Enzyme cascades in biofuel cells

Enzymatic biofuel cells are a class of fuel cells that utilize oxidoreductase proteins to catalyze the oxidation of fuel and/or the reduction of oxygen. Although biofuel cell cathodes typically utilize a single enzyme system, enzyme cascades are frequently necessary in biofuel cell anodes to enable deep or complete oxidation of fuels, since most oxidase and dehydrogenase enzymes only catalyze two-electron oxidation of substrates. Herein, we detail a summary of all the significant advancements made using enzyme cascades in recent years. We present examples of natural, non-natural and hybrid enzyme cascades that have been used in biofuel cells and hybrid fuel cells, and classified them either as linear, cyclic, random sequential or parallel cascades. We conclude by discussing the future directions that are necessary to the field.