Starchy biomass-powered enzymatic biofuel cell based on amylases and glucose oxidase multi-immobilized bioanode

• Three enzymes (glucose oxidase, alpha-amylase and glucoamylase) were co-immobilized on bioanode.
• The bioanode can both saccharize and oxidize starchy biomass.
• The assembled biofuel cells operated with crude rice as a fuel, and delivered an open circuit voltage of 0.522 V and power density of up to 99.0 μW cm−2.

The present study reports the design of a novel bioanode to directly utilize starch as a fuel in an enzymatic biofuel cell. The enzymatic fuel cell is based on three enzymes (alpha-amylase, glucoamylase and glucose oxidase). The carbon paste electrode containing these three enzymes and tetrathiafulvalene can both saccharize and oxidize starchy biomass. In cyclic voltammetry, catalytic currents were successfully observed with both glucose and starchy white rice used as a substrate. Finally, a membrane-less white rice/O2 biofuel cell was assembled and the electrochemical performance was evaluated. The three enzyme based electrode was used as a bioanode and an immobilized bilirubin oxidase (derived from Myrothecium verrucaria) electrode was used as a biocathode. The biofuel cell delivered an open circuit voltage of 0.522 V and power density of up to 99.0 μW cm−2. Our results show that a readily available fuel can be used for enzymatic fuel cells, and will lead to new designs.