Clostridium ljungdahlii sp. nov., an Acetogenic Species in Clostridial rRNA Homology Group I

Tanner, Ralph S.; Miller, Letrisa M.; Yang, Decheng

doi:10.1099/00207713-43-2-232

Cited by 260 publications

(165 citation statements)

References 23 publications

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“…First, we used the acetogen M. thermoacetica as a model organism because of its very high autotrophic flux to acetyl-CoA, which naturally produces acetate at very high rates and almost theoretical yields via the canonical Wood-Ljungdahl pathway. Additionally, the high temperature of operation (T opt 60°C) of this thermophilic organism makes it of industrial interest as it would require less cooling of syngas before feeding the bioreactor (12) compared with the other model acetogens, Clostridium ljungdahlii (T opt 37°C) (13) and Acetobacterium woodii (T opt 30°C) (14). Our prior work with M. thermoacetica (7) provided the basis of acetic acid production at high rates relevant to this study.…”

Section: Discussionmentioning

confidence: 99%

Integrated bioprocess for conversion of gaseous substrates to liquids

Chakraborty

Kumar

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

161

130

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In the quest for inexpensive feedstocks for the cost-effective production of liquid fuels, we have examined gaseous substrates that could be made available at low cost and sufficiently large scale for industrial fuel production. Here we introduce a new bioconversion scheme that effectively converts syngas, generated from gasification of coal, natural gas, or biomass, into lipids that can be used for biodiesel production. We present an integrated conversion method comprising a two-stage system. In the first stage, an anaerobic bioreactor converts mixtures of gases of CO 2 and CO or H 2 to acetic acid, using the anaerobic acetogen Moorella thermoacetica. The acetic acid product is fed as a substrate to a second bioreactor, where it is converted aerobically into lipids by an engineered oleaginous yeast, Yarrowia lipolytica. We first describe the process carried out in each reactor and then present an integrated system that produces microbial oil, using synthesis gas as input. The integrated continuous bench-scale reactor system produced 18 g/L of C16-C18 triacylglycerides directly from synthesis gas, with an overall productivity of 0.19 g·L −1 ·h −1 and a lipid content of 36%. Although suboptimal relative to the performance of the individual reactor components, the presented integrated system demonstrates the feasibility of substantial net fixation of carbon dioxide and conversion of gaseous feedstocks to lipids for biodiesel production. The system can be further optimized to approach the performance of its individual units so that it can be used for the economical conversion of waste gases from steel mills to valuable liquid fuels for transportation.two-stage bioprocess | lipid production | microbial fermentation | gas-to-liquid fuel | CO 2 fixation C oncerns over diminishing oil reserves and climate-changing greenhouse gas emissions have led to calls for clean and renewable liquid fuels (1). One promising direction has been the production of microbial oil from carbohydrate feedstocks. This oil can be readily converted to biodiesel and recently there has been significant progress in the engineering of oleaginous microbes for the production of lipids from sugars (2-5). A major problem with this approach has been the relatively high sugar feedstock cost. Alternatively, less costly industrial gases containing CO 2 with reducing agents, such as CO or H 2 , have been investigated. In one application, anaerobic Clostridia have been used to convert synthesis gas to ethanol (6), albeit at low concentration requiring high separation cost. Here we present an alternative gas-to-lipids approach that overcomes the drawbacks of previous schemes.We have shown previously that acetate in excess of 30 g/L can be produced from mixtures of CO 2 and CO/H 2 , using an evolved strain of the acetogen Moorella thermoacetica, with a substantial productivity of 0.55 g·L −1 ·h −1 and yield of 92% (7). We also have demonstrated that the engineering of the oleaginous yeast Yarrowia lipolytica can yield biocatalysts that can produce lipids from...

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Section: Discussionmentioning

confidence: 99%

Integrated bioprocess for conversion of gaseous substrates to liquids

Chakraborty

Kumar

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

161

130

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“…Tanner et al. showed the generation of acetate by growing Clostridium lungdahlii with, for example, CO, H 2 , or CO 2 14. Sakai et al.…”

Section: Introductionmentioning

confidence: 99%

Bio‐Electrocatalytic Application of Microorganisms for Carbon Dioxide Reduction to Methane

et al. 2016

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We present a study on a microbial electrolysis cell with methanogenic microorganisms adapted to reduce CO2 to CH4 with the direct injection of electrons and without the artificial addition of H2 or an additional carbon source except gaseous CO2. This is a new approach in comparison to previous work in which both bicarbonate and gaseous CO2 served as the carbon source. The methanogens used are known to perform well in anaerobic reactors and metabolize H2 and CO2 to CH4 and water. This study shows the biofilm formation of those microorganisms on a carbon felt electrode and the long‐term performance for CO2 reduction to CH4 using direct electrochemical reduction. CO2 reduction is performed simply by electron uptake with gaseous CO2 as the sole carbon source in a defined medium. This “electrometabolism” in such microbial electrolysis cells depends strongly on the potential applied as well as on the environmental conditions. We investigated the performance using different adaption mechanisms and a constant potential of −700 mV vs. Ag/AgCl for CH4 generation at 30–35 °C. The experiments were performed by using two‐compartment electrochemical cells. Production rates with Faradaic efficiencies of around 22 % were observed.

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“…The first acetogen reported to produce ethanol from syngas was Clostridium ljungdahlii [25,26]. Shortly thereafter, Butyribacterium methylotrophicum was reported to produce butanol and ethanol from CO [27].…”

Section: Species and Habitatmentioning

confidence: 99%

Syngas Fermentation: A Microbial Conversion Process of Gaseous Substrates to Various Products

2017

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Biomass and other carbonaceous materials can be gasified to produce syngas with high concentrations of CO and H 2 . Feedstock materials include wood, dedicated energy crops, grain wastes, manufacturing or municipal wastes, natural gas, petroleum and chemical wastes, lignin, coal and tires. Syngas fermentation converts CO and H 2 to alcohols and organic acids and uses concepts applicable in fermentation of gas phase substrates. The growth of chemoautotrophic microbes produces a wide range of chemicals from the enzyme platform of native organisms. In this review paper, the Wood-Ljungdahl biochemical pathway used by chemoautotrophs is described including balanced reactions, reaction sites physically located within the cell and cell mechanisms for energy conservation that govern production. Important concepts discussed include gas solubility, mass transfer, thermodynamics of enzyme-catalyzed reactions, electrochemistry and cellular electron carriers and fermentation kinetics. Potential applications of these concepts include acid and alcohol production, hydrogen generation and conversion of methane to liquids or hydrogen.

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Clostridium ljungdahlii sp. nov., an Acetogenic Species in Clostridial rRNA Homology Group I

Cited by 260 publications

References 23 publications

Integrated bioprocess for conversion of gaseous substrates to liquids

Integrated bioprocess for conversion of gaseous substrates to liquids

Bio‐Electrocatalytic Application of Microorganisms for Carbon Dioxide Reduction to Methane

Syngas Fermentation: A Microbial Conversion Process of Gaseous Substrates to Various Products

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