Application Note

Gas flow control for benchtop bioreactors

with flexible gas flow controller

Traditionally dozens of flow instruments are needed to satisfy the demands of advanced benchtop bioreactors. But with the FLEXI-FLOW Compact our customer experienced that this number can be greatly reduced, making it possible for bioreactor manufacturers to be more efficient with their stock, lead times and instrument design.

The challenge for benchtop bioreactor applications

Most bioreactors — whether they are used for fermented food and drinks or the development of vaccines and medicines — need to be supplied with gases for growing bacteria, yeast or cells for the desired biological synthesis to take place. These gases are usually added continuously over a period of a few days to several weeks using flow controllers. Bioreactor manufacturers would like to build reactors that are as generic as possible, to provide a system that can be used by a variety of users. Ideally, one bioreactor setup handles a wide range of gasses and flow rates.

Flow control in benchtop bioreactor

Flow requirements for benchtop bioreactors

For a reliable biological growth process, accuraterepeatable, and stable gas flows are essential. Especially in the R&D environment, a wide range of gas flow rates is necessary to investigate the best growth conditions. For benchtop bioreactors compact gas flow instruments are desired. For manufacturers that build bioreactors on specification for customers, it is desirable to reduce the number of variations of flow instruments, to counteract obstacles like delivery time. Being able to collect pressure data is also desired to inform the bioreactor user about the current process conditions.

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Important topics

  • Large dynamic flow range
  • Easy switching of gas type
  • High accuracy, repeatability and long-term stability
  • Pressure information
  • Compact

Process solution

Bronkhorst offers gas flow control for bioreactor manufacturers and has a gas flow controller available that is ideal for use in benchtop bioreactors. The FLEXI-FLOW Compact mass flow controller is equipped with a unique flow sensor that measures and controls flow over a wide dynamic range (a high turndown ratio of 1:1000) in combination with excellent accuracy and compatibility with 20 different gas types.
This allows the bioreactor manufacturer to easily change the flow range and switch to other gas types without the need to switch to different instruments. The FLEXI-FLOW Compact is also equipped with temperature and pressure sensors, providing more data to the user. Thus, you can benefit from model reduction, allowing you to keep a local stock and therefore be independent of lead times.

Flow scheme

Easy switching of gas types

As air, oxygen, nitrogen and carbon dioxide are the most common gases in this field, the FLEXI-FLOW Compact has the data on these gases available in an on-board database, so there is no need for additional calibration. Using the on-board FLUIDAT firmware, the instrument instantly calculates the physical properties of gases and adjusts accordingly, allowing you to reduce the number of instrument types needed.

Where a typical range up to 20 ln/min with four gases has been traditionally covered by 36 MFC models, this can be reduced to 12 models, and with four gases on board even to 3 mass flow controller models. The bioreactor manufacturer and the end-user can decide which of these gases to use by setting a parameter in the software.

FLEXI-FLOW flow controller enabling model reduction
Reduction of gas flow controllers possible

Customer experience:

“We only need to have a few models in stock to satisfy all our design options. And we were able to reduce the number of instruments in our process, which in turn made it possible to have a benchtop bioreactor with a smaller footprint than before.”

Long-term stability

Due to a capillary chip sensor technology combined with friction-free valve technology and electronics, the FLEXI-FLOW Compact instrument has an excellent accuracy, repeatability and long-term stability. The capillary chip sensor that measures the gas flow remains very stable over the years and does not need calibration. Since the small sensor is less prone to temperature gradients, the short-term stability is very good as well.

Pressure information

Pressure information is desired to inform or alarm the bioreactor user. This accounts for gas supply pressure at the inlet and bioreactor process pressure at the outlet. Limitation of the process pressure is necessary for bioreactors to avoid breakage of the reactor. The FLEXI-FLOW Compact gas flow controller contains pressure measurement and control at the inlet and outlet of the instrument, and as such, this smart instrument is suitable for predictive maintenance of the bioreactor system.


The small size of the FLEXI-FLOW instrument will make it a device of choice for compact benchtop bioreactors.

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