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.