Engineering microbe-material electrochemical interfaces for metabolic steering and targeted succinic acid production in hybrid fermentation systems

Abstract

The transition toward a carbon-neutral and resource-efficient economy requires innovative biomanufacturing platforms capable of converting waste-derived substrates and carbon dioxide (CO₂) into value-added chemicals with high carbon and electron efficiency. Conventional microbial fermentation, while industrially mature, is fundamentally constrained by rigid intracellular redox balancing, limited control over electron distribution, thermodynamic bottlenecks, and the formation of undesired by-products. These limitations restrict yield, selectivity, and scalability, particularly for redox-intensive biochemicals. This thesis addresses these challenges through the systematic development of electro-fermentation and materialassisted bio-electrochemical systems, integrated with non-genetic and metabolic engineering, to enable controlled redox-driven bioprocessing. It establishes the conceptual and mechanistic framework of Electrofermentation 2.0, emphasizing the shift to potential-driven metabolic steering through engineered material-microbe-electrode interfaces. Initially, the role of conductive and redox-active materials was explored towards enhancing extracellular electron transfer, microbial adhesion, and biofilm stability within electro-fermentation systems. These studies demonstrated that material properties such as conductivity, surface chemistry, porosity, and catalytic functionality directly influence intracellular redox balance and metabolic flux distribution. Further, focus on electro-metabolic rerouting for selective production of organic acids, particularly succinic acid was focused as it is an important platform chemical. Electrofermentation and gas electro-fermentation strategies were shown to enhance intracellular NADH regeneration, strengthened reductive metabolic pathways, and suppressed competing by-product formation. Integration of CO₂ as a carbon source further enab