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The degradation and mineralization of the nonionic surfactant octylphenol ethoxylate (OPEO), commercially known as Triton??? X-45, by the peroxymonosulfate (PMS)/UV-C process were investigated. Three different toxicity tests (Daphnia magna, Vibrio fischeri and Pseudokirchneriella subcapitata) as well as the Yeast Estrogen Screen (YES) bioassay were undertaken to evaluate the potential toxic and estrogenic effects of OPEO and its oxidation products. OPEO removal was very fast and complete after 7 min via PMS/UV-C treatment under the investigated reaction conditions (OPEO = 20 mg L???1 (47 ??M); TOC = 12 mg L???1; PMS = 2.5 mM; initial reaction pH = 6.5; applied UV-C dose = 21 Wh L???1). TOC removal also proceeded rapidly; a gradual decrease was observed resulting in an overall TOC removal of 84%. The toxic responses of PMS/UV-C treated OPEO solutions varied according to the test organism used in the bioassay. Daphnia magna was found to be most sensitive to aqueous OPEO, whereas Pseudokirchneriella subcapitata appeared to be the least sensitive one. Daphnia magna and Vibrio fischeri tests revealed that the inhibitory effect of OPEO decreased significantly during the course of treatment. On the other hand, PMS/UV-C oxidation products exhibited a high toxic effect towards Pseudokirchneriella subcapitata (around 60%). YES test results underlined the need for improving the PMS/UV-C treatment performance to remove the estrogenic activity of OPEO and its oxidation products.

Lactose hydrolysis by β-galactosidase immobilized on two nylonmembranes, differently grafted, has been studied in a bioreactor operating under isothermal and non-isothermalconditions. One membrane (M1) was obtained by chemical grafting of methylmethacrylate (MAA); the other one (M2) by a double chemical grafting: styrene (Sty) and MAA. Hexamethylenediamine was used as a spacer between the graftedmembranes and the enzyme. Both membranes have been physically characterized studying their permeabilities in presence of pressure or temperature gradients. Under non-isothermalconditions, the increase in activity of membrane M2 was higher than that of membrane M1. The α and β coefficients, giving the percentage of activity increase when a temperature difference of 1°C is applied across the catalytic membranes, have been calculated. Results have been discussed with reference to the greater hydrophobicity of membrane M2 with respect to membrane M1, the hydrophobicity being a prerequisite for the occurrence of the process of thermodialysis.

The growing body of experimental evidence on nonisothermal matter transport in artificial porous membranes until now has been alternatively interpreted within the frame of reference of one of three independent theoretical approaches. According to one, the force driving transport is due to transfer of momentum from thermal excitations to the medium; another assumes this force to be due to transported entropy balance; the third envisages distillation in vapor-filled pores as the particular transport mechanism occurring in hydrophobic membranes

The behaviour of the enzyme invertase, located on the cell wall of baker's-yeast cells and entrapped in a gelatin membrane, was studied under isothermal and non-isothermal conditions. The reaction rate linearly increased with the applied transmembrane temperature gradient, with reference either to the average temperature or to the temperature on the warm side of the catalytic membrane. These results were obtained both when the bioreactor was operated under conditions of closed volumes and when the substrate-containing solutions are recirculated. The mathematical relationships have been elaborated between the temperatures read in the working solutions and those on the two faces of the catalytic membrane. Since the temperature difference across the membrane is smaller than that indicated by the thermocouples, the observed effects are greater than expected. The potential advantages of the use of a non-isothermal bioreactor in processes of industrial interest are discussed.

Heat, flowing through material systems composed of condensed phases produces thermal radiation forces, giving thus rise to various effects, some of them probably relevant to biological membrane transport. We shall use a simple physical argument to prove that the heat flux Jq couples with momentum flux Jp, generating pressure in liquid and liquid-solid interfaces. A theorem due to Boltzmann, applied by Ehrenfest to the adiabatic case1, shall be our starting point.

In NaCl and KCl aqueous nonisothermal solutions K+ inverts its sense of migration within the physiological concentration range; Na+ behaves similarly at much lower concentrations. These findings are discussed in relation to solute-induced modifications of water structure and of their influence on thermal diffusion. A possible evolutionary model of a thermodiffusive mechanism for the sodium-potassium pump is also suggested.

Nonisothermal membrane transport has been experimentally studied in the system sodium chloride and potassium chloride aqueous solutions/AP-20 Millipore porous partition. Anomalous behavior is found in both solvent and solute fluxes. The concentration dependence of these fluxes exhibits sharp minima and maxima, respectively. The anomalous regions occur in concentration ranges strongly influenced by the nature of the cation and by (average) temperature. When these results are compiled with the ones relative to thermal diffusion in the same solutions, stringent proof of the close affinity of processes of heat-flux-mediated matter transport in homogeneous and nonhomogeneous (membrane) systems is obtained. The physical cause of the observed anomalies can be tentatively imputed to solute-solvent interactions and to their dependence on solute nature and concentration and on solution temperature. © 1982 American Chemical Society.

A monolithic silica gel matrix with entrapped glucose oxidase (GOD) was constructed as a bioactive element in an optical biosensor for glucose determination. Intrinsic fluorescence of free and immobilised GOD was investigated in the visible range in presence of different glucose concentrations by time-resolved spectroscopy with time-correlated single-photon counting detector. A three-exponential model was used for analysing the fluorescence transients. Fractional intensities and mean lifetime were shown to be sensitive to the enzymatic reaction and were used for obtaining calibration curve for glucose concentration determination. The sensing system proposed achieved high resolution (up to 0.17 mM) glucose determination with a detection range from 0.4 mM to 5 mM.

Micro-Attenuated Total Reflection (ATR) Fourier Transform Infrared spectroscopy was used to investigate sol–gel layers for biosensing applications prior and after glucose oxidase (GOD) immobilization. The changes occurring in sol–gel infrared spectrum after GOD immobilization were clearly evidenced confirming the retaining of the enzyme activity. Moreover, micro-ATR experimental technique allowed us to investigate the spatial distribution of enzyme concentration. The non-destructive nature of our approach also enabled to monitor the time stability of sol–gel layers and of embedded GOD. The temporal evolution of some peaks in infrared spectra of these sol–gel layers was compared with absorption and steady-state fluorescence measurements. The results reported here confirm that micro-ATR infrared spectroscopy can be usefully employed for a non- or minimally invasive detailed characterization of supports for enzyme immobilization.

In view of the heath problems induced by the presence into the environment of endocrine disruptors, laccase from Trametes versicolor was covalently immobilized on a chemically modified polypropylene membrane in order to remove phenol and its derivatives from polluted waters. Using phenol as substrate model the optimal immobilization conditions were determined. The immobilized laccase exhibited maximal enzyme activity at pH 5.5 and optimal temperature at 55 °C. These operative parameters have been compared with those obtained with the soluble laccase in order to ascertain the immobilization effect. When employed in a bioreactor operating under isothermal conditions the immobilized laccase was able to oxidize a wide range of phenolic substrates. In particular it was found that some phenol derivatives (2-CP, 3-CP, 4-CP, NP and chlorophene) were oxidized at a similar rate than phenol, other derivatives (paracetamol, 3-MP and chloroxyphenol) at a smaller rate, while others (2,4-DCP and BPA) at higher rate. When the catalytic membrane was employed in a non-isothermal reactor the reaction rate increased with the increase of the applied temperature difference. Practically the increase of the laccase oxidative power under the non-isothermal conditions followed the same sequence observed under isothermal conditions. Interesting enough, the percentage increase of enzyme reaction rate under non-isothermal conditions resulted higher in the cases in which the isothermal reaction rate was smaller. When the reduction of the production times by the presence of a temperature gradient is considered, the measured values strongly candidate the technology of non-isothermal bioreactors as a useful tool in processes of detoxification of waste waters polluted by endocrine disruptors of phenolic origin. © 2010 Elsevier B.V. All rights reserved.

A monolithic silica gel matrix with entrapped glucose oxidase was constructed as a bioactive element in an optical biosensor for glucose determination. Physicochemical and biochemical characterizations of the catalytic matrix were performed, and the intrinsic fluorescence of immobilised glucose oxidase (GOD) was investigated in the UV and visible range by performing steady state and time course measurements. In all cases, the silica gel matrix proved to be a suitable support for optical biosensing owing to its superior optical properties (e.g., high transmittance and reliable fluorescence and GOD absorption spectra after immobilisation). From steady state measurements, calibration curves were obtained as a function of glucose concentration. When time course measurements were performed, the silica gel support displayed a larger linear calibration range and higher sensitivity than other immobilisation systems. In addition, a glucose optical biosensor was developed and characterised using as catalytic element GOD immobilised on a gel disk bound to a bundle of optical fibres.

A novel packed-bed bioreactor, operating under isothermal and non-isothermal conditions, has been constructed. The core of the apparatus consisted in a polypropylene ring filled with beta-galactosidase immobilized on beads of polyacrylic acid, grafted with dimethylaminoethyl methacrylate. Phenylendiamine and glutaraldehyde were used as spacer and coupling agent, respectively. Two lateral nylon membranes held the enzyme beads into the ring and allowed the occurrence of the process of thermodialysis when the bioreactor was operating under non-isothermal conditions. Comparison of the enzyme activity under isothermal and non-isothermal conditions has shown that in the presence of temperature gradients the rate of lactose hydrolysis was increased, with a reduction of the apparent Km value. Under non-isothermal conditions the percentage increases of enzyme activity were found to decrease with the increase of the substrate concentration. The results have been explained within the frame of reference of the process of thermodialysis.

A hydrophobic and catalytic membrane has been obtained by grafting with γ -radiations a Teflon membrane in presence of methylmethacrylate solution and by immobilizing on it, after treatment with glutaraldehyde, the β-Galactosidase enzyme. When employed in a non-isothermal bioreactor, the membrane showed an increase in catalytic activity proportional to the applied temperature gradients. The results have been explained in terms of distinct contributions from the process of thermodialysis and the conformational changes induced in the dynamic structure of the enzyme by the presence of heat flow. The increase of the yield of the process has been evaluated in terms of a coefficient α representing the percent increase of enzyme activity when a temperature difference of 1°C is applied across the membrane. The catalytic Teflon membrane used here gave values of 20%, which are comparable to those obtained with other membrane systems, making this kind of membrane useful for practical applications in industrial processes.

The investigation of materials suitable for enzyme immobilization in biosensing applications has a widespread interest. There are many studies on physico-chemical properties of these materials at macroscopic level but few studies have been devoted to examine and correlate these properties at microscopic level. FT-IR spectroscopy with Micro-Attenuated Total Reflection (Micro-ATR) approach can be extremely useful for understanding a variety of aspects of materials which can be used for optimising immobilization procedures. Moreover, this experimental approach is particularly simple to use (no sample preparation is required) and minimally invasive. Using a Perkin Elmer Spectrum One FT-IR spectrometer equipped with a mercury-cadmium-telluride detector and a micro-ATR element we investigated different materials used for immobilization procedures with various enzymes widely used for biosensing in environmental and clinical applications. In particular, composite membranes constituted by a chemically modified poly-acrylonitrile (PAN) membrane plus layers of tethered chitosan of different molecular weight have been examined. Also silica gel matrices without and with glucose oxidase have been investigated. Spectra have been analysed and the contribution of principal functional groups has been evidenced.

The diffusion of peritoneal dialysis (PD) at home is somewhat restricted by the difficulty of transport and storage of a large amount of dialytic solutions. This problem is exacerbated in the case of hemodialysis. With the aim of producing pure water to be used in preparing the solution for peritoneal dialysis, or for hemodialysis in general, as one example, we purified the spent dialysate solution from PD. Experiments were carried out with 24 dialysate solutions taken from 8 patients. Pure water was obtained by means of a thermodialysis process in a hollow fiber reactor operating under nonisothermal conditions. Results show that the yield of the nonisothermal process is dependent on the temperature difference applied across the hydrophobic membranes. The production of pure water per square meter of membrane and per hour was equal to 0.55 or 1.2 or 2.0 liters, with a temperature difference of 11 degrees C or 21 degrees C or 28 degrees C, respectively. These results encourage the use of the thermodialysis process in the production of pure water for clinical uses.

In view of the treatment of agricultural waste waters, urea polluted, a catalytic and hydrophobic membrane was constructed by immobilizing urease on a nylon sheet grafted with cyclohexyl methacrylate (CHMA). Hexamethylenediamine (HMDA) and glutaraldehyde (GA) were used as spacer and crosslinking agent, respectively. With reference to the soluble counterpart immobilized urease was found to exhibit (i) a shift of the optimum pH towards more acidic values; (ii) a shift of the optimum temperature towards higher temperatures; (iii) higher values of Km. The latter result indicated an apparent loss of affinity of immobilized urease towards urea. To recovery this affinity loss, the catalytic membranes were employed in a bioreactor operating under non-isothermal conditions. Under these conditions the catalytic membranes exhibited reaction rates higher and apparent Km smaller than those measured under comparable isothermal conditions. As a consequence, percentage increases of enzyme activity and reduction of the production times, proportional to the magnitude of the applied temperature difference were observed. Results have been discussed in the frame of reference of the process of thermodialysis. The technology of the non-isothermal bioreactors confirmed its usefulness also in the reduction of urea concentration in aqueous solutions.

Glucose oxidase (GOD) was immobilized on nylon membranes having three different pore diameters and chemically grafted with glycidyl methacrylate (GMA) or butyl methacrylate (BMA). Hexamethylenediamine (HMDA) and glutaraldehyde (GA) were used as spacer and coupling agent, respectively. The biochemical and electrochemical behaviour of the membranes has been studied as a function of pH, temperature and glucose concentration with reference to the grafted monomer and the membrane pore diameter. The behaviour of the soluble GOD has also been studied in order to see the modification induced by the immobilization process on the enzyme activity. It was found that the values of the biosensor sensitivity, maximum saturation current and electrochemical affinity increase with the membrane pore diameter, indipendently of the nature of the graft monomer. Opposite behaviour was found relatively to the extension of the linear response ranges and the average response times. With reference to the parameters increasing with the pore diameter it was found that membranes grafted with GMA had higher values than those of the membranes grafted with BMA. The contrary occurred to the values of the parameters decreasing with the increase of the pore diameter. Biochemical and electrochemical results have been discussed in terms of the different limitations to the diffusion of substrate and reaction products across the catalytic membrane introduced by the different pore diameters and by the different hydrophobicity of the graft monomers.

Experiments on mass transport across non-isothermal porous partitions are reported. Solvent and solute fluxes are separately assessed, and simple methods for their evaluation from experimental data are given.The interesting conclusion is reached that often the observed fluxes move against chemical potential and hydrostatic pressure gradients.