Gas transfer in an external loop bioreactor with built‐in ultrafiltration

Abstract

The SGI Ultrafermenter is an external loop bioreactor with circulation through an ultrafiltration module allowing removal of medium and soluble products during fermentation. The contents are continually circulated during operation and the vessel is also equipped with a stirring turbine. The interaction of these two mixing agents on gas transfer was investigated. Both mechanisms produced similar increments in KLa over their working ranges, with values from approximately 0–700 h−1 at 200 dm3 h−1 airflow. The effects of these two mechanisms on KLa were approximately additive at low values but the combined mixing produced a maximum KLa value also in the region of 700 h−1. The power‐draw of mixing using the two agents was calculated and stirring was found to be 10–20 times more efficient than circulation.