Response: Deciphering the Burgess Shale of single-use bioreactors
Having worked with both -stainless steel and disposables - here a remark on the "best" systems that has been overlooked. Its' rise to becoming a dominant subspecies in the family of bioreactors may be mediated by superior performance in comparison to all other systems, being disposable or not.
Key to all reactors is the need to provide homogeneity and efficient gas transfers in/out efficiently. This is expressed in a single number that has the funny name kLa and its dimension is "per h". Stirred tanks, when running with air, have a kLa between 2 and 4 (run under conditions for mammalian cell culture). The same is true for any of the disposable versions, including the famous Wave bioreactor. My academic group (LBTC/EPFL), together with the companies Kühner AG and ExcellGene SA (both in Switzerland) has developed a new reactor system using an orbitally shaking cylindrical vessel. Here we find, under cell culture suitable conditions kLa-values of >10, even at the 1000 Liter scale (check website: http://www.excellgene.com/technologies.php, publication: S.Tissot et al. 2010: Determination of a scale-up factor from mixing time studies in orbitally shaken bioreactors, Biochemical Engineering Journal doi10.1016/j.bej.201008.005.)
Simple manufacturing processes can be applied, requiring less operator interaction, less power input, no pure oxygen, less pH control intervention. The reactors generate very little foam, the gas transfer is occurring through the liquid - gas interface (free surface of the rotating liquid bulk) only. Surprisingly, the mixing times in these reactors are shorter than in any other system we have worked with. The reactors are made of a holding tank into which a disposable bag can be inserted (OrbShake™ bioreactors).
Florian M Wurm
Prof. of Biotechnology
Swiss Federal Institute of Technology Lausanne (EPFL)
Lausanne, CH