Bio-electrochemical synthesis of commodity chemicals by autotrophic acetogens utilizing CO2 for environmental remediation

Bio-electrochemical synthesis (BES) is a technique in which electro-autotrophic bacteria such as Clostridium ljungdahlii utilize electric currents as an electron source from the cathode to reduce CO₂ to extracellular, multicarbon, exquisite products through autotrophic conversion. The BES of volatile fatty acids and alcohols directly from CO₂ is a sustainable alternative for non-renewable, petroleum-based polymer production. This conversion of CO₂ implies reduction of greenhouse gas emissions. The synthesis of heptanoic acid, heptanol, hexanoic acid and hexanol, for the first time, by Clostridium ljungdahlii was a remarkable achievement of BES. In our study, these microorganisms were cultivated on the cathode of a bio-electrochemical cell at ?400 mV by a DC power supply at 37°C, pH 6.8, and was studied for both batch and continuous systems. Pre-enrichment of bio-cathode enhanced the electroactivity of cells and resulted in maximizing extracellular products in less time. The main aim of the research was to investigate the impact of low-cost substrate CO₂, and the longer cathode recovery range was due to bacterial reduction of CO₂ to multicarbon chemical commodities with electrons driven from the cathode. Reactor design was simplified for cost-effectiveness and to enhance energy efficiencies. The Columbic recovery of ethanoic acid, ethanol, ethyl butyrate, hexanoic acid, heptanoic acid and hexanol being in excess of 80% proved that BES was a remarkable technology.