JP6624903B2 - Disinfectant and disinfection method - Google Patents

Description

  The present invention relates to a disinfectant and a disinfecting method.

  Disinfection methods for inactivating pathogenic microorganisms and the like are roughly classified into a physical disinfection method using ultraviolet irradiation, an autoclave or the like, and a chemical disinfection method using a disinfectant. Of these, the disinfection method by ultraviolet irradiation has limited utility because no effect can be expected on the non-irradiated portion of ultraviolet light. Further, the disinfection method using an autoclave is hardly a simple method, and the object to be disinfected (such as a medical instrument) must have heat resistance. Against this background, a chemical disinfection method using a disinfectant has been widely adopted.

In recent years, as one of the chemical disinfection methods, a disinfection method using hydroxy radicals generated by photocatalysis has been proposed.
For example, Patent Document 1 discloses a method of inactivating pathogenic microorganisms by immersing a medical device in a composite solution containing photocatalytic titanium oxide, nitric acid, and alcohol and irradiating the medical device with light.
Patent Literature 2 discloses a method of inactivating pathogenic microorganisms by bringing a composite suspension containing photocatalytic titanium oxide into contact with pathogenic microorganisms and irradiating light.

JP 2003-339826 A JP 2004-244344 A

  By the way, it is known that spores formed by spore-forming bacteria are difficult to inactivate unless a so-called high-level disinfectant is used. When the spore-forming bacterium is in an environment in which it is difficult to vegetatively divide and multiply, the spore-forming bacterium forms a spore inside the bacterial cell and distributes the replicated gene inside the spore. These spores are extremely durable and can survive even if the cells die. When the environment improves, the spores germinate and regrow into bacteria again.

Conventionally, as a high-level disinfectant used for inactivating spores, those containing glutaraldehyde or peracetic acid are known. However, all are highly irritating, and there is a problem in terms of safety. Further, the disinfectant containing peracetic acid also has a problem in the stability of peracetic acid.
Therefore, it is conceivable to use the disinfectant containing titanium oxide described in Patent Documents 1 and 2 to inactivate spores. However, the present inventors have confirmed that the disinfectant containing titanium oxide contains spores. Has not been found to be inactivated.

  The present invention has been made in view of such circumstances, and has as its object to provide a disinfectant and a disinfecting method that contain a photocatalyst and can inactivate spores and the like.

Specific means for solving the above problems include the following embodiments.
<1> At least one selected from the group consisting of a photocatalyst in which the potential at the bottom of the conduction band is more positive than the one-electron reduction potential of oxygen and more negative than the two-electron reduction potential of oxygen, and ethanol and methanol A disinfectant containing one kind of alcohol and water.
Disinfectants according to <2> the photocatalyst is a WO ₃ <1>.
<3> The disinfectant according to <1> or <2>, wherein the volume ratio of water to the alcohol (water / alcohol) is 5/95 to 35/65.
<4> The disinfectant according to any one of <1> to <3>, which is used for inactivating spores.

<5> At least one selected from the group consisting of a photocatalyst in which the potential at the bottom of the conduction band is more positive than the one-electron reduction potential of oxygen and more negative than the two-electron reduction potential of oxygen, and ethanol and methanol A disinfection method of irradiating light in the presence of one kind of alcohol and water, and disinfecting the product by the light irradiation.
Sterilizing method according to <6> the photocatalyst is a WO ₃ <5>.
<7> The disinfection method according to <5> or <6>, wherein the volume ratio of water to the alcohol (water / alcohol) is 5/95 to 35/65.
<8> The disinfection method according to any one of <5> to <7>, wherein the spores are inactivated.

  ADVANTAGE OF THE INVENTION According to this invention, the disinfectant which contains a photocatalyst and can inactivate a spore etc. can be provided.

The aqueous ethanol solution and WO ₃ particles B. subtilis suspension and various concentrations were mixed, illustrates the time course of survival rates of Bacillus subtilis spores in the case of irradiating with visible light. The aqueous ethanol solution and TiO ₂ particles B. subtilis suspension and various concentrations were mixed, illustrates the time course of survival rates of Bacillus subtilis spores in the case of irradiation with ultraviolet light.

Hereinafter, an example of an embodiment of a disinfectant and a disinfection method to which the present invention is applied will be described in detail. However, the present invention is not limited to the following embodiments.
In this specification, a numerical range indicated by using “to” indicates a range including numerical values described before and after “to” as a minimum value and a maximum value, respectively.

<Disinfectant>
The disinfectant of this embodiment has a photocatalyst in which the potential at the bottom of the conduction band is more positive than the one-electron reduction potential of oxygen and more negative than the two-electron reduction potential of oxygen (hereinafter, also referred to as “specific photocatalyst”). ), At least one alcohol selected from the group consisting of ethanol and methanol (hereinafter, also referred to as “specific alcohol”), and water.

  According to the disinfectant of the present embodiment, not only microorganisms such as bacteria, fungi and viruses, but also spores can be inactivated. Examples of spore-forming bacteria that form spores include Bacillus subtilis, Bacillus cereus, Bacillus anthracis and other bacteria of the genus Bacillus, Clostridium tetani, and Botulinum. (Clostridium botulinum) and other bacteria of the genus Clostridium species.

  The reason that the spores can be inactivated by the disinfectant of the present embodiment is presumed to be that peracetic acid or formic acid is generated by irradiating the disinfectant of the present embodiment with light. That is, when light is irradiated to a mixture of the specific photocatalyst, ethanol, and water, hydrogen peroxide generated by two-electron reduction of oxygen and acetic acid generated by oxidation of ethanol react to generate peracetic acid. Further, when light is irradiated to a mixture of the specific photocatalyst, methanol and water, hydrogen peroxide generated by two-electron reduction of oxygen and formic acid generated by oxidation of methanol react with each other to generate formic acid. It is known that both peracetic acid and formic acid can inactivate spores.

  In addition, the present inventors detect the MTSO (methyl-p-tolyl sulfoxide) generated by the reaction between MTS (methyl-p-tolyl sulfide) and a peracid by high performance liquid chromatography, and thus, after irradiation with light. The presence of peracid in the disinfectant has been confirmed.

  As the specific photocatalyst, the potential at the bottom of the conduction band is more positive than the one-electron reduction potential of oxygen (−0.046 V vs. SHE (Standard Hydrogen Electrode), pH = 0), and the two-electron reduction potential of oxygen. There is no particular limitation as long as the photocatalyst is more negative than (+0.695 V vs. SHE, pH = 0). When the specific photocatalyst is irradiated with light, oxygen is two-electron reduced by the photoexcited electrons, and hydrogen peroxide is generated.

Examples of particular _{photocatalyst,} WO 3, Cu supported _{WO 3, Bi 2 WO 6,} Fe supported BiVO _4, Cu supported BiVO _4, Fe supported TiO ₂ and the like. In one embodiment, WO ₃ is used as the specific photocatalyst.
Cu supported WO _3, for example, can be obtained by added and mixed WO ₃ particles in an aqueous solution of copper salts of divalent copper chloride and dried.
The Fe-supported BiVO ₄ can be obtained, for example, by adding BiVO ₄ particles to an aqueous solution of an iron trivalent salt such as iron chloride, mixing and drying.
Cu-supported BiVO ₄ can be obtained, for example, by adding BiVO ₄ particles to an aqueous solution of a copper divalent salt such as copper chloride, mixing and drying.
The Fe-supported TiO ₂ can be obtained, for example, by adding TiO ₂ particles to an aqueous solution of an iron trivalent salt such as iron chloride, mixing and drying.

Incidentally, TiO ₂ is a photocatalyst, potential -0.2V (vs. SHE, pH = 0) of the conduction band and is, for than one-electron reduction potential of oxygen is negative, the light to TiO ₂ Upon irradiation, oxygen is one-electron reduced by photoexcited electrons, and a superoxide anion radical is generated.

  The shape of the specific photocatalyst is not particularly limited. From the viewpoint of increasing the specific surface area and improving the disinfecting effect, the specific photocatalyst is preferably in the form of particles. In this case, the average particle diameter of the specific photocatalyst is preferably, for example, 1 nm to 1000 nm.

  The concentration of the specific photocatalyst is not particularly limited. The concentration of the specific photocatalyst may be, for example, 0.1 mg / mL to 10 mg / mL, or 0.1 mg / mL to 5 mg / mL.

  As the specific alcohol, any one of ethanol and methanol may be used, or both may be used in combination. As the specific alcohol, ethanol is preferred from the viewpoint of safety.

  The volume ratio between water and the specific alcohol (water / alcohol) is, for example, preferably 5/95 to 35/65, more preferably 10/90 to 30/70, and 15/85 to 25 / More preferably, it is 75. By setting the volume ratio of water to the specific alcohol (water / alcohol) to 5/95 to 35/65, spores and the like can be inactivated more efficiently.

  The pH of the disinfectant of the present embodiment is not particularly limited. The pH of the disinfectant of the present embodiment is, for example, in the range of 1 to 9.

<Disinfection method>
The disinfection method of the present embodiment is to irradiate light in the presence of a specific photocatalyst, a specific alcohol, and water, and disinfect an object to be disinfected by a product of the light irradiation. As described above, when a mixture of a specific photocatalyst, ethanol, and water is irradiated with light, peracetic acid may be generated. Further, when a mixture of a specific photocatalyst, methanol and water is irradiated with light, formic acid may be generated. In the disinfection method of the present embodiment, an object to be disinfected is disinfected using such a product.

  In the disinfecting method of the present embodiment, the above-described disinfectant of the present embodiment can be used. When disinfecting, the object to be disinfected may be immersed in the disinfectant of the present embodiment and irradiated with light, or the object to be disinfected may be sprayed with the disinfectant of the present embodiment and irradiated with light.

  When the specific photocatalyst is previously coated on the object to be disinfected, a mixed solution of specific alcohol and water can be used instead of the disinfectant of the present embodiment. In this case, the object to be disinfected may be immersed in a mixture of specific alcohol and water and irradiated with light, or a mixture of specific alcohol and water may be sprayed on the object to be disinfected and irradiated with light. Is also good.

The irradiation light may be any light having energy equal to or higher than the band gap of the specific photocatalyst. Wavelength of the irradiated light varies depending on the kind of the particular photocatalyst, for example, if the specific photocatalysts are WO ₃ is 440nm or less. Examples of the light source include a fluorescent lamp, a halogen lamp, a xenon lamp, and a light emitting diode.

  The light irradiation time can be appropriately set according to the type of the pathogenic microorganism or the like. For example, when spores are inactivated, the light irradiation time is preferably set to 6 hours to 24 hours.

  Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to the examples.

[Preparation Example 1]
(Preparation of Bacillus subtilis suspension)
First, Bacillus subtilis (IAM 12118 ^T ) stored refrigerated at 5 ° C was inoculated into a NA (Nutrient Agar) medium using a platinum loop, and incubated at 37 ° C for 10 days. After 10 days, the Bacillus subtilis recovered from the NA medium was suspended in 10 mL of ultrapure water to prepare a B. subtilis suspension. Next, 100 mg of lysozyme was added to the Bacillus subtilis suspension, and the mixture was incubated at 37 ° C. for 30 minutes using a water bath. At that time, stirring was performed every 10 minutes. Then, centrifugation was performed at 3500 rpm for 10 minutes, and the supernatant was removed. After removing the supernatant, 10 mL of ultrapure water was added to suspend the precipitate, followed by centrifugation again to remove the supernatant. This washing operation was performed three times in total. After washing, the suspension of Bacillus subtilis was made up to 10 mL using ultrapure water, and refrigerated at 5 ° C. until use.

(Confirmation of spore formation using the Wirtz method)
First, 3 μL of physiological saline was dropped on a slide glass, and 1 μL of Bacillus subtilis suspension was dropped on the physiological saline. The cells were fixed by heating from the back side of the slide glass using a gas burner. Next, 5 μL of saturated malachite green was dropped on the cells, and the cells were heated at 82 ° C. for 10 minutes using a hot water bath. Thereafter, ultrapure water was flowed from the back side of the slide glass and dried. Next, 5 μL of a 0.25% by mass safranin solution was dropped, and the mixture was allowed to stand at room temperature for 30 seconds. Thereafter, ultrapure water was flowed from the back side of the slide glass and dried. Then, using an optical microscope, Bacillus subtilis stained blue with malachite green was observed, and it was confirmed that the Bacillus subtilis formed spores.
Furthermore, Bacillus subtilis was added to a 70% by volume aqueous ethanol solution, and it was confirmed that the survival rate did not decrease.

[Example 1]
First, the concentration of the B. subtilis suspension prepared in Preparation Example 1 was adjusted to 2.0 × 10 ⁷ CFU / mL using ultrapure water. Then added to the ethanol solution of various concentrations of B. subtilis suspension and 45mL of 5mL was mixed in a beaker of 200 mL, WO ₃ particles (model number: 550086-5G, Aldrich Co.) in 0.5 mg / mL It was added at a concentration.

Next, the liquid containing Bacillus subtilis was irradiated with visible light at an intensity of about 110 mW / cm ² . For light irradiation, a wavelength of less than about 420 nm was cut using a 150 W xenon lamp and an ultraviolet cut filter (L42, manufactured by HOYA CORPORATION). Thereafter, samples of Bacillus subtilis spores at light irradiation times of 0, 3, 6, 9, 12, 15, 18, 21, and 24 hours were collected, inoculated on NA medium, and incubated at 37 ° C. for 48 hours. . Then, the survival rate (%) of the Bacillus subtilis spores was determined by a colony counting method.

FIG. 1 shows the change over time in the survival rate of Bacillus subtilis spores. The vertical axis of FIG. 1 shows the logarithmic survival rate (%), and the horizontal axis of FIG. 1 shows the irradiation time of visible light.
As it can be seen from Figure 1, in the case of using a WO ₃ particles as a photocatalyst, the survival rate of Bacillus subtilis spores is lowered by irradiation with visible light. In particular, the survival rate of Bacillus subtilis was less than 0.001% within 9 hours when the ethanol concentration was 80% by volume and within 12 hours when the ethanol concentration was 90% by volume. Activated.

[Comparative Example 1]
First, the concentration of the B. subtilis suspension prepared in Preparation Example 1 was adjusted to 2.0 × 10 ⁷ CFU / mL using ultrapure water. Next, 5 mL of Bacillus subtilis suspension and 45 mL of various concentrations of ethanol aqueous solution were added to a 200 mL beaker and mixed, and TiO ₂ particles (trade name: AEROXIDE TiO ₂ P 25, manufactured by Degussa) were 1.0 mg. / ML.

Next, the liquid containing Bacillus subtilis was irradiated with ultraviolet light at an intensity of about 2.0 mW / cm ² using black light. Thereafter, samples of Bacillus subtilis spores at light irradiation times of 0, 3, 6, 9, 12, 15, 18, 21, and 24 hours were collected, inoculated on NA medium, and incubated at 37 ° C. for 48 hours. . Then, the survival rate (%) of the Bacillus subtilis spores was determined by a colony counting method.

FIG. 2 shows the change over time in the survival rate of Bacillus subtilis spores. The vertical axis in FIG. 2 shows the logarithmic survival rate (%), and the horizontal axis in FIG. 2 shows the irradiation time of ultraviolet light.
As can be seen from FIG. 2, when the TiO ₂ particles were used as the photocatalyst, the survival rate of the Bacillus subtilis spores hardly changed even when irradiated with ultraviolet light for 24 hours.

Claims (6)

A photocatalyst in which the potential at the bottom of the conduction band is more positive than the one-electron reduction potential of oxygen, and at least one selected from the group consisting of ethanol and methanol, and a photocatalyst that is more negative than the two-electron reduction potential of oxygen. A disinfectant containing alcohol and water used for inactivating spores . Disinfectants as claimed in claim 1 wherein the photocatalyst is a WO _3.   The disinfectant according to claim 1 or 2, wherein the volume ratio of water to the alcohol (water / alcohol) is 5/95 to 35/65. A photocatalyst in which the potential at the bottom of the conduction band is more positive than the one-electron reduction potential of oxygen, and at least one selected from the group consisting of ethanol and methanol, and a photocatalyst that is more negative than the two-electron reduction potential of oxygen. A disinfection method that inactivates spores by irradiating light in the presence of alcohol and water, and disinfecting the product by the light irradiation. Disinfection process according to claim 4 wherein the photocatalyst is a WO _3. The disinfection method according to claim 4 or 5 , wherein the volume ratio of water to the alcohol (water / alcohol) is 5/95 to 35/65.