An all-around commercial oxygen sensor for fermentation off-gas monitoring

Fermentation off-gas monitoring for close to half a century have aided fermentation processes and their development in engineering labs, pilot plants and manufacturing plants.  It is used primarily in aerobic cultures where spent air leaving and occasionally sparged air entering the fermentor are monitored for its gaseous content or partial pressure of oxygen and/or carbon dioxide.  Together with air flow rate, inlet and outlet partial pressure differentials are then used to calculate rates of oxygen uptake (OUR) and/or carbon dioxide evolution (CER, mmol/L-h).  Among all process parameters available for on-line real time fermentation monitoring and control, OUR and CER are two of the most practical integral phenotype measurement indicative of overall culture robustness and reaction profiling in addition to their unique convenience in continuous and non-invasive sampling.  Fermentation off-gas monitoring is therefore non-disposable in productive high throughput phenotype culture screening.  However, costly analyzer and extensive hardware still hinder its move into most all labs.  When tied to a large reactor array, analyzer time sharing, gas sample plumbing and long measurement reading gaps further compromise its utility.  Hence, general or casual use of fermentation off-gas monitoring installation is still very much out of most labs reach.  Current work tries to demonstrate how a portable and consumable commercial oxygen gas sensor is adapted to all-around use anywhere in 24/7 fermentor off-gas monitoring.  Advantages over other oxygen and carbon dioxide gas analyzers include affordability, plug-and-play maintenance, long shelf life, high linearity, no need of standard gas, 0-100% partial pressure range, easy calibration, and sensor-to-sensor reproducibility.