# Single-use bioprocessing

Why disposable flow paths change the physics and the quality logic of a bioprocess — gamma sterilisation instead of steam, supplier qualification instead of cleaning validation, and a polymer wall that leaches into the culture.

Replacing steel with irradiated plastic film moves the hard problems rather than removing them: sterility becomes a supply-chain property and the vessel wall becomes a chemical participant.

Source: https://en.bioecon.ru/docs/bioproduction-equipment/upstream-bioreactors/single-use-bioprocessing/
Updated: 2026-09-06



A stainless steel bioreactor is sterilised in place with saturated steam and cleaned in place between campaigns, and both operations are validated by the operator. A single-use system arrives sterile, is used once, and is discarded. Everything that follows from disposability is a consequence of that one substitution, and the substitution is not neutral.

## Sterility becomes something you buy

Steam sterilisation is a kinetic process the plant controls and measures: time at temperature against a known thermal death curve. Single-use assemblies are sterilised by gamma irradiation, typically at doses in the 25–50 kGy range, before shipment. The user cannot re-run it, cannot verify it directly, and cannot repair a breach in the barrier. Sterility assurance therefore migrates from an operation into a supplied attribute, which is why the audit burden moves to the film manufacturer, the moulder and the irradiator, and why bag integrity testing before use exists at all. Steam also destroys nothing but organisms; gamma radiation deposits energy in the polymer as well, breaking chains and consuming the antioxidants added to stabilise the film. The dose that makes the bag sterile is the same dose that changes its chemistry.

## The wall is no longer inert

A bag is a multilayer laminate: a polyethylene product-contact layer for weldability and low extractables, an ethylene vinyl alcohol layer as the oxygen and carbon dioxide barrier, and an outer structural ply, with tie layers between. Only the contact layer touches the culture, but small molecules migrate. Extractables are what a solvent can be forced to pull out under exaggerated conditions; leachables are what actually enters the process fluid in use. The distinction matters because the second set is the one a regulator cares about and the first is the only one that can be characterised in advance — which is why extractables data is generated by the supplier and leachables studies remain process-specific. Polymer additives, oligomers, slip agents and irradiation degradants all appear in these datasets, and a compound present at parts per billion can still be biologically active. Detail on that failure mode is in [single-use bag bioreactors, 50 L to 2000 L](../single-use-bag-bioreactors-50l-2000l/).

## What it costs in transport

Disposable vessels are usually unbaffled, often with an undersized or magnetically coupled impeller and a bag geometry constrained by how the film folds. Against the framework in [high cell density culture systems](../high-cell-density-culture-systems/), that means lower achievable power per unit volume and lower kLa at equal working volume than a comparable steel tank, so the oxygen ceiling arrives earlier. The trade is real and usually accepted, because most single-use duty is mammalian cell culture with modest oxygen demand, seed expansion, or buffer and media handling — not high-power microbial fermentation, where the heat and oxygen loads are precisely what plastic cannot serve.

The genuine gains are elsewhere: no cleaning validation between products, so changeover is a physical operation rather than an analytical campaign, and the multi-product facility becomes viable. The cost is a permanent consumable dependency and a waste stream, and the risk register shifts from operator error to supplier variability.