 In this module, we will talk about again the some growth parameters in continuous culture. As we have seen in our previous module that the continuous culture and all the kinetic parameters is critical, we can say that dependent over the deletion rate. So, in this modules, we can say that when we say that as we have already discussed that what is chemostat, when we say that the whole fermentation kinetics and the growth rate is basically dependent upon some chemicals because in chemicals meanings, we can say all the substrate we are adding as a growth substrate, they are the chemicals. And when we say that there is a steady state that can be called as chemostat. So, here there is an alternative type of continuous culture which is sometimes when we can say that the chemostat is a turbidot state. This is a just different words that how we can use the term of chemostat and then we can change this chemostat into turbidostat. So, in this turbidostat, we can say that so, when the concentration of the cells is kept constant by the deletion rate which we can say that the flow of the medium that actually when we are adding something into the fermentation vessel and then the growth is happening that is basically the addition of the substrate and the growth of the organism combined effect on the turbidity of the medium have which have in the fermentation vessel. So, as well as we run this fermentation process, the turbidity of the medium or inside the fermentation vessel change. So, when we say that the growth will happen that change the turbidity inside the culture. So, when we say that we remain constant the turbidity of the fermentation vessels. So, that can be we check by the spectrophotomotorically. So, then we can say very a narrow limit of the change. So, that can be maintained not with this help of the substrate concentration not in term of the biomass concentration, we are not focusing the substrate concentration, we are not focusing that how much is the quantity of the biomass inside the fermentation, but we are only focusing the turbidity either that is due to the substrate or due to the number of the cells. So, sometimes it happen when there is a utilization of the substrate and there is the increase of the cell mass. So, by the depletion of the substrate turbidity reduced, but with the growth of the cells turbidity can increase sometime it happen when the medium color due to the substrate concentration is dark that can effect on the turbidity. So, this may be achieved by monitoring the biomass with photoelectric cells. So, the feeding the signal to the pump. So, when we say that there is a change in the turbidity that automatically send the signal to the pump to control the flow rate when there is a less turbidity then that will be decrease the dilution. So, if the flow rate will control with the turbidity meter that is attached with the photoelectric cells then we can achieve the state of turbidostat which is actually not the chemostat. So, the system other than turbidity may be used to monitor the biomass concentration. So, in this case when we say that turbidostat that is only when we only focus the turbidity of that, but there is another way by which we can have some steady state that when we only monitor the biomass concentration or so biomass concentration as we have studied in previous module that biomass concentration can be determined by various methods. So, that can be estimated by the carbon dioxide concentration or the pH change or by the respiration methods. So, if we estimating our biomass concentration so we are only focusing that how we can maintain the biomass. So, then that state if we are controlling our continuous culture with such growth rate determinant parameter so that state is known as a biostat. So, as we seen that what is the difference between chemostat, turbidostat and biostat. The biostat we have to clear about that the difference between this biostat term and another biostat term which is basically they use for the statistical implementation in the biology. So, that is another biostat that is biostatistics. So, this word which we called as the biostat that is basically the steady state conditions that is maintained through the biomass estimation inside the continuous culture fermentation. So, the chemostat is the more commonly used system rather to be turbidostat or a biostat. So, because it has the advantage over the biostat of not requiring the complex control system because that is very easy to control to maintain the steady state. However, the biostat has also the advantages over by turbidostat and chemostat with its own respect because it is more precise when we are talking about that what is the concentration of the biomass inside the fermentation vessel. So, when we are talking about that how this whole continuous culture have different changes with respect to the previous equation. We can see here that the effect of dilution rate on the steady state and the residual substrate concentration in chemostat. Then the microorganism with low K s value for the limiting substrate. So, how we can compare it with the substrate concentration? We can see that here there is a dark line is representing the steady state biomass concentration that how that is changed, but when such happening that the dotted line show the residual substrate. So, as well as the dilution rate will increase we can easily say when there will be a dilution rate increase then there is a gradually increase in the steady state residual substrate concentration that can be a maximize only up to a certain level. So, this graph can easily express that what is the difference between these two. So, as we have seen in the previous figure that the continuous culture behavior is hypothetically when we say that a bacterium with low K s value for the limiting substrate. So, with this increasing dilution rate the residual substrate concentration increased only to a certain limit when mu max will become the maximum. So, at that state we can say that that dilution when that become a maximum that we call as a critical dilution rate. So, the kinetic parameters of an organism when we can say that in a behavior of the chemo state that described by various numerical values why which is called as yield coefficient mu max and K s the monoid parameters. So, these can easily be expressed by these different parameters. So, if there is in a previous slide we have seen that if there is a low affinity with the K s, but in this graph we can see that when the K s value is high then how the dilution rate in steady state condition affect the fermentation conditions. So, you can see here that if there is a high K s value and then there is a biomass concentration decrease with the faster rate than in a low K s value and then the same case the residual substrate concentration increase with a rapid rate as compared to the low K s value. So, these two figures is very critical. So, when the growth in a substrate is a very linked with the K s value of that. So, if we know the K s value and the mu max which we called as the monoid parameter for any specific organism then that at what dilution rate there will be a mu max which we called as critical dilution or d critical. So, in such conditions when we say that the d critical is affected by different parameters that is mu max and K s. So, the larger SR mean substrate concentration the closer d critical to the mu max. So, however, the mu max can not be achieved in a simple steady state which we in a in a steady state which we called as chemostat. Because the substrate limiting conditions must always be sure to be prevail.