Biological conversion of methane to methanol using monooxygenic pathways in autotrophic ammonia oxidizing bacteria

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Biological conversion of methane to methanol using monooxygenic pathways in autotrophic ammonia oxidizing bacteria ABSTRACTCBET 1236297Kartik ChandranColumbia UniversityThe United States is investing significant resources to become a leader in bio-based chemicals. While ethanol has been of primary focus, it should be noted that other biofuels and chemicals such as methanol can be as, if not more, attractive. Methanol is widely used as an additive in gasoline blends, as an electron donor in fuel cells, as a trans-esterfication agent to convert long-chain fatty acids and lipids to biodiesel and as a precursor to synthesize dimethyl ether (also a fuel). In addition, methanol is still one of the most widely used chemicals for enhancing denitrification in wastewater treatment. Most methanol in the States is produced by chemical oxidation of methane. The chemical catalysis pathway is expensive, energy intensive and redundant; involving initial oxidation of methane to CO2 and H2 and then reduction of CO2 back to methanol. In this project, the metabolic versatility of ammonia oxidizing bacteria will be engineered to biologically convert "dirty" digester off-gas, which contains a mixture of methane and CO2 (both co-substrates for methanol producing ammonia oxidizing bacteria) to methanol. Specifically, as part of this project, pure culture ammonia oxidizing bioreactors will be developed for the partial oxidation of methane to methanol. The metabolic pathways and nutritional requirements of ammonia oxidizing bacteria associated with methane to methanol oxidation will be characterized. Finally, using the pure culture data, metabolic models will be developed and used for the design and operation of a system for biomethanol production.The successful implementation of this project could potentially convert wastewater treatment plants into biorefineries producing methanol, and promote utilization of digester off-gas in the form of a liquid fuel-source. At the same time, pathway redundancies in chemical conversion of methane to methanol could be avoided. This project therefore follows a potentially translational paradigm based on harnessing existing, but poorly studied microbial pathways and optimizing such pathways via process engineering. Of many possible applications, the methanol produced can also be used as a carbon source during the removal of nitrogen (nitrate) from wastewater. However, the benefit is that the source of carbon to achieve this nitrogen removal is not petroleum or fossil based. Therefore, this project could also be a strong catalyst for resource neutral biological nitrogen removal. This project is expected to contribute to the overall concept of resource recovery from wastewater, landfill gas and other sources of methane by engineering appropriate bioprocess technologies. Further, this project will provide an exciting platform for improving science education by involving students from a minority school in Harlem, NY as well as science teachers who are part of an ongoing NSF STEP Teacher Training Program.