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Product yields of biologicals such as monoclonal antibodies, recombinant proteins and vaccines produced in mammalian cell culture have to be improved constantly to cope with increasing demands and process economics. Real-time monitoring of metabolic activity of cells becomes more and more important for controlling animal cell culture, but there is still a lack of sensors for on-line measurements. The oxygen uptake rate is one indicator for metabolic activity of mammalian cells, but the determination of OUR using a gas balance is quite inaccurate due to the low oxygen uptake of cells resulting in small differences of air inlet and outlet of bioreactors.
Bennett and Kempe [1] investigated oxygen transfer mechanism in bioreactors with and without aeration. Oxygen uptake rate was calculated using the concentration of dissolved oxygen. This approach was adapted for animal cell culture using pulsed aeration [2] were the decrease of the dissolved oxygen partial pressure between pulses allows determining oxygen uptake rates.
Here, we present experimental data of an influenza vaccine production process with adherently growing Madin Darby canine kidney cells (MDCK) [3]. Cultivations were performed in 5 L bioreactors with pulsed, discontinuous bubble aeration for oxygen supply. Similar to data given for other animal cells [4] the average specific oxygen uptake rate (qO2) during cell growth was 20 amol s-1. Slopes of dissolved oxygen uptake between pulses allowed the calculation of cumulative oxygen consumption, which correlated with the increase of cell number during cell growth phase and with cell death during virus replication phase.
[1] Bennett and Kempe, 1964. Biotech Bioeng; 6: 347-360
[2] Biotechnology Vol.4: Measuring, Modelling and Control. 1991. p 36. Edited by H.-J. Rehm and G. Reed. VCH Verlagsgesellschaft Weinheim New York Basel Cambridge
[3] Genzel et al., 2006. Vaccine, 24(16), 3261-3272
[4] Mammalian cell biotechnology in Protein Production. 1997. p 221, Edited by H. Hauser and R. Wagner. Walter de Gruyter Berlin New York
