Bioprocess scale-up has to keep cell density and dissolved oxygen uniform across a much larger vessel, where mixing and gas transfer no longer behave the same way they did at benchtop scale.
density(t+1) = density(t) + agitation*mixing - deadZonePenalty*(1-aeration)
- Reactor grid resolution — how finely the vessel's cross-section is sampled to reveal mixing gradients.
- Target cell density — the cell concentration the bioprocess is scaled to reach uniformly.
- Impeller/agitation speed — mechanical mixing intensity distributing nutrients and cells through the vessel.
- Aeration rate — gas sparging rate supplying dissolved oxygen, which drops off in poorly mixed dead zones.
Scale-up failures — a process that works perfectly in a 2L bench reactor but underperforms at 20,000L — are almost always mixing and oxygen-transfer problems exactly like the ones this grid visualizes, not biology problems.