A solar-powered microbial electrolysis cell with a platinum catalyst-free cathode to produce hydrogen.

This paper reports successful hydrogen evolution using a dye-sensitized solar cell (DSSC)-powered microbial electrolysis cell (MEC) without a Pt catalyst on the cathode, indicating a solution for the inherent drawbacks of conventional MECs, such as the need for an external bias and catalyst. DSSCs fabricated by assembling a ruthenium dye-loaded TiO(2) film and platinized FTO glass with an I(-)/I(3)(-) redox couple were demonstrated as an alternative bias (V(oc) = 0.65 V). Pt-loaded (0.3 mg Pt/cm(2)) electrodes with a Pt/C nanopowder showed relatively faster hydrogen production than the Pt-free electrodes, particularly at lower voltages. However, once the applied photovoltage exceeded a certain level (0.7 V), platinum did not have any additional effect on hydrogen evolution in the solar-powered MECs: hydrogen conversion efficiency was almost comparable for either the plain (71.3-77.0%) or Pt-loaded carbon felt (79.3-82.0%) at >0.7 V. In particular, the carbon nanopowder-coated electrode without Pt showed significantly enhanced performance compared to the plain electrode, which indicates efficient electrohydrogenesis, even without Pt by enhancing the surface area. As the applied photovoltage was increased, anodic methanogenesis decreased gradually, resulting in increasing hydrogen yield.

Nonpungent Capsicum fermentation by Bacillus subtilis and the addition of Rapidase.

To reduce the pungency of Capsicum without the loss of its biological activity, a Capsicum sp. was fermented by Bacillus subtilis with the addition of Rapidase enzyme. At 1 day of fermentation, the capsaicin content of the Capsicum ferment with Rapidase had sharply decreased from an initial content of 11.8 to 2.8 microg/ml. The Rapidase-fermented Capsicum had higher total flavonoid and phenolic contents than the Capsicum ferment without Rapidase. In addition, ABTS radical scavenging activity was enhanced in the Rapidase-fermented Capsicum as compared to that without Rapidase. Overall, fermentation using B. subtilis and Rapidase was an efficient method to produce a non-pungent Capsicum with antioxidant properties.

Operational parameters affecting the performannce of a mediator-less microbial fuel cell.

A mediator-less microbial fuel cell was optimized in terms of various operating conditions. Current generation was dependent on several factors such as pH, resistance, electrolyte used, and dissolved oxygen concentration in the cathode compartment. The highest current was generated at pH 7. Under the operating conditions, the resistance was the rate-determining factor at over 500 omega. With resistance lower than 500 omega, proton transfer and dissolved oxygen (DO) supply limited the cathode reaction. A high strength buffer reduced the proton limitation to some extent. The DO concentration was around 6 mg l(-1) at the DO limited condition. The fact that oxygen limitation was observed at high DO concentration is believed to be due to the poor oxygen reducing activity of the electrode used, graphite. The current showed linear relationship with the fuel added at low concentration, and the electronic charge was well correlated with substrate concentration from up to 400 mg l(-1) of COD(cr). The microbial fuel cell might be used as a biochemical oxygen demand (BOD) sensor.