Oxygen uptake rate measurements both by the dynamic method and during the process growth of Rhodococcus erythropolis IGTS8: Modelling and difference in results

Abstract

Oxygen uptake rate (OUR) during growth of Rhodococcus erythropolis IGTS8, a natural desulphurizing bacterium, is measured using two experimental methods for the same set of experiments performed in a 2 L work volume commercial bioreactor. The experimental OUR values obtained by the usual “dynamic method” were compared to those obtained by the “process method” after fitting the values of oxygen concentration measured during cell growth process. Experimental OUR values obtained from the ‘process method’ are always higher than those from the ‘dynamic method’. This discrepancy is explained by the cell economy principle: during the few minutes employed to measure OUR using the dynamic method, the cells do not use oxygen to synthesize 4S desulphurization route enzymes. The experimental values obtained by both methods are modelled to describe oxygen consumption using three parameters: consumption for growth ( Y OX) and for maintenance ( m O 2 ), as usual, and the oxygen consumption to synthesize Dsz enzymes by means of a yield of oxygen into ‘biodesulphurization capability’ ( Y OBDS). Oxygen concentration profile during growth is closely described using the final model proposed.