In biotechnological processes, sterilisation is the first step towards success. Heating the interior of the vessel to 121°C for 20 minutes ensures that there are no germs in the reactor that could contaminate the culture medium prior to inoculation.

But heating alone is not enough for a bioreactor. The reflux cooler must be deactivated, the boiler must be vented so that the temperature can be reached. During full sterilisation, stirring must be carried out so that the medium is heated evenly. The temperature must be maintained for the entire time so that the medium is not affected by overheating or the sterility is not affected by a drop in temperature. It must be ensured that supply air and exhaust air filters and all interfaces to dosing and transfer lines are also sterilized. When cooling down, a valve must be opened so that the fermentor does not fall into a vacuum.

During sterilisation, care must be taken not only to ensure that germs and spores are killed, but also that the medium is denatured as little as possible.

For the in situ sterilizable laboratory fermentors from Bioengineering (KLF, NLF, LP) there are different possibilities for sterilization:

Full sterilization (KLF, NLF, LP)

Media for microbial cultivation are usually not particularly sensitive to heat. Therefore, the fermentor is sterilized already filled with medium and heat-labile media components are subsequently added via a sterile filter if necessary.

The benchtop-fermentor KLF heats up electrically with a heating rod mounted in the bottom of the reactor.

With the steel fermentors NLF and LP, water in the double jacket is heated via a heat exchanger. The water is heated either electrically or with steam.

Empty sterilization (NLF, LP)

Cell culture media are often heat labile and are filtered sterile into the bioreactor. The vessel must therefore first be sterilized empty. Pure steam is passed through the vessel and the filters. In order to keep condensate formation to a minimum, the double jacket is also heated.

Various degrees of automation are available for sterilisation. In all variants, the sterilisation is documented in the batch report and it can be seen at any time whether the temperature has been maintained for the required time:

Manual (Full, Empty, KLF, NLF, LP)

Manual sterilisation is a process programmed as a recipe via the step chain, which runs largely automatically and in which a few manual operations are carried out. The program informs the operator at the right time about the steps to be performed. The temperature is maintained until the message is confirmed so that the reactor cannot evaporate or fall into a vacuum because a valve is not opened or closed. Operators must be present during sterilisation to carry out the operations.

Automatic (Full, NLF, LP)

Automatic full sterilisation is also programmed via the step chain, but the fermentor is also equipped with automated valves that open and close at the right time. The operators start the sterilization program, which runs autonomously until the cooling temperature is reached after successful sterilization.

Complete valve automation (full, empty, NLF, LP)

With full valve automation, not only the vessel sterilisation with pneumatic valves is automated, but also the sterilisation of permanently piped dosing lines and other functional groups of the fermenter system. The valve position sequences for cultivation, harvesting and, if necessary, the cleaning process can also be called up as operations.

Which variant is chosen depends on the model, the process requirements and the budget.