JPH01266185A - Ice nucleus-forming agent - Google Patents

Abstract

PURPOSE:To attain an improvement in the safety while maintaining an ice nucleus activity and avoiding direct contact of an ice nucleus-forming material with the skin, by microencapsulating said material. CONSTITUTION:An ice nucleus-forming material is obtd. by culturing an ice nucleus-forming bacterium (e.g. Erwinia herbicola). This material is mixed with a soln. of a natural polymer (e.g., sodium alginate) and sprayed into a coagulant soln. so as to effect coagulation. Thus, an ice nucleus-forming agent comprising a microencapsulated ice nucleus-forming material as a core material is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an ice nucleating agent that is safe and highly effective.

[Prior art]

In recent years, biologically derived ice-nucleating active substances have been attracting attention. Among them, ice-nucleating active bacteria have attracted particular attention as a main source of ice-nucleating substances in the atmosphere and as a cause of plagiarism to plants.

The ice-nucleating active bacteria known to date include Pseudomonas syringe (Pseudomonas! 3yr).
ingae), Pseudomonas fluoreaens
), Xanthomonas campestris (
onaa campes-trta), Erwinia herbicola (grwi-nia herbicola)
), Erwinia ananas (Eirwinia
ananaa) etc. In addition to the bacteria mentioned above, ice-nucleating bacteria have been found one after another mainly among plant scrofula bacteria and pathogenic bacteria. Among the above bacteria, Pseudomonas fluorescens
a fluorasana) and Erwinia +
All bacteria other than Erwinia herbicola are known as plant pathogens.

Traditionally, research has focused on techniques to suppress the activity of ice-nucleating bacteria in order to prevent frost damage to crops, but in recent years research has begun to utilize their excellent ice-nucleating activity.

In addition to snow making materials using artificial snow machines and food freezing media, applications for this technology include artificial climate control, cooling and heat insulation, heat storage, frozen desserts, etc., and research has already begun and some have been put into practical use. Some have been.

As a practical example of the use of ice-nucleating bacteria, there is a material for artificial snow machines that is commercially available in the United States. This is Pseudomonas syringa
e) The freeze-dried bacterial cells are suspended in water and introduced into an artificial snow machine when used. Therefore, the bacterial bodies themselves become ice nuclei and are directly dispersed onto the slopes.

As mentioned above, Pseudomonas syringe (Paeudo
Monas syringae) is a plant pathogenic bacterium, so when snow made with these fungi as ice nuclei melts on the surface of plants and the fungi settle there and multiply, it may cause harm to plants.

In addition, there is a possibility that the snow that is formed on the skin of a snow machine operator or a skier on the slopes using these bacteria as ice cores will melt, and the bacteria may come into direct contact with the skin. of course,
Pseudomonas syringe
syringae) and other ice-nucleating bacteria are ubiquitous in the natural world, including the atmosphere, so it is unlikely that they will directly cause illness in humans, but they may cause discomfort to workers and skiers. , causing a feeling of anxiety.

Similar problems can occur when utilizing ice-nucleating bacteria in natural environments. Also, the issue of skin contact is
As long as we consider its application to things directly used by humans, we must consider that it occurs.

[Means and structure for solving the problems] The present invention provides ice nucleation by microcapsulating an ice nucleation substance, thereby retaining ice nucleation activity and eliminating the need for the substance to come into direct contact with the skin. This solves the problem that even when ice-nucleating active bacteria are used as a forming substance, the bacteria colonize and multiply on plants.

Here, the ice nucleating material used as the stone material for the microcapsules can be selected as appropriate depending on the intended use of the ice nucleating material. , organic substances derived from living organisms may be used. However, when used in the natural environment, biodegradable substances are desirable in order to prevent environmental contamination by ice nucleating substances, so ice nucleating bacteria or their products are most effective.

When ice-nucleating bacteria or their products are used as stone materials, living cells of ice-nucleating bacteria and their freeze-dried products, cells that have been sterilized by some method and their freeze-dried products, as well as crushed bacterial cells and If the ice nucleus active site exists in a state □ that retains its activity, such as in the freeze-dried product,
It can be in any shape or form.

Also, depending on the type of bacteria, is it an ice nucleus active substance? Since some substances are released into the culture solution, in this case, the ice nucleating active substance released into the solution and its lyophilized product can be used. Among these, bacterial cells that have lost their ability to proliferate in some way,
Products that do not have the ability to proliferate on their own, including crushed bacterial cells, will not proliferate there even if the wall material of the microcapsule is decomposed or destroyed and released directly into the outside world, and on the contrary, other bacteria will not proliferate there. It is the most suitable core material when used in the natural environment.

On the other hand, the material for the microcapsules is selected depending on the manufacturing method of the microcapsules. Methods for producing microcapsules are broadly classified into chemical methods, physicochemical methods, and physical/mechanical methods. Any method can be used to produce the ice nucleating agent of the present invention as long as it does not cause the ice nucleating activity of the ice nucleating substance used as the stone to be lost. In other words, it is necessary to select a production method that does not cause ice-nucleating active bacteria.

Furthermore, the development goal of this ice nucleating agent is to separate the ice nucleating active material, which is stone, from the outside world, and at the same time utilize its ice nucleating ability. It must have pores large enough to be impermeable and allow water to pass through.

Examples of enzyme immobilization methods that require similar functionality include enzyme immobilization methods, especially entrapment methods. The entrapment method is generally divided into the lattice type, in which the enzyme is injected into a fine gel lattice, and the microcapsule type, in which the enzyme is covered with a semipermeable polymer film, but the lattice type also has different manufacturing methods. can be considered a type of microcapsule.

As the material for the microcapsule type, there are cases where non-biopolymers are used and biopolymers are used. Examples of the former include polyamide, polyurea, phenylsiloxane ladder polymer, polyfvn, ethylcellulose, collodion, nitrocellulose, Cellulose phthyl acetate. In addition, for lattice-type materials, that is, microcapsules, the materials include polyacrylic acid, polyacrylamide, polyethylene glycol methacrylate, polyvinyl alcohol, photocurable resin, urethane polymer,
Silicone resins such as cellulose acetate, starch, konjac powder, gelatin, agarose, chitosan, di-carrageenan, Ca-alginic acid, Ca-pectin, and fibrin are used.

Any of these materials can be used as the material for the microcapsules for the purpose of producing the present ice nucleating agent, as long as the stone does not lose its ice nucleating activity as described above.

The material of the ice nucleating agent microcapsule is also selected depending on its use. That is, if it is desired that the shape of the microcapsules be maintained for a long period of time, a material that is physically, chemically, or biologically stable must be selected. Furthermore, in cases where it is undesirable for the material to remain for a long period of time, such as in the natural environment, it is necessary to select a biodegradable material. A synthetic polymer can be used as the former, and a natural polymer can be used as the latter. Natural polymers include cellulose derivatives, starch, konjac flour, gelatin, agarose, chitosan, carrageenan, alginic acid, pectin, fibrin, etc., and polysaccharides produced by microorganisms, such as dextran, pullulan, curdlan, etc. can also be used.

When the ice nucleating agent of the present invention is used in a natural environment, it is desirable that neither the stone nor the microcapsule material remain for a long period of time. Therefore, the most suitable combination is ice-nucleating bacteria or their products as stone materials and natural polymers as wall materials.

The actual columns are shown below.

[Real ift row] Bacterial culture Erwinia + Herbicola (FJrwinia he
rbi-cola)17012686'i table-
The cells were cultured with shaking at 15° C. for 3 days in a liquid medium having the composition shown in 1. Centrifugation (8000F, 20 minutes,
Bacteria were collected at 4°C) and washed twice with a 1% sodium chloride solution. The washed bacterial cells were washed out with 175M sucrose-10mM) Lis-Hat mild tit (pH 7.5) and disrupted using French V solution. Undestroyed bacteria were removed by centrifugation, and the supernatant was collected.

Table-1 Composition of medium Supernatant 25- and 15% sodium alginate solution 100-
were mixed and introduced into the spray equipment. The sprayed fine particles were placed in a 15M calcium chloride solution to gel alginic acid as a calcium salt to create microcapsules. The prepared microcapsules were collected, washed twice with pure water, and then suspended in 100% deionized water. All of the above operations were performed at 20°C or lower.

Assay of ice nucleus activity Using a device that can cool the surface while lowering the temperature over time, 50 drops of 1 μL each of the above microcapsule suspension were placed on the metal plate on the top of the device, and 50 drops of 1 μL each of deionized water were added as a control.
0 drops were arranged and cooled. The time from the start of cooling until all 50 drops were frozen was recorded. The results are shown in Figure 4. As is clear from FIG. 1, the present ice nucleating agent has a submerged ice nucleating ability.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the cooling time and freezing rate of droplets and water droplets of the microcapsule suspension of the present invention.

Claims (1)

[Scope of Claims] 1. An ice nucleating agent comprising microcapsules containing an ice nucleating substance as a core substance. 2. The ice nucleating agent according to claim 1, wherein the ice nucleating substance is an ice nucleating bacterium or a product thereof.