MICROBIAL BIOSYNTHESIS IS AN ATTRACTIVE PLATFORM FOR GENERATING NUTRIENTS AND COMPLEX BIOMOLECULES (ENZYMES PHARMACEUTICALS ETC.) ON DEEP SPACE MISSIONS. CHEMOHETEROTROPHIC ORGANISMS IN PARTICULAR CAN BE ENGINEERED TO PRODUCE A VARIETY OF HIGH-VALUE MOLECULES IN USEFUL YIELDS. A FUNDAMENTAL CHALLENGE FOR UTILIZING THIS BIOTECHNOLOGY ON DEEP SPACE MISSIONS IS HOW TO SUPPLY THE ORGANISMS WITH A SUBSTRATE THAT CAN SUSTAIN THEIR GROWTH AND PRODUCTIVITY USING THE RESOURCES AVAILABLE IN A SPACECRAFT OR HABITAT. THIS PROPOSAL AIMS TO DEVELOP ELECTROLYSIS CELLS THAT CONVERT H2O AND CO2 INTO O2 AND CONCENTRATED ACETATE SOLUTIONS THAT CAN BE USED AS A FEEDSTOCK FOR MICROBIAL BIOSYNTHESIS. MULTIPLE CHEMOAUTOTROPHIC ORGANISMS EXHIBIT ROBUST GROWTH USING ACETATE AS THEIR PRINCIPAL ENERGY AND CARBON SOURCE AND CAN BE GENETICALLY ENGINEERED USING COMMONLY AVAILABLE MOLECULAR BIOLOGY TOOLS. ACETATE IS A KNOWN PRODUCT OF ELECTROCHEMICAL CO2 REDUCTION ON CU ELECTRODES BUT TO DATE IT HAS ONLY BEEN PRODUCED AS A MINOR PRODUCT AT LOW SYNTHESIS RATES. THE PROPOSED RESEARCH WILL INVESTIGATE CO2 REDUCTION AT CU-CONTAINING GAS DIFFUSION ELECTRODES (GDES) WHICH ARE DESIGNED TO DELIVER CO2 TO THE CATALYST SURFACE AT A FLUX THAT ALLOWS FOR HIGH ELECTROSYNTHESIS RATES. THE DESIGN OF THE GDE THE ARCHITECTURE OF THE ELECTROLYSIS CELLS AND THE OPERATING CONDITIONS WILL BE INVESTIGATED TO ELUCIDATE THE FACTORS THAT DETERMINE THE ELECTROLYTIC EFFICIENCY AND TO OPTIMIZE THE SYNTHESIS RATE AND SELECTIVITY OF ACETATE PRODUCTION. STUDIES WILL INCLUDE THE DEVELOPMENT OF NOVEL GDE CELL DESIGNS THAT GENERATE CONCENTRATED LIQUID-PHASE PRODUCT STREAMS DIRECTLY. THE STUDIES WILL INITIALLY BE PERFORMED USING CELLS THAT OPERATE WITH 1 CM2 GDES. SUBSEQUENTLY LARGER CELLS WILL BE DEVELOPED TO EVALUATE THE PERFORMANCE WITH 10 CM2 GDES AND DETERMINE DESIGN MODIFICATIONS NEEDED TO ACHIEVE LARGER SYNTHESIS RATES WITHOUT COMPROMISING EFFICIENCY.