Process for producing 2-keto-D-gluconic acid by high-concentration fermentation

The invention discloses a process for producing 2-keto-D-gluconic acid by high-concentration fermentation. A microorganism for converting glucose into the 2-keto-D-gluconic acid or salt of the 2-keto-D-gluconic acid is cultured in a fermentation container, as a carbon source in a fermentation culture medium, the glucose is subjected to fermentation culture, and the pH (Potential Of Hydrogen) value before sterilization is 5.5-7.0; and the fermentation culture medium consists of the following substances by massvolume: 10-32% of glucose, 0.1-1% of maize pulp, 1-5% of calcium hydroxide, 0.02-0.08% of de-foaming agent and a solvent as water. The pH value is adjusted by calcium hydroxide in the beginning of fermentation so that the cost is lower, the pH value of a fermentation solution is more accurately adjusted and controlled by liquid ammonia or ammonia water in the mid- to late-period of fermentation so that the fermentation solution is kept in the environment for optimal growth and acid production of the micro