Crude Fungal Culture Allows Current Flow in Biofuel Cells

In Germany, University of Freiburg scientists have used crude culture solution of enzyme-secreting fungus to trigger electrochemical reaction for allowing enzymatic biofuel cells (BFCs) to generate electricity.

Enzymatic BFC is a type of fuel cell that uses enzymes, rather than the resource-limited noble metals, as catalyst for the conversion of biochemically stored energy into electricity. The bottlenecks for enzymatic BFC are the limited electrode lifetime caused by enzyme degradation and the cost and time needed for enzyme purification.

The German group reported in the journal ChemSusChem that the supernatant from Tremetes versicolor crude culture containing laccase enzyme could extend the electrode lifetime of enzymatic BFCs significantly to as much as 120 days, and even longer lifetimes seem possible.

T. versicolor, also known as turkey tail fungus,  is a tree fungus commonly found in temperate climates. When used in a BFC, the fungus releases laccase enzyme into a solution surrounding the cathode (the positive pole of the cell) where it enables the oxygen reduction reaction to liberate the electrons into the electrode.

The experiment, conducted at the Micro Energy Harvesting at the Department of Microsystems Engineering (IMTEK) of the University of Freiburg, demonstrated that an enzymatic BFC cathode can be sustained without the need for expensive and time-consuming purification of the enzymes.