Kinetic model of hybridoma cultures for the identification of rate limiting factors and process optimisation

A methodology is proposed to evaluate which components of the culture medium limit the growth of mammalian cells during the culture. It is based on a kinetic model that describes the hybridoma growth decreasing and death enhancing effects of glucose, amino-acids, serum and oxygen depletion, on the one hand, and of ammonia and lactate accumulation on the other. This model correctly simulates the kinetics of a perfusion culture of hybridoma cells in a medium containing increasing lactate and ammonia levels. The developed model was then used as a process optimisation tool for the identification of the main rate limiting factors during the perfused culture. Under these culture conditions it appeared that increasing the ammonia concentration in the bioreactor had a dramatical effect on both cell growth and death, since a 70% inhibition of the specific cell growth rate and a fourfold increase of the specific death rate were reached. Unlike ammonium ions, the effect of lactate remained very low, even for concentrations higher than 30 mM.