Anaerobic CO<sub>2</sub> fixation by the acetogenic bacterium <i>Moorella thermoacetica</i>

Hu, Peng; Rismani-Yazdi, Hamid; Stephanopoulos, Gregory

doi:10.1002/aic.14127

Cited by 55 publications

(44 citation statements)

References 28 publications

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“…Although syngas has historically been used for gas engines and the production of bulk chemicals, such as methanol, acetate, and carbohydrate, by chemical processes, acetogens have recently received greater attention as hosts for producing biofuels and bulk chemicals from syngas (1). Acetogens can grow by using H 2 and CO as electron donors and CO 2 as a carbon source.…”

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confidence: 99%

Homolactic Acid Fermentation by the Genetically Engineered Thermophilic Homoacetogen Moorella thermoacetica ATCC 39073

Iwasaki

Kita

Yoshida

et al. 2017

Appl Environ Microbiol

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For the efficient production of target metabolites from carbohydrates, syngas, or H 2 -CO 2 by genetically engineered Moorella thermoacetica, the control of acetate production (a main metabolite of M. thermoacetica) is desired. Although propanediol utilization protein (PduL) was predicted to be a phosphotransacetylase (PTA) involved in acetate production in M. thermoacetica, this has not been confirmed. Our findings described herein directly demonstrate that two putative PduL proteins, encoded by Moth_0864 (pduL1) and Moth_1181 (pduL2), are involved in acetate formation as PTAs. To disrupt these genes, we replaced each gene with a lactate dehydrogenase gene from Thermoanaerobacter pseudethanolicus ATCC 33223 (T-ldh). The acetate production from fructose as the sole carbon source by the pduL1 deletion mutant was not deficient, whereas the disruption of pduL2 significantly decreased the acetate yield to approximately one-third that of the wild-type strain. The double-deletion (both pduL genes) mutant did not produce acetate but produced only lactate as the end product from fructose. These results suggest that both pduL genes are associated with acetate formation via acetyl-coenzyme A (acetyl-CoA) and that their disruption enables a shift in the homoacetic pathway to the genetically synthesized homolactic pathway via pyruvate.IMPORTANCE This is the first report, to our knowledge, on the experimental identification of PTA genes in M. thermoacetica and the shift of the native homoacetic pathway to the genetically synthesized homolactic pathway by their disruption on a sugar platform.KEYWORDS thermophilic, acetogen, Moorella, transformation, biomass, sugar, syngas, fermentation T he use of various forms of renewable energy and industrial bulk chemicals is increasingly desired because of concerns about the depletion of fossil resources and the existence of global warming/climate change. Solar, wind, waterpower, and biomass energies are abundant forms of renewable energy that are available all over the world, and they are promising as sources that could meet the global demand for energy as electricity and heat. However, the number and amount of renewable resources for producing bulk substrates are very limited. Presently, bulk chemicals used to produce, for example, plastics and paints, are produced from naphtha.

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confidence: 99%

Homolactic Acid Fermentation by the Genetically Engineered Thermophilic Homoacetogen Moorella thermoacetica ATCC 39073

Iwasaki

Kita

Yoshida

et al. 2017

Appl Environ Microbiol

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“…2, which presents time courses for growth and acetic acid titer in an anaerobic bubble column run independently. Our prior work provided the basis for flow rates relevant to this study (7). Fermentation was carried out at a flow rate of 1,000 standard cubic centimeters per minute (sccm), using either CO or H 2 as reducing gas at a composition of 7/3 CO/CO 2 or 7/3 H 2 /CO 2 .…”

Section: Resultsmentioning

confidence: 99%

“…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 glucose at high yields and productivities (2,5).…”

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confidence: 87%

Integrated bioprocess for conversion of gaseous substrates to liquids

Chakraborty

Kumar

et al. 2016

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

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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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“…Recently, Moorella thermoacetica, a thermophilic acetogenic bacterium which produces acetic acid as the only end product of the WL pathway, was used in a bubble column reactor for conversion of syngas to acetic acid with improved productivity [76]. Fermentation of CO by Clostridium carboxidivorans has also been performed, which showed the formation of acetic acid, butyric acid, and ethanol when pH was not regulated, whereas with pH regulation ethanol and butanol were formed both from CO fermentation and from the bioconversion of acetic-and butyric acids [77].…”

Section: Production Of Chemicals and Fuels From Carbon Dioxidementioning

confidence: 99%

Anaerobes in Industrial- and Environmental Biotechnology

Hatti‐Kaul

Mattìasson

2016

Advances in Biochemical Engineering/Biotechnology

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Anaerobic microorganisms present in diverse ecological niches employ alternative strategies for energy conservation in the absence of oxygen which enables them to play a key role in maintaining the global cycles of carbon, nitrogen, and sulfur, and the breakdown of persistent compounds. Thereby they become useful tools in industrial and environmental biotechnology. Although anaerobes have been relatively neglected in comparison to their aerobic counterparts, with increasing knowledge about their diversity and metabolic potential and the development of genetic tools and process technologies to utilize them, we now see a rapid expansion of their applications in the society. This chapter summarizes some of the developments in the use of anaerobes as tools for biomass valorization, in production of energy carriers and chemicals, wastewater treatment, and the strong potential in soil remediation. The ability of several autotrophic anaerobes to reduce carbon dioxide is attracting growing attention as a means for developing a platform for conversion of waste gases to chemicals, materials, and biofuels.

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Anaerobic CO₂ fixation by the acetogenic bacterium Moorella thermoacetica

Cited by 55 publications

References 28 publications

Homolactic Acid Fermentation by the Genetically Engineered Thermophilic Homoacetogen Moorella thermoacetica ATCC 39073

Homolactic Acid Fermentation by the Genetically Engineered Thermophilic Homoacetogen Moorella thermoacetica ATCC 39073

Integrated bioprocess for conversion of gaseous substrates to liquids

Anaerobes in Industrial- and Environmental Biotechnology

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Anaerobic CO2 fixation by the acetogenic bacterium Moorella thermoacetica

Cited by 55 publications

References 28 publications

Homolactic Acid Fermentation by the Genetically Engineered Thermophilic Homoacetogen Moorella thermoacetica ATCC 39073

Homolactic Acid Fermentation by the Genetically Engineered Thermophilic Homoacetogen Moorella thermoacetica ATCC 39073

Integrated bioprocess for conversion of gaseous substrates to liquids

Anaerobes in Industrial- and Environmental Biotechnology

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Anaerobic CO₂ fixation by the acetogenic bacterium Moorella thermoacetica