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    High-speed videos show what happens when a droplet splashes into a pool

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    Rain can freefall at speeds of up to 25 miles per hour. If the droplets land in a puddle or pond, they can form a crown-like splash that, with enough force, can dislodge any surface particles and launch them into the air.Now MIT scientists have taken high-speed videos of droplets splashing into a deep pool, to track how the fluid evolves, above and below the water line, frame by millisecond frame. Their work could help to predict how spashing droplets, such as from rainstorms and irrigation systems, may impact watery surfaces and aerosolize surface particles, such as pollen on puddles or pesticides in agricultural runoff.The team carried out experiments in which they dispensed water droplets of various sizes and from various heights into a pool of water. Using high-speed imaging, they measured how the liquid pool deformed as the impacting droplet hit the pool’s surface.Across all their experiments, they observed a common splash evolution: As a droplet hit the pool, it pushed down below the surface to form a “crater,” or cavity. At nearly the same time, a wall of liquid rose above the surface, forming a crown. Interestingly, the team observed that small, secondary droplets were ejected from the crown before the crown reached its maximum height. This entire evolution happens in a fraction of a second.

    “This cylinder-like wall of rising liquid, and how it evolves in time and space, is at the heart of everything,” Lydia Bourouiba says. GIF has been edited down to 5 frames per second.

    Image: Courtesy of the researchers; edited by MIT News

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    Scientists have caught snapshots of droplet splashes in the past, such as the famous “Milk Drop Coronet” — a photo of a drop of milk in mid-splash, taken by the late MIT professor Harold “Doc” Edgerton, who invented a photographic technique to capture quickly moving objects.The new work represents the first time scientists have used such high-speed images to model the entire splash dynamics of a droplet in a deep pool, combining what happens both above and below the surface. The team has used the imaging to gather new data central to build a mathematical model that predicts how a droplet’s shape will morph and merge as it hits a pool’s surface. They plan to use the model as a baseline to explore to what extent a splashing droplet might drag up and launch particles from the water pool.“Impacts of drops on liquid layers are ubiquitous,” says study author Lydia Bourouiba, a professor in the MIT departments of Civil and Environmental Engineering and Mechanical Engineering, and a core member of the Institute for Medical Engineering and Science (IMES). “Such impacts can produce myriads of secondary droplets that could act as carriers for pathogens, particles, or microbes that are on the surface of impacted pools or contaminated water bodies. This work is key in enabling prediction of droplet size distributions, and potentially also what such drops can carry with them.”Bourouiba and her mentees have published their results in the Journal of Fluid Mechanics. MIT co-authors include former graduate student Raj Dandekar PhD ’22, postdoc (Eric) Naijian Shen, and student mentee Boris Naar.Above and belowAt MIT, Bourouiba heads up the Fluid Dynamics of Disease Transmission Laboratory, part of the Fluids and Health Network, where she and her team explore the fundamental physics of fluids and droplets in a range of environmental, energy, and health contexts, including disease transmission. For their new study, the team looked to better understand how droplets impact a deep pool — a seemingly simple phenomenon that nevertheless has been tricky to precisely capture and characterize.Bourouiba notes that there have been recent breakthroughs in modeling the evolution of a splashing droplet below a pool’s surface. As a droplet hits a pool of water, it breaks through the surface and drags air down through the pool to create a short-lived crater. Until now, scientists have focused on the evolution of this underwater cavity, mainly for applications in energy harvesting. What happens above the water, and how a droplet’s crown-like shape evolves with the cavity below, remained less understood.“The descriptions and understanding of what happens below the surface, and above, have remained very much divorced,” says Bourouiba, who believes such an understanding can help to predict how droplets launch and spread chemicals, particles, and microbes into the air.Splash in 3DTo study the coupled dynamics between a droplet’s cavity and crown, the team set up an experiment to dispense water droplets into a deep pool. For the purposes of their study, the researchers considered a deep pool to be a body of water that is deep enough that a splashing droplet would remain far away from the pool’s bottom. In these terms, they found that a pool with a depth of at least 20 centimeters was sufficient for their experiments.They varied each droplet’s size, with an average diameter of about 5 millimeters. They also dispensed droplets from various heights, causing the droplets to hit the pool’s surface at different speeds, which on average was about 5 meters per second. The overall dynamics, Bourouiba says, should be similar to what occurs on the surface of a puddle or pond during an average rainstorm.“This is capturing the speed at which raindrops fall,” she says. “These wouldn’t be very small, misty drops. This would be rainstorm drops for which one needs an umbrella.”Using high-speed imaging techniques inspired by Edgerton’s pioneering photography, the team captured videos of pool-splashing droplets, at rates of up to 12,500 frames per second. They then applied in-house imaging processing methods to extract key measurements from the image sequences, such as the changing width and depth of the underwater cavity, and the evolving diameter and height of the rising crown. The researchers also captured especially tricky measurements, of the crown’s wall thickness profile and inner flow — the cylinder that rises out of the pool, just before it forms a rim and points that are characteristic of a crown.“This cylinder-like wall of rising liquid, and how it evolves in time and space, is at the heart of everything,” Bourouiba says. “It’s what connects the fluid from the pool to what will go into the rim and then be ejected into the air through smaller, secondary droplets.”The researchers worked the image data into a set of “evolution equations,” or a mathematical model that relates the various properties of an impacting droplet, such as the width of its cavity and the thickness and speed profiles of its crown wall, and how these properties change over time, given a droplet’s starting size and impact speed.“We now have a closed-form mathematical expression that people can use to see how all these quantities of a splashing droplet change over space and time,” says co-author Shen, who plans, with Bourouiba, to apply the new model to the behavior of secondary droplets and understanding how a splash end-up dispersing particles such as pathogens and pesticides. “This opens up the possibility to study all these problems of splash in 3D, with self-contained closed-formed equations, which was not possible before.”This research was supported, in part, by the Department of Agriculture-National Institute of Food and Agriculture Specialty Crop Research Initiative; the Richard and Susan Smith Family Foundation; the National Science Foundation; the Centers for Disease Control and Prevention-National Institute for Occupational Safety and Health; Inditex; and the National Institute of Allergy and Infectious Diseases of the National Institutes of Health. 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      in Security

      Pivot Bio is using microbial nitrogen to make agriculture more sustainable

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      The Haber-Bosch process, which converts atmospheric nitrogen to make ammonia fertilizer, revolutionized agriculture and helped feed the world’s growing population, but it also created huge environmental problems. It is one of the most energy-intensive chemical processes in the world, responsible for 1-2 percent of global energy consumption. It also releases nitrous oxide, a potent greenhouse gas that harms the ozone layer. Excess nitrogen also routinely runs off farms into waterways, harming marine life and polluting groundwater.In place of synthetic fertilizer, Pivot Bio has engineered nitrogen-producing microbes to make farming more sustainable. The company, which was co-founded by Professor Chris Voigt, Karsten Temme, and Alvin Tamsir, has engineered its microbes to grow on plant roots, where they feed on the root’s sugars and precisely deliver nitrogen in return.Pivot’s microbial colonies grow with the plant and produce more nitrogen at exactly the time the plant needs it, minimizing nitrogen runoff.“The way we have delivered nutrients to support plant growth historically is fertilizer, but that’s an inefficient way to get all the nutrients you need,” says Temme, Pivot’s chief innovation officer. “We have the ability now to help farmers be more efficient and productive with microbes.”Farmers can replace up to 40 pounds per acre of traditional nitrogen with Pivot’s product, which amounts to about a quarter of the total nitrogen needed for a crop like corn.Pivot’s products are already being used to grow corn, wheat, barley, oats, and other grains across millions of acres of American farmland, eliminating hundreds of thousands of tons of CO2 equivalent in the process. The company’s impact is even more striking given its unlikely origins, which trace back to one of the most challenging times of Voigt’s career.A Pivot from despairThe beginning of every faculty member’s career can be a sink-or-swim moment, and by Voigt’s own account, he was drowning. As a freshly minted assistant professor at the University of California at San Francisco, Voigt was struggling to stand up his lab, attract funding, and get experiments started.Around 2008, Voigt joined a research group out of the University of California at Berkeley that was writing a grant proposal focused on photovoltaic materials. His initial role was minor, but a senior researcher pulled out of the group a week before the proposal had to be submitted, so Voigt stepped up.“I said ‘I’ll finish this section in a week,’” Voigt recalls. “It was my big chance.”For the proposal, Voigt detailed an ambitious plan to rearrange the genetics of biologic photosynthetic systems to make them more efficient. He barely submitted it in time.A few months went by, then the proposal reviews finally came back. Voigt hurried to the meeting with some of the most senior researchers at UC Berkeley to discuss the responses.“My part of the proposal got completely slammed,” Voigt says. “There were something like 15 reviews on it — they were longer than the actual grant — and it’s just one after another tearing into my proposal. All the most famous people are in this meeting, future energy secretaries, future leaders of the university, and it was totally embarrassing. After that meeting, I was considering leaving academia.”A few discouraging months later, Voigt got a call from Paul Ludden, the dean of the School of Science at UC Berkeley. He wanted to talk.“As I walk into Paul’s office, he’s reading my proposal,” Voigt recalls. “He sits me down and says, ‘Everybody’s telling me how terrible this is.’ I’m thinking, ‘Oh my God.’ But then he says, ‘I think there’s something here. Your idea is good, you just picked the wrong system.’”Ludden went on to explain to Voigt that he should apply his gene-swapping idea to nitrogen fixation. He even offered to send Voigt a postdoc from his lab, Dehua Zhao, to help. Voigt paired Zhao with Temme, and sure enough, the resulting 2011 paper of their work was well-received by the nitrogen fixation community.“Nitrogen fixation has been a holy grail for scientists, agronomists, and farmers for almost a century, ever since somebody discovered the first microbe that can fix nitrogen for legumes like soybeans,” Temme says. “Everybody always said that someday we’ll be able to do this for the cereal crops. The excitement with Pivot was this is the first time that technology became accessible.”Voigt had moved to MIT in 2010. When the paper came out, he founded Pivot Bio with Temme and another Berkeley researcher, Alvin Tamsir. Since then, Voigt, who is the Daniel I.C. Wang Professor at MIT and the head of the Department of Biological Engineering, has continued collaborating with Pivot on things like increasing nitrogen production, making strains more stable, and making them inducible to different signals from the plant. Pivot has licensed technology from MIT, and the research has also received support from MIT’s Abdul Latif Jameel Water and Food Systems Lab (J-WAFS).Pivot’s first goals were to gain regulatory approval and prove themselves in the marketplace. To gain approval in the U.S., Pivot’s team focused on using DNA from within the same organism rather than bringing in totally new DNA, which simplified the approval process. It also partnered with independent corn seed dealers to get its product to farms. Early deployments occurred in 2019.Farmers apply Pivot’s product at planting, either as a liquid that gets sprayed on the soil or as a dry powder that is rehydrated and applied to the seeds as a coating. The microbes live on the surface of the growing root system, eating plant sugars and releasing nitrogen throughout the plant’s life cycle.“Today, our microbes colonize just a fraction of the total sugars provided by the plant,” Temme explains. “They’re also sharing ammonia with the plant, and all of those things are just a portion of what’s possible technically. Our team is always trying to figure out how to make those microbes more efficient at getting the energy they need to grow or at fixing nitrogen and sharing it with the crop.”In 2023, Pivot started the N-Ovator program to connect companies with growers who practice sustainable farming using Pivot’s microbial nitrogen. Through the program, companies buy nitrogen credits and farmers can get paid by verifying their practices. The program was named one of the Inventions of the Year by Time Magazine last year and has paid out millions of dollars to farmers to date.Microbial nitrogen and beyondPivot is currently selling to farmers across the U.S. and working with smallholder farmers in Kenya. It’s also hoping to gain approval for its microbial solution in Brazil and Canada, which it hopes will be its next markets.”How do we get the economics to make sense for everybody — the farmers, our partners, and the company?” Temme says of Pivot’s mission. “Because this truly can be a deflationary technology that upends the very expensive traditional way of making fertilizer.”Pivot’s team is also extending the product to cotton, and Temme says microbes can be a nitrogen source for any type of plant on the planet. Further down the line, the company believes it can help farmers with other nutrients essential to help their crops grow.“Now that we’ve established our technology, how can Pivot help farmers overcome all the other limitations they face with crop nutrients to maximize yields?” Temme asks. “That really starts to change the way a farmer thinks about managing the entire acre from a price, productivity, and sustainability perspective.” More

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      in Environment

      Seeking climate connections among the oceans’ smallest organisms

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      Andrew Babbin tries to pack light for work trips. Along with the travel essentials, though, he also brings a roll each of electrical tape, duct tape, lab tape, a pack of cable ties, and some bungee cords.“It’s my MacGyver kit: You never know when you have to rig something on the fly in the field or fix a broken bag,” Babbin says.The trips Babbin takes are far out to sea, on month-long cruises, where he works to sample waters off the Pacific coast and out in the open ocean. In remote locations, repair essentials often come in handy, as when Babbin had to zip-tie a wrench to a sampling device to help it sink through an icy Antarctic lake.Babbin is an oceanographer and marine biogeochemist who studies marine microbes and the ways in which they control the cycling of nitrogen between the ocean and the atmosphere. This exchange helps maintain healthy ocean ecosystems and supports the ocean’s capacity to store carbon.By combining measurements that he takes in the ocean with experiments in his MIT lab, Babbin is working to understand the connections between microbes and ocean nitrogen, which could in turn help scientists identify ways to maintain the ocean’s health and productivity. His work has taken him to many coastal and open-ocean regions around the globe.“You really become an oceanographer and an Earth scientist to see the world,” says Babbin, who recently earned tenure as the Cecil and Ida Green Career Development Professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “We embrace the diversity of places and cultures on this planet. To see just a small fraction of that is special.”A powerful cycleThe ocean has been a constant presence for Babbin since childhood. His family is from Monmouth County, New Jersey, where he and his twin sister grew up playing along the Jersey shore. When they were teenagers, their parents took the kids on family cruise vacations.“I always loved being on the water,” he says. “My favorite parts of any of those cruises were the days at sea, where you were just in the middle of some ocean basin with water all around you.”In school, Babbin gravitated to the sciences, and chemistry in particular. After high school, he attended Columbia University, where a visit to the school’s Earth and environmental engineering department catalyzed a realization.“For me, it was always this excitement about the water and about chemistry, and it was this pop of, ‘Oh wow, it doesn’t have to be one or the other,’” Babbin says.He chose to major in Earth and environmental engineering, with a concentration in water resources and climate risks. After graduating in 2008, Babbin returned to his home state, where he attended Princeton University and set a course for a PhD in geosciences, with a focus on chemical oceanography and environmental microbiology. His advisor, oceanographer Bess Ward, took Babbin on as a member of her research group and invited him on several month-long cruises to various parts of the eastern tropical Pacific.“I still remember that first trip,” Babbin recalls. “It was a whirlwind. Everyone else had been to sea a gazillion times and was loading the boat and strapping things down, and I had no idea of anything. And within a few hours, I was doing an experiment as the ship rocked back and forth!”Babbin learned to deploy sampling cannisters overboard, then haul them back up and analyze the seawater inside for signs of nitrogen — an essential nutrient for all living things on Earth.As it turns out, the plants and animals that depend on nitrogen to survive are unable to take it up from the atmosphere themselves. They require a sort of go-between, in the form of microbes that “fix” nitrogen, converting it from nitrogen gas to more digestible forms. In the ocean, this nitrogen fixation is done by highly specialized microbial species, which work to make nitrogen available to phytoplankton — microscopic plant-like organisms that are the foundation of the marine food chain. Phytoplankton are also a main route by which the ocean absorbs carbon dioxide from the atmosphere.Microorganisms may also use these biologically available forms of nitrogen for energy under certain conditions, returning nitrogen to the atmosphere. These microbes can also release a byproduct of nitrous oxide, which is a potent greenhouse gas that also can catalyze ozone loss in the stratosphere.Through his graduate work, at sea and in the lab, Babbin became fascinated with the cycling of nitrogen and the role that nitrogen-fixing microbes play in supporting the ocean’s ecosystems and the climate overall. A balance of nitrogen inputs and outputs sustains phytoplankton and maintains the ocean’s ability to soak up carbon dioxide.“Some of the really pressing questions in ocean biogeochemistry pertain to this cycling of nitrogen,” Babbin says. “Understanding the ways in which this one element cycles through the ocean, and how it is central to ecosystem health and the planet’s climate, has been really powerful.”In the lab and out to seaAfter completing his PhD in 2014, Babbin arrived at MIT as a postdoc in the Department of Civil and Environmental Engineering.“My first feeling when I came here was, wow, this really is a nerd’s playground,” Babbin says. “I embraced being part of a culture where we seek to understand the world better, while also doing the things we really want to do.”In 2017, he accepted a faculty position in MIT’s Department of Earth, Atmospheric and Planetary Sciences. He set up his laboratory space, painted in his favorite brilliant orange, on the top floor of the Green Building.His group uses 3D printers to fabricate microfluidic devices in which they reproduce the conditions of the ocean environment and study microbe metabolism and its effects on marine chemistry. In the field, Babbin has led research expeditions to the Galapagos Islands and parts of the eastern Pacific, where he has collected and analyzed samples of air and water for signs of nitrogen transformations and microbial activity. His new measuring station in the Galapagos is able to infer marine emissions of nitrous oxide across a large swath of the eastern tropical Pacific Ocean. His group has also sailed to southern Cuba, where the researchers studied interactions of microbes in coral reefs.Most recently, Babbin traveled to Antarctica, where he set up camp next to frozen lakes and plumbed for samples of pristine ice water that he will analyze for genetic remnants of ancient microbes. Such preserved bacterial DNA could help scientists understand how microbes evolved and influenced the Earth’s climate over billions of years.“Microbes are the terraformers,” Babbin notes. “They have been, since life evolved more than 3 billion years ago. We have to think about how they shape the natural world and how they will respond to the Anthropocene as humans monkey with the planet ourselves.”Collective actionBabbin is now charting new research directions. In addition to his work at sea and in the lab, he is venturing into engineering, with a new project to design denitrifying capsules. While nitrogen is an essential nutrient for maintaining a marine ecosystem, too much nitrogen, such as from fertilizer that runs off into lakes and streams, can generate blooms of toxic algae. Babbin is looking to design eco-friendly capsules that scrub excess anthropogenic nitrogen from local waterways. He’s also beginning the process of designing a new sensor to measure low-oxygen concentrations in the ocean. As the planet warms, the oceans are losing oxygen, creating “dead zones” where fish cannot survive. While others including Babbin have tried to map these oxygen minimum zones, or OMZs, they have done so sporadically, by dropping sensors into the ocean over limited range, depth, and times. Babbin’s sensors could potentially provide a more complete map of OMZs, as they would be deployed on wide-ranging, deep-diving, and naturally propulsive vehicles: sharks.“We want to measure oxygen. Sharks need oxygen. And if you look at where the sharks don’t go, you might have a sense of where the oxygen is not,” says Babbin, who is working with marine biologists on ways to tag sharks with oxygen sensors. “A number of these large pelagic fish move up and down the water column frequently, so you can map the depth to which they dive to, and infer something about the behavior. And my suggestion is, you might also infer something about the ocean’s chemistry.”When he reflects on what stimulates new ideas and research directions, Babbin credits working with others, in his own group and across MIT.“My best thoughts come from this collective action,” Babbin says. “Particularly because we all have different upbringings and approach things from a different perspective.”He’s bringing this collaborative spirit to his new role, as a mission director for MIT’s Climate Project. Along with Jesse Kroll, who is a professor of civil and environmental engineering and of chemical engineering, Babbin co-leads one of the project’s six missions: Restoring the Atmosphere, Protecting the Land and Oceans. Babbin and Kroll are planning a number of workshops across campus that they hope will generate new connections, and spark new ideas, particularly around ways to evaluate the effectiveness of different climate mitigation strategies and better assess the impacts of climate on society.“One area we want to promote is thinking of climate science and climate interventions as two sides of the same coin,” Babbin says. “There’s so much action that’s trying to be catalyzed. But we want it to be the best action. Because we really have one shot at doing this. Time is of the essence.” More

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      in Environment

      An abundant phytoplankton feeds a global network of marine microbes

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      One of the hardest-working organisms in the ocean is the tiny, emerald-tinged Prochlorococcus marinus. These single-celled “picoplankton,” which are smaller than a human red blood cell, can be found in staggering numbers throughout the ocean’s surface waters, making Prochlorococcus the most abundant photosynthesizing organism on the planet. (Collectively, Prochlorococcus fix as much carbon as all the crops on land.) Scientists continue to find new ways that the little green microbe is involved in the ocean’s cycling and storage of carbon.Now, MIT scientists have discovered a new ocean-regulating ability in the small but mighty microbes: cross-feeding of DNA building blocks. In a study appearing today in Science Advances, the team reports that Prochlorococcus shed these extra compounds into their surroundings, where they are then “cross-fed,” or taken up by other ocean organisms, either as nutrients, energy, or for regulating metabolism. Prochlorococcus’ rejects, then, are other microbes’ resources.What’s more, this cross-feeding occurs on a regular cycle: Prochlorococcus tend to shed their molecular baggage at night, when enterprising microbes quickly consume the cast-offs. For a microbe called SAR11, the most abundant bacteria in the ocean, the researchers found that the nighttime snack acts as a relaxant of sorts, forcing the bacteria to slow down their metabolism and effectively recharge for the next day.Through this cross-feeding interaction, Prochlorococcus could be helping many microbial communities to grow sustainably, simply by giving away what it doesn’t need. And they’re doing so in a way that could set the daily rhythms of microbes around the world.“The relationship between the two most abundant groups of microbes in ocean ecosystems has intrigued oceanographers for years,” says co-author and MIT Institute Professor Sallie “Penny” Chisholm, who played a role in the discovery of Prochlorococcus in 1986. “Now we have a glimpse of the finely tuned choreography that contributes to their growth and stability across vast regions of the oceans.”Given that Prochlorococcus and SAR11 suffuse the surface oceans, the team suspects that the exchange of molecules from one to the other could amount to one of the major cross-feeding relationships in the ocean, making it an important regulator of the ocean carbon cycle.“By looking at the details and diversity of cross-feeding processes, we can start to unearth important forces that are shaping the carbon cycle,” says the study’s lead author, Rogier Braakman, a research scientist in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS).Other MIT co-authors include Brandon Satinsky, Tyler O’Keefe, Shane Hogle, Jamie Becker, Robert Li, Keven Dooley, and Aldo Arellano, along with Krista Longnecker, Melissa Soule, and Elizabeth Kujawinski of Woods Hole Oceanographic Institution (WHOI).Spotting castawaysCross-feeding occurs throughout the microbial world, though the process has mainly been studied in close-knit communities. In the human gut, for instance, microbes are in close proximity and can easily exchange and benefit from shared resources.By comparison, Prochlorococcus are free-floating microbes that are regularly tossed and mixed through the ocean’s surface layers. While scientists assume that the plankton are involved in some amount of cross-feeding, exactly how this occurs, and who would benefit, have historically been challenging to probe; any stuff that Prochlorococcus cast away would have vanishingly low concentrations,and be exceedingly difficult to measure.But in work published in 2023, Braakman teamed up with scientists at WHOI, who pioneered ways to measure small organic compounds in seawater. In the lab, they grew various strains of Prochlorococcus under different conditions and characterized what the microbes released. They found that among the major “exudants,” or released molecules, were purines and pyridines, which are molecular building blocks of DNA. The molecules also happen to be nitrogen-rich — a fact that puzzled the team. Prochlorococcus are mainly found in ocean regions that are low in nitrogen, so it was assumed they’d want to retain any and all nitrogen-containing compounds they can. Why, then, were they instead throwing such compounds away?Global symphonyIn their new study, the researchers took a deep dive into the details of Prochlorococcus’ cross-feeding and how it influences various types of ocean microbes.They set out to study how Prochlorococcus use purine and pyridine in the first place, before expelling the compounds into their surroundings. They compared published genomes of the microbes, looking for genes that encode purine and pyridine metabolism. Tracing the genes forward through the genomes, the team found that once the compounds are produced, they are used to make DNA and replicate the microbes’ genome. Any leftover purine and pyridine is recycled and used again, though a fraction of the stuff is ultimately released into the environment. Prochlorococcus appear to make the most of the compounds, then cast off what they can’t.The team also looked to gene expression data and found that genes involved in recycling purine and pyrimidine peak several hours after the recognized peak in genome replication that occurs at dusk. The question then was: What could be benefiting from this nightly shedding?For this, the team looked at the genomes of more than 300 heterotrophic microbes — organisms that consume organic carbon rather than making it themselves through photosynthesis. They suspected that such carbon-feeders could be likely consumers of Prochlorococcus’ organic rejects. They found most of the heterotrophs contained genes that take up either purine or pyridine, or in some cases, both, suggesting microbes have evolved along different paths in terms of how they cross-feed.The group zeroed in on one purine-preferring microbe, SAR11, as it is the most abundant heterotrophic microbe in the ocean. When they then compared the genes across different strains of SAR11, they found that various types use purines for different purposes, from simply taking them up and using them intact to breaking them down for their energy, carbon, or nitrogen. What could explain the diversity in how the microbes were using Prochlorococcus’ cast-offs?It turns out the local environment plays a big role. Braakman and his collaborators performed a metagenome analysis in which they compared the collectively sequenced genomes of all microbes in over 600 seawater samples from around the world, focusing on SAR11 bacteria. Metagenome sequences were collected alongside measurements of various environmental conditions and geographic locations in which they are found. This analysis showed that the bacteria gobble up purine for its nitrogen when the nitrogen in seawater is low, and for its carbon or energy when nitrogen is in surplus — revealing the selective pressures shaping these communities in different ocean regimes.“The work here suggests that microbes in the ocean have developed relationships that advance their growth potential in ways we don’t expect,” says co-author Kujawinski.Finally, the team carried out a simple experiment in the lab, to see if they could directly observe a mechanism by which purine acts on SAR11. They grew the bacteria in cultures, exposed them to various concentrations of purine, and unexpectedly found it causes them to slow down their normal metabolic activities and even growth. However, when the researchers put these same cells under environmentally stressful conditions, they continued growing strong and healthy cells, as if the metabolic pausing by purines helped prime them for growth, thereby avoiding the effects of the stress.“When you think about the ocean, where you see this daily pulse of purines being released by Prochlorococcus, this provides a daily inhibition signal that could be causing a pause in SAR11 metabolism, so that the next day when the sun comes out, they are primed and ready,” Braakman says. “So we think Prochlorococcus is acting as a conductor in the daily symphony of ocean metabolism, and cross-feeding is creating a global synchronization among all these microbial cells.”This work was supported, in part, by the Simons Foundation and the National Science Foundation. More

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      in Security

      Repurposed beer yeast may offer a cost-effective way to remove lead from water

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      Every year, beer breweries generate and discard thousands of tons of surplus yeast. Researchers from MIT and Georgia Tech have now come up with a way to repurpose that yeast to absorb lead from contaminated water.Through a process called biosorption, yeast can quickly absorb even trace amounts of lead and other heavy metals from water. The researchers showed that they could package the yeast inside hydrogel capsules to create a filter that removes lead from water. Because the yeast cells are encapsulated, they can be easily removed from the water once it’s ready to drink.“We have the hydrogel surrounding the free yeast that exists in the center, and this is porous enough to let water come in, interact with yeast as if they were freely moving in water, and then come out clean,” says Patricia Stathatou, a former postdoc at the MIT Center for Bits and Atoms, who is now a research scientist at Georgia Tech and an incoming assistant professor at Georgia Tech’s School of Chemical and Biomolecular Engineering. “The fact that the yeast themselves are bio-based, benign, and biodegradable is a significant advantage over traditional technologies.”The researchers envision that this process could be used to filter drinking water coming out of a faucet in homes, or scaled up to treat large quantities of water at treatment plants.MIT graduate student Devashish Gokhale and Stathatou are the lead authors of the study, which appears today in the journal RSC Sustainability. Patrick Doyle, the Robert T. Haslam Professor of Chemical Engineering at MIT, is the senior author of the paper, and Christos Athanasiou, an assistant professor of aerospace engineering at Georgia Tech and a former visiting scholar at MIT, is also an author.Absorbing leadThe new study builds on work that Stathatou and Athanasiou began in 2021, when Athanasiou was a visiting scholar at MIT’s Center for Bits and Atoms. That year, they calculated that waste yeast discarded from a single brewery in Boston would be enough to treat the city’s entire water supply.Through biosorption, a process that is not fully understood, yeast cells can bind to and absorb heavy metal ions, even at challenging initial concentrations below 1 part per million. The MIT team found that this process could effectively decontaminate water with low concentrations of lead. However, one key obstacle remained, which was how to remove yeast from the water after they absorb the lead.In a serendipitous coincidence, Stathatou and Athanasiou happened to present their research at the AIChE Annual Meeting in Boston in 2021, where Gokhale, a student in Doyle’s lab, was presenting his own research on using hydrogels to capture micropollutants in water. The two sets of researchers decided to join forces and explore whether the yeast-based strategy could be easier to scale up if the yeast were encapsulated in hydrogels developed by Gokhale and Doyle.“What we decided to do was make these hollow capsules — something like a multivitamin pill, but instead of filling them up with vitamins, we fill them up with yeast cells,” Gokhale says. “These capsules are porous, so the water can go into the capsules and the yeast are able to bind all of that lead, but the yeast themselves can’t escape into the water.”The capsules are made from a polymer called polyethylene glycol (PEG), which is widely used in medical applications. To form the capsules, the researchers suspend freeze-dried yeast in water, then mix them with the polymer subunits. When UV light is shone on the mixture, the polymers link together to form capsules with yeast trapped inside.Each capsule is about half a millimeter in diameter. Because the hydrogels are very thin and porous, water can easily pass through and encounter the yeast inside, while the yeast remain trapped.In this study, the researchers showed that the encapsulated yeast could remove trace lead from water just as rapidly as the unencapsulated yeast from Stathatou and Athanasiou’s original 2021 study.Scaling upLed by Athanasiou, the researchers tested the mechanical stability of the hydrogel capsules and found that the capsules and the yeast inside can withstand forces similar to those generated by water running from a faucet. They also calculated that the yeast-laden capsules should be able to withstand forces generated by flows in water treatment plants serving several hundred residences.“Lack of mechanical robustness is a common cause of failure of previous attempts to scale-up biosorption using immobilized cells; in our work we wanted to make sure that this aspect is thoroughly addressed from the very beginning to ensure scalability,” Athanasiou says.After assessing the mechanical robustness of the yeast-laden capsules, the researchers constructed a proof-of-concept packed-bed biofilter, capable of treating trace lead-contaminated water and meeting U.S. Environmental Protection Agency drinking water guidelines while operating continuously for 12 days.This process would likely consume less energy than existing physicochemical processes for removing trace inorganic compounds from water, such as precipitation and membrane filtration, the researchers say.This approach, rooted in circular economy principles, could minimize waste and environmental impact while also fostering economic opportunities within local communities. Although numerous lead contamination incidents have been reported in various locations in the United States, this approach could have an especially significant impact in low-income areas that have historically faced environmental pollution and limited access to clean water, and may not be able to afford other ways to remediate it, the researchers say.“We think that there’s an interesting environmental justice aspect to this, especially when you start with something as low-cost and sustainable as yeast, which is essentially available anywhere,” Gokhale says.The researchers are now exploring strategies for recycling and replacing the yeast once they’re used up, and trying to calculate how often that will need to occur. They also hope to investigate whether they could use feedstocks derived from biomass to make the hydrogels, instead of fossil-fuel-based polymers, and whether the yeast can be used to capture other types of contaminants.“Moving forward, this is a technology that can be evolved to target other trace contaminants of emerging concern, such as PFAS or even microplastics,” Stathatou says. “We really view this as an example with a lot of potential applications in the future.”The research was funded by the Rasikbhai L. Meswani Fellowship for Water Solutions, the MIT Abdul Latif Jameel Water and Food Systems Lab (J-WAFS), and the Renewable Bioproducts Institute at Georgia Tech. More

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      in Environment

      A mineral produced by plate tectonics has a global cooling effect, study finds

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      MIT geologists have found that a clay mineral on the seafloor, called smectite, has a surprisingly powerful ability to sequester carbon over millions of years.

      Under a microscope, a single grain of the clay resembles the folds of an accordion. These folds are known to be effective traps for organic carbon.

      Now, the MIT team has shown that the carbon-trapping clays are a product of plate tectonics: When oceanic crust crushes against a continental plate, it can bring rocks to the surface that, over time, can weather into minerals including smectite. Eventually, the clay sediment settles back in the ocean, where the minerals trap bits of dead organisms in their microscopic folds. This keeps the organic carbon from being consumed by microbes and expelled back into the atmosphere as carbon dioxide.

      Over millions of years, smectite can have a global effect, helping to cool the entire planet. Through a series of analyses, the researchers showed that smectite was likely produced after several major tectonic events over the last 500 million years. During each tectonic event, the clays trapped enough carbon to cool the Earth and induce the subsequent ice age.

      The findings are the first to show that plate tectonics can trigger ice ages through the production of carbon-trapping smectite.

      These clays can be found in certain tectonically active regions today, and the scientists believe that smectite continues to sequester carbon, providing a natural, albeit slow-acting, buffer against humans’ climate-warming activities.

      “The influence of these unassuming clay minerals has wide-ranging implications for the habitability of planets,” says Joshua Murray, a graduate student in MIT’s Department of Earth, Atmospheric, and Planetary Sciences. “There may even be a modern application for these clays in offsetting some of the carbon that humanity has placed into the atmosphere.”

      Murray and Oliver Jagoutz, professor of geology at MIT, have published their findings today in Nature Geoscience.

      A clear and present clay

      The new study follows up on the team’s previous work, which showed that each of the Earth’s major ice ages was likely triggered by a tectonic event in the tropics. The researchers found that each of these tectonic events exposed ocean rocks called ophiolites to the atmosphere. They put forth the idea that, when a tectonic collision occurs in a tropical region, ophiolites can undergo certain weathering effects, such as exposure to wind, rain, and chemical interactions, that transform the rocks into various minerals, including clays.

      “Those clay minerals, depending on the kinds you create, influence the climate in different ways,” Murray explains.

      At the time, it was unclear which minerals could come out of this weathering effect, and whether and how these minerals could directly contribute to cooling the planet. So, while it appeared there was a link between plate tectonics and ice ages, the exact mechanism by which one could trigger the other was still in question.

      With the new study, the team looked to see whether their proposed tectonic tropical weathering process would produce carbon-trapping minerals, and in quantities that would be sufficient to trigger a global ice age.

      The team first looked through the geologic literature and compiled data on the ways in which major magmatic minerals weather over time, and on the types of clay minerals this weathering can produce. They then worked these measurements into a weathering simulation of different rock types that are known to be exposed in tectonic collisions.

      “Then we look at what happens to these rock types when they break down due to weathering and the influence of a tropical environment, and what minerals form as a result,” Jagoutz says.

      Next, they plugged each weathered, “end-product” mineral into a simulation of the Earth’s carbon cycle to see what effect a given mineral might have, either in interacting with organic carbon, such as bits of dead organisms, or with inorganic, in the form of carbon dioxide in the atmosphere.

      From these analyses, one mineral had a clear presence and effect: smectite. Not only was the clay a naturally weathered product of tropical tectonics, it was also highly effective at trapping organic carbon. In theory, smectite seemed like a solid connection between tectonics and ice ages.

      But were enough of the clays actually present to trigger the previous four ice ages? Ideally, researchers should confirm this by finding smectite in ancient rock layers dating back to each global cooling period.

      “Unfortunately, as clays are buried by other sediments, they get cooked a bit, so we can’t measure them directly,” Murray says. “But we can look for their fingerprints.”

      A slow build

      The team reasoned that, as smectites are a product of ophiolites, these ocean rocks also bear characteristic elements such as nickel and chromium, which would be preserved in ancient sediments. If smectites were present in the past, nickel and chromium should be as well.

      To test this idea, the team looked through a database containing thousands of oceanic sedimentary rocks that were deposited over the last 500 million years. Over this time period, the Earth experienced four separate ice ages. Looking at rocks around each of these periods, the researchers observed large spikes of nickel and chromium, and inferred from this that smectite must also have been present.

      By their estimates, the clay mineral could have increased the preservation of organic carbon by less than one-tenth of a percent. In absolute terms, this is a miniscule amount. But over millions of years, they calculated that the clay’s accumulated, sequestered carbon was enough to trigger each of the four major ice ages.

      “We found that you really don’t need much of this material to have a huge effect on the climate,” Jagoutz says.

      “These clays also have probably contributed some of the Earth’s cooling in the last 3 to 5 million years, before humans got involved,” Murray adds. “In the absence of humans, these clays are probably making a difference to the climate. It’s just such a slow process.”

      “Jagoutz and Murray’s work is a nice demonstration of how important it is to consider all biotic and physical components of the global carbon cycle,” says Lee Kump, a professor of geosciences at Penn State University, who was not involved with the study. “Feedbacks among all these components control atmospheric greenhouse gas concentrations on all time scales, from the annual rise and fall of atmospheric carbon dioxide levels to the swings from icehouse to greenhouse over millions of years.”

      Could smectites be harnessed intentionally to further bring down the world’s carbon emissions? Murray sees some potential, for instance to shore up carbon reservoirs such as regions of permafrost. Warming temperatures are predicted to melt permafrost and expose long-buried organic carbon. If smectites could be applied to these regions, the clays could prevent this exposed carbon from escaping into and further warming the atmosphere.

      “If you want to understand how nature works, you have to understand it on the mineral and grain scale,” Jagoutz says. “And this is also the way forward for us to find solutions for this climatic catastrophe. If you study these natural processes, there’s a good chance you will stumble on something that will be actually useful.”

      This research was funded, in part, by the National Science Foundation. More

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      in Security

      Microbes could help reduce the need for chemical fertilizers

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      Production of chemical fertilizers accounts for about 1.5 percent of the world’s greenhouse gas emissions. MIT chemists hope to help reduce that carbon footprint by replacing some chemical fertilizer with a more sustainable source — bacteria.

      Bacteria that can convert nitrogen gas to ammonia could not only provide nutrients that plants need, but also help regenerate soil and protect plants from pests. However, these bacteria are sensitive to heat and humidity, so it’s difficult to scale up their manufacture and ship them to farms.

      To overcome that obstacle, MIT chemical engineers have devised a metal-organic coating that protects bacterial cells from damage without impeding their growth or function. In a new study, they found that these coated bacteria improved the germination rate of a variety of seeds, including vegetables such as corn and bok choy.

      This coating could make it much easier for farmers to deploy microbes as fertilizers, says Ariel Furst, the Paul M. Cook Career Development Assistant Professor of Chemical Engineering at MIT and the senior author of the study.

      “We can protect them from the drying process, which would allow us to distribute them much more easily and with less cost because they’re a dried powder instead of in liquid,” she says. “They can also withstand heat up to 132 degrees Fahrenheit, which means that you wouldn’t have to use cold storage for these microbes.”

      Benjamin Burke ’23 and postdoc Gang Fan are the lead authors of the open-access paper, which appears in the Journal of the American Chemical Society Au. MIT undergraduate Pris Wasuwanich and Evan Moore ’23 are also authors of the study.

      Protecting microbes

      Chemical fertilizers are manufactured using an energy-intensive process known as Haber-Bosch, which uses extremely high pressures to combine nitrogen from the air with hydrogen to make ammonia.

      In addition to the significant carbon footprint of this process, another drawback to chemical fertilizers is that long-term use eventually depletes the nutrients in the soil. To help restore soil, some farmers have turned to “regenerative agriculture,” which uses a variety of strategies, including crop rotation and composting, to keep soil healthy. Nitrogen-fixing bacteria, which convert nitrogen gas to ammonia, can aid in this approach.

      Some farmers have already begun deploying these “microbial fertilizers,” growing them in large onsite fermenters before applying them to the soil. However, this is cost-prohibitive for many farmers.

      Shipping these bacteria to rural areas is not currently a viable option, because they are susceptible to heat damage. The microbes are also too delicate to survive the freeze-drying process that would make them easier to transport.

      To protect the microbes from both heat and freeze-drying, Furst decided to apply a coating called a metal-phenol network (MPN), which she has previously developed to encapsulate microbes for other uses, such as protecting therapeutic bacteria delivered to the digestive tract.

      The coatings contain two components — a metal and an organic compound called a polyphenol — that can self-assemble into a protective shell. The metals used for the coatings, including iron, manganese, aluminum, and zinc, are considered safe as food additives. Polyphenols, which are often found in plants, include molecules such as tannins and other antioxidants. The FDA classifies many of these polyphenols as GRAS (generally regarded as safe).

      “We are using these natural food-grade compounds that are known to have benefits on their own, and then they form these little suits of armor that protect the microbes,” Furst says.

      For this study, the researchers created 12 different MPNs and used them to encapsulate Pseudomonas chlororaphis, a nitrogen-fixing bacterium that also protects plants against harmful fungi and other pests. They found that all of the coatings protected the bacteria from temperatures up to 50 degrees Celsius (122 degrees Fahrenheit), and also from relative humidity up to 48 percent. The coatings also kept the microbes alive during the freeze-drying process.

      A boost for seeds

      Using microbes coated with the most effective MPN — a combination of manganese and a polyphenol called epigallocatechin gallate (EGCG) — the researchers tested their ability to help seeds germinate in a lab dish. They heated the coated microbes to 50 C before placing them in the dish, and compared them to fresh uncoated microbes and freeze-dried uncoated microbes.

      The researchers found that the coated microbes improved the seeds’ germination rate by 150 percent, compared to seeds treated with fresh, uncoated microbes. This result was consistent across several different types of seeds, including dill, corn, radishes, and bok choy.

      Furst has started a company called Seia Bio to commercialize the coated bacteria for large-scale use in regenerative agriculture. She hopes that the low cost of the manufacturing process will help make microbial fertilizers accessible to small-scale farmers who don’t have the fermenters needed to grow such microbes.

      “When we think about developing technology, we need to intentionally design it to be inexpensive and accessible, and that’s what this technology is. It would help democratize regenerative agriculture,” she says.

      The research was funded by the Army Research Office, a National Institutes of Health New Innovator Award, a National Institute for Environmental Health Sciences Core Center Grant, the CIFAR Azrieli Global Scholars Program, the MIT J-WAFS Program, the MIT Climate and Sustainability Consortium, and the MIT Deshpande Center. More

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      in Security

      Tiny magnetic beads produce an optical signal that could be used to quickly detect pathogens

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      Getting results from a blood test can take anywhere from one day to a week, depending on what a test is targeting. The same goes for tests of water pollution and food contamination. And in most cases, the wait time has to do with time-consuming steps in sample processing and analysis.

      Now, MIT engineers have identified a new optical signature in a widely used class of magnetic beads, which could be used to quickly detect contaminants in a variety of diagnostic tests. For example, the team showed the signature could be used to detect signs of the food contaminant Salmonella.

      The so-called Dynabeads are microscopic magnetic beads that can be coated with antibodies that bind to target molecules, such as a specific pathogen. Dynabeads are typically used in experiments in which they are mixed into solutions to capture molecules of interest. But from there, scientists have to take additional, time-consuming steps to confirm that the molecules are indeed present and bound to the beads.

      The MIT team found a faster way to confirm the presence of Dynabead-bound pathogens, using optics, specifically, Raman spectroscopy. This optical technique identifies specific molecules based on their “Raman signature,” or the unique way in which a molecule scatters light.

      The researchers found that Dynabeads have an unusually strong Raman signature that can be easily detected, much like a fluorescent tag. This signature, they found, can act as a “reporter.” If detected, the signal can serve as a quick confirmation, within less than one second, that a target pathogen is indeed present in a given sample. The team is currently working to develop a portable device for quickly detecting a range of bacterial pathogens, and their results will appear in an Emerging Investigators special issue of the Journal of Raman Spectroscopy.

      “This technique would be useful in a situation where a doctor is trying to narrow down the source of an infection in order to better inform antibiotic prescription, as well as for the detection of known pathogens in food and water,” says study co-author Marissa McDonald, a graduate student in the Harvard-MIT Program in Health Sciences and Technology. “Additionally, we hope this approach will eventually lead to expanded access to advanced diagnostics in resource-limited environments.”

      Study co-authors at MIT include Postdoctoral Associate Jongwan Lee; Visiting Scholar Nikiwe Mhlanga; Research Scientist Jeon Woong Kang; Tata Professor Rohit Karnik, who is also the associate director of the Abdul Latif Jameel Water and Food Systems Lab; and Assistant Professor Loza Tadesse of the Department of Mechanical Engineering.

      Oil and water

      Looking for diseased cells and pathogens in fluid samples is an exercise in patience.

      “It’s kind of a needle-in-a-haystack problem,” Tadesse says.

      The numbers present are so small that they must be grown in controlled environments to sufficient numbers, and their cultures stained, then studied under a microscope. The entire process can take several days to a week to yield a confident positive or negative result.

      Both Karnik and Tadesse’s labs have independently been developing techniques to speed up various parts of the pathogen testing process and make the process portable, using Dynabeads.

      Dynabeads are commercially available microscopic beads made from a magnetic iron core and a polymer shell that can be coated with antibodies. The surface antibodies act as hooks to bind specific target molecules. When mixed with a fluid, such as a vial of blood or water, any molecules present will glom onto the Dynabeads. Using a magnet, scientists can gently coax the beads to the bottom of a vial and filter them out of a solution. Karnik’s lab is investigating ways to then further separate the beads into those that are bound to a target molecule, and those that are not. “Still, the challenge is, how do we know that we have what we’re looking for?” Tadesse says.

      The beads themselves are not visible by eye. That’s where Tadesse’s work comes in. Her lab uses Raman spectroscopy as a way to “fingerprint” pathogens. She has found that different cell types scatter light in unique ways that can be used as a signature to identify them.

      In the team’s new work, she and her colleagues found that Dynabeads also have a unique and strong Raman signature that can act as a surprisingly clear beacon.

      “We were initially seeking to identify the signatures of bacteria, but the signature of the Dynabeads was actually very strong,” Tadesse says. “We realized this signal could be a means of reporting to you whether you have that bacteria or not.”

      Testing beacon

      As a practical demonstration, the researchers mixed Dynabeads into vials of water contaminated with Salmonella. They then magnetically isolated these beads onto microscope slides and measured the way light scattered through the fluid when exposed to laser light. Within half a second, they quickly detected the Dynabeads’ Raman signature — a confirmation that bound Dynabeads, and by inference, Salmonella, were present in the fluid.

      “This is something that can be used to rapidly give a positive or negative answer: Is there a contaminant or not?” Tadesse says. “Because even a handful of pathogens can cause clinical symptoms.”

      The team’s new technique is significantly faster than conventional methods and uses elements that could be adapted into smaller, more portable forms — a goal that the researchers are currently working toward. The approach is also highly versatile.

      “Salmonella is the proof of concept,” Tadesse says. “You could purchase Dynabeads with E.coli antibodies, and the same thing would happen: It would bind to the bacteria, and we’d be able to detect the Dynabead signature because the signal is super strong.”

      The team is particularly keen to apply the test to conditions such as sepsis, where time is of the essence, and where pathogens that trigger the condition are not rapidly detected using conventional lab tests.

      “There are a lot cases, like in sepsis, where pathogenic cells cannot always be grown on a plate,” says Lee, a member of Karnik’s lab. “In that case, our technique could rapidly detect these pathogens.”

      This research was supported, in part, by the MIT Laser Biomedical Research Center, the National Cancer Institute, and the Abdul Latif Jameel Water and Food Systems Lab at MIT. More

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      in Environment

      Harnessing synthetic biology to make sustainable alternatives to petroleum products

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      Reducing our reliance on fossil fuels is going to require a transformation in the way we make things. That’s because the hydrocarbons found in fuels like crude oil, natural gas, and coal are also in everyday items like plastics, clothing, and cosmetics.

      Now Visolis, founded by Deepak Dugar SM ’11, MBA ’13, PhD ’13, is combining synthetic biology with chemical catalysis to reinvent the way the world makes things — and reducing gigatons of greenhouse gas emissions in the process.

      The company — which uses a microbe to ferment biomass waste like wood chips and create a molecular building block called mevalonic acid — is more sustainably producing everything from car tires and cosmetics to aviation fuels by tweaking the chemical processes involved to make different byproducts.

      “We started with [the rubber component] isoprene as the main molecule we produce [from mevalonic acid], but we’ve expanded our platform with this unique combination of chemistry and biology that allows us to decarbonize multiple supply chains very rapidly and efficiently,” Dugar explains. “Imagine carbon-negative yoga pants. We can make that happen. Tires can be carbon-negative, personal care can lower its footprint — and we’re already selling into personal care. So in everything from personal care to apparel to industrial goods, our platform is enabling decarbonization of manufacturing.”

      “Carbon-negative” is a term Dugar uses a lot. Visolis has already partnered with some of the world’s largest consumers of isoprene, a precursor to rubber, and now Dugar wants to prove out the company’s process in other emissions-intensive industries.

      “Our process is carbon-negative because plants are taking CO2 from the air, and we take that plant matter and process it into something structural, like synthetic rubber, which is used for things like roofing, tires, and other applications,” Dugar explains. “Generally speaking, most of that material at the end of its life gets recycled, for example to tarmac or road, or, worst-case scenario, it ends up in a landfill, so the CO2 that was captured by the plant matter stays captured in the materials. That means our production can be carbon-negative depending on the emissions of the production process. That allows us to not only reduce climate change but start reversing it. That was an insight I had about 10 years ago at MIT.”

      Finding a path

      For his PhD, Dugar explored the economics of using microbes to make high-octane gas additives. He also took classes at the MIT Sloan School of Management on sustainability and entrepreneurship, including the particularly influential course 15.366 (Climate and Energy Ventures). The experience inspired him to start a company.

      “I wanted to work on something that could have the largest climate impact, and that was replacing petroleum,” Dugar says. “It was about replacing petroleum not just as a fuel but as a material as well. Everything from the clothes we wear to the furniture we sit on is often made using petroleum.”

      By analyzing recent advances in synthetic biology and making some calculations from first principles, Dugar decided that a microbial approach to cleaning up the production of rubber was viable. He participated in the MIT Clean Energy Prize and worked with others at MIT to prove out the idea. But it was still just an idea. After graduation, he took a consulting job at a large company, spending his nights and weekends renting lab space to continue trying to make his sustainable rubber a reality.

      After 18 months, by applying engineering concepts like design-for-scale to synthetic biology, Dugar was able to develop a microbe that met 80 percent of his criteria for making an intermediate molecule called mevalonic acid. From there, he developed a chemical catalysis process that converted mevalonic acid to isoprene, the main component of natural rubber. Visolis has since patented other chemical conversion processes that turn mevalonic acid to aviation fuel, polymers, and fabrics.

      Dugar left his consulting job in 2014 and was awarded a fellowship to work on Visolis full-time at the Lawrence Berkeley National Lab via Activate, an incubator empowering scientists to reinvent the world.

      From rubber to jet fuels

      Today, in addition to isoprene, Visolis is selling skin care products through the brand Ameva Bio, which produces mevalonic acid-based creams by recycling plant byproducts created in other processes. The company offers refillable bottles and even offsets emissions from the shipping of its products.

      “We are working throughout the supply chain,” Dugar says. “It made sense to clean up the isoprene part of the rubber supply chain rather than the entire supply chain. But we’re also producing molecules for skin that are better for you, so you can put something much more sustainable and healthier on your body instead of petrochemicals. We launched Ameva to demonstrate that brands can leverage synthetic biology to turn carbon-negative ingredients into high-performing products.”

      Visolis is also starting the process of gaining regulatory approval for its sustainable aviation fuel, which Dugar believes could have the biggest climate impact of any of the company’s products by cleaning up the production of fuels for commercial flight.

      “We’re working with leading companies to help them decarbonize aviation” Dugar says. “If you look at the lifecycle of fuel, the current petroleum-based approach is we dig out hydrocarbons from the ground and burn it, emitting CO2 into the air. In our process, we take plant matter, which affixes to CO2 and captures renewable energy in those bonds, and then we transfer that into aviation fuel plus things like synthetic rubber, yoga pants, and other things that continue to hold the carbon. So, our factories can still operate at net zero carbon emissions.”

      Visolis is already generating millions of dollars in revenue, and Dugar says his goal is to scale the company rapidly now that its platform molecule has been validated.

      “We have been scaling our technology by 10 times every two to three years and are now looking to increase deployment of our technology at the same pace, which is very exciting.” Dugar says. “If you extrapolate that, very quickly you get to massive impact. That’s our goal.” More