A bioreactor fermenter is a controlled vessel that keeps living cells or microorganisms in the conditions they need to grow and produce. We build these every week, and the job never changes: hold a defined working volume, mix it, feed it, and keep temperature, speed, pH, DO and foam steady while the culture works.
What is a bioreactor fermenter?
The two words get used loosely, so it helps to separate them. A bioreactor is any vessel that supports a biological reaction. A fermenter is a bioreactor aimed at microbial fermentation, though in practice most labs use the terms interchangeably for the same stirred-tank hardware. Either way, you are looking at a sealed vessel with a stirrer, ports for sensors and feeds, and a jacket or coil for temperature control.
The reason the category exists is control. You can grow bacteria in a shake flask, but you cannot hold pH, keep dissolved oxygen where you want it, or feed the culture on a schedule. A fermenter turns all of those into set points you dial in. That is the whole point of the vessel: it takes a biological process that would otherwise drift and pins it to numbers you can reproduce.
What does a fermenter actually do?
Strip away the branding and a fermenter does five things at once. It contains the culture in a sterile boundary. It mixes so cells, nutrients, gas and heat are evenly distributed. It transfers oxygen into the liquid for aerobic cultures. It holds temperature. And it measures and corrects the process variables that decide whether your culture thrives or crashes.
Glass Fermentation Tank specifications
These figures come straight from our Glass Fermentation Tank spec sheet, so you can size a unit against real numbers rather than generic ranges.
| Total volume | 1L, 2L, 3L, 5L, 7L, 10L and multi-vessel configurations |
|---|---|
| Material | 316L stainless steel + borosilicate glass |
| Stirring | Magnetic-drive mechanical stirring; top or bottom pin-free magnetic coupling options |
| Sterilization | Off-site autoclave sterilization |
| Basic controls | Temperature, speed, pH, DO, foam control and feeding |
Those variables are not a mystery. Across our fermentation tanks the basic control set is temperature, speed, pH, DO, foam control and feeding. Larger units add air flow and tank pressure to that list. Each one has a sensor going in and an actuator responding: a pH probe triggers acid or base dosing, a DO probe drives the stirrer speed or gas mix, a foam sensor cuts in antifoam. The vessel is the stage; these loops are what make it a fermenter rather than a jar.
Here is the sequence a batch runs through, from empty vessel to harvested product.
What is inside the vessel?
This is where competitor overviews tend to go vague, so it is worth being concrete. A stirred-tank fermenter is built around a body, an agitation system, a set of ports, and a temperature-control surface. The glass units we make use a 316L stainless steel head and base with a borosilicate glass barrel, so you can see the culture; the larger and industrial units are full 316L or 304 stainless steel because you no longer need to look inside and you do need the strength.
Agitation is the part people underestimate. Our glass tanks use magnetic-drive mechanical stirring with top or bottom pin-free magnetic coupling options, which keeps the seal clean because nothing mechanical crosses the vessel wall. The larger laboratory tanks offer top mechanical stirring or magnetic-drive stirring depending on the scale and the shear the culture can tolerate. The stirrer is what sets your oxygen transfer and your mixing time, so it is not a detail you skip past.
Every functional variable you saw in the control set needs a port: a temperature sensor, a speed reference, a pH probe, a DO probe, a foam sensor, a feed line. On the larger vessels you also route air flow and monitor tank pressure. When someone asks how many ports they need, the honest answer is: count your control loops, because each loop is a physical penetration into the vessel.
Why does working volume matter more than total volume?
Every spec sheet, including ours, lists total volume first: our glass tanks run 1L, 2L, 3L, 5L, 7L and 10L plus multi-vessel configurations, and our laboratory bio tanks run 10L, 15L, 20L, 30L, 50L, 75L, 100L, 150L, 200L, 300L and 500L. Those are the sizes of the vessels. They are not the volume of culture you actually run.
You always leave headspace. Gas comes out of solution, aeration and stirring throw up foam, and the sensors and sparger need clearance above the liquid. So the working volume, the amount of culture the vessel actually holds, sits below the total volume. We do not publish a fixed ratio because the right headspace depends on how much your culture foams and how hard you aerate; a low-foam culture at gentle aeration keeps more of the vessel usable than a protein-rich broth that you have to fight with antifoam. The judgment is: size the vessel by the working volume you need, then step up to the next total volume, not the one that matches your batch on paper.
This is the single number competitor articles skip, and it is the one that decides whether you buy a 10L or a 15L. If your process never runs more than a certain batch, there is no reason to buy the tank whose total volume equals it exactly.
What is a fermenter used for in the lab?
In practice a lab fermenter earns its place in three jobs. The first is small-scale and multi-vessel experiments, which is exactly what our glass fermentation tanks are for: run several 1L to 10L vessels side by side, change one variable per vessel, and read the culture through the glass. That parallel setup is how you screen strains or media without burning weeks on sequential runs.
The second job is process development, taking a result from the bench toward a pilot. Our laboratory bio fermentation tanks cover microbial and cell-culture development from bench scale toward pilot validation, which is why they add in-situ steam sterilization and controls for air flow and tank pressure that the small glass units do not need. Once you are validating a process rather than screening ideas, in-place sterilization stops being a convenience and becomes a requirement.
The third job is production, and that is where an industrial stainless steel fermentation tank comes in, running from laboratory and pilot sizes up to production-scale configurations as a single tank or a multi-stage fermentation system. Most labs never own this one, but knowing it exists matters, because the whole reason you develop a process on a bench-scale tank is so it scales to production-scale configurations without surprises.
Glass or stainless steel: which vessel fits your stage?
The choice is not about quality; both are 316L-grade builds. It is about what you are doing at your stage. Glass lets you see the culture and swaps quickly between small vessels, which is why it dominates screening. Stainless steel carries in-situ steam sterilization, higher pressure and larger volumes, which is why it dominates once you are developing and producing. The table below lays the three families side by side so the boundary is visible.
Read it as a staircase, not a menu. You screen on glass, you develop on the laboratory bio tank, and you produce on the industrial tank. The sterilization row is the clearest tell: off-site autoclave is fine when you can carry a 5L vessel to the autoclave, but the moment your vessel is too big to move, in-situ steam sterilization stops being optional.
How do you pick the right size and configuration?
Fermentation tank selection comes down to vessel volume, agitation, temperature support and process-control requirements, in that order. We size these every day, and the checklist is short and unglamorous. Confirm the working volume you actually need. Confirm the agitation the culture tolerates, since a shear-sensitive cell line and a robust bacterial strain want different stirrers. Confirm your temperature-control support. Confirm your sterilization route, which is the fork between glass with off-site autoclave and stainless with in-situ steam. Then confirm your sensor requirements and whatever downstream equipment the broth feeds into.
Notice what is not on that list: a single “best” tank. There isn’t one. The right vessel is the smallest configuration that holds your working volume, tolerates your culture’s shear, and carries the sterilization your protocol demands. Get those three right and the rest of the spec follows.
Frequently asked questions
Is a bioreactor the same as a fermenter?
In everyday lab use, yes. Strictly, a bioreactor is any vessel supporting a biological reaction and a fermenter is one aimed at microbial fermentation, but the stirred-tank hardware, the ports, the control loops and the sizing logic are the same. When you are choosing equipment, treat them as one category and focus on volume, agitation and sterilization instead of the label.
What working volume can a fermenter actually hold?
Less than its total volume, because you always leave headspace for foam, gas disengagement and sensor clearance. We do not quote a fixed percentage because it depends on how much your culture foams and how hard you aerate. Size the vessel by the working volume you need, then step up to the next total volume so you are not running the tank at its brim.
Do I need in-situ steam sterilization or is autoclaving enough?
It depends on whether you can physically move the vessel. Our small glass fermentation tanks use off-site autoclave sterilization, which is fine at 1L to 10L. Our laboratory bio and industrial stainless tanks use in-situ steam sterilization because once a vessel is too large to carry to an autoclave, sterilizing it in place is the only practical option.
What controls come standard on a lab fermenter?
Across our fermentation tanks the basic control set is temperature, speed, pH, DO, foam control and feeding. The larger laboratory and industrial units add air flow and tank pressure. Each control is a sensor-plus-actuator loop, so the number of controls you specify also sets the number of ports the vessel needs.
Can I run several fermenters in parallel?
Yes, and for screening you should. Our glass fermentation tanks are offered in multi-vessel configurations precisely so you can run 1L to 10L vessels side by side, change one variable per vessel, and compare cultures directly. Parallel small vessels are how you screen strains and media without turning every experiment into a sequential wait.
Choosing your vessel
If you are screening strains or media, start with a glass fermentation tank in a multi-vessel setup so you can watch the culture and run variables in parallel. When you move from screening to validating a process, the laboratory bio fermentation tank with in-situ steam sterilization is the vessel that carries you from bench toward pilot. And when a validated process is ready to scale, an industrial stainless steel fermentation tank built as a single tank or multi-stage system takes it to production. You can see the full range on our fermentation tank category page, and if you are weighing sizes against your process, our selection guide walks through working volume, agitation and sterilization the same way we size vessels ourselves. For a deeper split of the hardware, our companion pieces on the three types of bioreactor fermenter and the fermenter components inside the vessel go one level deeper than this overview.