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An amperometric biosensor for assessing the biochemical oxygen demand (BOD) was formed by immobilizing Debaryomyces hansenii VKM Y-2482 yeast cells in poly(vinyl alcohol) modified by N-vinylpyrrolidone. Modification provided for a high sensitivity and stability of the bioreceptor. A high oxidative activity of the receptor element and the absence of any toxic effect of assayed compounds were shown for 34 substrates (alcohols, carbohydrates, carboxylic acids, amino acids, nitrophenols and surfactants) that may occur in wastewaters. Estimates of the measurement range and region of the linear dependence of signals on the BOD level, pH and temperature sensitivities, dependences of signals on concentrations of salts, stability, Michaelis kinetic constants and assay rates were obtained. The BOD values determined by the biosensor in assayed wastewater samples were shown to have a high correlation with those obtained by the standard dilution method.

The dependence of EMF, current and voltage at a fixed load, and the fuel cell inner resistance on anolyte composition has been studied using microbial fuel cell (MFC) model. Strain Gluconobacter oxydans subsp. industrius VKM B-1280 was a biocatalyst; glucose was used as a fuel. The following anolyte compositions were considered: (1) water-soluble mediator 2,6-dichlorophenol indophenol (DCPIP) in combination with suspension and immobilized bacteria and (2) hydrophobic mediators ferrocene and 1,1'-dimethylferrocene in combination with immobilized bacteria. It was shown that DCPIP in combination with immobilized bacteria versus the cell suspension increases the generated EMF for 36%, current for 25%, power for 56%, and inner resistance for 14%. Ferrocene seems to be more preferable as compared with 1,1'-dimethylferrocene. Ferrocene gives higher values of the generated EMF (for 8%) and current (for 47%), as well as decreases the inner resistance of MFC for 38%. The proposed system can be used for rapid qualitative and quantitative assessment of the "fuel-cell-mediator-electrode" interaction under charge transfer and is used in the search of effective anolyte compositions.