Improving the performance of a biofuel cell cathode with laccase-containing culture supernatant from Pycnoporus sanguineus

• Easy to produce high redox laccase from Pycnoporus sanguineus.
• Using crude culture supernatant of Pycnoporus sanguineus in biofuel cells.
• Laccase in culture supernatant improves cathode performance under different pH values.

Laccases are multicopper oxidoreductases that can be used in biofuel cells to improve cathode performance by cathodic oxygen reduction. Here we present a laccase from the ligninolytic white-rot fungus Pycnoporus sanguineus that, in contrast to the Trametes versicolor laccase, can be produced in the absence of inducers in a standard culture medium. After 7 days of cultivation the activity of this laccase in culture supernatant reached 2.5 U/ml, which is high enough for direct application of the supernatant in biofuel cells. The highest current density of 115.0 ± 3.5 μA/cm2 at 400 mV vs. SCE was obtained at pH 5 with a buckypaper cathode with a laccase-containing culture supernatant. The enzyme also showed electrocatalytic activity at pH 6 and 7. These results not only present a new cost-efficient laccase for improving cathode performance, but also show that new laccases with different catalytic properties can be suitable for biofuel cells.