About This Project

Atmospheric methane is a GHG with 84x more warming potential than CO2. While chemical engineers struggle to capture or destroy it, methanotrophic enzymes oxidize methane at ambient temperatures and pressures. However, transferring enzymatic activity into open-air industrial systems faces many challenges. How might we build a pMMO enzymatic site that's active outside cell and outside aqueous solutions?

Ask the Scientists

Motivating Factor

Particulate methane monooxygenase (pMMO), a membrane-bound enzyme active at ambient temperature and pressure, has been an inspiration for synthetic biologists and chemical engineers fighting to reduce atmospheric CH4. However, deployments by both groups have struggled to economically tackle 2ppm concentrations.

Any scaled engineering solution requires a combination of lowering air-handling costs, increasing catalytic efficiency, and utilizing low-cost materials.

How do we integrate pMMO-like catalytic abilities into built infrastructure moving air, from coal mine ventilation systems to general HVAC systems? How can biologicals stay active without hydration, durable with fast moving air, and paired with an energy source? How might we integrate these active sites into high surface area materials like paints?

Specific Bottleneck

Enzyme engineering today assumes an aqueous environment, but for effective oxidation we have to catalyize in a gaseous context. While biologicals like spores can survive totally dry conditions, their proteins are inactive until hydrated. Our primary challenge is driving catalytic activity outside an aqueous environment with limited or no hydration.

Catalytic activity in metalloenzymes requires several components working in tandem. Following pMMO chemistry, we'll need 1) a coordinated di-copper active site, 2) hydrophobic channel for selecting CH4 and O2, 3) histidine sidechain for electron transfer to and positioning copper ions, and 4) a channel for methanol produced to vacate. Additionally, for membrane bound proteins like pMMO, we have to consider how cell membrane itself provides mechanical and electrical support for all these components to work.

These compounding challenges require new approaches for catalyst design that spans synthetic biology and physical chemistry.

Actionable Goals

Demonstrate a proof-of-principle catalyst that avoid gas-liquid diffusion rate limits by maintaining structure and activity without being in liquid.

The first goal will be forming an experimental workflow that combines methods from high throughput enzyme design, molecular dynamics modeling, and materials characterization. We need to demonstrate a sequence of computational steps that lets us work backwards from nature's aqueous active site to new open-air possibilities.

We then will produce minimal structures to validate different sub-nanometer structural goals, such as pooling H2O at specific sites, metal ion positioning, hydrophobic channeling, electrode or quantum dot integration, durability, and anchoring into supporting polymers or materials.

Upon proving fundamentals, we can combine lessons learned for CH4 oxidation starting at high ppm and working down to 2 ppm.