Which are the values of stirrer speed and air flow rate you are employing?
Perhaps the oxygen transfer rate (OTR) you are introducing in the vessel is not enough because the strain needs more oxygen that you are introducing into the system.
Have you worked before in a smaller vessel to know the best OTR to be used?
300-600 rpm( Cascade) is the stirrer speed. We use 1LPM air and oxygen as a cascade unit. We have antifoam too. This thing arises in every batch we perform. Growth itself varies in every batch. Plz suggest me a way to find out the issue.
You use 1 l/min or 1 vvm?
Have you performed any run at a smaller scale to determine the OUR of your strain?
sorry my bad. it is 1 vvm. But definitely it keeps varying through the different batches we produce. What do you think the main constraint in E.coli fed-batch fermentation?
I think you have to have prevgious information at smaller scale (1 or 2 liters work volume) both in batch and fed batch fermentation, because the scale up to 10 L is not linear.
Ok mam. Thank you for your time and valuable suggestion. I would like to get more information from you in future.
The reason for such behaviour of the DO probe may not necessarily by of a "biological" origin as the former discussion suggests... It can be simply due to the functioning of the very DO probe. It is common that after connecting a DO probe to a fermenter, its readings first rapidly increase and then decrease before reaching a stable value. This is due to the time necessary to polarize the probe and it can be in the scale of 1-2 hours. If the probe is not fully polarized its readings are wrong and can be misleading. One should check first this point after trying to find out "biologically" based explanations.
More information.
Type of medium and concentrations of ingredients
DO Concentration
Picture of your DO time lapse
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