JPH05209307A - Core-sheath fibrous gel and its production - Google Patents

Abstract

PURPOSE:To obtain the subject gel, good in reactional efficiency, excellent in strength and compatibility and useful as bioreactors, etc., without settling or entangling fiber by discharging a specific mixed aqueous solution together with fiber having a specified value or below of specific gravity, forming the mixed aqueous solution and gelatinizing the resultant formed material. CONSTITUTION:A mixed aqueous solution of (A) a water-soluble synthetic polymer such as PVA with (B) water-soluble polysaccharides such as an alginate having the ability to gelatinize by contact with cations, together with fiber such as PP having <=1 specific gravity, is discharged from a nozzle and the discharged material is then brought into contact with an aqueous solution containing cations and formed. The component (A) is subsequently gelatinized to afford the objective get.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a core-sheath fibrous gel useful as a carrier used in bioreactors and the like, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, studies have been conducted to immobilize biocatalysts such as enzymes and microorganisms and efficiently utilize their functions. One of the methods for immobilizing the biocatalyst is the entrapping immobilization method in which the biocatalyst is wrapped as it is using a polymer material, and agar, alginate, carrageenan, polyacrylamide are commonly used polymer materials for this method. , Polyvinyl alcohol, polyethylene glycol,
There are photo-curable resins and the like. The shape of the carrier may be spherical, dice-shaped, sheet-shaped, tubular or fibrous. Conventionally, there are known research examples in which a granular carrier such as a spherical or dice is put into a wastewater treatment tank to improve its efficiency, but in the case of a granular carrier, the carrier may flow out of the system. There is
Equipment such as filters is required. On the other hand, since the fibrous carrier has a wide active surface, it can be expected to increase the reaction efficiency, and if fibers are bundled and one end thereof is fixed to the tank,
Since the carrier does not flow out of the system, a device such as a filter becomes unnecessary. As a conventional fibrous carrier, there are known a method in which ordinary fibers are used as a carrier to wait for the biocatalyst to adhere, and a method in which only a polymer gel is processed into a fibrous form to enclose or adhere the biocatalyst.

[0003]

Since the carrier using ordinary fiber cannot entrap and fix the biocatalyst, only the surface to which the biocatalyst is attached can participate in the reaction. Further, the affinity with the biocatalyst is poor, and the biocatalyst attached to the surface is easily peeled off, which is not preferable as a carrier. A carrier obtained by processing the gel itself into a fibrous form is capable of entrapping and fixing biocatalysts and is excellent in the habitability of microorganisms, but due to the low strength of the gel, it can be treated by wastewater treatment or water flow in various bioreactors. Be disconnected. Further, when the specific gravity of the fibrous carrier is larger than 1, there is a problem in that the fibrous carrier is precipitated in water or the fibers are entangled with each other due to aeration and the reaction efficiency is deteriorated. It is an object of the present invention to provide a fibrous carrier which does not settle in water or is not entangled with each other and has high strength and excellent affinity with a biocatalyst.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that the sheath portion is a gel composed of a water-soluble synthetic polymer (A) and the core portion is The inventors have found a core-sheath fibrous gel, which is a fiber having a specific gravity of 1 or less, and completed the present invention. Here, the fibers of the core are
The gel which plays a role of reinforcing and adjusting the specific gravity, and the gel of the water-soluble synthetic polymer (A) in the sheath portion plays a role of immobilizing biocatalyst. Therefore, if the amount of the gel composed of the water-soluble synthetic polymer (A) to be coated is too small, there is not much difference from the ordinary biofilm, and the efficiency as a bioreactor carrier becomes poor.
In order to effectively fix the biocatalyst, the thickness of the gel made of the water-soluble synthetic polymer (A) is preferably 10 μm or more, more preferably 50 μm or more. The fiber having a specific gravity of 1 or less (preferably a specific gravity of 0.98 or less) used in the present invention is not particularly limited as long as it has strength enough to withstand use in a reaction tank, but a diameter of 20 μm or more is preferable. For example, synthetic fibers such as polyethylene fibers and polypropylene fibers can be used. Examples of the water-soluble synthetic polymer (A) constituting the gel composed of the water-soluble synthetic polymer (A) include polyvinyl alcohol, polyacrylamide, polyethylene glycol and the like. Although the one in which the biocatalyst is not entrapped and immobilized in the polymer gel is also within the scope of the present invention, considering the efficiency in the bioreactor, the one in which the biocatalyst is entrapped and immobilized in the polymer gel is preferable. The biocatalyst used here is not particularly limited, and any microorganism and enzyme can be immobilized by the present invention. Further, to the gel comprising the water-soluble synthetic polymer (A) of the present invention, a microbial medium, a filler for adjusting the specific gravity of the produced gel, and the like may be added within a range that does not inhibit gelation.

Next, a method for producing the core-sheath fibrous gel will be described. First, a mixed aqueous solution containing a water-soluble synthetic polymer (A), which is the main component of the gel, and a water-soluble polysaccharide (B) having the ability to gel by contact with a cation is prepared.
When the above-described biocatalyst such as a microorganism or enzyme, a culture medium of the microorganism, and a filler for adjusting the specific gravity are added, they are added to this mixed aqueous solution. Specific examples of the water-soluble polysaccharide (B) having the ability to gel upon contact with a cation include alginate, carrageenan, mannan, chitosan, etc. Among them, sodium alginate is particularly preferable. Next, the aqueous solution containing the component (A) and the component (B) is discharged from the nozzle together with the fiber having a specific gravity of 1 or less, and brought into contact with the aqueous solution containing cations to form a core-sheath fibrous gel. Specific examples of the cation used here include at least metal cations such as calcium ion, magnesium ion, strontium ion, barium ion, aluminum ion, potassium ion, cerium ion and nickel ion; and organic cations such as ammonium ion. Included are compounds containing one, but calcium chloride is particularly preferable.

Finally, the core-sheath fibrous gel can be obtained by gelling the water-soluble synthetic polymer (A) which is the main component of the gel. As a method of gelling the water-soluble synthetic polymer (A), a method of contacting with a polymerization initiator and a crosslinking agent to polymerize and crosslink, a method of irradiating with light or an electron beam to crosslink, and freeze-thawing once or more. A method of producing fine crystals by carrying out the method, a method of bringing into contact with an aqueous solution of a compound having a syneresis action of the water-soluble synthetic polymer (A), and a method of gelling are considered. In particular, when immobilizing the biocatalyst, a method of gelling the biocatalyst by a method that does not inhibit its activity is preferable. Particularly, a method of performing freeze-thawing once or more, and a method of contacting with an aqueous solution of a compound having a syneresis action are preferable. Freeze and thaw 1
When it is performed more than once, the freezing temperature is preferably −5 ° C. or lower in order to generate sufficient fine crystals. Further, the freeze-thaw operation may be repeated in order to increase the strength of the gel.

When the water-soluble synthetic polymer (A) is brought into contact with an aqueous solution of a compound having a synergic action, the aqueous solution of the water-soluble synthetic polymer (A) having a synergic action includes sodium sulfate, ammonium sulfate and sulfuric acid. Potassium, magnesium sulfate, aluminum sulfate, sodium citrate, ammonium citrate, potassium citrate, magnesium citrate, aluminum citrate, sodium tartrate,
An aqueous solution containing at least one of compounds such as ammonium tartrate, potassium tartrate, magnesium tartrate and aluminum tartrate can be mentioned, and an aqueous solution of sulfate is particularly preferable.

The core-sheath fibrous gel thus produced has such strength that it will not be deformed or damaged for a long period of time in various types of reaction tanks and will not be immersed in water or various chemical solutions. , Continuous operation becomes possible. Further, the fibers do not sink or get entangled in water, and the utility as a carrier for a biological reaction with high reaction efficiency is exhibited.

[0009]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Example 1 Polyvinyl alcohol manufactured by Kuraray Co., Ltd. (hereinafter abbreviated as PVA) (average polymerization degree: 4000, saponification degree: 99.85)
(Mol%) is washed with warm water of 40 ° C. for about 1 hour, and water is added to PVA so that the PVA concentration becomes 10 wt%, and the total amount is 400%.
The pH was adjusted to 6 and adjusted to pH 6. 1 in an autoclave
After treatment at 20 ° C. for 30 minutes to dissolve PVA, the mixture was allowed to cool to room temperature. To this PVA aqueous solution, 200 g of 4% sodium alginate aqueous solution was added and mixed, and further collected from the wastewater treatment tank of Kuraray Okayama Factory (1-2-1, Kaigandori, Okayama City, Okayama Prefecture) and concentrated. 200 g of the obtained activated sludge (MLSS 80,000 mg / liter (hereinafter abbreviated as mg / l)) was added and sufficiently stirred. A polypropylene spun yarn (diameter 200 μ
m, specific gravity 0.91). The discharge port is 0.
It was dipped in a ₂ mol / l calcium chloride (CaCl ₂ ) aqueous solution, and the ejected product was drawn at a speed of 5 m / min. The retention time of the discharged material in the CaCl ₂ aqueous solution was set to 1 minute. The surface of the yarn was immediately covered and solidified by contact with the discharged CaCl ₂ aqueous solution. Lightly wash this with distilled water, then -20 ℃
After freezing in a freezer for 24 hours, it was thawed at room temperature.
These freezing and thawing operations were repeated twice. This gave an opaque brown flexible core-sheath fibrous gel. The obtained core-sheath fibrous gel was cut into 50 cm pieces, 100 pieces were aligned, and one end was fixed. This was immersed in the activated sludge aeration tank of Kuraray Okayama Factory for 10 days. Since the color of the core-sheath fibrous gel changed from light brown to dark brown, the growth of activated sludge was confirmed. Further, since the shape of the core-sheath fibrous gel did not change before and after the culture, it was found that the core-sheath fibrous gel also has excellent durability. The untreated wastewater from Kuraray Okayama Factory is converted to TOC (Tot
al Organic Carbon) value 100mg
20 liters of the drainage liquid obtained by adjusting to 1 / l was placed in a test aeration tank, and one end of 1 kg of core-sheath fibrous gel fixed was fixed on the bottom surface of the test aeration tank. Since the specific gravity of the core part was 1 or less, the core-sheath fibrous gel was in a state of being arranged substantially vertically in water. Therefore, the core-sheath fibrous gel was not entangled even when aerated. The TOC value of the treated solution obtained by aeration for 30 minutes was 2 mg / l, and it was found that sufficient biological activity was exhibited.

Comparative Example 1 PVA (average polymerization degree: 4000, saponification degree: 99.85 mol%) manufactured by Kuraray Co., Ltd. was washed with warm water at 40 ° C. for about 1 hour, and then PVA was adjusted to a PVA concentration of 10 wt%. Water was added to bring the total amount to 400 g and the pH was adjusted to 6. This was treated in an autoclave at 120 ° C. for 30 minutes to dissolve PVA and then allowed to cool to room temperature. To this PVA aqueous solution, 200 g of 4% sodium alginate aqueous solution was added and mixed, and further collected from the wastewater treatment tank of Kuraray Okayama Factory (1-2-1, Kaigandori, Okayama City, Okayama Prefecture) and concentrated. 200 g of the obtained activated sludge (MLSS 80,000 mg / l) was added and sufficiently stirred. This mixed liquid was discharged at the tip together with rayon spun yarn (diameter 200 μm, specific gravity 1.52) from an injection needle-shaped discharge port having an inner diameter of 0.2 mm. The discharge port is 0.2 mol / l calcium chloride (CaC
l ₂ ) It was immersed in an aqueous solution, and the discharged product was drawn at a speed of 5 m / min. The retention time of the discharged material in the CaCl ₂ aqueous solution is 1
Minutes The discharged product immediately covered the surface of the yarn and solidified by contact with the CaCl ₂ aqueous solution. After lightly washing this with distilled water and freezing in a freezer at -20 ° C for 24 hours,
This was thawed at room temperature, and this freezing and thawing operation was repeated twice. This gave an opaque brown flexible core-sheath fibrous gel. The obtained core-sheath fibrous gel was cut into 50 cm pieces, 100 pieces were aligned, and one end was fixed. This was immersed in the activated sludge aeration tank of Kuraray Okayama Factory for 10 days. Since the color of the core-sheath fibrous gel changed from light brown to dark brown, the growth of activated sludge was confirmed. TOC value of untreated water from Kuraray Okayama Factory is 100
20 liters of the drainage liquid obtained by adjusting to mg / l was put into a test aeration tank, and one end of 1 kg of the core-sheath fibrous gel fixed was fixed to the bottom surface of the test aeration tank. Since the specific gravity is greater than 1, the core-sheath fibrous gel lay in the bottom surface of the aeration tank in water, and the core-sheath fibrous gel was entangled with each other without being vertically aligned even when aeration was performed.

Comparative Example 2 A polypropylene spun yarn similar to that used in Example 1 was cut into 50 cm pieces, 10 pieces were aligned, and one end was fixed. This was immersed in the activated sludge aeration tank of Kuraray Okayama Factory for 10 days. A small amount of activated sludge adhered to the surface of the yarn. The untreated wastewater from Kuraray Okayama Factory is converted to TOC (Tot
al Organic Carbon) value 100 mg / l
20 liters of the drainage liquid obtained by adjusting to 1. was put into a test aeration tank, and one end of 1 kg of polypropylene spun yarn was fixed to the bottom surface of the test aeration tank. Since the specific gravity is 1 or less, the core-sheath fibrous gel was in a state of being arranged almost vertically in water, but the TOC value of the treatment liquid obtained by aerating for 30 minutes was 65 mg / l, The activity was insufficient.

Comparative Example 3 PVA manufactured by Kuraray Co., Ltd. (average degree of polymerization: 4000, saponification degree: 99.85 mol%) was washed with warm water at 40 ° C. for about 1 hour, and then PVA was adjusted to a PVA concentration of 10 wt%. Water was added to bring the total amount to 400 g and the pH was adjusted to 6. This was treated in an autoclave at 120 ° C. for 30 minutes to dissolve PVA and then allowed to cool to room temperature. To this PVA aqueous solution, 200 g of a 4% sodium alginate aqueous solution was added and mixed, and then collected from the wastewater treatment tank of the Kuraray Okayama Factory and concentrated to obtain an activated sludge (MLSS 80000).
200 mg of (mg / l) was added and sufficiently stirred. Only this mixed solution was discharged from the injection needle-shaped discharge port having an inner diameter of 0.2 mm at the tip. The discharge port was dipped in a 0.2 mol / l calcium chloride (CaCl ₂ ) aqueous solution to discharge the discharge product at 10 cm / l.
It was taken at the speed of s. The retention time of the discharged material in the CaCl ₂ aqueous solution was set to 1 minute. The discharged product was immediately solidified by contact with the CaCl ₂ aqueous solution. This was lightly washed with distilled water, frozen in a −20 ° C. freezer for 24 hours, and then thawed at room temperature. Further, this freezing and thawing operation was repeated twice. This gave an opaque brown flexible fibrous gel. The obtained fibrous gel was cut into 50 cm pieces, 100 pieces were aligned, and one end was fixed. This was immersed in the activated sludge aeration tank of Kuraray Okayama Factory for 10 days. Since the color of the fibrous gel changed from light brown to dark brown, the growth of activated sludge was observed. However, since the fibrous gel was cut by being immersed in the aeration tank, it was revealed that there was a problem in the strength of the fibrous gel.

[0013]

EFFECTS OF THE INVENTION As is clear from the above examples, by using a core-sheath fibrous gel in which the sheath portion is a gel composed of a water-soluble synthetic polymer and the core portion is a fiber having a specific gravity of 1 or less, The fibers do not settle or become entangled in the tank, and can be applied to bioreactors such as wastewater treatment as a high-strength fibrous carrier with good reaction efficiency.

Claims (4)

[Claims] 1. A core-sheath fibrous gel in which the sheath portion is a gel composed of a water-soluble synthetic polymer (A) and the core portion is a fiber having a specific gravity of 1 or less. 2. A mixed aqueous solution containing a water-soluble synthetic polymer (A) and a water-soluble polysaccharide (B) capable of gelling upon contact with a cation is discharged from a nozzle together with fibers having a specific gravity of 1 or less, and discharged. The method for producing a core-sheath fibrous gel according to claim 1, wherein the water-soluble synthetic polymer (A) is gelled after the material is molded by contacting it with an aqueous solution containing a cation. 3. The method for producing a core-sheath fibrous gel according to claim 2, wherein the method of gelling the water-soluble synthetic polymer (A) is a method of performing freezing and thawing at −5 ° C. or lower at least once. .. 4. The core-sheath fibrous form according to claim 2, wherein the method of gelling the water-soluble synthetic polymer (A) is a method of bringing the water-soluble synthetic polymer (A) into contact with a solution having a syneresis action. Method for producing gel.