Method of PMI foam chemical defoaming fermentation: A d […]
Method of PMI foam chemical defoaming fermentation:
A defoaming method that uses a chemical defoamer to eliminate foam is also the most widely used defoaming method. Depending on the factors that form the foam, a defoamer with a different mechanism of action can be selected. Defoamers are all surfactants with low surface tension. When there is an electric double layer formed by a polar surface active material on the surface of the foam, the addition of another surface active material of the opposite polarity can neutralize the electrical properties, destroy the stability of the foam and break the foam; The substance competes with the foaming agent for space on the surface of the foam, reduces the mechanical strength of the foam liquid film, and then promotes the bursting of the foam. When the liquid film of the foam has a large viscosity, certain substances with small molecular cohesion can be added to reduce the surface viscosity of the liquid film, cause the liquid of the liquid film to leak, and cause the foam to break, thereby achieving the purpose of eliminating the foam.
According to the defoaming principle and the properties and requirements of the fermentation broth, the ideal defoamer must have the characteristics: the defoamer must have a low surface tension, the defoaming effect is rapid, and the efficiency is high; the PMI foam has sufficient at the gas-liquid interface A large spreading coefficient means that the defoamer must have a certain degree of hydrophilicity; the solubility of the defoamer in water is small to maintain its long-lasting defoaming or antifoaming properties; the transfer of oxygen during the fermentation process and the extraction process The separation and extraction of the products have no effect.
High temperature resistance, does not interfere with the use of dissolved oxygen, pH and other measuring instruments; convenient sources of defoamer, cheap price; non-toxic to microorganisms, humans and animals. The defoamers commonly used in the PMI foam fermentation industry are divided into four categories: natural oils, polyethers, higher alcohols, and silicone resins, of which the first two are used most. Commonly used natural oil defoamers are corn oil, soybean oil, rice bran oil, cottonseed oil, and lard. In addition to being defoamers, these materials can also be used as carbon sources, but their defoaming capacity is not strong and the required amount Big.