title: Oxidation of laccase for improved cathode biofuel cell performances.
abstract: Graphite rods were modified by substituted aryldiazonium salts allowing subsequent laccase immobilisation and direct electron transfer at the cathode. Two covalent enzyme immobilisation methods were performed with carboxy and amino substituted grafted groups, either via the formation of an amide bond or a Schiff base between the glycosidic groups of the enzyme and the amino groups on the electrode surface, respectively. Laccase adsorption efficiency was consistently compared to the covalent attachment method on the same carbon surface, showing that the latter method led to a higher immobilisation yield when the electrode surface was functionalised with carboxylic groups, as shown from both laccase activity measurement towards an organic reducing substrate, ABTS, and quantitative XPS analysis. Both analytical methods led to similar laccase surface coverage estimations. From activity measurements, when laccase was covalently immobilised on the electrode functionalised with carboxylic groups, the surface coverage was found to be 43 ± 2% whereas it was only 10 ± 3% when laccase was adsorbed. Biocatalysed dioxygen reduction current was also higher in the case of covalent immobilisation. For the first time, oxidised laccase performances were compared to unmodified laccase, showing significant improved efficiency when using oxidised laccase: the current obtained with oxidised laccase was 141 ± 37 μA cm(-2) compared to 28 ± 6 μA cm(-2) for unmodified laccase after covalent immobilisation of the enzyme on a graphite electrode functionalised with carboxylic groups.
authors.affiliation: Laboratory Charles Friedel, CNRS UMR 7223, Chimie ParisTech, 11 rue Pierre et Marie Curie, F-75231 Paris cedex 05, France. Electronic address: meihui.zheng2809@gmail.com.
authors.forename: Meihui
authors.initials: M
authors.lastname: Zheng
authors.affiliation: PSL Research University, Chimie ParisTech, Ecole Nationale Supérieure de Chimie de Paris, Unité de Technologies Chimiques et Biologiques pour la Santé, UMR 8258, INSERM 1022, 11 rue Pierre et Marie Curie, F-75231 Paris cedex 05, France. Electronic address: sophie.griveau@chimie-paristech.fr.
authors.forename: Sophie
authors.initials: S
authors.lastname: Griveau
authors.affiliation: Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain, Croix du Sud 1, Box L7.04.01, B-1348 Louvain-la-Neuve, Belgium. Electronic address: christine.dupont@uclouvain.be.
authors.forename: Christine
authors.initials: C
authors.lastname: Dupont-Gillain
authors.affiliation: Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain, Croix du Sud 1, Box L7.04.01, B-1348 Louvain-la-Neuve, Belgium. Electronic address: michel.genet@uclouvain.be.
authors.forename: Michel J
authors.initials: MJ
authors.lastname: Genet
authors.affiliation: Laboratory Charles Friedel, CNRS UMR 7223, Chimie ParisTech, 11 rue Pierre et Marie Curie, F-75231 Paris cedex 05, France; CNRS UMR 7197, Laboratoire de Réactivité de Surface, F-75005 Paris, France; Sorbonne Universités, UPMC Univ Paris 06, UMR 7197, Laboratoire de Réactivité de Surface, F-75005 Paris, France. Electronic address: claude.jolivalt@upmc.fr.
authors.forename: Claude
authors.initials: C
authors.lastname: Jolivalt
mesh_terms: D055162:Biocatalysis; D001674:Bioelectric Energy Sources; D002244:Carbon / Q000737:chemistry; D004566:Electrodes; D004579:Electron Transport; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism; D042845:Laccase / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D010100:Oxygen / Q000737:chemistry; D011487:Protein Conformation; D055454:Trametes / Q000201:enzymology
chemical_list: D004800:Enzymes, Immobilized; D002244:Carbon; D042845:Laccase; D010100:Oxygen
keywords: Biocatalytic dioxygen reduction; Biocathode; Biofuel cell; Diazonium salt; Direct electron transfer; Oxidised laccase; XPS