Tag Archives: photosynthesis

Hybrid battery feeds cyanobacteria with electricity to supercharge photosynthesis

Schematic of the microbial electro-photosynthetic system (MEPS). It uses a genetically engineered microbe that lacks Photosystem II and can therefore accommodate significantly high light intensities and continue photosynthetic activity without damage.

The world’s renewable energy capacity has increased tremendously in recent years and continues to do so at an encouraging rate. That’s good news for mankind’s mission to avert potentially catastrophic climate change, the biggest challenge of this century. The problem is that the rate of adoption of renewable energy is still not on the right track, partly because our insatiable demand for energy is also growing at a rapid pace. Playing this game of catch up requires us to put on our thinking hats and throw new clean technologies into the energy mix. And when faced with such challenges, it can be a good idea to turn to nature for inspiration.

With this in mind, researchers at Arizona State University have tapped into the natural processes that have allowed plants and many animals to draw their energy from the sun for more than a billion years. The team, led by graduate student Christine Lewis, devised a hybrid device — part battery, part living organism — that is capable of increasing energy flow from photosynthesis produced by bacteria. The researchers call this approach microbial electro photosynthesis or MEPS.

The proof-of-concept could eventually lead to new technologies fitting for a broad range of energy applications, such as transportation fuels, plastics, human and animal supplements, agrochemicals, and pharmaceuticals.

“This project involves unlocking the mysteries involved with energy transfer. Specifically, we work on bridging artificial energy with natural photosynthesis by tapping into the latter half of the photosynthetic electron transport chain,” Lewis said in a statement. “The research objectives are to have the ability to turn photosynthesis on at will, eventually to make it more efficient, and produce stable energy products.”

Tweaking nature

The evolution of photosynthesis on a large scale is one of the most significant events that shaped life on Earth. Not only did this process feed bacteria and plants that would then support entire ecosystems, but it also led to a massive increase in atmospheric oxygen levels, basically making our planet livable in the first place; oxygen that we and other complex life still breathe to this day.

Stripped to its bare bones, photosynthesis simply turns water, sunlight, and CO2 into energy that supports plant and bacterial growth. This natural process is possible thanks to two membrane-protein complexes called Photosystem I and Photosystem II, which work together to absorb and transfer electrons. The former’s main function is the production of a molecule called NADPH, while the latter is busy hydrolysis of water along with ATP synthesis (the energy currency of living cells made from glucose).

Scientists have tried to mimic these processes, developing so-called “artificial leaf” technologies that use sunlight to convert carbon dioxide into high-value compounds such as ethylene, methanol, and ethanol. But there are some problems.

While photosynthesis is very efficient at splitting water into hydrogen and oxygen — Photosystem II proteins in plants do this a thousand times a second, for instance — the rate at which light is converted into useful chemical energy is not suitable for the high-paced energy needs that our civilization requires.

One of the reasons why this is the case has to do with Photosystem II, which is disabled or outright destroyed when a photosynthetic organism is exposed to too many electrons at one time, such as when a plant is exposed to high-intensity sunlight.

Lewis and colleagues got around this problem by genetically modifying cyanobacteria that carry out photosynthetic cycling of electrons without a Photosystem II component. The bacteria is connected to the cathode of a battery, from which electrons are shuttled into the electron transport chain of the bacteria, with the help of some chemical mediators along the way.

As a result, the bacteria carry out photosynthesis, using the Photosystem I pathway, using an external power supply rather than energy from the sun. But the hybrid energy system also works with high-intensity light that would have been otherwise damaging.

The researchers envision a setup in which solar panels provide external power to photosynthetic reactors. Photovoltaic cells can harvest a much broader energy spectrum of light than bacteria or plants can, which are typically limited to red visible light. With the extra electrons, the modified bacteria can then perform their photosynthetic wonders on a much broader spectrum of light. In the future, this kind of hybrid photosynthesis could join established renewable sources, like solar and wind, to supplement our growing energy needs and replace dirty fossil fuels.

“By the year 2050, with global expansion moving at the pace that it is, our energy needs will surpass our supply. However, we can act now to learn how to provide efficient and cleaner energy,” Lewis says. “It is my goal to contribute to the next “breakthrough” that will help to make this big, blue marble a better place.”  

The findings were reported in the Journal of the American Chemical Society.

Photosynthesis could be as old as life itself

Photosynthesis has been supporting life for longer than previously assumed, according to a new paper. The finding suggests that the earliest bacteria that wiggled their way around the planet were able to perform key processes involved in photosynthesis.

Image via Pixabay.

Exactly how the earliest organisms on our planet lived and evolved is an area of active interest and research — but not answers are few and scarce. However, a new paper could fundamentally change how we think about this process.

The advent of photosynthesis on a large scale is one of the most significant events that shaped life on Earth. Not only did this process feed bacteria and plants that would then support for entire ecosystems, but it also led to a massive increase in atmospheric oxygen levels, basically making our planet livable in the first place. Oxygen that we and other complex life still breathe to this day.

To the best of our understanding , it took life several billion years to evolve the ability to perform photosynthesis. However, if the findings of this new study are confirmed, it means complex life could have appeared much earlier.

A light diet

“We had previously shown that the biological system for performing oxygen-production, known as Photosystem II, was extremely old, but until now we hadn’t been able to place it on the timeline of life’s history. Now, we know that Photosystem II show patterns of evolution that are usually only attributed to the oldest known enzymes, which were crucial for life itself to evolve.”

The team led by researchers from Imperial College London studied the evolutionary process of certain proteins that are crucial for photosynthesis. Their findings show that these could possibly have first appeared in the very early days of life on Earth.

They traced the ‘molecular clock’ of key proteins involved in the splitting of water molecules. This approach looks at the time between ‘evolutionary moments’, events such as the emergence of different groups of cyanobacteria or land plants that carry a version of these proteins. They then used this to calculate the rate at which the proteins evolved over time — by backtracking this rate, researchers can estimate when a protein first appeared.

A comparison with other known proteins, including some used in genetic data manipulation that should (in theory) be older than life itself, as well as comparison with more recent events, suggests that these photosynthesizing enzymes are very old. According to the team, they have nearly identical patterns of evolution to the oldest enzymes — suggesting they evolved at a similar rate for a similar time.

Based on what we know so far, type II photosynthesis (which produces oxygen) likely appeared around 2.5 billion years ago in cyanobacteria (blue-green algae), with type I likely evolving some time before that. But there’s something that doesn’t really mesh with that timeframe: we know that there were pockets of atmospheric oxygen before this time. This means that biological communities were around to produce said oxygen even before the 2.5 billion years ago mark, since oxygen is extremely reactive and doesn’t last long in nature without binding to something. Researchers have been trying to reconcyle this for a while.

The current findings could help make everything fit. According to the team, key enzymes that underpin photosynthesis were likely present in the earliest bacteria on Earth. There’s still some uncertainty about this, as life on our planet is at least 3.4 billion years old, but it could be older than 4 billion years.

The first versions of the process were probably simplified, very inefficient versions of the one seen in plants and algae today. It took biology around one billion years to tweak and refine the process, which eventually led to the appearance of cyanobacteria. From there, it took two more billion years for plants and animals to colonize dry land, with the latter breathing oxygen produced by the former.

One interesting implication of these findings is that it could mean life would evolve much quicker and easier on other planets than previously assumed. We tend to estimate this based on how quickly and easily life appeared and then developed on Earth.

The paper “Time-resolved comparative molecular evolution of oxygenic photosynthesis” has been published in the journal Biochimica et Biophysica Acta (BBA) – Bioenergetics.

Researchers develop a functional artificial chloroplast

New research is bringing us one step closer to artificial chloroplasts, which would be able to produce clean energy, fuel, and carbon compounds from sunlight and thin air.

Each cell-sized droplet acts as a synthetic chloroplast. The thylakoid membranes visible in the microscope images (top row) use light to produce NADPH (which is seen fluorescing in the bottom row) and ATP, which is used by biological systems as energy storage.
Image credits Miller et al., (2020), Science.

If there’s one engine that keeps life as we know it going, it’s the chloroplast. They help plants generate organic compounds using CO2, nutrients, and sunlight, and plants feed everything else. They also produce the oxygen our cells use in respiration. So they supply the building blocks, fuel, and the gases needed to keep our cells alive.

Creating artificial chloroplasts could allow humanity to tap into this process for our own needs. It could allow us to produce energy, fuel, and organic substances from thin air. But we’ve had a hard time actually creating these artificial photosynthesis machines.

Synthetic biology and microfluidics

A team of researchers at the MaxSynBio network, part of the Max Plank Society, has successfully created a platform for the automated construction of cell-sized artificial chloroplasts, which are able to function just like the natural ones.

“Our work shows for the first time that you can realise alternative, autonomous photosynthetic systems at the micro-scale from individual parts and modules, allowing us to construct “alternative” biological solutions, which nature has not explored,” explains Tobias Erb, co-author of the paper .

“To our knowledge, it is the first demonstration of continuous, multi-step conversion of carbon dioxide into carbon compounds.”

The team used the CETCH (crotonylCoA/ethylmalonyl-CoA/hydroxybutyryl-CoA) cycle developed in 2016 by Tobias Erb’s lab at the Max Planck Institute for Terrestrial Biology in Marburg, Germany. This cycle mimics natural photosynthesis but relies on a series of natural and engineered enzymes to make it even more efficient than the one employed by plants. What they describe in this paper is the process through which they ‘grafted’ the CETCH cycle onto thylakoid membranes – the structures that convert light into energy-rich compounds in natural chloroplasts (isolated from spinach).

Synthetic biology was used to design and build the components needed to assemble these CETCH-thylakoid membrane couplings, and microfluidics to encapsulate them together in water-and-oil microdroplets. This last step follows the natural structure of cells (which have lipid membranes and watery interiors) and allowed for the creation of “hundreds to thousands of cell-sized compartments that can operate independently from each other,” Erb adds.

The team explains that past attempts have failed when trying to mix the CETCH cycle with the rest of the artificial chloroplast and that their success marks an important step towards harnessing photosynthesis for human use.

“This opens the way for the standardized mass production of catalytically active micro-reaction compartments – or “artificial cells” – for different biotechnological applications in the future,” he adds.

The paper “Light-powered CO2 fixation in a chloroplast mimic with natural and synthetic parts” has been published in the journal Science.

Photosynthesis.

Semi-artificial photosynthesis points the way to a viable hydrogen economy

Researchers from the University of Cambridge look to plants for a new energy revolution.

Molecules.

Oxygen, hydrogen (left) and water molecules (right).
Image credits Luis Romero / Flickr.

Looking for new and more efficient ways of harvesting solar energy, a team of researchers from St John’s College has turned plants to the job. The team has successfully split water molecules into hydrogen and oxygen by altering and improving on natural photosynthetic processes. Photosynthesis is the process plants use to convert sunlight into energy.

Lettuce make fuel

Photosynthesis is arguably the most important process for life on Earth. The process — which uses energy in sunlight to break down water and carbon dioxide — provides the energy and building blocks that plants need to grow. In turn, plants act as primary producers: they form the first link of virtually every trophic network on the planet, essentially feeding the rest of the planet. Moreover, photosynthesis is the source of nearly all the oxygen in the atmosphere today. In its absence, oxygen (a very reactive gas) would bind with chemical compounds or would be used up in biological respiration pretty quickly, and we’d all choke to death. Which would be sad.

Not content to let the process drive just our biology, the team — led by St John’s College PhD student Katarzyna Sokół — worked on turning it into a power source.

Hydrogen has long been considered a viable — and powerful — alternative to fossil fuels. In fact, the first internal combustion engine ever built used a mixture of hydrogen and oxygen, not fossil fuels, to generate energy. It was designed by Francois Isaac de Rivaz, a Swiss inventor, all the way back in 1806. However, it never really caught on, as we didn’t know of any fast and cheap way of mass-producing the gas.

Artificial photosynthesis has yet to reach a point where it can supply enough hydrogen for wide-scale use, mostly because it relies on the use of catalysts, which are often expensive and toxic. On the other hand:

“Natural photosynthesis is not efficient because it has evolved merely to survive so it makes the bare minimum amount of energy needed — around 1-2 per cent of what it could potentially convert and store,” says Katarzyna Sokół, who is also the paper’s first author.

This means that neither can support an industrial-level economy based on hydrogen.

Photosynthesis.

Experimental two-electrode setup showing the photoelectrochemical cell illuminated with simulated solar light.
Image credits Katarzyna Sokół.

The team’s new paper details their efforts to change this state of affairs. Using a combination of biological components and manmade technologies, they managed to convert water into hydrogen and oxygen at high efficiency using only sunlight — a process known as semi-artificial photosynthesis. As part of their research, the team had to remove genetic limitations on photosynthesis that had been imposed millennia ago.

“Hydrogenase is an enzyme present in algae that is capable of reducing protons into hydrogen. During evolution this process has been deactivated because it wasn’t necessary for survival,” Sokół explains, “but we successfully managed to bypass the inactivity to achieve the reaction we wanted — splitting water into hydrogen and oxygen.”

The team is the first to successfully create semi-artificial photosynthesis driven solely by sunlight. Their method was over 80% more efficient than natural photosynthesis.

The groundwork they laid down in integrating organic and inorganic materials into semi-artificial devices also provides new avenues of research into other systems for solar energy capture, they add.

“It’s exciting that we can selectively choose the processes we want, and achieve the reaction we want which is inaccessible in nature,” Sokół explains.

“This could be a great platform for developing solar technologies. The approach could be used to couple other reactions together to see what can be done, learn from these reactions and then build synthetic, more robust pieces of solar energy technology.”

The paper has been published in the journal Nature.

Elysia chlorotica.

New species of sea slug steals algae chlorophyll to live a solar-powered lifestyle

Is it an animal? Is it a plant? Strangely, it’s a bit of both — one newly-discovered species of sea slug lives entirely on photosynthesis.

Elysia chlorotica.

Elysia chlorotica.
Image credits Karen N. Pelletreau / University of Maine.

Ever wished you could plaster your body with solar panels and just go about your day, feeding off sunlight in lieu of eating? Sorry to break it to you, then, but there’s one sea slug is living your dream right now. According to researchers from the Rutgers University-New Brunswick, the slug can suck raw material from algae to maintain its solar-powered lifestyle.

Light eating

“It’s a remarkable feat because it’s highly unusual for an animal to behave like a plant and survive solely on photosynthesis,” said Debashish Bhattacharya, senior author of the study.

“The broader implication is in the field of artificial photosynthesis. That is, if we can figure out how the slug maintains stolen, isolated plastids to fix carbon without the plant nucleus, then maybe we can also harness isolated plastids for eternity as green machines to create bioproducts or energy.”

Christened Elysia chlorotica, the mollusk can grow to about 2 inches long and lives in the intertidal zone between Nova Scotia, Canada and Martha’s Vineyard, Massachusetts, as well as in Florida, the team reports. As juveniles, the slugs munch on Vaucheria litorea, a non-toxic variety of brown algae, to appropriate their plastids — the algae’s photosynthetic organelles — and store them in their gut lining.

The team used RNA sequencing to see what the slug does with the plastids it ingests. Their results show that the animal’s body actively responds to the organelles, protecting them from digestion and turning on genes to utilize the photosynthetic products they synthesize. The team’s results resemble findings in corals — animals that maintain symbiotic dinoflagellates (algae) which perform photosynthesis to help feed the coral.

Bhattacharya explains that Vaucheria litorea is an ideal food source for the slug because it doesn’t have walls separating adjoining cells in its body — it’s essentially one long tube filled with nuclei and plastids. This means that the slug can suck out all the cellular contents through a single puncture, anywhere along the algae’s outer wall.

After gathering enough of the organelles (in the order of a few million), the slugs become photosynthetic. Just like a plant, they start using sunlight to create sugars (compounds that store chemical energy) in their bodies from carbon dioxide and water.

Previous research performed on other species of sea slugs suggested that the animals steal these plastids and store them as food for later use — similar to how our bodies store fat. So far, Elysia chlorotica seems to be the only species that actually uses them to carry out photosynthesis, Bhattacharya says.

“It has this remarkable ability to steal these algal plastids, stop feeding and survive off the photosynthesis from the algae for the next six to eight months,” he adds.

Finally, the team notes that, while the slugs store plastids, they don’t do the same for nuclei they ingest. They still don’t know how the slug’s body keeps the plastids healthy and operational for months, or how they operate the organelles without the algal nuclei — which normally control the plastids’ activity, Bhattacharya adds.

The paper “Active Host Response to Algal Symbionts in the Sea Slug Elysia chlorotica” has been published in the journal Molecular Biology and Evolution.

Artist's rendering of bioreactor (left) loaded with bacteria decorated with cadmium sulfide, light-absorbing nanocrystals (middle) to convert light, water and carbon dioxide into useful chemicals (right). Credit: Kelsey K. Sakimoto.

Cyborg bacteria equipped with tiny solar panels outperform photosynthesis

All biological processes on Earth rely on the sun for energy. It’s the sun’s rays that allow plants or cyanobacteria to grow. They become lunch for different creatures which in turn are preyed on higher up the food chain. Plants use the energy from incoming photons in a biological process known as photosynthesis, and for all intents and purposes, this is an elegant solution. However, it’s not all that efficient and researchers at the University of California, Berkeley, think they can come up with something better — or at least something different that might work well for some applications.

Artist's rendering of bioreactor (left) loaded with bacteria decorated with cadmium sulfide, light-absorbing nanocrystals (middle) to convert light, water and carbon dioxide into useful chemicals (right). Credit: Kelsey K. Sakimoto.

Artist’s rendering of bioreactor (left) loaded with bacteria decorated with cadmium sulfide, light-absorbing nanocrystals (middle) to convert light, water and carbon dioxide into useful chemicals (right). Credit: Kelsey K. Sakimoto.

At the 254th National Meeting & Exposition of the American Chemical Society (ACS), Kelsey K. Sakimoto and colleagues showed off their latest attempt at harvesting energy with a hybrid system comprised of bacteria and what can only be described as tiny solar panels. Essentially, when the Moorella thermoacetica bacteria, which is nonphotosynthetic, was fed cadmium and the amino acid cysteine, it synthesized the food into cadmium sulfide (CdS) nanoparticles. These are the semiconducting materials many solar panels employ on their surface to collect photons and create electron-hole pairs. 

They then showed that the hybrid system comprised of M. thermoacetica-CdS could make acetic acid from CO2, water, and light. “Once covered with these tiny solar panels, the bacteria can synthesize food, fuels, and plastics, all using solar energy,” Sakimoto said in a statement.

Plants turn CO2, water, and light into oxygen and sugars mainly through chlorophyll, which are the green pigments plants use to harvest sunlight. They’re quite similar to semiconductors employed in solar energy only photovoltaic cells turn all of that sunlight into flowing electrons whereas photosynthetic plant cells turn it into plant food. The problem is photosynthesis doesn’t seem all that efficient. Typically, most plants have a sunlight to biomass conversion of only 0.1%-0.2% whereas some crops see 1-2% efficiency.

The hybrid system, however, operates at an efficiency of more than 80 percent, all in a self-replicating and self-generating environment. “These bacteria outperform natural photosynthesis,” Sakimoto said.

Of course, none of this makes trees and plants obsolete. Given our urgent need to phase off fossil fuels, however, any alternative technology that can generate clean energy or products is more than welcome. Acetic acid, for instance, is a very versatile chemical. It’s widely used in the chemical manufacturing industry to make polymers, pharmaceuticals, even liquid fuels. In fact, you have a 5-20% acetic acid-water solution in your kitchen right now — vinegar. Even among alternative energy systems, such as artificial photosynthesis devices, this bacterial-semiconductor system offers long-standing benefits.

“Many current systems in artificial photosynthesis require solid electrodes, which is a huge cost. Our algal biofuels are much more attractive, as the whole CO2-to-chemical apparatus is self-contained and only requires a big vat out in the sun,” Sakimoto points out.

For now, he and colleagues are working on making the semiconductor and bacteria interact better. They’re also looking at other matches that might render different chemicals or foods.

Synthetic Photosynthesis.

New, cheap artificial photosynthesis scrubs the air and produces fuel

A research team from the University of Central Florida has found a way to trigger photosynthesis in an inexpensive synthetic material. The technology could be used to scrub the air clean and produce ‘solar’ fuel from atmospheric CO2.

Synthetic Photosynthesis.

The team’s photoreactor, with a sliver of the MOF dangling inside.
Image credits Bernard Wilchusky.

Scientists the world over have been trying to re-create the process that plants rely on to feed in a synthetic material for years now, with some success. Photosynthesis-like reactions can be maintained in common materials such titanium dioxide under higher-energy UV light. But, since the lion’s share of energy released by the Sun lies in the violet to red wavelengths, the challenge lies in finding a way to keep it going under visible light. Up to now, we’ve known comparatively few materials that can do so, and they’re very expensive (think platinum or iridium compounds), keeping them far away from commercial applications.

Uribe-Romo, a chemistry professor at the UCF, and his students may bring artificial photosynthesis into the market. The team has found a way to trigger the reaction in an inexpensive synthetic material, offering a cost-effective way to turn atmospheric CO2 into fuel.

The system uses a class of materials known as metal-organic frameworks (MOFs) to break down the CO2 into its two compounds. Uribe-Romo’s MOF was constructed from titanium with a pinch of organic molecules to act as light-harvesting points and power the reaction. These molecules, called N-alkyl-2-aminoterephthalates, can be tailored to absorb specific wavelengths (colors) of light when incorporated in the MOF — the team went for blue.

They tested the system under a photoreactor — a battery of blue LED lights which looks like a tiny tanning bed — constructed to mimic the sun’s blue wavelength. Controlled amounts of CO2 were pumped into the photoreactor, and the MOF scrubbed it out then split it into two reduced carbon compounds — formate and formamide.

“The goal is to continue to fine-tune the approach so we can create greater amounts of reduced carbon so it is more efficient,” Uribe-Romo said.

He says that the next thing the team will be looking into is how to adjust their material so it can sustain the process under other colors of light. If they can pull it off, the system will gain hugely in versatility and could grow to become a significant carbon sink. Stations could be set up near CO2-producing areas, such as power plants, to capture the gas and use it to produce energy which could be fed back into the system. Or it could be fashioned into rooftops that homeowners can install to clean their neighborhood’s air while saving up on power bills.

“That would take new technology and infrastructure to happen,” Uribe-Romo said. “But it may be possible.”

The full paper “Systematic Variation of the Optical Bandgap in Titanium Based Isoreticular Metal-Organic Frameworks for Photocatalytic Reduction of CO2 under Blue Light” has been published in the Journal of Material Chemistry A.

Photosynthetic solar cell turns carbon dioxide and sunlight into fuel

A team of researchers from the University of Illinois at Chicago (UIC) has created a photosynthetic solar cell that converts atmospheric carbon dioxide into usable hydrocarbon fuel.

The solar cell that converts atmospheric carbon dioxide directly into fuel. Credit: University of Illinois at Chicago/Jenny Fontaine

The solar cell that converts atmospheric carbon dioxide directly into fuel. Credit: University of Illinois at Chicago/Jenny Fontaine

Conventional solar cells convert sunlight into electricity that must be stored in heavy batteries. The new solar cell is potentially game-changing because it converts atmospheric carbon dioxide into fuel, which could not only remove large amounts of carbon from the atmosphere but also create energy-dense fuel.

“The new solar cell is not photovoltaic – it’s photosynthetic,” said Amin Salehi-Khojin, an assistant professor of mechanical and industrial engineering at UIC and senior author of the study. “Instead of producing energy in an unsustainable one-way route from fossil fuels to greenhouse gas, we can now reverse the process and recycle atmospheric carbon into fuel using sunlight.”

If the new solar cell can be taken advantage of on a global scale, it would render fossil fuels obsolete by giving us the ability to turn carbon dioxide into fuel at a cost similar to a gallon of gasoline.

Past studies have failed to find effective catalysts for the conversion of carbon dioxide into burnable forms of carbon. In the current study, Salehi-Khojin and his team focused on using transition metal dichalcogenides (TMDCs) as catalysts, which they paired with an unconventional ionic liquid as the electrolyte. They were then placed inside a two-compartment, three-electrode electrochemical cell.

Of all of the TMDCs that they tried, nanoflake tungsten diselenide turned out to be the ideal catalyst.

“The new catalyst is more active; more able to break carbon dioxide’s chemical bonds,” said Mohammad Asadi of UIC and first author of the paper.

The final solar cell is an artificial leaf that consists of two silicon triple-junction photovoltaic cells that harvest light. On the cathode side is the tungsten diselenide and ionic liquid co-catalyst system, while the anode side possesses cobalt oxide in potassium phosphate electrolyte.

The team hopes that the technology will be able to be adapted not only to large-scale applications such as solar farms, but also small-scale applications.

Journal Reference: Nanostructured transition metal dichalcogenide electrocatalysts for CO2 reduction in ionic liquid. 29 July 2016. 10.1126/science.aaf4767

banana leaf

Reverse photosynthesis turns plants into biofuels

Photosynthesis is maybe the most important chemical process on Earth, turning sunlight and CO2 into the oxygen we breath and the food we eat. This process can be reversed, however. Danish researchers were the first to demonstrate how biomass can be broken down by sunlight in the presence of an enzyme and turned into useful chemicals like biofuels or renewable plastic.

banana leaf

Image: Pixabay

“This is a game changer, one that could transform the industrial production of fuels and chemicals, thus serving to reduce pollution significantly,” says University of Copenhagen Professor Claus Felby, who heads the research published in Nature Communications.

“It has always been right beneath our noses, and yet no one has ever taken note: photosynthesis by way of the sun doesn’t just allow things to grow, the same principles can be applied to break plant matter down, allowing the release of chemical substances. In other words, direct sunlight drives chemical processes. The immense energy in solar light can be used so that processes can take place without additional energy inputs,” says Professor Claus Felby.

Breaking down plant material is mainly done using industrial processes with high energy inputs, and can take a long time. The process developed in Denmark relies on lytic polysaccharide monooxygenases, a natural enzymes also used in industrial biofuel production, which aided by the sun’s energy can break down plant material in less than 10 minutes.

Tests were made on biomass — straw or wood — sprinkled with chlorophyll and the enzyme. The sun’s rays then break the sugar molecules inside the biomass into smaller constituents.

“We use the term “reverse photosynthesis” because the enzymes use atmospheric oxygen and the Sun’s rays to break down and transform carbon bonds, in plants among other things, instead of building plants and producing oxygen as is typically understood with photosynthesis”, says Postdoc Klaus Benedikt Møllers

Using this process biofuels could be made much faster. Methanol, an important fuel, could be sourced directly and at ambient conditions without additional energy inputs, for instance.

There’s reason to believe this reaction occurs naturally on the planet, though no one has reported it yet.

 

The light-collecting centers, called chromophores, are in red, and chromophores that just absorbed a photon of light are glowing white. After the virus is modified to adjust the spacing between the chromophores, energy can jump from one set of chromophores to the next faster and more efficiently. Image: MIT

A virus was used to harvest energy from light, and it could be used in solar cells someday

Solar energy could be turned up a notch not by some exotic material or chip, but surprisingly by viruses. A team at MIT published a paper demonstrating how a genetically modified virus was used in a quantum system to transfer energy at double the speed and over a greater distance than even the best solar cells.

The light-collecting centers, called chromophores, are in red, and chromophores that just absorbed a photon of light are glowing white. After the virus is modified to adjust the spacing between the chromophores, energy can jump from one set of chromophores to the next faster and more efficiently. Image: MIT

The light-collecting centers, called chromophores, are in red, and chromophores that just absorbed a photon of light are glowing white. After the virus is modified to adjust the spacing between the chromophores, energy can jump from one set of chromophores to the next faster and more efficiently. Image: MIT

Plants are the most efficient energy harvesting mediums, as photosynthesis is able to convert almost all the income energy a plant receives with little waste. It’s no wonder then that a lot of scientists are looking for the holy grail, an artificial leaf of sorts that can mimic this process that took billions of years for evolution to perfect.

When a photon hits a receptor inside a plant called a chromophore, an exciton is produced or an electron-hole pair. In other words, an electron gets charged, jumps an energy level and leaves a hole in its absence.  When the electron is initially excited it remains strongly bound to the hole since they have opposite charges and are both confined to the same small molecule. Then, this exciton jumps from one chromophore to another until it reaches a reaction center, where that energy is harnessed to build the molecules that support life.

Using quantum effects, the exciton can be in multiple places at once. Since its present in multiple pathways at once, the exciton choose the best one (most efficient). Previously, Seth Lloyd, an expert on quantum theory and its potential applications, showed that photosynthetic organisms transmit light energy efficiently because of these quantum effects and the key to their success was just the right spacing between chromophores. Lloyd later met  Angela Belcher, an expert on engineering viruses to carry out energy-related tasks, who was working with tiny engineered viruses that happened to have the right wavelength to support quantum effects. The two swapped ideas and eventually teamed up for a project.

Four years later, Belcher, Lloyd and dozens of collaborators showed how their engineered virus could bind to multiple synthetic chromophores (organic dyes) at once. They tried out multiple spacing configurations between the synthetic chromophores until they found the right one. Using laser spectroscopy and dynamical modeling, the researchers analyzed the light-harvesting process and found the viruses were indeed transporting energy in a quantum coherence framework.

“It was really fun,” Belcher says. “A group of us who spoke different [scientific] languages worked closely together, to both make this class of organisms, and analyze the data. That’s why I’m so excited by this.”

Lloyd says their work could help design a new generation of solar cells. Exciton solar cells (Dye-sensitised solar cells; Organic and hybrid photovoltaics) have been around for a lot of time, but these are clumsy and convert energy at low efficiency. The quantum effect exploiting virus can transfer energy at double the speed of any exciton solar cell. For now, it’s all just a proof of concept though. The researchers have only demonstrated how the virus can be used to transport energy. They’ve yet to show how this approach can harness power (electricity) or molecules.  Check out the video below for a more in-depth and graphic explanation.

“This is exciting and high-quality research,” says Alán Aspuru-Guzik, a professor of chemistry and chemical biology at Harvard University who was not involved in this work. The research, he says, “combines the work of a leader in theory (Lloyd) and a leader in experiment (Belcher) in a truly multidisciplinary and exciting combination that spans biology to physics to potentially, future technology.”

“Access to controllable excitonic systems is a goal shared by many researchers in the field,” Aspuru-Guzik adds. “This work provides fundamental understanding that can allow for the development of devices with an increased control of exciton flow.”

Findings reported in Nature Materials.

The prototype for the first practical "artificial leaf," which has been hyped in the media since its flashy debut at the American Chemical Society national meeting last year. Image: MIT

Artificial leaf and bacteria turn sunlight into liquid fuel

Using only energy from the sun, a pioneering artificial leaf system splits water to generate hydrogen – a highly energy dense fuel. When Daniel Nocera, then a professor at MIT, announced his device for the first time four years ago, people were really hyped about it but it soon became clear that making hydrogen was only part of the solution. “The problem with the artificial leaf,” Nocera says, is that “it makes hydrogen. You guys don’t have an infrastructure to use hydrogen.” Why aren’t we seeing more hydrogen cars on the streets? Because there aren’t any hydrogen fueling stations. Why aren’t any hydrogen pumps? Because hydrogen is one bad mother. It’s the smallest stable molecule and it naturally wants to escape into the atmosphere. To contain it you need to compress it to at least 10,000 PSI (more like 100,000 PSI to be sure) which makes it extremely expensive and prohibitive.

Sunlight to liquid fuel

The prototype for the first practical "artificial leaf," which has been hyped in the media since its flashy debut at the American Chemical Society national meeting last year. Image: MIT

The prototype for the first practical “artificial leaf,” which has been hyped in the media since its flashy debut at the American Chemical Society national meeting last year. Image: MIT

Conspiracies aside, diesel and gasoline are here to stay for a long while because they’re so convenient – they’re cheap, readily available and liquid at normal temperature and pressure. Also, while hydrogen  has more energy per unit mass than other fuels, it’s much less dense than other fuels. A gallon of gasoline has a mass of 6.0 pounds, the same gallon of liquid hydrogen only has a mass of 0.567 pounds or only 9.45% of the mass of gasoline.  Therefore one gallon of gasoline yields 125,400 BTUs of energy while a gallon of liquid hydrogen yields only 34,643 BTUs or 27.6% of the energy in a gallon of gasoline. What are we to do with an artificial leaf that makes hydrogen, then? Well, Nocera and his new colleagues at Harvard now report pairing their hydrogen-generating leaf with an engineered bacteria called Ralstonia eutropha to generate biomass and isopropyl alcohol, respectively – an alcohol fuel comparable to ethanol. This way, the extra step converts the hydrogen in a much more manageable fuel. Though, far from efficient right now, the system might become a viable means of storing energy from the sun – still a lifelong engineering problem.

Biofuels like ethanol are made from biomass. We call biomass any biological material derived from living, or recently living organisms – most often than not plants. In nature, plants use photosynthesis to capture CO2 and use it with water in the presence of energy from the sun to make organic compounds of carbons. These are stored and can then be used to generate energy. Sticking with ethanol, this can be broken down from starchy corn kernels. The Harvard system bypasses the biomass step and goes straight to liquid fuel thanks to their engineered bacterium.

The simple setup consists of a  triple-junction solar cell, connected with two catalysts: cobalt-borate for splitting the water molecule and a nickel-molybdenum-zinc alloy to form the hydrogen gas. The bacteria then absorbs the hydrogen, combines it with carbon dioxide, eventually producing the isopropyl alcohol. The resulting system would look like an algae farm, Nocera says, except that the bacteria wouldn’t need the continuous light or maintenance that algae require.

While it all sounds extremely appealing, there are still many challenges that the researchers need to overcome. One has already been met. In initial runs the bacteria kept dying. They eventually identified  reactive oxygen as being the culprit, but what was surprising was its source. Reactive oxygen species were coming out of the hydrogen side of the water splitting, not the oxygen side. “We were shocked,” Nocera said for National Geographic. “That confused us for a while.”

Next, they need to improve the system’s flow such that it might become efficient and make sense economically. Right now, there’s more energy going into growing the microbes and extracting the fuel than going out. Findings appeared in PNAS.

This plant may look like an ordinary tobacco plant, but on the inside it was engineered to express bacteria proteins which helps it perform more efficient photosynthesis. Photo: Rothamsted Research

Tobacco plants borrowing bacteria genes achieve more efficient photosynthesis

This plant may look like an ordinary tobacco plant, but on the inside it was engineered to express bacteria proteins which helps it perform more efficient photosynthesis. Photo: Rothamsted Research

This plant may look like an ordinary tobacco plant, but on the inside it was engineered to express bacteria proteins which helps it perform more efficient photosynthesis. Photo: Rothamsted Research

It wouldn’t be an understatement to say we owe all the wonders of life to photosynthesis – the ability of plants and certain bacteria to convert CO2 into energy (sugars) and food. Scientists have for some time attempted to enhance photosynthesis through genetic manipulation, but it’s only recently that we’re beginning to see these efforts take form. The most recent breakthrough was made by a team of British and American biologists  who report they’ve  successfully infused tobacco plants with bacterial genes – a first step towards engineering crops that grow faster, offer higher yields and use less fertilizers.

Better photosynthesis, more food

Cyanobacteria – single-celled organisms also known as blue algae – are far more better at converting CO2 to useful energy than plants. Part of the reason is that the bacteria use an upgraded version of an enzyme called  rubisco, which is the protein that converts CO2 into sugar, and is possibly the most abundant protein on Earth. About half of all the soluble proteins found in leaves are rubisco.

In plants, however, rubisco isn’t that efficient and scientists have been trying to find ways to boost it for some time. If such an attempt were to be proven entirely successful, then crops with the equivalent bacterial photosynthesis ability would cut fertilizer needs and increase crop production by 35 and 60 percent. But researchers at Cornell University, USA and Rothamsted Research, UK claim they’ve managed to solve one piece of the puzzle: they’ve modified tobacco plants that produce functional rubisco from the cyanobacterium Synechococcus elongatus.

This wasn’t an easy job, though. While previous attempts focused on swapping bacterial genes that code for the turbocharged rubisco, the team also made other genetic substitutions  that encode proteins that manufacture the rubisco. The modified plants confer CO2 into sugar faster than normal tobacco, a sign that photosynthesis had been sped up and that the researchers are heading in the right direction.

Yet they still have their work cut out for them. While the photosynthesis is more efficient, the plants themselves grew significantly slower. The researchers report:

“We grew our [genetically engineered] plants in a CO2 elevated environment” with more 22 times the amount of normal amount of the gas, “and they still were growing slightly slower than the normal type plants.”

 

While the algal rubisco makes the photosynthesis more efficient, the tobacco plant wasn’t completely engineered to mimic the whole process the bacteria use. Namely, cyanobacteria employ β-carboxysome shell proteins that ward off oxygen, creating a tiny, CO2-rich environments for their rubisco. Normal plants on the other hand lack this shell and consequently adapted by using a form of rubisco that is slower and less efficient, but which none the less is also capable of picking CO2 in favor of O2. In the case of our modified tobacco plant, the Rubisco is bacterial, but without the shell, a lot of energy is wasted on reacting with oxygen.

Obviously, researchers are concentrating on how to integrate the shell with the bacterial rubisco. So far, developments have been promising since the same team engineered tobacco plants that could generate carboxysome-like structures a while back. Integrating the findings of the two bodies of research might finally take food production to a new level.

While genetically modified plants, fertilizers and pesticides have made crop yields go a long way, the momentum sparked a couple of decades ago is steadily running out. Soon enough, we’ll have to find new ways to increase food production per unit area to keep up with an ever expanding population. Tweaking photosynthesis may be just one in many such efforts.

Findings appeared in Nature.

Hot-spring bacteria can make photosynthesis using far-red light

Bacteria living in obscure environments use an extremely rare process to harvest energy and produce oxygen from sunlight – but they don’t use visible light, they use far-red light.

Image via Penn State.

“We have shown that some cyanobacteria, also called blue-green algae, can grow in far-red wavelengths of light, a range not seen well by most humans,” said Donald A. Bryant, the Ernest C. Pollard Professor of Biotechnology and professor of biochemistry and molecular biology at Penn State. “Most cyanobacteria can’t ‘see’ this light either. But we have found a new subgroup that can absorb and use it, and we have discovered some of the surprising ways they manipulate their genes in order to grow using only these wavelengths,” he said.

Far-red light is light at the extreme red end of the visible spectrum, between red and infra-red light. Usually regarded as the region between 710 and 850 nm wavelength, it is dimly visible to some eyes. Up until recently, it was thought that no organisms can use far-red light for photosynthesis, but in 2009, a different research team found a unique microbe in California’s largest lake. Now, the Penn State researchers discovered that the cyanobacterial strain, named Leptolyngbya, completely changes its photosynthetic apparatus in order to use far-red light. Basically, they can turn on a large number of genes and simultaneously turn other genes off when they need this type of photosynthesis, and the reverse process when they don’t. Because the genes that are turned on are the genes that determine which proteins the organism will produce, this massive remodeling of the available gene profile has a dramatic effect on the entire organism.

“It changes the core components of the three major photosynthetic complexes, so one ends up with a very differentiated cell that is then capable of growing in far-red light. The impact is that they are better than other strains of cyanobacteria at producing oxygen in far-red light, and they are better even than themselves. Cells grown in far-red light produce 40 percent more oxygen when assayed in far-red light than cells grown in red light assayed under the same far-red light conditions.”

This photo shows the colors of the cells of the cyanobacterium Leptolyngbya sp. strain (JSC-1), which was collected from a hot spring near Yellowstone National Park. The cells were grown in white fluorescent light (WL), green-filtered fluorescent light (GL), red light provided by 645-nm LEDs, or far-red light provided by 710-nm LEDs.

The bacteria sample was taken from the LaDuke hot spring in Montana, close to Yellowstone Park. The bacteria was living under a 2-milimeter-thick mat so thick that visible light couldn’t even get to it – only far-red light reaches it. Understanding this type of photosynthesis may actually be extremely important, because surface crusts of deserts and other soils under which this cyanobacteria might live cover a significant part of the Earth.

“It is important to understand how this photosynthetic process works in global-scale environments where cyanobacteria may be photosynthesizing with far-red light, in order to more fully understand the global impact of photosynthesis in oxygen production, carbon fixation, and other events that drive geochemical processes on our planet,” Bryant said.

The research also sheds some light on how photosynthesis in the far-red light. Bryant explains:

 “Our research already has shown that it would not be enough to insert a new far-red-light-absorbing pigment into a plant unless you also have the right protein scaffolds to bind it so that it will work efficiently.  In fact, it could be quite deleterious to just start sticking long-wavelength-absorbing chlorophylls into the photosynthetic apparatus,” he said.

 

Scientists have determined the exact structure of an important photosynthesis complex at a crucial stage. Photo: Shutterstock

New insights on photosynthesis bring us one step closer to solar fuels

For billions of years, nature has been harnessing the energy from the sun through photosynthesis. This way, plants, algae and cyanobacteria use sunlight to split water and produce energy-rich chemical compounds from carbon dioxide (CO2). This energy is then transferred to animal that eat these plants, and animals that eat plant-eating animals, including us humans. It’s clear that without photosynthesis, there would be no life as we know it. 

A photosynthesis dream

Society today is highly dependent on energy, so why not profit from a process that’s been evolutionary refined for billions of years? Synthetic photosynthesis is a hot trend in biotech right now, but while scientists have known the basic reactions involved in photosynthesis for a very long time, developing a complex artificial photosynthesis system that mimics all the transmuting steps has proved to be no easy task. Researchers at the Max Planck Institute for Chemical Energy Conversion in Mülheim an der Ruhr and the Commissariat à l’Énergie Atomique (CEA) in Saclay, France have provided new insight in how photosynthesis happens and along with it, brought us one step closer to a new energy dream.

Namely, the researchers investigated an important cofactor involved involved in photosynthesis, a manganese-calcium complex. The cofactor uses solar energy to split water into O2, and it was only now that the scientists determined the exact structure of this complex right before this crucial stage in the chemical reaction takes place. This way, the researchers have provided a basic blueprint for a synthetic system that might one day store sunlight energy in chemical energy carriers.

The job wasn’t easy; the team had to painstakingly go through an extraction and purification process of photosystem II – the large protein membrane where light-induced catalytic water splitting takes place. Then came the actual characterization work for the manganese-calcium complex, which they performed using electron paramagnetic resonance (EPR), a technique which makes it possible to visualize the distribution of the electrons in a molecule or metal complex and thus provides deep insight into the individual stages of water-splitting.

“These measurements generated new information and enabled the solvation of problems concerning the detailed analysis of molecular structures in the reaction cycle that are not accessible using other methods,” says Dr Alain Boussac from the CEA Saclay.

One might argue that we already harness the sun. Indeed, solar cells are great but the electricity they provide is unreliable and be served as baseload. This means that if we can’t develop efficient energy storage systems, solar or wind energy will always be in second place, behind fossil and nuclear. In contrast, a viable artificial photosynthesis system can store energy from the sun directly into chemical energy, ready for use at any time and any place.

“Synthetic solar fuels open up wide-ranging possibilities for renewable energy technologies, in particular for the transport and infrastructure sectors, which are still reliant on fossil fuels,” says Professor Wolfgang Lubitz, Director at the Max Planck Institute for Chemical Energy Conversion. “An efficient light-driven, water splitting catalyst based on common metals such as manganese would represent huge progress here. The insight gained into nature’s water splitting enzyme through this research has laid the foundations for such developments.”

The findings were reported in the journal Science.

photosynthesis

Popeye’s secret: spinach provides key insight that might one day lead to artificial photosynthesis

photosynthesisWhile scientists have been studying and incrementally increasing solar cell efficiency, we’ve yet to reach nature’s magnitude of solar energy conversion through photosynthesis. Artificial photosynthesis is a goal in alternative energy research, yet the process is extremely difficult to mimic since, in nature, the process involves numerous stages and transformation of matter and energy. Purdue University physicists used spinach and applied novel techniques to understand what happens during one of the photosynthesis stages.

Just add water, CO2 and sunlight

Photosynthesis is the process plants employ to convert carbon dioxide using energy from the sun into chemical energy in the form of hydrogen-carrying carbohydrates and oxygen. This process is achieved with massive energy conversion efficiency, which is why an artificial photosynthesis system is so desirable. To recreate the photosynthesis that plants have perfected, such an artificial system needs to perform two key roles: harvest energy and split water molecules. Plants accomplish these tasks using chlorophyll, which captures sunlight, and a collection of proteins and enzymes that use that sunlight to break down H2O molecules into hydrogen, electrons and oxygen (protons). The electrons and hydrogen are then used to turn CO2 into carbohydrates, and the oxygen is expelled.

One step close to the power of photosynthesis

Splitting water isn’t that simple though – there are organic catalysts involved and multi-steps processes, and nature had the benefit of millions of years worth of evolution to tweak photosynthesis to the highest efficiency possible. Attempts so far at mimicking this process have been rather counterproductive. Oxidizing water is a four-electron process, but the catalysts used in artificial photosynthesis processes, like cobalt oxide, have been found to be ineffective in the later stages.  So what can we do? Well, one course of action would be to solve and understand each intermediate step and then fill in the puzzle.

Yulia Pushkar, a Purdue associate professor of physics, and her colleagues  extract a protein complex called Photosystem II from spinach they bought at the supermarket. After the protein was extracted, the researchers fired an ultra fast laser that basically acts like sunlight (the protein needs light to activate) and recorded the electron configuration of their molecules. Photosystem II is involved in the photosynthetic mechanism that splits water molecules into oxygen, protons and electrons.

Using the world’s most powerful laser,  the LCLS atthe  Department of Energy’s SLAC National Accelerator Laboratory, the researchers fired fast femtosecond (one-quadrillionth of a second) laser pulses which allowed them to record snapshots of the PSII crystals before they explode in the X-ray beam, a principle called ‘diffraction before destruction. X-rays are great if you want to see structural changes in a crystal, but you can’t see its electron configuration evolution in time.

The Purdue team mimicked the conditions of the serial femtosecond crystallography experiment, but used electron paramagnetic resonance to reveal the electronic configurations of the molecules, Pushkar said. The Purdue team mimicked the conditions of the serial femtosecond crystallography experiment, but used electron paramagnetic resonance to reveal the electronic configurations of the molecules, Pushkar said.

When PSII splits water,  a portion of the protein complex, called the oxygen-evolving complex, cycles through five states in which four electrons are extracted from it. The international team recently revealed the structure of the first and third states at a resolution of 5 and 5.5 Angstroms using the techniques described above.

“The electronic configurations are used to confirm what stage of the process Photosystem II is in at a given time,” she said. “This information is kind of like a time stamp and without it the team wouldn’t have been able to put the structural changes in context.”

Findings appeared in the journal Nature.

artificial_leaf

Progress in artificial leaf development made

What nature seems to perform effortlessly with photosynthesis has proven to be an immense hurdle for scientists trying to mimic it with so called artificial leafs. In recent years, important breakthroughs have been made with this scope in mind, yet the artificial leaf is so inefficient at the moment that it’s absolutely not worth pursuing on a large scale. Researchers at Arizona State University report considerable advances toward perfecting a functional artificial leaf.

artificial_leaf
An artificial photosynthetic reaction center containing a bioinspired electron relay (yellow) mimics some aspects of photosynthesis. Photo: ASU

Plants are extremely efficient at taking carbon dioxide from the air and converting it into biomass using light as an energy source. What scientists are particularly interested in, however, is not in mitigating carbon but using an artificial photosynthesis-like process to break down water into its constituting molecules: hydrogen and oxygen. Hydrogen is one of the most powerful and easy to use fuels at our disposal, the problem is producing it. This is the whole basis of the “hydrogen economy” –  a platform that envisions a world where energy needs are met by hydrogen fuel, cheaply and cleanly obtained. Society requires a renewable source of fuel that is widely distributed, abundant, inexpensive and environmentally clean.

An artificial leaf

The thing is, as scientists first understood some decades ago, mimicking photosynthesis is a whole lot harder than it seems. The researchers took a closer look at how nature had overcome a related problem in the part of the photosynthetic process where water is oxidized to yield oxygen.

“Initially, our artificial leaf did not work very well, and our diagnostic studies on why indicated that a step where a fast chemical reaction had to interact with a slow chemical reaction was not efficient,” said ASU chemistry professor Thomas Moore. “The fast one is the step where light energy is converted to chemical energy, and the slow one is the step where the chemical energy is used to convert water into its elements viz. hydrogen and oxygen.”

“We looked in detail and found that nature had used an intermediate step,” said Moore. “This intermediate step involved a relay for electrons in which one half of the relay interacted with the fast step in an optimal way to satisfy it, and the other half of the relay then had time to do the slow step of water oxidation in an efficient way.”

With this new found knowledge, the researchers constructed an artificial relay based on the natural counterpart. They then designed an artificial relay based on the natural one and were rewarded with a major improvement. X-ray crystallography and optical and magnetic resonance spectroscopy techniques were used to determine and characterize the interactions occurring between electrons and protons participating in the relay. There’s a rather solid theory on proton coupled electron transfer mechanism; with this theoretical work to guide them and the experimental data at hand, the Arizona scientists identified a unique structural feature of the relay. This was an unusually short bond between a hydrogen atom and a nitrogen atom that facilitates the correct working of the relay.

They also found subtle magnetic features of the electronic structure of the artificial relay that mirrored those found in the natural system.

Not only has the artificial system been improved, but the team understands better how the natural system works. This will be important as scientists develop the artificial leaf approach to sustainably harnessing the solar energy needed to provide the food, fuel and fiber that human needs are increasingly demanding.

source: ASU

Fisheye view from a data collection forest tower. (c) Harvard University

Forests become more efficient in response to rising CO2 levels

For years scientists have hypothesized that a rise in CO2 levels will cause the world’s forests to use water more efficiently, however only recently was this theory proven after Harvard University researchers performed the most complex study of the sort to date. The team of researchers  led by research  Trevor Keenan and Andrew Richardson actually found the the world’s forests are more efficient than expected.

“This could be considered a beneficial effect of increased atmospheric carbon dioxide,” said Keenan, the first author of the paper. “What’s surprising is we didn’t expect the effect to be this big. A large proportion of the ecosystems in the world are limited by water. They don’t have enough water during the year to reach their maximum growth. If they become more efficient at using water, they should be able to take more carbon out of the atmosphere due to higher growth rates.”

How does CO2 relate to water use? It’s all tied to the fundamental conversion process plants use to transform CO2 taken from the atmosphere to produce O2 called photosynthesis. During photosynthesis plants open tiny pores, called stomata, on their leaves to collect the CO2. Seeing how there’s more CO2 than they’re traditionally used to, compared to other generations where CO2 levels were lower, the plants do not need to open the stomata  as wide, or for as long. This means a lower energy usage, translating into less water needed and an increase in efficiency. Farmers, for instance, have known this for a while which is why many greenhouses pump extra CO2 to promote crop growth.

So does this mean that the extra CO2 is actually good for the world’s vegetation? In the short-term yes, however in the long term the chain of events that is triggered by an accelerated rise in CO2 trend, such as the one we’re currently on, will have an overall detrimental effect.

“We’re still very concerned about what rising levels of atmospheric carbon dioxide mean for the planet,” Richardson cautioned. “There is little doubt that as carbon dioxide continues to rise — and last month we just passed a critical milestone, 400 ppm, for the first time in human history — rising global temperatures and changes in rainfall patterns will, in coming decades, have very negative consequences for plant growth in many ecosystems around the world.”

Fisheye view from a data collection forest tower. (c) Harvard University

Fisheye view from a data collection forest tower. (c) Harvard University

Testing the CO2 fertilizer effect on the world’s forests, however, is much more difficult to assess since you need a heck load of data. Luckily, Harvard has been monitoring forests in northeast United States for 20 years using towers extending above the forest canopy, allows researchers to determine how much carbon dioxide and water are going into or out of the ecosystem. The researchers also employed data from other 300 towers positioned in forests all over the globe, which however haven’t been deployed for nearly as long as those installed by Harvard, but which still can serve valuable data.

When Keenan, Richardson, and their colleagues began to examine those records, they found that forests were storing more carbon and becoming more efficient in how they used water. These findings were not limited to a particular region of the globe, but rather the trend was observed everywhere.

“We went through every possible hypothesis of what could be going on, and ultimately what we were left with is that the only phenomenon that could cause this type of shift in water-use efficiency is rising atmospheric carbon dioxide,” Keenan said.

Next, the researchers plan on improving their assessment by gaining access to data collected from tropical and Arctic regions.

“This larger dataset will help us to better understand the extent of the response we observed,” he said. “That in turn will help us to build better models, and improve predictions of the future of the Earth’s climate. Right now, all the models we have underrepresent this effect by as much as an order of magnitude, so the question is: What are the models not getting? What do they need to incorporate to capture this effect, and how will that affect their projections for climate change?”

The findings were presented in a paper published in the journal Nature.

Secret of efficient photosynthesis is decoded

When you think about photosynthesis, the color green probably comes to mind – almost all plants are green, and they rely on photosynthesis, right? But purple bacteria have been around for a long time, and they are among the most efficient organisms at turning sunlight into usable chemical energy. Now, a key to their light-harvesting ability has been explained through a detailed structural analysis by scientists at MIT.

ring

Researchers found a ring-shaped molecule with an unusual ninefold symmetry which is critical for the process; the circular symmetry accounts for its efficiency in converting sunlight, and for its mechanical durability and strength. The new study was conducted by professors of chemistry Jianshu Cao and the late Robert Silbey, postdoc Liam Cleary, and graduate students Hang Chen and Chern Chuang, and it has been published in the Proceedings of the National Academy of Sciences.

“The symmetry makes the energy transfer much more robust,” Cao says. “Most biological systems are quite soft and disordered. You would not expect a regular structure, almost a perfect structure,” as is found in this primitive microbe, he says.

As Cao explains,

“nature only used certain symmetry numbers: mostly ninefold, some eightfold, very few tenfold. It’s very selective.” His group’s mathematical analysis shows there are good reasons for that, he says.

These ring shaped molecules are arranged in a hexagonal pattern on the spherical photosynthetic membrane of purple bacteria, Cao says.

“With these symmetry numbers, the interactions between all pairs of the symmetric rings are optimized at the same time. … We believe that nature found the most robust structures in terms of energy transfer,” Cao says. Both eightfold and tenfold symmetries also work, though not as well: Only a lattice made up of ninefold symmetric complexes can tolerate an error in either direction. “You want consecutive numbers so it can tolerate such mistakes,” Cao says.

Stuart Rice, a professor of chemistry at the University of Chicago, says this work is “an inspired analysis and prediction for synthetic materials that is itself inspired by a biological process and system. I have not ever before seen the question of the relationship between energy-transfer efficiency and complexity of packing treated as in this paper. … This is a brilliant analysis that should find immediate acceptance.”

Interestingly enough, the study was funded by the military: National Science Foundation; the Defense Advanced Research Projects Agency; and the MIT Center for Excitonics, funded by the Department of Energy.

Cross section of a mature maize leaf showing Kranz (German for wreath) anatomy around a large vein. The bundle sheath cells (lighter red) encircle the vascular core (light blue). Mesophyll cells (dark red) encircle the bundle sheath cells. The interaction and cooperation between the mesophyll and bundle sheath is essential for the C4 photosynthetic mechanism. (c) Thomas Slewinski

Newly discovered ‘Scarecrow’ gene might yield 50% more efficient crops

Scientists at Cornell University may have stumbled across the cornucopia gene for crops, after scientific investigations revealed that a certain gene allows some plants to photosynthesize 50% more efficient than most common plants, including crops like wheat or rice. The researchers hope through genetic manipulation that they may transfer this gene to crops, allowing for higher yields and an increase in food production destined for an ever demanding and growing population.

Cross section of a mature maize leaf showing Kranz (German for wreath) anatomy around a large vein. The bundle sheath cells (lighter red) encircle the vascular core (light blue). Mesophyll cells (dark red) encircle the bundle sheath cells. The interaction and cooperation between the mesophyll and bundle sheath is essential for the C4 photosynthetic mechanism. (c) Thomas Slewinski

Cross section of a mature maize leaf showing Kranz (German for wreath) anatomy around a large vein. The bundle sheath cells (lighter red) encircle the vascular core (light blue). Mesophyll cells (dark red) encircle the bundle sheath cells. The interaction and cooperation between the mesophyll and bundle sheath is essential for the C4 photosynthetic mechanism. (c) Thomas Slewinski

The gene is responsible for controlling a special leaf structure called the Kranz anatomy, known to render a better photosynthesis efficiency – the ability to turn energy from light into chemical energy. Typically modern plants today photosynthesize using two methods: the C3 method, employed by most older plants like wheat or rice, and the C4 method, a more efficient adaptation employed by grasses, maize, sorghum and sugarcane that is better suited to drought, intense sunlight, heat and low nitrogen.

It is the latter method that scientists are most interested in because of its higher yield potential for crops, however although the underlying mechanisms that allow for a better efficiency had been known, the genetic markups that code this behavior was a mystery until now. It’s no wonder then that massive efforts and funding has been granted in pursuit of transferring C4 mechanics to C3.

The “Scarecrow” gene

“Researchers have been trying to find the underlying genetics of Kranz anatomy so we can engineer it into C3 crops,” said Thomas Slewinski, lead author of a paper that appeared online in November in the journal Plant and Cell Physiology.

[The finding] “provides a clue as to how this whole anatomical key is regulated,” said Turgeon. “There’s still a lot to be learned, but now the barn door is open and you are going to see people working on this Scarecrow pathway.”

Since C4 plants evolved 60 times more compared to C3, which surfaced at a time in Earth’s history when the atmosphere was more rich in carbon dioxide, the C4 adaptation involves Kranz anatomy in the leaves. This entails an extra layer of bundle sheath cells surrounding the veins and outer layer of the mesophyll – a special tissue key to photosynthesis. The mesophyll cells and extra sheath cells layer work together to form a two-step version of photosynthesis, employing different kinds of chloroplasts.

By using a two-step process, C4 plants first shuttle the products of the photosynthesis reaction in the mesophyll, before delivering them to the bundle sheath for RubisCo – an enzyme that facilitates a reaction that captures carbon dioxide from the air, the first step in producing sucrose, the energy-rich product of photosynthesis that powers the plant. In C3 plants, the RubisCo enzyme also facilitates a competing reaction with oxygen, creating a byproduct that has to be degraded, at a cost of about 30-40 percent overall efficiency. In C4 plants this competing oxygen reaction is minimized to the point of it being eliminated, hence the tremendous 50% jump in efficiency.

The findings were published in the journal journal Plant and Cell Physiology.

[source]

Scientists split an atom in two and then fuse it back together

Atom = at·om, noun \ˈa-təm\, from the greek  ἄτομος (atomos) meaning “indivisible”.

Apparently the atom isn’t that indivisible after all. Scientists at University of Bonn have managed to split an atom into two with a special laser, in special conditions, before merging it back together. Just like in the case of light, quantum mechanics allowed an atom to be split and then fused back.

But how is this possible? In quantum mechanics, matter, say an atom, can exist in several different states at once – this formed the absolute basis of the so called “double-slit” experiment for the researchers. For their experiment the scientists successfully manged to keep a single atom in two place at once more than 10 microns apart from one another, an astronomical distance at the atomic scale.

This occurred only because the researchers imposed the right, necessary conditions for the quantum effect to take place. A cesium atom was cooled very close to absolute zero temperature using lasers, and was then moved with the help of another laser. The lasers were absolutely critical to the experiment, being employed to correct the atom’s spin. An atom can spin in both direction – clockwise or counterclockwise; for their current work, the researchers made the atom spin in both directions at the same time.

“The atom has kind of a split personality, half of it is to the right, and half to the left, and yet, it is still whole,” explained Andreas Steffen, the publication’s lead author.

If imaged, the atom sometimes shows on the left, the right, or in the center, but the split can be proved by putting the atom back together

“Thus an interferometer can be built from individual atoms that can, e.g., be used to measure external impacts precisely. Here, the atoms are split, moved apart and joined again. What will become visible, e.g., are differences between the magnetic fields of the two positions or accelerations since they become imprinted in the quantum mechanical state of the atom. This principle has already been used to very precisely survey forces such as Earth’s acceleration.”

Of course, this wasn’t all for show and tell. The researchers hope to better learn not only how to control individual atoms, but how multiple atoms  are linked together using quantum mechanics. This insight can be then used to develop quantum systems, to simulate intricate phenomena, like photosynthesis, which can’t be simulated by today’s supercomputers.

“For us, an atom is a well-controlled and oiled cog,” said Dr. Andrea Alberti, the team lead for the Bonn experiment. “You can build a calculator with remarkable performance using these cogs, but in order for it to work, they have to engage.”

“This is where the actual significance of splitting atoms lies: Because the two halves are put back together again, they can make contact with adjacent atoms to their left and right and then share it. This allows a small network of atoms to form that can be used — like in the memory of a computer — to simulate and control real systems, which would make their secrets more accessible.”

The findings were published in the journal Proceedings of the National Academy of Sciences.

Source: University of Bonn via Planetsave