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

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.