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Direct Bio-electrocatalysis of O2 Reduction by Streptomyces coelicolor Laccase Orientated at Promoter-Modified Graphite Electrodes

Authors

  • Samuel Lörcher,

    1. Interdisciplinary Nanoscience Center (iNANO), Science and Technology, Aarhus University, Gustav Wieds Vej 1590–14, 8000 Aarhus C (Denmark)
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  • Dr. Paula Lopes,

    1. Interdisciplinary Nanoscience Center (iNANO), Science and Technology, Aarhus University, Gustav Wieds Vej 1590–14, 8000 Aarhus C (Denmark)
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  • Andrey Kartashov,

    1. Interdisciplinary Nanoscience Center (iNANO), Science and Technology, Aarhus University, Gustav Wieds Vej 1590–14, 8000 Aarhus C (Denmark)
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  • Prof. Elena E. Ferapontova

    Corresponding author
    1. Interdisciplinary Nanoscience Center (iNANO), Science and Technology, Aarhus University, Gustav Wieds Vej 1590–14, 8000 Aarhus C (Denmark)
    • Interdisciplinary Nanoscience Center (iNANO), Science and Technology, Aarhus University, Gustav Wieds Vej 1590–14, 8000 Aarhus C (Denmark)

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Abstract

Bacterial laccase from Streptomyces coelicolor (SLAC) has been immobilised and orientated at promoter (pyrene and neocuproine)-modified electrodes productively both for direct electron transfer (ET) between the electrode and the T1 Cu site of SLAC and direct (unmediated) bio-electrocatalysis of dioxygen reduction. Its T1 Cu potential ranges between 471 and 318 mV versus the normal hydrogen electrode, at pH 5.5 and 8, respectively; this value is dependent both on the solution pH and electrode modification. In the presence of O2, Cu of the T2/T3 trinuclear centre is distinguished electrochemically at 748–623 mV. Depending on the promoter nature, different orientations of SLAC at pyrene- and neocuproine-modified electrodes can be followed from the kinetic analysis of the ET rates. Bio-electrocatalytic reduction of oxygen starts from the T1 Cu potentials of SLAC, and is most efficient at the promoter-modified electrodes, thereby demonstrating good performance both in neutral and basic media and in solutions with a high NaCl content, such as sea water. The obtained results allow consideration of a broader bioenergetic application of laccases as biocathodes operating directly in such environmental media as sea water and physiological fluids.

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