Optimized synthesis of L-sorbose by C(5)-dehydrogenation of D-sorbitol with Gluconobacter oxydans.
The optimization of L-sorbose synthesis by regiospecific dehydrogenation of D-sorbitol using Gluconobacter oxydans is reported. The current L-sorbose production processes that are based on G. oxydans and other bacterial strains are suboptimal as to yield and rate of L-sorbose synthesis. One reason for these problems is the toxicity that is induced by the substrate D-sorbitol when used in concentrations of >10% (w/v). This phenomenon significantly limits the potentials of L-sorbose production from an industrial point of view. The goal of this study was to develop a fast production process that yields L-sorbose in stoichiometric amounts starting from D-sorbitol concentrations that exceed 10% (w/v). A gradual improvement of the inoculum build-up procedure, culture medium composition, and process parameters ultimately led to a theoretically maximal L-sorbose productivity (200 g L(-1) of L-sorbose from 200 g L(-1) of D-sorbitol in 28 h of fermentation) using a Gluconobacter oxydans mutant strain that was selected under conditions of substrate inhibition. Because the D-sorbitol/L&HYPHEN;sorbose bioconversion is used to mass-produce vitamin C, the procedure reported here will contribute to a more efficient and more economic synthesis of vitamin C.
De Wulf
P
P
Laboratory of Industrial Microbiology and Biocatalysis, Department of Biochemical and Microbial Technology, Ghent University, Belgium.
Soetaert
W
W
Vandamme
E J
EJ
D001205:Ascorbic Acid / Q000096:biosynthesis / Q000191:economics; D018533:Biomass; D002455:Cell Division / Q000187:drug effects; D003470:Culture Media / Q000737:chemistry / Q000378:metabolism; D005285:Fermentation; D020600:Gluconobacter oxydans / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006865:Hydrogenation; D007064:L-Iditol 2-Dehydrogenase / Q000378:metabolism; D009154:Mutation; D013012:Sorbitol / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D013013:Sorbose / Q000737:chemistry / Q000378:metabolism*; D013237:Stereoisomerism; D013997:Time Factors
D003470:Culture Media; D013012:Sorbitol; D007064:L-Iditol 2-Dehydrogenase; D013013:Sorbose; D001205:Ascorbic Acid