JPH09192471A - Production of alginate gel sphere - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce alginate gel spheres by an easy operation by sticking droplet of an aq. soln. of a soluble alginate to a substrate and immersing the droplet, together with the substrate, in a hardening soln. SOLUTION: A water-repellent rubber belt 3 as a substrate is wound and stretched around four rolls 2 under a group of droplet feeding nozzles 1 arranged in a line. Droplet of an aq. soln. of a soluble alginate formed by the nozzles 1 is stuck to the belt 3 and sent to a hardening tank 1 filled with a hardening soln. In the tank 4, the droplet parts from the belt the 3 and forms gel spheres. The soluble alginate is not especially limited and it is, e.g. sodium alginate or potassium alginate. The hardening soln. may be any soln. which forms an insoluble alginate by contact with an aq. soln. of the soluble alginate and it is, e.g. an about 25-1,000mM calcium chloride soln.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel method for producing alginate gel spheres.

[0002]

2. Description of the Related Art It is known that an aqueous solution of an alginic acid-soluble salt such as a sodium alginate solution forms a gel when contacted with an aqueous solution of a divalent or higher valent metal salt excluding magnesium ion and mercury ion. Since this gelation occurs instantly, gel spheres can be easily created by adding drops of an aqueous solution of an alginic acid-soluble salt to a hardening liquid such as calcium chloride (hereinafter, this method is referred to as "droplet hardening method"). . For example, by appropriately adjusting the viscosity and spinnability of the alginic acid-soluble salt aqueous solution and using an optimum device,
A large amount of homogeneous gel spheres can be produced in a short time (JP-A-62-266137 and JP-A-63-197530).

Although the droplet curing method is excellent in mass productivity as described above, in order to encapsulate an object in a gel sphere or obtain a complicated gel sphere structure, further devising is required. For example, a method using a multi-nozzle for enclosing a liquid (Japanese Patent Laid-Open No. 52-117282) or a method of adding a solution containing a thickened hardening cation to an aqueous solution of an alginic acid-soluble salt (Japanese Patent Publication No. 41- No. 15501) is known. Also, some solid encapsulation methods have been developed. For example, a method in which an alginic acid-soluble salt aqueous solution in which an object is dispersed is introduced into a nozzle, the amount of liquid between the objects existing in the nozzle is supplied and adjusted by a discharge pump, and then dropped into a curing tank (JP-A-62-170251). Issue)
There is. In another method, after seeds and cultured plants were supplied to the meniscus of the alginic acid-soluble salt aqueous solution formed in the lower inner tube of the multiple nozzle, the alginic acid-soluble salt aqueous solution that had formed the meniscus with the object hardened into droplets. Drop into the tank (RE Garret, JJ Mehlschau, NE Smit
h, MK Redenbaugh, Applied Engineering in Agricul
ture 7 (1), 25-31 (1991) and JP-A-63-209502). In these methods, the nozzle structure and the object supply mechanism are complicated, and the gel sphere generation rate is limited to 0.5 seconds per nozzle. Furthermore, even if the object can be attached to the alginic acid droplets, especially when the object has high water repellency, due to impact at the time of dropping on the curing liquid,
It was observed that objects jumped out of the gel sphere (experimented with Garret et al.'S machine).

On the other hand, a technique of molding an alginic acid gel in a mold (molding die) is known (hereinafter referred to as "molding method"). This method also requires some ingenuity. That is, unlike agar, gelatin, and a photocurable resin, it is difficult to obtain a homogeneous gel-molded product from a mold with alginic acid that forms a gel by contact with a cation having a gelling ability. In order to solve this problem, a curable ion such as phosphate, citrate, tartrate, and sulfite is mixed with an aqueous solution of alginic acid in advance (for example, JP-A-52-53898). These salts delay the gelation of alginic acid by forming a sparingly soluble salt with calcium or hiding calcium.

[0005] In the casting method, it is easy to enclose or attach other objects to the surface before hardening. However, there is an initial cost to make the mold, and
The holding time in the mold until gelation and the step of removing from the mold are required, and the work is more complicated than the droplet curing method, which is a drawback.

As a modification of the casting method, there is known a method of injecting a hardening liquid into an alginic acid-soluble salt aqueous solution placed at the bottom of a round-bottomed container with a nozzle to form alginic acid into a spherical shape (Solimon). et. al., in Synseeds p4
0, Ed. By K. Redenbaugh, CRC Press (1993)). This method required an initial cost higher than that of the casting method, such as the production of an injection nozzle and an injection control device.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a liquid drop curing method without impairing the rapid curing characteristics of alginic acid,
It is an object of the present invention to provide a method for producing a new alginate gel sphere that enables inclusion and mounting of an object.

[0008]

It has been observed that an aqueous solution of sodium alginate has a surface tension similar to that of water, and a droplet of an aqueous solution of an alginic acid-soluble salt on the surface of a flat plate has a contact angle proportional to the water repellency of the flat plate. (The contact angle is the angle formed by the cutting line drawn on the liquid surface and the flat plate surface at the point where the water drop surface and the flat plate surface contact each other, and is said to be proportional to the degree of "wetting" of the substance). Drops of the alginic acid-soluble salt aqueous solution dropped on a flat plate treated with a commercially available silicone-based water repellent agent (spray) had large swelling and a large contact angle was observed (Fig. 1-a). When the liquid droplets together with the flat plate were immersed in a hardening liquid such as calcium chloride, the liquid droplets immediately separated from the surface of the flat plate (Fig. 1-b) and formed into a spherical shape by itself (Fig. 1-c). In addition, even if a droplet was dropped on a water-repellent mesh plate (mesh size 1 mm), similar swelling of the droplet was observed, and when this was immersed in a calcium chloride solution together with the mesh plate, the droplet immediately formed. It released from the plate and formed a gel sphere. Even though the gel spheres were slightly distorted immediately after they were immersed in the curable liquid, the spheres became close to a true sphere with the passage of time.

As described in "Prior Art", various methods of encapsulating or adhering an object to alginic acid gel spheres have been attempted, and the method can be applied to an alginic acid-soluble salt aqueous solution or a meniscus-shaped alginic acid-soluble salt aqueous solution in a template. Is known (Solimon et. Al., In Synsee
ds p40, Ed. by K. Redenbaugh, CRC Press (1993),
(RE Garret, JJ Mehlschau, NE Smith, M.
K. Redenbaugh, Applied Engineering in Agriculture 7
(1), 25-31 (1991)). Similar methods can be used to attach or encapsulate objects in the pre-cured droplets. In particular, when an object is attached to the surface of the gel sphere, impact is less likely to be applied in the dipping step in the curing liquid, and the adhered object is less likely to be separated from the gel sphere, as compared with the conventional method. found.

The above steps can be carried out by using a simple droplet supply device, preferably a support having water repellency, and a curing tank corresponding to the support. Further, since droplets can be formed at many points on the support at the same time without the need to create a large number of complicated nozzles or the like, it is also promising as a development principle of a mass production apparatus.

Here, "problems to be solved by the invention"
The new method for making alginate gel spheres was completed.
That is, when an algin droplet on a water-repellent support is immersed in a curing bath, it uses a mechanism of leaving the support to form a gel sphere, which has been complicated in the past. An inexpensive and efficient method of forming gel spheres after encapsulating or adhering an object on a support without using such a nozzle was obtained.

Hereinafter, the present invention will be described in detail. The alginic acid-soluble salt used is not particularly limited, but examples thereof include sodium alginate and potassium alginate. The concentration of the alginic acid-soluble salt aqueous solution is not particularly limited as long as it is within the range capable of forming gel spheres. For example, in the case of sodium alginate whose viscosity at the time of preparation of 1% concentration is 450 to 500 cp, it is 0.5 to 5.0%. can do. It is also possible to add various powders or dispersible substances as described in JP-A-3-218303 to the alginic acid-soluble salt aqueous solution.

The method of supplying the droplets of alginic acid is not particularly limited, but for example, when an accurate supply amount is expected, the supply from a nozzle is preferable. These nozzles can be arranged in a line at regular intervals or can be two-dimensionally arranged at regular intervals. The supply control of the liquid droplets can be optimally set by using a metering pump or a solenoid valve. With the above-mentioned alginic acid-soluble salt aqueous solution, the time required to supply one liquid droplet is 0.3 to 2 seconds.

The droplets are first dropped on the support. At this time, the material of the support is not particularly limited, but it is preferably water-repellent. Examples of the water-repellent treatment include a treatment with Teflon (DuPont) or a surface modifier such as a commercially available waterproof spray [eg, Scotchguard (Sumitomo 3M)]. You can

The shape of the support is not particularly limited as long as it does not interfere with adjacent droplets. For example, a flat plate, a flat plate having a round bottom concave surface at the drop position of the liquid drop, or the like can be used. Is. In the case of a flat plate having a round bottom concave portion, it is possible to stably hold the droplet of the alginic acid-soluble salt aqueous solution by dropping it on the concave surface. Further, a flat plate having "a hole that does not allow an aqueous solution of an alginic acid-soluble salt to pass" in the concave portion of the flat plate having the round bottom concave portion can also be used. Here, the "pores to the extent that the alginic acid-soluble salt aqueous solution does not pass" refers to pores having a pore size that does not allow the alginic acid-soluble salt aqueous solution to pass therethrough in the absence of pressure. By providing such holes, it is possible to inject / suck droplets of the aqueous solution of alginic acid-soluble salt through the holes, and by making the holes negative pressure, the droplets are dropped while adsorbing granules such as somatic embryos and seeds. can do.

It is also possible to use a water repellent mesh plate instead of the flat plate. The mesh may have a mesh size such that droplets do not drop, and generally, a mesh having a size of 2 mm or less can be used, for example, a mesh having a mesh size of 1 mm can be used. When the mesh plate is used, the penetration of the hardening liquid occurs quickly, so that a gel sphere closer to a true sphere can be obtained. Further, if the mesh plate is left as it is at the bottom of the curing tank during the curing time, it can be used as it is for collecting the gel spheres after the curing is completed.

It is also possible to use a belt wound and stretched around two or more rollers. At this time, the belt is preferably made of a material having both elasticity and water repellency, and for example, a water repellent treated silicone rubber or a water repellent stainless wire net is suitable.

Also, an object can be enclosed or attached to the droplet on the support. The object here is not particularly limited, but is preferably a solid. There is no limitation on the material or shape, but a material that is extremely hydrophobic is not suitable because it jumps out from the droplets before being dropped in the curing tank. Encapsulation refers to a state in which the gel spheres are completely embedded, and adhesion refers to a state in which at least a part thereof is exposed. For example, as an example of the attachment, a cultured plant body (major axis 6 mm) is placed on a droplet to obtain a cultured plant body-gel sphere having a shape in which the cultured plant body is partially buried. The method of supplying these objects is not particularly limited,
Many already known supply methods can be used.

Droplets (or objects-formed on the support)
The droplet complex) is immersed together with the support in the curing liquid in the curing bath. The curing liquid is contacted with an alginic acid-soluble salt aqueous solution,
Any insoluble salt may be formed, for example, 25 to 1,
A 000 mM calcium chloride solution can be used. The curing tank is preferably set according to the size of the support. Immersion of the support in the curing liquid can be performed relatively quickly. A few seconds after the immersion, the alginic acid droplets are released, and the support can be immediately recovered.
The gel spheres thus formed are placed in a curing tank for 1 second to 60 minutes, preferably 5 to 30 minutes as in the ordinary gel sphere preparation step, and then washed with water or the like to remove excess curing liquid. It can be obtained as a final product through a washing process. The recovered support can be reused after washing to remove the curing agent, and if necessary water-repellent treatment. When carrying out continuous production using a belt or the like, it is desirable to incorporate washing and water repellency recovery steps.

[0020]

The following examples show preferred embodiments of the present invention, and should not be understood as limiting the scope of the present invention.

[0021]

【Example】

[Example 1] About 200 μl of 1.5% sodium alginate solution (NS, manufactured by Kibun Food Chemifa Co., Ltd.) using a fraction collector (SF-2120 manufactured by Advantech)
(PH) water-repellent treated with a commercially available waterproof spray (Sumitomo 3M Scotch Guard) on a polyacrylic plate (20 x 30)
cm) to obtain 100 uniform droplets. 5 this plate
A water tank (25 x 35) containing 00 ml of 100 mM calcium chloride solution
X 5 cm). The droplets were immediately released and left in a curing tank for 10 minutes and then washed with tap water to obtain 100 homogeneous alginate gel spheres. The flat plate was collected immediately after immersion, washed, dried, and reused.

[Example 2] The same gel spheres as in Example 1 could be obtained by using a water repellent stainless steel wire mesh having a mesh size of 1 mm instead of the flat plate. The wire net was placed in the curing bath during the curing time and used as it was for the recovery of the gel spheres. The shape of the obtained gel sphere was close to a true sphere.

[Example 3] In the method of Example 1, a culture plant having an average shape of 7 mm in major axis and 3 mm in thickness was placed on a droplet on a flat plate, and then immersed in a hardening tank. After 10 minutes of curing and washing with water, a plant-gel sphere complex was obtained in which about half of the plant was exposed.

Example 4 A water repellent rubber belt 3 was wound and stretched by using four rollers 2 under a group of droplet supply nozzles 1 arranged in a line (FIG. 2). The droplets formed by the nozzle 1 were sent to the curing tank 4 on the belt 3, and the droplets themselves were released in the curing tank 4 to form gel spheres. The belt 3 was lifted from the curing tank 4, washed with water and dried to form droplets again.

[Embodiment 5] A water repellent wire mesh belt is formed by using a roller 2 under a group of droplet supply nozzles 1 aligned in a row.
3'was wound and stretched (Fig. 3). The droplets formed by the nozzle 1 were sent to the curing tank 4 on the belt 3 ′, and the droplets themselves were released in the curing tank 4 to form gel spheres. Belt 3 '
After collecting the hardened gel spheres, they were taken out of the hardening tank 4, washed with water and dried to form droplets again.

[0026]

INDUSTRIAL APPLICABILITY According to the present invention, alginic acid gel spheres can be prepared by a simple operation, and an object can be easily enclosed in gel spheres, which is generally difficult by the conventional method.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a method for producing gel spheres of the present invention.

FIG. 2 is a view showing an apparatus for continuously producing gel spheres using a water repellent belt as a support.

FIG. 3 is a view showing an apparatus for continuously producing gel spheres using a wire mesh belt as a support.

Claims (7)

[Claims] 1. A method for producing alginic acid gel spheres, which comprises depositing droplets of an aqueous solution of an alginic acid-soluble salt on a support and immersing the droplets together with the support in a curing solution. 2. The method for producing alginate gel spheres according to claim 1, wherein a water-repellent support is used. 3. The method for producing alginate gel spheres according to claim 1, wherein the support is a flat plate. 4. The method for producing alginate gel spheres according to claim 1, wherein the support is a mesh plate. 5. The method for producing alginate gel spheres according to claim 1, wherein the support is a flat plate having a round bottom concave surface. 6. The method for producing alginic acid gel spheres according to claim 5, wherein the concave surface has pores to the extent that an aqueous solution of an alginic acid-soluble salt does not pass through. 7. A method of depositing a droplet of an alginic acid-soluble aqueous solution on a support, enclosing or attaching an object to the droplet, and then immersing the droplet together with the support in a curing liquid. A method for producing an alginate gel sphere in which an object is enclosed or attached.