BT603 Final Term Merged PPT Handouts by Aarish Ali

The following compounds which meet most of ideal antifoam requirements (as discussed in previous module) have been found to be most suitable in different fermentation processes: 1. Alcohols; stearyl and octyl decanol. 2. Esters. 3. Fatty acids and derivatives, particularly glycerides, which include cottonseed oil, linseed oil, say-bean oil, olive oil, castor oil, sunflower oil, rapeseed oil and cod liver oil. 4. Silicones. 5. Sulphonates. 6. Miscellaneous; Alkaterge C, oxazaline, poly-propylene glycol. Unfortunately, the concentrations of many antifoams which are necessary to control fermentations will reduce the oxygen-transfer rate by as much as 50%; therefore antifoam additions must be kept to an absolute minimum. There are also other antifoams which will increase the oxygen-transfer rate. If the oxygen-transfer rate is severely affected by antifoam addition then mechanical foam breakers may have to be considered as a possible alternative. Various studies concluded that foam control in industry is still an empirical art. The best method for a particular process in one factory is not necessarily the best for the same process on another site. The design and operating parameters of a fermenter may affect the properties and quantity of foam formed. The types of antifoams mentioned in previous slides are generally added when foaming occurs during the fermentation. Because many antifoams are of low solubility they need a carrier such as lard oil, liquid paraffin or castor oil, which may be metabolized and affect the fermentation process.

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