Adaptive control at low glucose concentration of HEK-293 cell serum-free cultures

Fed-batch cultures were implemented to study the metabolism of HEK-293 cell s. Glucose, measured every 30 min by a FIA biosensor system, was maintained at 1 mM throughout the culture using an adaptive nonlinear controller base d on minimal process modeling. The controller performed satisfactorily at b oth low and high cell concentrations without the need for retuning between different culture phases. Overall, lactate production was significantly red uced by maintaining a low glucose concentration, thus decreasing the rate o f glycolysis. The rates of glucose and glutamine uptake as well as the lact ate and ammonia production were compared to those obtained in batch mode wi th an initial glucose concentration of 21 mM. Basically, three phases were observed in both culture modes. The metabolic shift from the first to the s econd phase was characterized by a significant reduction in glucose consump tion and lactate production while maximum growth rate was maintained. The s pecific respiration rate appeared unchanged during the first two phases, su ggesting that no change occurred in the oxidative pathway capacity. In the third phase, cell growth became slower very likely due to glutamine limitat ion.