Liucija Marcinkevičienė

Oxygen electroreduction catalysed by laccase wired to gold nanoparticles via the trinuclear copper cluster

Specific wiring of biocatalysts par excellence, viz. redox enzymes, to an electrode can be exploited in the fabrication of high-performance bioelectronic devices. Here we report oxygen electroreduction catalysed by Didymocrea sp. J6 laccase wired to gold nanoparticles via the trinuclear copper cluster. Bypassing the intramolecular electron transfer, which under certain conditions is the rate-limiting step of oxygen bioelectroreduction, has resulted in the fabrication of a high current density biocathode based on high-redox-potential laccase, which is able to operate in electrolytes with a broad pH range in the presence of high fluoride concentrations.

Application of oxygen-independent biosensor for testing yeast fermentation capacity.

The pyrroloquinoline quinone (PQQ)-dependent soluble glucose dehydrogenase based carbon paste electrodes were investigated and applied for glucose monitoring in the oxygen deficient media. Reagentless biosensors possessing a wide linear range (up to 5 mM glucose with a detection limit of 0.12 mM) were designed. The oxygen-insensitive response of the biosensor creates the opportunity to use it as a flow-through device for continuous monitoring of glucose in media during the wine yeast fermentation process. The analysis of glucose assimilation rate by yeast strains using the developed biosensor correlated well (R2=0.9938) with convenient yeast testing methods.

Bioanode with alcohol dehydrogenase undergoing a direct electron transfer on functionalized gold nanoparticles for an application in biofuel cells for glycerol conversion

In this paper we designed and investigated bioanode with alcohol dehydrogenase (ADH) catalysing oxidation of glycerol and glyceraldehyde. The most effective bioanode was fabricated when ADH was immobilized on gold nanoparticles (AuNPs) modified with 4-aminothiophenol. This electrode catalysed the oxidation of both glycerol and glyceraldehyde thus demonstrating a consecutive two-step process. The bioanode generated the current density of 510µAcm-2 at pH 7.0 and 0V vs. SCE. It was demonstrated that the electrode acted effectively due to the direct electron exchange between heme of ADH and modified AuNPs. The reversible oxidation and reduction of ADH heme proceeded at around -0.05V vs. SCE. The turnover number of the immobilized enzyme was estimated to be 65s-1 which is the same as the catalytic number of the enzyme in solution. To the best of our knowledge those parameters are the highest currently reported for the alcohol dehydrogenase bioanodes operating utilizing a direct electron transfer. As a proof of biofuels cell conception, the bioanode was combined with AuNPs-laccase biocathode. The biofuel cell generated maximum power output of 130µWcm-2 at 0.5V and pH 7.0.

Laccase-catalyzed bisphenol A oxidation in the presence of 10-propyl sulfonic acid phenoxazine

The kinetics of the Coriolopsis byrsina laccase-catalyzed bisphenol A (BisA) oxidation was investigated in the absence and presence of electron-transfer mediator 3-phenoxazin-10-yl-propane-1-sulfonic acid (PPSA) at pH5.5 and 25°C. It was shown that oxidation rate of the hardly degrading compound BisA increased in the presence of the highly reactive substrate PPSA. The increase of reaction rate depends on PPSA and BisA concentrations as well on their ratio, e.g., at 0.2 mmol/L of BisA and 2 μmol/L of PPSA the rate increased 2 times. The kinetic data were analyzed using a scheme of synergistic laccase-catalyzed BisA oxidation. The calculated constant, characterizing reactivity of PPSA with laccase, is almost 1000 times higher than the constant, characterizing reactivity of BisA with laccase. This means that mediator-assisted BisA oxidation rate can be 1000 times higher in comparison to non-mediator reaction if compounds concentration is equal but very low.

Wiring Gold Nanoparticles and Redox Enzymes: A Self-Sufficient Nanocatalyst for the Direct Oxidation of Carbohydrates with Molecular Oxygen

The development of artificial nanocatalysts, especially those incorporating the highly active biocatalysts (enzymes) present in nature, is a rapidly developing field in nanocatalysis and nanomaterials science. Dehydrogenases are exceptionally attractive, as they catalyze the oxidation of various cheap/common substrates to more expensive and desired products. However, their use in sustainable catalysis and/or their incorporation in advanced nanomaterials with catalytic functions are limited owing to one immense problem that can be formulated as a question: how can the electrons received from the oxidized substrate be removed? Here, a solution to this problem is demonstrated: we designed a unique nanomaterial composed of two redox enzymes (nonspecific glucose dehydrogenase and oxygen‐reducing laccase) and gold nanoparticles. Both enzymes were wired through the gold nanoparticles (10 nm) and direct electrochemical “communication” was achieved, allowing electron transfer from the redox center of glucose dehydrogenase to a copper center of laccase. As a result, self‐sufficient nanocatalysts were synthesized and shown to oxidize various carbohydrates directly with molecular oxygen.