Potential application of laccase from Pycnoporus sanguineus in methanol/O2 biofuel cells

• We demonstrate that changes in the enzyme source can improve the final biocathode performance.
• Biocathode prepared from crude extract of PyS lacase provides stable biomaterials with high power density
• Power density of 51.2 μW cm− 2 for the samples prepared with the crude extract were obtained.
• Entrapping ABTS in polypyrrole matrix and PAMAM is attractive material to immobilize PyS laccase.

This paper describes the preparation and characterization of biocathodes for a methanol/O2 biofuel cell using the crude extract and a purified laccase from a strain of Pycnoporus sanguineus (PyS). The biocathode assembly with mediated electron transfer was achieved by immobilizing either the enzymes in the crude extract or the purified laccase with polyamidoamine (PAMAM) dendrimers on top of a polypyrrole matrix containing entrapped 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) species as the redox mediator. Carbon nanotubes modified with anthracene moieties were used to orientate the purified laccase and allow for direct bioelectrocatalytic O2 reduction. The kinetic characterization of the biocathodes showed that samples prepared with either the crude extract or the purified laccase retained ABTS oxidation activity after the immobilization procedure. The biofuel cell tests showed that the biocathodes were able to furnish maximum power densities of 51.2 and 99.8 μW cm− 2 for the samples prepared with the crude extract and the purified enzyme, respectively. Moreover, it was observed that both biocathodes tested displayed a very similar loss in power performance as a function of storage time, reaching 60% of the initial activity after 60 days. Overall, the laccase-based biocathodes prepared either with the crude extract or with the purified enzyme are able to provide electrochemically active and stable biomaterials.

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