Design and characterization of a one-compartment scale-down system for simulating dissolved oxygen tension gradients

BACKGROUND: A laboratory scale one-compartment scale-down system (1-CSDS), used to generate dissolved oxygen tension (DOT) gradients was designed and characterized. The system consists of a 1.5-L stirred-tank bioreactor coupled to an automatic DOT controller that changes the oxygen partial pressure in the inlet gas through a feedback proportional-integral-derivative algorithm, while maintaining the hydrodynamic conditions constant. Oscillatory control of DOT was achieved by employing time-dependent square wave or sinusoidal setpoints.RESULTS: The 1-CSDS can be modeled as a first-order dynamic system, but showing a permanent lag between the system response and the setpoint. The 1-CSDS had a faster response rate for generating oscillating DOT when a square wave setpoint was used rather than a sinusoidal setpoint. The 1-CSDS generated symmetric DOT oscillations at periods above of 100 s.CONCLUSION: The 1-CSDS is suited to investigate the responses of microorganisms and cells, of biotechnological importance, to oscillatory DOT conditions. It was found that the response of the 1-CSDS was limited by the kLa. Copyright