A Biosensor Based Microorganisms Immobilized in Layer-by-Layer Films for the Determination of Biochemical Oxygen Demand

A new approach has been developed for the formation of the biosensor recognition elements via the immobilization of microorganisms in layer-by-layer films in order to determine the biochemical oxygen demand (BOD). Bioreceptor elements of BOD-biosensors have been fabricated based on the bacterial microorganisms Paracoccus yeei, Pseudomonas veronii, and Bacillus proteolyticus isolated from activated sludge. The recognition element was formed with via layer-by-layer deposition; each layer contained cells of one species. A similar multilayered recognition element based on yeast cells of Ogataea angusta , Blastobotrys adeninivorans, and Debaryomyces hansenii was created . In both cases, the cells were immobilized in a hydrogel of polyvinyl alcohol modified with N -vinylpyrrolidone. It was found that layer-by-layer immobilization increases the sensitivity of both the yeast- and bacterial cell–based biosensors. It was surmised that this is due to the lack of competition for substrate within the layer and its greater ability to each of the cell layers. The effects of the composition of the assayed samples (pH, ionic strength, heavy metal compounds) on the oxidative activity of the developed recognition elements have been studied. The analytical and metrological characteristics of the biosensors have been defined. The lower limit of the estimated BOD 5 values was 0.5 mg О 2 /dm 3 and 0.7 mg О 2 /dm 3 for bacterial- and yeast cell–based biosensors, respectively. BOD 5 was detected in water samples with the fabricated recognition elements. It was shown that the use of these two bioreceptors makes it possible to obtain data that strongly agree with those obtained with traditional method and that biosensing analyzers can act as prototype pilot model of the devices