Enhancement of hydrogen production and power density in a bio-reformed formic acid fuel cell (BrFAFC) using genetically modified Enterobacter asburiae SNU-1

The objective of this research was to enhance hydrogen production and power density of a bio-reformed fuel cell (BrFAFC) in the fermentative hydrogen-producing bacterium, Enterobacter asburiae SNU-1, by genetic manipulation and treatment for cell stability. At certain formate concentrations and pHs, formate hydrogen lyase (FHL) decomposes formate to hydrogen and CO₂. FHL is expressed by the FhlA transcription activator. Consequently, over-expressing the fhlA gene will increase FHL activity. We tested hydrogen productivity in peptone-yeast extract-glucose (PYG) growth medium and in formate production medium using fhlA over-expressed E. asburiae SNU-1 and found that specific hydrogen production was enhanced by 36.89% and 56.28%, respectively. Using a 25 mM optimized concentration of MgSO₄, cell autolysis, which impedes hydrogen production in formic acid media, decreased; therefore, hydrogen production increased by 18%. A BrFAFC performance test was conducted in 300 mM formic acid containing 25 mM MgSO₄. The BrFAFC using fhlA over-expressed SNU-1 as a cell catalyst for hydrogen production showed similar fuel cell performance up to 0.6 V compared to that of a proton exchange membrane fuel cell supplying pure H₂ gas, and also generated a two-fold maximum power density than that using the SNU-1wild type.