Expression of glf Z.m. increases D-mannitol formation in whole cell biotransformation with resting cells of Corynebacterium glutamicum |
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Authors: | Bäumchen Carsten Bringer-Meyer Stephanie |
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Institution: | (1) Institut für Biotechnologie 1, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany |
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Abstract: | A recombinant oxidation/reduction cycle for the conversion of D-fructose to D-mannitol was established in resting cells of Corynebacterium glutamicum. Whole cells were used as biocatalysts, supplied with 250 mM sodium formate and 500 mM D-fructose at pH 6.5. The mannitol dehydrogenase gene (mdh) from Leuconostoc pseudomesenteroides was overexpressed in strain C. glutamicum ATCC 13032. To ensure sufficient cofactor nicotinamide adenine dinucleotide (reduced form, NADH)] supply, the fdh gene encoding formate dehydrogenase from Mycobacterium vaccae N10 was coexpressed. The recombinant C. glutamicum cells produced D-mannitol at a constant production rate of 0.22 g (g cdw)−1 h−1. Expression of the glucose/fructose facilitator gene glf from Zymomonas mobilis in C. glutamicum led to a 5.5-fold increased productivity of 1.25 g (g cdw)−1 h−1, yielding 87 g l−1
D-mannitol from 93.7 g l−1
D-fructose. Determination of intracellular NAD(H) concentration during biotransformation showed a constant NAD(H) pool size
and a NADH/NAD+ ratio of approximately 1. In repetitive fed-batch biotransformation, 285 g l−1
D-mannitol over a time period of 96 h with an average productivity of 1.0 g (g cdw)−1 h−1 was formed. These results show that C. glutamicum is a favorable biocatalyst for long-term biotransformation with resting cells.
Dedicated to Prof. Hermann Sahm on the occasion of his 65th birthday. |
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Keywords: | Whole cell biotransformation NADH regeneration Corynebacterium glutamicum ATCC13032 D-Mannitol" target="_blank">D-Mannitol |
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