Biology Reference
In-Depth Information
Figure 6. Vessels used in the preparation of a seed train: (A) freezer vial, (B) T-flask, (C) shaker flask,
(D) roller bottle, (E) spinner flask, (F) Cellbag
®
, (G) stirred tank reactor.
Using the conservative estimate of two days for the doubling time (td), the
overall seed train time is n
×
td =20
two days = 40 days, or approximately
×
six weeks.
A backup seed train using cells spun off from an existing seed train may be
initiated if cell numbers allow and if the cell line's productivity remains stable.
Thus, multiple production reactors stemming from a single cell bank vial may
be considered to shorten the overall time to inoculate production reactors. This
approach is an option to the more typical practice of scheduling each produc-
tion reactor to be derived from a single vial thaw.
Production
Once the seed train has generated a sufficient number of cells from the cell
bank, these cells can produce rHuEPO in either adherent mode or suspension
mode. In adherent mode, cells adhere to a solid substrate and secrete rHuEPO
into the liquid cell culture medium. Examples of solid substrates include tis-
sue culture-treated plastic, such as roller bottles or microcarrier beads that may
be made of ceramic or other porous materials. In suspension mode, cells are
freely suspended in liquid medium where they secrete rHuEPO. In cell culture
processes, the three production modes may be used for both adherent and sus-
