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Cited by 485Microbial Metabolic Engineering and BioproductionBiofuel production and bioconversionAnaerobic Digestion and Biogas Production

Gas Fermentation—A Flexible Platform for Commercial Scale Production of Low-Carbon-Fuels and Chemicals from Waste and Renewable Feedstocks

Open access
Liew, FungMin, Martin, Michael E., Tappel, Ryan C., Heijstra, Björn D., Mihalcea, Christophe, Köpke, Michael·2016·Frontiers in Microbiology
DOI 10.3389/fmicb.2016.00694PMC PMC4862988
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Abstract

There is an immediate need to drastically reduce the emissions associated with global fossil fuel consumption in order to limit climate change. However, carbon-based materials, chemicals, and transportation fuels are predominantly made from fossil sources and currently there is no alternative source available to adequately displace them. Gas-fermenting microorganisms that fix carbon dioxide (CO2) and carbon monoxide (CO) can break this dependence as they are capable of converting gaseous carbon to fuels and chemicals. As such, the technology can utilize a wide range of feedstocks including gasified organic matter of any sort (e.g., municipal solid waste, industrial waste, biomass, and agricultural waste residues) or industrial off-gases (e.g., from steel mills or processing plants). Gas fermentation has matured to the point that large-scale production of ethanol from gas has been demonstrated by two companies. This review gives an overview of the gas fermentation process, focusing specifically on anaerobic acetogens. Applications of synthetic biology and coupling gas fermentation to additional processes are discussed in detail. Both of these strategies, demonstrated at bench-scale, have abundant potential to rapidly expand the commercial product spectrum of gas fermentation and further improve efficiencies and yields.

AI snapshot

Written from the paper’s full text.

TL;DR

This review describes gas fermentation as a flexible platform in which anaerobic acetogens use the Wood-Ljungdahl pathway to convert CO/CO₂/H₂-rich syngas and industrial off-gases into low-carbon fuels and chemicals. It highlights commercial ethanol production, synthetic-biology expansion of product spectra, and coupled biological/chemical upgrading, while noting remaining technical and economic challenges.

Key findings

  • Gas fermentation can use diverse feedstocks—gasified municipal solid waste, industrial waste, biomass, agricultural residues, and industrial off-gases such as steel mill gas—and offers advantages over Fischer-Tropsch, including operation at 37 °C and atmospheric pressure, flexible H₂:CO ratios, tolerance to sulfur/chlorine/tars, and higher product selectivity.
  • Commercial-scale ethanol from gas has been demonstrated: INEOS Bio built an 8 Mgy semi-commercial facility in Vero Beach, FL, generating 6 mW of electrical power; LanzaTech operated two 0.1 Mgy pre-commercial plants in China, with planned China Steel (17 Mgy, scaling to 34 Mgy) and ArcelorMittal (9.8 Mgy) projects, and potential European capacity of around 104 Mgy displacing 1.6 million barrels of gasoline on a BTU basis.
  • Life-cycle assessment estimates 67% GHG reduction using blast oxygen furnace off-gas from steel manufacturing and 88–98% GHG reduction using gasified biomass versus conventional fossil gasoline, with 20–40% of feed-gas carbon converted into ethanol in both scenarios.
  • Synthetic biology and coupled processes expand the product spectrum: engineered acetogens produced butanol up to 25.7 mM, acetone up to 871 mg/L, and continuous isopropanol at 700 mg/L/d; coupled bioprocesses produced 18 g/L triacylglycerides at 36% lipid content and enabled chain elongation, alcohol reduction, alcohol-to-jet fuel, and butadiene precursors.

Methods

  • Design: narrative review, not primary experimental research; it covers the gas fermentation process, acetogen biology and the Wood-Ljungdahl pathway, synthetic-biology tools, metabolic engineering examples, and coupled biological/chemical processes.
  • Data or sample: published literature, patents, company reports, and life-cycle assessment studies; the paper includes Table 1 on acetogen species and Table 2 on genetically modified acetogens.
  • Main analysis: qualitative synthesis of existing evidence, with no new experiments, systematic review protocol, or meta-analysis reported.

Limitations

  • Stated in the text: gas fermentation faces low solubility of CO, H₂, and CO₂ and mass-transfer limitations; impurities such as HCN, NOx, acetylene, O₂, and sulfur compounds can inhibit key enzymes; reactor design and scale-up remain challenging; and acetogens still have limited genetic tools, parts, and molecular characterization.
  • Stated in the text: microbial electrosynthesis and photosensitized acetogen systems are early-stage and require biological and engineering optimization; coupled processes can face issues such as methanogen contamination and difficulty maintaining mixed-culture population dynamics.
  • Evident from the text: as a review, it presents no original data; some commercial and strain details rely on patents and company reports rather than peer-reviewed studies, and the authors disclose LanzaTech’s commercial interest in gas fermentation.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.3389/fmicb.2016.00694

Cites

299 of 299 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 244 cited sources checked · 0 supported · 0 flagged

  • Interpretationnone given

    Gas-fermenting microorganisms that fix CO2 and CO can convert gaseous carbon to fuels and chemicals.

    “Gas-fermenting microorganisms that fix carbon dioxide (CO2) and carbon monoxide (CO) can break this dependence as they are capable of converting gaseous carbon to fuels and chemicals.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: No alternative source is currently available to adequately displace fossil carbon-based materials, chemicals, and transportation fuels.
  • Premisenone given

    Gas fermentation can utilize a wide range of feedstocks including gasified organic matter (e.g., municipal solid waste, industrial waste, biomass, agricultural waste residues) or industrial off-gases (e.g., from steel mills or processing plants).

    “As such, the technology can utilize a wide range of feedstocks including gasified organic matter of any sort (e.g., municipal solid waste, industrial waste, biomass, and agricultural waste residues) or industrial off-gases (e.g., from steel mills or processing plants).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites National Energy Technology Laboratory, 2014

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    • cites Clarke Energy, 2015

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    • cites Oakley et al., 2011

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  • Interpretationreasoning

    Use of biomass in its entirety as a feedstock is a key advantage inherent to gas fermentation compared to sugar and cellulosic fermentation to produce low-carbon fuels.

    “The use of the biomass in its entirety as a feedstock is a key advantage inherent to gas fermentation compared to sugar and cellulosic fermentation to produce low-carbon fuels.”
    Quote in the paperSubstantial claim
  • Premisecitation

    The ratio and partial pressures of CO, H2, and CO2 influence the product yield, production rate, and selectivity of a gas fermentation.

    “Next to gas availability determined by reactor kLa, the ratio and partial pressures of CO, H2, and CO2 also influence the product yield, production rate, and selectivity of a gas fermentation (Genthner and Bryant, 1982; Vega et al., 1988; Klasson et al., 1991; Gaddy and Chen, 1998; Hurst and Lewis, 2010; Kantzow et al., 2015).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Genthner and Bryant, 1982

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    • cites Vega et al., 1988 source

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    • cites Klasson et al., 1991 source

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  • Interpretationnone given

    The high power per unit volume required to drive the stirrer renders commercial scale operation of CSTRs economically challenging.

    “However, the high power per unit volume required to drive the stirrer renders commercial scale operation economically challenging.”
    Quote in the paperSubstantial claim
  • Classified as probably not a substantial claim. 49
  • May combine two claims. 59

  • Probably not a substantial claim: may not pass S4 (based).

    Findingnone given

    Large-scale production of ethanol from gas has been demonstrated by two companies.

    “Gas fermentation has matured to the point that large-scale production of ethanol from gas has been demonstrated by two companies.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    FTP employs high temperature (150-350 °C), elevated pressures (30 bar), and heterogeneous catalysts such as cobalt, ruthenium, and iron.

    “First developed in 1925, FTP employs high temperature (150–350 °C), elevated pressures (30 bar), and heterogeneous catalysts such as cobalt, ruthenium, and iron (De Klerk et al., 2013).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites De Klerk et al., 2013

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  • Probably not a substantial claim: may not pass S2 (checkable).

    Premisecitation

    There is an immediate need to drastically reduce emissions associated with global fossil fuel consumption in order to limit climate change.

    “There is an immediate need to drastically reduce the emissions associated with global fossil fuel consumption in order to limit climate change.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites United Nations, 2015

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    Premisecitation

    Lignin, which can account for up to 40% of plant biomass, does not get converted in cellulosic ethanol production.

    “Even with the extensive biomass processing required to produce cellulosic ethanol, the lignin, which can account for up to 40% of plant biomass does not get converted (Sun and Cheng, 2002; Abubackar et al., 2011).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Sun and Cheng, 2002 source

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    • cites Abubackar et al., 2011 source

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  • May combine two claims.

    Interpretationreasoning

    Conversion of biomass to syngas allows utilization of nearly all available carbon contained within the biomass, including lignin, and bypasses the expense and inefficiencies of biomass pretreatment.

    “Conversion of biomass to syngas allows for utilization of nearly all the available carbon contained within the biomass, including the otherwise inaccessible lignin fraction, and bypasses the expense and inefficiencies of biomass pretreatment.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    Gas fermentation takes place at 37 °C and atmospheric pressure, which presents significant energy and cost savings relative to FTP.

    “In comparison, gas fermentation takes place at 37 °C and atmospheric pressure, which presents significant energy and cost savings relative to FTP.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    INEOS Bio has identified and reported HCN as a key contaminant that needs treatment from operation of their Vero Beach plant.

    “INEOS Bio has identified and reported HCN as a key contaminant that needs treatment from operation of their Vero Beach plant (INEOS Bio, 2014).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites INEOS Bio, 2014

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    Premisecitation

    In a cradle-to-grave LCA by Handler et al. (2016), ethanol from gas fermentation in the USA is estimated to result in 67% GHG reduction using blast oxygen furnace off-gas from steel manufacturing and 88-98% GHG reduction utilizing gasified biomass, compared to conventional fossil gasoline.

    “In a recently published cradle-to-grave LCA by Handler et al. (2016), the production of ethanol from gas fermentation in the USA is estimated to result in 67% Greenhouse gas (GHG) reduction (using blast oxygen furnace off-gas from steel manufacturing) and 88–98% GHG reduction (utilizing gasified biomass), when compared to conventional fossil gasoline.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Handler et al., 2016 source

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    Premisecitation

    Many contaminants including BTEX are lipophilic compounds that readily dissolve in the cytoplasmic membrane and affect membrane fluidity.

    “Many contaminants including BTEX are lipophilic compounds that readily dissolve in the cytoplasmic membrane affecting membrane fluidity (Sikkema et al., 1995).”
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    • cites Sikkema et al., 1995 source

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    Premisecitation

    Removal technologies for aromatics from gas are commercially available, and techniques to improve efficiency are still being reported.

    “Removal technologies for aromatics from gas are commercially available, and techniques to improve efficiency are still being reported (Ye and Ariya, 2015).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Ye and Ariya, 2015

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  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    Bioreactor design, agitation, gas composition and supply rate, pH, temperature, headspace pressure, oxidation-reduction potential, nutrients, and foaming can all contribute to improving selectivity and yield of the desired product.

    “Bioreactor design, agitation, gas composition and supply rate, pH, temperature, headspace pressure, oxidation-reduction potential (ORP), nutrients, and amount of foaming in the bioreactor all can contribute to the goal of improving selectivity and yield of the desired product (e.g., ethanol and butanol) as discussed below.”
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    Premisenone given

    Polycyclic aromatics do not readily dissolve in aqueous phase but can accumulate and negatively affect operations.

    “Although polycyclic aromatics do not readily dissolve in aqueous phase, they can accumulate and negatively affect operations.”
    Quote in the paperNot a substantial claim

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    Premisecitation

    C. ljungdahlii has been shown to detoxify O2 and ROS, likely via rubrerythrin and hydrogen peroxidases.

    “C. ljungdahlii has been shown to detoxify O2 and ROS (likely via rubrerythrin and hydrogen peroxidases) and ethanol formation could actually be stimulated by exposure to O2 (likely due to changes in AOR activity and co-factor metabolism) (Whitham et al., 2015).”
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    • cites Whitham et al., 2015 source

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    Premisecitation

    O2 can be removed by passing the gas over various metal catalysts such as Pt, Pd, and Cu.

    “O2 can be removed by passing the gas over various metal catalysts such as Pt, Pd, and Cu (Yan et al., 2013).”
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    • cites Yan et al., 2013 source

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    Premisecitation

    Using biological co-culture for O2 removal has been described.

    “Using biological co-culture for O2 removal has also been described (Wu et al., 2016).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Wu et al., 2016

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  • May combine two claims.

    Premisecitation

    The Wood-Ljungdahl pathway is the only linear CO2 fixation pathway to acetyl-CoA and is considered the most efficient non-photosynthetic carbon fixation mechanism.

    “The WLP, also known as the reductive acetyl-CoA pathway, is the only linear CO2 fixation pathway to acetyl-CoA (Drake et al., 2008) and considered as the most efficient non-photosynthetic carbon fixation mechanism (Fast and Papoutsakis, 2012).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Drake et al., 2008 source

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    • cites Fast and Papoutsakis, 2012

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  • May combine two claims.

    Premisenone given

    LanzaTech has successfully operated two 0.1 Mgy pre-commercial plants in China with BaoSteel and Shougang Steel, both using steel mill off-gases as substrates.

    “LanzaTech has successfully operated two 0.1 Mgy pre-commercial plants in different locations in China with two steel companies, BaoSteel and Shougang Steel. Both plants, the first at one of BaoSteel's mills in Shanghai in 2012 and the second at a Shougang steel mill near Beijing in 2013, used steel mill off-gases as substrates for gas fermentation.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    At steady-state, the gasification process is self-sustaining, although a small amount of energy input is required to heat the incoming feedstock at the beginning.

    “Although a small amount of energy input is required to heat the incoming feedstock to gasification temperature at the beginning of the process, at steady-state the process is self-sustaining (Handler et al., 2016).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Handler et al., 2016 source

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    Premisecitation

    Continuous stirred tank reactors offer excellent mixing and homogenous distribution of gas substrates to the microorganisms and are most commonly employed at laboratory scale.

    “Continuous stirred tank reactors (CSTR) offer excellent mixing and homogenous distribution of gas substrates to the microorganisms and are most commonly employed at laboratory scale (Ungerman and Heindel, 2007).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Ungerman and Heindel, 2007

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  • May combine two claims.

    Interpretationreasoning

    Acetogens are particularly attractive for commercialized gas fermentation due to their native ability to synthesize useful products such as ethanol, butanol and 2,3-butanediol and the fact that they are anaerobes.

    “Acetogens are particularly attractive for commercialized gas fermentation due to their native ability to synthesize useful products such as ethanol, butanol and 2,3-butanediol and the fact that they are anaerobes.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    INEOS Bio built an 8 million gallon per year semi-commercial facility in Vero Beach, FL, commissioned in 2012, using lignocellulosic biomass and MSW, and announced successful production of ethanol in July 2013.

    “INEOS Bio built an 8 million gallon per year (Mgy) semi-commercial facility in Vero Beach, FL as a joint venture with New Planet Energy Holdings, LLC. Commissioned in 2012, the facility uses lignocellulosic biomass and MSW for generating gas fermentation substrates and generates 6 mW of electrical power. In July 2013, the company announced successful production of ethanol in its facility (Schill,”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Schill, 2013

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  • May combine two claims.

    Interpretationnone given

    Increasing flow of the substrate gas can lead to decreased yields of product per mole of carbon fed to the reactor, making reactor design and operation crucial.

    “Increasing flow of the substrate gas can lead to decreased yields of product per mole of carbon fed to the reactor, making reactor design and operation crucial.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Whole genome sequences have been elucidated for a range of acetogens including C. autoethanogenum, C. ljungdahlii, C. aceticum, M. thermoacetica, A. woodii, and E. limosum.

    “These include elucidation of whole genome sequences for a range of acetogens including C. autoethanogenum (Brown et al., 2014; Humphreys et al., 2015; Utturkar et al., 2015), C. ljungdahlii (Köpke et al., 2010), C. aceticum (Poehlein et al., 2015), M. thermoacetica (Pierce et al., 2008), A. woodii (Poehlein et al., 2012), and E. limosum (Roh et al., 2011);”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Brown et al., 2014 source

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    • cites Köpke et al., 2010 source

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    • cites Poehlein et al., 2015 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Liquid-liquid extraction is an option for removing acetate from the fermentation broth of gas-fermenting acetogens.

    “Liquid-liquid extraction is also an option for removing acetate from the fermentation broth of gas-fermenting acetogens (Jipa et al., 2009).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Jipa et al., 2009

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  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    E. coli and yeast are well studied and characterized on molecular and systems level with decades of intensive research by thousands of research groups.

    “E. coli and yeast are well studied and characterized on molecular and systems level with decades of intensive research by thousands of research groups.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Sophisticated genetic toolkits allow precise and rapid design and automated high-throughput strain engineering and prototyping in E. coli and yeast.

    “This has led to the development of sophisticated genetic toolkits that allow precise and rapid design (Temme et al., 2012b) and automated high-throughput strain engineering and prototyping (Gardner, 2013; Burk and Van Dien, 2016).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Temme et al., 2012b

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    • cites Gardner, 2013 source

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    • cites Burk and Van Dien, 2016

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    Premisecitation

    Based on the C. ljungdahlii genome-scale model, spatiotemporal modeling of gas fermentation in a bubble column was performed recently.

    “Based on the C. ljungdahlii GEM, spatiotemporal modeling of gas fermentation in a bubble column was performed recently (Chen et al., 2015, 2016).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Chen et al., 2015 source

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    • cites Chen et al., 2016 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    B vitamins and metals such as zinc, nickel, selenium, and tungsten, required as cofactors for certain enzymes in central metabolism, are required for bacterial growth and affect product selectivity.

    “B vitamins and metals such as zinc, nickel, selenium, and tungsten, required as cofactors for certain enzymes in the central metabolism, are required for bacterial growth and affect product selectivity.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Similar genome-scale models also exist for C. ljungdahlii and M. thermoacetica.

    “Similar models also exist for C. ljungdahlii (Nagarajan et al., 2013) and M. thermoacetica (Islam et al., 2015).”
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    • cites Nagarajan et al., 2013 source

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    • cites Islam et al., 2015 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisereasoning

    The establishment of an efficient protocol to introduce foreign DNA into a microbial host is frequently one of the most challenging steps in any genetic engineering endeavor.

    “The establishment of an efficient protocol to introduce foreign DNA into a microbial host is frequently one of the most challenging steps in any genetic engineering endeavor.”
    Quote in the paperNot a substantial claim

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    Premisecitation

    Acetogens have been viewed as genetically inaccessible until a few years ago and are still considered difficult to work with.

    “In contrast, acetogens have been viewed as genetically inaccessible until a few years ago and are still considered difficult to work with (Burk and Van Dien, 2016).”
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    • cites Burk and Van Dien, 2016

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationreasoning

    Although advancements in E. coli and yeast cannot be directly transferred to acetogens, similar principles may be applied.

    “Although these advancements cannot be directly transferred to acetogens, similar principles may be applied.”
    Quote in the paperNot a substantial claim

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    Premisecitation

    Distillation systems are common to separate lower boiling point products such as ethanol and acetone, but this is considered energy-intensive and therefore potentially expensive, especially for low concentration products and products with high boiling points.

    “Distillation systems are common to separate lower boiling point products such as ethanol (Handler et al., 2016) and acetone, but this is considered energy-intensive (and therefore potentially expensive), especially for low concentration products and products with high boiling points (e.g., butanediol).”
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    • cites Handler et al., 2016 source

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    Interpretationcitation

    Over the last 5 years, great strides have been made that have contributed to the understanding of acetogens on a molecular and systems level.

    “However, over the last 5 years, great strides have been made that have contributed to the understanding of acetogens on a molecular and systems level.”
    Quote in the paperNot a substantial claim

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    Premisereasoning

    Most genetic tool work has focused on acetogenic clostridia, partly due to their properties as commercial production strains and partly due to pre-existing tools for non-acetogenic clostridia.

    “Most of the work has focused on acetogenic clostridia, in part due to their properties as commercial production strains for gas-fermentation (see Section Acetogens and Wood-Ljungdahl Pathway) but also due to the presence of pre-existing tools for non-acetogenic clostridia studied for medical purposes (e.g., Clostridium difficile and Clostridium botulinum), or exploited for acetone/isopropanol-but”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Transcriptomics analyses have been performed for C. autoethanogenum and C. ljungdahlii.

    “and transcriptomics analyses of C. autoethanogenum (Mock et al., 2015; Marcellin et al., 2016) and C. ljungdahlii (Nagarajan et al., 2013; Tan et al., 2013; Whitham et al., 2015).”
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    • cites Mock et al., 2015 source

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    • cites Marcellin et al., 2016 source

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    • cites Nagarajan et al., 2013 source

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    Interpretationreasoning

    The product profile reflects the organism's requirement to maintain an internal energy balance that favors growth and is directly influenced by the gas composition and availability.

    “This product profile reflects the organism's requirement to maintain an internal energy balance that favors growth and is directly influenced by the gas composition and availability.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Other technologies to separate fermentation products from broth include liquid-liquid extraction, gas stripping, adsorption, perstraction, pervaporation, and vacuum distillation.

    “Other technologies to separate fermentation products from broth include liquid-liquid extraction, gas stripping, adsorption, perstraction, pervaporation, and vacuum distillation (Huang et al., 2008; Frolkova and Raeva, 2010; Liew et al., 2013; Molitor et al., 2016)”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Huang et al., 2008 source

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    • cites Frolkova and Raeva, 2010

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    • cites Liew et al., 2013

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Some well-studied non-acetogenic clostridia, such as C. acetobutylicum, C. beijerinckii, C. difficile, and C. botulinum, have transformation protocols that were established as early as 1988.

    “Some of the well-studied, non-acetogenic clostridia, such as the ABE model organisms C. acetobutylicum (Mermelstein et al., 1992) and C. beijerinckii (Oultram et al., 1988), and important pathogens, such as C. difficile (Ackermann et al., 2001) and C. botulinum (Zhou and Johnson, 1993), have transformation protocols that were established as early as 1988.”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Mermelstein et al., 1992 source

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    • cites Oultram et al., 1988 source

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    • cites Ackermann et al., 2001 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisenone given

    Each separation technology has its own benefits and drawbacks, including potential fouling of membranes for perstraction and pervaporation and substrate removal for gas stripping and liquid-liquid extraction.

    “Each of these separation technologies has their own benefits and drawbacks, including potential fouling of membranes (perstraction and pervaporation) and substrate removal (gas stripping and liquid-liquid extraction).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    Cultivation under an industrial setting, the limited number of genetic tools, potential energetic constraints, and lack of characterization on genetic and molecular levels are key challenges for successful development of genetically engineered gas-fermenting platforms.

    “More specifically, cultivation under an industrial setting, the limited number of genetic tools (Burk and Van Dien, 2016), potential energetic constraints (Bertsch and Müller, 2015), and lack of characterization on genetic and molecular levels are considered key challenges to address for successful development of genetically engineered gas-fermenting platforms.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Burk and Van Dien, 2016

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    • cites Bertsch and Müller, 2015

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    Premisecitation

    The ClosTron technique is reproducible and has been widely applied to various clostridia including acetogen C. autoethanogenum.

    “Thanks to these properties, this technique is reproducible and has been widely applied to various clostridia (Heap et al., 2007, 2010; Camiade et al., 2010) including acetogen C. autoethanogenum (Mock et al., 2015; Marcellin et al., 2016).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Heap et al., 2007 source

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    • cites Heap et al., 2010 source

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    • cites Camiade et al., 2010 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Marker excision can be achieved using FLP recombinase or the Cre-lox system.

    “This can either be achieved using above mentioned FLP recombinase (Lee et al., 2016) or using the Cre-lox system (Sauer, 1987).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Lee et al., 2016 source

      Not checked in the free run.

    • cites Sauer, 1987 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    For stable genome insertion, homologous recombination is typically used.

    “For stable genome insertion, homologous recombination is typically used.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationnone given

    The ClosTron technique should be amendable to other non-clostridia mesophilic acetogens such as A. woodii but may not be applicable for some thermophilic organisms such as M. thermoacetica.

    “The technique should also be amendable to other non-clostridia mesophilic acetogens such as A. woodii but may not be applicable for some of the thermophilic organisms such as M. thermoacetica.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisereasoning

    Electroporation is the most commonly explored method of transformation in microorganisms due to its technical simplicity, higher reproducibility, scalability, greater transformation efficiency, and independence from donor species.

    “Due to its technical simplicity, higher reproducibility, scalability, greater transformation efficiency, and independence from donor species, electroporation is the most commonly explored method of transformation in microorganisms.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Heap et al. adapted mobile group II introns for use in a wide spectrum of clostridia, and the technology is termed ClosTron.

    “Heap et al. (2007) adapted such mobile elements for use in a wide spectrum of clostridia, and the technology is termed “ClosTron.””
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Heap et al., 2007 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    C. difficile was recently found to harbor the Wood-Ljungdahl pathway and is able to grow autotrophically on H2 and CO2.

    “It is intriguing that C. difficile was recently found to also harbor the WLP and is able to grow autotrophically on H2 and CO2 (Köpke et al., 2013b).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Köpke et al., 2013b

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The ClosTron technique was further optimized to generate multiple insertional mutations in the same strain by recycling of marker through the actions of FLP recombinase, and delivery of cargo sequence of up to 1 kb was successfully demonstrated in C. sporogenes.

    “This technique was further optimized to generate multiple insertional mutations in the same strain by recycling of marker through the actions of FLP recombinase, and the delivery of cargo sequence of up to 1 kb was successfully demonstrated in C. sporogenes (Heap et al., 2010).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Heap et al., 2010 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Modular Clostridium-E. coli shuttle plasmids developed by Heap et al. contain customizable components such as different Gram-positive and Gram-negative replicons and the traJ gene, and have been adopted for genetic manipulation work in several acetogens.

    “The modular Clostridium-E. coli shuttle plasmids developed by Heap et al. (2009) contain customizable components such as different Gram-positive and Gram-negative replicons as well as the traJ gene (for conjugation), and it has been adopted for genetic manipulation work in several acetogens (Köpke and Liew, 2011; Leang et al., 2013; Ueki et al., 2014; Hoffmeister et al., 2016).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Heap et al., 2009 source

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    • cites Köpke and Liew, 2011

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    • cites Leang et al., 2013 source

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  • May combine two claims.

    Premisereasoning

    Conjugation requires direct cell-to-cell contact during the transfer of DNA from donor to recipient, so this approach is limited by the host range of the donor.

    “This method requires direct cell-to-cell contact during the transfer of DNA from donor to recipient so this approach is limited by the host range of the donor.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Conjugation was reported for C. autoethanogenum using E. coli strain HB101 as donor and for A. woodii using E. coli strain S17-1 as donor.

    “Conjugation was reported for C. autoethanogenum (using E. coli strain HB101 as donor) (Mock et al., 2015), and A. woodii (using E. coli strain S17-1 as donor) (Strätz et al., 1994).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Mock et al., 2015 source

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    • cites Strätz et al., 1994 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisenone given

    Validated parts include variable-strength promoters, inducible expression systems, genetic circuits, transcription terminators, and ribosomal binding sites.

    “This include variable-strength promoters, inducible expression systems, genetic circuits, transcription terminators, and ribosomal bindings sites (RBSs).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    When coupled with next generation sequencing, transposon-directed insertion site sequencing performed on C. difficile identified 404 essential genes for growth and 798 genes that are likely to affect spore production.

    “When coupled with next generation sequencing, transposon-directed insertion site sequencing (TraDIS) was performed on C. difficile and identified 404 essential genes for growth and 798 genes that are likely to affect spore production (Dembek et al., 2015).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Dembek et al., 2015 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    ACE utilizes the activation or inactivation of gene(s) that result in a selectable phenotype, and asymmetrical homology arms to direct the order of recombination events.

    “Instead, it utilizes the activation or inactivation of gene(s) that result in a selectable phenotype, and asymmetrical homology arms to direct the order of recombination events (Heap et al., 2012).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Heap et al., 2012 source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisenone given

    Commonly used reporters such as green fluorescent protein require oxygen for the development of the chromophore responsible for fluorescence.

    “However, commonly used reporters such as green fluorescent protein (GFP) require oxygen for the development of the chromophore responsible for fluorescence.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Some acetogens such as C. autoethanogenum also have a native CRISPR system that has been shown to be actively transcribed.

    “Some acetogens as C. autoethanogenum also have a native CRSIPR system, that has been shown to be actively transcribed (Brown et al., 2014).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Brown et al., 2014 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The type II CRISPR/Cas9 system has been exploited for high-efficiency gene editing in model microorganisms such as E. coli, S. cerevisiae, and Streptococcus pneumoniae.

    “The type II CRISPR/Cas9 system has been exploited for high-efficiency gene editing in model microorganisms such as E. coli (Jiang et al., 2015), S. cerevisiae (DiCarlo et al., 2013), and Streptococcus pneumoniae (Jiang et al., 2013).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Jiang et al., 2015 source

      Not checked in the free run.

    • cites DiCarlo et al., 2013 source

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    • cites Jiang et al., 2013 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In an ACE example, a promoterless primary/secondary adh from C. beijerinckii coupled to the ermB gene was introduced downstream of the thlA gene in C. acetobutylicum, allowing selection for the second recombination event and creation of a recombinant that reduces acetone to isopropanol.

    “For example, a promoterless primary/secondary adh from C. beijerinckii coupled to the ermB gene was introduced into the downstream region of the thlA gene in the genome of C. acetobutylicum. The native promoter of thlA drives the expression of ermB and adh, allowing selection for the second recombination event using erythromycin or acid-stable analog clarithromycin, and also creation of a”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Heap et al., 2012 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Triple Cross forces a double crossover directly in the first step using a combination of positive selection marker and a negative selection marker, with an optional second step involving recycling of selection marker through the third homology arm and the second negative selection marker.

    “Instead of screening for a first crossover in the first step and a second crossover with a marker recycling in the second step, this invention forces a double crossover directly in the first step using a combination of positive selection marker and a negative selection marker. The optional second step involves the recycling of selection marker through the third homology arms and the second”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Walker and Köpke, 2015

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    An inducible transposon system for random mutagenesis has been described for C. acetobutylicum that showed over 90% successful transposition.

    “Recently, an inducible transposon system for random mutagenesis has been described for C. acetobutylicum that showed over 90% successful transposition (Zhang et al., 2016).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Zhang et al., 2016 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    A first proof of concept study that acetogens can be genetically modified was published in 2010.

    “A first proof of concept study that acetogens can be genetically modified was published in 2010 (Köpke et al., 2010).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Köpke et al., 2010 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Earlier efforts of transposon mutagenesis were demonstrated in C. saccharobutylicum, C. acetobutylicum, and C. beijerinckii, but issues with multiple transposon insertions per mutant and non-random distribution of insertions were reported.

    “Earlier efforts of transposon mutagenesis were demonstrated in C. saccharobutylicum (Keis et al., 2001), C. acetobutylicum, and C. beijerinckii, but issues with multiple transposon insertions per mutant, and non-random distribution of insertions were also reported (Bertram and Dürre, 1989; Woolley et al., 1989).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Keis et al., 2001 source

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    • cites Bertram and Dürre, 1989

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    • cites Woolley et al., 1989 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    ACE was also demonstrated in C. difficile and C. sporogenes, suggesting it is applicable to other Clostridium spp. including acetogens.

    “This technique was also demonstrated in C. difficile and C. sporogenes, suggesting it is applicable to other Clostridium spp. including acetogens (Heap et al., 2012; Ng et al., 2013).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Heap et al., 2012 source

      Not checked in the free run.

    • cites Ng et al., 2013

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Interpretationnone given

    In addition to further development of tools, more validated parts are required to allow efficient metabolic engineering and refinement of the existing tools.

    “In addition to the further development of tools, more validated parts are required to allow efficient metabolic engineering and refinement of the existing tools.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisereasoning

    Forward genetics aims to determine the genotype resulting in a particular phenotype, and this can be accomplished by generating a pool of random mutants via transposon mutagenesis.

    “In contrast, “forward genetics” do not make any assumptions about the genes involved and aim to determine the genotype resulting in a particular phenotype. To achieve this, a pool of random mutants needs to be generated. This can be accomplished by means of transposon mutagenesis.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Large libraries of promoters, terminators, and RBS calculators have been developed and characterized for model organisms like E. coli, dramatically increasing the control of metabolic pathways and allowing efficient pathway refactoring and design of genetic circuits.

    “Large libraries of promoters (Temme et al., 2012a), terminators (Chen et al., 2013b), and RBS calculators (Farasat et al., 2014) have been developed and characterized for model organisms like E. coli, dramatically increasing the control of metabolic pathways and allow efficient pathway refactoring and design of genetic circuits (Temme et al., 2012a,b).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Temme et al., 2012a

      Not checked in the free run.

    • cites Chen et al., 2013b

      Not checked in the free run.

    • cites Farasat et al., 2014 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Recent developments have seen the successful generation of mono-copy random insertion of transposon Tn1545 into C. cellulolyticum and mariner transposon Himar1 into C. difficile.

    “Recent developments have seen the successful generation of mono-copy random insertion of transposon Tn1545 into C. cellulolyticum (Blouzard et al., 2010) and mariner transposon Himar1 into C. difficile (Cartman and Minton, 2010; Zhang et al., 2015b).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Blouzard et al., 2010 source

      Not checked in the free run.

    • cites Cartman and Minton, 2010

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    • cites Zhang et al., 2015b

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    The CRISPR/Cas9 system is a RNA-guided prokaryotic immune system which can cleave foreign DNA such as phages and plasmids.

    “The Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system is a RNA-guided prokaryotic immune system which can cleave foreign DNA (e.g., phages and plasmids).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    C. ljungdahlii with plasmid-based expression of C. acetobutylicum butanol biosynthetic genes produced up to 148 mg/L n-butanol from synthetic syngas in bottles, with conversion to butyrate at end of growth.

    “| C. ljungdahlii | Plasmid based expression of C. acetobutylicum butanol biosynthetic genes (thlA-crt-hbd-bcd, adhE-bdhA) | Production of up to 148 mg/L n-butanol from synthetic syngas in bottles; Conversion to butyrate at end of growth | Köpke et al., 2010 |”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Köpke et al., 2010 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    C. difficile transposon mutagenesis identified 798 genes that are likely to affect sporulation.

    “| C. difficile | Generation of more than 70,000 unique mutants via transposon mutagenesis, coupled with transposon-directed insertion site sequencing | Identification of 404 essential genes for growth; Identification of 798 genes that are likely to affect sporulation | Dembek et al., 2015 |”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Dembek et al., 2015 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Chromosomal deletion of adhE1 in C. ljungdahlii causes a 6-fold reduction in ethanol concentration under heterotrophic conditions, but deletion of adhE2 does not.

    “| C. ljungdahlii | Chromosomal deletion of adhE1 and/or adhE2 | 6-fold reduction in ethanol concentration of ΔadhE1 mutant (but not ΔadhE2 mutant) under heterotrophic conditions | Leang et al., 2013 |”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Leang et al., 2013 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    C. autoethanogenum and C. ljungdahlii with plasmid-based expression of acetone and isopropanol biosynthetic genes produced up to 300 mg/L acetone and 25 mg/L isopropanol from steel mill gas and syngas in bottles, and continuously produced 700 mg/L/d isopropanol from steel mill gas in a CSTR.

    “| C. autoethanogenum, C. ljungdahlii | Plasmid based expression of acetone and isopropanol biosynthetic genes thlA (from C. acetobutylicum) and ctfA-ctfB-adc (from C. beijerinckii) | Production of up to 300 mg/L acetone and 25 mg/L isopropanol from steel mill gas and syngas in bottles; Continuous production of 700 mg/L/d isopropanol from steel mill gas in CSTR | Köpke et al., 2012 |”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Köpke et al., 2012

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    M. thermoacetica with genome insertion of ldh from Thermoanaerobacter pseudethanolicus into the pyrF locus produced up to 613 mg/L lactate from glucose in bottles under heterotrophic conditions; autotrophic production was not reported.

    “| M. thermoacetica | Genome insertion of ldh from Thermoanaerobacter pseudethanolicus into pyrF locus | Heterotrophic production of up to 613 mg/L lactate from glucose in bottles; Autotrophic production not reported | Kita et al., 2013 |”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Kita et al., 2013 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    C. difficile transposon mutagenesis identified 404 essential genes for growth.

    “| C. difficile | Generation of more than 70,000 unique mutants via transposon mutagenesis, coupled with transposon-directed insertion site sequencing | Identification of 404 essential genes for growth; Identification of 798 genes that are likely to affect sporulation | Dembek et al., 2015 |”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Dembek et al., 2015 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The complete WLP from various source organisms can be expressed in E. coli, but growth on CO and H2 could not be shown.

    “With the advancements in strain engineering, it became possible to express the complete WLP from various source organisms in E. coli (Burk et al., 2010; Trawick et al., 2012). While certain aspects could be demonstrated, growth on CO and H2 could not be shown.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Burk et al., 2010

      Not checked in the free run.

    • cites Trawick et al., 2012

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Jet fuels are typically aliphatic and contain 8-16 carbon atoms.

    “Jet fuels are typically aliphatic and contain 8–16 carbon atoms (Atsonios et al., 2015).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Atsonios et al., 2015 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Techniques to inhibit acetoclastic methanogens include pH control and high H2 partial pressure, which is estimated to confer greater growth advantage to homoacetogens over hydrogenotrophic methanogens.

    “Techniques to inhibit acetoclastic methanogens include pH control (Agler et al., 2014) and high H2 partial pressure, which is estimated to confer greater growth advantage to homoacetogens over hydrogenotrophic methanogens (Spirito et al., 2014).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Agler et al., 2014 source

      Not checked in the free run.

    • cites Spirito et al., 2014 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In first attempts to demonstrate parts of the WLP in E. coli in 1989, MeTr from M. thermoacetica was active, but activity was not detected for CODH/ACS and CoFeSP, and both CODH and CoFeSP were less thermostable than when isolated from the native host.

    “Genes encoding methyltransferase (MeTr), CODH/ACS, and CoFeSP from M. thermoacetica were cloned and heterologously expressed in E. coli (Roberts et al., 1989). Although the MeTr was found to be active, activity was not detected for the other two enzymes, and both CODH and CoFeSP were found to be less thermostable than when isolated from the native host.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Roberts et al., 1989 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    LanzaTech has demonstrated production of methyl ethyl ketone (MEK), 3-hydroxypropionate (3-HP), biodiesel, and jet fuel molecules via gas fermentation.

    “LanzaTech has demonstrated production of several additional high value molecules via gas fermentation, such as methyl ethyl ketone (MEK) (Mueller et al., 2013), 3-hydroxypropionate (3-HP) (Köpke and Chen, 2013), biodiesel, and jet fuel molecules (Liew and Köpke, 2012).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Mueller et al., 2013

      Not checked in the free run.

    • cites Köpke and Chen, 2013

      Not checked in the free run.

    • cites Liew and Köpke, 2012

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Gong et al. demonstrated lipid synthesis from acetate by multiple oleaginous yeast strains, with Cryptococcus curvatus ATCC 20509 yielding a lipid concentration of 4.2 g/L and 73.4% of the cell dry weight.

    “For instance, Gong et al. demonstrated lipid synthesis from acetate by multiple oleaginous yeast strains with one, Cryptococcus curvatus ATCC 20509, yielding a lipid concentration of 4.2 g/L and 73.4% of the cell dry weight (Gong et al., 2015).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Gong et al., 2015 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    "C. ragsdalei" can convert caproate at 62%, valerate at 82%, and butyrate at 100% efficiency to their respective alcohols.

    “Isom et al. for example, showed “C. ragsdalei” can convert caproate at 62%, valerate at 82%, and butyrate at 100% efficiency to their respective alcohols.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Isom et al., 2015 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    To obtain jet fuel from small alcohols, ethanol and butanol are first dehydrated to corresponding alkenes ethylene and butylene, which are then oligomerized to a desired range of sizes.

    “To obtain jet fuel from these small alcohols, ethanol and butanol (separated from the fermentation broth) are first dehydrated to corresponding alkenes ethylene and butylene (Harvey and Meylemans, 2011; Zhang and Yu, 2013). The alkenes are then oligomerized to a desired range of sizes (i.e., number of carbon atoms) that fit the end application (Heveling et al., 1998; Harvey and Meylemans, 2011).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Harvey and Meylemans, 2011

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    • cites Zhang and Yu, 2013 source

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    • cites Heveling et al., 1998 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given

    These chemical processes are generally faster than biological syntheses, and, if performed carefully, may still offer an overall reduction in GHG emissions for these products compared to traditional production from fossil fuels.

    “These chemical processes are generally faster than biological syntheses, and, if performed carefully, may still offer an overall reduction in GHG emissions for these products compared to traditional production from fossil fuels.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Hu et al. presented an integrated bioprocess where acetate made from CO2 and H2 by M. thermoacetica was converted to lipids by Yarrowia lipolytica, producing 18 g/L of triacylglycerides at 36% lipid content of cell weight.

    “Recent work from Hu et al., presented an integrated bioprocess where acetate made from CO2 and H2 by M. thermoacetica was converted to lipids by Yarrowia lipolytica (Hu et al., 2016). The two-stage system produced 18 g/L of triacylglycerides at 36% lipid content of cell weight.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Hu et al., 2016

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Richter et al. integrated three bioprocesses to produce alcohols, with the final step of carboxylic acid conversion to alcohols completed by syngas fermentation using C. ljungdahlii.

    “Richter et al. even integrated three bioprocesses to produce alcohols, with the final step of carboxylic acid conversion to alcohols completed by syngas fermentation (Richter et al., 2013a).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Richter et al., 2013a

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    H2/CO2 gas fermentations mostly produce acetate, though production of ethanol and other products such as acetone or butyrate have been described, albeit at lower productivity compared to CO.

    “H2/CO2 gas fermentations mostly produce acetate, though production of ethanol (Mock et al., 2015) and other products such as acetone (Schiel-Bengelsdorf and Dürre, 2012; Hoffmeister et al., 2016) or butyrate (Ueki et al., 2014) have been described, albeit at lower productivity compared to CO.”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Mock et al., 2015 source

      Not checked in the free run.

    • cites Schiel-Bengelsdorf and Dürre, 2012

      Not checked in the free run.

    • cites Ueki et al., 2014 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationreasoning

    Sourcing fuels and chemicals for polymer synthesis from renewable resources like biomass may be attainable with gas fermentation.

    “Sourcing fuels and chemicals for polymer synthesis from renewable resources like biomass may be attainable with gas fermentation.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given

    Even if advances in gas fermentation are able to expand to produce aviation fuels and thermoplastics at commercially-relevant rates, it is unlikely to develop quickly enough to completely replace the consumption of fossil fuels for their production.

    “Even if these advances in gas fermentation are able to expand to produce aviation fuels and thermoplastics at commercially-relevant rates, it is unlikely to develop quickly enough to completely replace the consumption of fossil fuels for their production.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationreasoning

    The combination of gas fermentation with established chemical processes could more quickly bring renewable aviation fuels and synthetic rubber to relevancy.

    “The combination of gas fermentation with established chemical processes, however, could more quickly bring renewable aviation fuels and synthetic rubber to relevancy.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given

    Gas fermentation has developed incredibly over the past years, leading to multiple endeavors for commercial production of ethanol from syngas.

    “Gas fermentation has developed incredibly over the past years, leading to multiple endeavors for commercial production of ethanol from syngas.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    1,3-butadiene is a precursor for nylon production.

    “1,3-butadiene is also a precursor for nylon production (Carraher, 2010), and LanzaTech is currently a part of multiple collaborations to develop gas fermentation production of 2,3-butanediol for the purpose of chemical conversion to 1,3-butadiene (Köpke and Havill, 2014).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Carraher, 2010 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given

    Significant strides in genetic manipulation of gas-fermenting bacteria (acetogens specifically) has granted access to new products and routes for enhancing production rates and yields.

    “Significant strides in genetic manipulation of gas-fermenting bacteria (acetogens specifically) has granted access to new products and routes for enhancing production rates and yields.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    LanzaTech is currently part of multiple collaborations to develop gas fermentation production of 2,3-butanediol for the purpose of chemical conversion to 1,3-butadiene.

    “1,3-butadiene is also a precursor for nylon production (Carraher, 2010), and LanzaTech is currently a part of multiple collaborations to develop gas fermentation production of 2,3-butanediol for the purpose of chemical conversion to 1,3-butadiene (Köpke and Havill, 2014).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Köpke and Havill, 2014

      Not checked in the free run.

94 of 94

  • The paper relies on this without support.

    Carbon-based materials, chemicals, and transportation fuels are predominantly made from fossil sources.

    “However, carbon-based materials, chemicals, and transportation fuels are predominantly made from fossil sources and currently there is no alternative source available to adequately displace them.”

  • The paper relies on this without support.

    No alternative source is currently available to adequately displace fossil carbon-based materials, chemicals, and transportation fuels.

    “However, carbon-based materials, chemicals, and transportation fuels are predominantly made from fossil sources and currently there is no alternative source available to adequately displace them.”

  • The paper relies on this without support.

    The time scale to 2050 is likely too short to switch away from and eliminate the need for carbon-based transportation fuels and chemicals.

    “However, this time scale is likely too short to switch away from and eliminate the need for carbon-based transportation fuels and chemicals.”

  • The paper relies on this without support.

    CO, H2, and CO2 have low aqueous solubilities (approximately 28 mg/L, 1.6 mg/L, and 1.7 g/L at 293 K, 1 atm, respectively) compared to glucose (900 g/L).

    “CO, H2, and CO2 are soluble to approximately 28 mg/L, 1.6 mg/L, and 1.7 g/L (293 K, 1 atm), respectively, compared to 900 g/L for glucose, a prevalent substrate for traditional fermentations.”
4 of 4

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Bioethanol can be produced through fermentation of carbon monoxide using specialized bacteria such as Clostridium autoethanogenum.

    “This process, known as gas fermentation, utilizes anaerobic bacteria such as Clostridium autoethanogenum to convert carbon monoxide into ethanol [96].”

    From Biofuel production: exploring renewable energy solutions for a greener future (2024) · cites this paper as [96]

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Conflicting pressures for the reported 360 g/L/d ethanol rate

    Minor

    The paper attributes the same highest reported ethanol production rate to operation at 1.7-2 bar in one section and 6 atmospheres in another.

  • Conflicting substrates for engineered M. thermoacetica lactate production

    Minor

    Table 2 says the reported lactate production used glucose, while the accompanying text says the experiments used fructose rather than gas.

2 of 2

Cites

Flagged first, then by citations

Research works printed but not linked: 65

  1. Al-Hinai, 2012b, Installing the wood-ljungdahl (WL) pathway in Clostridium acetobutylicum, Clostridium XII Conf.
  2. Aschenbrenner, 2016, World's Largest Hydrogen Electrolysis Facility
  3. Beck, 2014, Recombinant Anaerobic Acetogenic Bacteria for Production of Isoprene and/or Industrial Bio-Products Using Synthesis Gas.
  4. Beck, 2013, Compositions and Methods of Producing Isoprene and/or Industrial Bio-Products Using Anaerobic Microorganisms.
  5. Becker, 2012, Cells and Method for Producing Acetone.
  6. Boerrigter, 2005, Review of applications of gases from biomass gasification, 211
  7. Burk, 2010, Methods and Organisms for Utilizing Synthesis Gas or Other Gaseous Carbon Sources and Methanol.
  8. Clarke Energy, 2015, Steel Production Gas for Power Production
  9. Datta, 2014, Method for Production of n-Propanol and Other c3-containing Products from Syngas by Symbiotic Co-cultures of Anaerobic Microorganisms.
  10. Datta, 2014, Syntrophic Co-culture of Anaerobic Microorganism for Production of n-Butanol from Syngas.
  11. De Klerk, 2013, Greener Fischer-Tropsch Processes for Fuels and Feedstocks.
  12. Enzien, 2014, Method for Production of n-Propanol and/or Ethanol by Fermentation of Multiple Substrates in A Symbiotic Manner
  13. Evonik, 2013, Bacteria Like the Taste of Syngas
  14. Furutani, 2013, Recombinant Cell, and Method for Producing Isoprene
  15. Gaddy, 1997, Clostridium Strain Which Produces Acetic Acid from Waste Gases
  16. Gaddy, 2000, Clostridium Strains Which Produce Ethanol from Substrate-Containing Gases
  17. Gaddy, 1998, Bioconversion of Waste Biomass to Useful Products
  18. Global Bioenergies, 2016, Global Bioenergies and LANZATECH Strengthen Cooperation.
  19. Heijstra, 2012, Novel Bacteria and Methods of Use Thereof.
  20. Huhnke, 2008, Isolation and Characterization of Novel Clostridial Species
  21. INEOS Bio, 2014, INEOS Bio Provides Operational Update.
  22. INVISTA, 2015, INVISTA and LanzaTech Make Breakthrough for Bio-derived Butadiene Production.
  23. Jipa, 2009, Acetic acid extraction from fermentation broth experimental and modelling studies, Rev. Chim. Bucharest Orig. Ed., 60, 1084
  24. Köpke, 2013, Selection Method and Recombinant Microorganisms and Uses Therefor
  25. Köpke, 2015, Microorganisms and Methods for the Production of Ketones
  26. Köpke, 2013, Recombinant Microorganisms and Uses Therefor
  27. Köpke, 2014, LanzaTech's route to bio-butadiene, Catal. Rev., 27, 7
  28. Köpke, 2011, Recombinant Microorganism and Methods of Production Thereof.
  29. Köpke, 2013a, Recombinant Microorganisms and Methods of Use Thereof.
  30. Köpke, 2012, Fermentation Process for Producing Isopropanol Using a Recombinant Microorganism
  31. Lane, 2014, On the Mend: Why INEOS Bio Isn't Producing Ethanol in Florida.
  32. Lane, 2015a, Alcohol to renewable jet fuel: the Digest's 2015 8-Slide Guide to Gevo's ATJ, Biofuels Dig.
  33. Lane, 2015b, China steel green-lights commercial-scale LanzaTech advanced biofuels project, Biofuels Dig.
  34. Lane, 2015c, Steel's Big Dog jumps into low carbon fuels: ArcelorMittal, LanzaTech, Primetals Technologies to construct $96M biofuel production facility, Biofuels Dig.
  35. Lane, 2016, Coskata's Technology Re-emerges as Synata Bio
  36. LanzaTech, 2013, Evonik and LanzaTech Working on Bio-Processed Precursors for Specialty Plastics.
  37. LanzaTech, 2015, Fuels
  38. LanzaTech, 2016, Aemetis Acquires License from LanzaTech with California Exclusive Rights for Advanced Ethanol from Biomass
  39. Levinson, 2014, A Butyrate Producing Clostridium Species, Clostridium pharus
  40. Liew, 2012, Recombinant Microorganisms Make Biodiesel
  41. 2007, Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, 2007
  42. Mueller, 2013, Recombinant Microorganisms and Uses Therefor
  43. Nagaraju, 2015, Recombinant Microorganisms and Methods of Use Thereof.
  44. National Energy Technology Laboratory, 2013, Water Gas Shift & Hydrogen Production
  45. National Energy Technology Laboratory, 2014, Alternatives/Supplements to Coal - Feedstock Flexibility.
  46. NEL Hydrogen, 2015, Efficient Electrolysers for Hydrogen Production
  47. Oakley, 2011, Improved Fermentation of Waste Gases
  48. OPUS 12, 2015, A Profitable Solution to CO2.
  49. Ritter, 2015, CO2 Electrolyzer Nears Commercialization.
  50. Schill, 2013, Ineos declares commercial cellulosic ethanol online in Florida, Ethanol Prod. Mag.
  51. SCS Global Services, 2013, Beijing Shougang LanzaTech New Energy Science and Technology Company Earns Roundtable on Sustainable Biomaterials (RSB) Certification
  52. Siemens, 2013, Silyzer - A Proton-Exchange-Membrane (PEM) Technology Based on Electrolysis System.
  53. Simpson, 2009a, Microbial Alcohol Production Process
  54. Simpson, 2009b, Novel Bacteria and Methods of Use Thereof.
  55. Simpson, 2011, Recombinant Microorganisms and Methods of Use Thereof.
  56. Simpson, 2014, System and Method for Controlling Metabolite Production in a Microbial Fermentation
  57. Simpson, 2010, Optimised Fermentation Media
  58. Soucaille, 2008, Process for Chromosomal Integration and DNA Sequence Replacement In Clostridia
  59. Stephanopoulos, 2011, Bioprocess And Microbe Engineering for Total Carbon Utilization in Biofuel Production.
  60. Trawick, 2012, Microorganisms and Methods for Conversion of Syngas and Other Carbon Sources to Useful Products
  61. Vakkilainen, 2013, Large Industrial Users of Energy Biomass
  62. Walker, 2015, Recombinant Microorganisms and Methods of Use Thereof.
  63. Walker, 2015, Method of Producing a Recombinant Microorganism
  64. Wood, 1991, Life with CO or CO2 and H2 as a source of carbon and energy, Fed. Am. Soc. Exp. Biol. J., 5, 156
  65. Zahn, 2012, Ethanologenic Clostridium Species, Clostridium coskatii.

Cited by

Sorted by citations

Related

Authors
Liew, F., Martin, M. E., Tappel, R. C., Heijstra, B. D., Mihalcea, C., & Köpke, M.
Corresponding author
Köpke, Michael
ORCID
Venue
Frontiers in Microbiology
Publisher
Frontiers Media SA
Published
2016-05-11
Volume
7
Pages
694-694
ISSN
1664-302X (ISSN-L)
DOI
10.3389/fmicb.2016.00694
PMC
PMC4862988
OpenAlex
W2412234405
Cited by
485
References
299
Citations by year
2026: 37 · 2025: 51 · 2024: 50 · 2023: 58 · 2022: 74 · 2021: 57 · 2020: 59 · 2019: 42 · 2018: 23 · 2017: 26 · 2016: 8
FWCI
2.98
Type
journal article
Language
en
Open access
Licence
cc-by
Locations
  • Frontiers in Microbiology (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Microbial Metabolic Engineering and Bioproduction
  • Physical Sciences › Engineering › Biomedical Engineering › Biofuel production and bioconversion
  • Physical Sciences › Engineering › Building and Construction › Anaerobic Digestion and Biogas Production
Keywords
gas fermentation, CO2 fixation, low-carbon fuels, renewable chemicals, waste feedstocks, synthetic biology, ethanol production, biomass gasification, industrial-scale production

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Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-10.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-10.

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