The CO₂ Wrangler

Chemical biologist is developing enzymatic ways to turn the excess CO₂ in our atmosphere into useful stuff

The vast amount of carbon dioxide churning in our atmosphere and warming up the planet has many researchers chasing efficient ways to remove it from the air.

“At the moment, the only thing humans can do is dump it in the ground or the ocean. Or we can trap and sequester it,” says Tobias J. Erb, a synthetic biologist at Max Planck Institute for Terrestrial Microbiology, in Marburg, Germany. Erb has a different strategy: Use bacterial enzymes to pull CO₂ from the atmosphere and then convert it into useful carbon-based compounds, such as biofuel or polymers.

As a graduate student, Erb nailed the first step in the process by plucking the world’s fastest and most efficient CO₂-fixing enzyme from an ancient purple photosynthetic Proteobacteria called Rhodobacter sphaeroides. The enzyme, crotonyl-CoA carboxylase/reductase (CCR), is nearly 100 times as fast at pulling CO₂ out of the atmosphere as the enzyme that plants use.

Plants convert CO₂ into useful carbon-based compounds by the gigaton each year, but the enzyme responsible for this transformation, called Rubisco, is not only slow, it’s a bit fickle: About 20% of the time, it chooses to fix oxygen instead of CO₂.

Since discovering CCR, Erb has been dissecting the way the enzyme extracts CO₂ from the air to make the process more efficient. He’s also assembled an orchestra of 15 enzymes that can work in harmony with CCR to produce basic three-carbon compounds. His goal is to get this system working optimally in a test tube, export it to a bacterial or plant cell, and ramp up the variety and usefulness of products it makes.—Sarah Everts