Biomedical Engineering Reference
In-Depth Information
Modular Systems
Modular systems of connecting disposable bags will obviate the need for
scale-up and allow custom manufacturing of variable batch sizes. Only mix-
ing validation will be required, which can be readily demonstrated.
Gentle Mixing
Upstream systems have historically been very rigorous; the new findings are
that all cells and organisms grow much better when they are allowed to grow
in colonies, which means providing gentler mixing systems. This profile is
well delivered in 2D bag bioreactors only as 3D still require propellers and
mixing systems similar to what is used in the stainless steel bioreactors.
2D Bags
Disposable bags will mainly be of the 2D type as this is the cheapest form,
and the hybrid disposables that are designed to provide a liner to the exist-
ing stainless steel-type bioreactors with disposable mixing attachments will
fade because of their high cost without any additional benefits. Every type of
cell and organism will be adequately grown in 2D plastic bags with innova-
tions in the designs of the bags to meet the growth requirements (see
www.
mayabio.com
)
. The problem with 2D bags lies in the difficulties encountered
when handling larger volumes and also to hold. For example, the only large
commercial 2D bag bioreactor comes from GE (the Wave Bioreactor); beyond
the 500 L media, the bags would not be able to hold the weight as it is rocked.
However, recent filings with the U.S. Patent and Trademark Office show that
a new class of stationary bioreactors will soon be appearing where the 2D bag
is kept stationary (thus, eliminating any size constraints) and the aeration is
provided through proprietary ceramic spargers. The 3D bag technologies as
currently promoted by all major equipment manufacturers require disposal
mixing systems preinstalled and that adds substantial ongoing costs, while
the starting equipment also adds substantial capital investment. Today, the
cost of a disposable 3D bioreactor is just about the same as the stainless steel
bioreactors. The use of 2D stationary bags will cut down the capital cost by
more than 50%.
