 In this module of the sterilization, we will discuss the source of contamination. As concerned the fermentation process as we have seen in our previous module that fermentation process is actually the mass culturing that require a suitable medium. So, during the fermentation process when we see the whole organization of the fermentation process that is first one is the source of contamination is the leakage or the fermentation vessel. Second source of the contamination is actually the medium. When we formulate the medium, when we make the medium and then feed into the fermentation vessel then the contamination can happen. And third is when we sparge the medium with the air then the contamination may come through the air. So, there are the number of factors that can be the source of contamination. If we first of all if we avoid those and we can have a control check over all those factors from where the contamination can occur then we can run our fermentation only with our production organism which we called as our fermentation organism. So, how we can avoid the contamination? As concerned the avoidance of the contamination so, the first is we use pure inoculum in the start of the fermentation. If there will be a contamination in our inoculum then there is no more way by which we can avoid our contamination. Our inoculum should be 100 percent pure and without any sort of contamination. And second is the medium which we are using and we are employed because there are two techniques. Either we sterilize our the medium inside the fermentor either we first having the sterilization of the medium apart from the fermentation vessel and then we add into the vessel. So, if we employed the medium then our medium should be sterilized. So, the sterilized medium should be employed. In this case when we are adding the medium sterilized then our fermentor vessel should be clean and sterilized. So, in fourth case the sterilization of all the material to be added into the fermentation that should be sterilized. What are those materials? That can be antiphone that can be any other alkali or the acid medium or if we are running with the fat batch then those ingredient and those part of the medium which we are adding through the fermentation process that should be properly sterilized. And then the fifth one the maintenance the maintaining the aseptic conditions during the fermentation process then we can avoid the contamination in our fermentation process. So, as concern the extent to which the procedures are to be adopted for the avoidance of the contamination that will help to check out the probability of the contamination. If we have a very control mechanism of the avoidance of the contamination then there will be a less probability of the contamination. Why we are talking about the probability of contamination? Because when we say that the number of unwanted microorganism present into any object then our whole sterilization process will be. So, we can say on the base of the fermentations in two category either that was protected or unprotected. So, in first case in most of the fermentation they are termed as the protected. If the media may be utilize only a limited range of the microorganism which we called as the process organism and in the result of the development of a selective growth conditions for our desired organisms in term of pH, in term of nutrients, in term of other conditions. So, in case of just an example if we are the breathing of the beer falls into the category if we are using the whole presence tend to inhibit the growth of many microorganisms and the growth of breathing yeast tend to decrease the pH of the medium. So, this is the case when such type when there is a microorganism then how that effect on the pH of the medium. So, thus the breathing what are boiled, but not necessarily sterilized and the fermentations are thoroughly cleaned with disinfectants, but are not properly sterilized. So, also there are some precautions used when the development of the inoculum. So, in case of the inoculum development then that should be having a very pure and having no contamination. So, the majority of the fermentations are the protected, but we can say that then there are the majority of the fermentation which we cannot say that they are protected. So, if there is a contamination that can lead to different consequences as we have discussed in our previous modules. So, in case of the protected then we can assure our fermentation process in a positive way, but if our fermentation process is not protected then so many consequence which we have discussed that can happen.