How to Avoid Oxygen Limitations in Shake Flask Culture

Flask with integrated O2 sensor & SFR vario
DO in two shake flask cultures of E. coli

Avoid O2 Limitations

Several measures can be taken to avoid oxygen limitations inside Erlenmeyer flask cultures:

  • Reduce the working volume
  • Increase the rpm
  • Change the rotation diameter
  • Switch to another shake flask design

But how do you determine the time point when oxygen becomes limiting and which measure is most suitable for your application?

The Approach

The figure on the left shows online oxygen measurements with optical sensors in two parallel E. coli DH5alpha cultures on LB complex medium. By constant monitoring and timely adjustment of the rpm oxygen limitations could be avoided. The online measurements enable to react in time and control the oxygen supply. At the same time one can immediately verify that the taken measure had the desired effect.

The Method

A non-toxic fluorescent layer, the sensor spot, is integrated in the shake flask. This layer is excited with light of a certain wavelength and emits fluorescence in response. The fluorescence signal changes with the amount of oxygen molecules present. This sensor can detect oxygen with a precision better than 0.1 % O2. An electro-optical device (Shake Flask Reader) reads out the sensor signal non-invasively through the flask bottom. The data is transferred wirelessly to a PC and oxygen levels inside the culture can be displayed in real-time with the reader software. This way online monitoring can be performed conveniently without disturbing the culture inside the shaking incubator.

The Shake Flask Reader constantly measures dissolved oxygen. You can see the effect of your measures immediately!

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Shake Flask Reader Features

  • Online monitoring of O2, OUR, biomass & pH or CO2 in shake flasks
  • Also stores temperature & rpm
  • Wireless data transfer to a PC
  • Parallel monitoring in up to 4 Erlenmeyer flasks
  • Fits in any shaking incubator
  • Works with any shake flask type & size


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