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.