CHARACTERISTICS OF FERMENTATION ELECTRODES

Most fermentors at least come equipped with the following electrodes or sensors.
1 Ph probe
2 Dissolved oxygen probe
3 Thermo probe
4 Foam probe
5 Level probe

The ph and dissolved oxygen probes are also commonly used in various laboratories or field monitorings and process controls. The other three probes are more based on the principle of conductance and impedence

Despite the variety of probes such as ion specific electrodes and enzyme sensors present on the market, only ph and DO probes are suitable to be used directly in the fermentor assembly. The failure to incorporate the other electrodes directly into the fermentor is because of the inability of the other probes to withstand the harsh conditions of the fermentor.

The requirements of the probes to be incorporated as probes in fermentors include:

1 Able to withstand high temperature especially during the sterilization process
2 Able to withstand high pressure in the course of the fermentation exercise
3 Maintain aseptic integrity of the fermentor in the incorporation of the electrodes

Only ph and DO probes so far can comply with the above factors and are used routine;y as important online monitoring activities,

The DO and ph probes used in the fermentor are in a way similar to the same probes used routinely in the laboratory. However, they are structurally modified to adapt to the harsh fermentation conditions. They are built of more durable bodies and have specific housings which allow them to be inserted safely in large fermentors.

YOU CANNOT USE NORMAL PH AND DO PROBES USED IN THE LABORATORY FOR FERMENTORS!

ELECTRODE HOUSINGS
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Housings are very important components in electrode sensor systems of the fermentor. Housings allow:
1 the electrodes to be inserted at the correct location in the fermentor.
2 It protects the electrodes.
3It provide defense against contamination of the electrodes.
4It maintains the aseptic integrity of the fermentor system once electrodes are inserted.
5It allows built up of pressure to counter the higher in built pressure of the fermentor


The type of housings for the electrodes depend upon process requirements and the type of electrode/sensor used. Conventional electrolyte filled probes on large fermentors are fitted inside pressurized housings to keep a positive pressure over the fermentors to prevent contaminations of the electrolyte and reduces the risk of plug blockage. Sealed gel electrode provide a suitable alternative




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