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

在自养氨氧化细菌中利用单氧途径将甲烷生物转化为甲醇美国正在投入大量资源，以成为生物化学领域的领先者。虽然乙醇一直是主要的关注点，但应该指出的是，其他生物燃料和化学品，如甲醇，即使不是更具吸引力，也同样具有吸引力。甲醇被广泛用作混合汽油中的添加剂、燃料电池中的电子给体、将长链脂肪酸和脂肪转化为生物柴油的转酯剂，以及合成二甲醚(也是一种燃料)的前体。此外，甲醇仍然是污水处理中应用最广泛的强化反硝化的化学品之一。美国的大部分甲醇是由甲烷的化学氧化产生的。化学催化途径是昂贵的、能源密集的和多余的；包括甲烷的初始氧化为二氧化碳和氢气，然后二氧化碳还原为甲醇。在这个项目中，氨氧化细菌的代谢多功能性将被改造成生物地将含有甲烷和二氧化碳(两者都是产生氨氧化细菌的甲醇的共底物)的“肮脏”消化器尾气转化为甲醇。具体地说，作为该项目的一部分，将开发用于甲烷部分氧化为甲醇的纯培养氨氧化生物反应器。将描述与甲烷氧化成甲醇有关的氨氧化细菌的代谢途径和营养需求。最后，利用纯培养数据，开发代谢模型并用于生物甲醇生产系统的设计和运行。该项目的成功实施可能会将废水处理厂转变为生产甲醇的生物精炼厂，并以液体燃料的形式促进消化池废气的利用。同时，可以避免甲烷化学转化为甲醇过程中的路径冗余。因此，该项目遵循潜在的转换范式，基于利用现有的但研究较少的微生物途径，并通过过程工程优化这些途径。在许多可能的应用中，在去除废水中的氮(硝酸盐)的过程中，产生的甲醇也可以用作碳源。然而，好处是实现这种脱氮的碳来源不是石油或化石。因此，该项目也可能成为资源中性生物脱氮的有力催化剂。该项目预计将通过设计适当的生物处理技术，促进从废水、垃圾填埋气和其他甲烷来源中回收资源的总体概念。此外，该项目将为改善科学教育提供一个令人兴奋的平台，让纽约州哈莱姆区一所少数民族学校的学生以及参加正在进行的NSF STEP教师培训计划的科学教师参与进来。

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.