Bioreactor selection: sizing a bioreactor for the work, single-use bioreactors against stainless, and the control and sensor decisions that follow

Sizing and specifying

1. Working volume, and the turndown ratio. The usable range of a vessel is narrower than its nominal volume at both ends, because probes must stay submerged and headspace must be preserved. Ask for the minimum and maximum working volume, since a vessel that cannot run small cannot be used for development.
2. Single use or stainless. Single use removes cleaning and sterilisation validation and shifts cost into consumables and into a supply chain you do not control. Stainless costs more up front, more in utilities and validation, and is cheaper per run at high utilisation. Utilisation is what decides this, not preference.
3. Mixing and gas transfer. Impeller type and sparging arrangement set the oxygen transfer and the shear the culture experiences, and mammalian and microbial processes want very different answers. Specify from the organism and the process, because retrofitting a different impeller is rarely straightforward.
4. Sensors and control. Decide which parameters are controlled rather than merely monitored, and which measurements are in line rather than sampled. Single use vessels constrain sensor choice more than stainless does, and that constraint is easier to accept before the purchase than after.
5. Data and integration. Establish how the batch record leaves the controller and whether it can reach your system of record without manual transcription. A process whose data lives only in the controller is a process whose history is hard to defend later.

Development, scale-up and the parameters that travel

Scale-up works when the parameters that matter are held constant, and which parameter that is depends on the process. Geometric similarity between your development and production vessels makes this much easier, which is an argument for buying within one manufacturer's range rather than assembling a mixed fleet.

A bench system that cannot reproduce the production vessel's mixing and gas transfer behaviour will generate conditions you cannot carry forward, which is an expensive way to save money at the development stage.

Running cost and consumables

For single use, the consumable is the running cost and it is worth understanding the lead time and the supply position as much as the price. A vessel whose bags are on long lead is a vessel that idles.

For stainless, the running cost is utilities, cleaning validation and the labour around turnaround. Both are predictable; the mistake is comparing capital cost alone.

Common questions

What size bioreactor do I need?

Size from the working volume your process needs, not the nominal vessel volume, and confirm the minimum working volume as well as the maximum. A vessel that cannot run at small volumes is not usable for development.

Single use or stainless steel?

Single use where utilisation is moderate, changeover is frequent or cleaning validation is a burden. Stainless where utilisation is high and the process is stable. The deciding factor is how often the vessel runs, not the purchase price.

What is the difference between a bioreactor and a fermenter?

The terms overlap. In common usage a fermenter runs microbial cultures at high oxygen demand and high shear tolerance, while a bioreactor often means a mammalian cell system with gentler mixing. The mixing and sparging design is what actually differs.

Can I scale a process between different manufacturers' vessels?

Yes, but it is harder. Geometric differences change mixing and gas transfer, so more of the process has to be re-characterised. Staying within one geometry family simplifies scale-up considerably.

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