When analyzing substrates in cultivation media, it is necessary for a sample to be removed from the bioreactor (fermenter) under sterile conditions. The reproducibility and relevance of the sample taken must remain intact during this step.
- Filtration with a filtration probe
- Gas diffusion with a dialysis probe
Both procedures enable safe and sterile removal from the bioreactor.
The simplest method is to directly measure a filtered sample of medium. However, because reactor medium is used, the range of applications is limited to processes for which there's a sufficient reactor volume or which allow continuous-feed.
Gas diffusion sampling is an option when processes are involved for which reactor volume does not allow enough sample material. This method only removes low molecular substances from the reactor medium, without reducing the volume of fluid.
For the measurement ethanol is separated from the sample by a gas diffusion membrane in the probe, or in the fluidic tubing set and then supplied to the biosensor.
TRACE is using a combination of immobilized enzymes and electrochemical transducers for the production of biosensors. This combination is extremely robust and versatile. The biosensor is mounted in a flow-through cell (see figure). This results in a compact measurement cell which can be preconfigured in tubesets for specific applications.
The figure shows an ethanol biosensor with enzyme reactor
The enzymatic determination of ethanol is performed according to the following reaction:
Since the enzyme alcohol oxidase recognizes both methanol and ethanol, there is a cross-sensitivity between the two substances. A separate determination is not possible.
Depending on the application, the service life of the sensor system ensures 30 days or 5,000 measurements. The deviation from the average measurement is less than 5% for a measurement of 2 g/L ethanol.
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