We have a partner who calibrates their DO probe before sterilization. nitrogen gas for zero and ambient air fro 100%. These are large units up to 10,000L. After sterilization the %DO is 130%. Would this be caused by an increase in temperature ~28C as well as back pressure perhaps. What else could present this %DO. As the fermentation proceeds the DO does drop and is maintained between 20-50%. Thanks!
Maybe you can find this RG discussion of some help: https://www.researchgate.net/post/What_is_the_proper_way_to_perform_DO_probe_calibration
In a fermenter, DO is always calibrated after sterilization. If you are using electrochemical DO probe then u should connect the probe to the control system after sterilization and leave for 6-8 hours. This is done for polarisation. It is required for establishing proper circuit. Sterilization at high temperatures affect the solution in the probe and hence it doesn't retain the calibration.
Always calibrate DO probe after sterilization at the temperature and pH of the medium you will use.
Sterilization of the do probe need to be done after Sterilization and when the medium is cooled down to the desired working temperature. But immediately after sterilization the do connections should be restored and atleast 6 hour repolarization time is required for DO probe after being disconnected from the control unit which makes it depolarised.
Moreover, its also necessary to check electrolyte level, no air bubble should be preset inside probe and the DO membrane should also be checked for damage before its operation
- Badges
- Science method