INFLUENCE OF CONSTANT AND OSCILLATING DISSOLVED-OXYGEN CONCENTRATION ON ASPERGILLUS-NIGER

The critical concentration of dissolved oxygen (DO) that determines the optimum capability of a microorganism depends upon the desired end product. Glucose oxidase (GOD) as a fermentation product is significantly influenced by oxygen in liquid phase. The DO concentration of 100% related to air at 1 bar is shown to be the threshold concentration for a several fold increase in production of the enzyme. By generating periodic sinusoidal DO oscillations during fermentation it is shown that the DO gradient prevailing in airlift loop reactors of industrial scale is advantageous for the induction of GOD. Additionally, the influence of periodic residence of Aspergillus niger at sub-optimal DO concentration on organized export of the enzyme into the medium is demonstrated.