How so that when air is introduced in culture medium than pH rises and when pure oxygen is used than it does not. There is bicarbonate in medium presented and hybridoma cells cultivated.
The fermenter's broth may possibly be closer to O2 saturation if pure O2 gas is being sparged into the broth, rather than air, meaning that the dissolved oxygen concentration (DO) may (seemingly) be higher for the former case. If the pH is not being controlled, it may be influenced by DO due to its effect in the metabolic activity, as the medium composition may change accordingly. Of particular significance could be the dissolved CO2 concentration due to the equilibrium with the bicarbonate ion: 2H2O + CO2 ↔ H3O+ + HCO3-. The DO, which is typically accessed with a polarographic oxygen electrode, can be accessed and controlled as described at the following reference:
Thesis Controlo do Oxigénio Dissolvido em Fermentadores para Minimi...
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