Biofuels: Biomolecular Engineering Fundamentals and Advances

Li, Han; Cann, Anthony F.; Liao, James C.

doi:10.1146/annurev-chembioeng-073009-100938

Cited by 62 publications

(40 citation statements)

References 110 publications

(169 reference statements)

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“…(6), and artemisinin (via mevalonate) in Saccharomyces cerevisiae (7). Key metrics in determining the likelihood of commercial viability, particularly when targeting terpenes valued within the range of commodity chemicals or biofuels, are yield, productivity, and titer (8,9). Of the two metabolic routes, the DXP pathway is considered the better option from the viewpoint of pathway efficiencyfor example, the theoretical maximum yield of isoprene from glucose is around 20% higher when synthesized via DXP instead of mevalonate (9,10).…”

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confidence: 99%

“…Key metrics in determining the likelihood of commercial viability, particularly when targeting terpenes valued within the range of commodity chemicals or biofuels, are yield, productivity, and titer (8,9). Of the two metabolic routes, the DXP pathway is considered the better option from the viewpoint of pathway efficiencyfor example, the theoretical maximum yield of isoprene from glucose is around 20% higher when synthesized via DXP instead of mevalonate (9,10). In considering production of terpenes from hemicellulosic feedstocks, conversion efficiencies of pentoses, predominantly xylose and arabinose, should also be taken into account (11).…”

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Enhancing Terpene Yield from Sugars via Novel Routes to 1-Deoxy- d -Xylulose 5-Phosphate

Kirby

Nishimoto

Chow

et al. 2015

Appl Environ Microbiol

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Terpene synthesis in the majority of bacterial species, together with plant plastids, takes place via the 1-deoxy-D-xylulose 5-phosphate (DXP) pathway. The first step of this pathway involves the condensation of pyruvate and glyceraldehyde 3-phosphate by DXP synthase (Dxs), with one-sixth of the carbon lost as CO 2 . A hypothetical novel route from a pentose phosphate to DXP (nDXP) could enable a more direct pathway from C 5 sugars to terpenes and also circumvent regulatory mechanisms that control Dxs, but there is no enzyme known that can convert a sugar into its 1-deoxy equivalent. Employing a selection for complementation of a dxs deletion in Escherichia coli grown on xylose as the sole carbon source, we uncovered two candidate nDXP genes. Complementation was achieved either via overexpression of the wild-type E. coli yajO gene, annotated as a putative xylose reductase, or via various mutations in the native ribB gene. In vitro analysis performed with purified YajO and mutant RibB proteins revealed that DXP was synthesized in both cases from ribulose 5-phosphate (Ru5P). We demonstrate the utility of these genes for microbial terpene biosynthesis by engineering the DXP pathway in E. coli for production of the sesquiterpene bisabolene, a candidate biodiesel. To further improve flux into the pathway from Ru5P, nDXP enzymes were expressed as fusions to DXP reductase (Dxr), the second enzyme in the DXP pathway. Expression of a Dxr-RibB(G108S) fusion improved bisabolene titers more than 4-fold and alleviated accumulation of intracellular DXP.T erpenes constitute a very large family of natural products, members of which are produced in virtually all free-living organisms (1). The diverse array of structures within the terpene family is reflected by the variety of applications in society, ranging from nutrition (carotenoids) and medicine (artemisinin, paclitaxel [originally taxol]) to industrial materials (isoprene, linalool) and candidate biofuels (farnesene, bisabolene, pinene) (2). Terpenes can be synthesized via either the mevalonate pathway or the 1-deoxy-D-xylulose 5-phosphate (DXP) pathway, the former predominating in the eukaryotic cytosol and the latter in plastids, while prokaryotes may contain either pathway or, in some cases, both pathways (3).Commercial-scale terpene production has been demonstrated in a variety of organisms, for example, carotenoids (via the DXP pathway) in algae (4, 5), paclitaxel (via DXP) in Taxus sp. (6), and artemisinin (via mevalonate) in Saccharomyces cerevisiae (7). Key metrics in determining the likelihood of commercial viability, particularly when targeting terpenes valued within the range of commodity chemicals or biofuels, are yield, productivity, and titer (8, 9). Of the two metabolic routes, the DXP pathway is considered the better option from the viewpoint of pathway efficiencyfor example, the theoretical maximum yield of isoprene from glucose is around 20% higher when synthesized via DXP instead of mevalonate (9, 10). In considering production of terpenes from hemicellul...

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confidence: 99%

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confidence: 99%

Enhancing Terpene Yield from Sugars via Novel Routes to 1-Deoxy- d -Xylulose 5-Phosphate

Kirby

Nishimoto

Chow

et al. 2015

Appl Environ Microbiol

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“…Also, it is important to identify reduced power sources as substrates, which may be carbohydrates, glycerol, H 2 , CO, methane, methanol, electricity and so on. For example, butanol production based on glucose is spontaneous (i.e., delta G b0) mainly due to a negative enthalpy (Li et al, 2010). In contrast, methane generation from acetate occurs spontaneously due to a gain of entropy but a positive enthalpy (Thauer et al, 1977;Zhang, 2011a).…”

Section: General Design Principlesmentioning

confidence: 99%

Production of biofuels and biochemicals by in vitro synthetic biosystems: Opportunities and challenges

Zhang

2015

Biotechnology Advances

162

101

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The largest obstacle to the cost-competitive production of low-value and high-impact biofuels and biochemicals (called biocommodities) is high production costs catalyzed by microbes due to their inherent weaknesses, such as low product yield, slow reaction rate, high separation cost, intolerance to toxic products, and so on. This predominant whole-cell platform suffers from a mismatch between the primary goal of living microbes - cell proliferation and the desired biomanufacturing goal - desired products (not cell mass most times). In vitro synthetic biosystems consist of numerous enzymes as building bricks, enzyme complexes as building modules, and/or (biomimetic) coenzymes, which are assembled into synthetic enzymatic pathways for implementing complicated bioreactions. They emerge as an alternative solution for accomplishing a desired biotransformation without concerns of cell proliferation, complicated cellular regulation, and side-product formation. In addition to the most important advantage - high product yield, in vitro synthetic biosystems feature several other biomanufacturing advantages, such as fast reaction rate, easy product separation, open process control, broad reaction condition, tolerance to toxic substrates or products, and so on. In this perspective review, the general design rules of in vitro synthetic pathways are presented with eight supporting examples: hydrogen, n-butanol, isobutanol, electricity, starch, lactate,1,3-propanediol, and poly-3-hydroxylbutyrate. Also, a detailed economic analysis for enzymatic hydrogen production from carbohydrates is presented to illustrate some advantages of this system and the remaining challenges. Great market potentials will motivate worldwide efforts from multiple disciplines (i.e., chemistry, biology and engineering) to address the remaining obstacles pertaining to cost and stability of enzymes and coenzymes, standardized building parts and modules, biomimetic coenzymes, biosystem optimization, and scale-up, soon.

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“…Biochemical routes using hydrolysis to produce aqueous sugars and then fermentation to produce alcohols and other chemicals are described in an extensive body of literature (4,5,7,58,59). Basically, in this process the cellulose and hemicellulose components of the biomass are broken into individual sugars in the presence of excess water, acids, bases, or enzymes.…”

Section: Figurementioning

confidence: 99%

Solar Energy to Biofuels

Agrawal

Singh

2010

Annu. Rev. Chem. Biomol. Eng.

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In a solar economy, sustainably available biomass holds the potential to be an excellent nonfossil source of high energy density transportation fuel. However, if sustainably available biomass cannot supply the liquid fuel need for the entire transport sector, alternatives must be sought. This article reviews biomass to liquid fuel conversion processes that treat biomass primarily as a carbon source and boost liquid fuel production substantially by using supplementary energy that is recovered from solar energy at much higher efficiencies than the biomass itself. The need to develop technologies for an energy-efficient future sustainable transport sector infrastructure that will use different forms of energy, such as electricity, H(2), and heat, in a synergistic interaction with each other is emphasized. An enabling template for such a future transport infrastructure is presented. An advantage of the use of such a template is that it reduces the land area needed to propel an entire transport sector. Also, some solutions for the transition period that synergistically combine biomass with fossil fuels are briefly discussed.

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Biofuels: Biomolecular Engineering Fundamentals and Advances

Cited by 62 publications

References 110 publications

Enhancing Terpene Yield from Sugars via Novel Routes to 1-Deoxy- d -Xylulose 5-Phosphate

Enhancing Terpene Yield from Sugars via Novel Routes to 1-Deoxy- d -Xylulose 5-Phosphate

Production of biofuels and biochemicals by in vitro synthetic biosystems: Opportunities and challenges

Solar Energy to Biofuels

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