Constriction of H2 biofuel cell voltammeter based on Escherichia coli microbial cells.

Abstract

Hydrogen (H2) is the lightest and most abundant chemical element in the universe, with potential to replace fossil fuels as a carbon-free source of energy. Sensitive and faster H2 gas sensors are/will be required in many industries and hydrogen-based infrastructures. Microbial hydrogenases (Hyds) reversibly catalyze the formation and oxidation of H2. Isolation and characterization of O2-tolerant [NiFe]-Hyds have stimulated new concepts in hydrogen biofuel cells (BFCs). Platinum-independent H2-driven bio-electrochemical devices are suitable for environmentally friendly energy generation and application in biosensors. Escherichia coli employs four [NiFe]-Hyds, which can be applied as anode biocatalysts in BFCs. In this study, the H2 BFC voltammeter working with graphite based strips (sensors) were constructed and the efficiency of applying the E. coli BW25113 whole cells or crude extracts as anode biocatalysts were evaluated. E. coli BW25113 was grown under fermentation of 0.2% glucose or 1% glycerol in a peptone medium, pH 7.5. Upon glucose fermentation, H2-oxidizing Hyd activity of E. coli whole cells was 1.03±0.01 U (mg CDW)−1 and 1.39±0.01 U (mg CDW)−1 was observed in cell extracts. During glycerol fermentation, Hyd activity reached up to 2.15±0.02 U (mg CDW)−1 and 3.58±0.02 U (mg CDW)−1, respectively in whole cells and cell extracts. 3 μL volumes of bacterial whole cells or cell extracts were immobilized on the sensors with the aid of 3 mM KCl and 0.8% bacteriological agar support. Whole immobilized cells(grown on glucose) produced an electrical potential of 0.650±0.05 V, and with the cell extracts, the electrical potential was slightly lower. Meanwhile, under glycerol fermentation, the electrical potential was 0.550±0.05 V in cell extracts and whole cells. Despite, the highest electrical potential was achieved with bacterial whole cells grown on glucose, H2-oxidizing Hyd activity was stimulated upon bacterial glycerol fermentation.