Continuous oxygen consumption estimation method for animal cell bioreactors based on a low-cost control of the medium dissolved oxygen concentration

The applications of animal cell cultures are becoming wider every day: protein and vaccine production, toxicity tests, development of tissue and cell therapies, as well as stem cell research. All of these issues, require the use of reliable bioreactors to ensure reproducible culture conditions and data collection. Some common functions of these systems are aeration, stirring, thermoregulation, pH control, so as measurement of variables like biomass density, pCO₂, pO₂, etc. However, for certain cell species, the traditional probes are not able to provide enough data to evaluate the cells metabolic response, in such cases the study of oxygen consumption becomes a useful tool, where OUR (Oxygen Uptake Rate) is one of the key parameters commonly used. The most straightforward current technique for on-line OUR determination is the 'Dynamic Method', however, this low cost strategy has some drawbacks that can be overcome if accurate control of the culture medium dissolved oxygen concentration is applied. This strategy is known as 'Stationary liquid phase balance method'. Previous realizations of the referred technique implied the use of expensive mass flow meters and constant gas flow rate to keep the dissolved oxygen concentration constant. An approach for a continuous OUR estimation method, taking profit of the advantages of both methods referred above is presented. Where pulse commanded pinch electrovalves can be used, instead of a mass flow meter, to provide pulse width modulated gas flow in order to keep the dissolved oxygen set-point. The OUR information can be directly estimated from the control loop parameters. The classical OUR dynamic method has been implemented in a six minibioreactor (10 ml) system (Hexascreen) using optical oxygen probes. The minibioreactor gas dynamics has been modelled and the proposed approach performance has been simulated and is being tested.