Reaction engineering studies for the production of 2-hydroxyisobutyric acid with recombinant Cupriavidus necator H 16 |
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Authors: | Torben Hoefel Eva Wittmann Liv Reinecke Dirk Weuster-Botz |
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Affiliation: | 1. Lehrstuhl für Bioverfahrenstechnik, Technische Universit?t München, Boltzmannstr. 15, 85748, Garching, Germany 2. Evonik Degussa GmbH, Paul-Baumann-Str. 1, 45764, Marl, Germany
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Abstract: | Recombinant Cupriavidus necator H 16 with a novel metabolic pathway using a cobalamin-dependent mutase was exploited to produce 2-hydroxyisobutyric acid (2-HIBA) from renewable resources through microbial fermentation. 2-HIBA production capacities of different strains of C. necator H 16 deficient in the PHB synthase gene and genetically engineered to enable the production of 2-HIBA from the intracellular PHB precursor (R)-3-hydroxybutyryl-CoA were evaluated in 48 parallel milliliter-scale stirred tank bioreactors (V = 11 mL). The effects of media composition, limitations, pH, and feed rate were studied with respect to the overall process performances of the different recombinant strains. 2-HIBA production was at a maximum at nitrogen limiting conditions and if the pH was controlled between 6.8 and 7.2 under fed-batch operating conditions (intermittent fructose addition). The final concentration of 2-HIBA was 7.4 g L−1 on a milliliter scale. Best reaction conditions identified on the milliliter scale were transferred to a laboratory-scale fed-batch process in a stirred tank bioreactor (V = 2 L). Two different process modes for the production of 2-HIBA, a single-phase and a dual-phase fermentation procedure, were evaluated and compared on a liter scale. The final concentration of 2-HIBA was 6.4 g L−1 on a liter scale after 2 days of cultivation. |
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