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Ultrafiltration

Ultrafiltration is a pressure-driven filtration separation occurring on a molecular scale (see Dialysis Filtration Hollow-fibermembranes Membrane TECHNOLOGY REVERSE osMOSis). Typically, a liquid including small dissolved molecules is forced through a porous membrane. Large dissolved molecules, coUoids, and suspended soHds that caimot pass through the pores are retained. [Pg.293]

Ultrafiltration separations range from ca 1 to 100 nm. Above ca 50 nm, the process is often known as microfiltration. Transport through ultrafiltration and microfiltration membranes is described by pore-flow models. Below ca 2 nm, interactions between the membrane material and the solute and solvent become significant. That process, called reverse osmosis or hyperfiltration, is best described by solution—diffusion mechanisms. [Pg.293]

Membrane-retained components are collectively called concentrate or retentate. Materials permeating the membrane are called filtrate, ultrafiltrate, or permeate. It is the objective of ultrafiltration to recover or concentrate particular species in the retentate (eg, latex concentration, pigment recovery, protein recovery from cheese and casein wheys, and concentration of proteins for biopharmaceuticals) or to produce a purified permeate (eg, sewage treatment, production of sterile water or antibiotics, etc). Diafiltration is a specific ultrafiltration process in which the retentate is further purified or the permeable sohds are extracted further by the addition of water or, in the case of proteins, buffer to the retentate. [Pg.293]

Membrane filtration has been used in the laboratory for over a century. The earliest membranes were homogeneous stmctures of purified coUagen or 2ein. The first synthetic membranes were nitrocellulose (collodion) cast from ether in the 1850s. By the early 1900s, standard graded nitrocellulose membranes were commercially available (1). Their utihty was limited to laboratory research because of low transport rates and susceptibiUty to internal plugging. They did, however, serve a useflil role in the separation and purification of coUoids, proteins, blood sera, enzymes, toxins, bacteria, and vimses (2). [Pg.293]

The subsequent improvement of the physical and chemical characteristics of these membranes, their incorporation into machines, and the development of procedures to prevent or clean surface-fouling films were the principal areas of significant advancement. By 1990, the industrial ultrafiltration market had grown to an estimated (90-100) x 10 .  [Pg.293]

Ultrafiltration or gel filtration can be used instead of dialysis to de-salt solutions, or change buffer conditions. These techniques have the advantage of increased speed, but the disadvantage of being less straightforward and needing more complex equipment. [Pg.63]

Equilibrium dialysis is an analytical technique which is usually performed with commercial apparatus. In this technique, the two dialysis chambers, separated by a membrane, are filled respectively with macromolecule solution and with ligand, which is usually radioactively labelled. After equilibrium has been reached, samples are removed from the two chambers the concentration of free ligand is determined from one sample, and free plus bound ligand from the other. Parameters characterising the binding equilibrium can be determined by appropriate analysis of the data. [Pg.63]

This apparatus can be used not only for concentrating, but also for dialysis in this case, after an intial concentration, the chamber is filled with buffer and the ultrafiltration process repeated. [Pg.65]

The main application of ultrafiltration is in concentrating solutions, but it can also be used for de-salting and changing buffers, and for quantitative studies of binding equilibria between macromolecules and their ligands. [Pg.66]

Ausubel, F.M., Brent, R., Kingston, R.E., Moore, D.D., Seidman, J.G., Struhl, K. (1989) Current Protocols in Molecular Biology. John Wiley Sons, New York. [Pg.67]

Ultrafiltration is used to separate and concentrate various protein types from foodstuffs, such as whey protein from cheese manufacture, egg albumen, and blood plasma proteins (Porter and Michaels, 1970). Ultrafiltration achieves separation by the use of a semi-permeable membrane. The process is carried out under hydraulic pressure. [Pg.49]

Most membranes for use in food applications are plastic anisotropic membranes, which are highly permeable to water but capable of retaining very small solute particles. As the pore size of the membrane is reduced it is possible to separate solutes on the basis of molecular dimensions. Solvent and very small solute particles pass through the membrane and are collected the larger solutes are retained on the membrane surface. [Pg.49]

The major advantages of ultrafiltration are that it is non-destructive, no chemicals are required, and it is possible to carry out separation at low [Pg.49]

Ultrafiltration provides a suitable alternative to conventional drying techniques, such as spray drying, in some applications and is ideally suited to materials with high solids contents (Bhave et al., 1992). Applications in the food industry include the concentration of pasteurised skimmed milk and whole milk. The advantages of osmotic methods when compared with conventional drying techniques are that there is no flavour loss or heat deterioration as with heating methods (Ishikawa and Nara, 1992). [Pg.50]

The applications of ultrafiltration in producing animal-derived ingredients currently centre on the production of plasma protein concentrates. It is also used to separate red blood cells from plasma. Further applications in the refining of animal products include the concentration and de-ashing of gelatin. Ultrafiltration is also used for the treatment of blood and animal waste (Cheryan, 1992). [Pg.50]

Ultrafiltration techniques [293-295] have been used to separate surfactant monomers from their micelles. Asakawa et al. [296] used the ultrafiltration [Pg.426]

It is perhaps needless to state that surface tension is the most important physical property of a surfactant to be determined. Methods for surface and interfacial tension measurement have been the subject of numerous papers and review articles [298-314]. [Pg.427]

In spite of the apparent simplicity of surface tension measurement, correct and reproducible values are not always readily obtainable. In addition to the specific limitations of each technique, the time dependence of surface tension of surfactant solutions can be a major complication. Surface tension depends on the [Pg.427]

Surface tension methods measure either static or dynamic surface tension. Static methods measure surface tension at equilibrium, if sufficient time is allowed for the measurement, and characterize the system. Dynamic surface tension methods provide information on adsorption kinetics of surfactants at the air-liquid interface or at a liquid-liquid interface. Dynamic surface tension can be measured in a timescale ranging from a few milliseconds to several minutes [315]. However, a demarkation line between static and dynamic methods is not very sharp because surfactant adsorption kinetics can also affect the results obtained by static methods. It has been argued [316] that in many industrial processes, sufficient time is not available for the surfactant molecules to attain equilibrium. In such situations, dynamic surface tension, dependent on the rate of interface formation, is more meaningful than the equilibrium surface tension. For example, peaked alcohol ethoxylates, because they are more water soluble, do not lower surface tension under static conditions as much as the conventional alcohol ethoxylates. Under dynamic conditions, however, peaked ethoxylates are equally or more effective than conventional ethoxylates in lowering surface tension [317]. [Pg.428]

Most techniques stretch the liquid-air surface at the moment of measurement. For example, the drop weight method [318] and the ring method [319-322] stretch the surface during detachment. However, instruments are now available which measure surface tension without detaching the ring from the liquid (e.g., the Ki-iiss Tensiometer K12). [Pg.428]

Recovery of proteins from ultrafiltration depends not only on the size, but also on the solute composition and the type of membrane, since unspecific adsorption of the protein to the membrane cannot be excluded. Furthermore, the chemical resistance of the membrane to buffer components and sanitation ingredients should be taken into consideration. [Pg.127]

Unspecific adsorption of proteins maybe decreased if the membrane is preincubated with 5% Tween 20 (w/v) for 1 h and subsequently washed with ddH20. [Pg.127]

Desalting is also possible by ultrafiltration. For this purpose, the sample is concentrated to about 10% of its volume, reconstituted to its original volume with water or a second buffer, and ultrafiltration is repeated twice in the same way. Proteins are less likely to be denatured, because ultrafiltration is a mechanical separation which does not need harsh chemicals for separation. [Pg.127]

This section discusses the ultrafiltration, microwave-assisted, and ultrasound-assisted extraction techniques. [Pg.142]

Ultrafiltration (UF) is used primarily to separate analytes of interest from macromolecules, such as proteins, peptides, lipids, and sugars, which may interfere with analyses, particularly affecting ionization in mass spectrometry. In residue analysis, molecular weight cut-off devices or spin filters coupled to microcentrifuge tubes are the most commonly used formats. Alternative formats such as the [Pg.142]

96-well plate are also available, but require dedicated vacuum manifolds and pumps. All residue applications use centrifugal devices. [Pg.142]

Goto et al. described a simple, rapid, and simultaneous analysis method for oxytetracycline, tetracycline, chlortetracycline, penicillin G, ampicillin, and nafcillin in meat using electrospray ionization tandem mass spectrometry. The samples were homogenized with water followed by a centrifugal ultrafiltration after addition of internal standards (demeclocycline, penicillin G-ds, ampicillin-fi 5, and [Pg.142]

Other examples of applications include sulfonamides in milk ° eggs plasma edible tissues tetracyclines in egg penicillin G in muscle, kidney, and liver and spiramycin (a macrolide) in egg and chicken muscle. [Pg.142]

In the following section, film and gel-polarisation models are developed for ultrafiltration. These models are also widely applied to cross-flow microfiltration, although even these cannot be simply applied, and there is at present no generally accepted mathematical description of the process. [Pg.446]

Here solute concentrations C and Cp in the permeate are expressed as mass fractions, D is the diffusion coefficient of the solute and y is the distance from the membrane. Rearranging and integrating from C = C/ when y = / the thickness of the film, to C = Cw, the concentration of solute at the membrane wall, when y = 0, gives  [Pg.447]

If it is further assumed that the membrane completely rejects the solute, that is, and Cp = 0, then  [Pg.447]

The mass transfer coefficient is usually obtained from correlations for flow in non-porous ducts. One case is that of laminar flow in channels of circular cross-section where the parabolic velocity profile is assumed to be developed at the channel entrance. Here the solution of LfivfiQUE(7), discussed by Blatt et al.(H , is most widely used. This takes the form  [Pg.447]

For the case of turbulent flow the Dittus-Boelter(9) correlation given in Volume 1, Chapters 9 and 10, is used  [Pg.447]

The procedure used for the industrial production of acid (isoelectric) casein is essentially the same as that used on a laboratory scale, except for many technological differences (section 4.15.1).The whey proteins may be recovered from the whey by salting out, dialysis or ultrafiltration. [Pg.153]

Because they occur as large aggregates, micelles, most (90-95%) of the casein in milk is sedimented by centrifugation at 100 000 g for 1 h. Sedimentation is more complete at higher (30 37°C) than at low (2°C) temperature, at which some of the casein components dissociate from the micelles and are non-sedimentable. Casein prepared by centrifugation contains its original level of colloidal calcium phosphate and can be redispersed as micelles with properties essentially similar to the original micelles. [Pg.153]

Addition of CaCl2 to about 0.2 M causes aggregation of the casein such that it can be readily removed by low-speed centrifugation. If calcium is added at 90°C, the casein forms coarse aggregates which precipitate readily. This principle is used in the commercial production of some casein co-precipitates in which the whey proteins, denatured on heating milk at 90°C for 10 min, co-precipitate with the casein. Such products have a very high ash content. [Pg.153]

Casein can be precipitated from solution by any of several salts. Addition of (NHJ SO to milk to a concentration of 260 g 1 causes complete precipitation of the casein together with some whey proteins (immunoglobulins, Ig). MgS04 may also be used. Saturation of milk with NaCl at 37°C precipitates the casein and Igs while the major whey proteins remain soluble, provided they are undenatured. This characteristic is the basis of a commercial test used for the heat classification of milk powders which contain variable levels of denatured whey proteins. [Pg.153]

The casein micelles are retained by fine-pore filters. Filtration through large-pore ceramic membranes is used to purify and concentrate casein on a laboratory scale. Ultrafiltration (UF) membranes retain both the caseins [Pg.153]

Filtration is another common method to separate solid particles dispersed in a liquid. The simplest case is filter paper, although mostly polymer-based filter membranes are used. The most important quality of filters is the size (diameter) of the particles filtered out, corresponding to the pore size of the filter. In the case of ultrafiltration, macromolecules can be filtered out—this is discussed in Section 2.4. Filters come in various sizes, depending on the quantity of sample to be analyzed. They may be incorporated into the tips of pipettes, which make it easy to remove small solid particles from a solution, for example, before injecting it onto a chromatographic column. [Pg.42]

Probably the simplest way to separate proteins from small molecules is protein precipitation. It is needed for studying low-molecular-weight compounds (MW below 2-5 kDa), as the presence of macromolecules typically deteriorates analytical performance. In chromatography they lift the baseline, cause noise, and may even ruin chromatographic columns. In MS, they deteriorate ionization and may block the ion source. [Pg.42]

Ulfrafiltration is another common way of separating small and large molecules (e.g., sodium vs. albumin). The liquid sample is dispensed into an ulfrafiltration [Pg.42]

The most important characteristic of an ultrafiltration tube is its MW cutoff value, usually expressed in kilodaltons. A tube with 10 kDa cutoff retains the molecules with molecular mass higher than approximately 10 kDa. This cutoff value is not very accurate in the present example, a small fraction of compounds with 5-10 kDa may be retained, while some of 15-20 kDa may pass through the filter. There are various filters, with cutoff values in the range 3-100 kDa. [Pg.43]

As discussed previously, the technique of microfiltration is effectively utilized to remove whole cells or cell debris from solution. Membrane filters employed in the microfiltration process generally have pore diameters ranging from 0.1 to 10 pm. Such pores, while retaining whole cells and large particulate matter, fail to retain most macromolecular components, such as proteins. In the case of ultrafiltration membranes, pore diameters normally range from 1 to 20 nm. These pores are sufficiently small to retain proteins of low molecular mass. Ultrafiltration membranes with molecular mass cut-off points ranging from 1 to 300 kDa are commercially available. Membranes with molecular mass cut-off points of 3,10, 30, 50, and 100 kDa are most commonly used. [Pg.137]

Traditionally, ultrafilters have been manufactured from cellulose acetate or cellulose nitrate. Several other materials, such as polyvinyl chloride and polycarbonate, are now also used in membrane manufacture. Such plastic-type membranes exhibit enhanced chemical and physical stability when compared with cellulose-based ultrafiltration membranes. An important prerequisite in manufacturing ultrafilters is that the material utilized exhibits low protein adsorptive properties. [Pg.137]

Ultrafiltration has become prominent as a method of protein concentration for a variety of reasons  [Pg.139]

One drawback relating to this filtration technique is its susceptibility to rapid membrane clogging. Viscous solutions also lead to rapid decreases in flow rates and prolonged processing times. [Pg.139]

The driving potential for UF - that is, the filtration of large molecules - is the hydraulic pressure difference. Because of the large molecular weights, and hence the low molar concentrations of solutes, the effect of osmotic pressure is usually minimal in UF this subject is discussed in Section 8.5. [Pg.136]

if experiments are performed with solutions of various concentrations C and at a given liquid velocity along the membrane (i.e., at one /cp value), and the experimental values of /p are plotted against log C on a semi-log paper, then a straight line with a slope of -/cp should be obtained. In addition, it is seen that such straight lines should intersect the abscissa at Cq, because ln(CQ/C) is zero where C = Cq. If such experiments are performed at various liquid velocities, then /fp could be correlated with the liquid velocity and other variables. [Pg.137]

The following empirical dimensional equation [5], which is based on data for the UF of diluted blood plasma, can correlate the filtrate flux/p (cm min ) averaged over the hollow fiber of length/, (cm)  [Pg.138]

The shear rate (s ) at the membrane surface is given by = 9ivld (cf. Example 2.2), where v is the average linear velocity (cm s ), d is the fiber inside diameter (cm), and Dp is the molecular diffusion coefficient (cm s ) all other symbols are as in Equation 8.4. Hence, Equation 8.6 is most likely applicable to UF in hollow-fiber membranes in general. [Pg.138]

Cellulose acetate Acetone, dioxan, DMAc, DMF, DMSO, THF Around 135 3-7 [Pg.35]

Regenerated cellulose Stable in most organic solvents (typically prepared from cellulose acetate as precursor) High crystalline content 4-9 [Pg.35]

Adopted from the state-of-the-art in RO, TFC membranes have become increasingly interesting for UF as well. One of the first examples of a commercial membrane of this type is composed of a thin barrier layer from regenerated cellulose on a porous polyolefine support [32]. Significant increase in selectivity in protein UF via electrostatic exclusion in addition to size exclusion has been achieved by introducing fixed charges into the barrier layer of a cellulose-based TFC membrane [33]. [Pg.35]

Similar to developments in NF and RO, solvent-resistant U F membranes could be the basis for a wide range of novel applications. Cross-linked integrally anisotropic membranes are explored with particular emphasis, and a very promising example are membranes made from poly(acrylonitrile-co-glycidyl methacrylate) that after NIPS had been cross-linked with ammonia or other tri- or difunctional amines [34], [Pg.36]

Mahmood J (2000) Interspecies Scaling Role of Protein Binding in the Prediction of Clearance from Animals to Humans. J Clin Pharmacol 40 1439-1446 [Pg.477]

Oravcova J, Bohs B, Lindner W (1995) Drug-protein studies New trends in analytical and experimental methodology. Journal of Chromatography 677 1-28 Pacifici GM, Viani A (1992) Methods of Determining Plasma and Tissue Binding of Drugs. Clin Pharmacokinet 23(6) 449-468 [Pg.477]

Pang KS, Rowland M (1977) Hepatic clearance of drugs. I. Theoretical consideration of a well-stirred model and a parallel tube model Influence of hepatic blood flow, plasma and blood cell binding, and to the hepatocellular enzymatic activity on hepatic drug clearance. J Pharmacokinet Bio-pharm 5 625-653 [Pg.477]

Rolan PE (1994) Plasma protein binding displacement interactions - why are they still regarded as clinically important Br J Clin Pharmac 37 125-128 [Pg.477]

Rosenthal AE (1967) A graphic method for the determination and presentation of binding parameters in a complex system. Analytical Biochemistry 20 525-532 Sansom LN, Evans AM (1995) What is the True Clinical Significance of Plasma Protein Binding Displacement Interactions Drug Safety 12(4) 227—233 Scatchard G (1949) The attractions of protein for small molecules and ions. New York Academic of Sciences 51 660-692 [Pg.477]

The first membrane separation was performed with nitrocellulose in 1855. During the following 100 years, the technology played a limited role as a research tool in analytical chemistry. A major breakthrough occurred in 1958-1961 when the anisotropic or asymmetric membrane was developed. While membranes employed previously were uniform throughout, the upper portion of anisotropic membranes represents only 1% of the total film and is the actual filter, the other 99% acting as a support. The thinness of the membrane and the very fine pore structure promote excellent throughput for UF. [Pg.518]

Springer Series in Wood Science Methods in Lignin Chemistry (Edited by S.Y. Lin and C.W. Dence) [Pg.518]

The term molecular weight cutoff (MWCO) is used to describe separation capabilities. If a membrane has a nominal MWCO of 10000, at least 90% of the soluble macomolecules that have a molecular weight of 10000 or more will be rejected by the membrane. [Pg.519]

The amount of material that will pass through a given area of UF membrane in a given period is commonly called membrane flux, which may be expressed by the equation [Pg.519]

Factors such as concentration polarization, shear rate, and temperature also have a pronounced effect on UF performance. In general, high shear rate and temperature tend to increase membrane flux. In contrast, high concentration and low flow rate reduce the flux. For more details of UF as a separation process, see Klinkowski (1978), and Claussen (1978), Lonsdale (1982), Woerner and McCarthy (1986). [Pg.519]

UF usually is applied to aqueous streams which may contain soluble macromolecules, colloids, salts, augers, and so on. It is used to concentrate or fractionate, often simultaneously. [Pg.826]

Flux (J) is ibe measure of a membrane s productivity SI units for flux, jim/s, are convanible into more convantkmal units by multiplying by 3.60 to obtain L/m2-h or by 2.12 to obtain U,S. gel/ft -dey [Pg.826]

Permeate is the melenal that has passed throngh the membrane. [Pg.826]

Retention, also callnd rejection or reflection, is defined as [Pg.826]

Retention ignores the phenomenon of concentration polarization, which generally increnses significantly the true concentration of the retained species at the membmae surface (Fig. IS. 1-1). [Pg.826]

UF only became popular in water treatment very recendy, primarily because of its ability to remove viruses. The first plant was constructed in 1988 (Aptel (1995)). Since then, UF has been widely installed and unit costs have been reduced, with many large scale suppliers available (Do) en (1997)). [Pg.86]

An NF pilot plant was operated with a MF pretreatment to remove THMPs from highly organic groundwater. The 100 (AgL THM standard was easily achieved. This process was compared to other options such as oxidant substitution, coagulant, and GAC. No other process could compete with ultra-low pressure NF (Watson and Homburg (1989)). [Pg.86]

NF and low MWCO UF were compared for colour removal and both proved to be efficient (AreniUas et al (1995)). NF was able to remove 95% of chlorinated organic compounds from pulp and paper [Pg.86]

NF was found to be a very good treatment for a groundwater high in sulphates, hardness, and sodium, although the concentrate disposal was a problem (Dard et al. (1995)). [Pg.87]

Different treatment processes, such as coagulation and sand filtration, oxidation, NF, granular activated carbon, and biologically activated carbon were compared by Legube et al. (1995). [Pg.87]

Permeate is the material that has passed through the membrane. [Pg.826]

As discussed above, UF membranes have smaller pores than MF membranes indicating that their rejection of suspended solids and bacteria are greater or tighter and that for MF. For example, the California Department of Public Health gives UF membranes a 4-log removal credit [Pg.387]

See reference 1 and 6-8 for more detailed discussions about ultrafiltration. [Pg.388]

Heavy metals Toxicities USA Thailand Hong Kong [Pg.59]

Copper (II) Liver damage, insomnia, Wilson disease 0.25 2.00 0.05-0.1 [Pg.59]

Nickel (II) Nausea, chronic asthma, coughing, dermatitis 0.20 1.00 0.10-0.20 [Pg.59]

Microza Research Development Department, Specialty Products Systems R D Center, Asahi Kasei Chemicals Corporation, Fuji City, Shizuoka, 416-8501 Japan [Pg.101]

1 Overview and Major Trends in Microfilter/Ultrafilter Technology [Pg.101]

Target to be separated is scarcely denatured or decomposed due to separation under nuld conditions. [Pg.101]

Therefore, since Loeb and Sourirajan innovated an industrially usable filtration membrane having a low permeation resistanee in 1960, the filtration separation using a membrane has been used in various industrial fields around the world, sueh as the automobile industry (closed system for recovery of eleetrodeposition paint), the eleetronies industry (produelion of ultrapure water for semiconduetor production), and the pharmaceutieal industry (eoneen-tration and purification of enzymes and antibiotics, production of pyrogen-free water, etc). [Pg.101]

Advanced Membrane Technology and Applications. Edited by Norman N. Li, Anthony G. Fane, W. S. Winston Ho, and T. Matsuura Copyright 2008 John Wiley Sons, Inc. [Pg.101]


Ultrafiltration. Ultrafiltration was described under pretreatment methods. It is used to remove finely divided suspended solids, and when used as a tertiary treatment, it can remove virtually all the BOD remaining after secondary treatment. [Pg.319]

The mechanism of ultrafiltration is not simply a sieve effect, but depends also upon the electrical conditions of both the membrane and the colloid. [Pg.411]

Surface active electrolytes produce charged micelles whose effective charge can be measured by electrophoretic mobility [117,156]. The net charge is lower than the degree of aggregation, however, since some of the counterions remain associated with the micelle, presumably as part of a Stem layer (see Section V-3) [157]. Combination of self-diffusion with electrophoretic mobility measurements indicates that a typical micelle of a univalent surfactant contains about 1(X) monomer units and carries a net charge of 50-70. Additional colloidal characterization techniques are applicable to micelles such as ultrafiltration [158]. [Pg.481]

Finally, micellar systems are useful in separation methods. Micelles may bind heavy-metal ions, or, through solubilization, organic impurities. Ultrafiltration, chromatography, or solvent extraction may then be used to separate out such contaminants [220-222]. [Pg.484]

Partition coefficients are usually determined using ultrafiltration" or NMR" or UV-vis ... [Pg.129]

Table 1. Removal of Viral Particles from Fluids by Ultrafiltration... Table 1. Removal of Viral Particles from Fluids by Ultrafiltration...
Acrylonitrile fibers treated with hydroxides have been reported to be useful for adsorption of uranium from seawater (105). Tubular fibers for reverse osmosis gas separations, ion exchange, ultrafiltration, and dialysis are a significant new appHcation of acryUc fibers and other synthetics. Commercial acryUc fibers have already been developed by Nippon Zeon, Asahi, and Rhc ne-Poulenc. [Pg.286]

The axial filter (Oak Ridge National Laboratory) (30) is remarkably similar to the dynamic filter in that both the rotating filter element and the outer shell are also cylindrical. An ultrafiltration module based on the same principle has also been described (31). Unlike the disk-type European dynamic filters described above, the cylindrical element models are not so suitable for scale-up because they utilize the space inside the pressure vessel poorly. [Pg.410]

Cross-Flow Filtration in Porous Pipes. Another way of limiting cake growth is to pump the slurry through porous pipes at high velocities of the order of thousands of times the filtration velocity through the walls of the pipes. This is ia direct analogy with the now weU-estabHshed process of ultrafiltration which itself borders on reverse osmosis at the molecular level. The three processes are closely related yet different ia many respects. [Pg.412]

The idea of ultrafiltration has been extended ia recent years to the filtration of particles ia the micrometer and submicrometer range ia porous pipes, usiag the same cross-flow principle. In order to prevent blocking, thicker flow channels are necessary, almost exclusively ia the form of tubes. The process is often called cross-flow microfiltration but the term cross-flow filtration is used here. [Pg.412]

PVDF-based microporous filters are in use at wineries, dairies, and electrocoating plants, as well as in water purification, biochemistry, and medical devices. Recently developed nanoselective filtration using PVDF membranes is 10 times more effective than conventional ultrafiltration (UF) for removing vimses from protein products of human or animal cell fermentations (218). PVDF protein-sequencing membranes are suitable for electroblotting procedures in protein research, or for analyzing the phosphoamino content in proteins under acidic and basic conditions or in solvents (219). [Pg.389]

K. marxianus var. fragilis which utilizes lactose, produces a food-giade yeast product from cheese whey or cheese whey permeates collected from ultrafiltration processes at cheese plants. Again, the process is similar to that used with C. utilis (2,63). The Provesteen process can produce fragiUs yeast from cheese whey or cheese whey permeate at cell concentrations ia the range of 110—120 g/L, dry wt basis (70,73). [Pg.467]

Pish protein concentrate and soy protein concentrate have been used to prepare a low phenylalanine, high tyrosine peptide for use with phenylketonuria patients (150). The process includes pepsin hydrolysis at pH 1.5 ptonase hydrolysis at pH 6.5 to Hberate aromatic amino acids gel filtration on Sephadex G-15 to remove aromatic amino acids incubation with papain and ethyl esters of L-tyrosine and L-tryptophan, ie, plastein synthesis and ultrafiltration (qv). The plastein has a bland taste and odor and does not contain free amino acids. Yields of 69.3 and 60.9% from PPG and soy protein concentrate, respectively, have been attained. [Pg.471]


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