Tobias Erb

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

Vital Stats

Current Affiliation: Max Planck Institute for Terrestrial Microbiology, in Marburg, Germany

Age: 36

Ph.D. alma mater: Albert-Ludwigs University Freiburg

Talent: Transforming CO2 into useful carbon-based compounds, such as biofuels, using enzymes.

Scientific role model: Fritz Haber and Carl Bosch. Thanks to these scientists, Erb says, humans can industrially carry out two to three times as much nitrogen fixation as bacteria. “Having something like a Haber-Bosch process for pulling CO2 out of the atmosphere would be fabulous.”

Three Most Important Papers By Erb:

“The Use of Ene Adducts to Study and Engineer Enoyl-Thioester Reductases” (Nature Chem. Biol. 2015, DOI: 10.1038/nchembio.1794)

“Direct Evidence for a Covalent Ene Adduct Intermediate in NAD(P)H-dependent Enzymes” (Nature Chem. Biol 2014, DOI: 10.1038/nchembio.1385)

“Carboxylation Mechanism and Stereochemistry of Crotonyl-Coa Carboxylase/Reductase, a Carboxylating Enoyl-Thioester Reductase” (Proc. Natl. Acad. Sci. USA 2009, DOI: 10.1073/pnas.0903939106)

Research At A Glance

Erb wants to reduce the greenhouse gas CO2 in Earth’s atmosphere with bacterial enzymes and turn it into useful carbon-based compounds. He’s already discovered a CO2-fixing enzyme, called CCR, that can carry out the toughest step: Pull CO2 out of the air and attach it to an organic molecule, crotonyl-CoA. The long-term goal is to build more complicated, useful compounds such as fuel.

Erb wants to reduce the greenhouse gas CO2 in Earth’s atmosphere with bacterial enzymes and turn it into useful carbon-based compounds. He’s already discovered a CO2-fixing enzyme, called CCR, that can carry out the toughest step: Pull CO2 out of the air and attach it to an organic molecule, crotonyl-CoA. The long-term goal is to build more complicated, useful compounds such as fuel.
Credit: Shutterstock/C&EN

Emily Balskus
Karen Havenstrite
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