Biomedical Engineering Reference
In-Depth Information
FIGURE 5.7
Xcellerex bioreactor.
(a proof-of-concept reactor) is a bag bioreactor with a Vibromixer, where the
movement of a perforated disk fixed on a vertically oscillating hollow shaft
causes an axial flow in the bag, which mixes and aerates the cells. The form,
size, and position of the conical drill holes on the disk affect the fluid flow
and oxygen transfer efficiency in the bag and contribute to the elimination
of vortex formation. Similarly, the BayShake Bioreactor achieves vertical
oscillation in which the culture broth oscillates in a surface-aerated cube-
shaped bag.
The bubble bioreactors are exemplified by Nestle's Slug Bubble Bioreactor
(SBB), which generates intermittent large, long, bullet-shaped bubbles termed
“slug bubbles” that occupy nearly the entire cross section of a tube, are gen-
erated at the bottom of the bag, and rise to the top. To provide a determined
quantity of air at a given frequency, a solenoid valve is used to control bubble
generation. Varying the air inlet pressure and the valve opening time con-
trols the quantity of air and the bubble frequency.
The Bioreactor System (PBS) works with an air-wheel design and a dual
sparger system for efficient mixing and aeration. In the case of the CellMaker
systems (Cellexus Biosystems), the unique asymmetric shape of the culture
bag is significant. The CellMaker Regular is a single-use bubble column.
This system is preferable for microbial productions. The version specific to
animal cell cultivations is the hybrid CellMaker Plus, where pneumatic and
mechanic drives are combined. Mixing and aeration is achieved by trans-
verse liquid movement. While the airflow is induced by a sparger tube, the
two magnetically driven propellers intensify the “riser” flow. Excessive
foam formation, which is linked to flotation and is a well-known problem
in bubble columns, may be minimized or even eliminated by applying pres-
sure to the headspace within the bag.
