Transplastomic plants are capable of high-yield production of recombinant biopharmaceutical proteins. Plant
tissue culture combines advantages of agricultural cultivation with the bioprocess consistency associated with
suspension culture. Overexpression of recombinant proteins through regeneration of transplastomic Nicotiana
tabacum shoots from callus tissue in RITA® temporary immersion bioreactors has been previously demonstrated.
In this study we investigated the hydrodynamics of periodic pneumatic suspension of liquid medium during
temporary immersion culture (4 minutes aeration every 8 hours), and the impact on biological responses and
transplastomic expression of fragment C of tetanus toxin (TetC). Biomass was grown under a range of aeration
rates for 3, 20 and 40-day durations. Growth, mitochondrial activity (a viability indicator) and TetC protein yields
were correlated against the hydrodynamic parameters, shear rate and energy dissipation rate (per kg of medium).
A critical aeration rate of 440 ml min-1 was identified, corresponding to a shear rate of 96.7 s
-1
, pneumatic power
input of 8.8 mW kg-1
and initial 20-day pneumatic energy dissipation of 127 J kg-1
, at which significant reductions
in biomass accumulation and mitochondrial activity were observed. There was an exponential decline in TetC
yields with increasing aeration rates at 40 days, across the entire range of conditions tested. These observations
have important implications for the optimisation and scale-up of transplastomic plant tissue culture bioprocesses
for biopharmaceutical production.