of baffles resulted in substantially reduced power input required to achieve homogenous suspension in all configurations - other than the A-STR (DP), which exhibited relatively similar performance to the corresponding baffled configuration. Considering adherent cell sensitivity and mixing implications, and based on the results found in this work, the baffled A-STR (DP) is recommended for achieving microcarrier suspension at the lowest specific power input. (c) 2023 The Author(s). Published by Elsevier Ltd on behalf of Institution of Chemical Engineers. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

This study investigated the microcarrier suspension performance and flow fields in a scale-down mimic of Allegro STR single-use bioreactor range compared to a standard cylindrical configuration. It was found that the down-pumping mode in the A-STR achieved homogeneous suspension at a considerably lower power input compared to other configurations. Flow structures at the just-suspended condition were similar to those in the turbulent regime. Baffles significantly reduced the power input required for suspension, except for the A-STR (DP) configuration.