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Formation of fermentation foam and selection of defoamer
Published Time:
2020-06-23 14:51
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Reasons for foam fermentation:
1. In the fermentation process, the aeration is large, and the strong stirring power makes foam increase;
2. Fermented microorganisms are too active, and the culture medium is rich in nutrients and viscosity, resulting in more foam;
3. The sterilization quality of the culture medium is poor, sugar and nitrogen are destroyed, which inhibits the growth of microorganisms, makes the seed hyphae self dissolve, and produces a lot of foam
4. The quality of the strain is good, the growth rate is fast, and the soluble nitrogen source is used quickly, which makes the concentration of protein in the fermentation broth rise, and the concentration increases to produce foam;
5. The bacterial cells in the fermentation tank are cracked, resulting in the release of a large amount of protein. The liquid continuously expands and comes into contact with air, causing a large number of bubbles to appear.
6. Affected by the environment, the temperature rises rapidly during fermentation, coupled with constant stirring during the fermentation process, resulting in an increase in bubbles.
The selection of defoamers should meet the following characteristics:
1. Insoluble or insoluble in foaming solution
In order to break the foam, the defoamer should be concentrated on the foam film. For defoamers, they should be concentrated and concentrated in an instant, while for foam suppressants, they should be kept in this state regularly. So defoamers are in a supersaturated state in foaming liquids, and only insoluble or poorly soluble ones are prone to reaching supersaturation. Insoluble or difficult to dissolve, it is easy to aggregate at the gas-liquid interface, easy to concentrate on the bubble membrane, and can function at lower concentrations. The defoamer used in water systems, the active ingredient molecules, must be strongly hydrophobic and weakly hydrophilic, with an HLB value in the range of 1.5-3 for the best effect.
2. The surface tension is lower than that of the foaming liquid.
Only when the intermolecular forces of defoamers are small and the surface tension is lower than that of foaming liquids, can defoamer particles penetrate and expand on the foam film. It is worth noting that the surface tension of the foaming solution is not the surface tension of the solution, but the surface tension of the foaming solution.
3. Has a certain degree of affinity with foaming liquid.
Since the defoaming process is actually a competition between the foam collapse speed and the foam generation speed, the defoamer must be able to disperse rapidly in the foaming liquid so that it can quickly play a role in a wider range of foaming liquid. To make the defoamer diffuse quickly, the active ingredient of the defoamer must have a certain degree of affinity with the foaming solution. The active ingredients of defoamers are too close to foaming liquids and will dissolve; Too sparse and difficult to disperse. Only when the closeness is appropriate can the effectiveness be good.
4. No chemical reaction occurs with foaming liquid.
Defoamers react with foaming liquids, causing them to lose their effectiveness and potentially produce harmful substances that can affect microbial growth.
5. Low volatility and long duration of action.
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