Influence of dissolved oxygen concentration on the oxygen kinetics of Gluconobacter oxydans

Abstract

As shown in earlier studies in production scale bioreactors oxygen limited zones occur. Microorganisms in these reactors are therefore subjected to concentrations of oxygen varying with time. To simulate these conditions, the effect of low oxygen concentrations upon product formation and kinetics of oxygen of Gluconobacter oxydans are studied at laboratory scale. Under these oxygen limited conditions comparable kinetic parameters for oxygen are observed as under normally aerated conditions. So, a saturation constant for oxygen K O 2=6.9 μmol/l is observed, which is equivalent to a DOT value of about 3% of air saturation. For optimization purposes of production scale conditions, gassing with oxygen enriched air or with pure oxygen is one of the possibilities. To study the effect of high oxygen concentrations upon kinetics and product formation, the organisms are also cultivated under these extreme conditions. Although at oxygen concentrations larger then 60% saturation with pure oxygen, still growth was observed, the growth rate and also the product formation rate were strongly diminished. From these experiments it can be concluded that gassing with pure oxygen to achieve higher oxygen transfer rates at production scale will be restricted.