scholarly journals Enhancing Bioethanol Production by Deleting Phosphoenolpyruvate Synthase and ADP-Glucose Pyrophosphorylase, and Shunting Tricarboxylic Acid Cycle In Synechocystis Sp. PCC 6803

2021 ◽  
Author(s):  
E-Bin Gao ◽  
Penglin Ye ◽  
Haiyan Qiu ◽  
Junhua Wu ◽  
Huayou Chen
Keyword(s):  
Carbon Dioxide ◽  
Ethanol Production ◽  
Atmospheric Carbon Dioxide ◽  
Metabolic Flux ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Acid Cycle ◽  
Photosynthetic Production ◽  
Engineered Strain ◽  
Pcc 6803

Abstract Background: The outstanding ability of directly assimilating carbon dioxide and sunlight to produce biofuels and chemicals impels photosynthetic cyanobacteria to become attractive organisms for the solution to the global warming crises and the world energy growth. The cyanobacteria-based method for ethanol production has been increasingly regarded as alternatives to food biomass-based fermentation and traditional petroleum-based production. Therefore, we engineered the model cyanobacterium Synechocystis sp. PCC 6803 to synthesize ethanol and optimized the biosynthetic pathways for improving ethanol production under photoautotrophic conditions.Results: In this study, we successfully achieved the photosynthetic production of ethanol from atmospheric carbon dioxide by an engineered mutant Synechocystis sp. PCC 6803 with over-expressing the heterologous genes encoding Zymomonas mobilis pyruvate decarboxylase (PDC) and Escherichia coli NADPH-dependent alcohol dehydrogenase (YqhD). The engineered strain was further optimized by an alternative engineering approach to improve cell growth, and increase the intracellular supply of the precursor pyruvate for ethanol production under photoautotrophic conditions. This approach includes blocking phosphoenolpyruvate synthetic pathway from pyruvate, removing glycogen storage, and shunting carbon metabolic flux of tricarboxylic acid cycle. Through redirecting and optimizing the metabolic carbon flux of Synechocystis, a high ethanol-producing efficiency was achieved (248 mg L-1 day-1) under photoautotrophic conditions with atmospheric CO2 as the sole carbon source. Conclusions: The engineered strain SYN009 (∆slr0301/pdc-yqhD, ∆slr1176/maeB) would become a valuable biosystem for photosynthetic production of ethanol and for expanding our knowledge of exploiting cyanobacteria to produce value chemicals directly from atmospheric CO2.

Structure, Carbon Dioxide Fixation and Metabolism of Stomata

1974 ◽  
Vol 1 (2) ◽  
pp. 221 ◽  
Author(s):  
CJ Pearson ◽  
FL Milthorpe
Keyword(s):  
Carbon Dioxide ◽  
Organic Acid ◽  
Co2 Fixation ◽  
Tricarboxylic Acid Cycle ◽  
Guard Cells ◽  
Tricarboxylic Acid ◽  
Light Illumination ◽  
Acid Cycle ◽  
Free Air ◽  
Positive Correlations

Studies were made of the structure and rates of CO2 fixation of epidermis and of changes in organic metabolites in Commelina cyanea during transition to light and dark in both normal and CO2-free air. Guard cells of C. cyanea and Vicia faba contain numerous highly developed mitochondria and starch-forming chloroplasts (mitochondria: chloroplast ratios of 3 : 1) in comparison to other epidermal cells with few mitochondria and rudimentary plastids without starch. Their rates of photosynthesis per chloroplast appeared to be at least as high as those of the mesophyll, but circumstantial evidence suggested that about half of current photosynthate was respired. The rate of CO2 fixation in the dark was about 0.2–0.4% of that in the light. Illumination caused an increase, and darkening a decrease, of aperture, malate, and organic acid 1% within the epidermis of C. cyanea. Darkening in CO2-free air was accompanied by only slight decreases in aperture and malate. There were close positive correlations between aperture and concentration of malate and between aperture and organic acid 14C. During opening, the rise in organic acid 14C was associated with a decline in amino acid 14C. It is suggested that organic acids may be formed through aspartate and possibly also from sugars and other amino acids entering the tricarboxylic acid cycle. Concentrations of sugars were not related to aperture although they increased on illumination and declined about 2 h after darkening. Polysaccharide concentrations in the epidermis of darkened leaves were similar to those in illuminated leaves.

scholarly journals The redistribution of carbon label by the reactions involved in glycolysis, gluconeogenesis and the tricarboxylic acid cycle in rat liver

1968 ◽  
Vol 110 (2) ◽  
pp. 313-335 ◽  
Author(s):  
D. F. Heath
Keyword(s):  
Carbon Dioxide ◽  
Steady State ◽  
Rat Liver ◽  
Tricarboxylic Acid Cycle ◽  
Specific Radioactivity ◽  
Tricarboxylic Acid ◽  
State Theory ◽  
Variable Rate ◽  
Acid Cycle ◽  
Constant Rate

A scheme is presented that shows how the reactions involved in gluconeogenesis, glycolysis and the tricarboxylic acid cycle are linked in rat liver. Equations are developed that show how label is redistributed in aspartate, glutamate and phosphopyruvate when it is introduced as specifically labelled pyruvate or glucose either at a constant rate (steady-state theory) or at a variable rate (non-steady-state theory). For steady-state theory the fractions of label introduced as specifically labelled pyruvate that are incorporated into glucose and carbon dioxide are also given, and for both theories the specific radioactivities of aspartate and glutamate relative to the specific radioactivity of the substrate. The theories allow for entry of label into the tricarboxylic acid cycle via both oxaloacetate and acetyl-CoA, for 14CO2 fixation and for loss of label from the tricarboxylic acid cycle in glutamate, but not for losses in citrate. They also allow for incomplete symmetrization of label in oxaloacetate due to incomplete equilibration with fumarate both in the extramitochondrial part of the cell and in the mitochondrion on entry of oxaloacetate into the tricarboxylic acid cycle. In the latter case failure both of oxaloacetate to equilibrate with malate and of malate to equilibrate with fumarate are considered.

scholarly journals Systems-Level Metabolic Flux Profiling Elucidates a Complete, Bifurcated Tricarboxylic Acid Cycle in Clostridium acetobutylicum

2011 ◽  
Vol 193 (23) ◽  
pp. 6805-6805
Author(s):  
D. Amador-Noguez ◽  
X.-J. Feng ◽  
J. Fan ◽  
N. Roquet ◽  
H. Rabitz ◽  
...  
Keyword(s):  
Clostridium Acetobutylicum ◽  
Metabolic Flux ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Acid Cycle

Address of the President Sir Howard Florey, at the Anniversary Meeting, 30 November 1961

1961 ◽  
Vol 265 (1320) ◽  
pp. 1-14 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Fatty Acids ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Biological Degradation ◽  
Tissue Slices ◽  
Carbamyl Phosphate ◽  
Acid Cycle ◽  
Main Route ◽  
Carbon Fragment

Award of Medals 1961 The Copley Medal is awarded to Sir Hans Krebs, F.R.S. Sir Hans Krebs has made outstanding contributions to knowledge of the chemical pathways of metabolism. In 1932, with Henseleit, he used tissue slices to demonstrate the synthesis of urea and found that additions of ornithine stimulated the process. Ornithine was regarded as uniting with carbon dioxide and ammonia to give arginine, with citrulline as an intermediate. The enzyme arginase liberated urea and a molecule of ornithine, so that the process could begin again. Subsequent research has shown that the postulated cycle is essentially valid, although more detail has been introduced; carbamyl phosphate, argininosuccinate and adenosine triphosphate have been brought in and aspartic acid has replaced ammonia in the reaction with citrulline. The more complicated version owes much to the fundamental work initiated by Krebs in 1937 on the tricarboxylic acid cycle. This process is now seen as the main route for oxidizing the two-carbon fragment produced in the biological degradation of carbohydrates, fatty acids and arninoacids.

THE METABOLISM OF ACETATE BY WHEAT STEM RUST UREDOSPORES

1964 ◽  
Vol 42 (6) ◽  
pp. 883-888 ◽  
Author(s):  
S. Suryanarayanan ◽  
W. B. McConnell
Keyword(s):  
Carbon Dioxide ◽  
Glutamic Acid ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Water Soluble ◽  
Puccinia Graminis ◽  
Acid Fraction ◽  
Wheat Stem Rust ◽  
Acid Cycle ◽  
Carbon 14

When uredospores of Puccinia graminis var. tritici (race 15B) were incubated at pH 6.2 in phosphate buffer containing either acetate-1-C14or -2-C14, about 12% of the radioactivity was removed from the solution in a period of 3 hours. Respired carbon dioxide contained about 45% and 22% of the carbon-14 taken up as acetate-1-C14and acetate-2-C14, respectively. Incorporation of carbon-14 into spore components was considerably higher with acetate-2-C14than with acetate-1-C14. With either tracer most of the radioactivity in water-soluble spore materials was accounted for in amino acids and neutral substances. Glutamic acid was particularly radioactive and accounted for about 40% of the radioactivity in the amino acid fraction. Incorporation of carbon-14 into the glutamic acid skeleton was consistent with the view that both the tricarboxylic acid cycle and the glyoxalate cycle were functioning.

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