Carbon-Negative Platform Uses Microbes to Turn Waste Gases into Valuable Chemicals

A tiny ally produces big results for decarbonization and clean manufacturing.

Fossil fuels do more than run our vehicles and electric power plants and heat our homes. They are also the source of chemicals found in countless products we use every day, from plastics to soaps. But fossil fuels are not a renewable resource – they come from multi-million-year-old deposits of plants and animals. That’s why we need alternatives to fossil fuels. In the search for alternatives, a team of scientists from LanzaTech, Northwestern University, and Oak Ridge National Laboratory (ORNL) has developed carbon capture technology that harnesses industrial emissions to sustainably produce valuable chemicals without fossil fuels.

The carbon-negative platform uses microorganisms as tiny but powerful factories to convert carbon in gases released by agriculture, industry, and municipal waste into acetone and isopropanol (IPA). Companies use these chemicals to make thousands of products, from fuels and solvents to fabrics and clear acrylic. These chemicals are currently made using raw materials – called feedstocks – that come from fossil fuels.

“This bioprocess provides a sustainable alternative to today's production routes to these essential chemicals, which currently rely on fresh fossil feedstocks and result in significant toxic waste,” said Jennifer Holmgren, CEO of LanzaTech. "We can reduce greenhouse gases by more than 160%, achieve carbon-negative production, and lock up carbon that would have ended up in the atmosphere."

Researchers built on existing LanzaTech technology to develop an efficient new process that converts waste gases, such as emissions from heavy industry, into either acetone or IPA using an engineered bacterium called Clostridium autoethanogenum, or C. auto.

Identifying the best enzymes for acetone and IPA production and engineering microbial strains to achieve efficient, high-yielding carbon-to-chemical conversion was a complex scientific challenge. The scientists used a three-pronged approach.

First, LanzaTech screened nearly 300 strains of the bacteria for enzymes that could be useful, Next, the researchers built a combinatorial DNA library – the largest ever for this class of microbe – to find enzyme variants that optimized acetone production. Further optimization relied on cutting-edge synthetic biology tools, including cell-free prototyping by Northwestern University, advanced modeling by LanzaTech, and molecular analyses by ORNL.

The work expanded on a 2015 project in which ORNL and LanzaTech scientists sequenced the entire C. auto genome. This work provided critical data necessary to make connections between the microbe’s genes and the desired traits. As work with C. auto progressed, the researchers employed ORNL’s comprehensive systems biology approach and analytical capabilities.

The work drew in particular on two key ORNL specialties: proteomics, the study of proteins, and metabolomics, the study of small molecules called metabolites. These research areas provide a molecular-level view of which specific chemicals are being used and produced by a microbe. Like any organism, when microbes consume or metabolize the substances they need to survive, they produce byproducts. For scientists engineering microbes to produce certain substances, these byproducts represent bottlenecks.

“The protein and metabolite profiles show where a production bottleneck is occurring inside the C. auto cell,” said Tim Tschaplinski, head of ORNL’s Biodesign and Systems Biology Section. “We can see what needs to be modified next in the pathways to flow more of the carbon to the product.”

Michael Köpke, LanzaTech’s vice president for synthetic biology, said, “Oak Ridge has very unique capabilities in terms of DNA sequencing, systems biology, and various metabolomics and proteomics. The lab’s expertise helped us troubleshoot the process to find out which steps may be limiting.”

“We found one of the enzymes in particular gave a significant boost once we increased production,” Köpke said. “And we found that through a lot of systems biology and proteomics analyses that were done by Oak Ridge.”

LanzaTech is currently scaling up the technology. The process, described in the journal Nature Biotechnology, can be inserted into existing systems and deployed for use around the world, recycling carbon that would otherwise be released as greenhouse gases.

“Synthetic biology is a powerful tool to advance decarbonization and address climate change,” ORNL Associate Laboratory Director Paul Langan said. “Our scientists use the laboratory’s world-class capabilities and work with industry to harness biological systems for the production of clean fuels and chemicals in support of a robust bioeconomy.”

This article was created in partnership with Oak Ridge National Laboratory, learn more about their work.

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