| Autor: |
Kaup, Björn |
| Jazyk: |
angličtina |
| Rok vydání: |
2004 |
| Zdroj: |
Jülich : Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Berichte des Forschungszentrums Jülich 4155, 104 S. (2004). = Düsseldorf, Univ., Diss., 2004 |
| Popis: |
Aim of this work was the construction of recombinant Escherichia coli strains for the formation of D-mannitol from D-fructose and D-glucose in whole-cell biotransformations. First the NAD-dependent mannitol dehydrogenase from Leuconostoc pseudomesenteroides ATCC12291 was expressed in E. coli. Despite of its high enzyme activity this E. coli strain was not able to form D-mannitol from D-fructose as resting cell suspension in a whole-cell biotransformation. The coexpression of the NAD-dependent formate dehydrogenase of the methylotrophic Mycobacterium vaccae N10 for the regeneration of NADH resulted in the formation of a minor amounts of D-mannitol from D-fructose and formate, again regardless of high enzyme activities in the respective strain. Because D-fructose uptake in wildtype E. coli is catalysed by the PTS-system, this sugar is phosphorylated and therefore not a substrate of the mannitol dehydrogenase. This problem was overcome by the coexpression of the glucose facilitator of Zymomonas mobilis for uptake of D-fructose without concomitant phosphorylation. This strain was able to form D-mannitol up to a concentration of 1 M in a reaction time of 18 hours with a yield Y$_{D-mannitol/D-fructose}$ of 84 - 90 mol% from D-fructose and formate as substrates. The maximum specific productivity was 9,5 [g$_{Dmannitol}$x (g$_{CDW}$ x h)$^{-1}$]. However, this E. coli strain was not able to form D-mannitol from D-glucose. Therefore, glucose isomerases were supplemented to reaction mixture and the the glucose isomerase from E. coli was coexpressed. In both cases this resulted in D-mannitol formation solely from D-glucose as carbohydrate source and formate as source of redox equivalents without the participation of phosphorylated intermediates. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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