Enzyme Cascade for Catalyzing Sucrose Oxidation in a Biofuel Cell

Biofuel cells provide a safe and renewable means of powering small electronic devices. In this work, we demonstrate a bioanode that is capable of extracting four electrons from a single molecule of sucrose by way of a three-enzyme cascade. Invertase, fructose dehydrogenase and glucose oxidase are immobilized in a ferrocene-modified linear poly(ethylenimine) (LPEI) hydrogel onto the surface of a carbon electrode. Fuel sources are generated in the polymer film by (1) hydrolyzing sucrose into fructose and glucose and then (2) electroenzymatically oxidizing fructose and glucose to produce a current response. A previously unreported synergistic effect is observed between glucose oxidase and fructose dehydrogenase that results in a current response that is considerably higher than expected. The newly described enzyme cascade generated 302 ± 57 μA/cm 2 at 25 °C and 602 ± 62 μA/cm 2 at 37 °C and when poised against an air breathing platinum cathode in a biofuel cell, the multienzyme-containing film generated 42 ± 15 μW/cm 2 at 172 mV with a maximum current density of 344 ± 25 μA/cm 2 in 100 mmol/L sucrose at 25 °C. This is the first example of an enzymatic biofuel cell that utilizes both fructose and glucose as oxidation fuel sources.