By Caleb MorganA continuous stirred tank fermenter, often called a CSTR, keeps fresh medium flowing into a well-mixed vessel while spent broth or wort leaves at the same rate. For home brewers, kombucha makers and small pilot-scale experimenters, that steady-state operation can produce more consistent flavor and cell density than a single batch vessel. This guide covers eight continuous stirred tank fermenter options, grouped by the kind of user each one suits. The selection criteria were working volume, agitation method, temperature and pH control, sterile-port access, material compatibility and how well each design fits a budget or flea-market build. Everything here is based on manufacturer specifications and common owner feedback patterns, not on hands-on testing.
Our Top Picks
Quick Comparison
| Product | Best for | Key feature |
|---|---|---|
| Eppendorf BioFlo 120 | Bench-scale research labs | Integrated DO, pH and temperature control |
| Sartorius Biostat B-DCU | Academic and pilot-scale bioprocess work | Modular controller with multiple vessel sizes |
| Applikon ADI 1025 Bioreactor | Stirred fermentations needing tight control | Glass vessel with programmable agitation |
| New Brunswick BioFlo 310 | Teaching labs and process development | Multiple sensor inputs and data logging |
| Chemglass Benchtop Jacketed Reactor Kit | Budget-conscious glassware builds | Jacketed vessel for temperature control |
| Brewer’s Edge Continuous Ferment Kit | Homebrewers exploring continuous fermentation | Simple inlet and outlet ports for flow |
| Stainless steel conical fermenter with dosing ports | Flea-market builds on a tight budget | Repurposed vessel with added ports |
| Peristaltic pump and tubing kit | Metering feed and effluent flow | Adjustable flow rate for steady dilution |
Eppendorf BioFlo 120
This is a bench-top bioreactor controller aimed at researchers who need reproducible stirred cultures at small volumes. It suits labs that want to model continuous operation before scaling up.
Key specs
- Bench-scale working volumes in the low-liter range
- Integrated control of agitation, temperature, pH and dissolved oxygen
- Compatible with standard glass vessels from the same product line
Pros
- Precise control loops for sensitive cultures
- Well-documented software for recording run data
- Established brand with broad service support
Cons
- Overbuilt for casual homebrew use
- Requires laboratory-grade accessories to run fully
Sartorius Biostat B-DCU
The Biostat B-DCU is a modular bioprocess controller used in academic and pilot settings. It fits users who expect to grow from bench work into larger continuous runs.
Key specs
- Modular design with selectable vessel sizes
- Supports continuous and fed-batch operating modes
- Logs process parameters for scale-up comparison
Pros
- Flexible configuration for different vessel sizes
- Strong data handling for process development
- Widely used in academic bioprocess courses
Cons
- Significant setup and training requirement
- Far beyond the needs of a typical home kitchen
Applikon ADI 1025 Bioreactor
This glass stirred-tank bioreactor is built for controlled fermentations where agitation speed and gas flow need to be tuned tightly. It suits small research groups running repeated continuous experiments.
Key specs
- Glass vessel for visual monitoring of the broth
- Programmable agitation and aeration
- Designed for small laboratory working volumes
Pros
- Clear vessel makes culture behavior easy to observe
- Controller supports repeatable run profiles
- Robust glass construction for routine lab use
Cons
- Glass requires careful handling during cleaning and sterilization
- Accessories and sensors add meaningful complexity
New Brunswick BioFlo 310
The BioFlo 310 is commonly used in teaching labs and process development groups that want multiple sensor inputs and data logging in one controller. It suits instructors and developers who need to explain how continuous systems behave.
Key specs
- Multiple sensor and pump channels
- Data logging for run documentation
- Bench-scale vessel compatibility
Pros
- Good for teaching continuous-flow concepts
- Expandable sensor configuration
- Clear documentation for lab users
Cons
- Learning curve is steep for beginners
- Not designed for home kitchen environments
Chemglass Benchtop Jacketed Reactor Kit
A jacketed glass reactor lets you circulate warm or cool water around the vessel to hold temperature steady. It is a practical choice for builders who want glassware-based continuous experiments without a full bioprocess controller.
Key specs
- Jacketed vessel for heating or cooling by circulating fluid
- Glass body with standard ground-glass ports
- Suitable for stirred, small-volume work
Pros
- Simple temperature control through the jacket
- Glass allows direct visual inspection
- Works with a separate pump and stirrer setup
Cons
- Glass fragility makes it a poor fit for rough handling
- You must supply your own pump, stirrer and tubing
Brewer’s Edge Continuous Ferment Kit
This kind of homebrew-oriented kit provides inlet and outlet ports for feeding and draining a fermenter. It suits brewers who want to experiment with continuous flow without building a full lab rig.
Key specs
- Fermenter with added inlet and outlet ports
- Designed for food-safe homebrew materials
- Compatible with standard brewing tubing
Pros
- Easy entry point for continuous-flow experiments
- Uses familiar homebrew hardware
- Simple setup and cleaning routine
Cons
- Limited sensor and control options
- Steady-state operation still requires careful flow management
Stainless Steel Conical Fermenter with Dosing Ports
A used stainless conical fermenter, fitted with extra ports for feed and effluent, is the classic flea-market route to a continuous setup. It suits budget builders with some welding or fitting skills.
Key specs
- Stainless steel construction, typically food-grade
- Conical bottom for sediment collection
- Added ports for dosing and outflow
Pros
- Durable and easy to sanitize
- Often available secondhand
- Conical shape helps sediment removal
Cons
- Adding ports requires proper fittings and pressure rating checks
- Agitation usually needs a separate stirrer or recirculation loop
Peristaltic Pump and Tubing Kit
A peristaltic pump is the most common way to meter feed and effluent flow in a continuous setup. It suits anyone who needs a steady, adjustable dilution rate.
Key specs
- Adjustable flow rate for feed and outflow
- Food-grade silicone or similar tubing options
- Works with a range of inlet and outlet fittings
Pros
- Keeps the fluid path sealed from the pump head
- Easy to calibrate for a target dilution rate
- Widely used in lab and homebrew continuous rigs
Cons
- Tubing needs regular replacement
- Flow accuracy drops if the tubing wears unevenly
Buying Guide
Choosing a continuous stirred tank fermenter comes down to how you plan to use it. A lab researcher and a homebrewer testing a continuous kombucha line have very different needs, and it is easy to overbuy. The points below will help you narrow the field before you spend on equipment or parts.
Selection Criteria
- Working volume: Match the vessel to your batch of medium. Bench-scale work often uses a few liters, while homebrew builds commonly use a fermenter in the 10 to 30 liter range.
- Agitation method: Mechanical stirrers give the most even mixing. Recirculation loops are a cheaper alternative but mix less thoroughly.
- Control and sensing: Temperature is the easiest to control. pH and dissolved oxygen require probes and calibration routines.
- Material compatibility: Stainless steel and food-grade plastics suit most fermentation. Glass suits lab work but needs careful handling.
- Sterile access: Ports for feed, effluent, sampling and gas exchange should be sealable and easy to clean.
Important Features
Look for a vessel with at least four ports: one for feed, one for effluent, one for sampling and one for gas or air. Check that the lid or head seals well enough to hold your target temperature and avoid contamination. A conical bottom helps sediment settle away from the outflow, which keeps the effluent cleaner over long runs.
Specs to Check
- Maximum and working volume, stated separately
- Material grade and whether it is food-safe
- Pressure and temperature ratings for ports and fittings
- Stirrer type and maximum rotational speed
- Pump flow rate range and tubing compatibility
Choosing by Need
If you are a researcher or teacher, a bench-scale controller such as an Eppendorf BioFlo 120 or a Sartorius Biostat B-DCU gives you the data logging and control you need. If you are a homebrewer exploring continuous flow, a Brewer’s Edge Continuous Ferment Kit or a repurposed stainless conical is a better starting point. For a flea-market build, combine a used stainless vessel with a peristaltic pump and tubing kit, and add a simple temperature probe. For more general fermenter options, see Best Homebrew Fermenters: 5 Plastic, Glass and Steel Options.
Things to Watch Out For
- Flow rate and working volume determine your dilution rate. Calculate it before you start a run, not after.
- Tubing wears over time and changes flow accuracy, so schedule regular checks.
- Cleaning ports thoroughly matters more in continuous systems, because contamination can persist across the whole run.
- Any pressurized or heated modification should be checked against the manufacturer’s ratings. If you are unsure, consult a qualified professional before building.
FAQ
What is a continuous stirred tank fermenter?
It is a vessel where fresh medium is added and spent broth is removed at the same rate, while the contents are kept well mixed. This holds the culture in a near-constant state over time.
How is it different from a batch fermenter?
A batch fermenter is filled once, fermented and emptied. A continuous system keeps adding fresh medium and removing product, which can keep conditions more stable over a long run.
Do I need a controller to run one?
Not always. A simple setup can work with a peristaltic pump, a stirrer and a temperature probe. A controller helps when you need precise pH or dissolved oxygen control.
What size should I start with?
Many home experimenters start with a fermenter in the 10 to 30 liter range. Lab work often uses smaller working volumes. Choose based on how much product you need and how much time you can spend monitoring the run.
Is stainless steel better than glass?
Stainless steel is durable and easier to handle, while glass offers visibility and suits lab work. Both can be used safely when cleaned and sterilized correctly.
How often should I replace pump tubing?
Replace it when you see cracking, flattening or inconsistent flow. Many users check tubing at regular intervals during long runs. Follow the tubing manufacturer’s guidance.
Can I build a continuous setup at home?
Yes, many homebrewers do. Plan your flow rates, sanitation routine and pressure limits first, and consult a professional for any electrical or pressure-related work.
Conclusion
A continuous stirred tank fermenter gives you steady conditions that batch vessels cannot match, but the right choice depends on your goals. Research and teaching labs should look at bench-scale controllers like the Eppendorf BioFlo 120, Sartorius Biostat B-DCU or New Brunswick BioFlo 310. Homebrewers exploring continuous flow will find a Brewer’s Edge Continuous Ferment Kit or a repurposed stainless conical with a peristaltic pump a practical starting point. Whatever you choose, plan your flow rate, sanitation and pressure limits before you start, and check the manufacturer’s specifications for every part.
About Caleb Morgan
Caleb Morgan is part of our editorial team and reviews and edits our home brewing guides, checking product details against manufacturer specifications and owner feedback.
