Characterization of a biological test system for studies on insufficient mixing in bioreactors: H2 evolution from E. coli

A biological test system for mixing insufficiences, based on detection of hydrogen gas by oxygen-limited E. coli cells, was studied. It was characterized with respect to the relative oxygen uptake rate and the redox potential in the medium using a quantitative PdMOS-based hydrogen gas sensing system. Hydrogen gas was detected already at a relative oxygen uptake rate of 95%, but no other anaerobic products were formed in traceable amounts at this stage. It was not possible to correlate the relative oxygen uptake rate and the hydrogen production in a simple way. It was shown, however, that the specific production rate of hydrogen was linearly related to the redox potential during oxygen limitation.