Microbial Production of 2-Keto-l-Gulonic Acid froml-Sorbose andd-Sorbitol byGluconobacter melanogenus

Taxonomic characterization of Ketogulonigenium vulgare gen. nov., sp. nov. and Ketogulonigenium robustum sp. nov., which oxidize L-sorbose to 2-keto-L-gulonic acid.

“…We propose the new genus be named Ketogulonigenium based on the conspicuous production of 2-keto--gulonic acid from -sorbose by members of the proposed taxon. The newly isolated strains and strain DSM 4025 TP were distinguishable from Roseobacter, the nearest phylogenetic relative, and from Gluconobacter and Acetobacter, the other genera of α-Proteobacteria that oxidize -sorbose to 2-KLG (Imai et al, 1990 ;Sugisawa et al, 1990 ;Yin et al, 1990 ;Nogami et al, 1995). Although the isolates characterized in this study are similar to Roseobacter strains in that they are catalasepositive and oxidase-positive, there exist major phenotypic differences related to the energy metabolism of the two groups.…”

“…Although bacteria from several genera oxidize -sorbose to 2-keto--gulonic acid (Imai et al, 1990 ;Sugisawa et al, 1990 ;Yin et al, 1990 ;Nogami et al, 1995), the yield is generally insufficient to warrant commercial production of 2-KLG, a key intermediate in the chemical synthesis of vitamin C. We initiated a search for bacteria that generated higher yields of 2-KLG through the use of enrichment cultures supplemented with -sorbose. A high concentration of -sorbose was used in initial enrichments to provide sufficient substrate to achieve detectable levels of 2-KLG despite the potential for 2-KLG-degrading organisms to be active in the mixed-culture enrichments.…”

“…Alternatively, the exploitation of micro-organisms to synthesize vitamin C or vitamin C precursors has both economic and ecological advantages. A number of axenic and mixedculture microbial processes have been described for the biosynthesis of various intermediates in -ascorbic acid synthesis (Tengerdy, 1961a, b ;Imai et al, 1990 ;Sugisawa et al, 1990 ;Yin et al, 1990 ;Nogami et al, 1995). Abbreviation : 2-KLG, 2-keto-L-gulonic acid.…”

“…Members of a number of bacterial genera have been identified that produce 2-KLG from the oxidation of -sorbose (another intermediate of vitamin C synthesis). These include the acidophilic, α-Proteobacteria Gluconobacter and Acetobacter, the γ-Proteobacteria Pseudomonas, Escherichia, Klebsiella, Serratia and Xanthomonas, the Gram-positive Bacillus and Micrococcus (Imai et al, 1990 ;Sugisawa et al, 1990 ;Yin et al, 1990 ;Nogami et al, 1995), and the genus ' Pseudogluconobacter ' (Nogami et al, 1995). However, the yield of 2-KLG from these organisms is generally too low to be exploited industrially (for a review of vitamin C chemistry, natural biosynthesis and industrial synthesis, see Delic!…”

Metabolic Pathway for 2-Keto-l-gulonic Acid Formation inGluconohacter melanogenusIFO 3293

“…NAD, NADP, NADH, and NADPH were purchased from Oriental Yeast Industry Co., Ltd. 2,6-Dichlorophenolindophenol sodium' 2H 2 0 (DCIP) was purchased from Merck & Co., Inc. Ca-L-Idonate, L-idose, and L-sorbosone were kindly supplied by Hoffmann-La Roche Inc., Nutley, N.J., U.S.A. Microorganisms. Five mutants derived from Gluconobacter melanogenus SPO-1 3 ) were used. The phenotypes of these mutants are shown in Table I.…”