JP2019062808A - Production method of nutrient solution for microorganisms - Google Patents

Abstract

To provide production methods of nutrient solutions for microorganisms having all prompt effectiveness, sustained-releases, no effluence, and diffusibility.SOLUTION: According to the production method of a nutrient solution for microorganisms of the present invention, by preparing a polymer component containing an aliphatic polyester as a main component, and an aqueous medium containing 40% by mass or more of water, by adding the polymer component to the aqueous medium, and by heating and hydrolyzing it under normal pressure, a nutrient solution for microorganisms which has an insoluble matter and in which at least some of the insoluble matter is the insoluble hydrolysate of the polymer component and the total organic carbon concentration of the solution excluding the insoluble matter is 130 ppm or more is produced.SELECTED DRAWING: None

Description

  The present invention relates to a method of producing a nutrient solution to be provided to microorganisms.

  Contaminated soil produced in factories etc. has been transported to a treatment facility for many years and incinerated to render it harmless. Although this method is excellent in that processing can be performed in a short time and processing can be performed regardless of the type of contaminant, there is a drawback in that costs such as transportation costs are required.

  Therefore, recently, soil remediation methods utilizing microorganisms called bioremediation have been actively studied. Bioremediation is the process of decontaminating pollutants and decontaminating soil by causing specific microorganisms to be present in contaminated soil and feeding them.

  In bioremediation, electron donors such as organic acids are sprayed as a nutrient for microorganisms on contaminated soil to make the reproduction and activity of microorganisms more active. Such a nutrient may be an immediate-acting that can function as a nutrient of microbes immediately after spraying, a sustained release that gradually releases nutrients and feeds nutrients to the microbes over a long period of time, and also nutrients the microbes deep underground. The diffusivity etc. which can supply

  Organic acids and the like that have been used in the prior art function as nutrients as they are, so they have immediate effects because they are dissolved in water and penetrate deep into the ground, and therefore they are excellent in diffusion. However, since it is inferior to sustained release and the runoff from the soil due to ground water etc. is high, there has been a problem that the spraying has to be performed frequently.

  Other than organic acids, for example, Patent Document 1 proposes a polylactic acid-based resin in a solid state and having a weight average molecular weight of 12,000 or less. Although the nutrient of patent document 1 is excellent in the point which has sustained release and the non-spillability which is hard to flow out of the soil due to ground water etc., it has lack of immediate effect and also has diffusivity since it is hardly soluble in water. It was not.

JP, 2011-104551, A

  Therefore, an object of the present invention is to provide a method for producing a nutrient solution for microbes having all of immediate action, sustained release, non-effusive and diffusive properties.

  According to the present invention, a polymer component containing an aliphatic polyester as a main component and an aqueous medium containing 40% by mass or more of water are prepared, the polymer component is charged into the aqueous medium, and heating is conducted under normal pressure for hydrolysis. By decomposing, it has an insoluble matter, at least a part of the insoluble matter is the insoluble hydrolyzate of the polymer component, and the total organic carbon concentration of the liquid excluding the insoluble matter is There is provided a method for producing a nutrient solution for microorganisms, which comprises producing a nutrient solution for microorganisms having a concentration of 130 ppm or more.

In the production method of the present invention, the following embodiments are preferable.
(1) The aqueous medium is an aqueous solution of lactic acid having a concentration of 60% by mass or less.
(2) The aliphatic polyester is polylactic acid.
(3) The weight average molecular weight of the insoluble matter is 12,000 to 20,000.
(4) Polyoxalate is used as a low molecular weight promotion resin which releases an acid by hydrolysis.

  Further, according to the present invention, there is provided a method for supplying nutrients to soil microorganisms, wherein the nutrient solution for microorganisms obtained by the above-mentioned production method is directly sprayed to the soil without solid-liquid separation.

In the present specification, "insoluble" refers to a state of precipitation or dispersion without dissolving in a nutrient solution for a microorganism immediately after production.
In addition, the presence of the insoluble hydrolyzate solid-liquid separates the nutrient solution for microorganisms immediately after production, measures the average molecular weight of the solid content by gel permeation chromatography, and the value is smaller than the average molecular weight of the polymer component of the raw material It can confirm by having become.

  In the present invention, a polymer component containing an aliphatic polyester such as polylactic acid as a main component is hydrolyzed in an atmospheric pressure / aqueous medium. Hydrolysis in such a method is characterized in that small molecules such as monomers and oligomers are easily dissolved in an aqueous medium, and as hydrolysis progresses and the amount of dissolved matter increases, the affinity with the dissolved small molecules is high and It is characterized in that even a slightly larger hydrolyzate of the molecule becomes easier to dissolve than the small molecule. Therefore, as shown in the results of the examples in FIGS. 1 to 3, in the production method of the present invention, the peak shifts to the low molecular weight side in the molecular weight distribution of the insoluble matter for a while from the start of hydrolysis. The weight average molecular weight of the lysate (hereinafter sometimes referred to as average molecular weight) decreases, but if hydrolysis proceeds to a certain extent or more, the soluble hydrolyzate dissolved in the reaction solution increases. In the molecular weight distribution of the insoluble matter, the peak does not shift and the shape collapses. At this stage, the average molecular weight of the insoluble matter is substantially unchanged. If the hydrolysis is continued as it is, the insoluble matter decreases in amount without changing the average molecular weight so much that it eventually disappears and the hydrolysis is completely finished.

  Therefore, according to the present invention, by stopping the hydrolysis when the average molecular weight of the insoluble matter becomes unchanged, it is possible to simply and reliably disperse or precipitate the hydrolyzate without dissolving in the solution. And, the nutrient solution for microorganisms which the organic acid etc. which were used for other hydrolysates and aqueous media etc. dissolved more than fixed amount can be obtained.

  When the nutrient solution is sprayed onto the soil to be treated during bioremediation etc., the soluble hydrolyzate, the organic acid and the organic solvent penetrate deep into the ground and can be immediately consumed by the microorganism.

  On the other hand, the insoluble matter remains near the ground surface after spraying, and is gradually hydrolyzed by the moisture in the environment to be decomposed into microorganisms. Undissolved substances are less soluble in water and less likely to flow out of the soil due to groundwater or the like.

  Therefore, the nutrient solution for microorganisms obtained by the production method of the present invention is excellent in terms of immediate action, diffusion, non-efflux and sustained release.

  If it is attempted to prepare soluble aliphatic polyester, water and insoluble aliphatic polyester respectively in order to obtain the above nutrient solution for microbes and try to mix them, the grinding and stirring operations become complicated, and the cost for equipment etc. However, in the present invention, it is only necessary to stir while heating the polymer component of the raw material in the aqueous medium, so the operation is simple and the manufacturing cost can be reduced. Such an advantage is very industrially advantageous since soil purification requires a large amount of nutrient solution.

5 is a graph showing time-dependent changes in molecular weight distribution of the insoluble matter in Example 1. FIG. It is a graph which shows a time-dependent change of the average molecular weight of the insoluble matter in Examples 1-3. It is the elements on larger scale of FIG.

  In the present invention, hydrolysis is carried out by charging a polymer component containing an aliphatic polyester such as polylactic acid as a main component into an aqueous medium.

<Aqueous medium>
As an aqueous medium, an aqueous medium containing 40% by mass or more of water is used. Preferably, the aqueous medium is water or comprises in water an organic acid and / or an organic solvent in an amount of up to 60% by weight. When the amount of the organic acid is too large, the hydrolyzate is easily dissolved, and it becomes difficult to disperse or precipitate a sufficient amount of insoluble matter in the nutrient solution. Moreover, when there are too many organic solvents, there exists a possibility that the quantity of the water required for a hydrolysis can not be ensured. In addition, since an inorganic acid volatilizes by heating at the time of hydrolysis, it is not preferable.

  As the organic acid, in consideration of the environment, a carboxylic acid is preferable, and lactic acid is particularly preferable.

  As the organic solvent, an organic solvent containing a hydroxy group is preferable, ethylene glycol or methanol is more preferable, and ethylene glycol is particularly preferable because the boiling point is high.

  The aqueous medium other than water may contain other solutes such as inorganic acids and alkali metal salts under the condition that it contains 40% by mass or more of water and does not impair the effect of the present invention, It is preferred not to use any other solute than the organic acid, as it slows down the rate of hydrolysis.

  It is particularly preferable to use, as the aqueous medium, an aqueous solution of an organic acid in which the organic acid is dissolved in water in an amount of 60% by mass or less because hydrolysis proceeds fast.

<Polymer component>
The polymer component contains aliphatic polyester as a main component. That is, the ratio of the aliphatic polyester to the entire polymer component is 50% by mass or more, preferably 70% by mass or more, and the additives or the low molecular weight promoting resin described later account for the components other than the aliphatic polyester.

  As aliphatic polyesters, known ones can be used without limitation. For example, poly (α-hydroxy acid), poly (β-hydroxyalkanoate), poly (ω-hydroxyalkanoate), polyalkylene dicarboxylate and the like can be mentioned. These may be used singly or in combination of two or more. Moreover, although it may be a homopolymer, it may be in the form of a copolymer together with the copolymerization component under the condition that the effect of the present invention is not impaired.

  As a component to form a copolymer, for example, polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, hexanediol, octanediol, dodecanediol, neopentyl glycol, glycerin, pentaerythritol, sorbitan, bisphenol A, polyethylene glycol and the like; Acids, adipic acid, sebacic acid, glutaric acid, decanedicarboxylic acid, cyclohexanedicarboxylic acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, dicarboxylic acids such as anthracenedicarboxylic acid and diesters thereof; glycolic acid, L-lactic acid, D-lactic acid, hydroxypropionic acid Hydroxybutyric acid such as hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, mandelic acid, hydroxybenzoic acid, etc .; glycolide, caprolactone Butyrolactone, valerolactone, propiolactone, lactones such undecalactone; and the like.

  As aliphatic polyesters, poly (α-hydroxy acids) are preferred in view of easy availability, and polylactic acid is particularly preferred. The polylactic acid may be either 100% poly-L-lactic acid or 100% poly-D-lactic acid, or a melt blend of poly-L-lactic acid and poly-D-lactic acid. It may be a random copolymer or block copolymer of lactic acid and D-lactic acid.

  The weight average molecular weight of the aliphatic polyester is preferably 25,000 or more. This is because it has been confirmed that in the case of an aliphatic polyester of such molecular weight, an appropriate amount of soluble hydrolyzate is dissolved in a nutrient solution, and an appropriate amount of insoluble matter is dispersed or precipitated. The upper limit is not particularly limited, but from the viewpoint of shortening the hydrolysis time, 300,000 or less is particularly preferable. The most preferred range of the weight average molecular weight of the aliphatic polyester is 100,000 to 300,000.

  From the viewpoint of the balance of the amount of soluble hydrolyzate and insoluble matter, it is preferable to charge 100 g to 1.5 kg of aliphatic polyester per liter of aqueous medium.

  As the polymer component, if necessary, known plasticizers, heat stabilizers, light stabilizers, antioxidants, UV absorbers, flame retardants, colorants, pigments, fillers, fillers, release agents, antistatic agents Additives such as agents, perfumes, lubricants, foaming agents, antibacterial and antifungal agents, nucleating agents, carboxyl group-binding compounds and the like may further be included. Although the compounding quantity of an additive is suitably determined on the conditions of not impairing the effect of this invention, Usually, it is 5 mass parts or less per 100 mass parts of aliphatic polyester.

  In addition, the polymer component is less susceptible to hydrolysis than the above-mentioned aliphatic polyester and is a resin which releases an acid by hydrolysis, ie, a resin which is easily hydrolyzed to release an acid when mixed with water. It may be contained as a molecular weight promoting resin. In particular, when using a poorly hydrolyzable aliphatic polyester such as polylactic acid as a raw material, a low molecular weight promoting resin is suitably used in order to promote the hydrolysis of such aliphatic polyester to promote the molecular weight reduction. Be done. As the acid released from the low molecular weight promoting resin, it is particularly preferable that the pH (25 ° C.) in an aqueous solution or aqueous dispersion having a concentration of 0.005 g / ml indicates 4 or less, particularly 3 or less. Acids released include oxalic acid and glycolic acid.

  Examples of the low molecular weight promoting resin include polyoxalate and polyglycolic acid, but polyoxalate is preferable. These may be used in the form of a copolymer. Moreover, you may use individually by 1 type and may be used combining 2 or more types. As a component which forms a copolymer, the component which forms the copolymer mentioned by description of the aliphatic polyester of a raw material can be employ | adopted.

  The weight average molecular weight of the low molecular weight promoting resin is generally 1,000 to 200,000.

  The compounding amount of the low molecular weight promoting resin is not particularly limited, but is preferably 1 part by mass or more and less than 100 parts by mass with respect to 100 parts by mass of the aliphatic polyester. More than 1 mass part and less than 50 mass parts are more preferred, and more than 1 mass part and less than 30 mass parts are especially preferred.

  The low molecular weight promoting resin may be used alone as an injection into an aqueous medium, as needed, instead of being mixed with the polymer component.

  Examples of the form of the polymer component include a film or sheet, a cut form of the film or sheet, pellets, particles and the like, and particles are preferable. When the particulate polymer component is used, the insoluble matter inevitably becomes particulate, and there is a merit that it can be used directly as a nutrient solution for microorganisms.

  In the present invention, a polymer component as a raw material is usually charged into an aqueous medium under normal pressure (approximately 1 atm) using a reaction apparatus equipped with a reaction tank, a heating device and a stirring device, and heating and stirring are carried out to add water. Disassemble. It is preferable to make the polymer component into fine particles in advance before charging, since hydrolysis proceeds uniformly.

  The heating temperature is determined by the composition of the aqueous medium, the type of aliphatic polyester used, and the like, but is usually 90 ° C. or more. When the heating temperature is too low, the hydrolysis rate is slow.

  The upper limit of the heating temperature is usually less than the boiling point of the aqueous medium, but when the organic solvent is blended in the aqueous medium, it may be set to not more than the boiling point of the organic solvent. The boiling point of the aqueous medium means the boiling point before the raw material is charged. If the heating temperature is too high, the organic acid or the organic solvent may be volatilized.

  The hydrolysis may be terminated when the average molecular weight of the insoluble matter and the total organic carbon concentration of the reaction solution excluding the insoluble matter reach a desired value, but when the reaction conditions and the average molecular weight are unchanged in advance The relationship between the value of the average molecular weight thereof is confirmed and adjusted, and when the hydrolysis is terminated when the average molecular weight of the insoluble matter becomes difficult to change, the desired nutrient solution for microorganisms is easily and surely obtained. Because it can be

<Microbial nutrient solution>
In the nutrient solution for microorganisms thus obtained, a relatively small molecule hydrolyzate of the polymer component hydrolysates is dissolved, and a relatively large molecule hydrolyzate is precipitated or dispersed as an insoluble matter. doing. For example, when a polymer component substantially consisting only of polylactic acid is used, the soluble hydrolyzate contains polylactic acid monomers, oligomers and the like, and the insoluble hydrolyzate has low average molecular weight and low molecular weight Contains polylactic acid which is larger than the raw material and smaller than the raw material polylactic acid.

  In addition, depending on the composition and amount of the polymer component, the polymer component that has not been hydrolyzed may remain as an insoluble matter in the nutrient solution for microorganisms. Furthermore, when an organic acid or an organic solvent is contained in the aqueous medium, the organic acid dissolves in the liquid excluding the insoluble matter, or a liquid organic solvent coexists.

  Thus, in the nutrient solution for microorganisms of the present invention, the insoluble hydrolyzate of the polymer component and, in some cases, the unreacted polymer component are dispersed or precipitated as the insoluble matter. Further, in the solution excluding the insoluble matter, the soluble hydrolyzate of the polymer component and, in some cases, the organic acid are dissolved, and a liquid organic solvent coexists.

The total organic carbon concentration (TOC) of the nutrient solution excluding the insoluble matter is 130 ppm or more, preferably 1800 ppm or more immediately after production. When the TOC value is low, the amount of dissolved components such as soluble hydrolyzate and organic acid is small, and there is a possibility that rapid action and diffusivity may be lacking. The TOC is measured, for example, under the following conditions.
Device: TOC-5000A manufactured by Shimadzu Corporation
Carrier gas: High purity air Carrier gas flow rate: 150 mL / min
Measurement item: TC (all carbon) / IC (inorganic carbon) / TOC (= TC-IC)
Calibration substance: Sodium hydrogen phthalate and sodium hydrogen carbonate Burning temperature: 680 ° C

  When the TOC of the nutrient solution is in the above numerical range, the total weight average molecular weight of the dissolved components, ie, the soluble hydrolyzate and the optionally contained organic acid and organic solvent, is usually 2,000 or less, in particular 1,1. It is less than 000.

  On the other hand, in the nutrient solution for microorganisms of the present invention, the insoluble matter is dispersed or precipitated as it is after production.

  The weight average molecular weight of the insoluble matter is preferably larger than the soluble hydrolyzate and insoluble, and is preferably in the range of 2,000 to 25,000, particularly 12,000 to 20,000. Such insoluble matter is excellent in sustained release and has an appropriate rate of hydrolysis in the environment. In addition, as described later, the obtained nutrient solution for microbes may be recovered and pulverized only for the insoluble matter, if necessary, and may be used as a microbial solid nutrient agent. It is also excellent in that it is easy.

  The nutrient solution for microorganisms of the present invention may be further blended with sodium hydroxide or the like to be neutralized. By neutralizing, it is possible to obtain a more environmentally friendly nutrient solution for microorganisms.

  The nutrient solution for microorganisms of the present invention is used in various fields, and in particular, it is suitably used as a nutrient solution for microorganisms for soil purification. The insoluble matter contributes to sustained release and non-effluxing, and the soluble hydrolyzate contributes to immediate action and diffusion. Furthermore, when an organic solvent such as an organic acid and methanol is used as the aqueous medium, the organic acid and the organic solvent also become nutrients, which contributes to the immediate effect and the diffusion. Therefore, the nutrient solution for microorganisms of the present invention effectively supplies nutrients to microorganisms only by directly spraying it onto the soil without solid-liquid separation.

  Alternatively, the insoluble matter may be ground in the nutrient solution for microorganisms by a known means such as a ball mill, and the insoluble matter may be dispersed or precipitated as fine particles to form a nutrient solution for slurry-like microorganisms. Such slurry-like nutrient solution for microbes is slightly inferior in non-effluent property, but has an advantage that not only soluble hydrolysates, organic acids and organic solvents but also insoluble matters can penetrate deep into the ground.

  Alternatively, the insoluble matter may be recovered from the nutrient solution for microorganisms by a known means such as filtration and pulverized to obtain a solid microorganism nutrient.

  The invention is illustrated by the following examples.

<Material used>
As PLA (polylactic acid resin), REVODE 101 (d-lactic acid 4.62%) manufactured by Kaisei Biomaterials was used.
Musashino lactic acid 50F (50 mass%) manufactured by Musashino Chemical Laboratory was used as the 50% lactic acid aqueous solution.
A 50% ethylene glycol / water mixed solution was prepared by treating a reagent special grade ethylene glycol (purity 99.7 +%) manufactured by Wako Pure Chemical Industries, Ltd. as 100% ethylene glycol and diluting with pure water.

<Measurement of PLA molecular weight>
Device: gel permeation chromatograph GPC
Detector: Differential Refractive Index Detector RI
Column: SuperMultipore HZ-M (2)
Solvent: chloroform flow rate: 0.5 mL / min
Column temperature: 40 ° C
Sample preparation: 3 mL of a solvent was added to about 10 mg of a sample and left at room temperature.
It confirmed that it melt | dissolved visually and filtered with a 0.45 micrometer filter.
The standard sample used polystyrene.

<Measurement of nutrient total organic carbon content (TOC)>
Device: TOC-5000A manufactured by Shimadzu Corporation
Carrier gas: High purity air Carrier gas flow rate: 150 mL / min
Measurement item: TC (all carbon) / IC (inorganic carbon) / TOC (= TC-IC)
Calibration substance: Sodium hydrogen phthalate and sodium hydrogen carbonate Burning temperature: 680 ° C
Sample preparation: 1 mL of sample is dropped into a 100 mL volumetric flask, and 100 with Milli-Q water
Diluted twice. Take 1 mL of this 100-fold diluted solution and use a 10 mL volumetric flask
The solution was added dropwise and similarly diluted 10 times. A 1000-fold diluted solution was used as a measurement sample.

Example 1
In three 20 mL vials, 5.0 g of PLA was immersed in 5.0 g of Milli-Q water. It stood still for 10 hours, 30 hours, and 52 hours, respectively in the state heated at 95 degreeC.

(Example 2)
In three 20 mL vials, 5.0 g of PLA was immersed in 5.0 g of a 50% aqueous solution of lactic acid. It stood still for 10 hours, 30 hours, and 52 hours, respectively in the state heated at 95 degreeC.

(Example 3)
In three 20 mL vials, 5.0 g of PLA was immersed in 5.0 g of a 50% ethylene glycol / water mixture. It stood still for 10 hours, 30 hours, and 52 hours, respectively in the state heated at 95 degreeC.

After heat treatment, the solid content and the solution were separated by a Pasteur pipette. The solid content was washed twice with 20 mL of pure water and dried by heating at 95 ° C. for 1 hour. The weight average molecular weight (Mw) was measured from the obtained solid content sample piece, and the result is shown in Table 1 and FIGS.
The TOC value (1000-fold dilution) of the solution was measured by the method described above, and the results are shown in Table 2.

As shown in Table 1, when using any of the solvents, the average molecular weight of the undissolved substance decreased with time due to the heat treatment, reaching 25,000 or less in 10 hours. After 30 hours of treatment, the average molecular weight decreased to less than 10,000.
As shown in Table 2, even when any solvent was used, a sufficient amount of total organic carbon in the liquid could be secured at the time of the treatment for 10 hours. From 30 hours of treatment, the TOC value of the solution increased with any of the solvents. As the nutrient solution, when the total organic carbon concentration is increased by 100 ppm or more before dilution, hydrolysis proceeds and so many soluble hydrolysates are preferable.
As mentioned above, the nutrient solution for microorganisms of this invention was able to be manufactured by the process for 10 hours or more. In 10 hours or more and less than 30 hours, a suitable nutrient solution for microorganisms could be produced in that the average molecular weight of the insoluble matter was of a suitable size. In 30 hours or more, the nutrient solution for microorganisms suitable for the point with many soluble hydrolysates was able to be manufactured.

Claims (6)

A polymer component mainly composed of an aliphatic polyester and an aqueous medium containing 40% by mass or more of water are prepared, and the polymer component is charged into the aqueous medium and hydrolyzed by heating under normal pressure,
It has an insoluble matter, at least a part of the insoluble matter is an insoluble hydrolyzate of the polymer component, and the total organic carbon concentration of the liquid excluding the insoluble matter is 130 ppm or more A method for producing a nutrient solution for microorganisms, comprising producing a nutrient solution for microorganisms.   The method according to claim 1, wherein the aqueous medium is an aqueous solution of lactic acid having a concentration of 60% by mass or less.   The method according to claim 1, wherein the aliphatic polyester is polylactic acid.   The production method according to any one of claims 1 to 3, wherein the weight average molecular weight of the insoluble matter is 12,000 to 20,000.   The production method according to any one of claims 1 to 4, wherein polyoxalate is used as a low molecular weight promotion resin which releases an acid by hydrolysis.   The nutrient supply method to soil microorganisms which spread | disperse the soil for nutrient solution obtained by the manufacturing method in any one of Claims 1-5 directly to soil, without solid-liquid separation.