Electro-fermentation process design for efficient CO2 conversion into value-added products

化学工业严重依赖原油，这是一种有限和不可持续的资源，全球价格波动对全球经济产生负面影响。石油化工储量的消耗，加上全球碳排放的空前增长引发的恶劣天气事件，代表了开发环保、可持续替代能源的驱动力，并遏制了我们对化石资源的依赖。利用微生物细胞工厂的工业生物技术已经进入了一个时代，在这个时代，生物工程的科学和技术进步可以为使用可再生碳原料的可持续产品开发做出可观的贡献。利用废物和温室气体（如CO2或CH4）生产有价值的产品，从而减少碳排放，创造净零循环经济，应该成为政府可持续工业脱碳政策的前沿。这些废气有潜力成为第三代可持续和技术经济上可行的原料。C1气体消耗好氧细菌具有明显的优势比他们的厌氧对应物，如更广泛的产品谱，更高的生产力和遗传适应性。然而，H2和O2混合物的可燃性问题限制了有氧发酵中最佳的O2浓度。较低的氧气浓度意味着较高的传质要求，这是一个可行的发酵过程所必需的。这是一个已知的问题，在一个典型的工业好氧发酵和问题加剧，只有在氧气浓度有限的好氧发酵。因此，在工业气体发酵的资本成本范围内，替代工艺设计对于经济上可行的工艺至关重要。微生物电合成将电化学与生物技术相结合，利用废弃原料和可再生能源，实现资源高效利用。电生物技术力求从电能到化学品的概念，以缩小甚至消除能源和化学部门之间的差距。产电/电活性细菌（EAB），如硫还原地杆菌和希瓦氏菌是细胞外电子转移途径的天然载体，被广泛研究，然而O2敏感性和缺乏遗传工具限制了这些细菌主要用于生物修复目的。在这个项目中，我们的目标是设计和建立一个生物过程平台，该平台将能够评估生物催化剂的电发酵潜力，以生产增值化学品。该平台将用于阐明兼性厌氧CO2消耗菌铜毒杆菌CH34的外部电子转移（EET）的遗传基础。这项多学科合作研究旨在利用电化学表征和工程生物学的互补方法来阐明和验证这种细菌的EET机制。接下来将展示其在生物电发酵过程中的潜力，从二氧化碳中产生有价值的产品。阐明该细菌EET的确切机制也将为其近亲Cupriavidus necator H16的EET机制打开大门，Cupriavidus necator H16已被证明是一种有效的自养细菌，可将二氧化碳转化为高价值的产物。凭借PI（生物过程工程/开发），Co-I（合成生物学）和国际合作伙伴（可持续电化学）的独特和互补技能，通过有效的知识交流活动，包括外展活动，我们将展示该技术在当前化学工业中的整合，作为可持续工业脱碳的主要例子。

The chemical industries are heavily reliant on crude oil, a finite and unsustainable resource with global price fluctuations with negative impact on global economies. Depleting petrochemical reserves, coupled with unprecedented rise in global carbon emissions triggering severe weather events, represent the driving forces behind the development of environmentally sound, sustainable alternatives and to curb our reliance on fossil-based resources. Industrial biotechnology using microbial cell factories has entered an era where scientific and technological advances in bioengineering can contribute appreciably towards sustainable product development using renewable carbon feedstocks. Utilization of waste and greenhouse gases such as CO2 or CH4 to produce valuable products, thereby reducing carbon emissions and creating net-zero circular economies, should be at the forefront of the governments sustainable industrial decarbonization policies. These waste gases have the potential to become the third generation sustainable and techno economically feasible feedstocks. C1 gas consuming aerobic bacteria possess significant advantages over their anaerobic counterparts such as wider product spectrum, higher productivities and genetic amenability. However, the flammability concerns of H2 and O2 mixtures limit optimum O2 concentrations in aerobic gas fermentations. Lower O2 concentrations mean higher mass transfer requirements are necessary for a viable fermentation process. This is a known problem in a typical industrial aerobic fermentation and the problem is only exacerbated in aerobic gas fermentation where O2 concentration are limited. An alternative process design is therefore pivotal for an economically feasible process within the capital cost context of industrial gas fermentation.Microbial electrosynthesis combines electrochemistry and biotechnology in a resource-efficient processes by relying on waste raw materials and renewable energies. Electro-biotechnology strives for the concept of power-to-chemicals to narrow or even close the gap between the energy and the chemistry sector. Electrogenic /electroactive bacteria (EAB) such as, Geobacter sulfurreducens and Shewanella oneidensis are natural carriers of extracellular electron transfer pathways and are extensively studied, however O2 sensitivity and lack of genetic tools have limited the use of these bacteria mostly for bioremediation purposes.In this project we aim to design and set up a bioprocess platform that will enable the assessment of electro-fermentative potential of biocatalysts for the production of value-added chemicals. This platform will be used to elucidate the genetic basis of external electron transfer (EET) in Cupriavidus metallidurans CH34, a facultative anaerobic, CO2 consuming bacteria. This collaborative multidisciplinary study aims to use complimentary approaches in electrochemical characterisation and engineering biology to elucidate and validate the EET mechanism in this bacterium. This will be followed by demonstrating its potential in a bio-electro fermentation process, producing a valuable product from CO2. Elucidating the exact mechanism of EET in this bacterium will also open doors to potentially transfer this mechanism to its close relative, Cupriavidus necator H16 which is proven to be an efficient autotrophic bacterium converting CO2 to highly valuable products. With the unique and complementary skills from the PI (bioprocess enigneering/development), the Co-I (synthetic biology) and the international partners (sustainable electrochemistry), via effective knowledge exchange activities, including outreach activities, we will showcase the integration of this technology within the current chemical industries as a prime example for sustainable industrial decarbonisation.