Study of a Biocathode Based on the Physical Immobilization of Crude-Extract with Laccase Activity for Oxygen Reduction

A biocathode based on the physical absorption on carbon surfaces of crude extract with laccase activity (ExLac) obtained of C. polyzona, a Mexican endemic fungus that uses barley straw as substrate, is prepared and evaluated toward oxygen reduction reaction. The biocathode electrode consists in a mixture of ExLac with 10 mM ABTS {2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)} diammonium salt and vulcan XC-72.

Electrochemical evaluation of the biocathode consisted of cyclic voltammetry CV and linear sweep voltammetry in a standard three-electrode glass cell containing a neutral aqueous media phosphate buffer solution (pH 7.4 near to blood pH) in the absence and presence of oxygen. The biocathode working electrode is constructed as follows: an ink of ExLac-ABTS/Vulcan is prepared by dispersion in deionized water and 5% Nafion solution in a ratio of 1:56:5 in a vortex and subsequently deposited onto a PVC chip and dried at room temperature.

The results showed that the biocathode catalyzes the oxygen reduction reaction better than the platinum in a neutral media in glucose presence. Further, the electrocatalyst activity of ExLac-ABTS/C is compared with that achieved by using of a biocathode prepared with commercial laccase.

One of the advantages of this type of bioelectrode array is the utilization of barley straw as a substrate in the crude extract production which is an inexpensive material that may be a good alternative for great-scale production.