Kartik Chandran Columbia University
The 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.
The 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 also equally if not even 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 (DME, 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, we employed the metabolic versatility of ammonia oxidizing bacteria (AOB) to biologically convert ‘dirty’ digester off-gas, which contains a mixture of methane and CO2 (both co-substrates for methanol producing AOB) to methanol. The successful more widespread implementation of this project is intended to potentially convert wastewater treatment plants into biorefineries producing methanol, and promote utilization of digester off-gas in the form of a liquid fuel-source. To further render the results of this project widely applicable, we focused on using nitrifying bacteria, which had been grown using bacteria present in real field-scale wastewater treatment systems. Based on our studies, we were able to achieve some of the highest rates and yields of methane to methanol conversion ever reported in literature. We were able to achieve these high rates and yields by externally supplying hydroxylamine, which acts as an electron source. Hydroxylamine is also an intermediate in ammonia oxidation and is produced by ammonia oxidzing bacteria under alternating oxic and anoxic conditions. However, external addition of hydroxylamine would not be ideal from a financial perspective. Therefore, in a further improvement to our previous work, we have also now recently demonstrated methane to methanol production by ammonia oxidizing bacteria, even just using ammonia as the electron donor. The principal Intellectual Merit of this project has been to translate the fundamental microbial potential for partially oxidizing methane in ‘dirty digester gas’ to biomethanol into viable operational bioreactors. The main Broader Impact of this work has been to contribute to the overall concept of ‘resource recovery’ from wastewater, sewage, landfill gas and other sources of methane by engineering appropriate bioprocess technologies. Additional Broader Impacts of this work have included developing educational modules to introduce environmental microbiology research to high-school students in New York City and training high-school science teachers in environmental microbiology at Columbia University. This project has combined principles related to biochemical reactor engineering design, mathematical modeling and environmental microbiology. This project also supported the summer research of one female undergraduate student (summer 2013) through a research experience for undergraduates (REU) supplement.
