| Abstract [eng] |
The objectives of the doctoral thesis are following: (i) to design carbohydrate/oxygen enzymatic biofuel cells (EBFCs); (ii) to determine the factors limiting the performance of EBFCs; (iii) to characterise the bioelectrochemical properties of the enzymes adsorbed at conductive nanostructures and evaluate the viscoelasticity of these nanostructures. In this work 5-amino-1,10-phenanthroline (5AP) has been found to be the best redox mediator for glucose oxidase (GOx) enzyme among five studied phenanthroline derivatives with different functional groups. Later the 5AP cross-linked with GOx enzyme on a graphite rod electrode (GRE) was employed as an anode while GRE with co-immobilised horseradish peroxidase (HRP) and GOx was exploited as a cathode in order to design a glucose powered EBFC. A positively charged bi-functional thiol, N-(6-mercapto)hexylpyridinium (MHP), was exploited to electrostatically attach the cellobiose dehydrogenase (CDH) enzymes from Corynascus thermophilus (CtCDH) and Humicola insolens (HiCDH) to the gold nanoparticle (AuNP) surface. This coupling enabled a sufficient direct electron transfer between the enzymes and the AuNP-modified gold surface. Therefore, the HiCDH enzyme, showing better performance characteristics, was employed as an anodic biocatalyst in the designing of a mediatorless carbohydrate (glucose or lactose)/oxygen EBFC. The biocathode of the EBFC was based on bilirubin oxidase from Myrothecium verrucaria directly immobilised on the surface of AuNPs. When separate electrodes of the designed EBFCs were studied, it was estimated that the anodes were the limiting electrodes of the performance of both mediated and direct ET based EBFCs. The controlled assembly of mono- and multi-layer structures of AuNPs on a planar thiol/polyelectrolytes modified gold surfaces has been studied, while alternating the ionic strength of the AuNP dispersion. The viscoelastic properties of the AuNP nanostructures were assessed. Moreover, the bioelectrocatalytic characteristics of the laccase (Lc) enzyme, incorporated into those nanostructures, were estimated. Specifically, the number of the Lc molecules adsorbed on a single NP was determined, the bioelectrocatalytic at a single AuNP was evaluated, and the standard heterogeneous ET rate constant between the enzyme molecule and an AuNP was assessed. |
