Major advance in artificial photosynthesis poses win/win for the environment

April 16, 2015
A major advance in artificial photosynthesis poses win/win for the environment -- using sequestered CO2 for green chemistry, including renewable fuel production. Credit: Caitlin Givens

A potentially game-changing breakthrough in artificial photosynthesis has been achieved with the development of a system that can capture carbon dioxide emissions before they are vented into the atmosphere and then, powered by solar energy, convert that carbon dioxide into valuable chemical products, including biodegradable plastics, pharmaceutical drugs and even liquid fuels.

Scientists with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley have created a hybrid system of semiconducting nanowires and bacteria that mimics the natural photosynthetic process by which plants use the energy in sunlight to synthesize carbohydrates from and water. However, this new artificial photosynthetic system synthesizes the combination of carbon dioxide and water into acetate, the most common building block today for biosynthesis.

"We believe our system is a revolutionary leap forward in the field of ," says Peidong Yang, a chemist with Berkeley Lab's Materials Sciences Division and one of the leaders of this study. "Our system has the potential to fundamentally change the chemical and oil industry in that we can produce chemicals and fuels in a totally renewable way, rather than extracting them from deep below the ground."

Yang, who also holds appointments with UC Berkeley and the Kavli Energy NanoSciences Institute (Kavli-ENSI) at Berkeley, is one of three corresponding authors of a paper describing this research in the journal Nano Letters. The paper is titled "Nanowire-bacteria hybrids for unassisted solar carbon dioxide fixation to value-added chemicals." The other corresponding authors and leaders of this research are chemists Christopher Chang and Michelle Chang. Both also hold joint appointments with Berkeley Lab and UC Berkeley. In addition, Chris Chang is a Howard Hughes Medical Institute (HHMI) investigator. (See below for a full list of the paper's authors.)

The more carbon dioxide that is released into the atmosphere the warmer the atmosphere becomes. Atmospheric carbon dioxide is now at its highest level in at least three million years, primarily as a result of the burning of fossil fuels. Yet fossil fuels, especially coal, will remain a significant source of energy to meet human needs for the foreseeable future. Technologies for sequestering carbon before it escapes into the atmosphere are being pursued but all require the captured carbon to be stored, a requirement that comes with its own environmental challenges.

The artificial photosynthetic technique developed by the Berkeley researchers solves the storage problem by putting the captured carbon dioxide to good use.

This break-through artificial photosynthesis systems has four general components: (1) harvesting solar energy, (2) generating reducing equivalents, (3) reducing CO2 to biosynthetic intermediates, and (4) producing value-added chemicals. Credit: Berkeley Lab

"In natural photosynthesis, leaves harvest and carbon dioxide is reduced and combined with water for the synthesis of molecular products that form biomass," says Chris Chang, an expert in catalysts for carbon-neutral energy conversions. "In our system, nanowires harvest solar energy and deliver electrons to bacteria, where carbon dioxide is reduced and combined with water for the synthesis of a variety of targeted, value-added chemical products."

By combining biocompatible light-capturing nanowire arrays with select bacterial populations, the new artificial photosynthesis system offers a win/win situation for the environment: solar-powered green chemistry using sequestered carbon dioxide.

"Our system represents an emerging alliance between the fields of materials sciences and biology, where opportunities to make new functional devices can mix and match components of each discipline," says Michelle Chang, an expert in biosynthesis. "For example, the morphology of the nanowire array protects the bacteria like Easter eggs buried in tall grass so that these usually-oxygen sensitive organisms can survive in environmental carbon-dioxide sources such as flue gases."

The system starts with an "artificial forest" of nanowire heterostructures, consisting of silicon and titanium oxide nanowires, developed earlier by Yang and his research group.

"Our artificial forest is similar to the chloroplasts in green plants," Yang says. "When sunlight is absorbed, photo-excited electron?hole pairs are generated in the silicon and titanium oxide nanowires, which absorb different regions of the solar spectrum. The photo-generated electrons in the silicon will be passed onto bacteria for the CO2 reduction while the photo-generated holes in the titanium oxide split water molecules to make oxygen."

Once the forest of nanowire arrays is established, it is populated with microbial populations that produce enzymes known to selectively catalyze the reduction of carbon dioxide. For this study, the Berkeley team used Sporomusa ovata, an anaerobic bacterium that readily accepts electrons directly from the surrounding environment and uses them to reduce carbon dioxide.

This is a cross-sectional SEM image of the nanowire-bacteria hybrid array used in a revolutionary new artificial photosynthesis system. Credit: Berkeley Lab

"S. ovata is a great carbon dioxide catalyst as it makes acetate, a versatile chemical intermediate that can be used to manufacture a diverse array of useful chemicals," says Michelle Chang. "We were able to uniformly populate our nanowire array with S. ovata using buffered brackish water with trace vitamins as the only organic component."

Once the carbon dioxide has been reduced by S. ovata to acetate (or some other biosynthetic intermediate), genetically engineered E.coli are used to synthesize targeted chemical products. To improve the yields of targeted chemical products, the S. ovata and E.coli were kept separate for this study. In the future, these two activities - catalyzing and synthesizing - could be combined into a single step process.

A key to the success of their artificial photosynthesis system is the separation of the demanding requirements for light-capture efficiency and catalytic activity that is made possible by the nanowire/bacteria hybrid technology. With this approach, the Berkeley team achieved a solar energy conversion efficiency of up to 0.38-percent for about 200 hours under simulated sunlight, which is about the same as that of a leaf.

The yields of target chemical molecules produced from the acetate were also encouraging - as high as 26-percent for butanol, a fuel comparable to gasoline, 25-percent for amorphadiene, a precursor to the antimaleria drug artemisinin, and 52-percent for the renewable and biodegradable plastic PHB. Improved performances are anticipated with further refinements of the technology.

"We are currently working on our second generation system which has a solar-to-chemical conversion efficiency of three-percent," Yang says. "Once we can reach a conversion efficiency of 10-percent in a cost effective manner, the technology should be commercially viable."

Explore further: Researchers report first fully integrated artificial photosynthesis nanosystem

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22 comments

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hillmeister
5 / 5 (5) Apr 16, 2015
Awesome! Good riddance fossil fuels!
stripeless_zebra
5 / 5 (1) Apr 16, 2015
Now I start worrying about Global Cooling :)
gkam
1 / 5 (3) Apr 16, 2015
Some smart businessman will start locking up the rights to roof space.
JVK
1 / 5 (2) Apr 17, 2015
See also: Single-residue insertion switches the quaternary structure and exciton states of cryptophyte light-harvesting proteins http://www.pnas.o...abstract

They appear to have artificially linked the light-induced de novo creation of amino acids to RNA-mediated metabolic and genetic networks that link nutrient uptake and the biophysically constrained chemistry of protein folding to cell type differentiation in all genera via amino acid substitutions, which are fixed in organized genomes via the physiology of reproduction.

If they can prevent virus-induced mutations in the microbes, they may be able to avoid the fatal flaw that limits commercial interest to those who are biologically uninformed. Alternatively, they may realize the thermodynamic cycles of protein biosynthesis and degradation involve more of the complex systems biology that enables bacteria to sense nutrients and secrete metabolites that control reproduction.
FainAvis
5 / 5 (1) Apr 17, 2015
@Gkam You are a pessimist.
OdinsAcolyte
5 / 5 (1) Apr 17, 2015
Impressive. The only real factor shall be cost, as in everything. Economics of solutions are most important.
betterexists
not rated yet Apr 17, 2015
Also, 5 years back "Microbial Electrosynthesis: Feeding Microbes Electricity To Convert Carbon Dioxide and Water to Multicarbon Extracellular Organic Compounds" by Nevin etal says on American Society for Microbiology...."The possibility of providing the acetogenic microorganism Sporomusa ovata with electrons delivered directly to the cells with a graphite electrode for the reduction of carbon dioxide to organic compounds was investigated. Biofilms of S. ovata growing on graphite cathode surfaces consumed electrons with the reduction of carbon dioxide to acetate and small amounts of 2-oxobutyrate. Electrons appearing in these products accounted for over 85% of the electrons consumed. These results demonstrate that microbial production of multicarbon organic compounds from carbon dioxide and water with electricity as the energy source is feasible. "
JVK
1 / 5 (3) Apr 17, 2015
Thanks. At times like this I remember the movie Conspiracy Theory with Mel Gibson.
http://www.amazon...02AS464Q

'A crackpot Big Apple cabbie finds himself in a heap of trouble after his self-published conspiracy 'zine elicits the interest..."

If my blog sites suddenly disappear and you find I have forgotten everything I knew about cell type differentiation, don't mention it to anyone else.

Until then, see http://rna-mediated.com/
https://www.faceb...Research and other sources of accurate information that links physics, chemistry, and molecular biology.
Vietvet
4.5 / 5 (8) Apr 18, 2015
@JVK

The world would be better off if you forgot what you think you know about cell type differentiation.
betterexists
not rated yet Apr 18, 2015
When can Artificial Photosynthesis be considered as 100% Artificial and 100% GREAT?
1) The day no use of bacterium is made in the experimental system. 2) To add to the previous point, may be we can add this one: The day it Exceeds any Natural Photosynthetic system in Efficiency..
Keep struggling, Folks!
betterexists
not rated yet Apr 18, 2015
Well, Berkeley Team achieves Solar energy Conversion Efficiency of 0.38% for 200 hrs which is same as that of a leaf (under simulated sunlight). They are currently working on their 2nd gen system which has a solar-to-chemical conversion efficiency of 3%. This technology will be commercially viable only when Conversion efficiency of 10% is reached in a cost effective manner. Wait on Folks! Read_on_ natureworldnewsWebsite.
The Photocatalyst, Titanium is 9th-most abundant ELEMENT in Earth's crust (0.63% by mass) & 7th-most abundant METAL.
betterexists
not rated yet Apr 18, 2015
My Advice is: "Keep Sailing in Titanic!" Efficiency multiplication by 30X is needed. Keep going.
betterexists
not rated yet Apr 18, 2015
My Advice is: "Keep Sailing in Titanic!" Efficiency multiplication by 30X is needed. Keep going.
It is like a guy making $8/ hr aspiring wages of $240.00/ hr. BEST OF LUCK! Of course, our focus is on elimination of toxic co2 i.e recycling it into fuel. Pretty Good.
betterexists
not rated yet Apr 18, 2015
Obviously, it is the need of the hour....In other words, ESSENTIAL!
In 2008 itself, there were approximately 5,800 km of CO2 pipelines in the United States, used to transport CO2 to oil production fields where it is then injected into older fields to extract oil. World's first commercial Carbon capture and storage (CCS) example is Weyburn (Year 2000). An integrated pilot-scale CCS power plant was to begin operating in September 2008 in the East German power plant Schwarze Pumpe run by utility Vattenfall, in the hope of answering questions about technological feasibility and economic efficiency. Deep Ocean storage is no longer considered feasible because it greatly increases the Problem of Ocean Acidification.
JVK
1 / 5 (2) Apr 18, 2015
The world would be better off if you forgot what you think you know about cell type differentiation.


http://www.telegr...ers.html

A protein which 'turbo-charges' the immune system so that it can fight off any cancer or virus has been discovered by scientists.

What kind of biologically uninformed science idiot wants others to stop "Combating Evolution to Fight Disease" http://www.scienc...88.short

That was a rhetorical question. Steven Taylor (aka Vietvet) is only one of them. Many others have been taught to believe in pseudoscientific nonsense about cell type differentiation, and many more people will be taught to believe in ridiculous theories. They are not intelligent enough to examine the facts established by experimental evidence published in journals like "Science" and "Nature."
JVK
1 / 5 (2) Apr 18, 2015
The world would be better off if you forgot what you think you know about cell type differentiation.


DNA Methylation, Its Mediators and Genome Integrity. Int J Biol Sci 2015; 11(5):604-617. doi:10.7150/ijbs.11218. Available from http://www.ijbs.c...0604.htm

Conclusion: "These insights linking the genetic instability and epigenetic perturbations such as aberrant DNA methylation machinery may ultimately form the basis for novel therapeutic strategies and targets for the treatment of inherited, acquired and malignant diseases."

See also: Search Results for 'RNA-mediated DNA methylation' http://rna-mediat...hylation

Why do people like Steven Taylor (aka Vietvet) keep touting their death-promoting and disease-promoting pseudoscientific nonsense? Why do they comment to Phys.org at all, and why do moderators allow their comments? Perhaps the folks at phys.org need examples of biologically uninformed science idiots. I don't.
JVK
1 / 5 (2) Apr 18, 2015
The world would be better off if you forgot what you think you know about cell type differentiation.


From Fertilization to Adult Sexual Behavior
http://www.hawaii...ion.html

From our section on "Molecular epigenetics"
It is now understood that certain genes undergo a process called "genomic or parental imprinting." Early in embryonic development attached methyl groups become removed from most genes. Several days later, methyl groups are reattached in appropriate sites. Fascinatingly, some such genes reestablish methylation patterns based upon whether the chromosomal segment carrying the gene came from maternal or paternal chromosomes.

Why does Steven Taylor think the world would be better off without the accumulation of information about cell type differentiation that started in the early 90's? Which one of your loved ones does he want to see suffer and die from something that could be prevented?
JVK
1 / 5 (2) Apr 18, 2015
See also: http://www.ijbs.c...0604.htm
"5mC as Mutagen and Cancer-Causing Mutation"

The link to mutations and disease can be compared to this representation:
http://www.pnas.o...abstract
Neocortical Tet3-mediated accumulation of 5-hydroxymethylcytosine promotes rapid behavioral adaptation

The link from RNA-directed DNA methylation to RNA-mediated amino acid substitutions that affect behavior may be the most significant scientific advance because it refutes the ridiculous theories of evolutionists who try to link mutations to cell type differentiation without considering the development of species-specific behaviors that must be linked to the physiology of reproduction during life history transitions.

For instance: The Val158Met amino acid substitution links the transitions from adolescence to adults: http://dx.doi.org...4-0895-5

Need I say more than this? Steven Taylor (Vietvet) is a fool.
JVK
1 / 5 (3) Apr 18, 2015
From my invited review: Nutrient-dependent pheromone-controlled ecological adaptations: from atoms to ecosystems
http://figshare.c...s/994281

"Researchers recently rediscovered a nutrient-dependent epigenetic variant that links vitamin C to what is probably a glucose and glucose dehydrogenase-dependent base pair change. The base pair change results in addition of a methyl group to a cytosine base, which takes on a hydroxyl group to form different 5-hydroxymethylcytosines (5hmCs). Different 5hmCs are associated with differences in cell types that have the same genetic backgrounds."

Nutrient-dependent epigenetically-marked bases help to explain how hundreds of cell types in the human body and in the brain (Kriaucionis & Heintz, 2009) are differentiated and how they maintain their glucose-dependent and other nutrient-dependent receptor-mediated identities..."
JVK
1 / 5 (3) Apr 18, 2015
It is like a guy making $8/ hr aspiring wages of $240.00/ hr.


Until then, the guy expects taxpayers to fund his works, so that he can achieve financial success via commercialization if he is able to do what's suggested. If not, he will have had a successful career based on theory that provided no benefit to anyone else but him.
tear88
3.7 / 5 (3) Apr 19, 2015
Big deal. So they'll capture the CO2 - from burning fossil fuels - and turn them into hydrocarbons. Which will then eventually decompose back into CO2 and water. This would be great - if no more fossil fuels were burned. Until then, it's trivial.
Caliban
5 / 5 (2) Apr 19, 2015
Big deal. So they'll capture the CO2 - from burning fossil fuels - and turn them into hydrocarbons. Which will then eventually decompose back into CO2 and water. This would be great - if no more fossil fuels were burned. Until then, it's trivial.


Exactly, tear88.

This process is nothing more than a holding pattern in terms of anthro CO2 emissions, and, given the expense of developing it to industrial scales for ANY purpose, it is highly unlikely that it will be adopted by the petrocomplex, which will continue with direct extraction of oil/coal/gas, rather than incur the expense of developing and deploying this tech on industrial scale.

Additionally, this tech requires a source of CO2 --ie, fossil fuel combustion. If it was capable of extracting CO2 from the atmosphere and/or ocean, then it could possibly provide some long term net reduction in CO2, but, as it stands, it does nothing at all to combat AGW.

Business as usual.

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