The Eastern and Western branches of the Wood/Ljungdahl pathway: how the East and West were won

Ragsdale, Stephen W.

doi:10.1002/biof.5520060102

Cited by 85 publications

(65 citation statements)

References 73 publications

(40 reference statements)

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“…The reductive acetyl-CoA pathway is illustrated in Figure 1 and is made up of carbonyl (sometimes referred to as "Eastern" [90]) and methyl (or "Western") branches. Ragsdale provides an excellent history of the elucidation of the different branches and a background to the biochemistry and enzymology of the pathway [90].…”

Section: Biochemistry Of Gas Fermentation: the Reductive Acetyl-coa mentioning

confidence: 99%

“…Ragsdale provides an excellent history of the elucidation of the different branches and a background to the biochemistry and enzymology of the pathway [90]. [54,85,[91][92][93].…”

Section: Biochemistry Of Gas Fermentation: the Reductive Acetyl-coa mentioning

confidence: 99%

“…The Western (or carbonyl) branch is unique to anaerobic microorganisms [90]. CO can either be used directly, or generated from CO 2 , and serves as the carbonyl group for acetyl-CoA synthesis.…”

Section: Biochemistry Of Gas Fermentation: the Reductive Acetyl-coa mentioning

confidence: 99%

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Commercial Biomass Syngas Fermentation

2012

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Abstract:The use of gas fermentation for the production of low carbon biofuels such as ethanol or butanol from lignocellulosic biomass is an area currently undergoing intensive research and development, with the first commercial units expected to commence operation in the near future. In this process, biomass is first converted into carbon monoxide (CO) and hydrogen (H 2 )-rich synthesis gas (syngas) via gasification, and subsequently fermented to hydrocarbons by acetogenic bacteria. Several studies have been performed over the last few years to optimise both biomass gasification and syngas fermentation with significant progress being reported in both areas. While challenges associated with the scale-up and operation of this novel process remain, this strategy offers numerous advantages compared with established fermentation and purely thermochemical approaches to biofuel production in terms of feedstock flexibility and production cost. In recent times, metabolic engineering and synthetic biology techniques have been applied to gas fermenting organisms, paving the way for gases to be used as the feedstock for the commercial production of increasingly energy dense fuels and more valuable chemicals.

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Section: Biochemistry Of Gas Fermentation: the Reductive Acetyl-coa mentioning

confidence: 99%

“…Ragsdale provides an excellent history of the elucidation of the different branches and a background to the biochemistry and enzymology of the pathway [90]. [54,85,[91][92][93].…”

Section: Biochemistry Of Gas Fermentation: the Reductive Acetyl-coa mentioning

confidence: 99%

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Commercial Biomass Syngas Fermentation

2012

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“…The reducing equivalents are funneled to the CO 2 produced, which is converted to acetate in the Wood-Ljungdahl pathway (32,33,40,41) according to:…”

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confidence: 99%

Dissection of the Caffeate Respiratory Chain in the Acetogen Acetobacterium woodii : Identification of an Rnf-Type NADH Dehydrogenase as a Potential Coupling Site

et al. 2007

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The anaerobic acetogenic bacterium Acetobacterium woodii couples caffeate reduction with electrons derived from hydrogen to the synthesis of ATP by a chemiosmotic mechanism with sodium ions as coupling ions, a process referred to as caffeate respiration. We addressed the nature of the hitherto unknown enzymatic activities involved in this process and their cellular localization. Cell extract of A. woodii catalyzes H 2 -dependent caffeate reduction. This reaction is strictly ATP dependent but can be activated also by acetyl coenzyme A (CoA), indicating that there is formation of caffeyl-CoA prior to reduction. Two-dimensional gel electrophoresis revealed proteins present only in caffeate-grown cells. Two proteins were identified by electrospray ionization-mass spectrometry/mass spectrometry, and the encoding genes were cloned. These proteins are very similar to subunits ␣ (EtfA) and ␤ (EtfB) of electron transfer flavoproteins present in various anaerobic bacteria. Western blot analysis demonstrated that they are induced by caffeate and localized in the cytoplasm. Etf proteins are known electron carriers that shuttle electrons from NADH to different acceptors. Indeed, NADH was used as an electron donor for cytosolic caffeate reduction. Since the hydrogenase was soluble and used ferredoxin as an electron acceptor, the missing link was a ferredoxin:NAD ؉ oxidoreductase. This activity could be determined and, interestingly, was membrane bound. A search for genes that could encode this activity revealed DNA fragments encoding subunits C and D of a membrane-bound Rnf-type NADH dehydrogenase that is a potential Na ؉ pump. These data suggest the following electron transport chain: H 2 3 ferredoxin 3 NAD ؉ 3 Etf 3 caffeyl-CoA reductase. They also imply that the sodium motive step in the chain is the ferredoxin-dependent NAD ؉ reduction catalyzed by Rnf.

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“…Conversion of CO2 to acetate is a reduction process. However, acetate can be converted back to CO2 through oxidation (Ragsdale, 1997). Acetogens conserve energy by reduction of CO, and/or CO2, and H2 to acetate.…”

Section: Biocatalystsmentioning

confidence: 99%