The application of shaken bioreactors for cell cultivation has increased enormously in the last eight years. These bioreactors are used for the expression (transient and stable) of recombinant proteins in drug and diagnostic research. Extensive tests demonstrate their potential in terms of performance, flexibility, and cost-effectiveness when compared with more conventional technologies.
Shaken bioreactors are typically operated in a temperature-, CO2-, and humidity-controlled environment. For medium-scale work with volumes from 50 mL up to 1 L of culture medium, disposable Erlenmeyer flasks, both with small bottom baffles and without baffles, are most commonly used.
For smaller scale work, the use of microtiter plates (12, 24, 48, and 96 well) has been established. Here evaporation is the most important issue; this can be partially solved using a humidified environment and special plastic membrane lids for the microtiter plates.
Special centrifuge tubes, so called TubeSpin® bioreactors (Techno Plastic Products), with a working volume from 5 mL to 35 mL, have a ventilation cap and cover the range between the small- and the medium-scale work. Compared to the spinner flask, shaking technology has two major advantages—a single motor can provide shaking activity to numerous bioreactors, and there are no complicated or cost intensive moving parts in the shaken bioreactor, while providing very efficient mixing. Both spinner and shaker systems do have one important parameter in common: low shear stress.
Ten years ago, C.M. Liu, a Roche researcher who sought to capitalize on the low shear stress benefit, developed a simple system in which cell cultivation was carried out in 50 L cylindrical vessels on an orbital shaker. The 50 L vessels had a working volume of 36 L, and the head space was actively aerated by a mixed gas.
Inspired by this simple and successful idea, Jochen Büchs, professor of biochemical engineering at RWTH Aachen University conducted research using the same vessel size. Mixing time and heat transfer were characterized. Professor Büchs’ team then performed parallel cultivations in shaken and stirred bioreactors with plant cells, which showed closely matching results.
Subsequently, Professor Florian Wurm, professor at EPFL and founder and CSO at ExcellGene, and Kühner began to develop the next generation of shaken bioreactors for volumes up to 200 L. Using an orbital shaken bioreactor system rather than existing bioreactor systems, offers several advantages.
The orbital shaken bioreactor (SB200-X) is designed without baffles and aeration through the head space means no breaking bubbles and little foam formation. Together these features deliver low shear stress since the bulk of the liquid is exposed to laminar flow only. The disposable bag for the shaken system is simple in design and also cost effective because, unlike the stirred disposable system, there are no moving parts (stirrer) involved.
The ability to scale-up is easier with the shaken bioreactor as the fluid hydrodynamics are comparable from microliter volumes all the way up to 200 L. In addition, the system provides flexibility by covering a wide range of working volumes from 50–200 L.