Suspension and flow dynamics of the Allegro™ stirred tank reactor

This is the authors' abstract. We don't add key points for this paper.

Microcarrier suspension performance and ensemble-averaged flow fields at the just-suspended 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™ 1, Cytodex™ 3, Cytopore™ 1, and Hillex® 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.