PNNL

The Science                                  

Researchers see an opportunity to replace synthetically-produced ammonia with a natural process using diazotrophic microorganisms. In this study, researchers developed a screening pipeline to identify a new microbial community that could act as a biocatalyst. Identifying and understanding the biological function of microbes enables researchers to model desirable phenomes of systems and, eventually, use them for other purposes. For example, researchers observed that Yarrowia lipolytica, which is broadly used for the production of oleo-chemicals, was enriched when co-cultured with Azotobacter vinelandii—a diazotrophic bacterium that captures nitrogen from air and secretes ammonium. This synergistic association naturally provides the ammonia necessary to produce fuels and other bioproducts.

The Impact

Bioconversion processes require nitrogen for growth and production of intracellular enzymes to produce biofuels and bioproducts. Typically, this is supplied as reduced nitrogen in the form of ammonia, which is produced offsite from N₂ and H₂ via the Haber-Bosch process. While this has revolutionized industries that are dependent on fixed nitrogen (e.g., modern agriculture), it is highly energy-intensive and the reliance on natural gas combustion results in substantial global carbon dioxide emissions. As a strategy to reduce greenhouse gas impacts on aerobic bioconversion processes, researchers demonstrated that a pairing of specific microorganisms could enable in situ biological nitrogen fixation from N₂ gas, thus supporting a cleaner bioprocess for production of fuels and chemicals. This project is part of Pacific Northwest National Laboratory’s Predictive Phenomics Initiative which is studying the molecular function of biological systems, such as microbial communities to model and recreate the systems’ phenotypes to aid biomanufacturing and health industries.

Summary

Researchers developed an efficient method to screen fungal bioconversion hosts for compatibility with the free-living diazotrophic bacterium Azotobacter vinelandii under nitrogen fixing conditions. Screening revealed that the genus Yarrowia is particularly enriched during co-culture experiments. Follow-up experiments identified four Y. lipolyticastrains that are capable of growth in co-culture with A. vinelandii. These strains utilize ammonium secreted during diazotrophic fixation of N₂, demonstrating the feasibly of in situ biological nitrogen fixation to support decarbonization of industrial processes that produce fuels and chemicals. 

PNNL Contacts

Kyle Pomraning, kyle.pomraning@pnnl.gov, PNNL

Pavlo Bohutskyi, pavlo.bohutskyi@pnnl.gov, PNNL

Funding

The research described in this paper is part of the Predictive Phenomics Initiative at Pacific Northwest National Laboratory and conducted under the Laboratory Directed Research and Development Program. PNNL is a multiprogram national laboratory operated by Battelle for the Department of Energy under contract no. DE-AC05-76RL01830.