Carbon dioxide has long looked more like waste than resource. A new solar reactor turns it into living bacterial biomass using sunlight, enzymes and engineered E. coli, offering an early glimpse of factories that could directly make materials from air.<\/p>\n
Plants have quietly mastered one of nature\u2019s greatest tricks for hundreds of millions of years. Using sunlight, water and carbon dioxide, they create life. Now, scientists in the United Kingdom have taken an important step toward recreating part of that process using engineered bacteria and solar-powered chemistry.<\/p>\n
Researchers led by Dr. Lin Su at Queen Mary University<\/a> of London have developed an integrated solar reactor that uses sunlight to turn carbon dioxide into living bacterial biomass. The work, published in the Journal of the American Chemical Society, combines solar technology, enzymes and engineered Escherichia coli, commonly called E. coli, inside a single liquid-filled device.<\/p>\n The system mimics key parts of photosynthesis without using plants, algae or naturally photosynthetic microbes. Instead, it relies on a carefully designed combination of chemistry and biology working together in one container.<\/p>\n Researchers say the technology could eventually help create cleaner ways to manufacture chemicals, plastics and even microbial protein while using carbon dioxide as a raw material instead of fossil fuels.<\/p>\n A graphical abstract of the study. (CREDIT: Journal of the American Chemical Society) Replacing Fossil Fuels With Sunlight<\/p>\n Modern chemical manufacturing depends heavily on oil, coal and natural gas. Factories use fossil fuels not only for energy but also as building blocks for products ranging from fertilizers to plastics.<\/p>\n Scientists worldwide have searched for cleaner alternatives. Two promising areas have emerged. One uses sunlight to power chemical reactions that convert carbon dioxide into useful molecules. The other uses engineered microbes that can be programmed to make valuable products.<\/p>\n Until now, combining those two systems into one functioning platform has remained difficult.<\/p>\n Many earlier experiments required separate reactors or complex transfer steps between chemical and biological systems. Those extra steps increase cost, reduce efficiency and make large-scale manufacturing harder.<\/p>\n The new study aimed to solve that problem by creating what researchers describe as a \u201cone-pot\u201d integrated reactor. In this setup, solar-powered chemistry and living bacteria coexist inside the same liquid environment.<\/p>\n \u201cFor a clean chemical industry<\/a> to replace the fossil-fuel one, the chemistry that captures CO\u2082 and the biology that turns it into useful products will eventually need to share the same device,\u201d the researchers explained.<\/p>\n How The Reactor Works<\/p>\n Inside the reactor, sunlight powers several linked reactions.<\/p>\n Natural and engineered photosynthesis. (CREDIT: Journal of the American Chemical Society) <\/p>\n One electrode splits water molecules, releasing oxygen. That oxygen supports the growth of bacteria inside the device. A second electrode uses an enzyme to capture carbon dioxide dissolved in the liquid and convert it into formate.<\/p>\n Formate is a simple one-carbon molecule that stores chemical energy. Scientists increasingly see it as a useful energy carrier for future low-carbon manufacturing systems.<\/p>\n The engineered E. coli<\/a> then consume the formate. Using oxygen produced by the device itself, the bacteria extract energy from formate and use carbon dioxide to build new biomass.<\/p>\n In simple terms, sunlight enters the system and living cells emerge.<\/p>\n \u201cThe value of the work is showing that the full chain, from photons to E. coli biomass in one liquid, is possible at all,\u201d the study noted.<\/p>\n Why Scientists Chose Formate and E. Coli<\/p>\n Formate plays an important role in the researchers\u2019 design. Unlike sugars, which require crops and farmland, formate can be made directly from carbon dioxide using renewable energy.<\/p>\n Scientists hope this could support a future \u201cformate bioeconomy,\u201d where carbon dioxide becomes the starting material for manufacturing instead of fossil fuels<\/a>.<\/p>\n Natural bacteria exist that can grow using formate, but many are difficult to engineer for industrial use. E. coli offered a better alternative because researchers already understand its genetics and metabolism in great detail.<\/p>\n Accelerated autotrophic growth on formate. (CREDIT: Journal of the American Chemical Society) <\/p>\n Over recent years, scientists engineered E. coli strains capable of using formate as an energy source while building biomass from carbon dioxide. However, those strains initially grew slowly.<\/p>\n To improve performance, the team carried out adaptive laboratory evolution over 168 days. They repeatedly cultured the bacteria under formate-fed conditions, allowing faster-growing cells to dominate.<\/p>\n The results were dramatic. The evolved strain reached similar growth levels in just two days instead of nearly two weeks.<\/p>\n Researchers discovered that a mutation affecting a phosphate transporter gene likely helped the bacteria conserve energy under stressful alkaline conditions<\/a>. That adaptation appeared to make growth on formate more efficient.<\/p>\n Turning Carbon Dioxide Into Fuel<\/p>\n The team next focused on producing formate efficiently.<\/p>\n They used an enzyme called formate dehydrogenase attached to a specially designed titanium dioxide electrode. Another enzyme, carbonic anhydrase, helped speed up carbon dioxide processing and stabilize local acidity levels.<\/p>\n When electricity flowed through the system, the electrode converted carbon dioxide into formate with remarkable efficiency. During 10 hours of operation, the setup produced about 650 micromoles of formate per square centimeter.<\/p>\n Bioelectrochemical formate synthesis and utilization. (CREDIT: Journal of the American Chemical Society) <\/p>\n Nearly all supplied electrons went toward formate production, giving the system a Faradaic yield close to 98%.<\/p>\n The researchers then placed the evolved E. coli strain into the formate-containing solution. Over several days, the bacteria consumed most of the formate and steadily increased in biomass.<\/p>\n This showed that electrochemically produced formate could directly support bacterial growth.<\/p>\n Powering Biology With Sunlight<\/p>\n After proving the electrical system worked, researchers replaced the external power supply with an organic solar cell.<\/p>\n The solar component generated enough voltage to drive carbon dioxide reduction while avoiding the release of toxic metal ions that could damage bacteria.<\/p>\n \u201cPreviously the problem with trying to make living biomass like bacteria in a solar powered chemical reactor<\/a>, is that the chemistry typically releases toxic metal ions that poison the bacteria,\u201d said Dr. Lin Su.<\/p>\n Under simulated sunlight, the reactor generated substantial amounts of formate. The evolved bacteria later consumed all the solar-produced formate and grew successfully.<\/p>\n This experiment confirmed that sunlight alone could power the entire chain from carbon dioxide conversion to bacterial growth.<\/p>\n Solar-driven autotrophic growth. (CREDIT: Journal of the American Chemical Society) Building a Semiartificial Leaf<\/p>\n The researchers then assembled the complete integrated system, which they describe as a semiartificial leaf.<\/p>\n The device combined an organic semiconductor<\/a> photocathode with a bismuth vanadate photoanode on a small glass platform. The photoanode split water and released oxygen. The photocathode converted carbon dioxide into formate.<\/p>\n Unlike many earlier systems, the reactor operated using a relatively simple solution compatible with both enzyme chemistry and bacterial growth.<\/p>\n The device ran for 20 hours under light exposure. During operation, it generated both formate and oxygen while supporting bacterial survival.<\/p>\n Initially, bacterial biomass dropped slightly because oxygen production remained limited. Researchers solved part of that problem by adding trace minerals and adjusting the surrounding gas atmosphere.<\/p>\n Once conditions improved, bacterial growth resumed. In dark control experiments, biomass steadily declined, confirming that light powered the system.<\/p>\n To verify where the carbon came from, scientists repeated the experiment using carbon dioxide labeled with carbon-13 isotopes. The resulting formate contained carbon-13<\/a>, confirming that the system truly converted carbon dioxide into bacterial biomass.<\/p>\n A Step Toward Solar Refineries<\/p>\n The reactor remains an early-stage proof of concept. Yields remain relatively small, and the system currently operates for hours rather than weeks. Still, researchers believe the achievement represents an important foundation.<\/p>\n \u201cOnce that integration works, a synthetic biologist can plug a different engineered E. coli strain into the same hardware to produce a different molecule,\u201d said Dr. Lin Su.<\/p>\n