 This module that is the continuation of the previous module in which we are talking about batch culture kinetics. So as I have already told you that in kinetics we will see the relationship of different parameters that gradually change during the fermentation period. So the major change occur as the definition of the fermentation involve the mass culturing. So when there is the addition of the inoculum then there is a gradual change in the number of the cells or we can say that gradually increase in the biomass of the cell. So in short we can see when with the respect to the time as the time will pass growth will happen. When there will be a growth then there is the increase in the biomass. So we can say that there is first there will be a lag phase and then there will be a log phase. So in lag phase no increase in the number as I have already told you in previous module but the size of the cell can enlarge. But especially in exponential phase or a log phase number of cells also increased. In short we can say that there the exponential phase may be described as the microbial growth pattern. You can see here this simple 2x0 to mean double x0 is the amount of the biomass which we add as in an oculum. So as there is different multiplication of that so there are different generations mean if one cell become 2 and then in the same period 2 become 4 and 4 become 8. So how these if 1 cell and 2 cell is the in oculum level and then what will be the change. So as increase the generations and there is the same pattern of growth then there is a exponential change in the biomass with respect to time. So when 1 cell become 2 and 2 become 4 first generation that become the base of the next generation and in which the biomass become double to the existing one which we called as the doubling time that how much time is required to become the biomass doubled from the existing one. So that is only possible when all the cells autonomously and individually become doubled. So that is only happened when there is a sufficient amount of the substrate and then that have the equal chance of growth that is only possible when each and individual cells especially in case of unicellular or we can say that in term of bacteria and the yeast then they cell become grow and then how they become doubled. So that is considered as the doubling time.