Unit Area Of Membrane Research Articles

Asymmetric osmotic water permeation through a vesicle membrane.

Understanding the water permeation through a cell membrane is of primary importance for biological activities and a key step to capture its shape transformation in salt solution. In this work, we reveal the dynamical behaviors of osmotically driven transport of water molecules across a vesicle membrane by molecular dynamics simulations. Of particular interest is that the water transport in and out of vesicles is highly distinguishable given the osmotic force are the same, suggesting an asymmetric osmotic transportation. This asymmetric phenomenon exists in a broad range of parameter space such as the salt concentration, temperature, and vesicle size and can be ascribed to the similar asymmetric potential energy of lipid-ion, lipid-water, lipid-solution, lipid-lipid, and the lipid-lipid energy fluctuation. Specifically, the water flux has a linear increase with the salt concentration, similar to the prediction by Nernst-Planck equation or Fick's first law. Furthermore, due to the Arrhenius relation between the membrane permeability and temperature, the water flux also exhibits excellent Arrhenius dependence on the temperature. Meanwhile, the water flux shows a linear increase with the vesicle surface area since the flux amount across a unit membrane area should be a constant. Finally, we also present the anonymous diffusion behaviors for the vesicle itself, where transitions from normal diffusion at short times to subdiffusion at long times are identified. Our results provide significant new physical insights for the osmotic water permeation through a vesicle membrane and are helpful for future experimental studies.

Effect of membrane morphology on rising properties of filtration resistance in microfiltration of dilute colloids

The effect of membrane morphology on the flux decline behaviors in dead‐end unstirred microfiltration of very dilute colloids of polystyrene latex was examined using mixed cellulose ester and cellulose acetate membranes with interconnected tortuous pores and track‐etched polycarbonate membranes with uniform straight cylindrical pores. The plots of reciprocal filtration rate against the filtrate volume per unit membrane area for the former two membranes exhibit concave downward curves in the initial period when the membrane pore blocking is significant, whereas the plot for the latter shows a concave upward curve in that period. The former results were described by a serial resistance model consisting of the initial membrane pore blocking followed by filter cake growth, and the latter was represented by a parallel resistance model in which the pore blocking and cake growth develop simultaneously from the beginning of filtration. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3511–3522, 2017

Compression and expansion properties of filter cake accompanied with step change in applied pressure in membrane filtration

Abstract In order to well elucidate the true nature of filter cake formed in membrane filtration of aqueous colloids, the transient flux decline behaviors accompanied with step-up and step-down changes in the applied filtration pressure during the course of constant pressure filtration were investigated by carrying out both microfiltration experiments of kaolin slurry and ultrafiltration experiments of nanosilica sol under various experimental conditions. When the applied pressure was increased stepwise, for each colloid the plot of the reciprocal filtration rate vs. the filtrate volume per unit membrane area referred to as the Ruth plot tends to approach a linear relationship obtained in constant pressure filtration conducted under the increased pressure condition from the beginning of filtration, after a transient period when the preformed cake under the initial pressure was compressed. In contrast, in the case of the step-down change in the applied pressure, when the volume of the preformed cake is adequate, the plot after a transient period tends to approach a higher straight line parallel to a linear relationship for constant pressure filtration conducted under the decreased pressure condition from the beginning. Such flux decay behaviors were well described by the expression having two constants: one is the constant representing the final filterability for the preformed filter cake, and the other is the rate constant describing the change rate in the structure of preformed cake resulting from a pressure jump. Moreover, the influence of experimental conditions on the cake reversibility and the rate constant was revealed both for kaolin slurry and for nanosilica sol.

Investigation of a solar energy driven and hollow fiber membrane-based humidification–dehumidification desalination system

A solar energy driven and membrane-based air humidification–dehumidification desalination (MHDD) system is proposed. A test rig is designed and constructed to investigate the performance of the system. The test rig consists of a U-tube evacuated solar collector, a heat storage water tank, a membrane-based humidifier (hollow fiber membrane module) and a dehumidifier (a fin-and-tube heat exchanger). A theoretical model for the whole system simulation is developed and validated. Performance indices of the system, such as the specific water production rate on the basis of unit area of membrane (SWR), specific electric energy consumption on unit volume of water production (SEC), coefficient of performance (COP) and electric coefficient of performance (COPE) are investigated. The effects of various parameters including the saline water flow rate, the air flow rate and the packing fraction of the membrane module, etc., on system performance are examined. It indicates that solar energy accounts for 92.0% of the energy consumption by the whole system. Sensible heat losses account for most of the energy losses from the system. High-purity water is produced by this system at a SWR of 25.88kgm−2d−1, a SEC of 19.23kWh/m3, a COP of 0.75 and a COPE of 36.13. The feasible operating parameters investigated are: hot saline water flow rate, 236L/h for per unit area of membrane; air flow rate, 25m3/h for per unit area of membrane; module packing faction, 30%.

Organic solvent-induced changes in membrane geometry in human SH-SY5Y neuroblastoma cells – a common narcotic effect?

Exposure to organic solvents may cause narcotic effects. At the cellular level, these narcotic effects have been associated with a reduction in neuronal excitability caused by changes in membrane structure and function. In order to critically test whether changes in membrane geometry contribute to these narcotic effects, cultured human SH-SY5Y neuroblastoma cells have been exposed to selected organic solvents. The solvent-induced changes in cell membrane capacitance were investigated using the whole-cell patch clamp technique for real-time capacitance measurements. Exposure of SH-SY5Y cells to the cyclic hydrocarbons m-xylene, toluene, and cyclohexane caused a rapid and reversible increase of membrane capacitance. The aliphatic, nonpolar n-hexane did not cause a detectable change of whole-cell membrane capacitance, whereas the amphiphiles n-hexanol and n-hexylamine caused an increase of membrane capacitance and a concomitant reduction in membrane resistance. Despite a large difference in dielectric properties, the chlorinated hydrocarbons 1,1,2,2-tetrachoroethane and tetrachloroethylene caused a similar magnitude increase in membrane capacitance. The theory on membrane capacitance has been applied to deduce changes in membrane geometry caused by solvent partitioning. Although classical observations have shown that solvents increase the membrane capacitance per unit area of membrane, i.e., increase membrane thickness, the present results demonstrate that solvent partitioning predominantly leads to an increase in membrane surface area and to a lesser degree to an increase in membrane thickness. Moreover, the present results indicate that the physicochemical properties of each solvent are important determinants for its specific effects on membrane geometry. This implies that the hypothesis that solvent partitioning is associated with a common perturbation of membrane structure needs to be revisited and cannot account for the commonly observed narcotic effects of different organic solvents.

Batch process of polymer-enhanced ultrafiltration to recover mercury (II) from wastewater

The removal of mercury (II) from water by polymer-enhanced ultrafiltration (PEUF) was carried out using polyethylenimine (PEI), polyvinylamine (PVAm) and poly(acrylic acid) (PAA) as the metal-binding polymers. All three water-soluble polymers had strong interactions with mercury (II) in aqueous solutions, and a high mercury rejection was achieved with PEUF. At a given polymer dosage, the permeate flux followed the order of PVAm > PEI > PAA, presumably due to different physiochemical properties (e.g., viscosity and interfacial property) of the solution systems. Membrane fouling by PVAm and PEI in cross-flow mode was insignificant, but the flux decline due to fouling by PAA was not negligible. The batch operation of PEUF was modeled based on mass balance, and the applicability of the model equations was validated with experimental data. For a given system, the mercury content in the concentrated retentate, the mercury retention rate, the batch time and membrane area needed to achieve a desired separation task could be predicted if prior knowledge of concentration dependences of permeate flux and solute rejection were known. The effects of the amount of feed solution to be treated per unit membrane area on the separation performance of batch PEUF was analyzed.

Synthesis and characterization of high-performance novel thin film nanocomposite PRO membranes with tiered nanofiber support reinforced by functionalized carbon nanotubes

The pressure retarded osmosis (PRO) process is a novel technology which generates green electrical energy via semi-permeable membranes. However, a major challenge in the PRO system is the lack of suitable membranes with satisfactory power density (i.e., the power output per unit membrane area). In this study, we have successfully fabricated a novel thin-film composite (TFC) PRO membrane consisting of a tiered structure of polyetherimide (PEI) nanofibrous support reinforced by functionalized multi-walled carbon nanotubes (f-CNTs) and an ultrathin polyamide-based selective top skin layer. The tiered support was made by a fine and a coarse PEI nanofiber layers. The thin finer fiber reinforced with well dispersed f-CNTs has been found to increase mechanical stability of the polyamide selective layer, allowing the support to withstand high hydraulic pressure in the PRO system. Our optimized membrane can endure a trans-membrane pressure up to 24bar and generate a peak power density as high as 17.3W/m2 at 16.9bar using synthetic seawater brine (1.0M NaCl) as the draw solution against deionized (DI) water. In addition, the long term PRO result shows that this membrane can generate a stable power density of 15.0±0.5W/m2 for a test period of 10h. This demonstrates that our membrane holds great potential to be used in the PRO process.

Nanocomposite reverse electrodialysis (RED) ion-exchange membranes for salinity gradient power generation

Despite the important role of ion-exchange membranes (IEMs) in reverse electrodialysis (RED) systems, the current absence of proper ion-exchange membranes delays the sustainable development of the RED process for salinity gradient power generation. This research presents the preparation of a new type of organic–inorganic nanocomposite cation exchange membrane and its performance characteristics. The combination of functionalized iron (III) oxide (Fe2O3-SO42−) as an inorganic filler with the sulfonated poly (2,6-dimethyl-1,4-phenylene oxide) (sPPO) polymer matrix proved to have great potential for power generation by RED. The results showed that an optimal amount of Fe2O3-SO42− (0.5–0.7wt%) enhanced the key electrochemical properties of the ion-exchange membranes including a permselectivity up to 87.65% and an area resistance of 0.87Ωcm2. The nanocomposite membrane containing 0.7wt% (Fe2O3-SO42−) achieved a maximum power density (amount of power per unit membrane area) of 1.3Wm−2, which is relatively higher than that of the commercially available CSO (SelemionTM, Japan) membranes. The goal of the present work is to maximize the salinity gradient power generation by developing RED-specific nanocomposite IEMs. The results show the potential of the new design of the nanocomposite IEMs for viable energy generation by RED.

Performance-determining membrane properties in reverse electrodialysis

Ion exchange membranes are core elements in reverse electrodialysis (RED), a process that can generate electricity from salinity gradients. The electrochemical and physical properties of these membranes are RED performance-determining factors. Although several studies regarding the optimization and modeling of membrane properties for RED have been performed, conclusions based on real experimental data of the relationship between physicochemical membrane bulk properties and power density (power output per unit membrane area) are still lacking. In this work, we studied bulk membrane properties of both a series of commercially available membranes and tailor made membranes and correlated these to experimental RED performance data. We successfully constructed the RED stack completely built with tailor-made membranes, made of sulfonated polyetheretherketone (SPEEK) as a cation-exchanging material and polyepichlorohydrin (PECH) as an anion-exchanging material. We obtained the highest gross power density when using only tailor-made membranes because of their significantly reduced membrane resistance. Using the experimental data, we developed a model based on multiple linear regression for gross power density which provides a better understanding on the dominant performance-determining membrane properties in RED to generate power from salinity gradients. The results set the directions towards tailoring ion exchange membranes for RED applications and show that emphasis should be especially on the development of low resistance membranes, whereas further increase of the permselectivity only has a limited effect.

The influence of feed flow channel diameter on frictional pressure drop, membrane performance and process cost in full-scale tubular ceramic membranes

Tubular ceramic membranes with many, small-diameter feed flow channels have the advantage of being less costly per unit membrane area. For this reason, membranes with many small channels are often favored over those with fewer larger channels. We have theoretically studied how the diameter of the feed flow channels influences the frictional pressure drop, the membrane performance (flux and retention) and the process cost by performing basic pressure drop calculations and using experimental data from bench-scale experiments. The investigation was carried out on a model microfiltration process consisting of the separation of yeast cells from polyethylene glycol (PEG) macromolecules. For a membrane with 2.5mm channels the average flux and PEG retention were 112L/m2h and 22%, respectively, differing significantly from a membrane with 6.0mm channel diameter (131L/m2h, 17%), under the same hydrodynamic conditions. The choice of channel diameter also has a considerable impact on the process cost. While the costs were similar for membranes with 6.0 and 3.8mm diameter channels, they were about 55% higher using a membrane with 2.5mm channels. This high cost was mainly attributed to the high frictional pressure drop along the membrane, which increases the energy required for pumping.

Modeling of power generation from the mixing of simulated saline and freshwater with a reverse electrodialysis system: The effect of monovalent and multivalent ions

A reverse electrodialysis (RED) system utilizes the transport of cations and anions from controlled mixing of saline water (e.g., seawater) and freshwater (e.g., river water) through selective ion exchange membranes for power generation. Sodium chloride alone has been widely used to create power via salinity gradients in lab-scale RED systems. In an effort to simulate realistic salinity conditions in the natural water environment, in this study a new RED model was developed to quantify the power generation with coexisting monovalent and multivalent salt ions. The effects of different flow rate ratios (saline water flow, ØS, over freshwater flow, ØF) and intermembrane distance ratios on power density (amount of power per unit membrane area) were investigated. Our results indicated that magnesium sulfate, sodium sulfate, and magnesium chloride in the feed solutions of the RED system led to a 9–20% lower power density than when sodium chloride was the single ion source, largely because of the higher internal stack resistance of the multivalent ions. Higher power densities could be achieved with higher flow rates in the saline water compartment and shorter intermembrane distances in the freshwater compartment. For example, the power density increased by approximately 11% when the flow rate ratio was 5 compared with 1; similarly, an intermembrane distance ratio of 8 yielded an approximately 85% increase in power density compared with a ratio of 1. The goal of the present work is to advance our understanding of RED systems working in realistic salinity environments.

Substrate Stiffness Regulates Cellular Uptake of Nanoparticles

Nanoparticle (NP)-bioconjugates hold great promise for more sensitive disease diagnosis and more effective anticancer drug delivery compared with existing approaches. A critical aspect in both applications is cellular internalization of NPs, which is influenced by NP properties and cell surface mechanics. Despite considerable progress in optimization of the NP-bioconjugates for improved targeting, the role of substrate stiffness on cellular uptake has not been investigated. Using polyacrylamide (PA) hydrogels as model substrates with tunable stiffness, we quantified the relationship between substrate stiffness and cellular uptake of fluorescent NPs by bovine aortic endothelial cells (BAECs). We found that a stiffer substrate results in a higher total cellular uptake on a per cell basis, but a lower uptake per unit membrane area. To obtain a mechanistic understanding of the cellular uptake behavior, we developed a thermodynamic model that predicts that membrane spreading area and cell membrane tension are two key factors controlling cellular uptake of NPs, both of which are modulated by substrate stiffness. Our experimental and modeling results not only open up new avenues for engineering NP-based cancer cell targets for more effective in vivo delivery but also contribute an example of how the physical environment dictates cellular behavior and function.

Size Effects of Pore Density and Solute Size on Water Osmosis through Nanoporous Membrane

Understanding the behavior of osmotic transport across nanoporous membranes at molecular level is critical to their design and applications, and it is also beneficial to the comprehension of the mechanism of biological transmembrane transport processes. Pore density is an important parameter for nanoporous membranes. To better understand the influence of pore density on osmotic transport, we have performed systematic molecular dynamics simulations on water osmosis across nanoporous membranes with different pore densities (i.e., number of pores per unit area of membrane). The simulation results reveal that significant size effects occur when the pore density is so high that the center-to-center distance between neighboring nanopores is comparable to the solute size. The size effects are independent of the pore diameter and solute concentration. A simple quantitative correlation between pore density, solute size, and osmotic flux has been established. The results are excellently consistent with the theoretical predictions. It is also shown that solute hydration plays an important role in real osmotic processes. Solute hydration strengthens the size effects of pore density on osmotic processes due to the enlarged effective solute size induced by hydration. The influence of pore density, solute size, and solute hydration on water osmosis through nanoporous membranes can be introduced to eliminate the deviations of real osmotic processes from ideal behavior.

Sub-critical filtration conditions of commercial hollow-fibre membranes in a submerged anaerobic MBR (HF-SAnMBR) system: The effect of gas sparging intensity

A submerged anaerobic MBR demonstration plant with two commercial hollow-fibre ultrafiltration systems (PURON®, Koch Membrane Systems, PUR-PSH31) was operated using municipal wastewater at high levels of mixed liquor total solids (MLTS) (above 22gL−1). A modified flux-step method was applied to assess the critical flux (JC) at different gas sparging intensities. The results showed a linear dependency between JC and the specific gas demand per unit of membrane area (SGDm). JC ranged from 12 to 19LMH at SGDm values of between 0.17 and 0.5Nm3h−1m−2, which are quite low in comparison to aerobic MBR. Long-term trials showed that the membranes operated steadily at fluxes close to the estimated JC, which validates the JC obtained by this method. After operating the membrane for almost 2years at sub-critical levels, no irreversible fouling problems were detected, and therefore, no chemical cleaning was conducted.

The metabolic efficiency of myelinated vs unmyelinated axons

Understanding the metabolic efficiency of axons is of critical importance in neuroscience: such as interpreting fMRI and other imaging data, understanding the impact of metabolic conditions and anoxia/hypoxia on the CNS, and finally because current data suggests that metabolic cost places severe limits on neuronal activity[1]. Surprisingly, the metabolic cost of action potential (AP) in myelinated nerve fibers has not been directly estimated, unlike the cost of unmyelinated axons[1,2]. We calculated the metabolic cost of saltatory APs using detailed stochastic, biophysical models of a human myelinated peripheral axon and compared it to APs in unmyelinated axons of equal diameter. We modelled both axon types using the Modigliani stochastic simulator[3,4]. For the human myelinated axon, we modelled a heterogeneous multi-compartment cable of 3 cm length. Each Node of Ranvier is surrounded by paranodal regions and separated by a myelinated internode. Ion channel kinetics and axonal geometry were taken from published physiological and anatomical data[5]. Parameters for the unmyelinated axon were taken from[6]. We measured the metabolic cost of APs as the amount of ATP needed for Na-K-pumps to restore ion concentrations after an AP [1,2,8]. This allowed us to systematically investigate how metabolic cost depends on factors such as axonal geometry and ion channel densities. E.g comparing myelinated and unmyelinated axons with the same axon diameter of 1µm (fibre diameter including myelin sheath was 3.7 µm) we find the following: single APs at a myelinated axon’s Node of Ranvier have a metabolic cost of 3.5 pmol/cm² ATP per unit membrane area. This is approximately 7 times the amount per AP in hippocampal mossy fibre (0.53 pmol/cm2;[2]) but less than leaky squid axons (5 pmol/cm2). However, Node of Ranvier cover only 0.33% in our myelinated axon. The internodal regions contain hardly any Na+ channels, but a low density of K+ channels (3 µm-2) along internodes, and higher densities at the paranode (80 µm-2). We estimate overall energy consumption based on Na currents at the Node and K along a segment comprising half the internodal fibre on both sides of a node. This yields an AP cost per myelinated axon segment of 0.05 pmol/cm2 ATP per unit membrane area. Thus, per unit length the myelinated axon is 70 times metabolically cheaper than mossy fibers. The added bulk of the myelin allows 13 unmyelinated axons of same diameter to fit in the volume of one myelinated fibre, suggesting that the ratio of energy demand over wiring density is 5 times higher for myelinated fibers vs unmyelinated axons. Our findings are novel, as the costs of saltatory APs were not calculated from the bottom-up before. They are important, as it was generally assumed that myelinated axons evolved mainly for speed of propagation[7] at the cost of achievable wiring density[6,8], but energy may be as important: in cortical grey matter unmyelinated axons operate close to the noise limits to wiring miniaturisation[6], yet still contains myelinated axons[9]. We can explain this with a four-way trade-off between time delay, metabolic cost, volume constraints and noise limits to axonal anatomy.

Biochemical and functional correlates of an increased membrane density of caveolae in hypertrophic rat urinary bladder

Organ hypertrophy is often found to be associated with changes in the expression of caveolins and altered density of caveolae in the membrane. A plethora of signalling intermediaries are associated with caveolae and loss of caveolae has profound effects on contractility of the urinary bladder. We hypothesized that smooth muscle hypertrophy caused by bladder outflow obstruction (BOO) might lead to an altered caveola density with consequences for contractile regulation. Rat BOO for 6 weeks caused a 2.56-fold increase in the number of smooth muscle caveolae per μm membrane. No changes in the expression of caveolin-1 or cavin-1, normalized to β-actin were seen, but membrane area per unit muscle volume dropped to 0.346. Hypertrophy was associated with altered contraction in response to carbachol. The effect on contraction of cholesterol desorption, which disrupts lipid rafts and caveolae, was however not changed. Contraction in response to bradykinin resisted mβcd in control destrusor, but was inhibited by it after 6 weeks of obstruction. It is concluded that rat detrusor hypertrophy leads to an increased number of caveolae per unit membrane area. This change is due to a reduction of membrane area per volume muscle and it does not play a role for cholinergic activation, but promotes contraction in response to bradykinin after long-term obstruction.

A feasibility study of pressure‐retarded osmosis power generation system based on measuring permeation volume using reverse osmosis membrane

AbstractA pressure‐retarded osmosis (PRO) power generation system is a hydroelectric power system which utilizes permeation flow through a semipermeable membrane. Permeation flow is generated by the potential energy of the salinity difference between sea water and fresh water. Since the cost of the membrane is high, the permeation performance of the membrane must be improved in order to realize PRO systems. We have investigated reverse osmosis (RO) membrane products as semipermeable membranes and measured the permeation volume of a few products. The generation power per unit membrane area calculated from the permeation volume is about 0.62 W/m2. But as a result of our improvements (greater salt water volume, spacers for fresh water channel with the function of discharging concentrated salinity, extralow‐pressure type of membrane, washing the support layer of membrane when the generation power falls by half) the generated power may be 2.43 W/m2. Then the power system cost would be about 4.1 million yen/kW. In addition, if the support layer of the membrane is made thinner and a PRO system is applied to equipment where pumping power for another purpose is available (wastewater treatment plants located at the seaside, thermal and nuclear power plants, sea water desalination plants), the generated power may be increased. These improvements may enable PRO systems to be realized at a cost close to that of photovoltaic power systems. 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 173(2): 8–20, 2010; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/eej.21000

Evaluation of intermittent air sparging in an anoxic denitrification membrane bioreactor

The impact of intermittent air sparging on the operation of an anoxic (dissolved oxygen <0.1 mg l(-1)) immersed membrane bioreactor (iMBR) applied to potable water denitrification is discussed. Air sparge length and specific aeration demand per unit membrane area (SAD(m)) were varied to determine impact on oxygen transfer and membrane fouling. For SAD(m)>0.39 m(3) m(-2) h(-1) with sparge lengths of 10 to 60 seconds, a low dissolved oxygen residual of 0.05 to 0.90 mg O(2) l(-1) was formed which typically inhibited denitrification; oxygen transfer efficiency increased with increasing sparge time. Residual oxygen was rapidly consumed at a rate, r(O(2)), of 0.35 mg O(2) l(-1) min(-1). Once oxygen was depleted, denitrification proceeded. When intermittently sparging at a SAD(m)<0.39 m(3) m(-2) h(-1) for 30 seconds (following 10 minute dead-end filtration cycles in the iMBR), no dissolved oxygen residual was observed and a flux of 21 l m(-2) h(-1) was sustained with fouling rates <0.001 m bar min(-1) recorded. This method provides for effective integration of air sparging into anoxic/anaerobic iMBR environments to simplify process design and delivers a tangible reduction in specific energy demand from 0.19 kWh m(-3) (for constant sparging) to 0.007 kWh m(-3).

Towards spacer free electrodialysis

In electrodialysis (ED) processes, the operating current density is limited by concentration polarisation. However, in order to get the maximum ion flux per unit membrane area it is desirable to operate at the highest possible current density. The fluid flow in ED modules mainly takes place in flat channels with rectangular cross-sections, where the membranes form the walls and the channels are filled with spacer material. The spacer design itself has great effect on the process costs and has been investigated intensively in recent years. Another way of promoting turbulence in the channel is by using air sparging. This work in fact shows the impact of air sparging on the ED process. The influence of the gas/liquid ratio in combination with various spacer configurations is discussed and compared with the situation where no feed spacer is present at all. This comparison clearly shows that the mass transfer increase is most effective in a spacer free cell where the mass transfer increases linearly with increasing G/L ratio. Of all cases studied here, the spacer free cell combines the highest mass transfer increase with the lowest increase in cell resistance.

Immobilization of lipase by ultrafiltration and cross-linking onto the polysulfone membrane surface

In this study, a biphasic enzymatic membrane reactor was made by immobilizing Candida Rugosa lipase onto the dense surface of polysulfone ultrafiltration membrane by filtration and then cross-linking with glutaraldehyde solution. The reactor was further applied for the hydrolysis of olive oil, the performance of which was evaluated in respect of apparent reaction rate based on the amount of fatty acids extracted into the aqueous phase per minute and per membrane surface. It was found that the ultrafiltration and cross-linking process greatly improved the reaction rate per unit membrane area and the enzyme lifetime. The highest reaction rate reached 0.089 μmol FFA/min cm 2 when the enzyme loading density was 0.098 mg/cm 2. The results also indicated that the performance of lipase immobilized on the membrane surface was superior to that immobilized in the pores, and the apparent reaction rate and stability of immobilized lipases were improved greatly after cross-linking. It suggested that immobilization of enzymes by filtration and then cross-linking the enzymes onto the membrane surface is a simple and convenient way to prepare a high-activity immobilized enzyme membrane.