Archive for December 4th, 2010

New Mexico Makes Plan to Ramp Up Renewable Energy Exports With Tres Amigas


A report from a 26 member task force, appointed by outgoing New Mexico Governor Bill Richardson, offers pointers on how to boost state independence with a major renewable energy transmission expansion, capitalizing on the Tres Amigas super station. The report spells out ten steps New Mexico can take to expand the grid to make it possible to export renewable energy.

“We have a renewable energy potential around 27,000 MW, the second-best solar resource in the nation, and a wind resource in the top 10 of states, but are unable to fully develop that potential because we do not have the transmission infrastructure to get the renewable energy from its point of generation to the grid,” Jim Noel, Secretary of the New Mexico Energy, Minerals and Natural Resources Department told Energy Prospects West.

One recommendation is to make the state’s Renewable Energy Transmission Authority (RETA) an independent transmission planning authority for all lines greater than 240 KV, to make it easier for it to assert eminent domain authority, and to increase its funding to at least $1 million a year. A five cents per megawatt charge would fund the change.

Los Alamos National Laboratory (LANL) also produced findings for the study, but fell short. The task force found it not broad enough, by failing to account for the markets North or East. That plan would export less too; a mere 5,200 MW of renewable energy.

Nor did LANL consider the Tres Amigas project, or that forming a Smart Grid-enabled network could move renewable energy all over the country. “There’s a market for wind from New Mexico to Texas and Oklahoma,” said David Stidham, Tres Amigas COO.

Tres Amigas, under review in New Mexico now, and slated to go online in 2014, is a proposed transmission super station centrally located where the three major US grids could be connected, at Clovis, a mile from the Texas border.

It is by far is the most ambitious renewable energy transmission project to date, nationwide. It would interconnect the country’s three primary power grids with high-capacity AC/DC voltage source converters and could be expanded to handle up to 30 Gigawatts of power.

Image: Dave Clark
Susan Kraemer@Twitter


Visit the original post at: Energy News

New Mexico Makes Plan to Ramp Up Renewable Energy Exports With Tres Amigas


A report from a 26 member task force, appointed by outgoing New Mexico Governor Bill Richardson, offers pointers on how to boost state independence with a major renewable energy transmission expansion, capitalizing on the Tres Amigas super station. The report spells out ten steps New Mexico can take to expand the grid to make it possible to export renewable energy.

“We have a renewable energy potential around 27,000 MW, the second-best solar resource in the nation, and a wind resource in the top 10 of states, but are unable to fully develop that potential because we do not have the transmission infrastructure to get the renewable energy from its point of generation to the grid,” Jim Noel, Secretary of the New Mexico Energy, Minerals and Natural Resources Department told Energy Prospects West.

One recommendation is to make the state’s Renewable Energy Transmission Authority (RETA) an independent transmission planning authority for all lines greater than 240 KV, to make it easier for it to assert eminent domain authority, and to increase its funding to at least $1 million a year. A five cents per megawatt charge would fund the change.

Los Alamos National Laboratory (LANL) also produced findings for the study, but fell short. The task force found it not broad enough, by failing to account for the markets North or East. That plan would export less too; a mere 5,200 MW of renewable energy.

Nor did LANL consider the Tres Amigas project, or that forming a Smart Grid-enabled network could move renewable energy all over the country. “There’s a market for wind from New Mexico to Texas and Oklahoma,” said David Stidham, Tres Amigas COO.

Tres Amigas, under review in New Mexico now, and slated to go online in 2014, is a proposed transmission super station centrally located where the three major US grids could be connected, at Clovis, a mile from the Texas border.

It is by far is the most ambitious renewable energy transmission project to date, nationwide. It would interconnect the country’s three primary power grids with high-capacity AC/DC voltage source converters and could be expanded to handle up to 30 Gigawatts of power.

Image: Dave Clark
Susan Kraemer@Twitter


Visit the original post at: Energy News

New Mexico Makes Plan to Ramp Up Renewable Energy Exports With Tres Amigas


A report from a 26 member task force, appointed by outgoing New Mexico Governor Bill Richardson, offers pointers on how to boost state independence with a major renewable energy transmission expansion, capitalizing on the Tres Amigas super station. The report spells out ten steps New Mexico can take to expand the grid to make it possible to export renewable energy.

“We have a renewable energy potential around 27,000 MW, the second-best solar resource in the nation, and a wind resource in the top 10 of states, but are unable to fully develop that potential because we do not have the transmission infrastructure to get the renewable energy from its point of generation to the grid,” Jim Noel, Secretary of the New Mexico Energy, Minerals and Natural Resources Department told Energy Prospects West.

One recommendation is to make the state’s Renewable Energy Transmission Authority (RETA) an independent transmission planning authority for all lines greater than 240 KV, to make it easier for it to assert eminent domain authority, and to increase its funding to at least $1 million a year. A five cents per megawatt charge would fund the change.

Los Alamos National Laboratory (LANL) also produced findings for the study, but fell short. The task force found it not broad enough, by failing to account for the markets North or East. That plan would export less too; a mere 5,200 MW of renewable energy.

Nor did LANL consider the Tres Amigas project, or that forming a Smart Grid-enabled network could move renewable energy all over the country. “There’s a market for wind from New Mexico to Texas and Oklahoma,” said David Stidham, Tres Amigas COO.

Tres Amigas, under review in New Mexico now, and slated to go online in 2014, is a proposed transmission super station centrally located where the three major US grids could be connected, at Clovis, a mile from the Texas border.

It is by far is the most ambitious renewable energy transmission project to date, nationwide. It would interconnect the country’s three primary power grids with high-capacity AC/DC voltage source converters and could be expanded to handle up to 30 Gigawatts of power.

Image: Dave Clark
Susan Kraemer@Twitter


Visit the original post at: Energy News

Bioplastics Not Necessarily the Greenest
bioplastics

Bioplastics would seem to be a positive development in many ways. Rather than needing to have petroleum extracted and processed to supply the feedstock for making plastic, plant-based materials are used instead. However, a study by University of Pittsburgh researchers finds that plant-based plastics are not necessarily greener than petroleum-based ones.

To reach this conclusion, the researchers looked at several life-cycle factors. Factoring in side effects of farming needed to produce the feedstock needed to produce bioplastics, there are issues such as eutrophication of waterways, ozone depletion, and even carcinogens where some bioplastics fared poorly.

Twelve different plastics were evaluated in the study. In addition to the life cycle analysis, the plastics were also ranked according to green design principles. The production of some petroleum plastics had a better score than the bioplastics did. “Once in use, however, biopolymers bested traditional polymers for ecofriendliness.” Polypropolene, for example, dropped from 1st place for production to 9th place as a sustainable material.

Each polymer is also assessed for its adherence to green design principles using metrics generated specifically for this paper. Metrics include atom economy, mass from renewable sources, biodegradability, percent recycled, distance of furthest feedstock, price, life cycle health hazards and life cycle energy use. A decision matrix is used to generate single value metrics for each polymer evaluating either adherence to green design principles or life-cycle environmental impacts. Results from this study show a qualified positive correlation between adherence to green design principles and a reduction of the environmental impacts of production. The qualification results from a disparity between biopolymers and petroleum polymers. While biopolymers rank highly in terms of green design, they exhibit relatively large environmental impacts from production.

It should be pointed out that this study is based on current methods of production. So, while the bioplastics are not necessarily the greenest option at present, improved production practices could improve their relative ranking. Farming methods that reduce fertilizer use could help decrease the eutrophication scores, for example.

The results of this study should not necessarily be used to bash bioplastics or to make the contrarian argument that petroleum ought to continue to be used. Petroleum is, after all, a finite resource, and alternative stocks will eventually need to be embraced. Producers of both petroleum-based plastics and bioplastics could work with this study to identify the most damaging aspects of their methods in order to reduce their environmental impacts.

via: Building Green


Visit the original post at: EcoGeek.org

Bioplastics Not Necessarily the Greenest
bioplastics

Bioplastics would seem to be a positive development in many ways. Rather than needing to have petroleum extracted and processed to supply the feedstock for making plastic, plant-based materials are used instead. However, a study by University of Pittsburgh researchers finds that plant-based plastics are not necessarily greener than petroleum-based ones.

To reach this conclusion, the researchers looked at several life-cycle factors. Factoring in side effects of farming needed to produce the feedstock needed to produce bioplastics, there are issues such as eutrophication of waterways, ozone depletion, and even carcinogens where some bioplastics fared poorly.

Twelve different plastics were evaluated in the study. In addition to the life cycle analysis, the plastics were also ranked according to green design principles. The production of some petroleum plastics had a better score than the bioplastics did. “Once in use, however, biopolymers bested traditional polymers for ecofriendliness.” Polypropolene, for example, dropped from 1st place for production to 9th place as a sustainable material.

Each polymer is also assessed for its adherence to green design principles using metrics generated specifically for this paper. Metrics include atom economy, mass from renewable sources, biodegradability, percent recycled, distance of furthest feedstock, price, life cycle health hazards and life cycle energy use. A decision matrix is used to generate single value metrics for each polymer evaluating either adherence to green design principles or life-cycle environmental impacts. Results from this study show a qualified positive correlation between adherence to green design principles and a reduction of the environmental impacts of production. The qualification results from a disparity between biopolymers and petroleum polymers. While biopolymers rank highly in terms of green design, they exhibit relatively large environmental impacts from production.

It should be pointed out that this study is based on current methods of production. So, while the bioplastics are not necessarily the greenest option at present, improved production practices could improve their relative ranking. Farming methods that reduce fertilizer use could help decrease the eutrophication scores, for example.

The results of this study should not necessarily be used to bash bioplastics or to make the contrarian argument that petroleum ought to continue to be used. Petroleum is, after all, a finite resource, and alternative stocks will eventually need to be embraced. Producers of both petroleum-based plastics and bioplastics could work with this study to identify the most damaging aspects of their methods in order to reduce their environmental impacts.

via: Building Green


Visit the original post at: EcoGeek.org

The Popemobile May Go Solar

The Popemobile May Go Solar

popemobile
The Vatican has made headlines with its eagerness to embrace solar power and renewable energy efforts in general.  Adding to that, Wednesday, the Vatican announced that the Pope was interested in replacing his gas-fueled Popemobile, with a solar-powered one.

Already the Vatican’s main auditorium is covered with a large rooftop solar array and the cafeteria is cooled by a solar cooling unit.  Also, in the works is a 100-MW solar facility on Vatican land outside of Rome.

That just leaves the Popemobile, currently a bullet-proof Mercedes Benz.  Apparently all the Vatican is waiting on to replace it is an auto company willing to build a solar-powered version (complete with the extreme security features).  I’ll be interested to see who jumps at the chance.

via Mother Nature Network


Visit the original post at: EcoGeek.org

The Popemobile May Go Solar

The Popemobile May Go Solar

popemobile
The Vatican has made headlines with its eagerness to embrace solar power and renewable energy efforts in general.  Adding to that, Wednesday, the Vatican announced that the Pope was interested in replacing his gas-fueled Popemobile, with a solar-powered one.

Already the Vatican’s main auditorium is covered with a large rooftop solar array and the cafeteria is cooled by a solar cooling unit.  Also, in the works is a 100-MW solar facility on Vatican land outside of Rome.

That just leaves the Popemobile, currently a bullet-proof Mercedes Benz.  Apparently all the Vatican is waiting on to replace it is an auto company willing to build a solar-powered version (complete with the extreme security features).  I’ll be interested to see who jumps at the chance.

via Mother Nature Network


Visit the original post at: EcoGeek.org

The Popemobile May Go Solar

The Popemobile May Go Solar

popemobile
The Vatican has made headlines with its eagerness to embrace solar power and renewable energy efforts in general.  Adding to that, Wednesday, the Vatican announced that the Pope was interested in replacing his gas-fueled Popemobile, with a solar-powered one.

Already the Vatican’s main auditorium is covered with a large rooftop solar array and the cafeteria is cooled by a solar cooling unit.  Also, in the works is a 100-MW solar facility on Vatican land outside of Rome.

That just leaves the Popemobile, currently a bullet-proof Mercedes Benz.  Apparently all the Vatican is waiting on to replace it is an auto company willing to build a solar-powered version (complete with the extreme security features).  I’ll be interested to see who jumps at the chance.

via Mother Nature Network


Visit the original post at: EcoGeek.org

The Popemobile May Go Solar

The Popemobile May Go Solar

popemobile
The Vatican has made headlines with its eagerness to embrace solar power and renewable energy efforts in general.  Adding to that, Wednesday, the Vatican announced that the Pope was interested in replacing his gas-fueled Popemobile, with a solar-powered one.

Already the Vatican’s main auditorium is covered with a large rooftop solar array and the cafeteria is cooled by a solar cooling unit.  Also, in the works is a 100-MW solar facility on Vatican land outside of Rome.

That just leaves the Popemobile, currently a bullet-proof Mercedes Benz.  Apparently all the Vatican is waiting on to replace it is an auto company willing to build a solar-powered version (complete with the extreme security features).  I’ll be interested to see who jumps at the chance.

via Mother Nature Network


Visit the original post at: EcoGeek.org

Putin opts out of helping Russia’s World Cup bid
Putin’s withdrawal Wednesday and allegation that the bidding process had turned into an “unfair competition” following scandals targeting FIFA dented its stature as a favorite to host the event.
Visit the original post at: TMCnet-News

Putin opts out of helping Russia’s World Cup bid
Putin’s withdrawal Wednesday and allegation that the bidding process had turned into an “unfair competition” following scandals targeting FIFA dented its stature as a favorite to host the event.
Visit the original post at: TMCnet-News

Senate to vote on Democratic tax cut plans
Republicans dismissed the attacks as the last gasp of a party that lost its majority in the House of Representatives in the November elections, surrendered several seats in the Senate and will be forced to share power beginning in January.
Visit the original post at: TMCnet-News

Keasling: metabolic engineering will soon rival and potentially eclipse synthetic organic chemistry; designer cells for fuels and chemicals

Keasling2
The future of engineered biocatalysts. Pathways, enzymes, and genetic controls are designed from characteristics of parts. The chromosomes encoding those elements are synthesized and incorporated into a ghost envelope to obtain the new catalyst. The design of the engineered catalyst is influenced by the desired product and the production process. Credit: AAAS, Keasling. Click to enlarge.

In a paper published in the 3 December issue of the journal Science titled “Manufacturing molecules through metabolic engineering,” Dr. Jay Keasling discusses the potential of metabolic engineering for the microbial production from simple, readily available, inexpensive starting materials of a large number of chemicals that are currently derived from nonrenewable resources or limited natural resources. Examples include, among a great many other possibilities, the replacement of gasoline and other transportation fuels with renewable biofuels. (Earlier post.)

Keasling is the chief executive officer for the Joint BioEnergy Institute, a US Department of Energy (DOE) bioenergy research center. He also holds joint appointments with the Lawrence Berkeley National Laboratory (Berkeley Lab), where he oversees that institute’s biosciences research programs, and the University of California (UC), Berkeley, where he serves as director of the Synthetic Biology Engineering Research Center, and is the Hubbard Howe Jr. Distinguished Professor of Biochemical Engineering.

Keasling recently was inducted into the National Academy of Engineering. He is also co-founder of Amyris Biotechnologies, a bioenergy startup which recently went public.

Metabolic engineering is the practice of altering genes and metabolic pathways within a cell or microorganism to increase its production of a specific substance. In the review in Science, Keasling notes that even with the substantial development of tools for metabolic engineering, and that metabolic engineers must weigh many trade-offs in the development of microbial catalysts:

  1. cost and availability of starting materials (e.g., carbon substrates);
  2. metabolic route and corresponding genes encoding the enzymes in the pathway to produce the desired product;
  3. most appropriate microbial host;
  4. robust and responsive genetic control system for the desired pathways and chosen host;
  5. methods for debugging and debottlenecking the constructed pathway; and
  6. ways to maximize yields, titers, and productivities.

Unfortunately, these design decisions cannot be made independently of each other: Genes cannot be expressed, nor will the resulting enzymes function, in every host; products or metabolic intermediates may be toxic to one host but not another host; different hosts have different levels of sophistication of genetic tools available; and processing conditions (e.g., growth, production, product separation and purification) are not compatible with all hosts. Even with these many challenges, metabolic engineering has been successful for many applications, and with continued developments more applications will be possible.

One area where metabolic engineering has a sizable advantage over synthetic organic chemistry is in the production of natural products, particularly active pharmaceutical ingredients (APIs), some of which are too complex to be chemically synthesized and yet have a value that justifies the cost of developing a genetically engineered microorganism. The cost of starting materials is generally a small fraction of their cost, and relatively little starting material is necessary so availability is not an issue. Most APIs fall into three classes of natural products, and many of the biosynthetic pathways for their precursors have been reconstituted in heterologous hosts.

—Jay Keasling

These three classes are: alkaloids; polyketides and nonribosomal peptides (NRPs); and isoprenoids. Keasling notes that bulk chemicals such as solvents and polymer precursors currently are rarely produced from microorganisms, because they can be produced inexpensively from petroleum by chemical catalysis. However, he adds, due to fluctuations in petroleum prices and recognition of dwindling reserves, trade imbalances, and political considerations, “it is now possible to consider production of these inexpensive chemicals from low-cost starting materials such as starch, sucrose, or cellulosic biomass (e.g., agricultural and forest waste, dedicated energy crops, etc.) with a microbial catalyst”. The key to producing bulk chemicals (e.g., polymer precursors) by using metabolically engineered cells will be to produce the exact molecule needed for existing products rather than something “similar but green” that will require extensive product testing before it can be used.

By far the highest-volume (and lowest-margin) application for engineered metabolism is the production of transportation fuels…Recent advances in metabolic pathway and protein engineering have made it possible to engineer microorganisms to produce hydrocarbons with properties similar or identical to those of petroleum-derived fuels and thus compatible with our existing transportation infrastructure. Linear hydrocarbons (alkanes, alkenes, and esters) typical of diesel and jet fuel can be produced by way of the fatty acid biosynthetic pathway. For diesel in cold weather and jet fuel at high altitudes, branches in the chain are beneficial—regularly branched and cyclic hydrocarbons of different sizes with diverse structural and chemical properties can be produced via the isoprenoid biosynthetic pathway. Both the fatty acid–derived and the isoprenoid-derived fuels diffuse (or are pumped) out of the engineered cells and phase separate in the fermentation, making purification simple and reducing fuel cost.

Although the pathways described above produce a wide range of fuel-like molecules, there are many other molecules that one might want to produce, such as short, highly branched hydrocarbons (e.g., 2,2,4-trimethyl pentane or isooctane) that would be excellent substitutes for petroleum-derived gasoline. Additionally, most petroleum fuels are mixtures of large numbers of components that together create the many important properties of the fuels. It should be possible to engineer single microbes or microbial consortia to produce a mixture of fuels from one of the biosynthetic pathways or from multiple biosynthetic pathways. Indeed, some enzymes produce mixtures of products from a single precursor—maybe these enzymes could be tuned to produce a fuel mixture ideal for a particular engine type or climate.

To make these new fuels economically viable, we must tap into inexpensive carbon sources (namely, sugars from cellulosic biomass). Given the variety of sugars in cellulosic biomass, the fuel producer must be able to consume both five- and six-carbon sugars. Because many yeasts do not consume five-carbon sugars, recent developments in engineering yeast to catabolize these sugars will make production of these fuels more economically viable. Engineering fuel-producing microorganisms to secrete cellulases and hemicellulases to depolymerize these sugar polymers into sugars before uptake and conversion into fuels has the potential to substantially reduce the cost of producing the fuel.

—Jay Keasling

In the paper, Keasling discusses the roadblocks that stand in the way of a future in which microorganisms and molecules can be tailor-made through metabolic engineering, including the need for debugging routines that can find and fix errors in engineered cells. However, he is convinced these roadblocks can and will be overcome.

One can even envision a day when cell manufacturing is done by different companies, each specializing in certain aspects of the synthesis—one company constructs the chromosome, one company builds the membrane and cell wall (the “bag”), one company fills the bag with the basic molecules needed to boot up the cell.

Until this future arrives, manufacturing of molecules will be done with well-known, safe, industrial microorganisms that have tractable genetic systems. Continued development of tools for existing, safe, industrial hosts, cloning and expressing genes encoding precursor production pathways, and the creation of novel enzymes that catalyze unnatural reactions will be necessary to expand the range of products that can be produced from biological systems. When more of these tools are available, metabolic engineering should be just as powerful as synthetic chemistry, and together the two disciplines can greatly expand the number of products available from renewable resources.

—Jay Keasling

Resources

  • Jay D. Keasling (2010) Manufacturing Molecules Through Metabolic Engineering. Science Vol. 330 no. 6009 pp. 1355-1358 doi: 10.1126/science.1193990


Visit the original post at: Transportation News

Keasling: metabolic engineering will soon rival and potentially eclipse synthetic organic chemistry; designer cells for fuels and chemicals

Keasling2
The future of engineered biocatalysts. Pathways, enzymes, and genetic controls are designed from characteristics of parts. The chromosomes encoding those elements are synthesized and incorporated into a ghost envelope to obtain the new catalyst. The design of the engineered catalyst is influenced by the desired product and the production process. Credit: AAAS, Keasling. Click to enlarge.

In a paper published in the 3 December issue of the journal Science titled “Manufacturing molecules through metabolic engineering,” Dr. Jay Keasling discusses the potential of metabolic engineering for the microbial production from simple, readily available, inexpensive starting materials of a large number of chemicals that are currently derived from nonrenewable resources or limited natural resources. Examples include, among a great many other possibilities, the replacement of gasoline and other transportation fuels with renewable biofuels. (Earlier post.)

Keasling is the chief executive officer for the Joint BioEnergy Institute, a US Department of Energy (DOE) bioenergy research center. He also holds joint appointments with the Lawrence Berkeley National Laboratory (Berkeley Lab), where he oversees that institute’s biosciences research programs, and the University of California (UC), Berkeley, where he serves as director of the Synthetic Biology Engineering Research Center, and is the Hubbard Howe Jr. Distinguished Professor of Biochemical Engineering.

Keasling recently was inducted into the National Academy of Engineering. He is also co-founder of Amyris Biotechnologies, a bioenergy startup which recently went public.

Metabolic engineering is the practice of altering genes and metabolic pathways within a cell or microorganism to increase its production of a specific substance. In the review in Science, Keasling notes that even with the substantial development of tools for metabolic engineering, and that metabolic engineers must weigh many trade-offs in the development of microbial catalysts:

  1. cost and availability of starting materials (e.g., carbon substrates);
  2. metabolic route and corresponding genes encoding the enzymes in the pathway to produce the desired product;
  3. most appropriate microbial host;
  4. robust and responsive genetic control system for the desired pathways and chosen host;
  5. methods for debugging and debottlenecking the constructed pathway; and
  6. ways to maximize yields, titers, and productivities.

Unfortunately, these design decisions cannot be made independently of each other: Genes cannot be expressed, nor will the resulting enzymes function, in every host; products or metabolic intermediates may be toxic to one host but not another host; different hosts have different levels of sophistication of genetic tools available; and processing conditions (e.g., growth, production, product separation and purification) are not compatible with all hosts. Even with these many challenges, metabolic engineering has been successful for many applications, and with continued developments more applications will be possible.

One area where metabolic engineering has a sizable advantage over synthetic organic chemistry is in the production of natural products, particularly active pharmaceutical ingredients (APIs), some of which are too complex to be chemically synthesized and yet have a value that justifies the cost of developing a genetically engineered microorganism. The cost of starting materials is generally a small fraction of their cost, and relatively little starting material is necessary so availability is not an issue. Most APIs fall into three classes of natural products, and many of the biosynthetic pathways for their precursors have been reconstituted in heterologous hosts.

—Jay Keasling

These three classes are: alkaloids; polyketides and nonribosomal peptides (NRPs); and isoprenoids. Keasling notes that bulk chemicals such as solvents and polymer precursors currently are rarely produced from microorganisms, because they can be produced inexpensively from petroleum by chemical catalysis. However, he adds, due to fluctuations in petroleum prices and recognition of dwindling reserves, trade imbalances, and political considerations, “it is now possible to consider production of these inexpensive chemicals from low-cost starting materials such as starch, sucrose, or cellulosic biomass (e.g., agricultural and forest waste, dedicated energy crops, etc.) with a microbial catalyst”. The key to producing bulk chemicals (e.g., polymer precursors) by using metabolically engineered cells will be to produce the exact molecule needed for existing products rather than something “similar but green” that will require extensive product testing before it can be used.

By far the highest-volume (and lowest-margin) application for engineered metabolism is the production of transportation fuels…Recent advances in metabolic pathway and protein engineering have made it possible to engineer microorganisms to produce hydrocarbons with properties similar or identical to those of petroleum-derived fuels and thus compatible with our existing transportation infrastructure. Linear hydrocarbons (alkanes, alkenes, and esters) typical of diesel and jet fuel can be produced by way of the fatty acid biosynthetic pathway. For diesel in cold weather and jet fuel at high altitudes, branches in the chain are beneficial—regularly branched and cyclic hydrocarbons of different sizes with diverse structural and chemical properties can be produced via the isoprenoid biosynthetic pathway. Both the fatty acid–derived and the isoprenoid-derived fuels diffuse (or are pumped) out of the engineered cells and phase separate in the fermentation, making purification simple and reducing fuel cost.

Although the pathways described above produce a wide range of fuel-like molecules, there are many other molecules that one might want to produce, such as short, highly branched hydrocarbons (e.g., 2,2,4-trimethyl pentane or isooctane) that would be excellent substitutes for petroleum-derived gasoline. Additionally, most petroleum fuels are mixtures of large numbers of components that together create the many important properties of the fuels. It should be possible to engineer single microbes or microbial consortia to produce a mixture of fuels from one of the biosynthetic pathways or from multiple biosynthetic pathways. Indeed, some enzymes produce mixtures of products from a single precursor—maybe these enzymes could be tuned to produce a fuel mixture ideal for a particular engine type or climate.

To make these new fuels economically viable, we must tap into inexpensive carbon sources (namely, sugars from cellulosic biomass). Given the variety of sugars in cellulosic biomass, the fuel producer must be able to consume both five- and six-carbon sugars. Because many yeasts do not consume five-carbon sugars, recent developments in engineering yeast to catabolize these sugars will make production of these fuels more economically viable. Engineering fuel-producing microorganisms to secrete cellulases and hemicellulases to depolymerize these sugar polymers into sugars before uptake and conversion into fuels has the potential to substantially reduce the cost of producing the fuel.

—Jay Keasling

In the paper, Keasling discusses the roadblocks that stand in the way of a future in which microorganisms and molecules can be tailor-made through metabolic engineering, including the need for debugging routines that can find and fix errors in engineered cells. However, he is convinced these roadblocks can and will be overcome.

One can even envision a day when cell manufacturing is done by different companies, each specializing in certain aspects of the synthesis—one company constructs the chromosome, one company builds the membrane and cell wall (the “bag”), one company fills the bag with the basic molecules needed to boot up the cell.

Until this future arrives, manufacturing of molecules will be done with well-known, safe, industrial microorganisms that have tractable genetic systems. Continued development of tools for existing, safe, industrial hosts, cloning and expressing genes encoding precursor production pathways, and the creation of novel enzymes that catalyze unnatural reactions will be necessary to expand the range of products that can be produced from biological systems. When more of these tools are available, metabolic engineering should be just as powerful as synthetic chemistry, and together the two disciplines can greatly expand the number of products available from renewable resources.

—Jay Keasling

Resources

  • Jay D. Keasling (2010) Manufacturing Molecules Through Metabolic Engineering. Science Vol. 330 no. 6009 pp. 1355-1358 doi: 10.1126/science.1193990


Visit the original post at: Transportation News

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