Filtration ultrafiltration

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. 

Mechanism-based inactivation results in formation of a covalent adduct between the active inhibitor and the enzyme, or between the active inhibitor and a substrate or cofactor molecule. If the mechanism involves covalent modification of the enzyme, then one should not be able to demonstrate a recovery of enzymatic activity after dialysis, gel filtration, ultrafiltration, or large dilution, as described in Chapters 5 to 7. Additionally, if the inactivation is covalent, denaturation of the enzyme should fail to release the inhibitory molecule into solution. If a radiolabeled version of the inactivator is available, one should be able to demonstrate irreversible association of radioactivity with the enzyme molecule even after denaturation and separation by gel filtration, and so on. In favorable cases one should likewise be able to demonstrate covalent association of the inhibitor with the enzyme by a combination of tryptic digestion and LC/MS methods. 

Koyuncu et al. [56] presented pilot-scale studies on the treatment of pulp and paper mill effluents using two-stage membrane filtrations, ultrafiltration and reverse osmosis [56]. The combination of UF and RO resulted in very high removals of COD, color, and conductivity from the effluents. At the end of a single pass with seawater membrane, the initial COD, color and conductivity values were reduced to 10-20 mg/L, 0-100 PCCU (platinum cobalt color units) and 200-300 ps/cm, respectively. Nearly complete color removals were achieved in the RO experiments with seawater membranes. 

Whey protein concentrates (WPC), which are relatively new forms of milk protein products available for emulsification uses, have also been studied (4,28,29). WPC products prepared by gel filtration, ultrafiltration, metaphosphate precipitation and carboxymethyl cellulose precipitation all exhibited inferior emulsification properties compared to caseinate, both in model systems and in a simulated whipped topping formulation (2. However, additional work is proceeding on this topic and it is expected that WPC will be found to be capable of providing reasonable functionality in the emulsification area, especially if proper processing conditions are followed to minimize protein denaturation during their production. Such adverse effects on the functionality of WPC are undoubtedly due to their Irreversible interaction during heating processes which impair their ability to dissociate and unfold at the emulsion interface in order to function as an emulsifier (22). 

Membrane-re tamed components are collectively called concentrate or retentate. Materials permeating the membrane are called filtrate, ultrafiltrate, or permeate. 

Part 1(1956), 542-8, 563-606, 655 718-23 (Centrifuges and centrifuge filtration ultrafiltration) Ibid, Vol 1, Pt 1(1959), 224-7 (Centrifugal sedimentation), 226-7(Ultracentri-fuges) 348-9(Centrifugal filtration) Ibid,... 

Techniques can be classified into two main categories those that detect total metal concentrations and those that detect some operationally defined fraction of the total. Methods which detect total concentrations such as inductively coupled plasma spectrometry, neutron activation analysis, atomic absorption spectrometry and atomic emission spectrometry have no inherent speciation capabilities and must be combined with some other separation technique(s) to allow different species to be detected (approach A in Fig. 8.2). Such separation methods normally fractionate a sample on the basis of size, e.g. filtration/ultrafiltration, gel filtration, or a combination of size and charge, e.g. dialysis, ion exchange and solvent extraction (De Vitre et al., 1987 Badey, 1989b Berggren, 1989 1990 Buffle et al., 1992). In all instances the complexes studied must be relatively inert so that their concentrations are not appreciably modified during the fractionation procedure. 

F(=) Elutriation Countercurrent electrophoresis Filtration Ultrafiltration Reverse osmosis Pressure dialysis Zone melting Electrofiltration... 

This invention relates to methods of preparing inulin from milled Jerusalem artichoke tubers by crystallization and drying. Water-soluble substances are separated from water-insoluble fibrous components. Following heating (80 to 85°C for 1 to 3 min), filtration, ultrafiltration, and nanofiltration steps remove protein and colored substances. The inulin is crystallized from the concentrated juice. 

Normal urine frequently contains a variety of low-molecular weight substances (urea is a notable example) that can inhibit the enzymes of interest The toxicant may also act as an inhibitor. These substances usually can be removed by dialysis, dilution, Sephadex filtration, ultrafiltration or gel filtration... 

At harvest, the benzylpenicillin is in solution extra-cellularly, together with a range of other metabolites and medium constituents. The first step in downstream processing is to separate the cells from the liquid broth by techniques such as filtration, ultrafiltration or centrifugation. This stage is carried out under conditions that avoid contamination with P-lactamase-producing microorganisms which could lead to serious or total loss of product. 

Membrane filters are used under vacuum, with positive pressure, or with gravity. Filters have been incorporated into certain disposable tips for use with semiautomatic pipettes. These filters minimize the exchange of aerosol droplets between the tips and the pipette. This is of particular importance for DNA amplification and microbiological procedures. Other membrane filters are designed for ultrafiltration and are available with a variety of pore sizes for selective filtration. Ultrafiltration is a technique for removing dissolved particles using an extremely fine filter. It is used to concentrate macromolecules, such as proteins, because smaller dissolved molecules pass through the filter. 

When validating passive sampling it is difficult to select an appropriate benchmark with which to compare it since spot sampling concentrations are operationally defined, and fractions measured by filtration/ultrafiltration may not coincide exactly with fraction sequestered by passive samplers. The use of a tank trial where repeated spot samples can be taken to define the concentration profile over the deployment period shows promise, but in the study outlined above some problems were identified. There were indications that the dissolved organic material (DOM) in the finite volume... 

In addition to methods that yield average molecular weights, there are a number of methods (gel filtration, ultrafiltration, small-angle X-ray scattering) that measure molecular size. In these methods, model compounds of known molecular weight and composition are used to estimate the molecular weight of humic substances. Problems can arise if the model compounds are not sufficiently similar to the humic substances of interest. Choice of appropriate model compounds is hampered by lack of detailed information about the chemical structures of humic substances. 

Let us examine the TFF technique and a typical process regime. Tangential Flow Filtration is the general term used to describe filtration where cross flow parallel to the filter surface is used to enhance filtration rate. This is in contrast to dead ended filtration where the fluid path is solely through the filter. If the membrane used to make the separation is microporous (0.2-0.1+5 urn pore size), the technique is more specifically called mdcroporous tangential flow filtration. Ultrafiltration, a subset of Tangential Flow Filtration, employs a finer, anisotropic membrane able to retain macromolecules, albumin for instance. We will emphasize the use of ultrafiltration membranes in this discussion. 

Sedimentation by gravity Cent rifugation/ultra centrifugation Filtration/ultrafiltration... 

The model system described above remains anyhow a simplified model for epithelia, as it neglects diffusive phenomena in the inner compartment and the possibility of coupling between the passive and active solute flows, which can be excluded only in mosaic membranes. In any case the results seem useful in order to explain the experimental data and to obtain a better control of the experiments. In effect, the variability of the filtration, ultrafiltration and apparent reflection coefficients which appear to be a function of both the experimental conditions and of the activity of the epithelia, imposes to be very careful in programming the experiments and when comparing the values existing in literature, often determined in poorly defined conditions. 

As the L/S ratio remains high, a concentration stage must be kept in the purification process. Evaporation is an expensive step that may be replaced by membrane filtration. Ultrafiltration was therefore investigated for its capability to achieve purification (in the same way as the alcohol precipitation) and concentration at the same time. Ultrafiltration was tested using differents membranes with an MWCO ranging from 1 to 50 kDa in order to obtain a minimum concentration ratio (CR) of 2 with a minimal organic matter loss. 

Researchers have recently developed four main types of processes to separate and purify whey proteins in an attempt to leave them in their more biologically active native forms. The types are selective precipitation, membrane filtration (ultrafiltration), selective adsorption, and selective elution (ion exchange). ... 

Filtration, ultrafiltration The removal of particles of 0.001 to 0.1 microns in size. 

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