Biotechnology

Struktol antifoam agents for fermentative processes

General
The generation of foam during fermentation processes is caused by the existence of foam-active substances in the fermentation broth, escaping gas/air and turbulences within the fermenter. In most cases the substrates used are high in carbohydrates, which are partly converted into sugar substrates by enzymes. Sugars, starches and proteins act as the foam promoting substances themselves and they may be assisted by other substances or ingredients that partly consist of trace elements for the microorganisms. Furthermore, amino acids and proteins, which are generated by the microorganisms during the fermentation, can cause considerable foam activity.

Anaerobic/aerobic fermentation processes

The nature of the released gases depends on the fermentation method. Basically we have to distinguish between anaerobic and aerobic fermentation processes. The production of alcohol is a typical example of anaerobic fermentation. During this process substrates containing different sugars and starches are transformed by using yeast into alcohol and carbon dioxide. Depending on the substrates used more or less foam is formed by the escaping carbon dioxide. However, aerobic fermentation processes are much more important for the use of antifoam agents. In this case we have to distinguish between processes for the propagation of microorganisms (as for example the production of baker's yeast) and the production of different "biotechnology products" (as for example antibiotics and enzymes) by using special microbes. During aerobic processes air is blown into the fermentation vessel in order to supply the microorganisms with oxygen. The excess air is released and generates foam. Usually aerobic processes are considerably more foam intensive, because the quantity of air released is significantly higher than the quantity of carbon dioxide released during anaerobic processes.

Dosage of antifoam products

Without the use of antifoam agents fermentation vessels would overflow, which would lead to considerable losses of product as well as to soiling of the plant and other disadvantages. In most cases the antifoam is added into the upper area of the fermentation vessel. The addition is controlled by a foam probe. Schill+Seilacher "Struktol" GmbH developed a dosage system of this type, used succesfully in a large number of plants for several years. The dosing procedure depends on the fermentation progress. Usually the required quantity of antifoam is automatically and continuosly added to the system during the whole fermentation process and the dosage can be adjusted as required. Other foam controlling procedures in fermentation processes are, to fill fermentation vessel with substrates and the antifoam agents in order to prevent frothover during fermentation start. 

Antifoam selection
The most important criteria to choose the best antifoam are effectiveness and not having any negative influence on the fermentation process concerning final product quality and yield. This results in an optimum yield and improved quality of the final products.

Product purification
After the fermentation process is completed, the final products have to be separated from the fermentation broth. The procedures for this isolation can be completely different and depend on whether the final products are either liquid or solid. Schill+Seilacher "Struktol" GmbH has developed a special product range for the fermentation industry. An accurate antifoam selection provides best fermentation results.

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