 In this module, which is the continuation of the microbial growth kinetics in previous two modules of this topic, we can we discussed different phases of the growth and different methods to estimate the growth. But in this module, we will gradually talk about the batch culture kinetics. In the previous modules, when we talk about the type of fermentation, we divide the fermentation into three different types on the base of the process batch fermentation, fat batch fermentation and continuous fermentation. So, today and in the following different modules, we will talk about the kinetics parameters in batch culture, fat batch and then in a continuous culture. So, as concerned the batch culture, as we have already discussed that batch culture is a batch of a culture medium in a fermenter is inoculated with the microorganism which we called as starter culture or inoculum. And then the fermentation proceed for a certain duration, which we called as incubation time at specific temperature with specific pH at a specific agitation and other parameters. And then at the end we harvest, there is no addition of the substrate during that. So, as we refer back, the batch culture is a closed system, which contain an initial limited amount of the nutrients. We put all the things at one time in technical terms as concerned the substrate or the nutrients we call them the S that amount of the substrate we add at zero time or we can say that before inoculation or before sterilization. So, that will remain the same and there is no more addition of that, but if we say that remain same that is not correct term because during the growth that S will be depleted because the growth will occur and at the result of the growth you know that growth will only occur when they utilize some substrates. So, when growth occurs the organism use some substrate and then they use for their metabolic pathways and then after the certain time we harvest that culture. So, in this whole process there are different changes occur in we can say that when growth will happen you can say here as we have already discussed in previous module about different phases of the growth especially in batch culture. So, there is a lag phase again in which we can say that it is a acclimatization stage in which only the cell there is no increase in the number, but they utilize some substrate for their maintenance and then there is a exponential phase. In this phase we can say there is a maximum utilization of the substrate and then there is a stationary phase in which also the organism has their metabolic pathways active, but in this rate the death become equal to the birth, but as concerned the decline is we cannot say that the metabolic pathways totally become inactive, but in this case some cells remain active, but the death rate increase then the birth rate. Now, talking of in detail about the growth kinetics in batch culture we should know that different symbols we use for the biomass for substrate for product. In this slide you can easily see that different so the x is used for biomass, s will be used for substrate and p for used for the product. So, as concerned the kinetics microbial growth kinetics in batch culture we will talk about the relationship between x mean biomass to time that how the change occur in biomass with respect to time and then how the substrate depleted with respect to time and what will be the rate of product formation with respect to time. So, in case of the product sometimes we say that in batch culture x biomass itself considered as the product might be you know that in very in our the introduction of the fermentation when we talk about the different types of the product we talk about the four different ranges of the fermentation. The first range of the fermentation product was the biomass production in which the biomass x is itself called as the product. So, sometimes x itself is a product sometimes some products are associated with the biomass as the biomass increase product will also increase, but sometimes our product will not be associated with the cell biomass. So, in as we concerned that if we want to produce the amount of DNA so as the biomass will increase the DNA will also increase. So, we should clarify here that when we talk about the kinetics we should know either our product is biomass associated or not associated with the biomass.