1
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Synergistic effects of inhibitors and osmotic stress during high gravity bioethanol production from steam-exploded lignocellulosic feedstocks. BIOCATALYSIS AND AGRICULTURAL BIOTECHNOLOGY 2022. [DOI: 10.1016/j.bcab.2022.102414] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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2
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Bing RG, Sulis DB, Wang JP, Adams MW, Kelly RM. Thermophilic microbial deconstruction and conversion of natural and transgenic lignocellulose. ENVIRONMENTAL MICROBIOLOGY REPORTS 2021; 13:272-293. [PMID: 33684253 PMCID: PMC10519370 DOI: 10.1111/1758-2229.12943] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 02/25/2021] [Accepted: 02/28/2021] [Indexed: 06/12/2023]
Abstract
The potential to convert renewable plant biomasses into fuels and chemicals by microbial processes presents an attractive, less environmentally intense alternative to conventional routes based on fossil fuels. This would best be done with microbes that natively deconstruct lignocellulose and concomitantly form industrially relevant products, but these two physiological and metabolic features are rarely and simultaneously observed in nature. Genetic modification of both plant feedstocks and microbes can be used to increase lignocellulose deconstruction capability and generate industrially relevant products. Separate efforts on plants and microbes are ongoing, but these studies lack a focus on optimal, complementary combinations of these disparate biological systems to obtain a convergent technology. Improving genetic tools for plants have given rise to the generation of low-lignin lines that are more readily solubilized by microorganisms. Most focus on the microbiological front has involved thermophilic bacteria from the genera Caldicellulosiruptor and Clostridium, given their capacity to degrade lignocellulose and to form bio-products through metabolic engineering strategies enabled by ever-improving molecular genetics tools. Bioengineering plant properties to better fit the deconstruction capabilities of candidate consolidated bioprocessing microorganisms has potential to achieve the efficient lignocellulose deconstruction needed for industrial relevance.
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Affiliation(s)
- Ryan G. Bing
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695
| | - Daniel B. Sulis
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695
| | - Jack P. Wang
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695
| | - Michael W.W. Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602
| | - Robert M. Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695
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3
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Kato J, Takemura K, Kato S, Fujii T, Wada K, Iwasaki Y, Aoi Y, Matsushika A, Murakami K, Nakashimada Y. Metabolic engineering of Moorella thermoacetica for thermophilic bioconversion of gaseous substrates to a volatile chemical. AMB Express 2021; 11:59. [PMID: 33891189 PMCID: PMC8065083 DOI: 10.1186/s13568-021-01220-w] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2021] [Accepted: 04/09/2021] [Indexed: 11/26/2022] Open
Abstract
Gas fermentation is one of the promising bioprocesses to convert CO2 or syngas to important chemicals. Thermophilic gas fermentation of volatile chemicals has the potential for the development of consolidated bioprocesses that can simultaneously separate products during fermentation. This study reports the production of acetone from CO2 and H2, CO, or syngas by introducing the acetone production pathway using acetyl–coenzyme A (Ac-CoA) and acetate produced via the Wood–Ljungdahl pathway in Moorella thermoacetica. Reducing the carbon flux from Ac-CoA to acetate through genetic engineering successfully enhanced acetone productivity, which varied on the basis of the gas composition. The highest acetone productivity was obtained with CO–H2, while autotrophic growth collapsed with CO2–H2. By adding H2 to CO, the acetone productivity from the same amount of carbon source increased compared to CO gas only, and the maximum specific acetone production rate also increased from 0.04 to 0.09 g-acetone/g-dry cell/h. Our development of the engineered thermophilic acetogen M. thermoacetica, which grows at a temperature higher than the boiling point of acetone (58 °C), would pave the way for developing a consolidated process with simplified and cost-effective recovery via condensation following gas fermentation.
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4
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Straub CT, Bing RG, Otten JK, Keller LM, Zeldes BM, Adams MWW, Kelly RM. Metabolically engineered Caldicellulosiruptor bescii as a platform for producing acetone and hydrogen from lignocellulose. Biotechnol Bioeng 2020; 117:3799-3808. [PMID: 32770740 DOI: 10.1002/bit.27529] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 07/12/2020] [Accepted: 08/05/2020] [Indexed: 11/10/2022]
Abstract
The production of volatile industrial chemicals utilizing metabolically engineered extreme thermophiles offers the potential for processes with simultaneous fermentation and product separation. An excellent target chemical for such a process is acetone (Tb = 56°C), ideally produced from lignocellulosic biomass. Caldicellulosiruptor bescii (Topt 78°C), an extremely thermophilic fermentative bacterium naturally capable of deconstructing and fermenting lignocellulose, was metabolically engineered to produce acetone. When the acetone pathway construct was integrated into a parent strain containing the bifunctional alcohol dehydrogenase from Clostridium thermocellum, acetone was produced at 9.1 mM (0.53 g/L), in addition to minimal ethanol 3.3 mM (0.15 g/L), along with net acetate consumption. This demonstrates that C. bescii can be engineered with balanced pathways in which renewable carbohydrate sources are converted to useful metabolites, primarily acetone and H2 , without net production of its native fermentation products, acetate and lactate.
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Affiliation(s)
- Christopher T Straub
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina
| | - Ryan G Bing
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina
| | - Jonathan K Otten
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina
| | - Lisa M Keller
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina
| | - Benjamin M Zeldes
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina
| | - Michael W W Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia
| | - Robert M Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina
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5
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Scully SM, Orlygsson J. Biotransformation of Carboxylic Acids to Alcohols: Characterization of Thermoanaerobacter Strain AK152 and 1-Propanol Production via Propionate Reduction. Microorganisms 2020; 8:microorganisms8060945. [PMID: 32586016 PMCID: PMC7356315 DOI: 10.3390/microorganisms8060945] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 06/18/2020] [Accepted: 06/19/2020] [Indexed: 11/22/2022] Open
Abstract
Thermoanaerobacter strains have recently gained interest because of their ability to convert short chain fatty acids to alcohols using actively growing cells. Thermoanaerobacter thermohydrosulfuricus strain AK152 was physiologically investigated for its ethanol and other alcohol formation. The temperature and pH optimum of the strain was 70 °C and pH 7.0 and the strain degraded a variety of compounds present in lignocellulosic biomass like monosaccharides, disaccharides, and starch. The strain is highly ethanologenic, producing up to 86% of the theoretical ethanol yield form hexoses. Strain AK152 was inhibited by relatively low initial substrate (30 mM) concentration, leading to inefficient degradation of glucose and levelling up of all end-product formation. The present study shows that the strain produces alcohols from most of the tested carboxylic acids, with the highest yields for propionate conversion to propanol (40.7%) with kinetic studies demonstrating that the maximum conversion happens within the first 48 h of fermentation. Various physiological tests were performed to maximize the acid conversion to the alcohol which reveals that the optimum pH for propionate conversion is pH 6.7 which affords a 57.3% conversion. Kinetic studies reveal that propionate conversion is rapid, achieving a maximum conversion within the first 48 h of fermentation. Finally, by using 13C NMR, it was shown that the addition of propionate indeed converted to propanol.
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6
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Holwerda EK, Olson DG, Ruppertsberger NM, Stevenson DM, Murphy SJL, Maloney MI, Lanahan AA, Amador-Noguez D, Lynd LR. Metabolic and evolutionary responses of Clostridium thermocellum to genetic interventions aimed at improving ethanol production. BIOTECHNOLOGY FOR BIOFUELS 2020; 13:40. [PMID: 32175007 PMCID: PMC7063780 DOI: 10.1186/s13068-020-01680-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 02/10/2020] [Indexed: 05/06/2023]
Abstract
BACKGROUND Engineering efforts targeted at increasing ethanol by modifying the central fermentative metabolism of Clostridium thermocellum have been variably successful. Here, we aim to understand this variation by a multifaceted approach including genomic and transcriptomic analysis combined with chemostat cultivation and high solids cellulose fermentation. Three strain lineages comprising 16 strains total were examined. Two strain lineages in which genes involved in pathways leading to organic acids and/or sporulation had been knocked out resulted in four end-strains after adaptive laboratory evolution (ALE). A third strain lineage recapitulated mutations involving adhE that occurred spontaneously in some of the engineered strains. RESULTS Contrary to lactate dehydrogenase, deleting phosphotransacetylase (pta, acetate) negatively affected steady-state biomass concentration and caused increased extracellular levels of free amino acids and pyruvate, while no increase in ethanol was detected. Adaptive laboratory evolution (ALE) improved growth and shifted elevated levels of amino acids and pyruvate towards ethanol, but not for all strain lineages. Three out of four end-strains produced ethanol at higher yield, and one did not. The occurrence of a mutation in the adhE gene, expanding its nicotinamide-cofactor compatibility, enabled two end-strains to produce more ethanol. A disruption in the hfsB hydrogenase is likely the reason why a third end-strain was able to make more ethanol. RNAseq analysis showed that the distribution of fermentation products was generally not regulated at the transcript level. At 120 g/L cellulose loadings, deletions of spo0A, ldh and pta and adaptive evolution did not negatively influence cellulose solubilization and utilization capabilities. Strains with a disruption in hfsB or a mutation in adhE produced more ethanol, isobutanol and 2,3-butanediol under these conditions and the highest isobutanol and ethanol titers reached were 5.1 and 29.9 g/L, respectively. CONCLUSIONS Modifications in the organic acid fermentative pathways in Clostridium thermocellum caused an increase in extracellular pyruvate and free amino acids. Adaptive laboratory evolution led to improved growth, and an increase in ethanol yield and production due a mutation in adhE or a disruption in hfsB. Strains with deletions in ldh and pta pathways and subjected to ALE demonstrated undiminished cellulolytic capabilities when cultured on high cellulose loadings.
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Affiliation(s)
- Evert K. Holwerda
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Daniel G. Olson
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | | | - David M. Stevenson
- Department of Bacteriology, University of Wisconsin, Madison, WI 53706 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Sean J. L. Murphy
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
| | - Marybeth I. Maloney
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Anthony A. Lanahan
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Daniel Amador-Noguez
- Department of Bacteriology, University of Wisconsin, Madison, WI 53706 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Lee R. Lynd
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
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7
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Scully SM, Brown A, Ross AB, Orlygsson J. Biotransformation of organic acids to their corresponding alcohols by Thermoanaerobacter pseudoethanolicus. Anaerobe 2019; 57:28-31. [PMID: 30876932 DOI: 10.1016/j.anaerobe.2019.03.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 02/15/2019] [Accepted: 03/05/2019] [Indexed: 11/24/2022]
Abstract
Higher order alcohols, such as 1-butanol and 1-hexanol, have a large number of applications but are currently prepared from non-renewable feedstocks. Here, the ability of Thermoanaerobacter pseudoethanolicus to reduce short-chain fatty acids to their corresponding alcohols using reducing potential generated by glucose catabolism with yields between 21.0 and 61.0%. 13C-labelled acetate, 1-propionate and 1-butyrate demonstrates that exogenously added fatty acids are indeed reduced to their corresponding alcohols. This mode of producing primary alcohols from fatty acids using a thermophilic anaerobe opens the door for the production of such alcohols from low-value materials using an inexpensive source of reducing potential.
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Affiliation(s)
- Sean M Scully
- Faculty of Natural Resource Science, University of Akureyri, Borgir, Nordurslod 2, 600, Akureyri, Iceland
| | - Aaron Brown
- School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - Andrew B Ross
- School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - Johann Orlygsson
- Faculty of Natural Resource Science, University of Akureyri, Borgir, Nordurslod 2, 600, Akureyri, Iceland.
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8
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Zeldes BM, Straub CT, Otten JK, Adams MW, Kelly RM. A synthetic enzymatic pathway for extremely thermophilic acetone production based on the unexpectedly thermostable acetoacetate decarboxylase from Clostridium acetobutylicum. Biotechnol Bioeng 2018; 115:2951-2961. [PMID: 30199090 PMCID: PMC6231964 DOI: 10.1002/bit.26829] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 08/25/2018] [Accepted: 09/05/2018] [Indexed: 01/02/2023]
Abstract
One potential advantage of an extremely thermophilic metabolic engineering host (T opt ≥ 70°C) is facilitated recovery of volatile chemicals from the vapor phase of an active fermenting culture. This process would reduce purification costs and concomitantly alleviate toxicity to the cells by continuously removing solvent fermentation products such as acetone or ethanol, a process we are calling "bio-reactive distillation." Although extremely thermophilic heterologous metabolic pathways can be inspired by existing mesophilic versions, they require thermostable homologs of the constituent enzymes if they are to be utilized in extremely thermophilic bacteria or archaea. Production of acetone from acetyl-CoA and acetate in the mesophilic bacterium Clostridium acetobutylicum utilizes three enzymes: thiolase, acetoacetyl-CoA: acetate CoA transferase (CtfAB), and acetoacetate decarboxylase (Adc). Previously reported biocatalytic pathways for acetone production were demonstrated only as high as 55°C. Here, we demonstrate a synthetic enzymatic pathway for acetone production that functions up to at least 70°C in vitro, made possible by the unusual thermostability of Adc from the mesophile C. acetobutylicum, and heteromultimeric acetoacetyl-CoA:acetate CoA-transferase (CtfAB) complexes from Thermosipho melanesiensis and Caldanaerobacter subterraneus, composed of a highly thermostable α-subunit and a thermally labile β-subunit. The three enzymes produce acetone in vitro at temperatures of at least 70°C, paving the way for bio-reactive distillation of acetone using a metabolically engineered extreme thermophile as a production host.
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Affiliation(s)
- Benjamin M. Zeldes
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695
| | - Christopher T. Straub
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695
| | - Jonathan K. Otten
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695
| | - Michael W.W. Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602
| | - Robert M. Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695
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9
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Eminoğlu A, Murphy SJL, Maloney M, Lanahan A, Giannone RJ, Hettich RL, Tripathi SA, Beldüz AO, Lynd LR, Olson DG. Deletion of the hfsB gene increases ethanol production in Thermoanaerobacterium saccharolyticum and several other thermophilic anaerobic bacteria. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:282. [PMID: 29213322 PMCID: PMC5707799 DOI: 10.1186/s13068-017-0968-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 11/13/2017] [Indexed: 05/22/2023]
Abstract
BACKGROUND With the discovery of interspecies hydrogen transfer in the late 1960s (Bryant et al. in Arch Microbiol 59:20-31, 1967), it was shown that reducing the partial pressure of hydrogen could cause mixed acid fermenting organisms to produce acetate at the expense of ethanol. Hydrogen and ethanol are both more reduced than glucose. Thus there is a tradeoff between production of these compounds imposed by electron balancing requirements; however, the mechanism is not fully known. RESULTS Deletion of the hfsA or B subunits resulted in a roughly 1.8-fold increase in ethanol yield. The increase in ethanol production appears to be associated with an increase in alcohol dehydrogenase activity, which appears to be due, at least in part, to increased expression of the adhE gene, and may suggest a regulatory linkage between hfsB and adhE. We studied this system most intensively in the organism Thermoanaerobacterium saccharolyticum; however, deletion of hfsB also increases ethanol production in other thermophilic bacteria suggesting that this could be used as a general technique for engineering thermophilic bacteria for improved ethanol production in organisms with hfs-type hydrogenases. CONCLUSION Since its discovery by Shaw et al. (JAMA 191:6457-64, 2009), the hfs hydrogenase has been suspected to act as a regulator due to the presence of a PAS domain. We provide additional support for the presence of a regulatory phenomenon. In addition, we find a practical application for this scientific insight, namely increasing ethanol yield in strains that are of interest for ethanol production from cellulose or hemicellulose. In two of these organisms (T. xylanolyticum and T. thermosaccharolyticum), the ethanol yields are the highest reported to date.
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Affiliation(s)
- Ayşenur Eminoğlu
- Department of Biology, Molecular Biology Research Laboratories, Faculty of Art and Science, Recep Tayyip Erdogan University, Rize, Turkey
| | - Sean Jean-Loup Murphy
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | - Marybeth Maloney
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | - Anthony Lanahan
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | - Richard J. Giannone
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | - Robert L. Hettich
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | | | - Ali Osman Beldüz
- Department of Biology, Faculty of Science, Karadeniz Technical University, Trabzon, Turkey
| | - Lee R. Lynd
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
- Department of Biological Sciences, Dartmouth College, Hanover, NH USA
| | - Daniel G. Olson
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA
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10
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Straub CT, Zeldes BM, Schut GJ, Adams MWW, Kelly RM. Extremely thermophilic energy metabolisms: biotechnological prospects. Curr Opin Biotechnol 2017; 45:104-112. [DOI: 10.1016/j.copbio.2017.02.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Revised: 02/14/2017] [Accepted: 02/24/2017] [Indexed: 12/16/2022]
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11
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Zhou J, Shao X, Olson DG, Murphy SJL, Tian L, Lynd LR. Determining the roles of the three alcohol dehydrogenases (AdhA, AdhB and AdhE) in Thermoanaerobacter ethanolicus during ethanol formation. J Ind Microbiol Biotechnol 2017; 44:745-757. [PMID: 28078513 DOI: 10.1007/s10295-016-1896-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 12/22/2016] [Indexed: 12/25/2022]
Abstract
Thermoanaerobacter ethanolicus is a promising candidate for biofuel production due to the broad range of substrates it can utilize and its high ethanol yield compared to other thermophilic bacteria, such as Clostridium thermocellum. Three alcohol dehydrogenases, AdhA, AdhB and AdhE, play key roles in ethanol formation. To study their physiological roles during ethanol formation, we deleted them separately and in combination. Previously, it has been thought that both AdhB and AdhE were bifunctional alcohol dehydrogenases. Here we show that AdhE has primarily acetyl-CoA reduction activity (ALDH) and almost no acetaldehyde reduction (ADH) activity, whereas AdhB has no ALDH activity and but high ADH activity. We found that AdhA and AdhB have similar patterns of activity. Interestingly, although deletion of both adhA and adhB reduced ethanol production, a single deletion of either one actually increased ethanol yields by 60-70%.
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Affiliation(s)
- Jilai Zhou
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA.,Bioenergy Science Center, Oak Ridge, TN, USA
| | - Xiongjun Shao
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA.,Bioenergy Science Center, Oak Ridge, TN, USA
| | - Daniel G Olson
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA.,Bioenergy Science Center, Oak Ridge, TN, USA
| | - Sean Jean-Loup Murphy
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA.,Bioenergy Science Center, Oak Ridge, TN, USA
| | - Liang Tian
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA.,Bioenergy Science Center, Oak Ridge, TN, USA
| | - Lee R Lynd
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA. .,Bioenergy Science Center, Oak Ridge, TN, USA.
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12
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Advances in Consolidated Bioprocessing Using Clostridium thermocellumand Thermoanaerobacter saccharolyticum. Ind Biotechnol (New Rochelle N Y) 2016. [DOI: 10.1002/9783527807796.ch10] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
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13
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Ferredoxin:NAD+ Oxidoreductase of Thermoanaerobacterium saccharolyticum and Its Role in Ethanol Formation. Appl Environ Microbiol 2016; 82:7134-7141. [PMID: 27694237 DOI: 10.1128/aem.02130-16] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 09/27/2016] [Indexed: 01/01/2023] Open
Abstract
Ferredoxin:NAD+ oxidoreductase (NADH-FNOR) catalyzes the transfer of electrons from reduced ferredoxin to NAD+ This enzyme has been hypothesized to be the main enzyme responsible for ferredoxin oxidization in the NADH-based ethanol pathway in Thermoanaerobacterium saccharolyticum; however, the corresponding gene has not yet been identified. Here, we identified the Tsac_1705 protein as a candidate FNOR based on the homology of its functional domains. We then confirmed its activity in vitro with a ferredoxin-based FNOR assay. To determine its role in metabolism, the tsac_1705 gene was deleted in different strains of T. saccharolyticum In wild-type T. saccharolyticum, deletion of tsac_1705 resulted in a 75% loss of NADH-FNOR activity, which indicated that Tsac_1705 is the main NADH-FNOR in T. saccharolyticum When both NADH- and NADPH-linked FNOR genes were deleted, the ethanol titer decreased and the ratio of ethanol to acetate approached unity, indicative of the absence of FNOR activity. Finally, we tested the effect of heterologous expression of Tsac_1705 in Clostridium thermocellum and found improvements in both the titer and the yield of ethanol. IMPORTANCE Redox balance plays a crucial role in many metabolic engineering strategies. Ferredoxins are widely used as electron carriers for anaerobic microorganism and plants. This study identified the gene responsible for electron transfer from ferredoxin to NAD+, a key reaction in the ethanol production pathway of this organism and many other metabolic pathways. Identification of this gene is an important step in transferring the ethanol production ability of this organism to other organisms.
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14
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Zhou J, Wu K, Rao CV. Evolutionary engineering of Geobacillus thermoglucosidasius
for improved ethanol production. Biotechnol Bioeng 2016; 113:2156-67. [DOI: 10.1002/bit.25983] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 02/12/2016] [Accepted: 03/18/2016] [Indexed: 01/30/2023]
Affiliation(s)
- Jiewen Zhou
- Department of Chemical and Biomolecular Engineering; University of Illinois at Urbana-Champaign; 600 S. Mathews Ave Urbana Illinois 61801
| | - Kang Wu
- Department of Chemical Engineering; University of New Hampshire; Durham New Hampshire
| | - Christopher V. Rao
- Department of Chemical and Biomolecular Engineering; University of Illinois at Urbana-Champaign; 600 S. Mathews Ave Urbana Illinois 61801
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15
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Herring CD, Kenealy WR, Joe Shaw A, Covalla SF, Olson DG, Zhang J, Ryan Sillers W, Tsakraklides V, Bardsley JS, Rogers SR, Thorne PG, Johnson JP, Foster A, Shikhare ID, Klingeman DM, Brown SD, Davison BH, Lynd LR, Hogsett DA. Strain and bioprocess improvement of a thermophilic anaerobe for the production of ethanol from wood. BIOTECHNOLOGY FOR BIOFUELS 2016; 9:125. [PMID: 27313661 PMCID: PMC4910263 DOI: 10.1186/s13068-016-0536-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 05/31/2016] [Indexed: 05/16/2023]
Abstract
BACKGROUND The thermophilic, anaerobic bacterium Thermoanaerobacterium saccharolyticum digests hemicellulose and utilizes the major sugars present in biomass. It was previously engineered to produce ethanol at yields equivalent to yeast. While saccharolytic anaerobes have been long studied as potential biomass-fermenting organisms, development efforts for commercial ethanol production have not been reported. RESULTS Here, we describe the highest ethanol titers achieved from T. saccharolyticum during a 4-year project to develop it for industrial production of ethanol from pre-treated hardwood at 51-55 °C. We describe organism and bioprocess development efforts undertaken to improve ethanol production. The final strain M2886 was generated by removing genes for exopolysaccharide synthesis, the regulator perR, and re-introduction of phosphotransacetylase and acetate kinase into the methyglyoxal synthase gene. It was also subject to multiple rounds of adaptation and selection, resulting in mutations later identified by resequencing. The highest ethanol titer achieved was 70 g/L in batch culture with a mixture of cellobiose and maltodextrin. In a "mock hydrolysate" Simultaneous Saccharification and Fermentation (SSF) with Sigmacell-20, glucose, xylose, and acetic acid, an ethanol titer of 61 g/L was achieved, at 92 % of theoretical yield. Fungal cellulases were rapidly inactivated under these conditions and had to be supplemented with cellulosomes from C. thermocellum. Ethanol titers of 31 g/L were reached in a 100 L SSF of pre-treated hardwood and 26 g/L in a fermentation of a hardwood hemicellulose extract. CONCLUSIONS This study demonstrates that thermophilic anaerobes are capable of producing ethanol at high yield and at titers greater than 60 g/L from purified substrates, but additional work is needed to produce the same ethanol titers from pre-treated hardwood.
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Affiliation(s)
- Christopher D. Herring
- />Mascoma Corporation, 67 Etna Rd, Lebanon, NH 03766 USA
- />Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA
| | - William R. Kenealy
- />Mascoma Corporation, 67 Etna Rd, Lebanon, NH 03766 USA
- />Verdezyne, Carlsbad, CA USA
| | - A. Joe Shaw
- />Mascoma Corporation, 67 Etna Rd, Lebanon, NH 03766 USA
- />Novogy Inc, Cambridge, MA 02138 USA
| | | | - Daniel G. Olson
- />Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA
- />Bioenergy Science Center, Oak Ridge, TN USA
| | - Jiayi Zhang
- />Mascoma Corporation, 67 Etna Rd, Lebanon, NH 03766 USA
- />Genzyme, Cambridge, MA USA
| | - W. Ryan Sillers
- />Mascoma Corporation, 67 Etna Rd, Lebanon, NH 03766 USA
- />Myriant Corporation, Quincy, MA USA
| | - Vasiliki Tsakraklides
- />Mascoma Corporation, 67 Etna Rd, Lebanon, NH 03766 USA
- />Novogy Inc, Cambridge, MA 02138 USA
| | | | | | | | - Jessica P. Johnson
- />Mascoma Corporation, 67 Etna Rd, Lebanon, NH 03766 USA
- />Washington, DC, USA
| | - Abigail Foster
- />Mascoma Corporation, 67 Etna Rd, Lebanon, NH 03766 USA
| | - Indraneel D. Shikhare
- />Mascoma Corporation, 67 Etna Rd, Lebanon, NH 03766 USA
- />Nalco Champion, Houston, TX USA
| | - Dawn M. Klingeman
- />Bioenergy Science Center, Oak Ridge, TN USA
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | - Steven D. Brown
- />Bioenergy Science Center, Oak Ridge, TN USA
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | - Brian H. Davison
- />Bioenergy Science Center, Oak Ridge, TN USA
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | - Lee R. Lynd
- />Mascoma Corporation, 67 Etna Rd, Lebanon, NH 03766 USA
- />Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA
- />Bioenergy Science Center, Oak Ridge, TN USA
| | - David A. Hogsett
- />Mascoma Corporation, 67 Etna Rd, Lebanon, NH 03766 USA
- />Novozymes Inc, Davis, CA USA
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Cofactor Specificity of the Bifunctional Alcohol and Aldehyde Dehydrogenase (AdhE) in Wild-Type and Mutant Clostridium thermocellum and Thermoanaerobacterium saccharolyticum. J Bacteriol 2015; 197:2610-9. [PMID: 26013492 DOI: 10.1128/jb.00232-15] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 05/21/2015] [Indexed: 02/07/2023] Open
Abstract
UNLABELLED Clostridium thermocellum and Thermoanaerobacterium saccharolyticum are thermophilic bacteria that have been engineered to produce ethanol from the cellulose and hemicellulose fractions of biomass, respectively. Although engineered strains of T. saccharolyticum produce ethanol with a yield of 90% of the theoretical maximum, engineered strains of C. thermocellum produce ethanol at lower yields (∼50% of the theoretical maximum). In the course of engineering these strains, a number of mutations have been discovered in their adhE genes, which encode both alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) enzymes. To understand the effects of these mutations, the adhE genes from six strains of C. thermocellum and T. saccharolyticum were cloned and expressed in Escherichia coli, the enzymes produced were purified by affinity chromatography, and enzyme activity was measured. In wild-type strains of both organisms, NADH was the preferred cofactor for both ALDH and ADH activities. In high-ethanol-producing (ethanologen) strains of T. saccharolyticum, both ALDH and ADH activities showed increased NADPH-linked activity. Interestingly, the AdhE protein of the ethanologenic strain of C. thermocellum has acquired high NADPH-linked ADH activity while maintaining NADH-linked ALDH and ADH activities at wild-type levels. When single amino acid mutations in AdhE that caused increased NADPH-linked ADH activity were introduced into C. thermocellum and T. saccharolyticum, ethanol production increased in both organisms. Structural analysis of the wild-type and mutant AdhE proteins was performed to provide explanations for the cofactor specificity change on a molecular level. IMPORTANCE This work describes the characterization of the AdhE enzyme from different strains of C. thermocellum and T. saccharolyticum. C. thermocellum and T. saccharolyticum are thermophilic anaerobes that have been engineered to make high yields of ethanol and can solubilize components of plant biomass and ferment the sugars to ethanol. In the course of engineering these strains, several mutations arose in the bifunctional ADH/ALDH protein AdhE, changing both enzyme activity and cofactor specificity. We show that changing AdhE cofactor specificity from mostly NADH linked to mostly NADPH linked resulted in higher ethanol production by C. thermocellum and T. saccharolyticum.
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