INFLUENCE OF DILUTION RATE AND DISSOLVED-OXYGEN CONCENTRATION ON CONTINUOUS KETO ACID PRODUCTION BY GLUCONOBACTER-OXYDANS SUBSP MELANOGENUM

The influence of dilution rate and dissolved oxygen concentration on continuous production of 2,5-diketogluconic acid (2,5-DKGA) by Gluconobacter oxydans subsp. melanogenum is described. Under suitable dissolved oxygen conditions, the glucose oxidation rate is independent of variations in dilution rates over a wide range (D < 0.33 h-1). The higher dilution rate, however, leads to a partial oxidation of the substrate and therefore accumulation of more gluconic acid. Contrary to this, a longer residence time (lower dilution rate) was more suitable for better ketogenic activity, thereby facilitating accumulation of 2,5-DKGA in higher yields. A high dissolved oxygen concentration is further shown to positively influence the overall oxidation process through an organized induction of membrane-bound NAD(P)+-independent dehydrogenases.