 In this module, we will talk about the microbial growth kinetics some elaboration of the chemostat that how we can having the calculations of growth yield in chemostat. So, chemostat when we say that there is a continuous culture is going on and the chemostat conditions prevail that how we estimate the growth yield. Growth yield can be expressed with as we say in a first condition that is basically the how much is the number of biomass is produced mean dry cell mass produced. And then how much is the substrate utilize the ratio between the substrate utilization and the cell mass produced. But in second case that the change in biomass concentration as the ATP are the formed. So, the relationship between the ATP formed and the biomass produced. So, yield coefficient is related to the ATP concentration and then the yield coefficient can also be determined with respect to the oxygen concentration utilize when the biomass is produced. So, in these 3 cases then we can easily see that the yield with respect to ATP synthesis oxygen consumption is relatively constant for many organism. But the yield of the cells per mole of the ATP synthesize under condition which the energy substrate limitations and high growth rate which is approximately 10 plus 2 gram per cells then the yield of the cells per mole of ATP is not constant for all bacteria. So, it can be vary. So, we can say that the growth limiting or the growth rate is lower than the maximum rate. So, that is only when the different bacteria and the different organism have a different requirement. So, that can effect on the yield coefficient. So, when we say that that how the steady state condition in chemostat then we can say that in term of cell and substrate concentration steady state condition steady state conditions can be ensured by at least the 4 changes of the fermentor in the liquid volume. So, if we say there is a 4 changes then we can explain it with this example. So, if there is a 2 liter fermentation chemostat process with the flow rate which we say inlet and outlet. So, 0.5 liter per hour is the addition and 0.5 liter half liter is also the output then we can easily calculate the D. So, by easily we can say that if we divide 0.5 by 2 then is automatically the answer is 0.25 hours. So, if we just have a divided the 4 changes we have there that at least 4 changes in the fermentation condition. So, then we can have 4 over 0.25 per hours then we can say that the 4 16 hours are required for the change in the whole medium then when you say that the initial media can be fully changed in 16 hours. So, by this example we can easily say that how we can determine that the further condition. So, the steady state will be established after 16 hours then that change the growth condition of a chemostat. So, overall growth yield of this condition is this. So, we have already discussed this equation that yield coefficient is equal to x minus x naught over x naught minus S. So, the substrate concentration minus initial substrate concentration and then the initial substrate minus the residual substrate concentration. So, when we say that overall growth yield that is related to the maintenance and the growth requirement for the limiting substrate when the fermentation is going on then there is some maintenance inside the fermentation vessel. So, that act as basically the energy source in such condition we can say that. So, if we have the reciprocal of yield coefficient and then equation. So, then we have the equation where we say that M is the specific rate of the substrate uptake when cellular maintenance conditions are that. So, in this case when we say that this equation we can have where we say that M and y e can be estimated by plotting a graph between 1 over yield coefficient and 1 over specific growth rate. So, when there is a straight line so by the having the intercept is equal to 1 over yield coefficient and as well as the slope of that we can have the condition which we called as the M state. So, that is why by using this equation we can have in a simple way without the cell cycle.