A Gluconobacter oxydans mutant converting glucose almost quantitatively to 5-keto-D-gluconic acid.
Gluconobacter oxydans converts glucose to gluconic acid and subsequently to 2-keto-D-gluconic acid (2-KGA) and 5-keto-D-gluconic acid (5-KGA) by membrane-bound periplasmic pyrroloquinoline quinone-dependent and flavin-dependent dehydrogenases. The product pattern obtained with several strains differed significantly. To increase the production of 5-KGA, which can be converted to industrially important L-(+)-tartaric acid, growth parameters were optimized. Whereas resting cells of G. oxydans ATCC 621H converted about 11% of the available glucose to 2-KGA and 6% to 5-KGA, with growing cells and improved growth under defined conditions (pH 5, 10% pO2, 0.05% pCO2) a conversion yield of about 45% 5-KGA from the available glucose was achieved. As the accumulation of the by-product 2-KGA is highly disadvantageous for an industrial application of G. oxydans, a mutant was generated in which the membrane-bound gluconate-2-dehydrogenase complex was inactivated. This mutant, MF1, grew in a similar way to the wild type, but formation of the undesired 2-KGA was not observed. Under improved growth conditions, mutant MF1 converted the available glucose almost completely (84%) into 5-KGA. Therefore, this newly developed recombinant strain is suitable for the industrial production of 5-KGA.
Elfari
Mustafa
M
Fachgebiet Technische Biochemie, Institut für Biotechnologie der Technischen Universität Berlin, Seestr. 13, 13353, Berlin, Germany.
Ha
Seung-Wook
SW
Bremus
Christoph
C
Merfort
Marcel
M
Khodaverdi
Viola
V
Herrmann
Ute
U
Sahm
Hermann
H
Görisch
Helmut
H
D005285:Fermentation; D005942:Gluconates / Q000378:metabolism*; D020600:Gluconobacter oxydans / Q000235:genetics* / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D007218:Industrial Microbiology; D009154:Mutation
D005942:Gluconates; C008229:2-ketogluconate; C093583:5-ketogluconic acid; D005947:Glucose; C030691:gluconic acid