TAKING CARE OF THE FERMENTER ELECTRODES

Electrodes, probes and sensors are very important components that help us in monitoring the fermentation process. The electrodes are the eyes that help us to see what is going on inside the fermentor at anytime! They are especially important to keep the fermentation occurring under the range op optimal conditions and to warn us if the fermentation process have deviated beyond the set optimal values.

The best part about these electrodes they are sensitive and we can read their values digitally much better than what our eyes and experience can detect.

That is why the electrodes used in the fermentation must always be kept under optimum conditions, functioning properly and properly calibrated. Failing to take care of the electrodes will affect the accuracy thus affecting our monitoring of the fermentation process.

The electrodes and probes in the fermentor are mainly on line probes.

HARSH CONDITIONS FOR PROBES IN FERMENTOR
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The electrodes found in the fermentor are similar to those found in the laboratory, except they are more rugged and can withstand the conditions of the fermentation such as:
1 High temperature
2 High pressure
3 High concentration of microorganisms
4 High organic content of broth
5 Long exposures in terms of time

This does not mean that they do not face the various problems mentioned above, except they are better in facing them than normal laboratory electrodes! However, because of the various harsh and extreme conditions, the life span of the electrodes is not long enough. Only proper maintenance and servicing will prolong the life and accuracy of the electrodes.

It is sad in the author's personal experience and observations that a high number of electrodes in fermentors used are not taken care of or properly calibrated by users. They have always assumed that the electrodes have indefinite lifespan and functionality and accuracy maintained. Of course, poorly or spoilt electrodes still do give readings if used BUT wrong or inaccurate readings!

We can classify errors to electrodes or probes being from one of the following causes:

1 Biofouling of electrodes
2 Structural and mechanical defects
3 Electrical defects
4 Chemical defects


BIOFOULING OF ELECTRODES
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The fermentor is a vessel that is purposely designed and built to cultivate high concentration of microorganisms. In a normal fermentation run, the fermentor will be supporting the growth of the microorganisms over a period of maybe 5 days. It is a long period of microbial incubation!

Throughout the fermentation process, the fermentor's electrodes will be subjected or continuously immersed in the fermentation broth, and exposed to the microorganisms, and components of the broth. Such situations will easily and unavoidably lead to rapid biofouling of the electrodes and sensors of the fermentors.

It is most important that the situation of biofouling of the electrodes be minimized by removing and cleaning the electrodes as soon as possible once fermentation is terminated. Do not leave the fermentors uncleaned or still lingering in the fermenter or fermentation broth.

DISSOLVED OXYGEN PROBE
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Unscrew the thread and gently pull the DO probe out.
Immediately rinsed off and then wiped dry gently.
Always remembering to avoid touching the membrane at the tip.

Removal of accumulation of biomaterial on the probe by wiping the probe down more vigorously In no case should the tip of DO probe be touched.

After cleaning the D.O. probe the tip can be visually inspected for damage.
Store the DO probe in a clean area in such a way as to protect the sensitive tip.

Ph PROBE
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Once the pH probe has been removed, it should be immediately washed off with warm water.

Remove biomaterial accumulation on the probe by using a sponge (or an equivalent that will not scratch glass) and gentle pressure to clean the surface.

The very tip of the probe should be handled with extreme care. A Kimwipe should be used to gently dry it off after washing.

The probe should be stored with the tip immersed in either electrolyte or pH 7 buffer.
Ensure the buffer is free from precipitations and biofoulings.