Comparison of metabolic pathway for hydrogen production in wild-type and mutant Clostridium tyrobutyricum strain based on metabolic flux analysis

2013 ◽  
Vol 38 (5) ◽  
pp. 2176-2184 ◽  
Author(s):  
Ling Jiang ◽  
Ping Song ◽  
Liying Zhu ◽  
Shuang Li ◽  
Yi Hu ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Metabolic Pathway ◽  
Metabolic Flux Analysis ◽  
Metabolic Flux ◽  
Flux Analysis ◽  
Clostridium Tyrobutyricum ◽  
Wild Type

Metabolic flux analysis of the hydrogen production potential in Synechocystis sp. PCC6803

2009 ◽  
Vol 34 (21) ◽  
pp. 8828-8838 ◽  
Author(s):  
E. Navarro ◽  
A. Montagud ◽  
P. Fernández de Córdoba ◽  
J.F. Urchueguía
Keyword(s):  
Hydrogen Production ◽  
Metabolic Flux Analysis ◽  
Metabolic Flux ◽  
Flux Analysis ◽  
Production Potential ◽  
Synechocystis Sp

scholarly journals Comparative13C Metabolic Flux Analysis of Pyruvate Dehydrogenase Complex-Deficient, l-Valine-Producing Corynebacterium glutamicum

2011 ◽  
Vol 77 (18) ◽  
pp. 6644-6652 ◽  
Author(s):  
Tobias Bartek ◽  
Bastian Blombach ◽  
Siegmund Lang ◽  
Bernhard J. Eikmanns ◽  
Wolfgang Wiechert ◽  
...  
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Metabolic Flux Analysis ◽  
Metabolic Flux ◽  
Pyruvate Dehydrogenase Complex ◽  
Pentose Phosphate ◽  
Strong Increase ◽  
Flux Analysis ◽  
Wild Type ◽  
Content Type ◽  
Split Ratio

ABSTRACTl-Valine can be formed successfully usingC. glutamicumstrains missing an active pyruvate dehydrogenase enzyme complex (PDHC). Wild-typeC. glutamicumand four PDHC-deficient strains were compared by13C metabolic flux analysis, especially focusing on the split ratio between glycolysis and the pentose phosphate pathway (PPP). Compared to the wild type, showing a carbon flux of 69% ± 14% through the PPP, a strong increase in the PPP flux was observed in PDHC-deficient strains with a maximum of 113% ± 22%. The shift in the split ratio can be explained by an increased demand of NADPH forl-valine formation. In accordance, the introduction of theEscherichia colitranshydrogenase PntAB, catalyzing the reversible conversion of NADH to NADPH, into anl-valine-producingC. glutamicumstrain caused the PPP flux to decrease to 57% ± 6%, which is below the wild-type split ratio. Hence, transhydrogenase activity offers an alternative perspective for sufficient NADPH supply, which is relevant for most amino acid production systems. Moreover, as demonstrated forl-valine, this bypass leads to a significant increase of product yield due to a concurrent reduction in carbon dioxide formation via the PPP.

scholarly journals Metabolic flux analysis of wild-type Escherichia coli and mutants deficient in pyruvate-dissimilating enzymes during the fermentative metabolism of glucuronate

Microbiology ◽  
2010 ◽  
Vol 156 (6) ◽  
pp. 1860-1872 ◽  
Author(s):  
Abhishek Murarka ◽  
James M. Clomburg ◽  
Ramon Gonzalez
Keyword(s):  
Escherichia Coli ◽  
Metabolic Flux Analysis ◽  
Metabolic Flux ◽  
Reducing Power ◽  
Building Blocks ◽  
Exponential Phase ◽  
Flux Analysis ◽  
Wild Type ◽  
Fermentative Metabolism

The fermentative metabolism of d-glucuronic acid (glucuronate) in Escherichia coli was investigated with emphasis on the dissimilation of pyruvate via pyruvate formate-lyase (PFL) and pyruvate dehydrogenase (PDH). In silico and in vivo metabolic flux analysis (MFA) revealed that PFL and PDH share the dissimilation of pyruvate in wild-type MG1655. Surprisingly, it was found that PDH supports fermentative growth on glucuronate in the absence of PFL. The PDH-deficient strain (Pdh−) exhibited a slower transition into the exponential phase and a decrease in specific rates of growth and glucuronate utilization. Moreover, a significant redistribution of metabolic fluxes was found in PDH- and PFL-deficient strains. Since no role had been proposed for PDH in the fermentative metabolism of E. coli, the metabolic differences between MG1655 and Pdh− were further investigated. An increase in the oxidative pentose phosphate pathway (ox-PPP) flux was observed in response to PDH deficiency. A comparison of the ox-PPP and PDH pathways led to the hypothesis that the role of PDH is the supply of reducing equivalents. The finding that a PDH deficiency lowers the NADH : NAD+ ratio supported the proposed role of PDH. Moreover, the NADH : NAD+ ratio in a strain deficient in both PDH and the ox-PPP (Pdh−Zwf−) was even lower than that observed for Pdh−. Strain Pdh−Zwf− also exhibited a slower transition into the exponential phase and a lower growth rate than Pdh−. Finally, a transhydrogenase-deficient strain grew more slowly than wild-type but did not show the slower transition into the exponential phase characteristic of Pdh− mutants. It is proposed that PDH fulfils two metabolic functions. First, by creating the appropriate internal redox state (i.e. appropriate NADH : NAD+ ratio), PDH ensures the functioning of the glucuronate utilization pathway. Secondly, the NADH generated by PDH can be converted to NADPH by the action of transhydrogenases, thus serving as biosynthetic reducing power in the synthesis of building blocks and macromolecules.

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