Tips for Successful Bioprocessing #1: How to Prevent Contamination

What is one of the worst things that could go wrong in your laboratory? Ask anyone working to a deadline in a bioprocess laboratory and a likely answer would be contamination of their cultures. Contamination can be hard to trace back to a source and difficult to remove if it is present in your working environment. Fortunately, there are a few simple steps you can follow to minimise the chances of this happening to you.

Rédigé par

Tony Allman

12. Mar 2020

Avoid contamination of the starter culture

The most frequent cause is contamination of the starter culture. This can happen in many ways: improper handling, poor cleaning or insufficient autoclaving of the culture vessels and reactor or media components. A cleaning and disinfection procedure for laboratory equipment upstream of your bioreactor can help keep contamination from spreading via the seed culture.

If contamination is present, an organism that usually grows slowly as a static culture may suddenly find the perfect growth conditions in the bioreactor, quickly overwhelming the other organisms you are actually cultivating. This problem frequently arises in cell cultures, because cells grow very slowly and can be easily flooded by rapidly growing bacteria. One possible solution is to use antibiotics to kill off bacteria.

Reliable steam sterilization of the bioreactor

Maintaining the bioreactor target temperature long enough during the autoclaving process is important to ensure effective sterilization. The temperature sensor of the autoclave should be inserted into the immersion pipe on the culture vessel.

For a double-walled culture vessel, there must be enough water present in the jacket to ensure proper heat transfer during sterilization.

Careful assembly of the bioreactor

Assemble the bioreactor carefully and methodically check all seals to help to keep any unwanted visitors from reaching your culture. All sealing rings should be in perfect condition, i.e. there should not be any signs of kinks, flattening or burr formation. If in doubt, it’s better to replace the seal again, especially if it is not seated properly.

Check the O-rings on all components installed on the lid, regardless of whether these are intakes, sensors or plugs.

Special recommendations for cell cultures

Buy a sterile medium and 70% ethanol for disinfecting.
Wear gloves
Work at a sterile bench
Work with single-use equipment

Lastly, what do you do if contamination does occur?

An occasional lapse can be expected and does not mean your culture is spoiled. However, if you are high levels of contamination over time, this is a good indicator that something needs attention. Following the simple rules provided in this short overview should be enough to reduce the risk of contamination and help your cultures to thrive.