4. Conclusion and future prospects
The cyclical semicontinuous operation in a pilot-scale bioreactor using
simplified bioreactor processing yielded consistent maximum total active
rrBChE production levels in the four cycles over 82-days of operation
showing the potential robustness and stability of the transgenic rice
cell cultures for rrBChE production. Here, in best of our knowledge for
the first time, we report the longest plant cell culture bioreactor with
reproducible production of a plant-made therapeutic recombinant protein
in a pilot-scale bioreactor. Using kLa as a scale-up
parameter, the pilot-scale batch culture without baffles provides
comparable growth kinetics, maximum total rrBChE production level,
maximum volumetric productivity and maximum specific productivity as
obtained from the lab-scale bioreactor. Based on Western blot analysis,
the culture medium rrBChE is likely the extracellular rrBChE that is
secreted to the medium via the secretory pathway guided by the RAmy3D
signal peptide. Altogether, we demonstrate a simple, reproducible, and
scalable platform for rrBChE production.
Future work will investigate medium optimization to improve rrBChE
production level and productivities. A cyclical semicontinuous
pilot-scale bioreactor operation without baffles and simplified
bioreactor processes using kLa as a scale-up parameter
is worth studying in a long-term operation (>6 months).
Exploring strategies and methods to mitigate bioreactor wall growth of
cell aggregates and cell lysis is also needed in a long-term
semicontinuous bioreactor operation reported as a better cost-effective
operation than batch operation for plant cell-made biopharmaceuticals
(Corbin et al., 2020).