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Cover story
Working in the bioreactor
Bioreactors are like small factories. However, it is not workers who are toiling away at heavy machines inside them, but tiny bacteria that metabolise and produce an amazing variety of substances. In order to achieve maximum performance, the tiny creatures have to be particularly comfortable. They need special living conditions for this.
Nutrients
Many bacteria like sugar; all of them need trace elements and vitamins. The nutrients must be supplied regularly.Foaming
Foam is created by stirring, for example. It can clog the exhaust air filters and therefore needs to be destroyed either chemically or mechanically.Temperature
Every bacterium has its own comfort temperature. If it is too warm, this damages the bacteria; if it is too cold, the metabolism and thus productivity drops.Mixing
To ensure that bacteria everywhere in the reactor receive sufficient nutrients and oxygen, the liquid is constantly being mixed – mostly by stirring, sometimes by blowing in gas.Harvesting
In order to obtain the desired substances, liquid is tapped via a valve, from which the substances are filtered.Reactor material
This is mostly glass or steel – the material must be stable and easy to clean. Between productions, the reactor is sterilised so that only the desired bacteria will grow there.Oxygen
Many bacteria need oxygen to breathe. The oxygen content is regulated via a fresh air supply.pH value
Bacteria also need an individual feel-good pH value. For this, the pH value is constantly being measured and, if necessary, readjusted.Learn more about the living conditions in the bioreactor by clicking on the individual components.
Turning small into large
New processes in bioreactors start very small: research reactors often only have the volume of a beer mug. However, the transition to an industrial plant that is sometimes hundreds of thousands of times larger does not always go smoothly. In a large kettle, for example, mixing is more difficult, and, with it, so is the constant supply of nutrients and temperature at every single point. But changing conditions of the environment can lead to undesired reactions of the bacteria. Researchers are thus already trying to sort out the bacteria that react too sensitively to fluctuations on the laboratory scale.
Read also:
Jülich blog entry: Water glass or swimming pool
<link en single-room-for-bacteria _blank hyperlink2>effzett 2-2019: Single room for bacteriaReactor sizes
in litres
1–10
In the laboratory
|
10–300
Test plant for the industry
|
500–1.500.000
Industrial production
|
< 20.000.000
Waste water bioreactor
For comparison:
≈ 2.500.000
Olympic swimming pool
Colourful workforce
In bioreactors, research and industry breed different bacteria for different purposes. Jülich researchers are relying on these workers, among other things.
Corynebacterium glutamicum
is an important workhorse of research and the biotechnology industry. With its help, several million tonnes of amino acids areproduced every year for infusion solutions and feed additives. The bacterium likes glucose and temperatures around 30 degrees Celsius as well as a neutral pH value of 7. What’s more: it can withstand several minutes without oxygen without its performance diminishing. Researchers at Jülich use it to produce xylonate, a raw material of interest to industry, from plant waste. For this purpose, they have given it the special ability of another bacterium: of Caulobacter crescentus (see here).
Pseudomonas putida
This is a soil bacterium that can even live on caffeine. Its ability to crack petroleum-based molecules, and thus bacterially recycle even difficult substances such as polyurethane, are in great demand by biotechnologists. Cold foam mattresses or sports shoes are made from this material, among other things. At Jülich, the bacterium is supposed to help break down PET, for example.
Escherichia coli
In humans, for example, this intestinal bacterium is responsible for the production of vitamin K. Biotechnologists use the organism to produce fine chemicals, enzymes or drugs, such as insulin. Jülich researchers use it to produce enzymes that can, for example, be used as biocatalysts in the production of active substances.Illustrations: Jens Neubert