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哥伦比亚大学美国正在投入大量资源成为生物基化学品的领导者。虽然乙醇一直是主要焦点，但应该指出的是，其他生物燃料和化学品，如甲醇，即使不是更有吸引力，也可能具有同样的吸引力。甲醇被广泛用作汽油混合物的添加剂，燃料电池中的电子供体，将长链脂肪酸和脂类转化为生物柴油的反式酯化剂，以及合成二甲醚（也是一种燃料）的前体。此外，甲醇仍然是废水处理中应用最广泛的加强脱氮的化学品之一。在美国，大多数甲醇是由甲烷的化学氧化产生的。化学催化途径昂贵、耗能大、冗余；包括甲烷最初氧化为二氧化碳和氢气，然后将二氧化碳还原回甲醇。在这个项目中，氨氧化细菌的代谢多样性将被设计成生物转化“脏”沼气池废气，其中含有甲烷和二氧化碳的混合物（两者都是产生甲醇的氨氧化细菌的共同底物）为甲醇。具体来说，作为该项目的一部分，将开发纯培养氨氧化生物反应器，用于将甲烷部分氧化为甲醇。氨氧化菌与甲烷甲醇氧化相关的代谢途径和营养需求将被表征。最后，利用纯培养数据，将开发代谢模型，并将其用于生物乙醇生产系统的设计和操作。该项目的成功实施有可能将废水处理厂转变为生产甲醇的生物精炼厂，并促进沼气池废气作为液体燃料源的利用。同时避免了甲烷化学转化为甲醇过程中的路径冗余。因此，该项目遵循一个潜在的转化范例，基于利用现有的，但研究较少的微生物途径，并通过工艺工程优化这些途径。在许多可能的应用中，甲醇也可以作为碳源在去除废水中的氮（硝酸盐）过程中使用。然而，好处是实现这种脱氮的碳源不是石油或化石燃料。因此，该项目也可能成为资源中性生物脱氮的强力催化剂。预计该项目将通过设计适当的生物工艺技术，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，该项目将提供一个令人兴奋的平台，通过参与纽约哈莱姆一所少数民族学校的学生以及正在进行的美国国家科学基金会STEP教师培训计划的科学教师，来改善科学教育。

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.