Project Description

Our project removes ammonia from waste water, and via two E. coli mutants, turns it into nitrous oxide.

Global demand for fixed nitrogen has increased to the point that half the human population now relies on chemical fertilizer to grow their food. While fertilizer is a requirement for modern life, runoff from overfertilized farmland can cause eutrophication. In the presence of abundant ammonia, algae overgrow and consume the much of the available oxygen in the water. This results in decreased biodiversity throughout the watershed. Within Europe, 53% of lakes are eutrophic.

Using two E. coli mutants built with genes from Nitrosomonas europaea and Pseudomonas aeruginosa, we provide a system to reverse nitrogen fixation. Our mutants consume ammonia and produce nitrous oxide, releases a sustainable source of energy when decomposed into nitrogen and oxygen. We also provide a prototype of a bioreactor that could be scaled up and deployed in the field to simultaneously clean the water and produce energy.

Details

The first mutant incorporates AMO, HAO and two cytochromes c554 and cm552 from Nitrosomonas europaea (shown in blue). AMO is a 3 subunit protein which converts ammonia to an intermediate called hydroxylamine (NH₂OH). HAO then converts the hydroxylamine to nitrite. During this conversion process, cytochrome c554 accepts an electron from HAO, and then passes this electron on to ccm552. The terminal electron acceptor in this chain is quinone. AMO and ccm552 are embedded in the cytoplasmic membrane, and all other proteins in this process are found in the periplasm.

The second mutant incorporates the Nir region from Pseudomonas aeruginosa (shown in yellow).