Bovine Serum Albumin Flux Research Articles

Preparation and Characterization of CA−PEG−TiO2 Membranes: Effect of PEG and TiO2 on Morphology, Flux and Fouling Performance

Modified cellulose acetate (CA) membranes were prepared by dissolving the polymers in a mixture of acetone (AC) and N, N dimethylacetamide (DMAc) (70:30) solvent and deionized (DI) water was used in the coagulation bath. The introduction of polyethylene glycol (PEG) additive and TiO2 nanoparticles (NPs) into the casting solution has changed the structures of the resulting membranes during the phase inversion process. Effects of PEG additive and TiO2 NPs on the preparation of the phase-inverted CA ultrafiltration membrane were investigated in terms of morphology, equilibrium water content (EWC), pure water flux (PWF), hydraulic resistance, thermal stability, water contact angle (WCA) and anti-fouling performance. Improvements in average pore size, porosity, thermal stability, and the hydrophilic nature of the CA membranes was detected after the introduction of PEG and TiO2 simultaneously to the polymer matrix. Thermo gravimetric analysis (TGA) results confirmed that the interaction between TiO2 and the degradation temperature of the CA membrane were significantly improved. The anti-fouling performance and the flux recovery potential of the membranes were investigated using the bovine serum albumin (BSA) protein. The M3 (CA-PEG-TiO2) membrane (10.5 Wt. % CA: 4 Wt. % PEG: 2 Wt. % TiO2) exhibited the highest BSA flux result and normalized flux recovery ratios (NFR) for the three fouling cycles.

Exploring the effects of graphene oxide concentration on properties and antifouling performance of PEES/GO ultrafiltration membranes

In this study, asymmetric polyphenylene-ether-ether-sulfone (PEES) ultrafiltration (UF) membranes containing graphene oxide (GO) were prepared via non-solvent-induced phase separation process and N-methyl pyrrolidone was used as a solvent. The synthesis of GO was confirmed by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analysis. The morphology of the prepared GO nanosheets was observed by field emission scanning electron microscope (FESEM) and transmission electron microscope. The membranes prepared with increasing concentrations of GO nanosheets were characterized by attenuated total reflectance-FTIR, SEM, atomic force microscopy (AFM), contact angle, and UF studies. The FTIR spectra of the GO embedded membranes reveal large amounts of –OH groups present due to the existence of GO nanosheets which improved its surface hydrophilicity. The contact angle of PEES/GO membrane was significantly lower than PEES membrane. The SEM pictures showed that PEES/GO UF membranes had a sponge-like substructure with the increased porosity and pore size. An AFM topography imaging showed that roughnesses of the modified membranes were improved compared to the pristine PEES membrane. The UF studies showed that the pure water flux ( JW) and the bovine serum albumin flux ( JP) were increased with the incorporation of GO into the blend solution. For the membrane with 0.1% GO content, JW increased by 75% and JP improved twofold which correspond to the maximum values of 186 and 113 L m−2 h−1, respectively. Furthermore, the flux recovery ratio results suggested that PEES/GO membranes have better antifouling characteristics due to the changes in membrane morphology and surface hydrophilicity.

Arabic gum as a novel pore-forming and hydrophilic agent in polysulfone membranes

In this study, novel polysulfone (PS) membranes blended with Arabic Gum (AG) as pore forming agent were prepared via phase inversion technique. The performances of the newly synthesized PS/AG membranes cast at different AG contents (0.1–3.0wt%) in dope solutions were examined for their surface morphology, cross-section, surface charge density, hydrophilicity, and mechanical strength using scanning electron microscopy (SEM), zeta potential, contact angle measurements and tensile testing, respectively. The antifouling properties of PS/AG membranes were evaluated during filtration of bovine serum albumin (BSA) solutions while the antibacterial tests were assessed using Escherichia coli bacteria. The addition of AG to the casting solutions displayed a remarkable enhancement on PS membrane hydrophilicity, surface charge, flux, rejection and antibacterial properties. The prepared PS membranes cast with 3wt% AG possessed high oil rejection and BSA flux recovery of about 98% and 80% respectively. In addition, the mechanical properties of the cast membrane increased by 52% compared to the pristine PS membrane. Overall, this study shows that, AG is promising additives that can be used for fabrication of ultrafiltration membranes with improved performance for water treatment applications.

Arsenic removal from drinking water by direct contact membrane distillation

The enantiomeric and racemic effects of tartaric acid (TA) on the properties of polysulfone (PSn) ultrafiltration membranes were studied in terms of morphology and hydrophilicity (HPCT) of membrane. Asymmetric membranes were prepared by direct blending of polyvinyl pyrrolidone (PVP) with D-TA and DL-TA in membrane casting solution. FTIR analysis was done for the confirmation of the reaction of PVP and TA in blended membranes and plain PSn membranes. Scanning electron microscope (SEM), field emission scanning electron microscope (FESEM) and atomic force microscopy (AFM) were used for analyzing the morphology and structure of the resulting membranes. The membranes were characterized in terms of pure water flux (PWF), hydraulic permeability and HPCT. PWF increased from 52 L/m2h to 79.9 L/m2h for plain and D-TA containing PSn membrane, respectively. Water contact angle also found to be decreased from 68° to 55°. In Additionally, permeation and rejection behavior of prepared membranes was studied by bovine serum albumin (BSA) solution. A considerable increase in BSA flux (from 19.1 L/m2h for plain membrane to 32.1 L/m2h for D-TA containing membrane) was observed. FESEM images affirm that the pore size of the membranes decreases and the membrane permeability increases from 0.16 to 0.32 by the addition of D-TA in the membrane. D-TA increases the HPCT whereas; DL-TA decreases the HPCT of PSn membrane. PVP (average molecular weight of 40000 Da) with D-TA (1 wt%) gave best performance among all the membranes for each parameter.

Optimization of lactoferrin and bovine serum albumin separation using ion-exchange membrane chromatography

Lactoferrin (LF), which is a high value minor whey protein, has recently received extensive attention from research scientists and industry due to its multifunction and potential therapeutic applications. In this study, the separation of two similar-sized proteins: bovine serum albumin (BSA) and LF was investigated using strong cation and anion exchange membrane chromatography (MC). Single protein and BSA–LF mixture adsorption were performed on Sartobind Q75 and S75 at pH between the LF and BSA isoelectric points. Identical breakthrough curves were obtained for both single protein and binary protein mixture, which suggests that there is no protein adsorption competition at the binding sites. The process optimization was further studied to yield optimum buffer and operating conditions. The highest BSA flux per membrane area (728.00gm−2h−1) was obtained using 100mM phosphate buffer solution at pH 6.0 on the cation exchange membrane, whereas LF was bound to the membrane with the dynamic binding capacity at 10% breakthrough (DBC10%) of about 60mg. On the anion exchange membrane, LF was collected in the effluent at the flux of 287.46gm−2h−1 using 5mM phosphate buffer at pH 6.0, while BSA was retained on the membrane with DBC10% equal to 60.96mg. The combination effect between pH change and hydrophobic interaction improved the eluted protein mass for both anion and cation exchangers. Furthermore, the completed separation cycle was operated with the Sartobind S75 device with a short process time of 34.19min and optimal LF productivity over 2628.84mgmL−1h−1. This study confirms the advantage of MC for the separation of biomolecules with similar molecular weight and different isoelectric points, such as BSA–LF mixture separation. This fast and effective protein separation method could be applied at an industry scale.

Preparation and characterization of carboxyl multi-walled carbon nanotubes/calcium alginate composite hydrogel nano-filtration membrane

Carboxyl multi-walled carbon nanotubes/calcium alginate (CMWCNT/CA) composite hydrogel nano-filtration membrane was prepared using polyethylene glycol 400 as the pore-forming agent. The membrane was characterized by SEM, TEM and FT-IR. And the strength, anti-fouling property and dye rejection were investigated. Results showed that the CMWCNT/CA membrane had a high tensile strength up to 1.83MPa. The flux of bovine serum albumin (BSA) solution was 96.87% of the pure water flux (PWF), indicating that the membrane exhibited good anti-fouling property. Even after the saturated adsorption, the rejection for Congo red still reached 98.62%.

Preparation and characterization of stimuli-responsive hydrophilic polysulfone membrane modified with poly (N-vinylcaprolactam-co-acrylic acid)

Novel polysulfone (PSF) ultrafiltration membranes with pH and thermo sensitivity were prepared using the copolymer poly (N-vinylcaprolactam-co-acrylic acid) (poly (VCL-co-AA)) as an additive. The copolymer was synthesized by free radical solution polymerization, and directly blended in membrane casting solution to prepare the asymmetric membranes by phase inversion method. The presence of copolymer in blended membranes was confirmed by comparing IR spectra of plain PSF membrane and blended PSF membrane. The morphology and structure of the resulting membranes were observed by scanning electron microscope (SEM) and field emission scanning electron microscope (FESEM). The membranes were characterized in terms of pure water flux (PWF), hydraulic permeability and hydrophilicity. PWF increased from 1 to 18.8L/m2h, when wt.% of copolymer increases from 0 to 2.5. Similarly, water contact angle decreased from 76° to 58°. The blended membranes showed evident of pH and thermo sensitivity. The stimuli responsive behaviour of membranes was also investigated in terms of pH and temperature. In addition, solution of bovine serum albumin (BSA) was used to study the permeation and antifouling performance of prepared membranes. A significant increase in BSA flux (from 0.061L/m2h for plain membrane to 3.37L/m2h for membrane with 6 wt.% of copolymer) and decrease in membrane fouling was observed.

Study on preparation and performance characteristics of polyvinyl chloride-co-vinyl acetate-modified membranes on the nonwoven fabrics

This work reports that membranes were cast from solution consisting of dimethylformamide, polyethylene glycol, and polyvinyl chloride-co-vinyl acetate (VC-co-VAc-OH) to prepare flat-sheet membranes on the nonwoven fabrics via phase inversion method. The influence of various factors (solid content, the content of additive, environmental temperature, relative humidity, evaporation time of solvent, coagulation temperature, and coagulation time) on membrane performance (the pure water flux and the retention of bovine serum albumin (BSA)) were studied in the film-forming process of the VC-co-VAc-OH membrane. The results showed that the membrane with higher pure water flux (289.6 mL cm-2 h-1) and good retention of BSA (86.7%) can be prepared under optimized preparation conditions. In addition, the carbon dioxide gas, which was produced by a chemical reaction between glacial acetic acid in the casting solution and sodium carbonate in coagulation medium, can improve the antifouling ability of the membrane. The membrane prepared by chemical reaction under optimum conditions (the molar ratio between Na2CO3 and glacial acetic acid is 0.5:1) possess higher pure water flux (457.7 mL cm-2 h-1) and good retention of BSA (90.7%).

Prediction of impacts of fabrication conditions on the filtration performance of homemade VC-co-VAc-OH microfiltration membrane by Support Vector Machine (SVM)

In this study, the support vector machine (SVM) model which was based on restricted data sets (the size of the training set is small or small training sample) was applied to predict the permeate flux and rejection of Bovine serum albumin (BSA) of homemade VC-co-VAc-OH microfiltration membrane as the function of fabrication conditions. The membrane preparation conditions (the solid content, the additive content, environmental temperature, the relative humidity, evaporation time of a volatile solvent, precipitation temperature, and precipitation time) were input variables; pure water flux and rejection of BSA were output variables. The results showed that the detailed relationships between fabrication conditions and filtration performance of the membranes could be established. Excellent agreements between the prediction of SVM model and the experiments validate that SVM model has sufficient accuracy. Furthermore, the results predicted by SVM model were compared with those predicted by artificial neural network (ANN) model which was widely used in the optimization of nonlinear relationships. It is found that the deviations of both the training and the predicting data obtained by SVM model are much smaller than those by ANN models. Hence, SVM model can be used as an efficient approach to optimize fabrication conditions of homemade VC-co-VAc-OH microfiltration membrane.

Effect of ionic strength and protein concentration on the transport of proteins through chitosan/polystyrene sulfonate multilayer membrane

The influence of ionic strength and protein concentration on the transport of bovine serum albumin (BSA), ovalbumin and lysozyme through chitosan (CHI)/polystyrenesulfonate (PSS) multilayers on polyether sulfone supports are investigated under ultrafiltration conditions. The percentage transmission and flux of BSA, ovalbumin and lysozyme were found to increase with increase in salt concentration in the protein. The percentage transmission of BSA through 9 bilayer membrane was found to increase from 5.3 to 115.6 when the salt concentration was varied from 0 to 1 M. It was observed that 0.1 M NaCl in BSA solution is capable of permeating all the BSA. When the salt concentration in BSA was further increased, a negative solute rejection (solute enrichment in permeate) was found to take place. With 9 bilayer membrane, the percentage transmission of ovalbumin was found to increase from 23.3 to 125.8 when the salt concentration in protein was increased from 0 to 0.05 M. The effect of protein concentration on protein transport is studied taking BSA as a model protein. BSA was rejected by the multilayer membrane at all the studied concentrations (0.25, 0.5, 1 and 2 mg/ml). With increase in feed concentration, maximum rejection of protein occurred at higher number of CHI/PSS bilayers. BSA solution flux was found to decrease with an increase in BSA concentration. This study indicates that it is possible to fine tune the transport properties of proteins through multilayer membranes by varying the concentration and ionic strength of protein solutions.

Protein transport through gold-coated, charged nanopores: Effects of applied voltage

The flux of bovine serum albumin and bovine hemoglobin through charged nanopores inside polymeric membranes is analysed as a function of the applied voltage to the nanopore surface, the solution ionic strength and pH. The electrostatic interaction of the protein with the nanopore surface gives low transport rates except at the protein isoelectric point and the minimum of the effective, voltage-induced nanopore charge. This electrostatic sieving effect allows for the separation of proteins with similar molecular weights.

Disruption of Tight Junctions during Traversal of the Respiratory Epithelium by Burkholderia cenocepacia

Burkholderia cenocepacia is an opportunistic bacterial species capable of causing life-threatening respiratory tract infection in persons with cystic fibrosis (CF). Unlike most other pathogens in CF, which typically remain confined to the endobronchial spaces, B. cenocepacia can traverse airway epithelium to cause bacteremia and sepsis. The mechanisms by which this occurs, however, are unknown. We examined the transmigration of B. cenocepacia through polarized respiratory epithelium. Representatives of three "epidemic" lineages common among CF patients in North America were able to traverse polarized 16HBE14o- cells in vitro. Transmigration of bacteria was associated with significant perturbations in epithelial permeability, as measured by a loss of transepithelial electrical resistance and increased flux of bovine serum albumin across the cell layer. Terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling and trypan blue exclusion assays, as well as lactate dehydrogenase levels, did not indicate excessive cytotoxicity or cell death in infected cell layers. Rather, confocal fluorescence microscopy demonstrated the loss of occludin from tight junctions. In contrast, zonula occludens 1 was well preserved along intercellular borders. Western blot analysis showed a shift in the major occludin isoforms from high- to low-phosphorylation states during infection. These observations suggest that B. cenocepacia traverses polarized respiratory epithelium by the dephosphorylation and dissociation of occludin from the tight-junction complex.

Protein tyrosine phosphatase activity regulates endothelial cell-cell interactions, the paracellular pathway, and capillary tube stability.

Protein tyrosine phosphorylation is tightly regulated through the actions of both protein tyrosine kinases and protein tyrosine phosphatases. In this study, we demonstrate that protein tyrosine phosphatase inhibition promotes tyrosine phosphorylation of endothelial cell-cell adherens junction proteins, opens an endothelial paracellular pathway, and increases both transendothelial albumin flux and neutrophil migration. Tyrosine phosphatase inhibition with sodium orthovanadate or phenylarsine oxide induced dose- and time-dependent increases in [14C]bovine serum albumin flux across postconfluent bovine pulmonary artery endothelial cell monolayers. These increases in albumin flux were coincident with actin reorganization and intercellular gap formation in both postconfluent monolayers and preformed endothelial cell capillary tubes. Vanadate (25 microM) increased tyrosine phosphorylation of endothelial cell proteins 12-fold within 1 h. Tyrosine phosphorylated proteins were immunolocalized to the intercellular boundaries, and several were identified as the endothelial cell-cell adherens junction proteins, vascular-endothelial cadherin, and beta-, gamma-, and p120-catenin as well as platelet endothelial cell adhesion molecule-1. Of note, these tyrosine phosphorylation events were not associated with disassembly of the adherens junction complex or its uncoupling from the actin cytoskeleton. The dose and time requirements for vanadate-induced increases in phosphorylation were comparable with those defined for increments in transendothelial [14C]albumin flux and neutrophil migration, and pretreatment with the tyrosine kinase inhibitor herbimycin A protected against these effects. These data suggest that protein tyrosine phosphatases and their substrates, which localize to the endothelial cell-cell boundaries, regulate adherens junctional integrity, the movement of macromolecules and cells through the endothelial paracellular pathway, and capillary tube stability.

Role of mass transfer coefficient with suction including property variations to predict limiting phenomena during ultrafiltration

Analytical expressions for limiting flux, limiting concentration at the membrane surface, limiting operating pressure are developed for osmotic pressure controlled cross flow ultrafiltration. Modified Sherwood number relationships incorporating the effects of suction and variations of physical properties are used to estimate mass transfer coefficient in a rectangular geometry. The model is solved to predict the limiting flux of bovine serum albumin and dextran data, obtained from the literature. A parametric study of limiting flux with different parameters (e.g., Reynolds number, feed concentration, real retention of the membrane, etc.) is also carried out. Further, the analysis is also carried out for a partially retentive membrane. Explicit quantification of limiting pressure would be of immense help for the design engineers from both operational and economic points of view.

Macromolecular transport across the rabbit proximal and distal colon

BackgroundAlthough many studies have investigated macromolecular uptake in the stomach and small intestine, little is known about macromolecular uptake in the colon.AimsTo investigate the mechanisms involved in the transport of...

Endotoxin induces endothelial barrier dysfunction through protein tyrosine phosphorylation.

Bacterial lipopolysaccharide (LPS) induces actin reorganization, intercellular gap formation, and endothelial barrier dysfunction in vitro. We studied whether LPS-induced increments in 14C-labeled bovine serum albumin (BSA) flux across bovine pulmonary artery endothelial cell (EC) monolayers and actin depolymerization are mediated through protein tyrosine phosphorylation. Lysates from EC exposed to LPS derived from Escherichia coli 0111:B4 (100 ng/ml, 1 h) demonstrated increased tyrosine phosphorylation of the cytoskeletal protein paxillin. Protein tyrosine kinase inhibition, with either herbimycin A (1 microM) or genistein (50 micrograms/ml), protected against LPS-induced actin depolymerization, intercellular gap formation, and increments in [14C]BSA flux. In contrast, inhibition of tyrosine phosphatases with sodium orthovanadate (2.5 microM) or phenylarsine oxide (0.1 microM) enhanced the LPS-induced increments in the G-actin pool and the transendothelial flux of [14C]BSA compared with that seen after exposure to LPS alone. Our data indicate that the influence of LPS on EC actin organization and barrier function is mediated, in part, through a signaling pathway that is dependent on tyrosine phosphorylation.

Organotin — environmental fate and effects

Novel polysulfone (PSF) ultrafiltration membranes with pH and thermo sensitivity were prepared using the copolymer poly (N-vinylcaprolactam-co-acrylic acid) (poly (VCL-co-AA)) as an additive. The copolymer was synthesized by free radical solution polymerization, and directly blended in membrane casting solution to prepare the asymmetric membranes by phase inversion method. The presence of copolymer in blended membranes was confirmed by comparing IR spectra of plain PSF membrane and blended PSF membrane. The morphology and structure of the resulting membranes were observed by scanning electron microscope (SEM) and field emission scanning electron microscope (FESEM). The membranes were characterized in terms of pure water flux (PWF), hydraulic permeability and hydrophilicity. PWF increased from 1 to 18.8 L/m2h, when wt.% of copolymer increases from 0 to 2.5. Similarly, water contact angle decreased from 76° to 58°. The blended membranes showed evident of pH and thermo sensitivity. The stimuli responsive behaviour of membranes was also investigated in terms of pH and temperature. In addition, solution of bovine serum albumin (BSA) was used to study the permeation and antifouling performance of prepared membranes. A significant increase in BSA flux (from 0.061 L/m2h for plain membrane to 3.37 L/m2h for membrane with 6 wt.% of copolymer) and decrease in membrane fouling was observed.

Transport of albumin into the intestinal lumen of the rat

The intestine is considered a major site for the breakdown and clearance of serum proteins. The mechanism of transport of macromolecules from the serosa into the lumen is unclear. The present study was designed to characterize the serosal to mucosal movement of albumin. Transport of bovine serum albumin (BSA) was assessed in short-circuited Ussing chambers, using stripped rat jejunum devoid of Peyer's patches. To define the kinetics of serosal to mucosal albumin transport the serosal surface was exposed to BSA at varying concentrations (0.5-5 mg.mL-1). Fluids from the mucosal compartment were sampled over time and assayed for immunologically intact BSA by ELISA. All subsequent experiments utilized a concentration of cold BSA (2 mg.mL-1) that produced maximal levels of intact BSA transport. To assess total BSA transport (intact BSA plus degraded BSA), 10 microCi (1 Ci = 37 GBq) 125I-labelled BSA was added to the serosal surface in addition to 2 mg.mL-1 cold BSA. To further characterize BSA transport tissues were treated with sodium fluoride (NaF) (metabolic inhibitor) or colchicine (an inhibitor of microtubule polymerization) or with the nerve blocker tetrodotoxin (TTX). All experiments using inhibitors were performed in paired tissues obtained from the same animal. Transport of intact BSA into the intestinal lumen was a saturable process, with a Vmax of 251 +/- 13 ng.cm-2.h-1 and a Km of 0.72 +/- 0.1 mg.mL-1, and represented 7% of the total BSA flux into the intestinal lumen. In the presence of NaF (2 x 10(-3) M), transport of both intact and total BSA was significantly inhibited (intact: control 374 +/- 80 vs. NaF 46 +/- 11, 88% inhibition; total: control 3288 +/- 296 vs. NaF 2550 +/- 235 ng.cm-2.h-1, 22% inhibition; p < 0.05). In addition, colchicine significantly inhibited intact BSA transport (control 339 +/- 15 vs. colchicine 206 +/- 13 ng.cm-2.h-1, 39% inhibition; p < 0.05). TTX had no effect on intact BSA flux. The findings suggest that transport of intact BSA from the serosa into the intestinal lumen is a saturable, energy-dependent process, which involves microtubules but is not under neural regulation.

Protein movement across cultured guinea pig trachea: specificity and effect of transcytosis inhibitors.

Airway surface liquid (ASL) is a complex fluid with solutes including electrolytes, lipids, mucins, and proteins. The proximal airways are absorptive for most solutes, including proteins. We investigated the process of protein movement across confluent primary cultures of guinea pig trachea grown on filters using fluorescent-labeled bovine serum albumin (BSA), ovalbumin (OA), and 70-kDa dextran (Dex). We found marked asymmetry of BSA and OA transepithelial flux, with apical-to-basolateral flux (JA-->B) 10 times greater than the opposite direction (JB-->A) for both proteins. The apparent permeability for Dex was the same as that for proteins in the basolateral-to-apical direction and showed no asymmetry. Increasing concentrations of unlabeled BSA, OA, or transferrin inhibited JA-->B for both BSA and OA without affecting Dex movement. Cooling reduced JA-->B for BSA without affecting JB-->A. Monensin and nocodazole each reduced JA-->B for BSA and OA without affecting JB-->A. Monensin eliminated all asymmetry for BSA movement. Brefeldin A did not affect JA-->B for either protein but did increase JB-->A for BSA. Treatment with the protease inhibitors increased JA-->B for BSA. Western immunoblotting demonstrated immunologically intact protein in the downstream compartment. We conclude that there is transcytosis of proteins across cultured trachea epithelium in the apical-to-basolateral direction, which is monensin sensitive, involves microtubules, is not dependent on proteolysis, and is not protein species specific. This process may be important for maintenance of the ASL, and defects in this process may contribute to the abnormally thickened airway secretion seen in airway diseases.

Improvement of membrane permeation performance by ultrasonic microfiltration.

To prevent membrane fouling, cross-flow microfiltration with ultrasonic wave cleaning was carried out using a model suspension containing both baker’s yeast and bovine serum albumin (BSA). The effects of ultrasonic waves on the permeate flux and rejection of BSA were studied.The steady-state flux obtained in filtration with ultrasonic waves was four to six times greater than that without ultrasonic waves, and a high flux was obtained, even at a low feed flow velocity. There was an optimum membrane pore size and an optimum operating pressure. It was found that ultrasonic waves were very effective for removing the cake layer deposited on the membrane surface and preventing the plugging of the membrane pores.A filtration method in which a feed pump and an ultrasonic generator were operated alternately was very effective for enhancing the flux and solute permeation rate during cross-flow microfiltration.