Microbial electrosynthesis of biochemicals : innovations on biocatalysts, electrodes and ion-exchange for CO2 supply, chemicals production and separation

Microbial electrosynthesis (MES) is an electricity-driven production of chemicals from low-value waste using microorganisms as biocatalysts. MES from CO2 comprises conversion of CO2 to multi-carbon compounds employing microbes at the cathode which use electricity as an energy source. This thesis presents innovations on MES from CO2 using anaerobic mixed-cultures, circumventing the methane generation. Acetate was the primary product but other products including ethanol, butyrate were also produced. Establishment of active biocathode at the graphite felt cathode was achieved under long-term operation which led to the acetate accumulation up to 7-10 g L-1 at -1 V/Ag/AgCl cathode potential. CO2 reduction in MES requires continuous availability of CO2 and low cathode potential to ensure the supply of reducing equivalents/hydrogen. Use of gas diffusion biocathode doubled the CO2 mass-transfer rate which enhanced the production rates, reaching. Furthermore, a sustainable technology for manufacturing biochemicals/biofuels was demonstrated in this thesis by integrating the product separation in MES. The electricity-driven production of chemicals/biofuels from CO2/waste products and subsequent product recovery studies prospect an integration of microbial electrosynthesis with biorefineries for the up-scaling of both technologies.