3.2 Scale translation of HEK293T stable producer cell line
culture at matched mixing time
The scalability of cell culture performance such as growth kinetics and
LVV productivity was investigated in 24-DSW microtiter plates (5 mL
scale) and stirred tank reactors (2 L scale). As described earlier,
mixing time was chosen as the basis for scale translation. Table 2
summarises the operating conditions selected in each of the two vessel
formats for operation at matched mixing time of <10 s. The
mixing time obtained in the STR under platform operating conditions was
selected as the benchmark. For the 24-DSW plate, the mixing time was
matched at shaking speeds ≥ 250 rpm for all fill volumes examined. A
larger fill volume is more advantageous since there is greater scope for
analytics. It also means sacrificial well sampling can be avoided thus
permitting a higher experimental throughput. Hence, 5 mL was selected as
the initial microwell fill volume. This was reduced to 2.5 mL at the
harvest time point as the culture was sampled from the same well each
day. It should be noted that a constant mixing time is still achieved
for this range of working volume at 250 rpm as supported by Figure 2B.
We also demonstrated comparable cell culture profiles between wells with
reducing volume (i.e. same well sampling) and the sacrificial well
sampling control with 5 mL culture volume (see Figure S1 in the
Appendix). Hence, the reduction in volume up to 2.5 mL does not have any
impact on cell culture performance, thus, validating the sampling
approach used in this study.