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PubMed1981

Immobilization of Escherichia coli Cells Containing Aspartase Activity with Polyurethane and Its Application for l-Aspartic Acid Production.

Whole cells of Escherichia coli containing aspartase activity were immobilized by mixing a cell suspension with a liquid isocyanate-capped polyurethane prepolymer (Hypol). The immobilized cell preparation was used to convert ammonium fumarate to l-aspartic acid. Properties of the immobilized E. coli cells containing aspartase were investigated with a batch reactor. A 1.67-fold increase in the l-aspartic acid production rate was observed at 37 degrees C as compared to 25 degrees C operating temperature. The pH optimum was broad, ranging from 8.5 to 9.2. Increasing the concentration of ammonium fumarate to 1.5 M from 1.0 M negatively affected the reaction rate. l-Aspartic acid was produced at an average rate of 2.18 x 10 mol/min per g (wet weight) of immobilized E. coli cells with a 37 degrees C substrate solution consisting of 1.0 M ammonium fumarate with 1 mM Mg (pH 9.0).

Journal Article↗
PubMed1984

Immobilization by Polyurethane of Pseudomonas dacunhae Cells Containing l-Aspartate beta-Decarboxylase Activity and Application to l-Alanine Production.

Whole cells of Pseudomonas dacunhae containing l-aspartate beta-decarboxylase activity were immobilized by mixing a cell suspension with a liquid isocyanate-capped polyurethane prepolymer (Hypol; W. R. Grace & Co., Lexington, Mass.). The immobilized cell preparation was used to convert l-aspartic acid to l-alanine. Properties of the immobilized P. dacunhae cells containing aspartate beta-decarboxylase activity were investigated with batch reactors. Retention of enzyme activity was observed to be as much as 100% when cell lysis was allowed to occur before immobilization. The pH and temperature optima were determined to be 5.5 and 45 degrees C, respectively. Immobilized P. dacunhael-aspartate beta-decarboxylase activity was stabilized by the addition of 0.1 mM pyridoxal-5-phosphate and 0.1 mM alpha-ketoglutaric acid to a 1.7 M ammonium aspartate (pH 5.5) substrate solution. Under conditions of semicontinuous use in a batch reactor, a 2.5% loss in immobilized l-aspartate beta-decarboxylase activity was observed over a 31-day period.

Journal Article↗
PubMed1988

Biotransformation of Dehydroabietic, Abietic, and Isopimaric Acids by Mortierella isabellina Immobilized in Polyurethane Foam.

Polyurethane foam supports immobilization of Mortierella isabellina ATCC 38063, a zygomycete that hydroxylates and thereby detoxifies resin acids found in certain pulp mill effluents. The fungus becomes entrapped as it threads growing mycelia through the open foam matrix. The tenacity of binding and the amount of biomass bound depend on initial spore numbers and nutrient concentration. Optimal dehydroabietic acid transformation occurs with early-stationary-phase foam-bound mycelia suspended in buffer at pH 6.5 to 8.5 with aeration >0.1 liter liter min and near a temperature maximum of 33 degrees C. Neither a greater number of similarly loaded foam cubes nor a greater surface area for similar amounts of biomass increased transformation rates. Compared to free mycelial cultures, foam presence retards growth and decreases the rate of precursor transformation but does not alter the nature of the metabolites formed from dehydroabietic acid, abietic acid, or isopimaric acid. Diffusional barriers or binding of substrates in an inaccessible manner may cause the observed inhibitions. Overall, foam immobilization stabilizes enzymic activity and is a facile laboratory process with scaleup potential.

Journal Article↗
PubMed1998

Purification and Properties of a Polyester Polyurethane-Degrading Enzyme from Comamonas acidovorans TB-35.

A polyester polyurethane (PUR)-degrading enzyme, PUR esterase, derived from Comamonas acidovorans TB-35, a bacterium that utilizes polyester PUR as the sole carbon source, was purified until it showed a single band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). This enzyme was bound to the cell surface and was extracted by addition of 0.2% N,N-bis(3-d-gluconamidopropyl)deoxycholamide (deoxy-BIGCHAP). The results of gel filtration and SDS-PAGE showed that the PUR esterase was a monomer with a molecular mass of about 62,000 Da. This enzyme, which is a kind of esterase, degraded solid polyester PUR, with diethylene glycol and adipic acid released as the degradation products. The optimum pH for this enzyme was 6.5, and the optimum temperature was 45 degrees C. PUR degradation by the PUR esterase was strongly inhibited by the addition of 0.04% deoxy-BIGCHAP. On the other hand, deoxy-BIGCHAP did not inhibit the activity when p-nitrophenyl acetate, a water-soluble compound, was used as a substrate. These observations indicated that this enzyme degrades PUR in a two-step reaction: hydrophobic adsorption to the PUR surface and hydrolysis of the ester bond of PUR.

Journal Article↗
PubMed2003

Albumin and fibrinogen adsorption on cibacron blue F3G-A immobilised onto PU-PHEMA (polyurethane-poly(hydroxyethylmethacrylate)) surfaces.

In the present work, it is intended to study the effect of Cibacron blue F3G-A (CB) immobilised onto PU-PHEMA (polyurethane-poly(hydroxyethylmethacrylate)) surfaces on protein adsorption and bacterial adhesion. CB immobilisation was carried out by covalent binding between its triazine ring and the hydroxyl groups of the polymer. Characterisation of the films was carried out by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FT-IR), contact angle measurements. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). CB efficiency was evaluated using radiolabelled albumin and fibrinogen from pure solutions, mixtures of both and plasma. Bacterial adhesion tests before and after albumin pre-coating were also performed. The presence of CB increases albumin and fibrinogen adsorption to PU-PHEMA surfaces. The incorporation of CB onto the PU-PHEMA surface also increases bacterial adhesion. Although albumin pre-coating decreases bacterial adhesion onto PU (67% decrease) and PU-PHEMA-CB (80%), bacterial adhesion is always lower on PU and PU-PHEMA surfaces than on PU-PHEMA-CB. These results demonstrate that, in contrast to what has been described for CB bound to dextran, CB immobilisation on PU-PHEMA surfaces presents low selectivity to albumin and increased bacterial adhesion relatively to PU and PU-PHEMA surfaces.

Adsorption↗
PubMed2001

In situ regeneration of rice (Oryza sativa L.) callus immobilized in polyurethane foam.

An in situ regeneration system for rice calli comprised of a callus growth stage and two regeneration stages was developed. After the first stage of regeneration, the medium is changed and the calli are immobilized in polyurethane foam supports, in each of which 3-5 regenerated plantlets develop from the immobilized calli during the second stage. While no significant change in callus size was observed during the first stage of regeneration, in the second stage callus enlargement and shoot regeneration predominated. In the light of these findings, calli were immobilized in the second stage after medium exchange. The use of 10-mm support cubes with an average pore size of 3.6 mm resulted in the most efficient immobilization and in situ regeneration. Medium exchange after 15 d gave the largest number of support cubes with shoots. When rice calli were cultivated in support cubes placed in 60 ml second-stage medium in a 500-ml flask, the immobilization ratio was 83%, and 82% of the support cubes contained 3-5 regenerated plantlets after 25 d. The shoot lengths of the regenerated plantlets obtained from the in situ regeneration culture were longer than those from a suspension culture. When support cubes with 3-5 regenerated plantlets were transferred from the flask to 1 4 MS solid medium supplemented with 10 g/l sorbitol and 5 g/l sucrose, the regenerated plantlets developed quickly into plants with a length above 10 cm after 10 d.

Journal Article↗
PubMed2001

Treatment of volatile organic compounds from polyurethane and epoxy manufacture by a trickle-bed air biofilter.

The objective of this study was to evaluate the performance of a trickle-bed air biofilter (TBAB) for the removal of volatile organic compound (VOC) produced during polyurethane (PU) and epoxy manufacture. The major VOCs emitted are ethyl acetate (EA) for PU and EA and xylene for epoxy production. For the treatment of VOCs emitted during PU production, the employed coal carbon appears to be efficient as a VOC concentration buffer in the biofiltration of waste gases. Based on the results of EA and total hydrocarbon (THC) removal, it was concluded that the TBAB is suitable for controlling VOC emission during PU manufacture. For the treatment of VOCs emitted during epoxy production, it was found that the performance of the TBAB is relatively poor due to the lack of VOC sources. However, this problem could be easily solved by mixing the VOCs emitted during PU and epoxy manufacture.

Journal Article↗
PubMed1999

Dermal transfer of chlorpyrifos residues from residential surfaces: comparison of hand press, hand drag, wipe, and polyurethane foam roller measurements after broadcast and aerosol pesticide applications.

Indoor residential pesticide applications present the potential for human exposures, particularly for small children. Personal contact with target and nontarget surfaces can result in transfer of pesticides to the skin, but the magnitude of such transfer is uncertain. This research compared surface sampling techniques [wipe and polyurethane foam (PUF) roller] with the removal ability of human skin following broadcast and total aerosol release applications of Dursban (Dow Elanco, Midland, MI), a residential formulation containing the insecticide chlorpyrifos. Hands were washed immediately after surface contact, following a protocol that included a laboratory-generated adjustment factor to account for incomplete removal of chlorpyrifos from skin. Chlorpyrifos transfer was similar for hand press and hand drag techniques, averaging approximately 1-6 ng/cm2 of carpet contacted. These amounts represented < 1% of the amount of chlorpyrifos deposited on the surfaces 3.5 hr earlier. Chlorpyrifos transfer from carpet to skin was 23-24 times lower than for wipe sampling and 33-36 times lower than for PUF roller sampling (p = 0.0007 and p = 0.0006 for broadcast and aerosol applications, respectively). Hand press sampling removed approximately 4.5 times less chlorpyrifos from nontarget furniture surfaces (12 ng/cm2) than did wipe sampling (56 ng/cm2; p = 0.009). Chlorpyrifos residues on carpet were substantially higher after broadcast applications than after aerosol applications, but residues on such nontarget surfaces as furniture were substantially higher for the aerosol application. This study indicates that human skin removes substantially less residue from carpets and furniture than either conventional wipe or PUF roller sampling methods following residential pest control applications of chlorpyrifos. Although this paper focuses on quantifying residue transfer from surface to skin using different surface sampling techniques, no attempt is made to quantify the amount of chlorpyrifos residue that is subsequently absorbed.

Aerosols↗
PubMed2004

Fourier transform infrared studies on deblocking and crosslinking mechanisms of some fluorine containing monocomponent polyurethanes.

The thermal reactivity of a set of different blocked perfluoropolyether (PFPE) containing polyisocyanates and one monocomponent polyurethane containing a PFPE diol was investigated by Fourier transform infrared (FT-IR) spectroscopy. With the former series of products the deblocking kinetics at 90 degrees C and 120 degrees C were investigated with time-dependent spectral data, showing the highest thermal deblocking activity for 3,5 dimethylpyrazole blocking agent. The crosslinking reaction of the PFPE diol with ketoxime blocked isocyanurate at 150 degrees C was monitored by infrared (IR) spectroscopy and two-dimensional (2D) correlation analysis; the results suggested a prevailing direct condensation mechanism and the formation of urea byproducts in the later stages of reaction. Both synchronous and asynchronous spectra were considered and discussed, pointing out the time relation of the chemical functions during the crosslinking experiment.

Journal Article↗
PubMed2003

A new selective chromogenic reagent for the spectrophotometric determination of thallium(I) and (III) and its separation using flotation and the solid-phase extraction on polyurethane foam.

A new sensitive chromogenic reagent, 9,10-phenanthaquinone monoethylthiosemicarbazone (PET), has been synthesized and used in the spectrophotometric determination of Tl(III). In HNO3, H2SO4 or H3PO4 acids, PET can react immediately at room temperature with Tl(III) to form a red 2:1 complex with a maximum absorption at 516 nm. The different analytical parameters affecting the extraction and determination processes have been examined. The calibration curve was found to be linear over the range 0.2-10 microg cm(-3) with a molar absorptivity of 2.2 x 10(4) dm3 mol(-1) cm(-1). Sandell's sensitivity was found to be 0.0093 microg cm(-2). No interference from macroamounts of foreign ions was detected, except for Pd(II). However, Pd(II) does not affect the determination process, because its complex with PET has its lambda(max) at 625 nm. The proposed method has been applied to the determination of Tl(I and III) in synthetic and natural samples after separation by flotation (in oleic acid/kerosene) and solid-phase extraction (on polyurethane foam) techniques. The two methods were found to be accurate and not subject to random error, but solid-phase extraction was preferred because it is cheap, simpler and there is no contamination risk coming from flotation reagents.

Journal Article↗
PubMed2004

A sensitive method for cadmium determination using an on-line polyurethane foam preconcentration system and thermospray flame furnace atomic absorption spectrometry.

A new sensitive and low cost method for cadmium determination at microg l(-1) levels that combines an on-line preconcentration system with the thermospray flame furnace atomic absorption spectrometry technique (TS-FF-AAS) is described in this work. Cadmium is preconcentrated from an acidic medium (pH 2.0) by forming a complex with ammonium O,O-diethyldithiophosphate (DDTP), which is then adsorbed onto polyurethane foam (PUF). The elution step is performed by using 80% (v/v) ethanol. The effects of the chemical and flow variables associated with the preconcentration were studied, such as the pH of formation of the Cd-DDTP complex, the DDTP concentration, the preconcentration and elution flow rate and the mass of adsorbent. The present method was operated in volume-mode (2 ml) and provided a linear range from 0.4 to 15.0 microg l(-1) with a sample throughput of 16 h(-1). The increase of power detection related to TS-FF-AAS by coupling the preconcentration system was confirmed by the enhancement of sensitivity (ca. 5 times), when compared to the value for TS-FF-AAS alone, thus achieving a low detection limit (0.12 microg l(-1)). The accuracy of the method was confirmed from analyses of spiked water samples and by the use of a reference technique (ETAAS). Certified biological materials were also used for the same purpose.

Journal Article↗
PubMed2005

Simultaneous determination of food dyes by first derivative spectrophotometry with sorption onto polyurethane foam.

A simple spectrophotometric method is described for resolving binary mixtures of some food dyes: Amaranth, Brilliant Blue, Sunset Yellow and Tartrazine, using the first-derivative spectra with measurements at zero-crossing wavelengths. Analytical curves are linear up to 20 mg L(-1). Standard deviations of 1.30, 2.22, 1.93 and 0.81% were obtained for synthetic binary mixtures of 2 mg L(-1) of Amaranth, Brilliant Blue, Sunset Yellow and Tartrazine, respectively. Before the spectrophotometric measurements, the dyes were sorbed onto polyurethane foam and recovered in sodium dodecyl benzene sulfonate solution. Therefore, matrix complexity was eliminated and simple spectra were obtained. The method was very satisfactorily used for determining the colorants in synthetic mixtures, with recoveries in the 96 - 101% range. Detection limit values were dependent on the colorant combination investigated. Commercial products containing binary combinations of these dyes in different ratios (from 1:1 to 1:8) were analyzed. The results were compared with those obtained by HPLC; very similar values were found by the two methods.

Journal Article↗
PubMed2005

Selective extraction of calcium on tri-n-butyl phosphate plasticized selective extraction of calcium on tri-n-butyl phosphate plasticized polyurethane foam for its spectrophotometric determination in glass and ceramics.

The present paper describes the application of a solid phase extraction system in order to separate traces of calcium from glass and ceramics for its spectrophotometric determination. The method is based on the extraction of calcium from sodium hydroxide solution by tri-n-butyl phosphate (TBP) loaded polyurethane foam (PUF), followed by its elution in hydrochloric acid. The spectrophotometric measurement of the absorbance of calcium complex with calconcarboxylic acid (2-hydroxy-1-(2-hydroxy-4-sulfo-1-naphthylazo)-3-naphthoic acid) takes place at pH 12. The following parameters were studied: effects of sodium hydroxide concentration and temperature on the extraction of calcium, time of equilibration for quantitative calcium extraction, effect of TBP concentration, effect of hydrochloric acid concentration for quantitative elution of calcium from PUF, effect of pH and concentration of calconcarboxylic acid for quantitative formation of the complex with calcium, effect of acetone on the stability of calcium-calconcarboxylic acid complex and influence of diverse ions on calcium sorption by TBP-loaded PUF. The results show that calcium traces can be separated onto TBP-loaded PUF from 0.25 mol L(-1) NaOH at 30 +/- 5 degrees C within 30 min. PUF was loaded with TBP in CCl4 (40% v/v). Elution of calcium was done in 1.0 mol l(-1) HCl. The calcium formed a complex with calconcarboxylic acid at pH 12 and absorbance was measured at 560 nm in acetone-water medium. Molar absorptivity was found to be 1.082 x 10(4) l mol(-1) cm(-1). The method obeys Beer's law from 0.10 to 5.0 microg ml(-1) Ca. The validity of the method was established by its successful application in NIST standard reference materials. The method proposed was applied to determine calcium in glass and ceramic materials. The results of the proposed method are comparable with the results of ICP-AES analysis and they are found to be in good agreement.

Journal Article↗
PubMed1988

Dust emission during cutting of polyurethane-impregnated bandages.

The airborne dust generated when cutting splinting bandages represents a potential respiratory hazard, particularly to those who regularly remove casts with a power saw. Plaster of Paris (POP) dust is already classified by the Health and Safety Executive as a nuisance dust. This paper reports on a study to determine the nature, size and concentration of dust produced when cutting polyurethane (PU) impregnated bandages using a power saw. It has been shown that, under severe conditions PU bandages produce lower airborne dust concentrations than POP bandage but that all of the bandages tested produced particles small enough to reach the final divisions of the lung. It is therefore recommended that a dust extraction unit be used when cutting all types of bandage.

Air Pollutants, Occupational↗
PubMed2002

Polyurethane and sulfonated polysulfone blend ultrafiltration membranes. I. Preparation and characterization studies.

Polyurethane (ether type) and sulfonated polysulfone (sodium salt form) in the presence of polyethylene glycol 600 were blended in various compositions using N,N'-dimethylformamide as solvent and used for preparing ultrafiltration membranes by the phase inversion technique. Polymer blend composition, additive concentration, and casting and gelation conditions were optimized. Blend membranes were subjected to ultrafiltration characterizations such as compaction, pure water flux, water content, and membrane resistance. The membranes were also subjected to the determination of pore statistics and molecular weight cutoff determination studies using dextran of different molecular weights. Surface morphology of the membranes was analyzed using scanning electron microscopy at different magnifications. The effects of polymer composition and additive concentration on the above parameters were analyzed and the results are compared and discussed with those of pure sulfonated polysulfone membranes. The derived pore size, porosity, and number of pores have a remarkable interrelationship and also have a definite role and relationship with the molecular weight cutoff, morphology, and flux performance of the membranes.

Journal Article↗
PubMed2004

[The interaction between La and polyurethane system].

A series of polyether polyurethane (PU)-LaCl3 composites with different lanthanum contents were prepared. DSC results indicate that LaCl3 promotes phase transition behavior of the LaCl3/PU composites, which causes the endothermic peak at 11.58 degrees C to disappear. FTIR spectroscopy demonstrates that significant variation can be observed. The peak at 1633 cm(-1) attributed to carbonyl vibration and the peak at 3311 cm(-1) attributed to N-H stretching band moves to 1647 cm(-1) and 3355 cm(-1), respectively, when LaCl3 is introduced into the PU system. A new band (-200 cm(-1)) assigned to the La-O band was observed, and the far IR result provided a direct evidence of the coordination between La3+ ion and C=O group of PU system.

English Abstract↗
PubMed2000

Decolorization of heat-treatment liquor of waste sludge by a bioreactor using polyurethane foam-immobilized white rot fungus equipped with an ultramembrane filtration unit.

A bench-scale bioreactor using immobilized fungal cells equipped with an ultramembrane filtration unit was developed as a means of decolorizing brown color components (melanoidins) arising from the heat-treatment liquor (HTL) of waste sludge. Artificial HTL containing 4200 color units of synthetic melanoidin supplemented with 1000 mg/l ethanol was first subjected to decolorization by the fungus Coriolus hirsutus IFO4917 immobilized onto polyurethane foam cubes. Then, the resultant biologically treated HTL was subjected to ultrafiltration to obtain the permeate (filtrate) as the effluent. The retentate (concentrate) of the filtration unit, containing the remaining melanoidin of high molecular weight and extracellular decolorizing enzymes, was returned to the fungal bioreactor to allow further decolorization. This system was operated in a sequencing batch mode under nonsterile conditions. Contamination of the bioreactor with air/water-born microbes markedly lowered the decolorization efficiency. However, this problem was solved by heating the returned concentrate at 50 degrees C for 10 min. Under the almost stable condition of a hydraulic retention time of 2 d in a 1-d cycle sequencing batch mode, about 70% decolorization was routinely achieved using the entire system (bioreactor + ultrafiltration), while the contribution of the fungal bioreactor alone to the decolorization was about 45%.

Journal Article↗