Abstract: 2,5-Diketo-D-gluconic acid is prepared in high yield and in high broth concentration by cultivating newly isolated microorganisms of genus Erwinia in an aqueous nutrient medium in the presence of D-glucose. The production is also possibly by simple contact of said microorganisms or their processed products therefrom, with D-glucose.

Abstract: 2,5-Diketo-D-gluconic acid is prepared in high yield and in high broth concentration by cultivating newly isolated microorganisms of genus Erwinia in an aqueous nutrient medium in the presence of D-glucose. The production is also possible by simple contact of said microorganisms or their processed products therefrom, with D-glucose.

Abstract: 2,5-Diketo-D-gluconic acid is prepared in high yield and in high broth concentration by cultivating newly isolated microorganisms of genus Erwinia in an aqueous nutrient medium in the presence of D-glucose. The production is also possible by simple contact of said microorganisms or their processed products therefrom, with D-glucose.

Abstract: 2-Keto-L-gulonic acid is prepared directly from D-glucose by microbial conversion utilizing mixed culturing on a medium containing D-glucose, employing two kinds of microorganisms; the first, a 2,5-diketo-D-gluconic acid producing microorganism which belongs to genus Erwinia and the second, a 2-keto-L-gulonic acid producing microorganism which belongs to genus Brevibacterium or Corynebacterium. The incubation of the microorganisms in a medium containing D-glucose is used in the disclosed process. By-production of 2-keto-D-gluconic acid, the undesired isomer of the intended product is effectively prevented by employing mixed culturing because of the co-existence of both microorganisms in the medium during at least part of the entire cultivation. Namely, 2-keto-D-gluconic acid produced by the second microorganism is utilized by the first microorganism to produce 2,5-diketo-D-gluconic acid which is subsequently converted into 2-keto-L-gulonic acid by the second microorganism.

Abstract: Fermentative or enzymatic production of 2-keto-L-gulonic acid from 2,5-diketo-D-gluconic acid using living or processed mutants, being defective in metabolizing 5-keto-D-gluconic acid and incapable of producing 2-keto-D-gluconic acid. The mutant is derived from 2-keto-L-gluconic acid producing microorganisms of genus Corynebacterium. The production is carried out in the presence of nitrates and/or hydrogen donors in a preliminarily sterilized fermentation broth in which a 2,5-diketo-D-gluconic acid producing microorganism of genus Gluconobacter or Erwinia has been cultivated.

Abstract: 2-Keto-L-gulonic acid is prepared directly from D-glucose by microbial conversion utilizing mixed culturing on or mixed contacting with a medium containing D-glucose, employing at least two kind of microorganisms; 2,5-diketo-D-gluconic acid producing strains which belong to the genera of Acetobacter, Acetomonas and Gluconobacter and strains capable of converting the 2,5-diketo-D-gluconic acid into 2-keto-L-gulonic acid which belong to the general of Brevibacterium and Corynebacterium. Both the incubation of the microorganisms in a medium containing D-glucose and the direct contact of any products obtained from the cells of the microorganisms with the substrate may be used in the disclosed process.

Abstract: 2-Keto-L-gulonic acid is prepared from 2,5-diketo-D-gluconic acid through microbial conversion. The 2-keto-L-gulonic acid producing microorganism available for this microbial conversion includes strains which belong to the species of the Brevibacterium nov. sp. ASM-856-4, ATCC 31083. The incubation of the microorganism in a medium containing 2,5-diketo-D-gluconic acid as well as the direct contact of any products obtained from the microbial cells with a substrate containing said 2,5-diketo-D-gluconic acid may be used in the disclosed process.

Abstract: 2-Keto-L-gulonic acid is prepared from 2,5-diketo-D-gluconic acid through microbial conversion. The 2-keto-L-gulonic acid producing microorganism available for this microbial conversion includes strains which belong to the genus Corynebacterium. The incubation of the microorganism in a medium containing 2,5-diketo-D-gliconic acid as well as the direct contact of any products obtained from the microbial cells with a substrate containing said 2,5-diketo-D-gluconic acid may be used in the disclosed process.