Ethanol

Sampling

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.

The TRACE C2 Control and BioPAT® Trace currently feature the following sampling options:

- 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.

Ethanol 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 (figure 1). This results in a compact measurement cell which can be preconfigured in tubesets for specific applications.

Analysis in the TRACE C2 Control and BioPAT® Trace is a combination of enzymatic conversion and electrochemical detection. An enzyme reactor with a platinum electrode serves as the biosensor.

Figure 1: Ethanol biosensor with enzyme reactor

The enzymatic determination of ethanol is performed according to the following reaktion:

Figure 2: Enzymatic conversion of ethanol by alcohol oxidase (AOD) with parallel anodic oxidation of hydrogen peroxide (H₂O₂)

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.

Application specific tubing sets
With the aid of pre-assembled tubing sets and associated transport and calibration solutions fully automatic sampling and measurement can be performed using TRACE C2 Control and BioPAT ® Trace.

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