The processes completely run under the control of a process
control system (Siemens: Simatic PCS7 V7.1) which sampled all
signals every second.
Oxygen offgas analysis was performed by a Sick Maihak Sidor
analyzer based on ZrO2 technology. Carbon dioxide volume fraction
was measured with the same device using its infrared sensor.
The power consumption of the stirrer drive (ABB SDM-251-
004N8092/30-2000) was logged in the process control system. A
calibration function was derived relating the electrical power consumption
of the motor at impeller speed N with the mechanical
power it is transferring into the culture. In this way the losses in
the motor, the gear and the seal were considered. The calibration
technique is based on the heat production by the impeller in the
dispersion as described by.. Both, the heat
production from the agitator and metabolic heat produced by the
culture were so high that the heat loss into the laboratory environment
could be neglected.