Bacillus Licheniformis CotA Laccase Mutant: ElectrocatalyticReduction of O2 from 0.6 V (SHE) at pH 8 and in Seawater

Abstract

AbstractEnzymes operating in environmental media are of immense biotechnological interest, in particular, for sustainable energy production. Here, we show that the K316 N/D500G mutant of CotA laccase from Bacillus licheniformis operates in basic media and seawater, electrocatalyzing O2 reduction from 0.59 V, pH 8. CotA mutant's T1Cu center exhibits a formal potential of 0.56 V, consistent with an onset of bioelectrocatalytic reduction of O2. A photoelectrochemical cell recycling H2O/O2 by a semiconductor photoanode and CotA mutant biocathode produced 41 and 11 μW cm2, in buffer and seawater, respectively, at pH 8, (electricity production being limited solely by the photoanode performance, reaching 240 and 220 μW cm−2 in a Zn‐biobattery design), suggesting a prospective enzyme application for clean and sustainable production of electricity from seawater and oxygen.