JP2007136442A - Method for removing/recovering metal using microorganism, removing/recovering device, removing/recovering agent, and biosensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for recovering metals, with which metals can be sufficiently removed from a solution comprising metals with low concentration such as household effluent. <P>SOLUTION: In the method for recovering metals, objective metals are removed and recovered using microorganisms or the organelles of microorganisms. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for removing and recovering metals, particularly silver and / or copper, using microorganisms, an apparatus for removing and recovering metals using the microorganisms, a metal removal and recovery agent, and a biosensor. About.

  Currently, household appliances, kitchen appliances, toiletries, stationery supplies, furniture and decorative goods, etc .; paper and pulp slime control agents, wood preservatives, and other industrial fields; lab coats, curtains, building materials, and medical equipment Antibacterial compounds that are widely used in the medical field such as the above are roughly classified into inorganic (silver, copper, zinc, titanium oxide) and organic (synthetic, natural).

As an organic antibacterial compound, an organic compound that draws on the flow of agricultural chemicals and pharmaceuticals has been used from the viewpoint of a broad antibacterial spectrum and excellent quick action and bactericidal properties. However, since such compounds are concerned about safety to humans and the environment, in recent years, compounds containing antibacterial metals such as silver, copper, and zinc, and inorganic compounds such as photocatalysts such as titanium oxide, etc. Many antibacterial compounds have been used.
Of these inorganic antibacterial compounds, focusing on the ability of metals contained in metal-containing compounds to suppress the growth of bacteria, silver and mercury ions are particularly active, followed by zinc ions, copper ions, and cadmium ions. . More specifically, since silver has 200 times the antibacterial activity of copper and 1,000 times that of zinc, silver-containing inorganic antibacterial compounds are often used.

As a result of the use of metals in many inorganic antibacterial compounds, the chances of metals, particularly silver, flowing out into the environment are increasing. Since silver has a high antibacterial effect even in a very small amount, it can be considered that silver once leaked into the environment has some influence on the ecosystem.
The regulation of silver ion concentration in drinking water is 50 ppb in the United States and 100 ppb in European countries, and the regulation is becoming stricter.
Under such circumstances, it is important from the viewpoint of environmental conservation and from the viewpoint of living a healthy life to collect silver that is discharged into the environment and flow out, and to reduce the amount of discharge and outflow as much as possible. It is a problem.

As a method for removing silver, a method is disclosed in which microorganisms are used for removing silver used in the processing of silver halide in the field of photographic light-sensitive materials (Patent Document 1). The microorganism (Acidovorax genus bacterium) used in the method disclosed in Patent Document 1 is effective in an environment where the silver compound concentration is as high as several ppm to several hundred ppm, and requires organic compound drainage as a nutrient source. Suitable for use in waste water from photographic photosensitive material production plants. However, for example, wastewater from homes has a very low silver concentration of <1 ppm, and there are almost no organic compounds that serve as nutrient sources for microorganisms.
In addition, the method disclosed in Patent Document 1 needs to react bacteria and silver-containing wastewater for 2 to 10 days. Further, screening such special bacteria in a general household, and using them after propagation, In view of the necessity of the specialized knowledge and the influence on the ecosystem, it is difficult to recover the metal, which is suitable for simple use at home and the like.

Other methods of removing silver include chemical methods and electrical methods, but they are not effective enough to remove silver from wastewater containing low concentrations of silver, such as domestic wastewater. there were.
JP 2004-180582 A

  In view of the above points, the present invention sufficiently removes metals even from metals-containing solutions containing metals, particularly solutions containing extremely low concentrations of metals such as domestic wastewater. It is an object of the present invention to provide a method and apparatus for removing and collecting metals that can be used.

  In order to overcome the above problems, the present inventors have focused on non-selective ion channels of prokaryotes such as non-pathogenic Escherichia coli, and used them to target metals in metal-containing solutions. The present invention has been completed by finding that it can be removed and recovered.

Accordingly, the present invention provides a metal characterized by contacting a microorganism or an organelle of a microorganism with a metal-containing solution to remove the metal from the metal-containing solution, and optionally collecting the metal. This is a method for removing and recovering species.
The present invention is also a biosensor that selectively detects metals using a microorganism or an organelle of a microorganism immobilized on a carrier.

Furthermore, the present invention provides a metal-containing solution containing a metal and an introduction part for introducing a microorganism or a microorganism organelle (organelle), a metal-containing solution introduced from the introduction part, and the microorganism or microorganism A metal removal / recovery device including a processing vessel in contact with an organelle.
Furthermore, the present invention is a removal / recovery agent for metals consisting of microorganisms or organelles of microorganisms.

  In the present specification, the “metal-containing solution containing a metal” means a solution containing a metal of less than several tens of ppm, but an extremely low concentration of metal ions of less than several ppm, for example, less than 1 ppm. The containing solution is preferred. The lower limit of the metal ion concentration varies depending on the type of microorganism used or the organelle of the microorganism, but is preferably several ppb or more, for example, 10 ppb or more. Examples of such metal-containing solutions include domestic wastewater and factory wastewater from factories other than those related to photography.

  According to the present invention, metals are removed from a metal-containing solution containing metals, particularly waste water containing extremely low concentrations of metals, using microorganisms or microbial organelles. Since it can be recovered, a trace amount of metals can be prevented from being released into the environment. In addition, the biosensor of the present invention enables highly sensitive detection of metals and can be used to provide a living space in a safer form for humans and nature.

  Examples of metals that can be removed / recovered by the removal / recovery method of the present invention include metals contained in antibacterial compounds such as silver, copper, zinc, cadmium, and mercury. In particular, silver and / or copper can be efficiently removed and recovered. These metals are preferably in the form of ions in terms of removal and recovery efficiency.

Microorganisms used in the removal / recovery method of the present invention are not particularly limited as long as they have the ability to absorb metals. Prokaryotes such as E. coli, photosynthetic bacteria, lactic acid bacteria, actinomycetes, staphylococci, filamentous fungi, yeast, Examples include eukaryotic organisms such as Candida. These microorganisms may be isolated and used by a known method, or may be used without isolating microorganisms contained in soil or fertilizer.
The microorganism preferably has an organelle having a membrane-bound protein that selectively allows metals to pass through. In the present specification, an organelle refers to a cytoplasmic component including ribosome, endoplasmic reticulum, mitochondria, Golgi apparatus, nucleus and the like.

The membrane-bound protein is one that selectively allows metals to pass through by a concentration gradient or potential gradient of metals inside and outside the membrane, and examples thereof include an ion channel. Ion channels are small tunnels that penetrate biological membranes that are normally closed but open when a certain stimulus occurs. In the ion channel, the type of metal that can be taken in is determined by its potential selectivity. Depending on the type of ion channel, there are metals that pass through the membrane and metals that do not pass through the membrane, and this is thought to produce selectivity. Moreover, the speed which passes a film | membrane changes with kinds of metal.
In the removal / recovery method of the present invention, for example, when silver as a metal is removed / recovered using Escherichia coli, silver is selectively absorbed by ribosomes present in E. coli at a concentration of several ppb or more. Furthermore, in this case, the reaction between E. coli and metals occurs in minutes to hours, so the time required to accumulate the metals in the cells can be shortened, and the metals can be removed and recovered quickly. Can do.

  The microorganism used in the removal / recovery method of the present invention may be one that dies by accumulating metals in intracellular organelles. Such death of microorganisms is considered to occur within minutes to hours after the microorganisms start to absorb metals. For example, when silver is removed and collected using E. coli, silver is first accumulated in ribosomes and the normal protein expression function of E. coli is impaired. Next, the production mechanism of various proteins necessary for maintaining life activity has also become abnormal, and eventually the production of ATP (adenosine triphosphate), which is indispensable for life activity, is also impaired. Will be killed. Therefore, by tracking the survival rate of the microorganism, it can be used as an index for detecting the amount, concentration, etc. of the metals absorbed by the microorganism in contact with the microorganism. When Candida, for example, is used as the microorganism, metals may accumulate in the organelles in the cell in a shorter time than E. coli and may die. In this case, since metals such as silver are accumulated in the mitochondria of Candida and die by a mechanism similar to that of Escherichia coli, the amount and concentration of metals absorbed by the microorganism are detected in the same manner as when using Escherichia coli. It can also be used as an indicator.

In the removal / recovery method of the present invention, it is also a preferred embodiment that an organelle having the above-mentioned membrane-bound protein is isolated from a microorganism and used.
As a method for isolating organelles from microorganisms, conventionally known methods can be used, and examples include ultracentrifugation.

  The microorganism or organelle of the microorganism may be used by suspending itself in an appropriate liquid, or may be used by being immobilized on a carrier, but locally increases the concentration of the microorganism or organelle. In view of the fact that microorganisms and the like can be prevented from leaking outside the space where the present method is carried out, those immobilized on a carrier are preferred.

As the above-mentioned carrier, a carrier that is water-insoluble and inert to microorganisms is preferable, and diatomaceous earth, porous ceramics, zeolite, SiO ₂ , SiO ₂ -Al ₂ O ₃ , SiO ₂ -TiO ₂ , SiO ₂ -V Silicon compounds such as silicates containing ₂ O ₅ , SiO ₂ —BO ₂ , SiO ₂ —Fe ₂ O ₃ , semiconductors made of Si, etc .; Al ₂ O ₃
Transition metal oxides such as TiO ₂ , ZrO ₂ , Nb ₂ O ₅ , SnO ₂ , HfO ₂ , AlPO ₄ , metals such as Pt, Ag, Au; polymers such as polyacrylamide and activated carbon or gels thereof; A porous body made of a bio-derived material such as scallop shell or a composite thereof can be preferably used.
The microorganism or organelle can be immobilized on the carrier using a conventional method. For example, by bringing a porous carrier such as silica or alumina having a water absorbing function into contact with a solution containing microorganisms at a predetermined concentration for several minutes to several hours, the microorganisms are naturally retained in the pores. Is possible.

A conductive nanostructure can be further produced in the porous body. The conductive nanostructure can be manufactured using a conductive material having a hollow fiber-like or fibrous microstructure. Examples of the material include carbon-based materials such as carbon nanotubes, carbon nanowires, and carbon fibers; metal-based materials such as Au, Ag, and Ni; and materials having a microstructure composed of TiO ₂ , Si, and the like. By forming such a conductive nanostructure, conductivity can be imparted to the porous body, so that a sensing device using an electric field or a magnetic field is produced using a carrier on which microorganisms or organelles are immobilized. It can be used as a concentration sensor for metal ions such as trace amounts of silver ions.

In the removal / recovery method of the present invention, the microorganism or organelle is brought into contact with the metal-containing solution for a predetermined time. The metal-containing solution can efficiently remove and recover metals as long as it contains a metal to be removed and recovered at a concentration of less than several tens of ppm, but more preferably at a concentration of 10 to 1000 ppb. It is a solution containing. The treated water obtained after the metals are removed by the removal / recovery method of the present invention is obtained by removing the metals to a concentration below the detection limit by, for example, an atomic absorption meter (manufactured by Hitachi; Model 180-30). It can be.
The contact time can be appropriately selected depending on the type of metal to be removed / recovered and the type and concentration of the microorganism or organelle used. For example, when removing and recovering silver using Escherichia coli, it is sufficient to perform contact for about 5 minutes to 24 hours, more preferably for about 5 minutes to 3 hours.

  After contacting the microorganism or organelle with the metal-containing solution for a certain period of time, the metals can be recovered as desired. As a method for recovering metals, a method of separating microorganisms or organelles from a solution containing microorganisms or organelles is preferable. Examples of the method for separating microorganisms or organelles from the solution include a method using centrifugation and a method using a magnet.

  The microorganism or organelle can be removed from the microorganism or organelle contacted with the metal-containing solution. Examples of the removing method include ultrasonic disruption, treatment with a solution such as hydrogen peroxide, treatment with a lytic enzyme such as lysozyme, and a method of disrupting microorganisms or organelles by heating. In this way, the microorganisms or organelles can be removed, and the metals can be removed from the microorganisms or organelles and recovered.

  In the removal / recovery method of the present invention, it is preferable to detect the amount of metals incorporated into microorganisms or organelles. Examples of the method for detecting the amount of metals include a method for detecting a change in the weight or conductivity of a microorganism or organelle, a change in a magnetic field around the microorganism or organelle, and the like. As a result, the amount of metal accumulated in the microorganism or organelle can be known, so that the exchange time of the microorganism or organelle can be known.

  When performing the detection described above, it is preferable to use a porous body having the above-described conductive nanostructure as a carrier with microorganisms or organelles immobilized thereon. Furthermore, the carrier is more preferably linked to a weight sensing device, a detection unit such as an electrode, and an external display unit that receives and displays a signal from the detection unit.

  A metal removal / recovery apparatus capable of performing the above metal removal / recovery method is also one aspect of the present invention.

  A biosensor for detecting metals comprising a microorganism or a cell organelle of a microorganism used in the removal / recovery method of the present invention can be obtained. Such a biosensor is also one aspect of the present invention.

  The biosensor of the present invention can detect metals by detecting a change in the weight or conductivity of a microorganism or organelle, a change in a magnetic field around the microorganism or organelle, and the like.

  The biosensor described above is formed by immobilizing microorganisms or organelles. As the carrier to be immobilized, it is preferable to use a porous body having the above conductive nanostructure. Thereby, electromagnetic changes such as a change in conductivity and a change in magnetic field can be detected, and a biosensor with higher sensitivity can be obtained. Furthermore, the carrier is more preferably linked to a weight sensing device, a detection unit such as an electrode, and an external display unit that receives and displays a signal from the detection unit.

  A metal removal / recovery agent comprising a microorganism or a microorganism of a microorganism used in the removal / recovery method of the present invention is also one aspect of the present invention. Such a metal removing / collecting agent is preferably one in which microorganisms or organelles are immobilized on the above-mentioned water-insoluble carrier that is inert to microorganisms.

A container (for example, a cartridge) containing the metal removal / recovery agent according to the present invention can be disposed at a drain outlet of a washing machine, a dishwasher or the like. The capacity of the container can be appropriately changed according to the amount of drainage or the content of metals to be removed. For example, a container having a diameter of φ = 50 mm and a length of 20 cm can be used. FIG. 8 shows an example of a configuration in which a container containing such a metal removal / recovery agent is arranged in a washing machine. As shown in this figure, a container 72 containing a metal removal / recovery agent can be disposed at the drain port 71 of the washing machine 70.
It is preferable that the container containing the metal removal / recovery agent is replaced after a certain period of use.

  Moreover, the container which accommodated the metal removal and collection | recovery agent by this invention can be arrange | positioned also to the drain outlet of a bathroom.

  The container containing the metal removal / recovery agent is preferably used particularly for recovering silver ions that can be contained in waste water from a washing machine, a dishwasher or the like.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an example of a metal removal / recovery device that can be used in the removal / recovery method of the present invention by suspending a microorganism in an appropriate liquid as it is, and an example of using a microorganism immobilized on a carrier. Is shown in FIG. In these drawings, 1 is a microorganism, 2 is a metal-containing solution containing metals such as silver, 3 is a processing vessel, and 4 is a carrier. Here, the metal-containing solution 2 will be described by taking as an example a solution containing silver ions having particularly high bactericidal properties.

The silver ion-containing solution can be experimentally prepared, for example, by the following method. Basically, silver has a low ionization tendency, the standard unipolar potential is +0.8 V, and it has the characteristics that it is difficult to be a cation (it is difficult to emit electrons, it is difficult to oxidize), and even if metallic silver is placed in water. Does not elute easily. Therefore, as a method for generating silver ions, a method of applying an electric field is taken. For example, a method of eluting silver ions in a solution by controlling the voltage (about 50 V) so that a current of 10 to 50 mA is applied between two pure silver plates is actually used. Among these conditions, under conditions where silver ions are eluted at about 1.2 mg / min, a silver ion-containing solution of 200 ppb (= 200 μg / L) is obtained by energizing 1 L of water for 10 seconds. .

The material of the processing container 3 is not particularly limited as long as it is inert to the metal-containing solution and can hold microorganisms or organelles. For example, Teflon (registered trademark), stainless steel, or the like may be used. it can.
The metal-containing solution 2 is introduced into the processing container 3 of FIG. 1 or FIG. 2 from the introduction part, the metal-containing solution 2 and the microorganism 1 are brought into contact with each other for a certain time to remove the metals, and then the solution is discharged. . The used microorganisms or immobilized microorganisms can be recovered, and the cells can be removed to recover the metals.

FIG. 3 shows an example of an apparatus for removing and recovering metals that can detect metals by detecting changes in the weight of immobilized microorganisms in the method for removing and recovering metals according to the present invention. In this apparatus, when the immobilized microorganism 1 is put into the processing container 3 and the metal-containing solution 2 is introduced from the upper part of the apparatus to remove and collect the metal, the change unit weight of the immobilized microorganism 1 is detected. By detecting at 5 and transmitting a signal to the detection unit 6 and displaying it on the external display unit 7, it can be used as a biosensor. As the detection unit 5, for example, a quartz crystal sensor head can be used.
More specifically, for example, when microorganisms are immobilized in a porous body and these microorganisms absorb a metal such as silver and the unit weight changes, the oscillation frequency changes, for example, 5 to 10 MHz. On the other hand, it is possible to detect a change in the weight of the microorganism in contact with the surface of the detection unit (sensitivity can be detected as a weight change on the order of ng). In addition to the form of detecting a change in weight, it is possible to detect a change in the conductivity of microorganisms immobilized on the conductive nanofibers and a change in magnetic field caused by taking in a metal.

  Since a specific microorganism takes only a specific metal into the body, a specific microorganism sensor corresponding to the metal ion can be created. When microorganisms that can take in both silver and copper are used, it is possible to produce a multichannel biosensor by constructing a sensing system according to the difference in the uptake speed. In this case, silver has a higher uptake rate into the microbial body, and copper is taken into the microbial body relatively slowly. Using this characteristic, when the reaction time is short, only the silver concentration is detected, both the silver and copper are detected in the middle, and when the reaction time is set to a long time such as 24 hours, the change in the silver concentration has already occurred. Since it is saturated, it is possible to create a sensor that can detect only copper.

  FIG. 4 shows an example of an apparatus for removing and collecting metals that is used by immobilizing only organelles existing in microorganisms in the removing and collecting method of the present invention. In the form of this figure, the immobilized organelle 9 obtained by supporting the organelle on a carrier is used as a metal ion removal / recovery agent, and the immobilized organelle after a certain time has passed. The amount of metals taken into the organelle can be detected by measuring conductivity using the minute electrode 8 on the material 10. The detection method may detect a change in mass or a change in magnetic field.

  For example, in Escherichia coli, the organ that takes in a specific metal ion is mainly a ribosome, so by removing unnecessary organs such as cell membranes for silver adsorption, it is more sensitive and downsized than using the cells as they are. Metal removal / recovery device and biosensor can be obtained.

  FIG. 5 shows an embodiment in which the metal can be recovered from the microorganism that has taken in the metal in the apparatus for removing and recovering metals shown in FIG. Using the magnetic field of the magnet 11, the immobilized microorganisms that have taken in the metal are recovered. The recovered immobilized microorganisms can be burned at 300 ° C. as they are, the cells can be destroyed with hydrogen peroxide, or the cells can be crushed by applying ultrasonic waves to recover the metals from the inside. .

FIG. 6 shows a schematic view of another preferred embodiment of the metal removal and recovery apparatus of the present invention.
In FIG. 6, 60 is an introduction container as an introduction part for storing and introducing microorganisms or organelles and a metal-containing solution into a processing container. In the introduction container, an electrode 65 made of, for example, silver may be set. The metal ion concentration in the metal-containing solution can be adjusted by applying a DC voltage to the electrode.

  In FIG. 6, 61 is a processing container. In the processing container, the metal-containing solution introduced from the introduction container is brought into contact with the microorganism or the organelle of the microorganism. The processing container contains a microorganism or organelle and a metal ion-containing liquid. The processing container may be provided with a control means capable of controlling the temperature and / or the contact time at the time of contact.

  The processing container may include a sensor 66 as a detection unit for detecting the amount of change caused by the microorganism or organelle taking in the metal, for example, the amount of change such as weight, conductivity, magnetic field, and absorbance. The sensor can be provided with an evaluation means for performing feedback to the introduction container or the first or second movement control means described below according to the amount of change detected by the sensor. The sensor mounting position is not limited to the position shown in FIG. 6, and may be any position as long as the above change amount can be detected inside or outside the processing container.

  Between the introduction container and the processing container, a first movement control means 63 such as an electromagnetic valve for controlling the movement of the contents between the two containers may be provided. It is possible to control the amount of contents in the introduction container. One first movement control means may be provided in the common part of the introduction container and the processing container, or one first movement control means may be provided on each of the introduction container side and the processing container side of the joint portion of the introduction container and the processing container. Good.

  62 is a collection container for collecting metals from a solution containing microorganisms or organelles of microorganisms in the processing container. The collection container preferably includes a centrifuge or a magnet. As a result, the microorganisms or cell organelles after being brought into contact with the metal-containing solution in the processing container can be recovered to extract the metals. The magnet and the centrifuge may be integrated with the collection container or may be provided separately from the collection container.

  Between the processing container 61 and the collection container 62, the 2nd movement control means 64 which controls the movement of the content may be provided. One second movement control means may be provided at the common part of the processing container and the recovery container, or one second control means may be provided at each of the processing container side and the recovery container side of the joint portion of the processing container and the recovery container. Good.

The material of these introduction container, processing container and recovery container is not particularly limited as long as it has low reactivity with the contents and does not infiltrate, and Teflon (registered trademark) is preferably used.
The introduction container, the processing container, and the recovery container may be integrally formed, but each container or a part of the containers may be separable and may be structured to be assembled by fitting, screwing, or the like. In the case of a removable structure such as the latter, it is possible to prepare a plurality of removal portions and proceed with the removal / recovery process in parallel.

  FIG. 7 schematically illustrates the metal removal / recovery apparatus of FIG. 6 as an input means, a reaction / evaluation means, and an output means for the introduction container, the processing container, and the recovery container, respectively. It is a figure explaining each function to be called.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these embodiments. In the following examples, as a waste water containing extremely low concentration of metals, a solution containing metals was prepared and used for convenience.

In this example, a metal removal / recovery apparatus as shown in FIG. 1 was used. E. coli (Escherichia coli / NBRC-3972) used as a microorganism, which phosphate buffer at a concentration of 10 ⁹ cells / ml; developed against (PBS concentration 50 mM). This was placed in a cylindrical Teflon (registered trademark) processing container having a diameter of 25 mm and a thickness of 30 mm.
A silver ion-containing solution having a concentration of 200 ppb was obtained by applying an electric field of 50 V to two pure silver plates to obtain a current of 20 mA. This silver ion-containing solution was put into the above-mentioned metal removal / recovery device and left in this state for 10 minutes. Then, the solution was discharged and Escherichia coli was recovered by centrifugation.

  The recovered Escherichia coli was pre-fixed with 0.1 M cacodylate buffer and 2% glutaraldehyde in an environment of 4 ° C, then washed 3 times with 0.1 M cacodylate buffer at 4 ° C, and 2% osmium tetroxide. Post-fixation treatment was performed by infiltrating the aqueous solution at 4 ° C. for 3 hours. After 10-15 minutes each in the ascending alcohol train, treated with propylene oxide 3 times for 10 minutes, and further replaced with propylene oxide + epoxy resin for 1 hour, epoxy resin (main agent Epon812, curing agent DDSA, NMA, accelerator) DMP-3060 ° C) was embedded for 2 days.

  The obtained sample was sliced using an ultramicrotome and reinforced with a carbon film to prevent charge-up, and an energy filter type transmission electron microscope (EF-TEM) observation sample was prepared. When E. coli observed using this sample was subjected to silver detection using an energy dispersive X-ray analyzer (EDS), silver was remarkably detected from around the center of the cells. However, since silver ions are not in a concentration at which they can be seen as shapes, large crystals of silver are not structurally precipitated.

In this example, a metal removal / recovery device as shown in FIG. 2 was used.
1. Preparation of porous body having nanostructure As a porous material, diatomaceous earth ceramics (manufactured by Showa Chemical Industry Co., Ltd.) in which 85% or more of the components are made of SiO ₂ was used. This diatomaceous earth ceramic had a particle size of about 10 μm and an average pore size of about 1 μm. First, in order to remove contaminants on the surface, an Xe ₂ dielectric barrier discharge excimer lamp device was used, and ultraviolet light having a central wavelength of 146 nm was emitted at an irradiance of 10 mW / cm ² and cleaned for 1 hour. Further, Ni paste (Ni particle diameter of about 10 nm) made by Nippon Paint was used as a catalyst, and ultrasonic cleaning treatment was performed in an acetone solvent. This sample was moved to a vacuum chamber (microwave plasma CVD; in an MPCVD apparatus), evacuated to 1 × 10 ⁻⁵ Pa using a vacuum pump, and further subjected to heat treatment at 600 ° C. for 30 minutes. A cross-sectional sample of this sample was prepared for the purpose of confirming the state of the coat from an experiment conducted under the same conditions separately, and confirmed with a transmission electron microscope (TEM). It was found that the coating was almost uniform at a thickness of 50 nm.

This was followed by a process for producing nanostructures on the catalyst coated porous material. While maintaining the substrate temperature at 600 ° C., adjusting the pressure of the chamber with a pressure control valve so that the vacuum degree of the chamber is about 15 Torr, H ₂ gas is introduced at 80 sccm through a mass flow controller, and then a 2.45 GHz microwave. (350 W) was introduced to make this H ₂ gas into plasma, and the surface was cleaned for about 5 minutes. Next, 80 sccm of H ₂ gas and 20 sccm of CH ₄ gas were introduced into the chamber, 2.45 GHz microwave (500 W) was introduced, and the raw material gas composed of H ₂ and CH ₄ was converted into plasma, and the catalyst The diatomaceous earth porous material coated with was exposed to plasma for 10 minutes. At this time, a bias voltage of −100 V was applied to the substrate on which the diatomaceous earth porous material was installed. By this treatment, carbon fibers including Ni catalyst at the tip grew on the entire pores and the surface of the porous body. The obtained carbon fiber had a diameter of 10 to 30 nm and a length of 1 to 50 μm, and the fibrous and hollow fiber-like fibers were mixed in a ratio of about 1: 1. This state was confirmed using a TEM or a scanning electron microscope (SEM). The porous body having a nanostructure obtained in this way has conductivity.

2. Metal Recovery The porous body having the above-mentioned conductive nanostructure was put into the processing vessel of the same metal removal / recovery apparatus used in Example 1, and the same Escherichia coli NBRC- used in Example 1 was used. 3972 was supported on a porous material to expand with PBS at a concentration of 10 ⁹ cells / ml. After 30 minutes, in order to measure the E. coli concentration in the solution, the solution was collected and cultured on an agar medium, but no colonies were obtained. That is, it can be seen that Escherichia coli is hardly present in the solution and is supported by the porous body having a nanostructure.
Next, a 200 ppb silver ion-containing solution is introduced into the processing vessel, and after 30 minutes of contact, the discharged processing solution is collected and silver is collected using an atomic absorption meter (manufactured by Hitachi; Model 180-30). When the ion concentration was measured, it was below the detection limit. In other words, it can be seen that almost all of the silver ions were absorbed by E. coli.

In this example, a metal removal / recovery device as shown in FIG. 3 was used.
Escherichia coli was developed at a concentration of 10 ⁹ cells / ml in a porous body having a nanostructure prepared in the same manner as in Example 2, and this was measured with a quartz resonator to make a relative mass standard. This immobilized Escherichia coli was brought into contact with a silver ion-containing solution adjusted to a concentration of 1 ppm for 30 minutes. Thereafter, when the weight was measured with a crystal resonator, a relative increase in mass of about 1 mg was recognized. This numerical value was output externally through a measuring instrument, and the amount could be grasped visually.

In addition, a porous material having the nanostructure obtained in the same manner as in Example 2 and carrying E. coli at a concentration of 10 ⁹ / ml was prepared, and metals containing 1 ppm of silver ions and 1 ppm of copper ions were prepared. The containing solution was contacted for 10 minutes. When the residual metal analysis of the obtained processing liquid was performed using an atomic absorption spectrometer, silver ions were below the detection limit, but copper ions were detected at a concentration of 800 ppb. In other words, it was found that copper ions took time to enter the cells.
By making such a concentration measurement result into a database and quantifying the rate of entry of each unique ion into the cell and its concentration, the weight of the metal actually absorbed by the fungus is measured, and the ion is simply measured. We were able to develop a multi-channel sensor for each species.

In this example, a metal removal / recovery device as shown in FIG. 4 was used.
In order to obtain a ribosome fraction from E. coli, an ultracentrifugation apparatus (manufactured by Hitachi; CF15RXE) was used. First, E. coli (about 100 mg) recovered in a 2 ml centrifuge tube by centrifugation (15,000 rpm / 18,800G / 3 min / 4 ° C, or 4,000 rpm / 2,900G / 20 min / 4 ° C using a swing rotor). The suspension was suspended in 1 ml of PBS (50 mM / pH 7.4) in ice. Thereafter, the bacteria were crushed in ice for 30 seconds using an ultrasonic crusher (UH-50 type, 50 W / 20 ± 3 kHz, manufactured by MST), and this was repeated four times. The obtained lysate was centrifuged (13,000 rpm / 9,000 G / 10 min / 4 ° C., CS150GXL) and fractionated into sediment (fungal debris) and supernatant (cytoplasm, ribosome, etc.). The supernatant was further ultracentrifuged (50,000 rpm / 10,500 G / 60 min / 4 ° C., CS150GXL) and fractionated into a sediment (ribosome) and a supernatant (cytoplasmic soluble component). PBS was added to the resulting precipitate and dissolved by vortexing to isolate only the ribosome.

In order to further increase the sensitivity and size of the sensor produced in Example 3, the obtained ribosome fraction of Escherichia coli was supported on a porous body having the same nanostructure as described above. A silver ion-containing solution was allowed to act on the obtained immobilized ribosome, and then the immobilized ribosome was moved onto the base (common) electrode using a magnet. A probe was brought into contact therewith as an upper electrode, and the change in conductivity was observed. The conductance (A / V; Ω ⁻¹ ) when the silver ion-containing solution was not acted was ¹ μΩ ⁻¹ , but when the silver ion-containing solution was acted, it was 45 μΩ ⁻¹ , and silver was contained in the ribosome. It can be seen that ions have been incorporated.

In this example, a metal removal / recovery device as shown in FIG. 5 was used.
As described in Example 2, since the porous body after the nanostructure is imparted is conductive, it can be handled using a magnetic field. Therefore, the immobilized microorganisms brought into contact with the silver-containing solution having a concentration of 10 ppm were collected using a magnetic field. Since the recovered immobilized microorganisms have high heat resistance of diatomaceous earth as a carrier, diatomaceous earth does not decompose even if it is burned at 500 ° C. as it is. When the microbial cells were removed by combustion, silver ions held by the microbial cells aggregated to form fine particles of several nm. This was confirmed by sampling with a focused ion beam device and analysis with EF-TEM.

Changes in the number of viable microorganisms due to the uptake of metals In this example, changes in the number of viable microorganisms after contact with a metal-containing solution containing a specific concentration of metal ions for a specific time were examined.

The same Escherichia coli used in Example 1 is placed in a processing vessel of the same metal removal / collection apparatus used in Example 1, and the final concentration after mixing with the metal-containing solution is 5 × 10 ⁷ CFU. / Ml. A silver ion-containing solution was prepared in the same manner as in Example 1, and placed in the above processing container so that the final concentration was 50 ppb or 900 ppb. Samples were collected after 30 minutes, 3 hours, and 15 hours at room temperature, and the number of viable bacteria was counted as colony forming units (CFU) by plate culture. The results are shown in Table 1.

  From the results in Table 1, it can be seen that the number of viable microorganisms decreases depending on the contact time with the metal-containing solution. It can also be seen that the rate of change in the number of viable bacteria depends on the concentration of metal ions.

An apparatus as shown in FIG. 6 is produced as the metal removal / recovery apparatus of the present invention.
FIG. 7 is a flowchart showing the functions of the metal removal / recovery device. A solution containing metals serves as an input means, and the microorganisms or organelles in the processing container absorb the metals, and changes in weight, chemical activity, thermal characteristics, optical characteristics, etc. according to the reaction action. The amount is taken out as information, and the microorganisms or organelles are removed as necessary, whereby the metals are collected and used as a reaction / evaluation means. And the apparatus structure which provides the solution from which the metals were collect | recovered as a result of a reaction and evaluation means from the metals contained in the input means as an output means as an output means was established.

  By the metal recovery method of the present invention, it is possible to prevent a trace amount of metal contained in household wastewater or the like from flowing out into the ecosystem, and it is ultrasensitive using the technology used in the recovery method. It is possible to develop a sensing technology suitable for an ecological system, and to propose a device / system that can provide a living space in a safer form for human beings and the natural world.

FIG. 1 shows an example of an apparatus for removing and collecting metals that can be used in the method for removing and collecting metals according to the present invention and that is used without immobilizing microorganisms. FIG. 2 shows an example of an apparatus for removing and recovering metals that is used by immobilizing microorganisms that can be used in the method for removing and recovering metals according to the present invention. FIG. 3 shows an example of a metal removal / recovery device that can be used in the metal removal / recovery method of the present invention to detect metals by detecting changes in the weight of immobilized microorganisms. FIG. 4 shows an example of a metal removal / recovery device that can be used in the method for removing / recovering metals according to the present invention and uses only an organelle that is present in a microorganism. FIG. 5 shows an embodiment for recovering microorganisms incorporating metal, which can be used in the metal removal and recovery apparatus of FIG. FIG. 6 is a diagram schematically showing the metal removal and recovery apparatus of the present invention. FIG. 7 is a flowchart showing each stage in the metal recovery apparatus of FIG. FIG. 8 shows an embodiment in which a container containing the metal removal / recovery agent of the present invention is used in a washing machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Microorganism 2 Metal ion containing solution 3 Processing container 4 Carrier 5 Crystal oscillator sensor head 6 Oscillator 7 External display part 8 Probe 9 Immobilization cell organelle 10 Electrode base material 11 Magnet 60 Introduction container 61 Processing container 62 Recovery container 63 1st 1 movement control means 64 2nd movement control means 65 Electrode 66 Sensor 70 Washing machine 71 Drain outlet 72 Container containing metal removal / recovery agent

Claims (15)

  A method for removing and recovering metals, comprising removing a metal from a metal-containing solution by contacting a microorganism or an organelle of the microorganism with a metal-containing solution, and collecting the metal if desired. .   The method for removing and collecting metals according to claim 1, wherein metal ions in the metal-containing solution are taken into microorganisms or organelles of microorganisms.   The method for removing and recovering metals according to claim 1 or 2, wherein the concentration of metal ions in the metal-containing solution is less than 1 ppm.   The method for removing and recovering metals according to any one of claims 1 to 3, wherein the microorganism is Escherichia coli.   The method for removing and recovering metals according to any one of claims 1 to 3, wherein the microorganism is Candida.   The method for removing and recovering metals according to any one of claims 1 to 5, wherein the microorganism or the organelle of the microorganism is immobilized on a carrier.   The method for removing and recovering metals according to claim 6, wherein the carrier is insoluble in water and inert to microorganisms.   Contact is at least 5 minutes or more, The method for removing and recovering metals according to any one of claims 1 to 7.   The method for removing and collecting metals according to any one of claims 1 to 8, wherein the metals to be collected are silver and / or copper.   The method for removing and collecting metals according to any one of claims 1 to 9, wherein the microorganism is killed by accumulating the metals in the organelle.   A biosensor for detecting metals comprising a microorganism or an organelle of a microorganism immobilized on a carrier.   A metal-containing solution containing a metal and an introduction part for introducing a microorganism or a microorganism (organelle), a metal-containing solution introduced from the introduction part, and a microorganism or a microorganism A metal removal / recovery device comprising a processing container to be contacted.   The metal removal / recovery device according to claim 12, wherein the metal removal / recovery is performed using the method according to any one of claims 1 to 10.   Metal removal / recovery agent consisting of microorganisms or organelles of microorganisms.   A metal removal / recovery agent according to claim 14, wherein the metal removal / recovery agent is housed in a container and installed in a washing machine, a dishwasher or a bathroom drain.

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