 In this module we will talk about again the form control system but as I have already told you in our previous module that we have to be very careful in case of this form control system and the selecting of the anti-foaming agent. So there are different factors which effect on the anti-foam requirement. Next one is the nature of the medium. Medium or a media rich in the proteins will tend to foam more readily than the simple media. If there is a media having carbohydrates having a less proteins then there is a less chance of foam formation. So the nature of the medium is very critical factor in producing the foam. So the product so when their fermentation process will on, numerous various kind of the product is are formed. So as concerned the nature of the product then that can effect on the foam production. As an example that secreted proteins, nucleic acids when they release either the cell death either by the hydrolysis of some detergent like properties. So that is why that help that facilitate the foam production. In third case, aeration and the stirring speed of the impellers also effect on the foam formation. So the fourth problem is that the use of the mechanical foam controllers. The foam control device such as mechanical and ultrasonic foam breakers help to reduce the anti-foam requirement. So that can also be when there is a highly aerobic fermenters sometimes we can change the fermenter type. Sometimes the straight fermenters replaced by the airlift fermenters or any other type of the fermenters. So there are different strategies that can be utilized that can be used for decreasing the risk of foam formation. So as concerned the fifth effect on the head space volume. Sometimes when we utilize the maximum capacity of the fermenter that is mostly I have told you already that 75% of the total capacity of the fermenter can be utilized. The 25% space is required for the head space that is basically for the oxygen transfer and the gaseous transfer and the foam production space. So if there is a large head space then there is a greater tendency for the foam to collapse under its own weight because when there is an increase in the then sometimes what happen then there will be automatically self-killing of the foam bubbles. So if we keep the 50% head space volume then that is basically this kind of the situation we can see but in case of 75% we have the problem. So as concerned the fifth but as concerned the sixth the condenser temperature. So in Liberty scale reactor the cold condenser temperature can help to control the foam. So the density of the foam increase when it moves from the warm head space volume to the cold condenser region. So this can cause the foam to collapse. So by this strategy by using the condenser temperature we can have the less risk of foam problem. So on other hand if there is a chemical antifombers then we can use some mechanical foam cutters as I have already told you in a one point. In this slide you can see that mechanical foam cutters but there is one problem by using the mechanical cutters because in a small scale there are different gadgets and the probes has to be fitted with the fermentor vessels but in such case that only be possible in a large scale or industrial scale fermentor when all such kind of the probes are attached to the surface or the periphery of the fermentors. So that can only be so there are different shapes and you can see here that this one this is having a sharp edge blades. So different shapes so in this slide you can say another type of foam cutter and then here you can see another foam cutter which is mostly utilized in a industrial scale fermentors. So there are different and genetical shapes which can be utilized but there is only one problem that there should be a free space where we are using otherwise there is if there is any probes insulting from the top to the fermentation medium then we cannot use these mechanical foam cutters attached to the surface of the working volume.