JP5123503B2 - Microbial activity control method - Google Patents

Description

  The present invention relates to a method for controlling the activity of microorganisms. More specifically, the present invention relates to a method for selectively activating a desired microorganism by controlling a redox potential of a culture solution.

  It is said that less than 1% of all microorganisms present in nature are currently used in various fields. Therefore, in order to effectively use the remaining 99% of the huge microbial resources, many culturing techniques for microorganisms based on a new concept have been developed.

  For example, Patent Document 1 discloses a technique for accumulating and cultivating chromium-reducing bacteria having the ability to reduce hexavalent chromium, which is an environmental pollutant, to harmless trivalent chromium. Specifically, in a culture solution in which hexavalent chromium is dissolved to make it difficult for various microorganisms other than chromium-reducing bacteria to grow, Shwanella, Pseudomonas, Sulfate reducing bacteria having a reducing activity against hexavalent chromium, Chromium-reducing bacteria such as Arthrobacter, Bacillus, Aerococcus, Micrococcus, Aeromonas, Thermoanaerobacter, Cellulomonas, Geobacter, Streptomyces, Escherichia, Enterobacter, etc. are selectively accumulated and cultured. The trivalent chromium produced by reduction by oxidation is oxidized and regenerated to hexavalent chromium, and then cultured.

Here, various substances other than hexavalent chromium are known as environmental pollutants. For example, organochlorine compounds such as tetrachloroethylene (PCE) and dichloroethylene (DCE) are known as environmental pollutants that are widely distributed in soil and groundwater. Since these organochlorine compounds have low solubility in water and are likely to accumulate in the underground environment, physical and chemical purification and purification using aerobic microorganisms are difficult. In recent years, a group of microorganisms growing by performing anaerobic respiration using an organic chlorine compound as an electron acceptor has been discovered, and application to bioremediation is expected.
JP 2006-55134 A

  However, it is difficult to culture a dechlorinated microorganism that performs anaerobic respiration using an organic chlorine compound such as PCE or DCE as an electron acceptor. In addition to dechlorinated microorganisms, there are many microorganisms that are difficult to culture in nature. Therefore, establishment of a culture technique for such difficult-to-culture microorganisms is desired.

  Further, in application to bioremediation, it is important to control the functions of microorganisms by controlling their activities, not just culturing microorganisms.

  Accordingly, an object of the present invention is to provide a method that enables selective control of growth and activity of a desired microorganism.

  In order to solve this problem, the inventors of the present application cultivate microorganisms because microorganisms existing in the underground environment grow in different redox potential environments depending on the type of electron acceptor used for respiration. Various studies were conducted considering that the oxidation-reduction potential of the culture medium during the treatment might have some influence on the growth of microorganisms. As a result, it has been found that by controlling the oxidation-reduction potential of the culture medium to a specific range when cultivating dechlorinated microorganisms that perform anaerobic respiration using PCE as an electron acceptor, it shows very excellent dechlorination activity. And it came to this invention.

  The microorganism activity control method according to claim 1 based on such knowledge is obtained by immersing an electrode in a culture solution containing the activity control target microorganism, and applying a potential to the electrode to set the oxidation-reduction potential of the culture solution. In order to selectively activate the activity control target microorganism.

  In this way, by controlling the oxidation-reduction potential of the culture solution itself within the optimum range of the activity-control target microorganism, the culture solution becomes an optimal environment for the activity-control target microorganism. Become. On the other hand, since it is not an optimum environment for microorganisms other than the activity control target microorganism, activation becomes difficult. Therefore, the activity control target microorganism can be selectively activated, and the function of the activity control target microorganism can be maximized.

  In this specification, “activation” means that the function of the activity control target microorganism group is increased by the proliferation of the activity control target microorganism, and the ratio of the functioning activity control target microorganism is increased. It means both the enhancement of the function of the microbial community.

  Next, the microorganism activity control method according to claim 2 is the microorganism activity control method according to claim 1, wherein the oxidation-reduction potential of the culture solution is controlled by the potential applied to the electrode. The resulting oxidation-reduction substance is contained in the culture solution, and the concentration ratio of the oxidation-reduction substance of the oxidation-reduction substance is controlled by the potential applied to the electrode.

  In this way, by controlling the concentration ratio of the oxidant and reductant of the redox substance by the potential applied to the electrode, the redox potential of the culture solution itself can be controlled to a constant value.

  The microorganism activity control method according to claim 3 is the microorganism activity control method according to claim 1, wherein the culture solution further contains a substance that functions as an electron acceptor of the activity control target microorganism. .

  By including a substance that functions as an electron acceptor of the activity control target microorganism in the culture solution, the activity control target microorganism respires. Therefore, the activation of the activity control target microorganism can be further promoted.

  In the microorganism activity control method according to claim 4, the activation target microorganism is activated in an anaerobic environment. Therefore, anaerobic microorganisms and facultative microorganisms (microorganisms that normally prefer an aerobic environment but can grow even in an anaerobic environment) can be efficiently activated using microorganisms as activity control targets.

Next, the microorganism activity control method according to claim 5 is the microorganism activity control method according to claim 1, wherein the optimum range of the redox potential is derived by the following procedures (a) to (e). Thus, the activity control target microorganism is selectively activated within the derived optimum range.
(A) preparing a plurality of culture solutions containing an activity control target microorganism and an electron acceptor substance that functions as an electron acceptor of the activity control target microorganism
(B) Immerse the electrode in each of the multiple culture solutions
(C) For each of the plurality of culture solutions, only the potential applied to the electrode is varied, and the culture test is performed under various oxidation-reduction potential conditions.
(D) The same culture test as in (c) is performed as a comparative test without applying an electric potential to the electrodes.
(E) A reduction potential of the electron acceptor substance in the culture test is compared with the decrease in the electron acceptor substance in the comparative test, and the redox potential condition in which the decrease of the electron acceptor substance in the culture test is larger than that in the comparative test. Is the optimal range

Here, in the microorganism activity control method according to claim 5, for example, the activity control target microorganism is a tetrachlorethylene (PCE) dechlorination microorganism, and the electron acceptor substance is tetrachloroethylene. Further, the activity control target microorganism is a dichloroethylene (DCE) dechlorination microorganism, and the electron acceptor substance is dichloroethylene. Further, the activity control target microorganism is a vinyl chloride (VC) dechlorination microorganism, and the electron acceptor substance is vinyl chloride. Further, the activity-controlled microorganism is a sulfate-reducing bacterium, and the electron acceptor substance is sulfate ion.

  Therefore, the culture solution should be made into an optimum environment for the growth of activity-controlled microorganisms such as tetrachlorethylene (PCE) dechlorinated microorganisms, dichloroethylene (DCE) dechlorinated microorganisms, vinyl chloride (VC) dechlorinated microorganisms, and sulfate-reducing bacteria. Therefore, each microorganism can be selectively activated to enhance dechlorination activity and sulfate reduction activity.

Here, the silver / silver chloride electrode shows a value of +0.22 V with respect to the standard hydrogen electrode. Then, by adding 0.22 V to the redox potential for the silver / silver chloride electrode, the redox potential for the silver / silver chloride electrode can be converted into the redox potential for the standard hydrogen electrode. Therefore, the redox potential for electrodes other than the silver / silver chloride electrode can be converted from the redox potential for the silver / silver chloride electrode. For example, the redox potential for a silver / silver chloride electrode is X (V), the redox potential for an electrode other than the silver / silver chloride electrode is A (V), and the potential of the electrode other than the silver / silver chloride electrode with respect to the standard hydrogen electrode Is B (V), the oxidation-reduction potential A for an electrode other than the silver / silver chloride electrode can be converted by the following formula.
[Formula 1] A = X + 0.22-B

That, A obtained by Equation 1, Ru synonymous der redox potential for silver-silver chloride electrode.

For example, when a saturated calomel electrode is used as an electrode other than a silver / silver chloride electrode, the potential B of the electrode with respect to a standard hydrogen electrode is + 0.24V, for example, more than −0.7V to less than −0.5V. The range of the oxidation-reduction potential can be converted from over -0.72 V to -0.52 V.

Further, when a mercury / mercury sulfate (I) electrode is used as an electrode other than the silver / silver chloride electrode, the potential B of the electrode with respect to the standard hydrogen electrode is +0.66 V , for example, more than −0.7 V to −− range of the redox potential of less than 0.5V, the Ru can be converted with -1.14V super ~-0.94 V.

  According to the first aspect of the present invention, the function of the control target microorganism group can be enhanced by the proliferation of the activity control target microorganism and the increase in the ratio of the functioning activity control target microorganism. In addition, since it is not an optimal environment for microorganisms other than the activity control target microorganism, activation becomes difficult. Therefore, the activity control target microorganism can be selectively activated, and the function of the activity control target microorganism can be maximized. In addition, since the active target microorganism can be selectively grown, the desired microorganism can be selectively cultured. Furthermore, since the activity of the microorganism can be controlled only by controlling the oxidation-reduction potential of the culture solution, it is very simple and low cost.

  According to invention of Claim 2, the oxidation-reduction potential of culture solution itself can be controlled to a fixed value.

  According to the third aspect of the invention, the activation of the activity control target microorganism can be further promoted by causing the activity control target microorganism to perform respiration. Moreover, when the electron acceptor substance is a harmful substance such as an environmental pollutant, an active control microorganism capable of treating the harmful substance can be selectively grown and cultured while treating the harmful substance. An advantageous effect can be obtained.

  According to the invention described in claim 4, the activation target microorganism is activated in an anaerobic environment. Therefore, anaerobic microorganisms and facultative microorganisms (microorganisms that normally prefer an aerobic environment but can grow even in an anaerobic environment) can be efficiently activated using microorganisms as activity control targets.

According to the invention described in claim 5, since it is possible to derive the optimum range of the oxidation-reduction potential of the activity control target microorganism, it is possible to activate the activity control target microorganism within the derived optimum range. it can. Therefore, according to the invention described in claim 6, tetrachlorethylene (PCE) dechlorination microorganisms can be selectively activated. Therefore, it is possible to maximize the function of dechlorinating PCE into DCE, and it is possible to selectively culture tetrachlorethylene (PCE) dechlorinated microorganisms.

According to invention of Claim 7 , a dichloroethylene (DCE) dechlorination microorganism can be activated selectively. Therefore, the function of dechlorinating DCE to ethylene (ETH) can be exhibited to the maximum, and selective culture of dichloroethylene (DCE) dechlorinated microorganisms is also possible.

According to the invention described in claim 8 , vinyl chloride (VC) dechlorinated microorganisms can be selectively activated. Therefore, the function of dechlorinating VC to ETH can be exhibited to the maximum, and selective culture of vinyl chloride (VC) dechlorinated microorganisms is also possible.

According to the invention described in claim 9 , sulfate-reducing bacteria can be selectively activated. Therefore, the function of reducing sulfate ions to hydrogen sulfide can be exhibited to the maximum, and selective culture of sulfate-reducing bacteria is also possible. Furthermore, in sulfate-reducing bacteria known to have an effect of decomposing aromatic compounds such as benzene and toluene in a complementary manner to sulfate reduction, the function of decomposing benzene and toluene can be maximized.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 illustrates a case where an electroculture apparatus 1 is used as an example of an embodiment of the microorganism activity control method of the present invention. In the microorganism activity control method of the present invention, an electrode is immersed in the culture solution 4 containing the activity control target microorganism 2, and an electric potential is applied to the electrode so that the redox potential of the culture solution 4 is optimal for the activity control target microorganism 2. It controls to the range and selectively activates the activity-control target microorganism 2. That is, it is a novel method that can selectively activate the activity control target microorganism 2 as an optimum environment for the activity control target microorganism 2 by controlling the oxidation-reduction potential of the culture solution 4 itself.

  The electrolytic cell 5 is divided into a culture cell 7 and a counter electrode cell 8 by an ion exchange membrane 6. The culture tank 7 and the counter electrode tank 8 are filled with the culture solution 4, the working electrode 9 and the reference electrode 11 are immersed in the culture tank 7, and the counter electrode 10 is immersed in the counter electrode tank 8. The working electrode 9, the counter electrode 10 and the reference electrode 11 are connected to a three-electrode type potential control device (potentiostat) 12 so that the potential of the working electrode 9 in the culture tank 7 can be set strictly.

  A redox substance 3 is further added to the culture tank 7.

The redox substance 3 is a substance that can cause a redox reaction reversibly with the working electrode 9 immersed in the culture solution 4 and that does not show toxicity to the activity-control target microorganism 2. Good. For example, a general iron ion is mentioned as a soil component. The iron ion reversibly changes into an oxidized form and a reduced form according to the chemical reaction formula 1 shown below.
[Chemical Reaction Formula 1] Fe (III) + e ⁻ = Fe (II)

  Here, in order to allow iron ions to stably exist in the culture solution 4, it is preferable that iron ions be coordinated with the chelating agent and added to the culture solution. As the chelating agent, any chelating agent capable of coordinating iron ions can be used. For example, diethylenetriaminepentaacetic acid (DTPA), ethylenediaminetetraacetic acid (EDTA), tetraethylenetriamine (TET), ethylenediamine (EDA), diethylenetriamine (DETA), citric acid, oxalic acid, crown ether, nitrilotetraacetic acid, disodium edetate, sodium edetate, trisodium edetate, penicillamine, trisodium pentetate calcium, pentetate, succil and edet An acid trientine can be mentioned, and EDTA is preferred.

  In addition to iron ions, quinone compounds such as potassium ferrocyanide and sodium anthraquinone disulfonate, and methyl viologen can be used. These substances also reversibly change into an oxidized form and a reduced form by an oxidation-reduction reaction. In particular, a quinone compound is a substance known as one of the soil components and is preferable. That is, by adding the soil itself to the culture solution 4, the oxidation-reduction potential of the culture solution can be controlled by the oxidation-reduction substance 3 contained in the soil. The redox material 3 is not limited to the materials described above.

  The amount of the redox substance 3 added to the culture tank 7 is not particularly limited as long as the redox potential of the culture solution 4 can be controlled, but the concentration of the culture solution 4 is 0.1 to 100 mmol / L. Is preferred. If it is less than 0.1 mmol / L, the redox potential may not be sufficiently controlled, and if it exceeds 100 mmol / L, it may not be completely dissolved in the culture solution or may cause growth inhibition of microorganisms. is there.

  Further, the electron acceptor substance 13 may be added to the culture tank 7. In this case, the activity control can be performed more efficiently by causing the activity control target microorganism 2 to breathe.

  The electron acceptor substance 13 is not particularly limited as long as it can cause the activity-control target microorganism 2 to perform respiration. For example, tetrachloroethylene (PCE) against PCE dechlorinated microorganisms, and against DCE dechlorinated microorganisms. Dichloroethylene (DCE), vinyl chloride against VC dechlorinated microorganisms, nitrate ions against nitrate-reducing bacteria, sulfate ions against sulfate-reducing bacteria, carbon dioxide against methanogens, against chlorobenzene-dechlorinated microorganisms Chlorobenzene, chlorophenol against chlorophenol dechlorinated microorganisms, chromium ion against chromium-reducing bacteria, quinone against quinone-reducing bacteria, mercury ion against mercury-reducing bacteria, cadmium ion against cadmium-reducing bacteria, iron reduction An iron ion is mentioned with respect to a microbe.

  It is possible to control the activity of microorganisms without adding the electron acceptor substance 13 to the culture tank 7. For example, the activity control target microorganism 2 that has been grown in advance is put into the culture tank 7, and the activity control target microorganism 2 is increased by controlling the oxidation-reduction potential of the culture solution 4, thereby increasing the activity control target microorganism 2. The target microorganism 2 can be activated.

  Here, in the microorganisms activity control method of the present invention, the growth environment of the target microorganism 2 is an anaerobic environment. In this case, an anaerobic microorganism or a facultative microorganism (a microorganism that normally prefers an aerobic environment but can grow in an anaerobic environment) can be efficiently activated using the microorganism as an activity control target microorganism. In an anaerobic environment, for example, the electrolytic cell 5 of the electroculture device 1 is placed in a box (not shown), and the box is filled with hydrogen gas, carbon dioxide, inert gas (nitrogen, rare gas), or a mixed gas thereof. However, it is not limited to such a method.

  In this embodiment, the growth environment of the active target microorganism 2 is an anaerobic environment. However, the growth environment of the active target microorganism 2 is an aerobic atmosphere, and the aerobic microorganism or facultative microorganism is an activity control target microorganism. By controlling to the optimum redox potential, the activation can be performed efficiently.

  Next, the oxidation-reduction potential of the culture solution 4 will be described. The oxidation-reduction potential of the culture solution 4 is expressed by the Nernst equation shown in Equation 1.

[Formula 2] E = E ₀ + RT / nF × ln (C _ox / C _red )

In Equation 2, E is the redox potential of the solution, E ₀ is the standard redox potential of the redox material, R is the gas constant, T is the absolute temperature, n is the number of reaction electrons, F is the Faraday constant, and C _ox is the oxidant. , C _red is the concentration of the reductant. That is, the oxidation-reduction potential of the culture solution 4 itself can be controlled by controlling the ratio of the oxidant concentration of the redox substance 3 and the concentration of the reductant contained in the culture solution to be constant. That is, the redox material 3 is an element that determines the redox potential of the culture solution 4, and the composition of the culture solution 4 hardly affects the redox potential.

  The tripolar potential control device 12 measures the potential difference between the working electrode 9 and the reference electrode 11, passes a current between the working electrode 9 and the counter electrode 10 so that the measured potential difference reaches the set potential V, and sets the reference Thus, no current flows through the reference electrode 11. In this way, the potential of the working electrode 9 is controlled to a constant potential V, and the ratio of the oxidant concentration to the reductant concentration of the redox substance 3 is controlled to be constant, whereby the redox potential of the culture solution 4 itself. Is controlled to be constant. Here, the redox potential of the culture solution 4 corresponds to the redox potential of the working electrode 9. Therefore, the set potential V, that is, the potential of the working electrode 9 with respect to the reference electrode 11 corresponds to the redox potential of the culture solution 4.

  As an example, a case where the oxidation-reduction potential of a culture solution having a oxidation-reduction potential of +0.5 V is controlled to -0.5 V will be described with reference to FIG. In the initial state, that is, when no potential is applied to the working electrode 9, the measured redox potential of the working electrode 9 is +0.5 V, which is the potential difference between the working electrode 9 and the reference electrode 11 (FIG. 15). (1)). Next, when potential control is started with the set potential set at −0.5 V, the potential of the working electrode 9 instantaneously becomes the set potential, and the redox substance 3 in the culture solution 4 undergoes a redox reaction, and the redox substance 3 The concentration ratio of the oxidant and reductant is controlled, the potential of the culture solution 4 gradually approaches the set potential ((2) in FIG. 15), and becomes a steady state. .5V ((3) in FIG. 15). At this time, the measured redox potential of the working electrode 9 is −0.5 V, which is the potential difference between the working electrode 9 and the reference electrode 11.

  Here, since the oxidation-reduction potential corresponds to the potential of the working electrode 9 with respect to the reference electrode 11, the value of the oxidation-reduction potential varies depending on the type of the reference electrode 11. The oxidation-reduction potential in this specification is a value for a silver / silver chloride electrode showing +0.22 V with respect to a standard hydrogen electrode, but the reference electrode 11 is not limited to a silver / silver chloride electrode. The oxidation-reduction potential when an electrode other than a silver / silver chloride electrode is used can be easily converted by the method described above, and the range of the oxidation-reduction potential converted when an electrode other than a silver / silver chloride electrode is used is also included in the present invention. included. In addition, the value of the oxidation-reduction potential described below is a value with respect to the silver / silver chloride electrode.

In addition, even when C _ox / C _red (concentration ratio of oxidant and reductant) is changed by oxidizing or reducing the redox substance by the microorganisms introduced into the culture tank 7, the reversible redox substance is removed. By using it, the redox potential can be maintained at a constant value by controlling to a predetermined C _ox / C _red .

Here, the ion exchange membrane 6 that divides the electrolytic cell 5 into two cells is a membrane that transmits only monovalent cations. Therefore, since bivalent iron ions and trivalent iron ions do not permeate, the redox material 3 does not move to the counter electrode tank 8. Therefore, the redox material 3 can be repeatedly used in the culture tank 7. In the counter electrode 9 installed in the counter electrode tank 8, hydrogen reduction / oxidation reaction occurs as a reverse reaction of the working electrode 9. In addition, transmission of ionic current between the membranes is performed by monovalent cations such as hydrogen ions, sodium ions (Na ⁺ ), and potassium ions (K ⁺ ) contained in the culture solution. Such an electrochemical reaction proceeds in the electrolytic cell 5, and the oxidation-reduction potential of the culture solution is controlled to be constant.

  The optimal range of the oxidation-reduction potential of the activity-control target microorganism 2 can be derived by a microorganism activity evaluation test described below. That is, all the culture conditions other than the oxidation-reduction potential are prepared, and the culture is performed with the oxidation-reduction potential set in a certain range, for example, in the range of −1 V to 1 V. Further, as a comparison condition, the culture is performed even under a condition where no voltage is applied. Before starting the culture, the electron acceptor substance 13 of the activity-control target microorganism 2 is added to the culture solution. Then, after culturing for several days, the concentration of the electron acceptor substance 13 in the culture solution is measured and the amount of decrease is measured, and the amount of decrease in the electron acceptor substance 13 is greater than the comparison condition. However, the activity is high, and the oxidation-reduction potential condition is in the optimum range.

  The present inventors obtained the optimum range of the oxidation-reduction potential of the PCE dechlorinated microorganism, the DCE dechlorinated microorganism, the VC dechlorinated microorganism, and the sulfate reducing bacterium by this activity evaluation test.

  The PCE dechlorination microorganism is a microorganism that dechlorinates PCE (tetrachloroethylene) to DCE (dichloroethylene) in the dechlorination reaction shown in FIG. 12 by anaerobic respiration. The optimum range of the oxidation-reduction potential of this microorganism is more than -0.7 V to less than -0.5 V, more preferably -0.65 V to -0.55 V, and still more preferably -0.6 V. An oxidation-reduction potential of −0.5 V or more and −0.7 V or less is not preferable because the PCE dechlorination activity is lower than that in the case of culturing without applying voltage.

  A novel or known microorganism can be used as the PCE dechlorination microorganism. For example, Desulfitobacterium, Dehalococcoides, Dehalobacter, Geobacter.

  The DCE dechlorination microorganism is a microorganism that dechlorinates DCE (dichloroethylene) to ETH (ethylene) in the dechlorination reaction shown in FIG. 12 by anaerobic respiration. The optimum range of the oxidation-reduction potential of this microorganism is more than -0.6 V to less than -0.2 V, preferably more than -0.55 V to less than -0.2 V, more preferably -0.5 to -0.2 V. Less than, more preferably −0.4 V to less than −0.2 V, and most preferably −0.3 V. An oxidation-reduction potential of −0.6 V or lower and −0.2 V or higher is not preferable because the DCE dechlorination activity is lower than that in the case of culturing without applying voltage.

  As the DCE dechlorination microorganism, a new or known microorganism can be used. For example, Dehalococcoides.

  The VC dechlorination microorganism is a microorganism that dechlorinates VC (vinyl chloride) to ETH (ethylene) in the dechlorination reaction shown in FIG. 12 by anaerobic respiration. The optimal range of the oxidation-reduction potential of this microorganism is more than -0.5 V to less than -0.2 V, more preferably more than -0.25 V to less than -0.45 V, most preferably -0.4 to -0. 3V. An oxidation-reduction potential exceeding this range is not preferable because the VC dechlorination activity is lower than when culturing without applying a voltage. According to experiments by the present inventors, it was confirmed that the VC dechlorination activity is increased by setting the oxidation-reduction potential to -0.6V. Therefore, it is suggested that there exists an optimum range of the redox potential even in the vicinity of -0.6V.

  A novel or known microorganism can be used as the VC dechlorination microorganism. For example, Dehalococcoides.

  A sulfate-reducing bacterium is a microorganism that reduces sulfate ions to hydrogen sulfide by anaerobic respiration. The optimum range of the oxidation-reduction potential of this microorganism is -0.6 V to -0.1 V, particularly -0.6 V, -0.1 V, whereby the sulfate reduction activity can be enhanced. If it is less than −0.6 V and more than −0.1 V, the sulfuric acid reduction activity may be lower than that in the case of culturing without applying voltage.

  As the sulfate-reducing bacteria, new or known microorganisms can be used. For example, Desulfovibrio, Desulfomicrobium, Desulfobacula, Desulfobacter.

  By controlling the oxidation-reduction potential within the optimal range, the activity of the activity control target microorganism can be enhanced. That is, the activity can be enhanced by the effect of increasing the function of the microorganism to be controlled by activity and the effect of increasing the function by increasing the ratio of the functioning microorganism to be controlled. In other words, the activity of the activity-control target microorganism can be reduced by controlling the oxidation-reduction potential outside the optimum range. That is, the activity can be reduced by the effect of reducing the function by decreasing the number of microorganisms subject to activity control and the effect of reducing the function by reducing the proportion of the functioning microorganisms.

  By using the method for controlling the activity of the activity-controlling microorganism in this way, it is possible to perform an accumulation culture of a specific functional microorganism. In addition, not only the culture but also only a certain kind of microorganisms can function to perform bioremediation. For example, by setting the redox potential of a culture solution containing PCE dechlorinated microorganisms and DCE dechlorinated microorganisms to −0.6 V, only PCE dechlorinated microorganisms are selectively activated and function, and redox If the potential is −0.3 V, only DCE dechlorinated microorganisms are selectively activated.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention. For example, the microorganism activity control method of the present invention may be carried out by a potential control method using a microarray electroculture apparatus 1 ′ as shown in FIG. Specifically, the electrolytic solution 5 is filled with the culture solution 4 and the counter electrode 10 and the reference electrode 11 are immersed. Then, a plurality of microincubators 15 each having a container bottom made of an ion exchange membrane 6 are filled with the culture solution 4, the activity control target microorganism 2 and the redox substance 3, and this is added to the culture solution 4 filled in the electrolytic cell 5. Immerse. The working electrode 9 is immersed in the culture solution 4 of the microincubator 15. That is, the culture tank 7 in the electroculture apparatus 1 shown in FIG. 1 corresponds to the microincubator 15 of the microarray electroculture apparatus 1 ′, and the outer part of the microincubator 15 is the counter electrode in the electroculture apparatus 1 shown in FIG. It corresponds to the tank 8. The working electrode 9, the counter electrode 10 and the reference electrode 11 are connected to a multichannel potential control device 12, and the reference electrode integrated microarray in which the potential of the working electrode 9 of the culture solution 4 of each microincubator 15 can be set precisely. It is an electric culture device. Here, as shown in FIG. 13 (B), the reference electrode 11 is immersed in each microincubator 15 so that the potential of the working electrode 9 of the culture solution 4 of each microincubator 15 can be set strictly. An electrode separation type microarray electrolysis apparatus may be used. In FIG. 13, ● represents the microincubator 15 in a simplified manner.

  By using the microarray electroculture apparatus shown in FIGS. 13A and 13B, various oxidation-reduction potentials can be applied to each microincubator 15. Therefore, it is possible to determine the optimum redox potential that maximizes the activity using a small amount of sample. In addition, by inoculating environmental micro-organisms collected from people into each micro-incubator and uniformly applying a potential that maximizes the target activity, it is possible to detect culture solutions containing highly active micro-organisms. It becomes.

  Further, as shown in FIG. 14, a culture tank 7 is partitioned by a membrane filter 16 that does not allow the microorganisms 2 to be controlled for activity to pass through to form a treatment tank 17, and a treatment liquid 18 containing an environmental pollutant 13 a is placed in the treatment tank 17. It may be inserted and disassembled. That is, the environmental pollutant 13 a moves from the treatment tank 17 to the culture tank 7 through the membrane reactor 16 due to a concentration gradient between the treatment tank 17 and the culture tank 7. When the environmental pollutant 13a is a substance that becomes an electron acceptor for the activity control target microorganism 2 added to the culture tank 7, the environmental pollutant 13a contained in the liquid to be treated 18 is the activity control target microorganism. 2 is decomposed. The decomposed product 13a ′ generated by decomposing the environmental pollutant 13a also moves from the culture tank 7 to the treatment tank 17 through the membrane reactor 16 due to the concentration gradient between the culture tank 7 and the treatment tank 17, so that the treatment tank The liquid 18 to be treated 18 is finally removed from the environmental pollutant 13a and contains a decomposition product 13a ′. Since the microorganism 2 for activity control in the culture tank 7 is activated by controlling the oxidation-reduction potential of the culture solution 4, it becomes a bioreactor capable of efficiently decomposing the environmental pollutant 13a. In this embodiment, when the ion current does not sufficiently flow in the culture solution 4, the redox substance 3 may be added to the solution to be treated 18.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
The optimal oxidation-reduction potential was examined using the microorganism 2 for activity control as a PCE dechlorinating microorganism.

(1) Adjustment of culture solution Culture solution 4a was adjusted as follows. That is, NH ₄ Cl; 0.5 g, K ₂ HPO ₄ ; 0.4 g, MgCl ₂ · 6H ₂ O; 0.49 g, CaCl ₂ · 2H ₂ O; 0.05 g, KCl; 1 mL of a trace metal solution was added to the inorganic salt medium dissolved in the solution. The trace metal solution is CuSO ₄ · 5H ₂ O; 5 mg, CoCl ₂ · 2H ₂ O; 5 mg, NiCl ₂ · 6H ₂ O; 5 mg, NaMoO ₄ · 2H ₂ O; 5 mg, ZnSO ₄ ; 30 mg, MnCl ₂ · 4H ₂ O; 5 mg was prepared by dissolving in 1 L of distilled water. The adjusted culture solution 4a was sterilized by autoclave. In addition, yeast extract; 0.5 g, PCE; 100 ppm (0.1 g added), Fe (III) -EDTA; 0.842 g were further added to the culture solution 4b filled in the culture tank 7, and a filter (0.22 μm) was added. , Millex-GS, MILLIPORE, Ireland). The pH of each of the culture solutions 4a and 4b was adjusted to 7.0 using a dilute sodium hydroxide solution.

(2) Culture apparatus The electric culture apparatus 1 shown in FIG. 2 was used for culture of PCE dechlorinated microorganisms. The electrolytic cell 5 is a two-tank type in which the inside of a glass petri dish with an outer diameter of 75 mm and a height of 90 mm is partitioned by a monovalent cation-permeable exchange membrane (Asahi Kasei, K-192) 6 and one is cultured. The tank 7 was used as the counter electrode tank 8. The culture tank 7 was provided with a working electrode 9 of a carbon plate (40 mm × 70 mm, 4 mm thickness) and a silver / silver chloride reference electrode 11 (HS-205C, Toa DKK). A counter electrode 10 of a carbon plate (40 mm × 70 mm, 4 mm thickness) was installed in the counter electrode tank 8. These three electrodes 9, 10, and 11 were connected to a potential control device (Fuso Seisakusho, POTENTO / GALVANOSTAT model 110) 12 so that the potential of the working electrode 9 in the culture tank 7 could be set precisely.

  The culture tank 7 was filled with the culture solution 4b, and the counter electrode tank 8 was filled with the culture solution 4a.

  In culturing, the electrolytic cell 5 was enclosed in an anaerobic box 14 made of acrylic, and the entire anaerobic box was installed in a thermostat (not shown) set at 30 ° C. Hydrogen gas was constantly injected into the anaerobic box 14 (0.2 L / min) to maintain an anaerobic atmosphere.

(3) Redox potential controllability of culture solution In order to confirm the redox potential controllability of the culture solution, the cyclic voltammogram of the culture solution 4b was measured. For the measurement, an electrochemical analyzer (ALS model 660B, BAS) was used, and the cyclic voltammetry (CV) method was used. At this time, the electrolysis system is a tripolar system, a carbon disk electrode (area: 7.065 mm ² , BAS) is used as a working electrode for observing electrode reactions, and a silver / silver chloride electrode (RE--) is used as a reference electrode. 1B, BAS), and a platinum electrode (1 mm diameter × 5 cm, self-made) was used as a counter electrode for supplying a current.

  The measurement results are shown in FIG. The horizontal axis (potential) is a value relative to the silver / silver chloride reference electrode. When the potential is changed in the oxidation direction, an oxidation current resulting from the reaction of Fe (II) → Fe (III) is generated, and when the potential is changed in the reduction direction, Fe (III) → Fe (II It was confirmed that a reduction current resulting from the reaction of In addition, almost no hysteresis was observed. Therefore, it was revealed that the oxidation-reduction potential can be stably controlled over a long period in the range of −1.0 V to +1.0 V by adding Fe (III) -EDTA to the culture solution.

(4) Optimal redox potential of PCE dechlorinated microorganisms The optimal redox potential of PCE dechlorinated microorganisms was examined.
The electric culture apparatus 1 shown in FIG. 2 was used for culture. The PCE dechlorinating microorganism group was subcultured and used after acquired from soil and acclimatized. The initial addition amount of the PCE dechlorination microorganism group was 5 mL of a suspension of 10 ⁶ to 10 ⁷ cells / mL with respect to 100 mL. The oxidation-reduction potential was -0.7V, -0.6V, -0.5V, -0.4V, -0.3V, -0.2V, and -0.1V. In addition, culture was performed without applying voltage, and this was used as comparative data. The culture period was 3 weeks. After culturing, 1 mL of the culture solution was collected.
Next, the separated culture solution is placed in a vial containing 10 mL of fresh culture solution 4b and inoculated (resuspended). It was done for 9, 12 days. During normal culture, the lid of the vial was closed to prevent PCE volatilization and the vial was placed under anaerobic conditions. The concentration of PCE in this culture was measured by gas chromatography (GC390B, GL Sciences).

  The results are shown in FIG. Under the conditions in which the oxidation-reduction potential was −0.6 V, the residual PCE value was lower than the comparison data. Thus, it was confirmed that the PCE dechlorination activity was higher than the conditions cultured without applying voltage. Under the conditions where the redox potential was −0.7 V and −0.5 V, the PCE dechlorination activity higher than the comparative data was confirmed when the culture period was 2 days. For 6 days showed lower PCE dechlorination activity than the comparative data. Therefore, it was judged that the value greater than -0.7 V to less than -0.5 V, preferably -0.6 V, is the optimum redox potential for the PCE dechlorination microorganism. Further, it has been clarified that the activity of the PCE dechlorinating microorganism decreases at an oxidation-reduction potential of −0.5 V or more and −0.7 V or less.

(5) Relationship between culture period and PCE dechlorination activity The relationship between the culture period at -0.6 V, which was judged to be the optimum oxidation-reduction potential from (4), was examined.
The electric culture apparatus 1 shown in FIG. 2 was used for culture. The PCE dechlorinated microorganism group and the initial amount added were the same as in (4). The culture period was 1, 2, and 4 weeks. In order to obtain comparative data, culture was performed without applying voltage. After culturing, 1 mL of the culture solution was collected.
Next, the collected culture solution was placed in a vial containing 10 mL of fresh culture solution 4b and inoculated (resuspended), and normal (no voltage applied) culture was performed for 4 days. . The concentration of PCE in this culture was measured by gas chromatography.

  The results are shown in FIG. The relative activity on the vertical axis is a numerical value calculated with the PCE concentration of the comparison data as 1. When the culture period was 4 weeks, the PCE dechlorination activity was 3 times higher than when the relative activity was 3, that is, the culture was performed without applying voltage. Therefore, it was confirmed that stable activity can be maintained over a long period of time by controlling the culture solution to the optimal redox potential of the PCE dechlorinating microorganism.

(6) Relationship between the oxidation-reduction potential during cultivation and the number of microorganisms grown An experiment was conducted to investigate the correlation between the oxidation-reduction potential during cultivation and the number of microorganisms grown.
The electric culture apparatus 1 shown in FIG. 2 was used for culture. The PCE dechlorinated microorganism group and the initial amount added were the same as in (4). The oxidation-reduction potential at the time of culture was −0.7V, −0.6V, −0.5V, −0.4V, −0.3V, −0.2V, and −0.1V. Moreover, it culture | cultivated without performing voltage application, and made this into the comparison data. The culture period was 1 week, 2 weeks, and 3 weeks. The number of microorganisms was measured by counting the number of bacteria by observation with an optical microscope.

The results are shown in FIG. It was confirmed that changes in the number of microbial growth were observed depending on the oxidation-reduction potential during culture. When the number of growth after 3 weeks was compared, it increased most at -0.7V and -0.5V, and decreased most at -0.6V. Since -0.7V and -0.5V are potentials that deviate from the optimum redox potential of PCE dechlorinating microorganisms, -0.7V and -0.5V are included in the PCE dechlorinating microorganism group. It is thought that the growth of the microorganisms of this occurred preferentially. From this result, it was suggested that microorganisms other than PCE dechlorinated microorganisms can be selectively cultured if they are cultured as the optimum oxidation-reduction potential for the microorganism.
(7) Current amount in culture medium during culture period When the experiment of (6) was performed, the current value of the culture medium was measured from the first day to the 25th day. The result is shown in FIG. When the redox potential was −0.7 V, −0.6 V, −0.5 V, and −0.4 V, the current value was stabilized on the third day. When the oxidation-reduction potential was −0.3 V and −0.1 V, the current value was stable on the fifth day. When the oxidation-reduction potential was −0.2 V, the current value was stable on the seventh day. Under any oxidation-reduction potential condition, the current value was stable in about one week.

  Therefore, even if iron ions, which are redox substances, are redoxed by microorganisms present in the PCE dechlorination microorganism group, the ratio of Fe (II) and Fe (III) is controlled to be constant, thereby reducing the redox potential. It was confirmed that can be stably controlled from the beginning of the culture. In addition, it was confirmed that the oxidation-reduction reaction of iron ions by microorganisms existing in the PCE dechlorination microorganism group becomes a steady state in about one week under any oxidation-reduction potential condition. Further, from this result, even when the electron acceptor substance for the activity-control target microorganism functions as a redox substance in the culture solution, the activity-control target microorganism is selectively controlled by controlling the redox potential to be constant. It was found that it can be activated. That is, it was found that when the electron acceptor substance is a substance that reversibly changes into an oxidant and a reductant, the electron acceptor substance can be used as the redox substance.

(Example 2)
The optimal oxidation-reduction potential was examined using the microorganism 2 for activity control as a DCE-dechlorinated microorganism.

(1) Adjustment of culture solution Culture solution 4a was adjusted as follows. That is, trisodium citrate dihydrate; 0.78 g, NaHCO ₃ ; 2.52 g, trishydroxyaminomethane; 2.29 g, CaCl ₂ .2H ₂ O; 0.015 g, Na ₂ S; 0.48 g, 10 mL mineral solution and 1 mL Trace element were added to an inorganic salt medium in which FeCl ₂ ; 0.2 g, resazurin; 1 mg was dissolved in 1 L distilled water. The mineral solution was prepared by dissolving MgCl ₂ · 6H ₂ O; 50 g, NaCl; 50 g, KH ₂ PO ₄ ; 20 g, NH ₄ Cl; 30 g, KCl; 30 g in 1 L of distilled water. The trace element is MnCl ₂ · 4H ₂ O; 1 g, CoCl ₂ · 2H ₂ O; 1.9 g, ZnCl ₂ ; 0.7 g, CuSO ₄ · 5H ₂ O; 0.04 g, H ₃ BO ₃ ; 0.06 g , NiCl ₂ · 6H ₂ O; 0.25 g, NaMoO ₄ · 2H ₂ O; 0.44 g was dissolved in 1 L of distilled water to prepare. The adjusted culture solution 4a was sterilized by autoclave. In addition, yeast extract; 0.1 g, DCE; 5.8 ppm (0.0058 g added), Fe (III) -EDTA; 0.842 g were further added to the culture solution 4b filled in the culture tank 7, and a filter (0 .22 μm, Millex-GS, MILLIPORE, Ireland) and used after being sterilized by filtration. Each culture solution was adjusted to pH 7.0 with dilute sodium hydroxide solution.

(2) Culture apparatus The same electric culture apparatus 1 as in Example 1 was used, but the gas injected into the anaerobic box 14 was a mixture of hydrogen and carbon dioxide in order to match the subculture conditions for DCE dechlorinated microorganisms. Gas (H ₂ : CO ₂ = 80: 20) was used.

(3) Optimal redox potential of DCE dechlorinated microorganisms The optimal redox potential of DCE dechlorinated microorganisms was examined.
The electric culture apparatus 1 shown in FIG. 2 was used for culture. The DCE dechlorinating microorganism group was subcultured and used after acquired from soil and acclimatized. The initial addition amount of the DCE dechlorination microorganism group was 5 mL of a suspension of 10 ⁵ to 10 ⁶ cells / mL with respect to 100 mL. The oxidation-reduction potential was -0.7V, -0.6V, -0.5V, -0.4V, -0.3V, and -0.2V. In addition, culture was performed without applying voltage, and this was used as comparative data. The culture period was 3 weeks. After culturing, 1 mL of the culture solution was collected.
Next, the collected culture solution was placed in a vial containing 10 mL of fresh culture solution 4b and inoculated (resuspended), and normal (no voltage application) culture was performed for one week. . During normal culture, the lid of the vial was closed to prevent the volatilization of DCE, and the vial was placed under anaerobic conditions. The concentration of DCE in this culture was measured by gas chromatography.

  The results are shown in FIG. Under the conditions in which the oxidation-reduction potential was cultured at -0.5 V, -0.4 V, and -0.3 V, the residual DCE value was lower than the comparison data. It was confirmed to show chlorine activity. At -0.6 V, the residual DCE value is slightly higher than that of the comparative data. From -0.7 V to -0.3 V, the residual DCE value tends to gradually decrease. At -0.2 V, the DCE residual concentration is low. Increased rapidly. Therefore, it was judged that the value greater than −0.6 V and less than −0.2 V is the optimum oxidation-reduction potential for the PCE dechlorination microorganism. Moreover, it became clear that the activity of DCE dechlorinating microorganisms decreases at an oxidation-reduction potential of −0.6 V or lower and −0.2 V or higher.

(Example 3)
The optimal oxidation-reduction potential was examined with the activity-controlled microorganism 2 as a VC dechlorinated microorganism.

(1) Adjustment of culture solution Culture solution 4a was adjusted as follows. Namely, trisodium citrate dihydrate; 0.78 g, NaHCO ₃ ; 2.52 g, trishydroxyaminomethane; 2.29 g, CaCl ₂ · 2H ₂ O; 0.015 g dissolved in 1 L of distilled water To the medium, 10 mL of mineral solution and 1 mL of Trace element were added. The mineral solution was prepared by dissolving MgCl ₂ · 6H ₂ O; 50 g, NaCl; 50 g, KH ₂ PO ₄ ; 20 g, NH ₄ Cl; 30 g, KCl; 30 g in 1 L of distilled water. The trace element is MnCl ₂ · 4H ₂ O; 1 g, CoCl ₂ · 2H ₂ O; 1.9 g, ZnCl ₂ ; 0.7 g, CuSO ₄ · 5H ₂ O; 0.04 g, H ₃ BO ₃ ; 0.06 g , NiCl ₂ · 6H ₂ O; 0.25 g, NaMoO ₄ · 2H ₂ O; 0.44 g was dissolved in 1 L of distilled water to prepare. The adjusted culture solution 4a was sterilized by autoclave. In addition, yeast extract; 0.1 g, VC; 10 ppm (0.01 g added), Fe (III) -EDTA; 0.842 g were further added to the culture solution 4b filled in the culture tank 7, and a filter (0.22 μm) was added. , Millex-GS, MILLIPORE, Ireland). Each culture solution was adjusted to pH 7.2 with dilute sodium hydroxide solution.

(2) Culture apparatus The same electric culture apparatus 1 as in Example 2 was used.

(3) Optimal redox potential of VC dechlorinated microorganisms The optimal redox potential of VC dechlorinated microorganisms was examined.
The electric culture apparatus 1 shown in FIG. 2 was used for culture. The VC dechlorinating microorganism group was subcultured and used after being acclimatized from the soil. The initial addition amount of the VC dechlorinated microorganism group was 5 mL of a suspension of 10 ⁵ to 10 ⁶ cells / mL with respect to 100 mL. The oxidation-reduction potential was -0.6V, -0.5V, -0.4V, -0.3V, -0.2V, -0.1V, 0.0V. In addition, culture was performed without applying voltage, and this was used as comparative data. The culture period was one week. After culturing, 1 mL of the culture solution was collected.
Next, the collected culture solution was placed in a vial containing 10 mL of fresh culture solution 4b and inoculated (resuspended), and normal (no voltage application) culture was performed for one week. . During normal culture, the lid of the vial was closed to prevent the volatilization of VC, and the inside of the vial was subjected to anaerobic conditions. The concentration of VC and ETH in this culture was measured by gas chromatography.

  The results are shown in FIG. Under the conditions where the redox potential was -0.6V, -0.4V, and -0.3V, the residual VC value was lower than the comparative data, and the amount of ETH generated was high. Therefore, the cells were cultured without voltage application. It was confirmed that the VC dechlorination activity was higher than the conditions. At 0.0V, -0.1V, -0.2V, and -0.5V, the VC dechlorination activity was lower than the comparative data. Therefore, it was judged that a value exceeding -0.5 V to less than -0.2 V was the optimum redox potential for the VC dechlorinating microorganism. In addition, it was suggested that -0.6V can be an optimum redox potential for VC dechlorinated microorganisms.

(4) Relationship between culture period and VC dechlorination activity The relationship between the culture period and VC dechlorination activity was examined.
The electric culture apparatus 1 shown in FIG. 2 was used for culture. The VC dechlorinated microorganism group and the initial amount added were the same as in (3). The oxidation-reduction potential was -0.6V, -0.5V, -0.4V, -0.3V, -0.2V, -0.1V, 0.0V. In addition, culture was performed without applying voltage, and this was used as comparative data. The culture period was 3 weeks. The OD ₆₆₀ value of the culture solution after the culture was measured. A spectrophotometer (U-3010 spectrophotometer, HITACHI) was used for the measurement.

  The results are shown in FIG. It was confirmed that the number of microbial growth was larger than the comparative data under the conditions where the oxidation-reduction potential was -0.6V, -0.4V, and -0.3V. It is confirmed in (3) that the VC dechlorination activity is high at these redox potentials. Therefore, it was confirmed that stable activity can be maintained over a long period of time by controlling the culture solution to the optimum redox potential of the VC dechlorinating microorganism.

Example 4
The optimal oxidation-reduction potential was examined using the microorganism 2 for activity control as a sulfate-reducing bacterium.

(1) Adjustment of culture solution Culture solution 4a was adjusted as follows. That is, sodium lactate; 4.0 mL, NH ₄ Cl; 1.0 g, K ₂ HPO ₄ ; 0.5 g, MgSO ₄ .7H ₂ O; 2.0 g, trisodium citrate dihydrate; 5.0 g, CaSO ₄ · 2H ₂ O; 1.0 g was dissolved in 1 L of distilled water to prepare. The adjusted culture solution 4a was sterilized by autoclave. In addition, yeast extract; 1.0 g, Fe (III) -EDTA; 0.42 g was further added to the culture solution 4b filled in the culture tank 7, and filtered with a filter (0.22 μm, Millex-GS, MILLIPORE, Ireland). It was used after sterilizing by filtration. Each culture solution was adjusted to pH 7.2 with dilute sodium hydroxide solution.

(2) Culture apparatus The same electric culture apparatus 1 as in Example 1 was used. However, in order to match the subculture conditions of sulfate-reducing bacteria, the gas injected into the anaerobic box 14 was nitrogen gas.

(3) Optimum redox potential of sulfate-reducing bacteria The optimal redox potential of sulfate-reducing bacteria was examined.
The electric culture apparatus 1 shown in FIG. 2 was used for culture. The sulfate-reducing bacteria group was subcultured and used after being acclimatized from the soil. The initial addition amount of the sulfate-reducing bacteria group was 1 mL of a suspension of 10 ⁷ to 10 ⁸ cells / mL with respect to 50 mL. The oxidation-reduction potential was 0.4V, −0.1V, and −0.6V. In addition, culture was performed without applying voltage, and this was used as comparative data. The culture period was one week. The concentration of sulfate ion (SO ₄ ²⁻ ) in this culture solution was measured with an ion chromatograph analyzer (ICS-1500, manufactured by DIONEX). Moreover, the sulfate ion concentration was measured also about the culture solution which did not add a sulfate-reducing bacteria group and voltage was not applied, and this was made into control.

  The results are shown in FIG. Under conditions in which the oxidation-reduction potential was -0.6 V and -0.1 V, the sulfate ion concentration was lower than that of the comparative data. Therefore, the sulfate reduction activity may be higher than the conditions cultured without applying voltage. confirmed. At 0.4 V, the sulfate reduction activity was lower than the comparative data. Therefore, -0.6V to -0.1V was judged to be the optimum redox potential for sulfate-reducing bacteria. In particular, it was revealed that the sulfate reduction activity of sulfate-reducing bacteria can be enhanced by controlling the oxidation-reduction potential around -0.1V and around -0.6V.

It is a conceptual diagram which shows an example of embodiment of the microorganisms activity control method of this invention. It is a conceptual diagram of the electroculture apparatus used for experiment. It is a figure which shows the cyclic voltammetry measurement result of the culture solution which added Fe (III) -EDTA. It is a figure which shows the oxidation-reduction potential dependence of PCE dechlorination activity. It is a figure which shows the relationship between a culture | cultivation period and PCE dechlorination activity. It is a figure which shows the oxidation-reduction potential dependence of the microbial growth number of a PCE dechlorination microorganism group. It is a figure which shows the electric current value change of the culture solution during a culture | cultivation period. It is a figure which shows the oxidation-reduction potential dependence of DCE dechlorination activity. It is a figure which shows the oxidation-reduction potential dependence of VC dechlorination activity. It is a figure which shows the oxidation-reduction potential dependence of the microorganisms growth number of VC dechlorination microorganisms. It is a figure which shows the oxidation-reduction potential dependence of sulfate reduction activity. It is a figure which shows a series of dechlorination reaction from PCE to ETH. It is a conceptual diagram which shows the other example of embodiment of the microorganisms activity control method of this invention. It is a conceptual diagram which shows the further another example of embodiment of the microorganisms activity control method of this invention. It is a figure regarding control of the oxidation-reduction potential of a culture solution.

Explanation of symbols

2 Activity-controlled microorganism 3 Redox substances 4, 4a, 4b Culture solution 9 Working electrode 10 Counter electrode 11 Reference electrode 13 Electron acceptor substance

Claims (9)

  Immerse the electrode in a culture solution containing the activity control target microorganism, apply a potential to this electrode to control the oxidation-reduction potential of the culture solution to the optimum range of the activity control target microorganism, and select the activity control target microorganism A method for controlling the activity of microorganisms, characterized in that it is activated dynamically.   The oxidation-reduction potential is controlled by including in the culture solution a redox substance that causes a redox reaction by the potential applied to the electrode, and reducing the oxidized form of the redox substance with the potential applied to the electrode. The method for controlling the activity of microorganisms according to claim 1, which is carried out by controlling the concentration ratio of the body. The method for controlling the activity of a microorganism according to claim 1, wherein the culture solution further contains an electron acceptor substance that functions as an electron acceptor of the microorganism for activity control.   The microorganism activity control method according to claim 1, wherein the activation of the activity control target microorganism is performed in an anaerobic environment. The optimal range of the oxidation-reduction potential is derived by the following procedures (a) to (e), and the microorganisms for activity control are selectively activated in the derived optimal range. A method for controlling the activity of microorganisms.
(A) preparing a plurality of culture solutions containing the activity control target microorganism and an electron acceptor substance functioning as an electron acceptor of the activity control target microorganism
(B) The electrode is immersed in each of the plurality of culture solutions
(C) For each of the plurality of culture solutions, the culture test is performed under various oxidation-reduction potential conditions by changing only the potential applied to the electrode.
(D) A culture test similar to (c) above is performed as a comparative test without applying a potential to the electrodes.
(E) The amount of decrease in the electron acceptor substance in the culture test is compared with the amount of decrease in the electron acceptor substance in the comparative test, and the amount of decrease in the electron acceptor substance in the culture test is greater than that in the comparative test. The oxidation-reduction potential condition that increases the amount is set to the optimum range. The microorganism activity control method according to claim 5, wherein the activity control target microorganism is a tetrachlorethylene (PCE) dechlorination microorganism, and the electron acceptor substance is tetrachloroethylene. The microorganism activity control method according to claim 5, wherein the activity control target microorganism is a dichloroethylene (DCE) dechlorination microorganism, and the electron acceptor substance is dichloroethylene. 6. The method for controlling the activity of microorganisms according to claim 5, wherein the microorganisms for activity control are vinyl chloride (VC) dechlorinated microorganisms, and the electron acceptor substance is vinyl chloride. The method for controlling the activity of a microorganism according to claim 5, wherein the microorganism to be controlled for activity is a sulfate-reducing bacterium, and the electron acceptor substance is sulfate ion.