JP3577992B2 - Membrane separation method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a membrane separation method suitable for separating bacterial cells from a fermentation liquor and recovering valuable resources by a membrane filtration, or for desalting and concentrating a protein solution. The present invention relates to a membrane separation method for maintaining a high permeation flux and reducing the frequency of chemical cleaning of a membrane.
[0002]
[Prior art]
When commercializing valuable products such as enzymes produced by a fermentation method, for example, enzymes such as lipase, cellulase, and xylase, bioactive peptides, and proteins, separating the producing bacteria from the fermentation products and recovering valuable products. There is a need. BACKGROUND ART Conventionally, there is a diatomaceous earth filtration method as a general method for recovering a target valuable substance from a fermentation liquid and separating cells. In the diatomaceous earth filtration method, since a large amount of diatomaceous earth is used as a filter aid or a precoating agent, the cells containing diatomaceous earth are separated. The diatomaceous earth-mixed cells cannot be incinerated and are discarded, so there is a problem with the disposal site.
[0003]
For this reason, as a separation method without using diatomaceous earth, a membrane separation method using an MF (microfiltration) membrane or a UF (ultrafiltration) membrane has been studied. Application is being attempted.
[0004]
Separation of the cells from the fermentation solution by the membrane separation method and recovery of the target valuables include filtration and concentration of the fermentation solution (permeation of valuables and concentration of the cells) and diafiltration (concentration of the concentrated solution by water treatment). (Recovery of valuables remaining on the permeate side). That is, first, the fermented liquor is subjected to membrane separation treatment to collect valuable resources on the permeate side, and at the same time, to concentrate the cells (hereinafter, this may be referred to as a “concentration step”), and the concentration of the cells is increased to some extent. After proceeding, by performing an operation called diafiltration in which membrane separation is continued while gradually adding (water-treating) water to the concentrate side, valuable substances remaining in the concentrate side are transferred to the permeate side. to facilitate recovery (hereinafter, sometimes referred to as "pressurized water process".).
[0005]
However, when a biological liquid such as a fermentation liquid or a protein solution is subjected to membrane separation treatment, the membrane is significantly contaminated by bacteria, proteins, lipids, etc. contained in the liquid to be treated, and the permeation flux of the membrane is increased. However, there is a problem in that the rate of decay decreases early. In particular, as described above, when the concentration step and the water addition step are performed, the highly concentrated liquid is treated in the concentration step, so that the membrane becomes heavily contaminated.
[0006]
Conventionally, in a general membrane separation process, as a countermeasure against the contamination of the membrane, the back surface of the membrane is back-washed by backwashing the washing water from a permeated liquid side (secondary side) to raw water or a concentrated liquid side (primary side). Removal of contaminants or chemical cleaning of the film is employed. In addition, by increasing the film area, film contamination can be relatively reduced. However, the chemical cleaning significantly lowers the operation efficiency of the membrane separation device, and also has problems such as shortening of the membrane life due to deterioration of the membrane and treatment of the chemical cleaning wastewater. Enlarging the membrane area is disadvantageous in terms of cost because the size of the membrane separation equipment increases. Accordingly, it is desirable to reduce the frequency of chemical cleaning of the membrane as much as possible, and to effectively prevent a reduction in the permeation flux of the membrane by backwashing with a minimum membrane area.
[0007]
In general, when backwashing a membrane, a permeate is often used as backwash water.
[0008]
[Problems to be solved by the invention]
However, in the case of membrane separation of fermentation liquid or protein solution, since the permeated liquid contains enzymes and proteins to be recovered, the use of this as backwash water may reduce the recovery rate of the target substance. In addition, they may adhere to the film surface in the backwashing step and cause secondary contamination.
[0009]
From the viewpoint of the backwashing effect, it is preferable to use warm water as the backwashing water.By performing the hot water backwashing, the effect of peeling off the membrane contaminants due to the backwashing can be improved. When the permeate obtained by the membrane separation treatment is heated, valuable substances such as proteins contained in the permeate are denatured, so that the permeate cannot be heated. In addition, by causing the hot water to flow back to the primary side of the membrane separation device, valuables in the primary side liquid containing valuables may be denatured.
[0010]
The present invention solves the above-mentioned conventional problems, and performs effective backwashing to maintain a high permeation flux in the membrane separation treatment of a biologically-treated liquid such as a fermentation solution or a protein solution. It is an object of the present invention to provide a membrane separation method that can perform the method.
[0011]
[Means for Solving the Problems]
The membrane separation method of the present invention is a membrane separation method for a biological liquid to be treated containing cells, proteins, or the like, wherein the liquid to be treated is sent to a membrane separation device, a permeate is taken out , and the concentrated liquid is concentrated. A diafiltration step of performing a membrane separation while adding water to the concentrate side after the concentration step, and a process in the membrane separation apparatus after the first step is completed. A second step of discharging the liquid, and after the second step, a third step of backwashing by supplying warm water consisting of backwashing water other than the permeate from the permeate side of the membrane separation device. The first step, the second step, and the third step are repeatedly performed.
[0012]
In the present invention, after the liquid to be treated in the membrane separation device is drained, backwashing is performed periodically to backflow hot water, so that membrane contaminants are effectively peeled and removed, and the permeation flux of the membrane is increased. Can be maintained.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0014]
FIG. 1 is a system diagram showing an embodiment of the membrane separation method of the present invention.
[0015]
This method is to carry out a recovery of the bacterial cell separation and purpose valuables from the fermentation liquor, was first fed to the adjustment tank 2 by a pump P ₁ a predetermined amount of the liquid to be treated to be processed solution storage tank 1 after, the valve V ₁ opened to supply the liquid to be treated in the adjustment tank 2 by operating the pump P ₂ in the valve V _2, V ₃ closed in the membrane separation device 3 in crossflow, a permeate containing the desired valuables It is collected in the permeated liquid receiving tank 4. The concentrated liquid flowing out of the membrane separation device 3 is returned to the adjustment tank 2 and circulated. Along with this, the cells are concentrated on the concentrate side. After it progressed concentrated to a predetermined magnification, diafiltration to further recover valuable materials remaining in the concentrate side by introducing dilution water by operating the pump P _3. In this case, the amount of water and the form of water required for diafiltration are appropriately determined according to the concentration of the target valuables in the concentrate, the rejection of the target valuables by the membrane, and the target recovery rate of the target valuables. Selected. The form of water addition may be continuous water addition or intermittent water addition, but a method of gradually adding an amount of water corresponding to the amount of the permeated liquid while keeping the amount of the concentrated liquid constant is generally used.
[0016]
After the target valuables are collected on the permeate side at a predetermined recovery rate in this way, the above-mentioned membrane separation processing step is terminated, the pumps P ₂ and P ₃ are stopped, the valve V ₃ is opened, and the membrane separation device is opened. The concentrated liquid in the primary side of 3, the concentrated liquid piping and the adjusting tank 2 is discharged out of the system.
[0017]
After the discharge process is completed, the valve V ₁ is closed, by operating the pump P ₄ is opened valves V _2, the backwash by flowing back to the primary side of the hot water from the secondary side of the membrane separation device 3 performs.
[0018]
The temperature of the hot water used for the backwashing is not particularly limited, and is appropriately set according to the heat resistance of the membrane material, the nature of the stain, and the like. In a normal case, hot water of about 40 to 80 ° C. is used.
[0019]
The backwashing conditions such as the amount of hot water to be fed are not particularly limited and are appropriately determined depending on the degree of dirt. Generally, about ¹⁰ to 100 L of hot water is applied to a membrane area of 1 m2. It is preferable that the liquid is sent for about 0.5 to 100 minutes at a liquid sending rate of 1 to ²⁰ L / min per 1 m ^{2 of} area, and backwashed.
[0020]
After the backwashing step is completed, a predetermined amount of the liquid to be treated is again sent from the liquid to be treated storage tank 1 to the adjusting tank 2, and the membrane separation step, the discharging step, and the backwashing step are repeated.
[0021]
In the present invention, since backwashing is performed using warm water, contaminants on the membrane can be effectively washed and removed.However, membrane contamination is particularly remarkable in membrane separation treatment of a biological liquid to be treated. Washing is preferably performed before the permeation flux of the membrane decreases. The backwash interval, properties and membrane separation processing conditions the liquid to be treated, varies depending or model of membrane area and membrane, backwash every time membrane separation liquid to be treated with a membrane area of 1 m ² per 50~1000L Is preferably performed.
[0022]
As the membrane of the membrane separation device 3, an MF membrane or a UF membrane is used. The membrane material is not particularly limited, and a polyolefin membrane, a polysulfone membrane, a Teflon membrane, a ceramic membrane, or the like is used. Although there is no particular limitation on the membrane type, a hollow fiber, a tubular, a spiral, a plate & frame type membrane module, or the like is generally used. Selection of the MF or UF membrane and selection of the membrane material and membrane type are intended for use, that is, whether the intended valuable is recovered in the permeate side or concentrated in the concentrated solution, or the intended valuable is used. It is carried out in consideration of the molecular weight and other properties of the liquid to be treated such as a fermentation liquid.
[0023]
Although FIG. 1 illustrates the case where the cells are separated from the fermented liquor and the target valuables are collected by diafiltration, the membrane separation method of the present invention is not limited to this method. Biological liquid to be treated such as separation of bacterial cells from fermentation liquor, recovery of target valuables such as proteins, enzymes such as lipase, cellulase and xylase, and physiologically active peptides, and desalting and concentration of protein solution This is extremely useful for a membrane separation treatment comprising a concentration step and a water addition step .
[0024]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
[0025]
Example 1
According to the method of the present invention shown in FIG. 1, cells of the fermented broth (dry bacterial cell concentration: 1% by weight, target valuable substance: enzyme having a molecular weight of about 18,000) were separated.
[0026]
A MF hollow fiber membrane module (pore diameter: 0.1 μm, outer diameter: 5 cm, length: 1 m, membrane area: 1 m ² ) was used for the membrane separator, processing temperature: 20 ° C., module inlet pressure: 2.0 kg / cm ² , module outlet pressure: Cross flow filtration was performed under the condition of 1.5 kg / cm ² .
[0027]
50 L of the fermented liquid transferred from the liquid storage tank to the adjustment tank is sent to a membrane separation device, and the concentrated liquid is separated and concentrated for circulating the cells, and the target valuables are collected on the permeate side. At the stage where the circulating liquid was concentrated to some extent, diafiltration by water treatment was performed, and the treatment was continued until a predetermined recovery rate was achieved. In the treatment of 50 L of the fermentation liquid, 30 L of the permeate was recovered in the concentration step, and 40 L of the permeate was recovered in the water addition step.
[0028]
After the completion of the membrane separation step, the concentrate was blown out from the membrane separation unit. The amount of the discharged concentrated liquid (cell-containing waste liquid) was 20 L.
[0029]
Then, 50 L of city water at 60 ° C. was flowed back from the permeated liquid side of the membrane separation unit at a rate of 10 L / min with a back washing pump to back wash the membrane.
[0030]
After the backwash was completed, the membrane separation step, discharge step, and washing step of 50 L of the fermentation liquor were repeated in the same manner as described above, and 500 L of the fermentation liquor was treated by performing 10 membrane separation steps.
[0031]
FIG. 2 shows the change in the permeation flux of the membrane in each of the membrane separation steps (the average value of the permeation flux in the concentration step and the permeation flux in the water addition step) in this treatment.
[0032]
Comparative Example 1
In Example 1, the treatment was carried out in the same manner except that city water at 18 ° C. was used as the backwash water, and the change in the permeation flux was examined in the same manner. The results are shown in FIG.
[0033]
Comparative Example 2
In Example 1, the same treatment was performed except that 500 L of the fermented liquor was treated at a time without backwashing. That is, using a 700 L capacity adjusting tank, 300 L of the permeate was recovered in the concentration step, 400 L of the permeate was recovered in the water addition step, and 200 L of the concentrate (cell-containing waste liquid) was discharged.
[0034]
In this process, the permeation flux was checked every time 70 L of the fermentation liquor was processed, and the results are shown in FIG.
[0035]
From FIG. 2, it can be seen that by performing backwashing with warm water, the permeation flux of the membrane can be maintained high.
[0036]
【The invention's effect】
As described in detail above, according to the membrane separation method of the present invention, when performing a membrane separation treatment on a biological target liquid such as a fermentation solution or a protein solution, an effective backwash is performed, and the permeation flow of the membrane is performed. The bundle can be kept high. For this reason, the treatment can be performed with a small-sized membrane separation equipment having a small membrane area. In addition, the frequency of chemical cleaning of the membrane can be reduced to increase the operation efficiency of the apparatus, and the deterioration of the membrane can be prevented to extend the life of the membrane. be able to.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of a membrane separation method of the present invention.
FIG. 2 is a graph showing a temporal change of a permeation flux in Example 1 and Comparative Examples 1 and 2.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Treatment liquid storage tank 2 Adjustment tank 3 Membrane separation device 4 Permeate receiving tank

Claims (3)

In a membrane separation method of a biological liquid to be treated containing cells or proteins,
A concentration step in which the liquid to be treated is sent to a membrane separation device to take out a permeate and concentrate the concentrated solution side, and a diafiltration for performing membrane separation while adding water to the concentrated solution side after the concentration step. A first step consisting of :
A second step of discharging the liquid to be treated in the membrane separation device after the first step,
After the second step, a third step of backwashing by supplying hot water comprising backwashing water other than the permeate from the permeate side of the membrane separation device,
A membrane separation method, wherein the first step, the second step, and the third step are repeatedly performed. In the third step, the film area is 1 m ² 10 to 100 L of warm water for 1 m of membrane area ² The membrane separation method according to claim 1, wherein the liquid is fed for 0.5 to 100 minutes at a liquid feed rate of 1 to 20 L / min and backwashed. In the first step, the film area is 1 m ² The membrane separation method according to claim 1 or 2, wherein the second step and the third step are performed each time the liquid to be treated is subjected to membrane separation processing in an amount of 50 to 1000 L.

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