Polysulphone Membranes Research Articles

Polymorphonuclear leukocyte rigidity is defective in patients with chronic renal failure.

The purpose of the study was to investigate the rigidity of polymorphonuclear leukocytes (PMNs) in non-dialysed chronic renal failure (CRF) and haemodialysis (HD) patients. PMN rigidity as well as tumour necrosis factor alpha (TNF-alpha) and interleukin 1beta (IL-1beta) plasma levels were assessed in 10 early-stage CRF, 10 late-stage non-HD, and 10 HD patients, before and during dialysis. In HD patients both cellulose acetate and polysulphone membranes were used. Ten healthy subjects served as controls. Rigidity was tested by counting the deformability in morphologically passive PMNs by the micropipette method. Cytokine levels were measured by enzyme-linked immunosorbent assay. PMN rigidity was significantly increased in end-stage CRF patients regardless of HD but not in early-stage CRF. In HD patients PMN rigidity increased significantly 60 min after initiation of HD. There was an increase of TNF-alpha and IL-1beta levels in end-stage non-HD and HD patients and a further increase at 60 min after initiation of HD. The percentage of morphologically activated PMNs was increased only during dialysis. The nature of the HD membrane had no influence on rigidity, PMN activation, or cytokine production. The results indicate that PMN rigidity is defective in end-stage chronic CRF patients and is further increased 60 min after initiation of HD, regardless of the nature of the HD membrane used. PMN activation, increased TNF-alpha and IL-1beta levels, or a direct PMN impairment may cause the observed cell rigidity.

Lysozyme separation by hollow-fibre ultrafiltration

This paper discusses the purification of lysozyme from chicken egg white using hollow-fibre ultrafiltration (30 kDa MWCO, polysulphone membrane). Lysozyme is preferentially transmitted through the membrane while the membrane largely retains other egg white proteins. Improvement in system hydrodynamics resulted in an increase in permeate flux while lysozyme transmission remained unaffected, leading to higher productivity. The percentage purity of lysozyme obtained was generally insensitive to system hydrodynamics. The permeate flux and productivity increased with increase in transmembrane pressure (TMP) before levelling off around 0.7 bar. However, the TMP did not have any pronounced effect on the transmission and the purity of lysozyme. Experiments carried out in the diafiltration mode showed that moderately pure lysozyme (80–90%) could be obtained in an extended operation.

Ultrafiltration of sugarcane juice with spiral wound modules: on-site pilot trials

This work investigates the performance of spiral wound membrane modules for the ultrafiltration (UF) of sugarcane juice. In on-site trials carried out in an Indian sugar mill, different modules with varying channel sizes employing 20 kDa polyethersulphone and polysulphone membranes were evaluated. Two juice streams viz. raw juice and clarified juice were selected in the sugar manufacturing process and the effect of such operating parameters as transmembrane pressure, operating time and feed temperature on the permeate flux and quality were examined. It was observed that a narrow channel size resulted in a higher flux with a corresponding lower membrane fouling. The flux could be further improved by increasing the operating temperature. With both the feed streams, the permeate was observed to be consistently superior in terms of higher clarity, lower color and reduced calcium oxide content as compared to the clarified juice produced by the conventional double sulphitation process.

An experimental analysis of membrane bioreactor performances with immobilized chymosin

Aim of the present work is the experimental analysis of a continuos flow membrane bioreactor with immobilized chymosin for the hydrolysis of milk k-casein, one of the steps in the cheese production process. Chymosin has been immobilized on the bioreactor membrane by ultrafiltering under pressure its solutions, continuously fed to the system in a total recycle configuration. Bioreactor performances are evaluated in terms of two different parameters: chymosin activity and its release. The former, indirectly, measures the amount of k-casein converted into reaction products ( para-k-casein and GlycoMacroPeptide, GMP); the latter quantifies the amount of biocatalyst that is removed from the membrane by the milk flowing stream. A theoretical approach, based on the boundary layer theory, has also been attempted to estimate the dependence of chymosin release upon the wall shear stress and on the back-diffusion phenomena towards the milk bulk. The experimental analysis of bioreactor behavior has been carried out, searching for the operating conditions and system configurations that maximized chymosin activity and minimized its release. Particular attention has been devoted to the selection of the membrane material: PolySulphone membranes offered the best performance during experiments, as compared to those of PolyPropilene and PolyVinilDeneFluoride. The system configuration that gave best results, both in terms of enzyme activity and of its release, was based on a continuous milk recycle to the bioreactor. Enzyme losses were confined to 5–10 mg/l range, whereas its activity always attained values high enough (>2 g/l) to promote the coagulation in the next heating step of destabilized milk. During the experiments, an optimal value of the recycle ratio, was also found.

Membrane bioreactors for use in small wastewater treatment plants: membrane materials and effluent quality

The relative efficiencies of three membrane materials for use in a submerged membrane bioreactor treating domestic wastewater were evaluated. A glass-filled hydrophobic polypropylene membrane allowed no flow through the membrane. A polysulphone membrane (PS, 0.4 mm pore size) did not achieve a steady-state flux although a flux of 7 l m−2h−1 occurred on the last day of the steady-state run. A melt-blown polypropylene membrane (NWPP, 5 μm pore size) gave a steady-state flux of 5 l m−2h−1. Membrane productivity was low due to irreversible fouling in the NWPP membrane and reversible fouling in the PS membrane. It was found that the PP membrane gave a 5-log reduction in total coliforms whereas the PS membrane gave a 9-log reduction. CBOD5, COD, SS, NH3-N and turbidity removal was similar with both the PS and the NWPP membranes. It was concluded that although the NWPP membrane was relatively inexpensive and achieved a high degree of organic matter removal, due to its inability to remove bacteria from the effluent it would be inappropriate to apply it to domestic wastewater in a submerged MBR.

Estimation of endoglucanase and lysozyme effective diffusion coefficients in polysulphone membranes

A diffusion cell and a polysulphone membrane were used for the estimation of the effective diffusion coefficient ( D M) of endoglucanase and lysozyme. D M was calculated from the slope obtained by fitting the amount of protein transferred through the membrane against time using the appropriate mathematical equation for the steady state. Different protein concentrations and pH values were tested. The calculated D M for endoglucanase was in the order of 10 −13 m 2 s −1 whereas the calculated D M for lysozyme was an order of magnitude lower. A diffusion coefficient dependence on the concentration and pH was observed. In addition, the partition coefficient, K M, of the two proteins between the membrane and a solution containing the proteins was calculated.

Production of a banana (Musa cavendishii) extract containing no polyphenol oxidase by ultrafiltration

The objective of this research was the production of a banana extract containing no polyphenol oxidase by ultrafiltration. Banana juice was extracted after inhibition of polyphenol oxidase using a solution containing 0.15 g per 100 ml of sodium metabisulphite and 1 g per 100 ml of ascorbic acid in distilled water to avoid initial browning. Polyphenol oxidase was then retained by ultrafiltration using polysulphone membranes with a cut-off of 20 kDaltons. Two transmembrane pressures, 600 and 800 kPa, were used but 600 kPa was preferred because of the more stable permeate flux which decreased less with time and concentration of extract. © 1999 Society of Chemical Industry

Effect of adsorbed protein on the hydraulic permeability, membrane and streaming potential values measured across a microporous membrane

The effect of the adsorption of a protein, bovine serum albumin (BSA), on the membrane potential, flux reduction and streaming potential measured across a microporous polysulphone membrane with different NaCl solutions and pH values is studied. From electrokinetic phenomena, information about the electrical properties of the membrane (fixed charge concentration and ionic transport numbers) or the membrane/solute interactions (streaming and zeta potentials) can be obtained. The influence of pH and ionic strength on volume flux and streaming potential values is considered. Results show that hydraulic permeability decreases strongly when the pH decreases, having its minimum value at the isoelectric point of the protein; the apparent zeta potential values are also dependent on both pH and salt concentration. Differences in the streaming potential coefficient determined for two membranes fouled under different experimental conditions may be attributed to different mechanisms for the adsorption of proteins in the membrane: (i) a protein deposition on the membrane pores; (ii) an adsorbed layer of protein on the membrane surface. In this latter case, the whole membrane system can be considered as a “composite” or two-layer membrane, and a comparison of the results obtained with both microporous polysulphone and “composite” (microporous+BSA layer) membranes could permit us to determine some parameters related to the protein sublayer.

Characterization of clean and fouled polymeric ultrafiltration membranes by Fourier transform IR spectroscopy–attenuated total reflection

Fourier transform IR spectroscopy was successfully used to study clean and fouled polysulphone ultrafiltration membranes of different pore sizes and from different manufacturers. The attenuated total reflection method was found to be very useful as a surface-characterizing method for membranes. The material of the GR polysulphone membranes of different pore sizes was found to be different. The GR 40 and the GR 51 membranes appear to be made of Udel polysulphone or poly(arylenesulphone ether) while the material of the GR 61 and the GR 81 is made of the more hydrophilic Victrex polyethersulphone and bisphenol A as is the PM 10 membrane. In the structure of the PM 10 membrane some unsubstituted OH groups have been left producing an even more hydrophilic surface. The depth profiling of the clean and the bovine serum albumin fouled GR 51 membranes demonstrated that the protein molecules adsorb more inside the pores of the membrane and less on the surface. This was also confirmed with further analysis of the penetration depth of radiation. The intensity of the peaks caused by the adsorbed protein in the spectrum of the fouled membrane increased when the radiation penetrated deeper into the sample, indicating that more protein was present.

Reduction of Mononuclear Cytokine Production in Hemodialysis Patients Treated with Steam-Sterilized Low-Flux Polysulphone Membranes

An increased cytokine production, correlated with long term complications of uremic disease, has been described during hemodialysis. To identify possible differences in the cytokine release of differently sterilized membranes, we enrolled six uremic patients on chronic hemodialysis. The patients underwent dialysis with ETO-sterilized low-flux polysulphone membranes (F6, Fresenius AG) for at least three months (A1), they were then switched to steam-sterilized polysulphone membranes (F6-HPS Fresenius AG) and further evaluations after one (B1) and two months (B2) were carried out. A final evaluation (A2) was made one month after switching back to F6 dialyzers. At each time period, samples were drawn to measure IL-1beta released by cultured mononuclear cells (MN). Moreover, dialysate samples were collected to test endotoxin levels. C3a and C5a levels were assessed at 0, 5, 15 and 60 min from starting hemodialysis. Anti-ETO IgE levels were also assayed at A1, B1 and A2. The LAL test revealed a good quality dialysate. The mean pre-dialysis IL-1beta levels were 215 pg/million cells at A1; falling to 49 at B1, and 54 at B2 (p<0.01); there was then a sharp rebound at A2: 284, p<0.01. Post-dialysis levels followed the same pattern. No correlation between the dialysate endotoxin level and cytokine release was found. Complement activation did not change and in all the phases of the study no anti-ETO IgE was detected in any of the subjects. Our data suggest that the steam sterilized polysulphone membrane induces a lower cytokine release than the ETO sterilized membrane, although the mechanism by which it does so remains to be clarified.

Remarkable Removal of Beta-2-Microglobulin by On-Line Hemodiafiltration

Eight chronic, anuric hemodialysis patients were randomly treated with a high-flux polysulphone dialyzer (F80), using 6 different modes: conventional bicarbonate hemodialysis (HD), hemodiafiltration (HDF) with a replacement solution at 40, 60, 80 or 100 ml/min in postdilution and 80 ml/min in predilution. The differences in β₂-microglobulin (β2M) reduction ratio and clearance were evaluated statistically by analysis of variance (ANOVA). Both studies revealed no significant difference between HD and HDF40 in postdilution, but an increasing significant difference from HDF60 to HDF100 in postdilution and with HDF80 in predilution. The mean reduction ratio ranged from 49.7 (HD) to 72.7% (HDF 100 ml/min), showing an overall statistically significant difference (p = 0.0000). For the clearance, the range was between 63.8 (HD) and 116.8 ml/min (HDF 100 ml/min) (p = 0.0000). β2M in the effluent dialysate with HDF100 ml/min reached up to a mean of 258 mg/session. Concerning small molecules (BUN, creatinine and P), there was a statistically significant different clearance for creatinine and especially for P with HDF 100 ml/min. Conclusion: HDF with an on-line replacement solution at 100 ml/min and a high-flux and biocompatible polysulphone membrane represents a new tool for enhanced removal of β2M. Besides a significant increase in creatinine and especially in phosphorus clearance is noted.

Immobilization of Bacillus licheniformis cells, producers of thermostable ?-amylase, on polymer membranes

Cells of Bacillus licheniformis 44MB82-G immobilized on different polymer membranes were used for production of thermostable α-amylase. The α-amylase yields of the membrane-immobilized cells were affected by the reactive chemical groups of the carriers and the spacer size. Formaldehyde-activated polysulphone membranes (PS-FA) were the most suitable for effective immobilization. The highest amylase yield (62% increase of the control) and operational stability (97% residual activity after 480 h repeated batch cultivation) were obtained with this system. This was confirmed by scanning electron micrographs. An additional increase of α-amylase production by PS-FA-membrane immobilized cells was achieved in a fluidized-bed reactor.

Tunneling chemical waves

The tunneling of chemical waves through the gaps of different geometrical shapes was studied using a new experimental model based on the polysulphone membranes with the fixed catalyst. Period doubling of the wave train, formation of the wave breaks on the split in polysulphone membrane, drift of the spiral wave along the widening split were observed. The effects were confirmed and studied in details using computer simulation.

Urease immobilized on an aminated polysulphone membrane – inhibition by boric acid

AbstractAn enzymatic membrane for application in the processes of decomposition and removal of urea from aqueous solutions was prepared: jack bean urease was immobilized on an aminated polysulphone membrane by adsorption. The inhibition of the system by boric acid was studied using procedures based on the MICHAELIS‐MENTEN integrated equation (non‐linear regression, and the linear transformations of WALKER and SCHMIDT, JENNINGS and NIEMANN, and BOOMAN and NIEMANN). The reaction was carried out in a 100 mM phosphate buffer of pH 7.0, containing 2 mM EDTA, obtained by neutralization of orthophosphoric acid with NaOH, at an initial urea concentration of 10 mM, and a temperature of 25 °C. The reaction was initiated by the addition of the enzyme to the urea solution, and was monitored by removing samples of the reaction mixture for NH3 determinations by the phenol‐hypochlorite method until the urea was exhausted. The results were compared with those obtained earlier under the same reaction conditions for free urease and urease covalently immobilized on chitosan. The inhibition was found to be competitive, similar to that of the free enzyme and urease immobilized on chitosan, with inhibition constants Ki equal to 0.36, 0.19 and 0.60 mM. The results show that adsorption of the enzyme on a polysulphone membrane changed the enzyme to a lesser degree than covalent immobilization of the enzyme on a chitosan membrane.

Cell-associated adhesion molecules as early markers of bioincompatibility.

Transient nature of adhesive interactions occurring during cell margination is mainly dependent on expression of selectins which are shed by activated cells. This shedding in the circulation may play an important role as anti-inflammatory mediator. Haemodialysis is also associated with P-selectin (CD62P)/sialyl-Lewis(x) (CD15s) interactions which mediate platelet-leukocyte coaggregation. We further investigated the mechanisms underlying leukocyte margination during haemodialysis. CD15s, CD11b and CD61 expression on circulating leukocytes from patients dialysed on synthetic membranes (modified polyacrylonitrile (SPAN), polysulphone (PS), and polyacrylonitrile (AN69) was assessed by cytofluorometry in a prospective crossover trial. We measured plasma levels C3a/C3a desArg, soluble CD62P, and CD62E molecules obtained from patients and healthy individuals. Expression of CD11b and CD15s was upregulated on neutrophils from patients dialysed with SPAN and PS membranes during the dialysis session. A significant negative correlation was found between the expression of CD11b or CD15s molecules and neutrophil counts as well as between CD15s expression and monocyte counts during haemodialysis. As assessed by CD61 expression on leukocytes, we observed that platelets bound significantly onto both neutrophils and monocytes during dialysis with both membranes. A significant positive correlation was found between the expression of CD11b molecules and the percentage of CD61+ monocytes counts during SPAN and PS dialysis. We found a significant increase of soluble CD62P in plasma samples obtained from haemodialysed patients before the dialysis session as compared to the levels detected in plasma from healthy individuals. This study documents a major role of CD15s, CD11b, CD61, CD62P molecules in the transient leukocytes activation and margination during haemodialysis on synthetic membranes despite their low complement-activating properties.

An enzymatic approach to the cleaning of ultrafiltration membranes fouled in abattoir effluent

Membrane fouling severely curtails the economical and practical implementation for the purification of biologically related process streams such as abattoir effluent (Jacobs, WRC Report no. K5/362, 1991, Pretoria, South Africa [1]). Mechanical and chemical removal of foulants usually lead to membrane damage and additional pollution. Enzymes, specific for the degradation of proteins and lipids, were tested as key components of biological cleaning regimes for membranes fouled in abattoir effluent. Fouling of polysulphone membranes was assessed as previously described by Maartens et al. (J. Membrane Sci., 119 (1996) 1 [2]) and optimal enzyme concentrations and incubation times were determined for the different preparations. The ability of each cleaning agent to remove adsorbed protein and lipid material, as well as their ability to restore the water-contact angle and the pure-water flux of the fouled membranes, were determined and compared. These variables were also used to compare the cleaning efficiency of enzymatic cleaning agents with conventional chemical agents under optimal conditions. The enzymes and enzyme detergent mixtures were effective cleaning agents and the pure-water flux of statically fouled membranes could be restored by treatment with these agents.

Shear controlled model of the ultrafiltration of soy suspensions

The ultrafiltration of the aqueous extract of full-fat soy flour was investigated as a complex suspension of proteins, lipids and carbohydrates where the foulant layer is the major resistance. Ultrafiltration was performed on both homogenised and unhomogenised soy extracts using a flat plate module and two polysulphone membranes. The permeate flux profiles for constant recirculation flow exhibited a combination of falling-flux and constant-flux regions. The mass transfer model was not applicable to these profiles. Both regions were modeled by the shear controlled model J=J iτ r nae −bC. The model was also effective in correlating the flux where the retentate flow was reduced for increasing concentration at constant pressure drop over the module. Wall shear stress had a larger effect on the permeate flux for the homogenised extract ( n = 0.7) than for the unhomogenised extract ( n = 0.5). The wall shear stress was shown to have minimal effect on displacing the foulant layer. The major effect of the wall shear stress was to sweep away the gel layer preventing it from binding to the foulant layer.

Lymphocyte subsets in dialyser eluates: a new parameter of bioincompatibility?

During haemodialysis (HD), several adverse reactions in peripheral blood can occur, which have been attributed to the bioincompatibility of the dialyser membrane. Utilizing a dialyser elution technique, we have demonstrated that polymorphonuclear cells (PMN) manifested non-membrane dependent signs of activation during HD with cellulose triacetate (CTA), cuprammonium (CU) and polysulphone (PS) membranes. In the present study, we employed this elution technique to investigate the influence of HD with these membranes on lymphocytes. Eight patients were studied during HD with CTA, CU, and PS dialysers in a randomized crossover design. Dialyser elution was performed after 3 h of HD. Besides total leukocyte count and differentiation, lymphocyte subpopulations and activation status in peripheral blood and dialyser eluates were analysed by flow cytometry. Only with CU was a significant leukocyte decrease observed in peripheral blood at 30 min (P<0.001). Neither the total number of lymphocytes nor the proportion of T(CD3+) and B(CD19+) cells had markedly changed after HD with either membrane. Meanwhile, all membranes induced a relative decline in natural killer cells -NK(CD3-/CD16+/56+)- at the end of dialysis, although this was only significant for CTA (P=0.04). As for the T-lymphocyte subsets, the proportion of CD4+ cells had markedly increased after three hours of HD with all three dialysers, CTA and PS being significant (P<0.05). Dialyser eluates contained 33.8-82.2 x 10(6) cells, CTA yielding the highest cell counts. The majority (81-91%) of the eluted cells consisted of PMN dialyser eluates versus peripheral blood: P<0.05), whereas only few lymphocytes were found (4-13%, absolute 2.6 x 10(6)). Lymphocyte subpopulations in dialyser eluates were comparable to peripheral blood at t 180 in case of CTA and CU. In contrast PS eluates contained significantly fewer T-cells (37%), but more B-cells (22%) and NK-cells (30%) in comparison with peripheral blood at 180 min (peripheral blood: 79, 6 and 16% respectively; P<0.05). The expression of activation markers on T-cells (HLA-DR, CD25) in dialyser eluates was comparable with peripheral blood. Conclusions. The absolute number of lymphocytes in dialyser eluates of CTA, CU, and PS dialysers was low (mean 2.6 x 10(6)) in comparison with peripheral blood (mean 1.4 x 10(9)/l). Whereas non-selective adhesion occurred in CU and CTA dialysers, a selective adhesion pattern of lymphocyte subpopulations was observed in case of PS, suggesting a difference in bioincompatibility. Apparent T-cell activation was not noted, either in peripheral blood or in dialyser eluates. Because PMN in the dialyser eluates of three different membranes showed similar activation patterns in a previous study, we hypothesize that eluted lymphocyte, rather than PMN, represent a preferable parameter of bioincompatibility.

Continuous separation of proteins by poly(vinyl alcohol) shielded Multichannel Flow Electrophoresis

A hydrophilic polysulphone membrane spaced multicompartment electrolyzer for Multichannel Flow Electrophoresis (MFE) was developed. Application of poly(vinyl alcohol) (PVA) in MFE resulted in a 35% increase of protein transmembrane flux. Continuous separation of bovine serum albumin (BSA) and haemoglobin bovine blood (HBB) model mixture by PVA shielded MFE yielded 56mg BSA and 48mg HBB per hour. The average recovery was 65%.

Chemical clocks on the basis of rotating waves. Measuring irrational numbers from period ratios

An ink-jet printer is utilized to generate catalyst-loaded patterns such as circles, triangles, and squares on polysulphone membranes. These patterns define excitable domains for the Belousov-Zhabotinsky reaction in which rotating waves can be initiated. The resulting wave propagation is exploited for the implementation of chemical clocks with stable period ratios. Based on this approach the irrational numbers π, √2, and the golden mean are measured with a relative error of 0.1−0.2%.