Shear separation method and system

Details Shear separation method and system Shear separation method and system

1999-03-03

2002-11-12

Fortuna, Ana (Department: 1723)

Liquid purification or separation

Processes

Liquid/liquid solvent or colloidal extraction or diffusing...

C210S650000, C210S321670, C210S321750, C210S331000, C210S097000, C210S096200, C210S107000

Reexamination Certificate

active

06478969

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to shear separation methods and systems and, more particularly, to shear separation methods and systems wherein microfiltration, ultrafiltration, diafiltration, or concentration can be achieved.
BACKGROUND OF THE INVENTION
Separation methods and systems, such as those employing filters, typically are employed to separate one or more components or substances of a fluid from other components or substances in the fluid. As used herein, the term “fluid” includes liquids, gases, and mixtures and combinations of liquids, gases and/or solids. Conventional separation processes include a wide variety of common processes, such as classic or particle filtration, microfiltration, ultrafiltration, nanofiltration, reverse osmosis (hyperfiltration), dialysis, electrodialysis, prevaporation, water splitting, sieving, affinity separation, purification, affinity purification, affinity sorption, chromatography, gel filtration, bacteriological filtration, and coalescence. Typical separation devices and systems may include dead end filters, cross-flow filters, dynamic filters, vibratory separation systems, disposable filters, regenerable filters including backwashable, blowback and solvent cleanable, and hybrid filters which comprise different aspects of the various above described devices.
Accordingly, as used herein, the term “separation” shall be understood to include all processes, including filtration, wherein one or more components of a fluid is or are separated from the other components of the fluid. The terms “filter”, “separation medium”, and “permeable membrane” shall be understood to include any medium made of any material that allows one or more substances in a fluid to pass therethrough in order to separate those substances from the other components of the fluid. The terminology utilized to define the various substances in the fluid undergoing separation and the products of these processes may vary widely depending upon the application, e.g., liquid or gas filtration, and the type of separation system utilized, e.g., dead end or open end systems; however, for clarity, the following terms shall be utilized. The fluid which is input to the separation system shall be referred to as process fluid and construed to include any fluid undergoing separation. The portion of the fluid which passes through the separation medium shall be referred to as permeate and construed to include filtrate as well as other terms. The portion of the fluid which does not pass through the separation medium shall be referred to as retentate and construed to include concentrate, bleed fluid, as well as other terms.
While many separation applications are quite routine, the separation of relatively small particles or substances from fluids requires separation protocols able to achieve a precise separation size (resolution) with minimal fouling (e.g., clogging with the small particles). This is particularly the situation when separating proteins (natural or recombinant) and other components from process fluids such as milk or products derived from milk (e.g., skim milk, whey, etc.).
Milk contains, among other things, fats, proteins (casein and a variety of other proteins such as &bgr;-lactoglobulin, &agr;-lactalbumin, serum albumin, and immunoglobulins), salts, sugar (lactose), and various vitamins (such as vitamins A, C, and D, along with some B vitamins) and minerals (primarily calcium and phosphorus). The composition of milk varies with the species, breed, feed, and condition of the animal from which the milk is obtained. Moreover, a wide variety of milk or whey proteins are employed as functional and nutritional ingredients in bakery products, pasta, confections, beverages, meats, and other food products. In addition, milk has proven a valuable source of biologically or medically important products. For example, it is possible to obtain antibodies by vaccinating lactating animals and collecting antibodies from their milk (see, e.g., U.S. Pat. Nos. 5,260,057 (Corcle et al.) and 3,128,230 (Heinbach et al.)). Moreover, many species of animals have been genetically engineered to express recombinant proteins in milk. See, e.g., Gordon et al.,
Biotechnology,
5(11), 1183-87 (1987) (mice); Ebert et al.,
Biotechnology,
12(7), 699-702 (1994) (goats); Lee et al.,
J. Control. Release,
29(3), 213-21 (1994) (dairy cows); Limonta et al.,
J. Biotechnol.,
40(1), 49-58 (1995) (rabbits); Clark et al.,
Biotechnology,
7(5), 487-92 (1989) (sheep).
Examples of such recombinant proteins are peptide hormones (e.g., growth hormones (Archer et al.,
Proc. Nat. Acad. Sci. USA,
91(15), 6840-44 (1994)), tissue plasminogen activator (tPA) (Ebert et al., supra), etc.), blood coagulation factors or subunits of them (e.g., factors VIII and IX (Clark et al., supra)), anticoagulation factors or subunits of them (e.g., anti-thrombin III and human protein C), other blood proteins (e.g., serum albumin (Barash et al.,
Mol. Repro. Dev.,
45(4), 421-30 (1996)), beta-globin, &agr;1-antitrypsin (Archibald et al,
Proc. Nat. Acad. Sci. USA,
87(13), 5178-82 (1990)), proteins for foodstuffs, enzymes, and other proteins (e.g., collagen, cystic fibrosis transmembrane conductance regulator (CFIR), antibodies, etc.). See, e.g., U.S. Pat. No. 4,873,316 (Meade et al.), U.S. Pat. No. 5,589,604 (Drohan et al.), and U.S. Pat. No. 5,476,995 (Clark et al.). Secretion of recombinant proteins into the milk of transgenic animals is an efficient method of producing such proteins; concentrations approaching 10 g/I have been reported.
Commercially produced milk commonly undergoes pasteurization to mitigate bacterial growth and homogenization to improve fat dispersion stability. Moreover, in the commercial processing of milk products, it is desirable in certain instances to remove as much fat as possible from the milk products.
Conventional milk processing heretofore has involved the use of mechanical separation (centrifugation), evaporation/crystallization, steam injection, electrodialysis, reverse osmosis, ultrafiltration, gel filtration, diafiltration, and/or ion exchange chromatography. For example, whey typically is subjected to mechanical separation (e.g., centrifuged) to remove fat, condensed via evaporation to increase solids content, and then spray dried or used for lactose crystallization. After desludging, the residual concentrate is dried, which yields whey powder containing about 11-14% protein (which usually is denatured, particularly during the evaporation/condensation step). The whey powder can be subjected to electrodialysis to remove ash and thereby prepare demineralized whey powder. Alternatively, the whey powder can be subjected to reverse osmosis to remove water, thereby obtaining whey powder containing about 12-15% protein. Such a whey powder can be subjected to ultrafiltration or gel filtration to remove further ash and lactose and thereby obtain a whey protein concentrate containing about 30-50% protein, which, in turn, can be subjected to diafiltration or ion exchange chromatography to remove yet more ash and lactose so as to obtain whey protein concentrates containing about 50-90% protein.
Such conventional processing methods carry with them many disadvantages, such as long processing times, high costs, and poor or inconsistent component fractionation. Moreover, it is often difficult to separate a recombinant protein from fluids such as milk by these methods without denaturing or damaging the protein, and it is also difficult to separate different proteins and particles of interest within milk or other fluids. Many of these difficulties are attributable to the aforementioned problems attendant with separating relatively small particles from fluids, namely poor resolution and filter fouling.
One advancement greatly reducing filter fouling is to employ separation methods and systems generating a shear layer at the surface of a filter. A layer of fluid which is adjacent to the surface of a filter and which is in a state of rapid shear flow parallel to the surface of the filter tends to mi

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