Multiphase stirred‐tank bioreactors – New geometrical concepts and scale‐up approaches

Abstract

A frequently observed lag time at the beginning of settling is caused by initially very small drops. Only when the drop size reaches a certain size due to coalescence, the sedimentation velocity becomes large enough to visually observe sedimentation. A so-called close-packed zone, where drops are in direct contact with several drops and stacked up to the interface, does not necessarily exist. On the other hand, there is a zone where the drops sediment freely at high holdup. These findings completely change the interpretation of settling tests, their modeling, and ultimately the design of settlers.

Engineering characterization of the novel Bach impeller for bioprocessing applications requiring low power inputs

“…It is obvious that depending on the cell type and target product, some impellers may be more suitable than others. Indeed, the large variety of cell types and applications for which stirred-tank bioreactors have been used necessitated the development of a multitude of stirrer designs to meet the specific needs of the production system and mitigate risks depending on the processing requirements of the biological entities (Böhm et al, 2019). A common goal of impeller design and development, however, may be formulated as achieving efficient mixing, off-bottom suspension, and solids homogenization (if required) at the lowest possible power input (Jaszczur et al, 2020).…”