Oxygen is a key nutrient in cell metabolism. Thus, culture oxygenation is a primary challenge. Whereas low oxygen concentrations negatively affect cell growth and biomass yield, excessive oxygen tension can be toxic to cells. pH (which is also a key physical parameter) can affect cell growth and must be kept at the optimum level. When working with mammalian cells, pH is optimised with CO2 (CO2 in this case acts as an acid). To control dissolved O2 concentration and pH of the medium, a sterile mixture of gases (air, O2, CO2) may be sparged into the medium.
MFCs control the amount and flow rate of each gas.