Effect of various methods of immobilization on the stability of a microbial biosensor for surfactants based onPseudomonas rathonis T

The operating and storage stability of a receptor element of an amperometric biosensor based on thePseudomonas rathonis strain T capable of degrading surfactants was tested. Microbial cells were immobilized by incorporation in gels (agar, agarose, and calcium-alginate), polyvinyl alcohol membrane, adhesion to Chromatographic paper GF/A, or by cross-linking induced by glutaric aldehyde. Incorporation of microbial cells in agar gel provides long-standing conservation of their activity and viability during measurements of high concentrations of surfactants and allows the receptor element of the biosensor to be rapidly recovered after measurements.     

Bacteria-degraders as the base of an amperometric biosensor for detection of anionic surfactants

Several strains belonging to genera Pseudomonas and Achromobacter and characterized by the ability to degrade anionic surfactants were tested as potential bases of microbial biosensors for surfactant detection. For each strain the substrate specificity and stability of sensor signals were studied. The total amount of the substrates tested (including carbohydrates, alcohols, aromatics, organic acids, etc.) was equal to 60; the maximal signals were observed towards the anionic surfactants. The lower limit of detection for sodium dodecyl sulfate used as a model surfactant was in the field of 1 microM for all the strains. The created microbial biosensor model can extend the practical possibilities for rapid evaluation of surfactants in water media.     

A new assay format for electrochemical immunosensors: polyelectrolyte-based separation on membrane carriers combined with detection of peroxidase activity by pH-sensitive field-effect transistor

A new rapid immunotechnique combining separation of reactants by filtration through a porous membrane and potentiometric detection of the bound enzyme label by a pH-sensitive field-effect transistor is proposed. The complexes to be detected are formed by the method described earlier in (Anal. Chem. 71 (1999) 3538), including a homogeneous binding of immunoreactants and a polyanion carrier (polymethacrylate) followed by heterogeneous separation on a membrane incorporating an immobilized polycation (poly-N-vinyl-4-ethylpyridinium). The proposed technique for a sensitive detection of peroxidase label is based on the measurement of pH changes in the optimised substrate solution containing o-phenylenediamine, hydrogen peroxide and ascorbic acid. The antigens studied were herbicide atrazine and hormone testosterone. Their specific detection is realised via competitive binding of free and peroxidase-labelled antigens by antibodies integrating with a (staphylococcal protein A-polyanion) conjugate. The total analysis time is 20-25 min. The range of quantitative detection is 0.2-100 ng ml(-1) for atrazine and 5-300 ng ml(-1) for testosterone. Data scatter of replicate tests varies from 3 to 10%. Application of protein A-polyanion conjugate allows to use the proposed protocol for different antigens without additional treatment of specific antisera.     

Structural modification of environment by microorganisms: formation of Liesegang rings around Dictyostelium discoideum population

The results of the experimental study of the environment modification--the emergence of Liesegang rings around a Dictyostelium discoideum population are presented. The formation of Liesegang rings induced by D. discoideum cells is observed on addition of glucose into the semi-solid nutrient medium (agar concentration 0.5-1.5%). We show that the emergence of Liesegang rings is attended with a redistribution of folic acid in the nutrient substrate. A pH decrease in the course of D. discoideum cultivation is shown to be a factor inducing the redistribution of folic acid. The mechanisms of structural modification of the D. discoideum environment are discussed.     

Effect of conditions of culturing Pseudomonas rathonis T on characteristics of a biosensor for determining anionic surface-active agents

The dependence of the sensitivity of a microbial biosensor of anionic surfactants (AS) on the growth phase of Pseudomonas rathonis T, a strain capable of degrading surfactants, was studied. Correlations were found between the optimum values of temperature and pH of microbial growth, substrate utilization, and functional performance of the microbial biosensor. These results allow the process of AS detection to be optimized.     

Bacterial Cellulose as a Matrix for Microorganisms in Bioelectrocatalytic Systems

Applied Biochemistry and Microbiology - Bacterial cellulose (BC) produced by the Komagateibacter sucrofermentas VKPM B-11267 bacteria was used as a carrier for immobilization of acetic acid...     

Degradation of <Emphasis Type="Italic">p</Emphasis>-Toluenesulfonate by Immobilized <Emphasis Type="Italic">Comamonas testosteroni</Emphasis> BS1310 (pBS1010) Cells

Parameters of degradation of p-toluenesulfonate (TS) by free and agar-embedded Comamonas testosteroni BS1310 (pBS1010) cells were determined. The maximum rate of TS degradation was 25% lower in immobilized than free cells, equaling 11 nmol min^?1 mg^?1 cells. Degradation of TS by both free and immobilized cells was associated with molecular oxygen consumption (molar ratio 1 : 2). In a plug-flow reactor, the degradation rate was 10.4 nmol min^?1 mg^?1 cells. The results can be applied to designing reactors for TS degradation in sewage and developing biosensors.     

Use of NMR spectroscopy in studies of sorbitol and glucose transformation by Gluconobacter oxydans

NMR spectroscopy was applied for studying the products of glucose and sorbitol oxidation by cells of Gluconobacter oxydans. An analysis of 1H NMR spectra showed that the transformation of glucose results in the formation of diketogluconic acid, and sorbitol is oxidized to sorbose. In the 32P NMR spectra, only a signal of inorganic phosphate was detected, which accumulated in the medium as a result of cell lysis.     

Analysis of ethanol–glucose mixtures by two microbial sensors: application of chemometrics and artificial neural networks for data processing

Although biosensors based on whole microbial cells have many advantages in terms of convenience, cost and durability, a major limitation of these sensors is often their inability to distinguish between different substrates of interest. This paper demonstrates that it is possible to use sensors entirely based upon whole microbial cells to selectively measure ethanol and glucose in mixtures. Amperometric sensors were constructed using immobilized cells of either Gluconobacter oxydans or Pichia methanolica. The bacterial cells of G. oxydans were sensitive to both substrates, while the yeast cells of P. methanolica oxidized only ethanol. Using chemometric principles of polynomial approximation, data from both of these sensors were processed to provide accurate estimates of glucose and ethanol over a concentration range of 1.0–8.0 mM (coefficients of determination, R²=0.99 for ethanol and 0.98 for glucose). When data were processed using an artificial neural network, glucose and ethanol were accurately estimated over a range of 1.0–10.0 mM (R²=0.99 for both substrates). The described methodology extends the sphere of utility for microbial sensors.