This article reports the electrochemical studies of bio-electrocatalytic oxygen reduction reaction catalyzed by a new laccase from a thermophilic bacterium, which exhibits superior stability and activity retention compared to fungal laccases. The electro-kinetic study of this catalytic reaction was conducted using a classic tool of electrochemistry, the rotating ring disk electrode (RRDE). Bacillus sp. FNT laccase was immobilized onto a multiwall carbon nanotube modified glassy carbon disk electrode using a molecular tethering agent, 1-pyrenebutanoic acid succinimidyl ester (PBSE). The conditions for laccase immobilization were optimized to prepare a highly active bioconjugate for the electrochemical reduction of oxygen. The kinetic parameters such as Tafel slopes, number of electrons transferred, electrochemical rate constant and the electron transfer rate were calculated from RRDE measurements. The rate constant of the four-electron transfer reaction was calculated to be 3.21 x 10(-1) +/- 8.5 x 10(-3) cm s(-1). The slope value obtained from Tafel plot was close to that of value for the ideal four-electron transfer oxygen reduction, suggesting excellent electro-catalytic activity of the FNT laccase-MWCNT conjugates. (C) 2018 The Electrochemical Society.

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