Application note A050-FP02

Gas dosing for bacterial growth

Bacteria are single-celled micro-organisms with their size in the micron range. Already for ages, bacteria have been used in the preparation of fermented foods and drinks, such as yoghurt and wine.
Bacteria are the workhorses in the modern field of biotechnology, where they are employed to produce chemically, pharmaceutically or biologically active substances as antibodies or insulin. Bioreactors form their artificial habitat. In this controlled environment, that needs to be conditioned with respect to temperature, dosing of gases and liquids and pH value, these bacteria can grow. In a search for better mass flow equipment a manufacturer of bioreactors came in contact with Bronkhorst. A few years ago they developed a new, small type of bioreactor with a volume of 500 ml, and they needed matching gas dosing equipment. It was the start of a fruitful cooperation.

Production process for yoghurt in bioreactor

Application requirements

Accurately and reproducibly dosing of gases as oxygen or carbon dioxide to bioreactors is essential to control bacterial growth rate. Moreover, for easy scaling-up, a full range of dosing equipment should be available, and these should be mutually interchangeable.

Important topics

  • Reproducibility and reliability
  • Full range
  • Mutually interchangable, easy to scale up

Process solution

The small bioreactor system has the size of a personal computer housing, with a reactor vessel of 500 ml and all kinds of sensors. For this system they needed small mass flow controllers: for low flows, but also compact. To this end Bronkhorst supplied the IQ+FLOW mass flow controller for one channel, or a package called IQM3 for three channels, to dose gases such as oxygen, nitrogen, carbon monoxide or carbon dioxide into the reactor. With IQM3 three gases can be dosed simultaneously, each in the range between 10 and 1500 ml per minute.

For this small bioreactor application, a dosing accuracy of max. ±3% is required, and the IQ+FLOW meters/controllers deliver with an accuracy of ±2%. In addition to that: the bioreactor uses a standard recipe of gases for bacteria to grow, and the composition of the recipe should be the same - within specifications - as the previous one, so reproducibility is even more important.

Bronkhorst is able to serve the entire biotechnology production range: from lab scale (1 l/min) with the compact IQ+/IQM3 flow meters and controllers, via intermediate scale (10 l/min) with the EL-FLOW Select flow controllers, to full production scale (200 l/min). Upscaling to another device with larger flow is easy, as all these devices use the ModBus communication protocol, so they all speak the same language. The cooperation started with small devices but nowadays Bronkhorst flow devices are also incorporated in the bioreactors of intermediate and full production scale of the manufacturer

Flow scheme
Flow scheme


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