Patent ID: 8076035

Claim:
A fuel cell comprising: an electrode; and an enzyme solution capable of decomposing a fuel with a plurality of enzymes in three or more stepwise reactions and transferring electrons produced by the oxidation reaction to the electrode, the enzyme solution including (a) fuel decomposing enzymes including a first enzyme, a second enzyme, and a third enzyme, (b) diaphorase, which oxidizes and decomposes NADH into NAD+ and H+, and (c) a NAD+ coenzyme, wherein the conditions specified by equations (1) and (2) below are satisfied and defined as follows: 0 <U ( E 1)≦ U ( E 2)≦ U ( E 3) (1) U ( E 1)+ U ( E 2)+ U ( E 3)≦ U (DI) (2) where U(E1) denotes an enzyme activity of the first enzyme, U(E2) denotes an enzyme activity of the second enzyme, U(E3) denotes an enzyme activity of the third enzyme, and U(DI) denotes an enzyme activity of the diaphorase.