Enhancing microbial production of biofuels by expanding microbial metabolic pathways

Yu, Ping; Chen, Xingge

doi:10.1002/bab.1529

Cited by 9 publications

(5 citation statements)

References 180 publications

(149 reference statements)

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“…An alternative CoA-dependent route from threonine to butane was also designed (Additional file 1: Figs. S2-S4), with the initial ilvE step substituted for threonine dehydratase (ilvA) from E. coli [18] and hydrocarbon chain extension performed by the E. coli leuABCD operon [19]. However initial constructs did not produce detectable propane due to the absence of activity of the LeuABCD-catalysed steps (results not shown).…”

Section: Resultsmentioning

confidence: 99%

Renewable and tuneable bio-LPG blends derived from amino acids

Amer

Hoeven

Kelly

et al. 2020

Biotechnol Biofuels

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Background: Microbial biorefinery approaches are beginning to define renewable and sustainable routes to cleanburning and non-fossil fuel-derived gaseous alkanes (known as 'bio-LPG'). The most promising strategies have used a terminal fatty acid photodecarboxylase, enabling light-driven propane production from externally fed waste butyric acid. Use of Halomonas (a robust extremophile microbial chassis) with these pathways has enabled bio-LPG production under non-sterile conditions and using waste biomass as the carbon source. Here, we describe new engineering approaches to produce next-generation pathways that use amino acids as fuel precursors for bio-LPG production (propane, butane and isobutane blends). Results: Multiple pathways from the amino acids valine, leucine and isoleucine were designed in E. coli for the production of propane, isobutane and butane, respectively. A branched-chain keto acid decarboxylase-dependent pathway utilising fatty acid photodecarboxylase was the most effective route, generating higher alkane gas titres over alternative routes requiring coenzyme A and/or aldehyde deformylating oxygenase. Isobutane was the major gas produced in standard (mixed amino acid) medium, however valine supplementation led to primarily propane production. Transitioning pathways into Halomonas strain TQ10 enabled fermentative production of mixed alkane gases under non-sterile conditions on simple carbon sources. Chromosomal integration of inducible (~ 180 mg/g cells/day) and constitutive (~ 30 mg/g cells/day) pathways into Halomonas generated production strains shown to be stable for up to 7 days. Conclusions: This study highlights new microbial pathways for the production of clean-burning bio-LPG fuels from amino acids. The use of stable Halomonas production strains could lead to gas production in the field under nonsterile conditions following process optimisation.

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Section: Resultsmentioning

confidence: 99%

Renewable and tuneable bio-LPG blends derived from amino acids

Amer

Hoeven

Kelly

et al. 2020

Biotechnol Biofuels

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“…This particular reaction is of interest to both human health and biotechnology due to the role of AdhE in the regulation of alcohol metabolism 9 . In addition, ethanol production via AdhE catalysis is widely studied as a prospect for renewable energy production 10,11 . Deletion of adhE is correlated with at least 90% loss of ethanol yield 12 .…”

Section: Introductionmentioning

confidence: 99%

Aldehyde-alcohol dehydrogenase forms a high-order spirosome architecture critical for its activity

et al. 2019

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Aldehyde-alcohol dehydrogenase (AdhE) is a key enzyme in bacterial fermentation, converting acetyl-CoA to ethanol, via two consecutive catalytic reactions. Here, we present a 3.5 Å resolution cryo-EM structure of full-length AdhE revealing a high-order spirosome architecture. The structure shows that the aldehyde dehydrogenase (ALDH) and alcohol dehydrogenase (ADH) active sites reside at the outer surface and the inner surface of the spirosome respectively, thus topologically separating these two activities. Furthermore, mutations disrupting the helical structure abrogate enzymatic activity, implying that formation of the spirosome structure is critical for AdhE activity. In addition, we show that this spirosome structure undergoes conformational change in the presence of cofactors. This work presents the atomic resolution structure of AdhE and suggests that the high-order helical structure regulates its enzymatic activity.

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“…The second proposed route begins with the upregulation of L-threonine dehydratase (ilvA) to deaminate threonine to α-ketobutyrate [72]. Carbon chain elongation then follows two stages to generate α-ketocaproate, catalysed by the isopropyl malate synthase, dehydrogenase & isomerase complex (LeuABCD; [73]) (Fig. 2).…”

Section: Table 3 Microbial Alkane Gas Production Via Amino Acid Biosymentioning

confidence: 99%

Engineering nature for gaseous hydrocarbon production

2020

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The development of sustainable routes to the bio-manufacture of gaseous hydrocarbons will contribute widely to future energy needs. Their realisation would contribute towards minimising over-reliance on fossil fuels, improving air quality, reducing carbon footprints and enhancing overall energy security. Alkane gases (propane, butane and isobutane) are efficient and clean-burning fuels. They are established globally within the transportation industry and are used for domestic heating and cooking, non-greenhouse gas refrigerants and as aerosol propellants. As no natural biosynthetic routes to short chain alkanes have been discovered, de novo pathways have been engineered. These pathways incorporate one of two enzymes, either aldehyde deformylating oxygenase or fatty acid photodecarboxylase, to catalyse the final step that leads to gas formation. These new pathways are derived from established routes of fatty acid biosynthesis, reverse β-oxidation for butanol production, valine biosynthesis and amino acid degradation. Single-step production of alkane gases in vivo is also possible, where one recombinant biocatalyst can catalyse gas formation from exogenously supplied short-chain fatty acid precursors. This review explores current progress in bio-alkane gas production, and highlights the potential for implementation of scalable and sustainable commercial bioproduction hubs.

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Enhancing microbial production of biofuels by expanding microbial metabolic pathways

Cited by 9 publications

References 180 publications

Renewable and tuneable bio-LPG blends derived from amino acids

Renewable and tuneable bio-LPG blends derived from amino acids

Aldehyde-alcohol dehydrogenase forms a high-order spirosome architecture critical for its activity

Engineering nature for gaseous hydrocarbon production

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