Dehydrogenation of ribitol with Gluconobacter oxydans: production and stability of L-ribulose.
l-Ribulose is an important chiral lead molecule used for the synthesis of, among others, l-ribose, a high-value rare sugar used in the preparation of antiviral drugs. These drugs--nucleoside-analogues--gain importance in the treatment of severe viral diseases, like those caused by the HIV or hepatitis virus. In this study, factors that may have an impact on l-ribulose production with Gluconobacter oxydans and on the stability of l-ribulose were investigated. A bioconversion-type process, using washed resting cells, was chosen to produce l-ribulose from ribitol. In this process, the cell production and bioconversion phase were separated. The former was first optimized and a maximum cell mass of 1.5 g CDWL(-1) could be produced. For the bioconversion phase, the aeration level of the system proved to be one of the most critical factors; a maximal production rate of 15.7 g L(-1)h(-1) or 5.9 g(g CDW)(-1)h(-1) of l-ribulose could be reached. Furthermore, resting cells were found capable of completely converting ribitol solutions of up to 300 g L(-1) within 30 h, although the kinetics indicated a rather low affinity of the dehydrogenase enzymes for the substrate.
De Muynck
Cassandra
C
Laboratory of Industrial Microbiology and Biocatalysis, Department of Biochemical and Microbial Technology, Ghent University, Coupure links 653, B-9000 Gent, Belgium. Cassandra.DeMuynck@UGent.be <Cassandra.DeMuynck@UGent.be>
Pereira
Catarina
C
Soetaert
Wim
W
Vandamme
Erick
E
D000091:Acetobacter / Q000201:enzymology / Q000254:growth & development; D018533:Biomass; D002244:Carbon / Q000600:supply & distribution; D002452:Cell Count; D004355:Drug Stability; D020600:Gluconobacter oxydans / Q000201:enzymology* / Q000254:growth & development; D006863:Hydrogen-Ion Concentration; D008954:Models, Biological; D010088:Oxidoreductases / Q000378:metabolism* / Q000493:pharmacokinetics; D010100:Oxygen / Q000494:pharmacology; D010429:Pentoses / Q000096:biosynthesis* / Q000378:metabolism / Q000493:pharmacokinetics; D012255:Ribitol / Q000378:metabolism* / Q000493:pharmacokinetics; D013401:Sugar Alcohol Dehydrogenases / Q000378:metabolism / Q000493:pharmacokinetics; D013997:Time Factors
D010429:Pentoses; D012255:Ribitol; C100182:ribulose; D002244:Carbon; D010088:Oxidoreductases; D013401:Sugar Alcohol Dehydrogenases; C068251:L-ribose reductase; D010100:Oxygen