The Effects of pH on 5-Oxogluconate Production by Gluconobacter Suboxydans

The metabolism of glucose to 5-oxogluconate by Gluconobacter oxydans subsp. suboxydans (Gluconobacter suboxydans) at different pH values, glucose concentrations and phosphate buffer concentrations was studied. Bacterial growth, gluconic acid accumulation and 5-oxogluconate production were related to both pH and phosphate buffer concentration in the medium. In media containing 2-3% glucose, 0.3% yeast extract and 0.3 M phosphate buffer, the optimal pH range for the bacterial growth was pH 6.4-7.0; the optimal pH range for gluconate production was pH 6.4-6.8; and the optimal pH range for 5-oxogluconate production was pH 6.6-7.0. Lowering the pH to 6.4 favored gluconate accumulation from glucose; an increase in pH after maximum gluconate accumulation increased the yield of 5-oxogluconate from gluconate. A medium with the initial pH below pH 3.5 or above pH 7.5 slowed the metabolic rate of the bacteria. An increase in phosphate buffer over 0.3 M decreased the metabolic rate of the cells. The calculated weight-yield of 5-oxogluconate using 2.0% glucose, 0.3% yeast extract, 0.3 M phosphate, pH 6.75 was approximately 60%