JP2006006211A - Sterilization method and apparatus for feed creature - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sterilization method and a sterilization apparatus each sterilizing feed creatures cultured under the natural environment without synthetic antibacterial drug or chemical agent just before giving to seeds of fish and shellfish. <P>SOLUTION: This sterilization apparatus 1 is based on the sterilization method for the feed creatures comprising irradiating ultraviolet rays toward the water surface of an aqueous solution in which the feed creatures float so as to sterilize harmful bacteria which the feed creatures floating in the aqueous solution hold. The sterilization apparatus 1 is composed of a storing container 12 storing an aqueous solution in which the feed creatures float, an ultraviolet ray irradiating part 14 irradiating ultraviolet rays toward the water surface 122 of the aqueous solution 121 which the storing container 12 stores, an apparatus main body 11 holding the storing container 12 and the ultraviolet ray irradiating part 14 in prescribed positional relationship and a control part 16 operating and stopping the ultraviolet ray irradiating part 14. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sterilization method for sterilizing harmful bacteria that contaminate feed organisms used in fish and shellfish seedling production, and a sterilization apparatus used in the sterilization method.

Feeding organisms such as rotifers or artemia are used for seedling production of seafood. For example, rotifers, which are feed organisms, are contaminated with harmful bacteria reaching 10 ⁸ CFU / g and may be a vector of pathogenic bacteria to seedlings. Thus, various methods for sterilizing harmful bacteria that contaminate food organisms have been proposed. Specifically, refrigeration methods and sterilization methods using various bactericides are known. Here, since the freezing method kills the feed organism itself, it is not so popular because of the problem of lowering the feed value of the feed organism. Currently, a sterilization method using a bactericidal agent is widely used.

  As a bactericidal method using a bactericidal agent, a method of immersing a feed organism in an aqueous solution in which sodium niflustyrate (NFS) which is a synthetic antibacterial agent is dissolved is widely used. Patent Document 1 proposes culturing a feed organism in the presence of an isothiazoline derivative that is not an antibiotic. In other words, until the feed organism is fed to the seafood seedling, it is prevented from being infected with harmful bacteria as much as possible to prevent contamination of the seafood seedling through the feed organism.

Japanese Patent Publication No. 10-507458 (pages 4-9, Fig. 1)

  There are the following problems in the method of sterilizing feed organisms using a bactericide. First, the daily use of NFS, a synthetic antibacterial agent, in feed organisms may lead to resistance of the feed organism to synthetic antibacterial agents. In addition, due to regulations of the Pharmaceutical Affairs Law, there are restrictions on the use of NFS, leading to a situation where a sufficient bactericidal effect cannot be expected. Furthermore, there is a problem that NFS administered to a feed organism accumulates in seedlings through the feed organism.

  In this regard, the sterilization method of Patent Document 1 using an isothiazoline derivative that is not a synthetic antibacterial agent has problems due to the acquisition of resistance to harmful bacteria and regulations of the Pharmaceutical Affairs Law, and isothiazoline derivatives that accumulate in seedlings through feed organisms. . In addition, it is not preferable to continue culturing a feed organism in the presence of an isothiazoline derivative, but if the effective concentration is lowered, there is a possibility that harmful bacteria are tolerated. Therefore, as a sterilization method for sterilizing prey organisms cultivated in a natural environment that does not use synthetic antibacterial agents or drugs just before giving them to seafood seedlings, sterilization equivalent to the case of using a disinfectant without using a disinfectant In order to develop a sterilizing method and a sterilizing apparatus that can obtain an effect, the present inventors have studied.

  What has been developed as a result of the study is a method for sterilizing feed organisms that sterilizes harmful bacteria possessed by the feed organisms floating in this aqueous solution by irradiating ultraviolet rays toward the water surface of the aqueous solution in which the feed organisms are suspended. . Although sterilization using ultraviolet rays is widely known, the present invention is characterized in that only harmful bacteria possessed by the feed organism are killed, that is, sterilized by irradiating the feed organism floating in an aqueous solution with ultraviolet rays. Have

  Ultraviolet rays have extremely low transmittance in water, and ultraviolet rays irradiated toward the surface of an aqueous solution only affect food organisms directly below the water surface. It is replaced complicatedly, and the sterilizing action of ultraviolet rays is applied to all feed organisms. Here, the ultraviolet ray bactericidal action works only on the bait organisms just below the water surface, and most bait organisms in the aqueous solution are not affected by the ultraviolet rays, so that the ultraviolet rays per individual bait organism can be suppressed. As a result, only harmful bacteria can be killed without affecting the feed organisms by ultraviolet rays. The bactericidal effect varies depending on the ultraviolet intensity, the amount of ultraviolet light, the amount of water in the aqueous solution, and the type and density of the feed organism, but harmful bacteria can be reduced in the range of about 1/10 to 1/1000.

  Ultraviolet rays are classified into A region ultraviolet rays (UV-A) having a wavelength of 320 nm to less than 400 nm, B region ultraviolet rays (UV-B) having a wavelength of 280 nm to less than 320 nm, and C region ultraviolet rays (UV-C) having a wavelength of less than 280 nm, Any ultraviolet ray can be used in the sterilization method of the present invention. However, generally, ultraviolet rays suitable for sterilization are C region ultraviolet rays, and ultraviolet lamps serving as ultraviolet light sources usually emit ultraviolet rays of 253.7 nm. Therefore, it is preferable to use C region ultraviolet rays in the present invention. Since the C region ultraviolet ray has the lowest transmittance in water in the ultraviolet ray, there is also an advantage that the bactericidal effect can be applied only to the feed organism just below the water surface.

In the sterilization treatment with ultraviolet rays, the intensity of ultraviolet rays influences the sterilization of harmful bacteria, and the amount of ultraviolet rays influences the influence on the feed organism. In the present invention, the effects of ultraviolet rays are kept on the water surface of the aqueous solution, and the whole living organism is sterilized by replacing the living organism just below the water surface by the activity or agitation of the living organism itself. Now, ultraviolet rays used in the present invention, ultraviolet intensity 50mW / cm ² ~150mW / cm ² at the water surface of the aqueous solution, preferably may be a ^{65mW / cm 2 ~135mW / cm 2} . If the UV intensity is weaker than 50 mW / cm ^2, it will not be able to exert sufficient bactericidal action against harmful bacteria possessed by underwater feed organisms, and a practical bactericidal effect cannot be obtained. In addition, if the ultraviolet intensity is higher than 150 mW / cm ² , sufficient ultraviolet rays reach a deeper depth than just below the surface of the water, which may cause an excessive amount of ultraviolet rays to feed organisms and kill them. When the ultraviolet intensity is in the above range, only the living organisms just below the water surface of the aqueous solution can be irradiated with ultraviolet rays, and the harmful organisms are not adversely affected by the ultraviolet rays, and only harmful bacteria can be killed.

Since the amount of ultraviolet rays influences the influence of ultraviolet rays on food organisms, an upper limit value needs to be determined. Specifically, the ultraviolet ray used in the present invention is when the feed organism is a rotifer, the amount of ultraviolet rays on the water surface of the aqueous solution is 5 mJ / cm ² at maximum per individual feed organism, and the feed organism is Artemia. In addition, the amount of ultraviolet rays on the water surface of the aqueous solution may be set to a maximum of 625 mJ / cm ² per one food organism. Since Artemia has an individual length of up to about 5 times that of a rotifer, the upper limit of the amount of UV light for Artemia is only 125 times the volume ratio, and the amount of UV light per volume is the same as the upper limit of the amount of UV light for a rotifer. It is.

  Since the ultraviolet ray amount is calculated from the ultraviolet ray intensity × irradiation time, when the ultraviolet ray intensity is set within the above range, the ultraviolet ray irradiation time is determined from the upper limit value of the ultraviolet ray amount. Since the bactericidal effect varies depending on the ultraviolet intensity, the amount of ultraviolet light, the amount of water in the aqueous solution, and the density of the feed organism, even if the measured amount of ultraviolet rays exceeds the above upper limit, the feed organism does not necessarily die. However, in order to kill only harmful bacteria without causing adverse effects of ultraviolet rays on the feed organism, it is desirable to irradiate ultraviolet rays with an ultraviolet ray amount equal to or less than the above upper limit value. In addition, since the sterilization effect depends on the amount of ultraviolet rays, the actual sterilization treatment may be, for example, a batch treatment in which ultraviolet light is applied to an aqueous solution in which food organisms are suspended in a storage container. Real-time processing in which ultraviolet rays are irradiated at a specific position may be used.

  In the sterilization treatment of the present invention, ultraviolet rays act only directly under the water surface of the aqueous solution, and the bait organisms directly under the water surface are replaced by the activity or agitation of the feed organisms themselves, so that all bait organisms are sterilized. Here, the fact that the feed organism is replaced by its own activity means that the feed organism is alive during the irradiation time of ultraviolet rays. The density of the feed organism in the aqueous solution is important for the survival of the feed organism, and the more the feed organism that can be sterilized at a time, the better. However, from the relationship with the survival of the feed organism, the density of the feed organism is in the following range. It is desirable to make it. That is, when the food organism is a rotifer, the sterilization treatment of the present invention is suspended in an aqueous solution at a density of 10,000 / mL to 200,000 / mL, preferably 30,000 / mL to 150,000 / mL. When the organism is Artemia, if it is suspended in an aqueous solution at a density of 1,000 individuals / mL to 20,000 individuals / mL, preferably 3,000 individuals / mL to 15,000 individuals / mL, food will be used for the duration of UV irradiation. Living organisms can survive, and feed organisms under the surface of the water can be replaced by their own activities.

  Since it is necessary to suspend a large amount of prey organisms in the aqueous solution for a certain irradiation time in this way, the aqueous solution can be exposed to seawater or osmotic pressure to seawater so that ultraviolet rays can be irradiated in the same state as in the natural environment as much as possible. A substantially equivalent saline solution may be used. Further, the aqueous solution can be actively replaced with the feed organism just below the water surface that is irradiated with ultraviolet rays by stirring together with the feed organism. In addition, the stirring of the aqueous solution has a function of supplying oxygen to the aqueous solution. From this, if the aqueous solution is sterilized while stirring, a high-density feed organism that is difficult to survive in an unstirred state can survive during the ultraviolet irradiation period.

  Based on the above sterilization method of the present invention, the sterilizer can be configured as follows. That is, a sterilization apparatus for sterilizing harmful bacteria held by a feed organism, a storage container for storing an aqueous solution in which the feed organism floats, an ultraviolet irradiation unit for irradiating ultraviolet rays toward the water surface of the aqueous solution stored in the storage container, and the storage It is a bait organism sterilizer comprising a device main body that holds a container and an ultraviolet irradiation unit in a predetermined positional relationship, and a control unit that operates and stops the ultraviolet irradiation unit.

  As described above, sterilization with ultraviolet rays is only brought to the bait organisms just below the water surface, so that the wider the opening shape of the storage container that determines the shape of the water surface of the aqueous solution, the higher the sterilization efficiency. Moreover, it is preferable that there are many food organisms that can be treated at one time. However, if the water depth is too deep, there is a possibility that food organisms near the bottom of the water will not be replaced with food organisms immediately below the water surface. From this, it is desirable that the storage container has a shallow dish structure in which the opening is wide and the depth of the aqueous solution to be sterilized at one time is 15 cm or less, preferably 10 cm or less. Specifically, for example, a talai storage container having a depth of 15 cm and an inner diameter of 60 cm can be shown.

  The storage container may be fixed to the apparatus main body. In this case, if the storage container is provided with a discharge part of the aqueous solution on the bottom surface, the feed organism suspended in the aqueous solution is poured into the storage container together with the aqueous solution, and the feed organism that has been sterilized from the discharge part of the storage container together with the aqueous solution It can be discharged quickly. Conversely, when the storage container is detachable from the apparatus main body, the aqueous solution can be poured into and discharged from the storage container more easily. Also in this case, the storage container may be provided with a discharge part on the bottom surface.

  The ultraviolet irradiation unit can use various light sources that emit ultraviolet rays exhibiting a bactericidal effect, but is most simply composed of one or a plurality of ultraviolet lamps. Ultraviolet lamps can be broadly divided into straight tube types and light bulb types. In the case of using a plurality of straight tube type ultraviolet lamps, it is preferable to form the irradiation range covering the water surface by aligning the directions of the ultraviolet lamps in the range covering the water surface of the aqueous solution stored in the storage container. When a plurality of bulb-shaped ultraviolet lamps are used, the ultraviolet lamps may be arranged in a lattice pattern so as to cover the water surface of the aqueous solution stored in the storage container to form an irradiation range that similarly covers the water surface.

  In order to promote replacement of feed organisms existing just below the surface of the aqueous solution stored in the storage container, the aqueous solution may be stirred. In this case, it is conceivable to provide a stirring unit in the storage container itself. However, since the stirring unit has a drive source and a control unit, providing the stirring unit in the storage container may complicate the apparatus configuration. Therefore, the apparatus main body may be provided with a stirring unit that hangs down toward the storage container, and a control unit that operates or stops the stirring unit.

  The stirrer is not limited to the configuration as long as it can stir the aqueous solution stored in the storage container, and it is only required to be able to apply some motion to the aqueous solution. However, when a motion perpendicular to the water surface (vertical motion) is applied, the aqueous solution and the feed organism may be dissipated from the storage container. Therefore, it is preferable to apply a motion parallel to the water surface. More specifically, the stirring unit is preferably composed of a long member that rotates horizontally, and the long member is immersed in the aqueous solution stored in the storage container, and the aqueous solution is stirred in the swirling direction.

  The stirring unit composed of the horizontally swirling long member stirs the aqueous solution as the long member moves in parallel with the water surface in the aqueous solution. The shape of the long member is not limited and may be, for example, a rod, but preferably has a blade structure. The stirring unit made of a long member having a blade structure may be swung at a maximum of 120 revolutions / minute or less, preferably at a maximum of 100 revolutions / minute or less. Moreover, the number of long members is also free, and when using a some long member, the positional relationship of each long member is also free. The positional relationship of the long members is determined by the height in the vertical direction of each long member, the interval in the circumferential direction of each long member, and the protruding direction of each long member from the pivot axis.

  If the stirring unit remains immersed in the aqueous solution stored in the storage container, the operation of pouring or discharging the aqueous solution into the storage container is troublesome. Therefore, it is preferable that the stirring unit is provided in the apparatus main body so as to be movable up and down relative to the storage container, and the storage container is detachable from the apparatus main body. The raising and lowering of the agitating unit facilitates the carrying-in and carrying-out of the storage container that is detachable from the apparatus main body. Actually, since the storage container storing the aqueous solution is heavy, a wheel is provided at the bottom of the storage container, and the storage container can be attached to and detached from the apparatus body using rails in the loading and unloading directions provided in the apparatus body. It is good to make it.

  The sterilization apparatus of the present invention only needs to be able to sterilize harmful bacteria possessed by feed organisms, and the sterilization treatment may be performed in an open environment or a closed environment. From now on, the apparatus main body is configured from an ultraviolet irradiation unit with respect to the storage container or a frame body that holds the storage container in a predetermined positional relationship with respect to the ultraviolet irradiation unit so that the ultraviolet intensity during the sterilization treatment does not change. You can also. However, since ultraviolet rays may also affect the human body, the device body is a closed box with a door as a closed environment, and a storage container and an ultraviolet irradiation unit are built in the device body. It is desirable to do.

  The apparatus body in the closed environment may include a stirring unit that hangs down toward the storage container, and a control unit that operates or stops the stirring unit. As described above, the stirring unit is composed of a long member that rotates horizontally, and the storage container may be a bottomed cylinder having an inner diameter larger than the outermost diameter of the long member of the stirring unit. In this case, the stirring unit is provided in the apparatus main body so as to be movable up and down with respect to the storage container, and the storage container is detachable from the apparatus main body.

  According to the present invention, it is possible to sterilize food organisms cultivated in a natural environment on the verge of giving them to seafood seedlings. The sterilization method of the present invention can have a bactericidal effect that makes harmful bacteria equivalent to 1/10 to 1/1000 equivalent to a sterilization treatment using a drug, but remains in a feed organism like a bactericide, There is no risk of affecting the seedlings. Moreover, since the sterilization method of the present invention is relatively simple, it can be implemented, for example, by irradiating an existing ultraviolet lamp. Thus, the present invention provides a method for sterilizing a feed organism that realizes an effective sterilization effect safely and easily. Furthermore, in the sterilization treatment of the present invention using ultraviolet rays, the time until harmful bacteria grow again is longer than the sterilization treatment using a drug, that is, the sterilization effect is sustained.

  The sterilization apparatus of the present invention provides a dedicated apparatus for more efficiently performing the sterilization method. In particular, it facilitates the setting of the UV intensity and the UV dose appropriate for killing only harmful bacteria without killing the feed organism. This makes it possible to sterilize food organisms cultivated in a natural environment easily and in large quantities immediately before feeding them to seafood seedlings. Thus, the present invention has an effect of providing not only an effective sterilizing effect but also a sterilizing apparatus that can be used practically while realizing this sterilizing effect.

  Hereinafter, an example of a sterilizer according to an embodiment of the present invention will be described with reference to the drawings. 1 is a front view showing an example of a sterilizer 1 according to the present invention, FIG. 2 is a side view of the sterilizer 1, FIG. 3 is a plan view of the sterilizer 1, and FIG. FIG. 5 and FIG. 6 are perspective views corresponding to FIG. 4 showing a state in which the aqueous solution 121 is stirred by the stirring units 23 and 33 of different examples. For convenience of explanation, the illustration of the door 111 is omitted in FIG. 1, and the illustration of the side plate 112 is omitted in FIG.

  The sterilizer 1 of this example is a structure which irradiates the storage container 12 accommodated in the substantially sealed apparatus main body 11 by the ultraviolet irradiation part 14 from the upper direction as seen in FIGS. In addition, the apparatus main body 11 includes a support frame 15 in the lower part, and is movable by a caster 151 with a stopper provided on the support frame 15. In this example, as will be described later, the storage container 12 is taken in and out according to a rail 113 protruding forward from the apparatus main body 11. The support frame 15 increases the position of the apparatus main body 11 to make it easier to place the storage container 12 on the rail 113.

  The apparatus main body 11 is a rectangular parallelepiped box made of stainless steel plate, and a flip-up type door 111 is provided on the front surface. The door 111 is provided with an acrylic small window 114 for internal observation and a handle 115 that assists opening and closing. The ultraviolet rays used for sterilization in this example are C region ultraviolet rays having a wavelength of 253.7 nm emitted from the ultraviolet lamp 141 as will be described later, and are dangerous to the human body. Therefore, the apparatus main body 11 surrounds the ultraviolet radiation range. A substantially sealed structure is preferred. The C region ultraviolet rays are rapidly attenuated even if the material transmits visible light. Therefore, the ultraviolet rays do not leak to the outside through the acrylic small window 114 of the internal observation level. The internal observation acrylic window 114 is also provided on the side plate 112. The upper plate 116 of the apparatus main body 11 is provided with a drive unit 131 of the stirring unit 13, an ultraviolet irradiation unit 14, and a control unit 16 of the stirring unit 13.

  The ultraviolet irradiation unit 14 includes four ultraviolet lamps 141 provided with a reflector 142 made of a stainless steel plate. If the main body 11 has a horizontal section of about 80 cm in width and about 70 cm in depth, if a 20W general-purpose product is used for the ultraviolet lamp 141, four to six pieces can be arranged as shown in the figure. The entire area can be approximated to a substantially uniform irradiation plane.

  The reflection plate 142 has a function of reflecting the ultraviolet ray irradiated upward from the ultraviolet ray emitted from the ultraviolet lamp 141 and increasing the amount of ultraviolet ray toward the water surface 122 of the aqueous solution 121 stored in the storage container 12. ing. For this reason, as in this example, in addition to providing an individual reflector for each ultraviolet lamp, one reflector may be provided for the entire ultraviolet lamp. A reflector bent in the direction may be used.

  The all ultraviolet lamps 141 are mounted on the lower surface of a reference plate 17 made of stainless steel plate having a plan view outer shape substantially equal to the horizontal cross section of the apparatus main body 11, arranged at substantially equal intervals, and the reference plate 17 can be adjusted in height. By suspending from the inner surface of the upper plate 116, the distance from each ultraviolet lamp 141 to the water surface 122 of the aqueous solution 121 stored in the storage container 12 is adjusted. In this example, a base bracket 172 provided with a long hole 171 is suspended from the inner surface of the upper plate 116 of the apparatus main body 11, and a suspension bracket 174 is fastened with a thumbscrew 173 to an arbitrary position of the long hole 171 of the base bracket 172. Due to this, the reference plate 17 is suspended. Accordingly, if the fastening position of the suspension bracket 174 with respect to the base bracket 172 is changed, the height of the reference plate 17, and consequently the height of the ultraviolet lamp 141 can be adjusted.

  The height of the ultraviolet lamp 141 is the distance from the storage container 12 housed in the apparatus main body 11, and determines the ultraviolet intensity at the water surface 122 of the aqueous solution 121 stored in the storage container 12. Therefore, it is not necessary to readjust the height of the ultraviolet lamp 141 once the height adjustment has been completed, and it is desirable that the height of the ultraviolet lamp 141 is fixed so that the ultraviolet intensity does not change during the sterilization process. If it is desired to change the ultraviolet intensity during the sterilization treatment, the irradiation intensity of the ultraviolet lamp itself may be adjusted. Such adjustment of the irradiation intensity of the ultraviolet lamp can be realized by adjusting the voltage applied to the ultraviolet lamp by the control unit.

  The storage container 12 has a circular shape in plan view, and a pair of carrying handles 123 are provided symmetrically on the opening edge, and four resin wheels 125 are attached to the bottom surface 124 in parallel. This example illustrates a talai-like storage container 12 having an opening diameter of 60 cm and a depth of 15 cm so that the water depth of the aqueous solution 121 to be sterilized at one time is 10 cm or less. The apparatus main body 11 has a rail 113 corresponding to the wheel 125 protruding forward along the lower edge of the door 111, and the storage container 12 can be easily put in and out of the apparatus main body 11 with the wheel 125 mounted on the rail 113. When the storage container is fixed in the apparatus main body, the rail is not necessary. Further, the bottom surface 124 of the storage container 12 is formed in a mortar shape having a downward slope toward the center, and a discharge cock is provided as a discharge portion 126 at the center. The feed organism that has been sterilized is discharged from the discharge section 126 together with the aqueous solution 121 and collected.

  The rail 113 of the apparatus main body 11 on which the storage container 12 is placed has a drop-off prevention protrusion 117 that engages with the wheel 125 of the storage container 12 from the front, and a positioning protrusion 118 that engages with the wheel 125 of the storage container 12 from the rear. They are provided at specific positions in the main body 11, respectively. Furthermore, in this example, in order to fix the position of the storage container 12 with the wheel 125 hitting the positioning protrusion 118, the fixing lever 18 is attached to the apparatus main body 11 at a position opposite to the positioning protrusion 118 across the center of the storage container 12. Provided. The fixed lever 18 includes a base portion 181 erected from the bottom surface 119 of the apparatus main body 11 and an L-shaped lever plate 182 that is pivotally attached to the base portion 181 and can be raised and tilted. This lever plate 182 does not hinder the movement of the storage container 12 according to the rail 113 in the tilted state shown in FIG. 2, and hits the outer surface of the storage container 12 carried into the apparatus main body 11 in the standing state shown in FIG. The storage container 12 is clamped together with the protrusion 118 to fix the position. The fixed position of the storage container 12 prevents the storage container 12 from being displaced due to the movement of the aqueous solution 121 stirred by the operation of the stirring unit 13.

  The agitating unit 13 descends from above with respect to the storage container 12 housed in the apparatus main body 11 and is immersed in the aqueous solution 121 stored in the storage container 12 to stir the aqueous solution 121 by swirling. The stirring unit 13 of this example is a pair of long members that project point-symmetrically from a rotating shaft 132 that passes through the upper plate 116 and the reference plate 17 from the driving unit 131 provided on the upper plate 116 of the apparatus main body 11. It consists of the feather 133 which is. For example, as shown in FIG. 4, the stirring unit 13 turns the blade 133 at an elevation angle to push the aqueous solution 121 downward from the water surface 122 toward the bottom of the water. The aqueous solution 121 stored in the storage container 12 is agitated not only by the blade 133 moving in the water but also by being pushed down from the water surface 122 to the water bottom caused by the blade 133. As a result, the feed organism floating in the aqueous solution 121 is also agitated, and in particular, the replacement of the feed organism just below the water surface is promoted.

  Here, when the stirring unit 13 made of a long member such as the blade 133 turns horizontally, the locus of the tip of the long member becomes circular. For example, if the storage container is square in plan view, stagnation occurs at each corner. There is a fear. From this, for the stirring unit 13 that horizontally swivels the long member such as the blade 133, the talai-shaped storage container 12 having a circular outer shape as in this example is preferable, and when the outer shape is a polygon in plan view, Is a pentagon or larger than 90 degrees.

  The drive unit 131 is an electric motor, and is attached to a table 135 that can be raised and lowered according to a guide shaft 134 erected on the upper plate 116 of the apparatus body 11. The operation of the drive unit 131 or the stop and control of the output rotation speed are also performed by the control unit 16 provided on the upper plate of the apparatus main body 11. The number of rotations output by the drive unit 131 is desirably wide so that it can be set as appropriate depending on the water depth of the aqueous solution 121 and the maximum outer diameter of the stirring unit 13, for example, a stirring unit comprising a pair of blades 133 having an outer diameter of about 40 cm In the case of 13, it is good to be able to output the number of rotations at a maximum of 100 rpm. The maximum number of revolutions is determined as long as the aqueous solution does not scatter from the storage container during the stirring, based on the specifications of the stirring unit, the amount of the aqueous solution stored in the storage container, and the density of the feed organism.

  A table 135 that supports the drive unit 131 is screwed with a ball screw 137 provided with a handle 136, and moves up and down with respect to the ball screw 137 by operating the handle 136. That is, by operating the handle 136, the drive unit 131 can be moved up and down, and the stirring unit 13 connected by the drive unit 131 and the rotating shaft 132 can be moved up and down. By raising and lowering the stirring unit 131, the stirring unit 13 can be retracted upward when the storage container 12 is carried into the apparatus main body 11. The raising and lowering of the stirring unit can be automated by driving a ball screw with an electric motor, for example.

  The stirring unit 13 of the present example is composed of a pair of blades 133 projecting point-symmetrically. However, the purpose is not to generate a separate lifting force, and the number of blades is arbitrary as long as the aqueous solution 121 can be stirred. For example, the stirring unit may be configured with one blade, or as illustrated in FIG. 5, the stirring unit may be configured with four blades 231 protruding at equal intervals in the circumferential direction. Moreover, if the stirring part of this invention is an object which moves in the aqueous solution, it can stir the aqueous solution and can promote the replacement of food organisms immediately below the water surface. From this point, as shown in FIG. 6, the stirring unit 33 may be constituted by a pair of rods 331 protruding symmetrically in place of the blades.

  The procedure of the sterilization process will be described according to the sterilization apparatus 1 of this example. First, the storage container 12 filled with the aqueous solution (seawater) 121 in which the feed organism is suspended is placed on the rail 113 of the apparatus main body 11 opened by lifting the door 111. The aqueous solution 121 may be put into the storage container 12 previously placed on the rail 113 from another container. At this stage, the drive unit 131 is raised by operating the handle 136, and the stirring unit 13 is retracted in the vicinity of the ultraviolet irradiation unit 14. Since there is no obstacle in the apparatus main body 11, the storage container 12 can be loaded into the apparatus main body 11 so as to be pushed in. Then, when the wheel 125 of the storage container 12 hits the positioning protrusion 118, the lever plate 182 of the fixing lever 18 is raised to fix the position of the storage container 12, and then the door 111 is closed, the stirring unit 13 is lowered, and the storage container is lowered. Immerse in the aqueous solution 121 in which 12 is stored. At this time, the storage container 12 and the stirring unit 13 may not be completely concentric, but in this example, by applying the wheel 125 to the positioning projection 118 on the rail 113, the stirring unit 13 and the storage container 12 Are concentric. Thereby, the stirring of the aqueous solution 121 by the stirring unit 13 is not biased, and the aqueous solution 121 can be stirred over the entire storage container 12.

  If the door 111 is closed and the stirring unit 13 is immersed in the aqueous solution 121 of the storage container 12, then the ultraviolet irradiation unit 14 is operated, and the stirring unit 13 is swung horizontally to start sterilization. The ultraviolet irradiation unit 14 and the stirring unit 13 may be operated or stopped independently, or may be operated or stopped integrally. The operation time of the ultraviolet irradiation unit 14 or the stirring unit 13 may be set by a timer. Here, the ultraviolet irradiation unit 14 only needs to operate during the processing time of the sterilization process, but rather does not perform excessive ultraviolet irradiation, so it is desirable that it can be automatically stopped by a timer after a predetermined processing time has elapsed. On the other hand, the stirring unit 13 has the function of replacing the feed organisms directly below the water surface, and also has the function of taking oxygen into the aqueous solution 121 and preventing the death of the feed organisms in a high density state. It is preferable to operate after 14 stops. From this point, the ultraviolet irradiation unit 14 and the stirring unit 13 may be operated at the same time, but after the ultraviolet irradiation unit 14 is stopped by the timer, the stirring unit 13 is not stopped until the storage container 12 is taken out. It is good to keep.

  The UV intensity suitable for killing only harmful bacteria without killing the feed organism is the distance from the UV irradiation unit 14 to the water surface 122 of the aqueous solution 121 stored in the storage container 12, and the UV amount that does not adversely affect the feed organism It is determined by the irradiation time of ultraviolet intensity. Prior to the use of the sterilizer, the ultraviolet intensity is measured at a height corresponding to the water surface 122 of the storage container 12, and the height of the ultraviolet irradiation unit 14 may be adjusted in advance so as to obtain an appropriate intensity. Here, when the amount of the aqueous solution 121 stored in the storage container 12 is increased or decreased, the height of the water surface 122 changes as a result, and the ultraviolet intensity in the actual sterilization treatment can be finely adjusted. The amount of ultraviolet rays can be calculated a priori from the irradiation time of ultraviolet rays. According to the irradiation time determined in this way, the ultraviolet irradiation unit 14 irradiates ultraviolet rays for a predetermined time according to a timer.

  When the control unit 16 stops the ultraviolet irradiation unit 14 after a predetermined operating time has elapsed by the timer, the sterilization process ends. The end of this sterilization process is, for example, turning off the operation lamp of the ultraviolet irradiation unit 14 provided in the control unit 16 or turning on the stop lamp, as well as the ultraviolet rays in the apparatus body 11 from the acrylic small window 114 provided in the door 111 or the side plate 112. This can be confirmed by watching the lamp 141 turn off. The agitation unit 13 is preferably operated in order to continue supplying oxygen until the feed organism is recovered. As will be described later, in the sterilization treatment according to the present invention, it is not necessary to collect the feed organism immediately after the sterilization treatment because the time until the harmful bacteria grow again is long, that is, the duration of the sterilization effect is long. This is an advantage in that it is not necessary to keep an operator involved in the sterilization process.

  The feed organism first stops the agitation unit 13 and then raises the agitation unit 13 by operating the handle 136 to retract from the storage container 12, and then collects it from the storage container 12 that has been opened by opening the door 111. Since the storage container 12 of this example is provided with a discharge cock as the discharge part 126 on the bottom surface 124, for example, from the storage container 12 pulled out on the rail 113, the feed organism is collected together with the aqueous solution from the discharge part to another container. May be. This is a case where the storage container is used repeatedly without replacement. Further, the storage container 12 may be carried out as it is to collect the feed organism. This is suitable for a case where there are a plurality of storage containers and the next sterilization process is performed immediately after the previous sterilization process is completed.

  The amount that can be sterilized at once by the sterilization apparatus of this example is determined by the amount of the aqueous solution and the density of the feed organism. For example, when the aqueous solution 121 having a depth of 10 cm is stored in the above-mentioned talai-shaped storage container 12 having a diameter of 60 cm and a depth of 15 cm, rotifers as a feed organism are suspended in the aqueous solution 121 at a density of 100,000 individuals / mL. Quantity: 30cm x 30cm x π x 10cm = 28274mL) x (Rotifer density = 100,000 individuals / mL) = 2,827.4 million individuals, ie about 3 billion individuals, about 1/10 to 1/1000 harmful bacteria Can be sterilized. This is comparable to the amount of rotifer needed per day in small to medium sized farms.

  In order to confirm the effectiveness of the sterilization treatment of the feed organism according to the present invention, the following experiment was conducted on a rotifer as a typical feed organism.

Experiment 1: Effect of ultraviolet rays on rotifers It is meaningless if rotifers themselves are killed by irradiating them with ultraviolet rays. First, how much ultraviolet rays are irradiated to rotifers, It confirmed about the upper limit of the amount of ultraviolet rays. The experimental conditions are as follows. A plastic shallow petri dish with an inner diameter of 90 mm, which is a storage container, was filled with seawater (water temperature 20 ° C.) as an aqueous solution at a depth of 3 mm, and rotifers were suspended in this aqueous solution at a density of 100 individuals / mL. The water depth of the aqueous solution is a depth at which the activity of the rotifer itself is sufficiently guaranteed and the rotifer just below the water surface can be replaced. In Experiment 1, the aqueous solution was not stirred.

As the ultraviolet rays, two 15W ultraviolet lamps (CL-15 manufactured by Toshiba) were used, and the distance to the water surface of the aqueous solution was set to 19.5 cm. This ultraviolet lamp was irradiated with C region ultraviolet rays, and the ultraviolet intensity at the water surface of the aqueous solution was 65.1 mW / cm ² . The ultraviolet intensity is a value measured with an ultraviolet intensity meter (UVR-254, manufactured by Tokyo Optical Machinery Co., Ltd.) at a position away from the ultraviolet lamp in accordance with the distance from the ultraviolet lamp to the water surface.

  The effect of ultraviolet rays on rotifers is due to the observation of rotifers from the start of ultraviolet irradiation. Although a slightly dead rotifer was observed until 2 minutes after the start of UV irradiation, the activity of the surviving rotifer itself was not different from that immediately after the start of UV irradiation. Here, the death of a rotifer is also related to the oxygen concentration in the aqueous solution, and cannot be determined as the influence of ultraviolet rays. However, 3 minutes have passed since the start of ultraviolet irradiation, and the number of active rotifers has drastically decreased. According to visual observation, approximately 80% of deaths have been confirmed. This is clearly considered to be the effect of ultraviolet irradiation.

In Experiment 1, the surface of an aqueous solution with a depth of 3 mm in which the rotifer floats was irradiated with ultraviolet light with an ultraviolet intensity of 65.1 mW / cm ² , and safety was confirmed with 2 minutes irradiation, and it was confirmed that rotifer was killed with 3 minutes irradiation. It was. In the case of 2 minutes irradiation, ultraviolet amount per rotifers one individual in 65.1mW / cm ² × 120 seconds /(4.5cm×4.5cm×π×0.3cm×100 individual /ML)=4.1MJ/cm ² is there. In addition, in the case of 3 min irradiation, ultraviolet amount per rotifers one individual is a 65.1mW / cm ² × 120 seconds /(4.5cm×4.5cm×π×0.3cm×100 individual /ML)=6.1MJ/cm ² .

From this, it is considered that the amount of ultraviolet rays that can be used in the sterilization method of the present invention is 5 mJ / cm ² per individual rotifer. Artemia, which is the same prey organism as rotifers, has an individual length that is up to about 5 times that of rotifers. Therefore, the upper limit of the amount of ultraviolet light for Artemia is 125 times the volume ratio, that is, 625 mJ / cm ² . It is considered to be. Since rotifers are the most utilized and small-sized feed organisms, by confirming the effects of ultraviolet rays on these rotifers, almost the same upper limit of the amount of ultraviolet rays according to the volume ratio is applied to all feed organisms. It is considered possible. Subsequent experiments UV dose was confirmed in this experiment 1, namely the one individual per 5 mJ / cm ² in the case of rotifers, in the case of Artemia was performed in a range not exceeding 625mJ / cm ^2.

Experiment 2: Sterilization of harmful bacteria possessed by rotifers by ultraviolet rays Next, ultraviolet rays are irradiated within the above upper limit for the amount of ultraviolet rays to rotifers, and ultraviolet rays are used to confirm whether harmful bacteria possessed by rotifers can be sterilized to a practical level. I decided to investigate the relationship between the irradiation time and the bactericidal effect. The experimental conditions are almost the same as in Experiment 1. A plastic shallow petri dish with an inner diameter of 90 mm, which is a storage container, was filled with seawater (water temperature 20 ° C.) as an aqueous solution at a depth of 3 mm, and rotifers were suspended in this aqueous solution at a density of 20,000 individuals / mL. The reason why the density of the rotifer was increased from Experiment 1 was that a more practical sterilization scene was assumed. In this experiment 2 as well, the rotifer just below the water surface is replaced by the activity of the rotifer itself, and the aqueous solution is not stirred.

For the ultraviolet rays, two 15W ultraviolet lamps (CL-15 manufactured by Toshiba) were used, and the distance to the water surface of the aqueous solution was set to 19.5 cm. This ultraviolet lamp was irradiated with C region ultraviolet rays, and the ultraviolet intensity at the water surface of the aqueous solution was 65.1 mW / cm ² . The ultraviolet intensity is a value measured with an ultraviolet intensity meter (UVR-254, manufactured by Tokyo Optical Machinery Co., Ltd.) at a position away from the ultraviolet lamp in accordance with the distance from the ultraviolet lamp to the water surface.

  The bactericidal effect is determined by measuring the number of harmful bacteria before ultraviolet irradiation (irradiation time 0 minutes) and the number of harmful bacteria at the stage of irradiation for 1, 2, 4, and 6 minutes from the start of ultraviolet irradiation. Evaluation was based on the degree of decrease from the number of harmful bacteria before ultraviolet irradiation (irradiation time 0 minutes). Harmful bacteria are divided into Vibrio bacteria (hereinafter referred to as TCBS bacteria from the relationship with the medium) and other general bacteria, which are problematic in the production of seafood seedlings, and cultured on a plate medium. The number of bacteria per 1 g of rotifer (CFU / g) was calculated from the number of colonies grown on the plant.

  The specific number of bacteria is calculated according to the following procedure. Before irradiation, each 1-minute and 2-minute irradiated rotifer is transferred together with the aqueous solution to a plankton net having a mesh size of 42 μm, washed with seawater, and excess water is removed from the back side of the plankton net using filter paper or the like. Next, a part of the rotifer (0.1 to 0.2 g) adhering to the plankton net is taken to a glass homogenizer, accurately weighed, and then well ground with 2.0 mL of sterilized seawater. This ground rotifer is diluted 10-fold using sterilized seawater as dilution water, and 0.1 mL per plate is inoculated into the plate medium from each dilution stage. As the medium, TCBS agar medium (produced by Eiken), which is a selective medium for Vibrio bacteria, and ZoBell2216e agar medium generally used for separation culture of seawater or marine bacteria are used. After culturing each medium at 25 ° C. for 2 days, the number of colonies grown at an appropriate dilution stage is counted, and the number of bacteria contained in 1 g of rotifer is determined from the counting result, the initial weighing value and the dilution rate. .

The result of Experiment 2 is shown in FIG. The graph of the experimental results represents the CFU / g value as a logarithmic value for each of general bacteria (open circles) and TCBS bacteria (black circles). First, TCBS bacteria bacteria count was confirmed in ¹⁰⁷ order before irradiation, the 1/100 10 ⁵ order at the stage of irradiation 1 minute, about 1/1000 of 10 ⁴ orders less at the stage of 2 minutes irradiation It was confirmed that the number of bacteria was about 1/1000 or less than the order of 10 ⁴ even at 4 minutes and 6 minutes. In addition, general bacteria whose number of bacteria was confirmed to be on the order of 10 ⁹ prior to irradiation were about 1/10 of 10 ⁸ when irradiated for 1 minute, and about 10 ^{7 of} about 1/100 when irradiated for 2 minutes. a, 4 minutes 10 ⁷ order stage of about 1/100 of the irradiation, and it was confirmed that at the stage of 6 minutes irradiation of 10 ⁶ bacteria count on the order of about 1/1000. Here, the UV dose per rotifers 1 individual, 0.06MJ 1 minute 0.01 mJ / cm ^2, 2 minutes irradiation with irradiation ^{0.02mJ / cm 2, 0.04mJ / cm} 2 in 4 minutes irradiation, and 6 minutes irradiation / cm ² , both of which are much lower than the upper limit (5 mJ / cm ² ) of the amount of ultraviolet light obtained in Experiment 1, and actually the death of a rotifer was not confirmed. The bactericidal effect at which the number of bacteria is 1/1000 or less is equivalent to or better than the conventional bactericidal treatment. From this, it can be said that the sterilization treatment by ultraviolet irradiation according to the present invention has a sufficient sterilization effect that can be used in place of the conventional sterilization treatment with a chemical solution.

Experiment 3: Sustainability of bactericidal effect From the above Experiment 1 and Experiment 2, it was confirmed that the bactericidal treatment with ultraviolet rays has a bactericidal effect equivalent to or higher than that of the conventional bactericidal treatment. Here, it is known that the sterilization treatment with a medicine loses the sterilization effect in about 2 hours after the sterilization treatment, and harmful bacteria re-grow. Therefore, it was decided to examine the persistence of the bactericidal effect according to how long the bactericidal effect of the bactericidal treatment with ultraviolet rays lasts after the bactericidal treatment, that is, the degree of regrowth of harmful bacteria after the bactericidal treatment.

The experimental conditions are the same as in Experiment 2. A plastic shallow petri dish with an inner diameter of 90 mm as a storage container was filled with seawater (water temperature 20 ° C.) as an aqueous solution at a depth of 3 mm, and rotifers in this aqueous solution were suspended at a density of 20,000 individuals / mL. For the ultraviolet rays, two 15W ultraviolet lamps (CL-15 manufactured by Toshiba) were used, and the distance to the water surface of the aqueous solution was set to 19.5 cm. This ultraviolet lamp was irradiated with C region ultraviolet rays, and the ultraviolet intensity at the water surface of the aqueous solution was 65.1 mW / cm ² . The ultraviolet intensity is a value measured with an ultraviolet intensity meter (UVR-254, manufactured by Tokyo Optical Machinery Co., Ltd.) at a position away from the ultraviolet lamp in accordance with the distance from the ultraviolet lamp to the water surface.

  The persistence of the bactericidal effect is determined by measuring the number of harmful bacteria in a rotifer irradiated with ultraviolet rays for 2 minutes in advance, and the bacteria after 2 hours, 4 hours and 6 hours after returning to seawater after sterilization treatment. It was evaluated by measuring the number and confirming the increasing tendency of harmful bacteria. From the end of the sterilization treatment until 6 hours after the final sterilization count, the seawater changed in the range of 25.3 ° C to 26.6 ° C, which is a normal change linked to the outside air temperature. The harmful bacteria are TCBS bacteria and other bacteria that are a problem in the production of seafood seedlings, and the measurement method was the same as in Experiment 2, and each was cultured on a plate medium, and the number of bacteria was calculated from the number of colonies grown on each medium. .

The result of Experiment 3 is shown in FIG. The graph of the experimental results represents the CFU / g value as a logarithmic value for each of general bacteria (open circles) and TCBS bacteria (black circles). Because of the same experimental conditions as in Experiment 2, TCBS bacteria, which were on the order of 10 ⁷ before the sterilization treatment, were on the order of 10 ^5, about 1/100 by 2 minutes of UV irradiation, and on the order of 10 ⁹ before the sterilization treatment. In addition, general bacteria have a bactericidal effect that is reduced to the order of 10 ^{8 of} about 1/10. This bactericidal effect was confirmed to have a persistence of at least 6 hours since the number of bacteria after 2 hours, 4 hours and 6 hours had hardly increased. The food organisms that have been sterilized are not all eaten immediately by the seafood seedlings after sowing, but can be eaten over about 6 hours. From this, it can be considered that the persistence of the bactericidal effect confirmed in Experiment 3 is a very effective bactericidal treatment in which harmful bacteria are less likely to be taken into the seafood seedlings.

  Thus, the reason why the sterilization effect of the sterilization treatment according to the present invention is sustained can be considered as follows. That is, the bactericidal effect of the bactericidal treatment with the drug not only kills harmful bacteria directly with the drug, but also has a function of suppressing the growth of harmful bacteria due to the presence of the drug. On the other hand, the sterilization effect of the sterilization treatment by ultraviolet rays not only kills harmful bacteria directly by ultraviolet rays, but also has the function that ultraviolet rays damage harmful bacteria's DNA and suppress regrowth or take time to regrowth. Conceivable. That is, the DNA breakage is linked to the persistence of the bactericidal effect. For this reason, the germicidal treatment with ultraviolet rays makes it easier to suppress the regrowth of harmful bacteria.

Experiment 4: Sterilization effect by stirring Next, in order to confirm whether or not the sterilization treatment by ultraviolet rays is practical, it was tested how many food organisms could be sterilized by ultraviolet rays at a time. The feed organisms are sterilized before being given to the seafood seedlings. Since the amount of feed organisms given to the seedlings is very large, it is desirable that a large amount of feed organisms can be sterilized in as short a time as possible. Therefore, in this experiment 4, a much larger amount of rotifer was sterilized by using the irradiation time for obtaining the sterilization effect equivalent to that of experiment 2 as a guide.

The experimental conditions are almost the same as in Experiment 2 except that the amount of aqueous solution is increased to increase the density of the feed organism in order to increase the amount of the feed organism. A glass deep petri dish having an inner diameter of 107 mm, which is a storage container, was filled with seawater (water temperature 25.7 ° C.) as an aqueous solution at a water depth of 45 mm, and rotifers in this aqueous solution were suspended at a density of 45,000 individuals / mL. From this, the amount of rotifers to be sterilized at a time in Experiment 4 is about 12 million individuals, which is 30 times or more of about 380,000 individuals in Experiment 2 or Experiment 3. Since the number of rotifers to be sterilized has increased, the use of two 15W UV lamps (Toshiba CL-15) is the same, but the distance to the water surface of the aqueous solution is shortened to 12 cm and the water surface of the aqueous solution is reduced. The UV intensity at 101.6 mW / cm ² was increased. The ultraviolet intensity is a value measured with an ultraviolet intensity meter (UVR-254, manufactured by Tokyo Optical Machinery Co., Ltd.) at a position away from the ultraviolet lamp in accordance with the distance from the ultraviolet lamp to the water surface. Further, in Experiment 4, the aqueous solution being sterilized by (stirring means) was stirred to promote replacement of the rotifer just below the water surface.

In Experiment 4, the water depth increased by 15 mm to 45 mm compared to 3 mm in Experiments 1 to 3, so that the UV intensity was increased as described above, but it was necessary to achieve the bactericidal effect equivalent to Experiment 2. It is expected that the irradiation time will be longer to ensure the amount of ultraviolet rays. Therefore, the number of harmful bacteria at each stage of irradiation for 5 minutes, 10 minutes, 15 minutes, and 20 minutes from the start of ultraviolet irradiation was examined. Ultraviolet quantity of rotifers per individual is a 5-minute irradiation with 0.00188mJ / cm ^2, 10 min irradiation ^{0.00375mJ / cm 2, 0.00563mJ / cm} 2 in 15 minutes irradiation, and in 20 minutes irradiation at 0.00750mJ / cm ² These values are much lower than the upper limit (5 mJ / cm ² ) of the amount of ultraviolet light obtained in Experiment 1, and no rotifer death was actually confirmed.

  The result of Experiment 4 is shown in FIG. The graph of the experimental results represents the CFU / g value as a logarithmic value for each of general bacteria (open circles) and TCBS bacteria (black circles). First, TCBS bacteria achieved a bactericidal effect equivalent to 1-minute irradiation in Experiment 2, that is, about 1/100 sterilization at the stage of 5-minute irradiation. Then, the sterilization effect gradually increases as the irradiation time increases, and at the stage of 20-minute irradiation, the sterilization effect equivalent to the 2-minute irradiation of Experiment 2, that is, about 1/1000 sterilization is achieved. Here, in this experiment 4, the amount of ultraviolet rays per individual rotifer is very small compared to experiment 2, but the irradiation time of ultraviolet rays is long and the feed organisms directly below the water surface are actively replaced by stirring. It is considered that the amount of ultraviolet rays per individual rotifer is secured to be equivalent to Experiment 2.

  For general bacteria, the 15-minute irradiation stage was reached, and finally the bactericidal effect equivalent to 1-minute irradiation in Experiment 2, that is, about 1/10 sterilization was achieved. Comparing Experiment 2 and Experiment 4 with this result, it is considered that there may be a difference in sterilization effect between TCBS bacteria and general bacteria depending on the conditions of sterilization treatment. Moreover, in Experiment 2, the sterilization rate of TCBS bacteria is larger than that of general bacteria, and the same tendency can be seen in Experiment 4. From this, it is considered that TCBS bacteria are more susceptible to ultraviolet rays than general bacteria and TCBS bacteria, and the bactericidal treatment of the present invention is particularly effective for TCBS bacteria. That is, it was found that when TCBS bacteria are targeted for sterilization, the present invention can provide a practically effective sterilization method.

Experiment 5: Demonstration of the present invention Finally, the sterilization apparatus described with reference to the above illustration was created, and a larger amount of feed organisms were sterilized to try to demonstrate the present invention. The experimental conditions are as follows. The storage container uses a stainless steel container with an inner diameter of 60 cm, filled with seawater (water temperature 21.1 to 24.7 ° C), which is an aqueous solution, at a depth of 10 cm, and low density (100,000 / mL = 3 billion / 30L) or high density (150,000 individuals / mL = 3 billion individuals / 20L) and experiments with Artemia in this aqueous solution suspended at a density of 3,300 individuals / mL = 100 million individuals / 30L did. Artemia is about several times as long as the rotifer, and the density was set to be lower than the individual length ratio. From this, for example, the number of rotifers to be sterilized at a time in Experiment 5 is about 2.8 to 1,100 times or more from about 2.8 billion to about 4.2 billion, compared to about 380,000 in Experiment 2 or Experiment 3.

As the ultraviolet rays, four 20W type ultraviolet lamps (GL-20 manufactured by National) were used, the distance to the water surface of the aqueous solution was 11 cm, and the ultraviolet intensity at the water surface of the aqueous solution was 121.6 mW / cm ² . The ultraviolet intensity is a value measured with an ultraviolet intensity meter (UVR-254, manufactured by Tokyo Optical Machinery Co., Ltd.) at a position away from the ultraviolet lamp in accordance with the distance from the ultraviolet lamp to the water surface. The irradiation time of ultraviolet rays is 30 minutes because the irradiation time of ultraviolet rays is more sterilized than in Experiment 4 because rotifer or artemia is sterilized. Further, in Experiment 5, the aqueous solution being sterilized was stirred by a stirring unit composed of a pair of blades having an outer diameter of 40 cm to promote replacement of the rotifer just below the water surface.

  FIG. 10 shows the experimental results for the low density rotifer, FIG. 11 shows the experimental results for the high density rotifer, and FIG. 12 shows the experimental results for Artemia. The graph of each experimental result shows that for low density rotifers and artemia, only general bacteria (open circles) and TCBS bacteria (black circles), and for high density rotifers only for TCBS bacteria (black circles), respectively. The value of CFU / g is expressed as a logarithmic value. First, regarding rotifers, it can be seen that, regardless of the density difference, general bacteria and TCBS bacteria are reduced by about 1/10 to 1/100, respectively, and a practical bactericidal effect is obtained. In addition, even with Artemia sterilization using the same sterilization device, harmful bacteria are reduced to 1/10 or more, so it can be said that practical sterilization is also possible. Thus, it was demonstrated that the method for sterilizing a feed organism according to the present invention is a sufficiently practical sterilization method instead of a chemical solution.

Here, the amount of ultraviolet rays in Experiment 5 is 7.53 × 10 ⁻¹⁰ mJ / cm ² per low-density rotifer, 5.02 × 10 ⁻¹⁰ mJ / cm ² per high-density rotifer, and per Artemia. 2.26 × 10 ^-8 mJ / cm ² , both of which are within the upper limits confirmed in Experiment 1 (the amount of ultraviolet light per rotifer is 5 mJ / cm ² and the amount of ultraviolet light per individual Artemia is 625 mJ / cm ² ) It is settled. Even by visual observation, it cannot be confirmed that the rotifer or Artemia has died. Rather, since each ultraviolet ray amount has a margin with respect to the upper limit value, for example, it is conceivable that the sterilizing effect equivalent to that of Experiment 5 is obtained while increasing the ultraviolet ray intensity and shortening the irradiation time.

It is a front view showing an example of the sterilizer based on this invention. It is a side view of the sterilizer of FIG. It is a top view of the sterilizer of FIG. It is the principal part excerpt perspective view showing the state which stirs the aqueous solution by a stirring part. FIG. 5 is a perspective view corresponding to FIG. 4 illustrating a state in which an aqueous solution is stirred by another stirring unit. FIG. 5 is a perspective view corresponding to FIG. 4 illustrating a state in which an aqueous solution is stirred by another stirring unit. 10 is a graph showing an experimental result in Experiment 2. 10 is a graph showing an experimental result in Experiment 3. 10 is a graph showing an experimental result in Experiment 4. It is a graph showing the experimental result about the low density rotifer in Experiment 5. FIG. It is a graph showing the experimental result about the high-density rotifer in Experiment 5. 10 is a graph showing experimental results for Artemia in Experiment 5.

Explanation of symbols

1 Sterilizer
11 Main unit
111 door
113 rails
114 acrylic small window
117 Protrusion prevention protrusion
118 Positioning protrusion
12 Reservoir
121 aqueous solution
122 Water surface
125 resin wheels
126 Discharge section
13 Stirrer
131 Drive unit
132 Rotation axis
133 feathers
134 Guide shaft
14 UV irradiation unit
141 UV lamp
142 reflector
16 Control unit
17 Reference plate
18 Fixing lever
23 Another stirrer
33 Another stirrer

Claims (18)

A method for sterilizing a feed organism, which sterilizes harmful bacteria possessed by the feed organism by irradiating ultraviolet rays toward the water surface of an aqueous solution in which the feed organism is suspended. The method according to claim 1, wherein the ultraviolet rays are C region ultraviolet rays. UV, bait biological methods germicidal UV intensity at the water surface of the aqueous solution according to claim 1, which is a ^{50mW / cm 2 ~150mW / cm 2} . ^{2. The} method for sterilizing a feed organism according to claim 1, wherein when the feed organism is a rotifer, the amount of ultraviolet rays on the water surface of the aqueous solution is 5 mJ / cm ² at maximum per individual feed organism. The method for sterilizing a feed organism according to claim 1, wherein when the feed organism is Artemia, the amount of ultraviolet rays on the water surface of the aqueous solution is 625 mJ / cm ² at maximum per individual organism. 2. The method for sterilizing a feed organism according to claim 1, wherein the feed organism is a rotifer suspended in an aqueous solution at a density of 10,000 individuals / mL to 200,000 individuals / mL. The method for sterilizing a feed organism according to claim 1, wherein the feed organism is Artemia suspended in an aqueous solution at a density of 1,000 individuals / mL to 20,000 individuals / mL. The method according to claim 1, wherein the aqueous solution is seawater. The method for sterilizing a feed organism according to claim 1, wherein the aqueous solution is a saline solution having an osmotic pressure substantially equivalent to seawater. The method for sterilizing a feed organism according to claim 1, wherein the aqueous solution is stirred together with the feed organism. A sterilization apparatus for sterilizing harmful bacteria held by a feed organism, a storage container for storing an aqueous solution in which the feed organism floats, an ultraviolet irradiation unit for irradiating ultraviolet rays toward the water surface of the aqueous solution stored in the storage container, the storage container, A sterilizing apparatus for food organisms comprising an apparatus main body that holds an ultraviolet irradiation unit in a predetermined positional relationship and a control unit that operates and stops the ultraviolet irradiation unit. 12. The apparatus according to claim 11, wherein the apparatus main body is provided with a stirring unit that hangs down toward the storage container, and a control unit that operates or stops the stirring unit. 13. The sterilization apparatus for food organisms according to claim 12, wherein the agitation unit is composed of a long member that swirls horizontally, the long member is immersed in the aqueous solution stored in the storage container, and the aqueous solution is stirred in the swirl direction. 13. The apparatus for sterilizing a feed organism according to claim 12, wherein the agitation unit is provided in the apparatus main body so as to be movable up and down with respect to the storage container, and the storage container is detachable from the apparatus main body. 13. The device for sterilizing a feed organism according to claim 12, wherein the device main body is a sealed box having a door, and a storage container and an ultraviolet irradiation unit are built in the device main body. 16. The apparatus for sterilizing a feed organism according to claim 15, wherein the apparatus main body includes a stirring unit that hangs down toward the storage container, and a control unit that operates or stops the stirring unit. 16. The apparatus for sterilizing a feed organism according to claim 15, wherein the agitation part is composed of a long member that horizontally turns, and the storage container is a bottomed cylinder having an inner diameter larger than the maximum turning radius of the long member of the agitation part. 16. The apparatus for sterilizing a feed organism according to claim 15, wherein the agitation unit is provided in the apparatus main body so as to be movable up and down with respect to the storage container, and the storage container is detachable from the apparatus main body.

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