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Efficient aerobic succinate production from glucose in minimal medium with Corynebacterium glutamicum.

Litsanov B, Kabus A, Brocker M, Bott M - Microb Biotechnol (2011)

Bottom Line: By deleting genes for all known acetate-producing pathways (pta-ackA, pqo and cat) acetate production could be strongly reduced by 83% and succinate production increased up to 7.8 g l(-1) (66 mM).Whereas overexpression of the glyoxylate shunt genes (aceA and aceB) or overproduction of the anaplerotic enzyme pyruvate carboxylase (PCx) had only minor effects on succinate production, simultaneous overproduction of pyruvate carboxylase and PEP carboxylase resulted in a strain that produced 9.7 g l(-1) (82 mM) succinate with a specific productivity of 1.60 mmol g (cdw)(-1) h(-1).This value represents the highest productivity among currently described aerobic bacterial succinate producers.

View Article: PubMed Central - PubMed

Affiliation: Institut für Bio- und Geowissenschaften, IBG-1: Biotechnologie, Forschungszentrum Jülich, D-52425 Jülich, Germany.

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Comparison of biomass formation (A), glucose consumption (B), succinate production (C) and acetate production (D) of C. glutamicum wild type (squares, n = 3), C. glutamicumΔsdh (circles, n = 4) and C. glutamicum BL‐1 (triangles, n = 2) in aerobic batch cultivations in modified CGXII medium containing 4% (w/v) glucose under constantly controlled conditions of pH 7.0 and pO2 > 30% using a Multifors bioreactor system. The results displayed are mean values from n independent experiments.
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f2: Comparison of biomass formation (A), glucose consumption (B), succinate production (C) and acetate production (D) of C. glutamicum wild type (squares, n = 3), C. glutamicumΔsdh (circles, n = 4) and C. glutamicum BL‐1 (triangles, n = 2) in aerobic batch cultivations in modified CGXII medium containing 4% (w/v) glucose under constantly controlled conditions of pH 7.0 and pO2 > 30% using a Multifors bioreactor system. The results displayed are mean values from n independent experiments.

Mentions: During aerobic metabolism C. glutamicum uses the TCA cycle for generation of reducing equivalents and precursors for amino acids (Bott, 2007). Under these conditions succinate is an intermediate of the oxidative TCA cycle and does not accumulate in the supernatant. In order to allow the accumulation of succinate as an end‐product of aerobic metabolism, the succinate dehydrogenase complex encoded by the sdhCAB genes must be inactivated. For this purpose, a C. glutamicumΔsdhCAB deletion mutant was constructed which is completely unable to oxidize succinate to fumarate (Fig. 1). The growth behaviour and product formation of this strain were compared with those of the wild type. For this purpose, independent batch cultivations in modified CGXII medium with 4% (w/v) glucose as carbon source were performed in the Multifors bioreactors. To prevent acidification of the medium caused by organic acid production the pH was kept at 7.0. Oxygen limitation was avoided by keeping pO2 at > 30% saturation. During cultivation growth, glucose consumption and organic acid production were measured (Fig. 2). Corynebacterium glutamicumΔsdhCAB exhibited a 9% reduced growth rate and 28% decreased biomass formation compared with the wild type (Table 1). The wild‐type cells consumed glucose with an uptake rate of 4.30 mmol g (cdw)−1 h−1 and did not produce measurable quantities of succinate or other organic acids in the culture broth. Corynebacterium glutamicumΔsdhCAB showed growth‐coupled accumulation of succinate from the beginning of the cultivation up to the end of the exponential growth phase with a specific production rate of 0.75 mmol g (cdw)−1 h−1. At the end of the cultivation after 22.5 h the succinate concentration in the supernatant reached 40 mM. The succinate yield (0.18 mol mol−1 glucose) represented 18% of the theoretically maximal yield (1 mol succinate mol−1 glucose). The major product formed during cultivation of C. glutamicumΔsdhCAB was acetate, which accumulated in parallel to succinate and reached a concentration of 125 mM (0.56 mol mol−1 glucose) after 22.5 h.


Efficient aerobic succinate production from glucose in minimal medium with Corynebacterium glutamicum.

Litsanov B, Kabus A, Brocker M, Bott M - Microb Biotechnol (2011)

Comparison of biomass formation (A), glucose consumption (B), succinate production (C) and acetate production (D) of C. glutamicum wild type (squares, n = 3), C. glutamicumΔsdh (circles, n = 4) and C. glutamicum BL‐1 (triangles, n = 2) in aerobic batch cultivations in modified CGXII medium containing 4% (w/v) glucose under constantly controlled conditions of pH 7.0 and pO2 > 30% using a Multifors bioreactor system. The results displayed are mean values from n independent experiments.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3815278&req=5

f2: Comparison of biomass formation (A), glucose consumption (B), succinate production (C) and acetate production (D) of C. glutamicum wild type (squares, n = 3), C. glutamicumΔsdh (circles, n = 4) and C. glutamicum BL‐1 (triangles, n = 2) in aerobic batch cultivations in modified CGXII medium containing 4% (w/v) glucose under constantly controlled conditions of pH 7.0 and pO2 > 30% using a Multifors bioreactor system. The results displayed are mean values from n independent experiments.
Mentions: During aerobic metabolism C. glutamicum uses the TCA cycle for generation of reducing equivalents and precursors for amino acids (Bott, 2007). Under these conditions succinate is an intermediate of the oxidative TCA cycle and does not accumulate in the supernatant. In order to allow the accumulation of succinate as an end‐product of aerobic metabolism, the succinate dehydrogenase complex encoded by the sdhCAB genes must be inactivated. For this purpose, a C. glutamicumΔsdhCAB deletion mutant was constructed which is completely unable to oxidize succinate to fumarate (Fig. 1). The growth behaviour and product formation of this strain were compared with those of the wild type. For this purpose, independent batch cultivations in modified CGXII medium with 4% (w/v) glucose as carbon source were performed in the Multifors bioreactors. To prevent acidification of the medium caused by organic acid production the pH was kept at 7.0. Oxygen limitation was avoided by keeping pO2 at > 30% saturation. During cultivation growth, glucose consumption and organic acid production were measured (Fig. 2). Corynebacterium glutamicumΔsdhCAB exhibited a 9% reduced growth rate and 28% decreased biomass formation compared with the wild type (Table 1). The wild‐type cells consumed glucose with an uptake rate of 4.30 mmol g (cdw)−1 h−1 and did not produce measurable quantities of succinate or other organic acids in the culture broth. Corynebacterium glutamicumΔsdhCAB showed growth‐coupled accumulation of succinate from the beginning of the cultivation up to the end of the exponential growth phase with a specific production rate of 0.75 mmol g (cdw)−1 h−1. At the end of the cultivation after 22.5 h the succinate concentration in the supernatant reached 40 mM. The succinate yield (0.18 mol mol−1 glucose) represented 18% of the theoretically maximal yield (1 mol succinate mol−1 glucose). The major product formed during cultivation of C. glutamicumΔsdhCAB was acetate, which accumulated in parallel to succinate and reached a concentration of 125 mM (0.56 mol mol−1 glucose) after 22.5 h.

Bottom Line: By deleting genes for all known acetate-producing pathways (pta-ackA, pqo and cat) acetate production could be strongly reduced by 83% and succinate production increased up to 7.8 g l(-1) (66 mM).Whereas overexpression of the glyoxylate shunt genes (aceA and aceB) or overproduction of the anaplerotic enzyme pyruvate carboxylase (PCx) had only minor effects on succinate production, simultaneous overproduction of pyruvate carboxylase and PEP carboxylase resulted in a strain that produced 9.7 g l(-1) (82 mM) succinate with a specific productivity of 1.60 mmol g (cdw)(-1) h(-1).This value represents the highest productivity among currently described aerobic bacterial succinate producers.

View Article: PubMed Central - PubMed

Affiliation: Institut für Bio- und Geowissenschaften, IBG-1: Biotechnologie, Forschungszentrum Jülich, D-52425 Jülich, Germany.

Show MeSH
Related in: MedlinePlus