초록
<P><B>Abstract</B></P> <P>Electrofuels processes are potentially promising platforms for biochemical production from CO<SUB>2</SUB> using renewable energy. When coupled to solar panels, this approach could avoid the inefficiencies of photosynthesis and there is no competition with food agriculture. In addition, these systems could potentially be used to store intermittent or stranded electricity generated from other renewable sources. Here we develop reactor configurations for continuous electrofuels processes to convert electricity and CO<SUB>2</SUB> to isobutyric acid (IBA) using genetically modified (GM) chemolithoautotrophic <I>Acidithiobacillus ferrooxidans</I>. These cells oxidize ferrous iron which can be electrochemically reduced. During two weeks of cultivation on ferrous iron, stable cell growth and continuous IBA production from CO<SUB>2</SUB> were achieved in a process where media was circulated between electrochemical and biochemical rectors. An alternative process with an additional electrochemical cell for accelerated ferrous production was developed, and this system achieved an almost three-fold increase in steady state cell densities, and an almost 4-fold increase in the ferrous iron oxidation rate. Combined, this led to an almost 8-fold increase in the steady state volumetric productivity of IBA up to 0.063±0.012mg/L/h, without a decline in energy efficiency from previous work. Continued development of reactor configurations which can increase the delivery of energy to the genetically modified cells will be required to increase product titers and volumetric productivities.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Demonstration of a continuous electrofuels process to convert CO<SUB>2</SUB> to isobutyric acid. </LI> <LI> New reactor design led to a three-fold increase in steady state cell densities. </LI> <LI> Volumetric productivity of isobutyric acid was increased almost eight-fold. </LI> <LI> Engineered chemolithoautotrophs could be used for efficient electrofuel production. </LI> </UL> </P>