Oxygen-reducing enzyme cathodes produced from SLAC, a small laccase from Streptomyces coelicolor.
The bacterially-expressed laccase, small laccase (SLAC) of Streptomyces coelicolor, was incorporated into electrodes of both direct electron transfer (DET) and mediated electron transfer (MET) designs for application in biofuel cells. Using the DET design, enzyme redox kinetics were directly observable using cyclic voltammetry, and a redox potential of 0.43 V (SHE) was observed. When mediated by an osmium redox polymer, the oxygen-reducing cathode retained maximum activity at pH 7, producing 1.5 mA/cm2 in a planar configuration at 900 rpm and 40 degrees C, thus outperforming enzyme electrodes produced using laccase from fungal Trametes versicolor (0.2 mA/cm2) under similar conditions. This improvement is directly attributable to differences in the kinetics of SLAC and fungal laccases. Maximum stability of the mediated SLAC electrode was observed at pH above the enzyme's relatively high isoelectric point, where the anionic enzyme molecules could form an electrostatic adduct with the cationic mediator. Porous composite SLAC electrodes with increased surface area produced a current density of 6.25 mA/cm2 at 0.3 V (SHE) under the above conditions.
Gallaway
Joshua
J
Columbia University, Department of Chemical Engineering, New York, NY 10027, USA.
Wheeldon
Ian
I
Rincon
Rosalba
R
Atanassov
Plamen
P
Banta
Scott
S
Barton
Scott Calabrese
SC
D001674:Bioelectric Energy Sources; D004563:Electrochemistry / Q000295:instrumentation* / Q000379:methods; D004566:Electrodes; D004574:Electromagnetic Fields; D004579:Electron Transport; D004800:Enzymes, Immobilized / Q000737:chemistry; D004867:Equipment Design; D019544:Equipment Failure Analysis; D042845:Laccase / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D048372:Streptomyces coelicolor / Q000201:enzymology*
D004800:Enzymes, Immobilized; D042845:Laccase; D010100:Oxygen