Appraisal of the mixing performance of Single-Use shaken bioreactors

The pharmaceutical industry is at the forefront of the production of antibodies using mammalian cell-based cultures, with single-use technologies gaining prominence in the manufacturing process. At laboratory scale mammalian cells are usually grown in low shear devices, with disposable shaken bioreactors being largely employed in the early stages of bioprocess development. It has been a recent industry trend to use shaken bioreactors at large scale in the upstream process, performing cell culture in single-use bags which eliminate the need for cleaning in place, offer flexibility and lower production down-times. Single-use Orbitally Shaken Bioreactors (OSRs) consist of a shaker, a structural support to which a disposable bag conforms to and all ancillary connections and controllers. Production scale OSRs with single-use bags, employ the agitation principle of shaken flasks and microwell plates, providing a homogeneously single-use upstream scale-up process thus facilitating scaling-up and simplifying regulatory approval. The aim of the work is to characterize the mixing and flow dynamics in a cylindrical orbitally shaken bioreactor with conical bottoms of different heights. The rationale for a conical bottom is to ease the suspension of cells or microcarriers, which are used for the cultivation of cells not yet adapted for suspend culture, such as legacy cell lines and stem cells. The geometry of the conical bottom was designed so to be compatible with single-use bags, as the conical bottom is truncated and the cone obtuse. This study builds upon previous works of the research group (Weheliye et al 2013, Rodriguez et al. 2013, Rodriguez et .al. 2014, Ducci and Weheliye, 2014) for flat bottom reactors, where increases in Froude number were found to determine a mean flow transition and to increase the turbulence levels. The major objective of the current work is to determine the performances of shaken bioreactors with conical bottom, and to assess to what extent the mean flow and flow regime transitions already identified for a flat bottom are affected by the geometry variation. Particle Image Velocimetry, PIV, and Dual Indicator System for Mixing Time, DISMT, were employed to assess the mixing performances in the bioreactor with a conical bottom. DISMT (see Rodriguez et al., 2014) consists in a colorimetric method where two pH indicators are used to visualise the level of mixing reached after insertion of an acid solution. The findings of the current study provides insight into the flow of a single-use shaken bioreactor and offers a novel approach to design the next generation of products and improve scaling methodologies