To determine the maximum number of cells that could be
grown per mL in suspension culture, a growth study was performed
using DMEM/F12 with and without HEPES supplemented
with 1 and 5% KSR with an initial cell seeding density of
7.0 105 cells/mL. Comparisons were made between cells grown
in DMEM/F12 with and without HEPES. A slower and lower
saturation density of 8.5 105 cells/mL was recorded for the
medium supplemented with 1% KSR (data not shown) (Fig. 2). On
the contrary, cells grown with medium supplemented with 5%
KSR grew faster and to a higher saturation density of
6.0e7.0 106 cells/mL after 144 h with daily medium change
(Fig. 3). No significant difference was noticed when cells were
grown in DMEM/F12 medium with (6.0e7.0 106 cells/mL) or
without HEPES (6.0 106 cells/mL). This shows that DMEM/F12
with HEPES may not increase the cell number significantly and the
changes in pH are not likely sufficient to affect growth under the
condition tested. Doubling time of approximately 39 and 21 h
were recorded for cells grown with 1% and 5% KSR respectively.
Based on these results, the 5% KSR medium will be better suited
for the production of the cells at industrial level due to faster
growth kinetics. The 5% KSR medium supplementation was then
used in growth related experiments throughout the study