I have problem in cho cell scale up. Cells grow well in 5000L bioreactor and reach to more than 20milion cells per ml like 1000L but OUR and Glucose consumption and QP decrease dramatically
Seems that cells only uptake glucose to remain live!
Glucose consumption is correlated with oxygen consumption and mAb expression, are you receiving yields that are comparable to your calculated scale up extrapolation? If not then it could be an issue of insufficient permeation and/or oxygenation. The kinetic rate law for cell density will be 1st order but zero order for oxygen so these variables don't scale with direct proportionality.
Also, are you monitoring acidification? In order to ameliorate reductive stress cells will oxidize NADPH via glycolysis, which can be detected by the levels of lactic acid excretion. CHO cells have the highest oxygen usage in the exponential phase, the lowest during plateau, but are increased during lag phase (likely due to redox adjustments of thiols in the extracellular matrix, driven by ATP and O2 consumption via the pentose pathway).
Dear Vincent,
Thanks for your answer. About acidification, we have a constant pattern of lactate production in all scales, lactate increases fast during log phase then consumes in stationary phase and reaches near zero.
Our scale up parameters are based on vvm for oxygenation and we use pure o2. As you said, glucose consumtion is related to oxygen uptake, but in our large scale oxygen uptakes slowly. Im agree with you, our problem meybe is related to permeation, can you give me more information and recommendation about this?
In engineering it is solved with eductors that force an oxygen stream in the center of liquid intake ducts that flows into a device that facilitates the venturi effect. I'm not sure if there is a "soft" version of this, if it were me I would investigate using a system similar to grain silos. They are constructed with a metal subframe that is specifically designed to force air evenly from bottom. I know that there are several ultrasonically-microdispersed gas delivery systems that can be purchased commercially or made in-house so that it can be retrofitted to the precise dimensions of the bottom of the bio-reactor tank. As long as the components are sterilized to spec (eto or autoclave?), and sealed tightly around the edges and oxygen inlet valve couplings, it should allow for better control and homogenous dispersion, exposure, and uptake of oxygen.
Alternatively, you could try implementing air spargers with microdispersion to test the under-oxygenation hypothesis. If your results improve but are still not optimal then you can proceed with a more comprehensive approach.
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