An overview of our online probe technologies at Culture
pH Probes
The measurement and control of pH during fermentation is critical for not only for cell health and productivity, but also for the quality of the product being made. Since pH is a log-scale measurement, maintaining tight control is a high priority and requires a reliable and responsive measurement technique.
Technology -
We use the Mettler Toledo inPro3253i for most processes
For processes with strong chemicals and solvents, we use Mettler Toledo InPro4260i/SG/120
If your process requires this probe, please contact us to ensure there is sufficient supply for your runs
Calibration -
The probes are autoclaved in the vessel and a one-point calibration is applied once the media in the vessel has achieved initial process condition setpoints
Storage and Lifespan -
Probes are cleaned after each run as guided by the manufacturer and stored in KCl to ensure hydration
Probe health, calibration stability, and autoclave cycle counts are monitored throughout each probe's lifespan and are discarded after they exceed our validated lifespan.
Dissolved Oxygen probes
Oxygen saturation is a critical measurement and control variable in fermentation. The amount of dissolved oxygen (DO) that will saturate a solution depends on temperature, pressure, and dissolved species (such as salts). We measure dissolved oxygen in the process liquid using an optical method described below.
Technology -
The probes we use, the Hamilton Visiferm Arc, excite a luminophore at the tip of the probe with a blue LED. The luminophore then emits in a red wavelength.
The quenching of the red emission by nearby molecules of oxygen changes the intensity and phase shift, which is then measured by the probe's sensor (a red-selective, filtered CCD).
At the bottom of the shaft is a screw-on cap that contains the luminophore dye layer. This cap can be replaced if the luminophore gets worn out (photobleached) or damaged physically. We currently use the H0 caps for most of our probes, but can alternatively use an H2 cap with a teflon separation layer that is more resistant to harsh environments.
If your process requires an H2 cap, please contact us to ensure there is sufficient supply for your runs
Calibration -
Preventative Maintenance: two point calibration
When the probe caps are replaced, the new cap goes through two point calibration using N2 and Air
Process calibration during vessel set up
Once the media in the reactor has reached process condition setpoints, the probes are calibrated to 100% saturation.
Storage and Lifespan -
Probes are cleaned after each run as guided by the manufacturer and stored dry and suspended to avoid scratching the cap membrane.
Probe cap health is monitored throughout each probe's lifespan and are replaced once they exceed our validated lifespan.
Temperature Probes
Technology -
We use a high accuracy PT-1000 RTD (resistance temperature detector) probe to measure process temp through a non-contact metal dip tube in the headplate (the thermowell).
The PT-1000 temperature probe is a resistance type thermometer. Where PT stands for platinum and 1000 is the measured resistance of the probe at 0˚C in ohms (1k at 0˚C). As the temperature changes the resistance of the platinum changes.
Calibration -
Calibration is performed by placing the PT-1000 in a well-stirred beaker of room temperature water and comparing against the lab’s NIST-traceable USB probe. Re-calibrations are performed during preventative maintenance and on an as needed basis.