Ultrafiltration sequential

Diafiltration is an ultrafiltration process where water or an aqueous buffer is added to the concentrate and permeate is removed (50). The two steps may be sequential or simultaneous. Diafiltration improves the degree of separation between retained and permeable species. 

It is a key step to develop methods to separate peptides with different molecular weights. An ultrafiltration membrane system equipped with the appropriate molecular weight cutoff has been effectively used in separating peptides having desired molecular weights (Jeon et al., 2000). In order to obtain functionally active peptides, it is a common method to use the type of enzymes letting sequential enzymatic digestions. 

Ultrafiltration and Size-Exclusion Chromatography. The apparent molecular weight distribution of each sample was determined by sequential use of ultrafiltration (UF) and size-exclusion chromatography (SEC). A modification of a procedure proposed by Chian and DeWalle (11) was used. Approximately 10 mg of a sample was dissolved in 200... 

Burba, R, Aster, B.,Nifant eva,T.,Shkinev, V., and Spivakov, B. Y. (1998). Membrane filtration studies of aquatic humic substances and their metal species A concise overview. Part 1. Analytical fractionation by means of sequential-stage ultrafiltration. Talanta 45, 977-988. 

Burba, P., Shkinev, V and Spivakov, B.Ya. (1995) On-line fractionation and characterization of aquatic humic substances by means of sequential-stage ultrafiltration. Fresenius J. Anal. Chem., 351, 74-82. 

As depicted in Fig. 18.2, the first step in BE-AES is sequential buffer exchanges using ultrafiltration spin columns. Buffer exchanges are necessary to get the analyte into a known reference buffer. The last round of buffer exchange is used to concentrate the sample. 

Ultrafilters can be used to permit sequential washing and filtering, after which the filter cake is redispersed into suspension, or continuous hollow-fibre ultrafiltration can be used to accomplish the same result (see Figure 7.6). 

Diafiltration is a variation of ultrafiltration, in which fresh solvent is added to the feed solution to replenish the volume ultrafiltered, and in the process washes small molecules such as salts away from the retained macromolecules. Using appropriate replenishing solutions, diafiltration is a common procedure to perform buffer exchange of proteins. Alternatively, a dilute solution may be first ultrafiltered to concentrate the feed material, then diafiltered to purify the retentate. It is sometimes possible to fractionate a mixture of macrosolutes by sequential diafiltration with a series of membranes of progressively lower molecular weight cutoff ratings. 

Those processes can be considered ideal pretreatment for reverse osmosis processes. The concentration and purification of antibiotics by sequential UF and RO,is an example. The removal of antigenic contaminants present in biological mixtures via the combined use of immunocomplexation and ultrafiltration has also been suggested (3 ). ... 

A modification (Doyle et al., 1982) of the four-step mixed anhydride procedure of Krejcarek and Tucker (1977) was used to couple DTPA to HSA. A 17-fold molar excess of In was added to the cooled HSA-DTPA solution, and the mixture stirred for 35 min. The pH was adjusted to pH 4.50 with 1.0 M NaOH, and the solvent was sequentially replaced by ultrafiltration using a 10,000 MWCO membrane, against 200 ml of 0.15 M NaCl and then 400 ml of 0.1 M citrate buffer (pH 5.50) and dialyzed once against 1 liter of 0.1 M citrate buffer (pH 5.50) to remove any unbound In or noncovalently attached DPTA. The HDI complex was shown to be monodisperse by gel chromatography and electrophoresis, immunoreactive via Ouchterlony radial immunodiffusion, and contained... 

Because food products require proteins with special functional properties, water-soluble zein was produced using a dual-phase, sequential enzymatic modification and ultrafiltration. A significant improvement in certain functional properties of zein was observed upon this enzymatic modification in organic solvents [154]. 

In sequential ultrafiltration successive volume reductions occur (Figure 6). Since volume is reduced by 50% at each stage, both the filtrates and retentates contain components of other molecular size fractions consequently, the components contributing to each measured fraction must be taken into account in a mass balance. 

Table V. Two Systems of Simultaneous Equations Used to Solve Sequential Ultrafiltration Mass Balance for Dissolved Organic Carbon in Mass Units...

The sequential ultrafiltration procedure was tested using known initial concentrations of the appropriate metal nitrate salt in Milli-Q water. Volume reduction factors were noted and metal concentrations for each retentate fraction were measured. From these values the mass... 

Figure 7. (a) Evaluation of sequential ultrafiltration scheme with standard solutions of cadmium, cop-... 

Figure 8. Sequential ultrafiltration of organic carbon and metals in spring 1978 (a) Site 1—Bemidji (b) Site 2—Royalton (c) Site 4—Inver Grove Heights (d) Site 5—Minnesota River...

Results of this study as illustrated in Figures 7 and 8 show that (1) the sequential ultrafiltration-mass balance approach is valid for known solutions (2) cadmium, copper, and lead are found in the soluble phase... 

For Lot B the acellular pertussis vaccine components are produced from B. pertussis cultures grown in Stainer-Scholte medium modified by the addition of casamino acids and dimethyl-betacyclodextrin. Fimbriae types 2 and 3 are extracted from the bacterial cells and the pertussis toxin, FHA, and PRN are prepared from the supernatant. These proteins are purified by sequential filtration, salt precipitation, ultrafiltration, and chromatography. Pertussis toxin is inactivated with glutaraldehyde and FHA is treated with formaldehyde. The individual antigens are adsorbed separately onto aluminum phosphate. Diphtheria and tetanus, toxoids are individually adsorbed onto aluminum phosphate. The adsorbed diphtheria, tetanus, and acellular pertussis components are combined in a sterile isotonic sodium chloride solution containing 2-phenoxyethanol as preservative. Each dose contains 10 pg of PT, 5 pg of FHA, 3 pg of PRN, 5pg of FIM, as well as 15Lf of diphtheria toxoid and 5.0 Lf of tetanus toxoid. 

We have used an adaptation of the fluorimetric assay described by Gardiner to measure purine levels in ultrafiltrates of human plasma (collection from different sites), cerebrospinal fluid and bone marrow aspirates. The assay technique allows the sequential determination of three major purine components, i.e. Hypoxanthine (Hx) plus Xanthine (X), Inosine (IR) and Adenosine (AR). 

After a prehydrolysis step (0.05 M HCl, pH 1.4, 2h at 70°C), the solution was cooled to room temperature and adjusted to pH 10.2 with ammonium hydroxide. After a sequential extraction with ammonium hydroxide, alkaline ethanol and alkaline water (both at room temperature and elevated temperature (70 C), the filtrates were bleached (50% H2O2, 2 days, 40 C). After ultrafiltration and spray... 

Fluoride removal by coagulation with Moringa oleifera seeds, followed by separation with ultrafiltration membranes, has been reported. The advantage of proposing a sequential process using membrane separation is that it removes color and turbidity, caused by the use of M. oleifera as a coagulant, resulting in water that meets portability standards (Bazanella et al, 2012). 

The Laboratory of Dairy Technology Research of the Institut National de la Recherche (INRA) in Rennes, France, is investigating the application of these techniques for improved propionic acid production (Boyaval and Corre 1995). Colomban et al. (1993) demonstrated the production of propionic acid from whey permeate by P. acidipropionici at high cell density combined with sequential cell recycling and ultrafiltration. O Figure 3.3 is a diagram of the process employing a 5-m industrial pilot plant bioreactor. 

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