Irina Bachmatova

Improvement of screen-printed carbon electrodes by modification with ferrocene derivative

Abstract 4-(4-Ferrocenephenyliminomethyl)phenol (FP1) was used to modify screen-printed carbon electrodes (CEs). It was shown that FP1 efficiently mediates the electron flow from pyrroloquinoline quinone (PQQ)-dependent alcohol (ADH) or glucose dehydrogenase (GDH) to the electrode surface. This CE modification increased the stability of immobilized enzymes as well. Moreover, FP1 sufficiently lowered the oxidation/reduction potential of H 2 O 2 . The FP1-modified CEs were integrated into the flow-through amperometric cell and applied for determination of H 2 O 2 , ethanol and glucose in beverages. Good correlations ( r =0.9778 and r =0.9204 for glucose and ethanol, respectively) between results obtained by these biosensors and by refractometric or hydrometric methods were observed.

An oxygen-independent ethanol sensor based on quinohemoprotein alcohol dehydrogenase covalently bound to a functionalized polypyrrole film

In the present work the characteristics of a phenazine methosulphate mediated alcohol biosensor based on a newly isolated quinohemoprotein alcohol dehydrogenase are described. The enzyme was covalently linked at a functionalized polypyrrole film which had been electrochemically deposited on the surface of a platinum-black electrode. The biosensor architecture developed was characterized with regard to sensitivity, selectivity, and long-term operational stability. Owing to the inherent properties of the new enzyme the related biosensors are oxygen-independent and exhibit improved selectivity to ethanol in contrast to alcohol biosensors based on alcohol oxidase or on cationic nicotinamide adenine dinucleotide dependent alcohol dehydrogenase.

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.

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.