JPS59189986A - Treatment of protein-contg. aqueous solution - Google Patents

Abstract

PURPOSE:To treat an aqueous solution containing protein such as soybean milk with a stable speed of water permeation over a long time, by treating said protein-contg. aqueous solution using a selectively permeable membrane, e.g. an ultrafiltration one, pretreated with lecithin. CONSTITUTION:A selectively permeable membrane such as an ultrafiltration one is treated by immersing it in a lecithin solution or letting the lecithin solution permeate through it and then washed with water to fix lecithin onto the membrane. Using this selectively permeable membrane treated with lecithin, a protein-contg. aqueous solution is concentrated or refined. Petroleum ether, benzene, carbon tetrachloride, alcohol or the like is used as a solvent for lecithin, and the concentration of lecithin dissolved in the solution is generally above a few tens ppm, pref. 10- a fed thousands ppm. The selectively permeable membrane treated with lecithin inhibits the deposition of protein onto the membrane and suppresses the deterioration of a speed of water permeation with time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating a protein-containing aqueous liquid, and more specifically, a method for treating a protein-containing aqueous liquid that can process a protein-containing aqueous liquid at a stable water permeation rate over a long period of time. Regarding.

Conventionally, aqueous liquids such as protein-containing solutions are often concentrated by vacuum evaporation, but this method has the problem of denaturing proteins because it requires heating, and is also difficult from an energy standpoint. Because it is undesirable,
In recent years, membrane treatment methods using selectively permeable membranes such as ultrafiltration membranes have been attracting attention. According to this membrane treatment method, no energy is required for heating, and there is no risk of denaturing the kumbaku substance as a result. However, on the other hand, proteins are deposited on the membrane surface, contaminating the membrane, and causing water permeability. The rate decreases significantly over time, making it difficult to treat protein-containing aqueous liquids with a stable water permeation rate over a long period of time. Furthermore, in order to restore the function of the membrane that has been dyed with lη in this way, it is necessary to clean it using special chemicals and methods.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method capable of treating a proteinaceous aqueous liquid at a stable water permeation rate over a long period of time.

The method according to the invention is characterized in that a protein-containing aqueous liquid is treated with a selectively permeable membrane that has been previously treated with lecithin.

In the present invention, the term lecithin refers to soybean, rapeseed,
A natural phospholipid mixture obtained from egg yolk, yeast, etc., i.e.
It contains both a mixture mainly composed of phosphatidylcholine and pure lecithin phosphatidylcholine, but for example, in the fields of medicine and food, soybean lecithin is preferably used because it is safe and is recognized as a food additive. It will be done. As is well known, soybean lecithin is a natural phospholipid mixture containing phosphatidylcholine, phosphatidylethanolamine, phosphaticylinositol, etc. as main components. Moreover, aqueous liquid means an aqueous solution, suspension, and emulsion.

In the method of the present invention, a selectively permeable membrane such as an ultrafiltration membrane is pretreated with a lecithin solution, and then the protein-containing aqueous solution is used for membrane treatments such as concentration and purification. Lecithin is insoluble in water, but dissolves in petroleum ether, benzene, carbon tetrachloride, chloroporum, alcohol, etc., so select a solvent depending on the lipid in the membrane and immerse the membrane in that solution, or The solution is passed through the membrane for treatment. Preferably alcohol is used. After this, when the membrane is washed with water, since lecithin is insoluble in water, the lecithin is fixed to the membrane, and at least a portion of it appears to form a kind of protective film on the membrane surface. The lecithin concentration in the solution is not particularly limited, but is usually several tens of ppm or more, preferably 10 ppm or more.
ppm to several thousand ppm (e.g. 5000 ppm
) is fine.

Although the reason for the selective permeation membrane treated with lecithin is not clear, the method of the present invention prevents protein deposition on the membrane and suppresses the decrease in water permeation rate over time. , it is possible to stably membrane-process protein aqueous liquids, and is suitable for, for example, concentrating soy milk, aqueous albumin solutions, etc.

The present invention will be explained below with reference to Examples.

Example 1 Molecular weight cutoff made of polyacrylonitrile: 13.000
The ultrafiltration membrane was immersed in an ethanol solution containing 200 ppm soybean lecithin for 90 minutes at room temperature, and then washed with water to deposit lecithin on the membrane.

Soy milk with a solid content of 5% by extracting the soluble components of soybeans with hot water 1
5β was obtained and concentrated using the lecithin-treated membrane described above. First, in order to stabilize the surface of the membrane, the soymilk was preconcentrated to a solid content of 5% to 6% at a pressure of 1 kg/cnt G, and then concentrated to 6% at a pressure of 1 kg/cn+G.
It was concentrated from 10% to 10%. During this concentration, the temperature of the soymilk rose from 12°C to 40°C, but considering that the membrane permeate from this process also has the same viscosity as Yomu Senshin Yosui, The water permeation rate was converted to the water permeation rate at 20°C using the following No\-Gen-Boiseuille equation.

J20-J''' (μt/μ20) is the viscosity of water at temperature BiC and 20°C.

As the results are shown in Figure 1, the water permeation rate of the membrane treated by the method of the present invention was initially 0.46β/m・min, and even at 10% concentration it was 0.45β/M・min. The S* rate was maintained almost constant during the process.

On the other hand, when soy milk was concentrated under the same conditions as above without treating the crotch with lecithin,
The water permeation rate of the membrane was initially 0.64β/m・min, but
At the time of 0% m contraction, it decreased to 0.51β/M·min. The results are also shown in Figure 1G.

Example 2 An ultrafiltration membrane made of polysulfone and having a molecular weight cut off of 10,000 was crushed in a methanol solution containing 180 ppm of soybean lecithin at room temperature for 11 hours, and then washed with water. A 0.1% bovine serum albumin aqueous solution was supplied to this membrane at a temperature of 30° C. and a pressure of 1 kg/c G for 4.2 hours to concentrate the albumin concentration to 0.30%.

As shown in Figure 2, this result shows that the water permeability in the crotch is
During the treatment, the water permeation rate remained the same.

On the other hand, without lecithin treatment, the same membrane as above was supplied with a 0°1% bovine serum albumin aqueous solution for 4.4 hours at a temperature of 30°C and a pressure of 1 kg/cIII G, and the albumin concentration was reduced to 0.32. It was concentrated to %. The water permeation rate of the membrane was initially 1°4- x 10 cc/cl+ seconds, or 6.5 x 10 at the time of 3.2 times concentration.
cc/Cm -sec. The results are also shown in Figure 2.

That is, in actual membrane treatment, it is common to operate for a long period of time, but in such cases, it is better to use a membrane treated by the method of the present invention because it is possible to treat a larger amount of albumin aqueous solution at a stable water permeation rate. This is advantageous because it can be done.

[Brief explanation of drawings]

Figure 1 is a graph showing the change in water permeation rate over time when an ultrafiltration membrane treated by the method of the present invention is used to concentrate soymilk, together with the results for a membrane of a comparative example. 2 is a graph showing a similar change in water permeation rate over time for concentration. Patent applicant: Nitto Electric Industry Co., Ltd. Patent attorney: Itsube Makino

Claims (1)

[Claims] +l) A treatment method characterized by treating a protein-containing aqueous liquid with a selectively permeable membrane that has been previously treated with lecithin.