 In this, in this module we will talk about the method of batch sterilization for medium sterilization. So, as concerned the methods in batch sterilization. So, the batch sterilization of the medium for the fermentation may be achieved either in a fermentation vessel or in a separate mass cooker. So, there are two strategies. Richard in 1966 considered that the relative merits of in-stew sterilization and the use of special vessel. So, the major advantages of a separate medium sterilization vessel is as follows because there are two approaches. Just in a batch sterilization we sterilize the whole system of fermentation fermenter inner vessel as well as the medium which we called as in-stew on the same place. On other hand if we are dealing with the sterilization just we will sterilize the medium apart from the fermentation vessel. Then there is a second approach. So, in this case when we sterilize the medium separately from the fermentation vessel then the one cooker may be used to serve several fermenters. And the medium may be sterilized as the fermenter are being cleaned and prepared for the next fermentation thus saving the time. So, if the one fermentation is going on during that time we can sterilize the next batch medium. So, this is the one advantage. As concerned the second the medium may be sterilized in a cooker in a more concentrated form than would be used in the fermentation. Because we can sterilize the medium in a concentrated form in a separate vessel and then we can add into the fermentation vessel and then we add the more. So, we can sterilize in a concentrated form this would allow the construction of a smaller cooker. So, in some fermentation the medium is at its most viscous during the sterilization and the power requirement for agitation is not elevated by the aeration as it would be during the fermenter properly. Thus if the requirement for the agitation during in-stitute sterilization were removed the fermenter could be equipped with less power motor. So, obviously the sterilization cattle would have to equipped with the powerful motor, but this would provide the sterile medium for several fermenters. So, as concerned the fourth the fermenter would be speared the corrosion which may occur with medium at high temperature. As concerned the major disadvantages of a separate medium sterilization vessel. So, first one is the cost of constructing the batch medium sterilizer that is much the same as the fermenter. Because if we design a separate vessel for the sterilization we need some specific material almost the equivalent and equal cost to the fermenter vessel. So, if the cooker serves a large number of fermenters the complex pipe work. So, if we are using the external vessel for a number of fermenters then we need a complex pipe work just to transport that sterilize medium to the particular fermenter. So, that is necessary and that pipe system and the transport system also need and the decontamination and with the inherent danger of the contamination. So, there is a risk. So, if we sterilize and then there is a transportation through that complex pipe system then there is a chance of contamination through those pipes and lines. So, as concerned the mechanical failure as concerned the third disadvantage the mechanical failure in the cooker supplying the medium to the several fermenters would render all the fermenters temporarily redundant. So, the provision of contingency equipment may be prohibitively costly. So, in this case the major disadvantage is the cost and the chance of contamination the risk of contamination. So, in all case the overall pressure to decrease the downtime between the fermentation has tended to over weigh the perceived disadvantages of using a separate sterilization vessel. So, thus the sterilization in dedicated vessel is the method of choice for batch sterilization.