JP2007031591A - Method for decomposing vinyl alcohol-based polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently decomposing a vinyl alcohol-based polymer by using a fungus, especially a method for efficiently decomposing a vinyl alcohol-based polymer in a solid state even not through operation of dissolution or immersion in water. <P>SOLUTION: The method for decomposing a vinyl alcohol-based polymer comprises a process for bringing a fungus of the genus Gloeophyllum or a culture of the fungus into contact with a vinyl alcohol-based polymer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for decomposing a vinyl alcohol polymer. More specifically, the present invention relates to a method for decomposing a vinyl alcohol polymer using a bacterium belonging to the genus Gloeophyllum.sp or a culture of the bacterium.

  Vinyl alcohol polymers (hereinafter sometimes referred to as “PVA”) are used in various applications such as vinylon fibers, films, fiber / paper processing, adhesives, and emulsions. PVA wastes after being used for these applications, particularly solid PVA wastes such as fibers and films that are hardly soluble in water because they are hardly soluble in water, are usually incinerated. In recent years, various plastic wastes such as PVA are required to be incinerated at high temperatures from the viewpoint of preventing environmental pollution caused by dioxin generation during incineration. However, incineration at high temperatures requires not only a large amount of energy, but also requires advanced treatment equipment capable of temperature control, and problems such as damage to the incinerator have been pointed out.

  On the other hand, if an efficient method for decomposing PVA by microorganisms is developed, it will lead to an energy-saving PVA waste decomposition method. In addition, material recycling of PVA waste by composting etc. will be possible.

As methods for degrading PVA using such microorganisms, methods using various bacteria such as Pseudomonas, Sphingomonas, and Bacillus are known (see, for example, Patent Documents 1, 2, 3, and 4). ). In addition, PVA degradation using bacteria has also been reported (see Non-Patent Documents 1 and 2).
Japanese Unexamined Patent Publication No. 7-108297 JP-A-8-140667 JP 2003-250527 A Japanese Patent Laid-Open No. 10-75773 Daniel m. Larking et al., Enhanced Degradation of Polyvinyl Alcohol by Pycnoporus cinnabarium after Pretreatment with Fenton's Reagent, Applied and Environmental Microbiology, 65 (4) 1798-1800 (1999) Amanda Ines Mejia et al., Biodegradation of poly (vinyl alcohol-co-ethylene) with the fungus Phanerochaete chrysosporium, Mat. Res. Innovat., 4, 148-154 (2001)

  However, since the above-mentioned bacteria cannot grow under dry conditions, it is necessary to dissolve PVA in water or to leave it under water conditions in order to decompose PVA. There was a problem that the decomposition efficiency was very poor. Therefore, if bacteria or the like is applied to the decomposition of solid PVA such as a film, an operation for dissolving the polymer in hot water and a large-scale treatment tank are required, and a great deal of energy and cost are still required.

  On the other hand, reports of PVA degradation using the above-mentioned bacteria are all limited to reports of degradation under aqueous conditions or under water conditions, and because of poor degradation efficiency, it has been difficult to apply to industrial applications.

  From the viewpoint of the practical application of the PVA decomposition treatment method, it is required to establish a method in which solid PVA is decomposed regardless of whether or not it is dissolved in water or immersed in water. Currently, a sufficiently efficient method capable of decomposing the PVA with or without dissolving or immersing it in water has not yet been established.

  In view of the above situation, the object of the present invention is to efficiently decompose PVA using microorganisms, in particular, to efficiently decompose solid PVA without dissolving or immersing it in water. It is to provide a way that can be done.

  In order to solve the above problems, the present inventor conducted PVA degradation experiments using various microorganisms.

As a result, the present inventor has found that the genus Bacillus genus, which is a kind of wood brown decaying fungus, can decompose solid PVA regardless of whether it is dissolved in water or immersed in water. Completed.
That is, the present invention
[1] The present invention relates to a method for decomposing a vinyl alcohol polymer, which comprises a step of bringing a cultivated genus Bloemophyllum.

  According to the present invention, a method for efficiently decomposing PVA using a bacterium, particularly a method capable of efficiently decomposing solid PVA without dissolving or immersing in water, is provided. There is an effect that energy-saving PVA waste can be decomposed.

  Moreover, it can be used as compost by composting the decomposed product after decomposing PVA.

  The present invention relates to a method for decomposing a vinyl alcohol polymer, which comprises the step of bringing a bacterium belonging to the genus Bacillus or contact with a vinyl alcohol polymer. By having such a configuration, the solid PVA can be efficiently decomposed without undergoing a dissolution or immersion operation in water.

  Here, the decomposition of PVA means that the main chain of PVA is cleaved when PVA is dissolved in an aqueous solution, and the weight of PVA is reduced when PVA is solid. The cleavage of the main chain of PVA can be evaluated by, for example, measuring the molecular weight of PVA by gel filtration chromatography and confirming the decrease in the molecular weight of PVA. The decrease in the weight of PVA can be evaluated, for example, by measuring the weight of the PVA film with an electronic balance after freeze-drying the PVA film.

The bacterium used in the decomposition method of the present invention may be a bacterium belonging to the genus Pleurotus. From the viewpoint of good PVA degradation, the bacterium belonging to the genus Pleurotus is preferably a bacterium selected from the mushrooms (hereinafter referred to as “Gloeophyllum trabeum”) or the “Gloeophyllum striatum”. Is Gloeophyllum trabeum NBRC number 6430, Gloeophyllum trabeum NBRC number 6509, or Gloeophyllum striatum NBRC number 30341.
Note that the fungus may be a mycelium or a fruit body, and a crushed material or an extract thereof may be used as the fungus.

  The above-mentioned bacteria can be obtained from the National Institute of Technology and Evaluation Technology, and can also be obtained by screening by a known method using the PVA degradation activity as an indicator from nature.

  A medium suitable for culturing the above-mentioned fungus is not particularly limited, and a medium used for normal wood-rot fungus culture and enzyme preparation can be suitably used. Specific examples of such a medium include potato dextrose medium, glucose corn steep liquor medium, malt extract medium, bran medium, Sabouraud medium, high / low nitrogen synthesis medium, wood flour and the like. These media may be used alone or in combination of two or more.

  In the present invention, the fungus culture is not particularly limited as long as it expresses the PVA resolution as long as the fungus is cultured using the medium or the like. It may be a medium-derived component after culturing, an enzyme solution derived from a medium after culturing bacteria, or the like.

  In the degradation method of the present invention, the above-mentioned bacteria or a culture of bacteria (hereinafter sometimes abbreviated as bacteria) may be used alone, or two or more of them may be used together.

  The vinyl alcohol polymer to be decomposed in the decomposition method of the present invention refers to a polymer having a vinyl alcohol unit as a main component. The vinyl alcohol polymer can be prepared by a known chemical synthesis method. The vinyl alcohol polymer is not particularly limited as long as it is such a polymer, and may have other constitutional units within a range in which decomposition proceeds, and has a structure crosslinked with a crosslinking agent described later. Also good.

  Examples of the other structural units include vinyl esters such as vinyl acetate, olefins such as ethylene, propylene, and butylene, acrylic acid and salts thereof, acrylic esters such as methyl acrylate, methacrylic acid and salts thereof, methacrylic acid, and the like. Methacrylic acid esters such as methyl acid, acrylamide derivatives such as acrylamide and N-methylacrylamide, methacrylamide derivatives such as methacrylamide and N-methylol methacrylamide, N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide and the like N-vinyl amides, allyl ethers having a polyalkylene oxide in the side chain, vinyl ethers such as methyl vinyl ether, nitriles such as acrylonitrile, vinyl halides such as vinyl chloride, maleic acid and salts thereof or the like There are anhydride or the like unsaturated dicarboxylic acid esters thereof.

  The introduction of the other structural units can be carried out by a known method, for example, a copolymerization method or a post-reaction method. The content of these structural unit components that are not vinyl alcohol units is usually preferably 44 mol% or less, more preferably 20 mol% or less, and more preferably 5 mol% or less in all the structural units of PVA from the viewpoint of efficient decomposition. Is more preferable.

  The PVA decomposed in the decomposition method of the present invention is also one or more kinds of PVA having different types and introduction amounts of structural units or blends of PVA having different molecular weights, and other polymers such as starch, A blend with a natural polymer such as cellulose or a synthetic polymer having biodegradability such as polylactic acid or polycaprolactone may also be used.

  Further, the PVA decomposed in the decomposition method of the present invention includes a crosslinking agent, a filler, a plasticizer and other thermoplastic resins, a fragrance, a colorant, a foaming agent, and the like within the range in which the object of the present invention is not impaired. Additives such as deodorants, extenders, lubricants, release agents, UV absorbers, antioxidants, processing stabilizers, weathering stabilizers, antistatic agents, flame retardants, mold release agents, reinforcements, etc. Also good.

  Examples of the crosslinking agent include aldehydes such as formaldehyde.

  The content of the additive in the PVA is preferably 30% by weight or less, more preferably 10% by weight or less, from the viewpoint of sufficient decomposition of the PVA.

  The shape of the PVA decomposed in the present invention is not particularly limited, and may be an aqueous solution of PVA, a film, a fiber, an arbitrary molded body, or the like.

  In the step of bringing the bacteria into contact with PVA, there is no particular limitation as long as the bacteria and the like come into contact with the PVA. Examples of the step include a step of incubating the PVA and the bacterium and a medium suitable for culturing the bacterium, a step of directly adding the bacterium and the like to the waste containing the PVA, and the like. In view of sufficient degradation of PVA, a step of incubating the PVA, the bacterium and a medium suitable for culturing the bacterium together is preferable. Hereinafter, the incubation step will be described.

  In the decomposition method of the present invention, incubation refers to maintaining a sample containing at least the PVA, bacteria, etc. in a certain range of temperature conditions. Incubation may be carried out in an apparatus such as a thermostatic bath, and if the temperature condition is kept within a certain range, it is carried out in a state where it is left outdoors or buried in the soil. It may be broken.

  In addition, in the case where PVA, bacteria, etc. and a medium suitable for culturing the bacteria are incubated together, the PVA, bacteria, etc. and the medium may be mixed in the sample, but the PVA resolution of the bacteria, etc. is exhibited. If it is, it may be left in contact without mixing.

  For example, the aspect etc. which add the said microbe to the culture medium containing said PVA and incubate are preferable. In addition, an embodiment in which a culture containing bacteria and a culture medium or a processed product thereof, for example, an enzyme solution obtained by crushing them is brought into contact with PVA and incubated is also preferred.

  The content ratio of PVA, bacteria and medium in the sample can be appropriately selected depending on the type of bacteria used, and is not particularly limited, but from the viewpoint of sufficient PVA degradation and degradation costs, incubation is performed. The dry weight of the PVA is preferably 3 to 200 times, more preferably 10 to 30 times the dry weight of the bacteria at the start. In addition, from the viewpoint of good growth of bacteria and the cost of the medium, the medium volume is preferably 50 to 2500 times, more preferably 100 to 1000 times the bacteria volume at the start of incubation.

  The temperature condition in the incubation step can be appropriately selected depending on the type of bacteria to be used, and is not particularly limited, but is generally 10 ° C. or higher from the viewpoint of good growth of bacteria and sufficient degradation of PVA. Preferably, it is more preferably 20 ° C. or higher. Moreover, it is preferable that this temperature condition is 45 degrees C or less similarly from a viewpoint of the favorable growth of a microbe, and it is more preferable if it is 40 degrees C or less.

  In addition, the relative humidity condition in the incubation step can be appropriately selected depending on the type of bacteria used, and is not particularly limited, but is generally 20 from the viewpoint of good growth of bacteria and sufficient degradation of PVA. % Or more is preferable, and 40% or more is more preferable. The relative humidity is preferably 90% or less, more preferably 80% or less, from the viewpoint of good growth of bacteria and sufficient PVA decomposition.

  Furthermore, the number of days of incubation in the incubation step varies depending on the type of bacteria used, and is not particularly limited. However, from the viewpoint of sufficient PVA degradation, it is generally preferably 1 day or longer. The incubation days are preferably 300 days or less, more preferably 200 days or less, and even more preferably 100 days or less from the viewpoint of economical degradation of PVA.

  In the incubation step, aeration and agitation may be performed from the viewpoint of good growth of bacteria and sufficient degradation of PVA, but aeration and agitation may be omitted if sufficient oxygen supply is possible for growth of the bacteria. . That is, in the incubation step, the PVA can be decomposed by the bacteria regardless of the presence or absence of aeration stirring.

  The decomposition method of the present invention may be a method comprising only a step of bringing a bacterium belonging to the genus Pleurotus genus into contact with PVA as in the step of incubating, but before such step, for example, PVA is converted into small fragments. Other steps such as a step of pulverizing or dissolving or immersing in water, a step of pre-culturing the bacteria, a step of crushing the pre-cultured bacteria into small pieces, and / or a step of sterilizing the PVA or the medium may be included.

  FIG. 1 is a process diagram showing an example of the decomposition method of the present invention. As shown in FIG. 1, the degradation method of the present invention may have a step (C) of incubating the PVA, the bacterium and a medium suitable for culturing the bacterium together.

  In the degradation method of the present invention, the degradation of PVA by bacteria proceeds from the surface to the inside of the PVA. Therefore, when PVA is pulverized into small pieces or dissolved or immersed in water, the surface area of PVA is increased, and the effect of promoting the progress of PVA decomposition is obtained.

  Therefore, the decomposition method of the present invention includes, for example, a step (A) of crushing PVA into small pieces, or dissolving or immersing in water before the step (C) of incubation as shown in FIG. be able to. In the step (A), a method of pulverizing PVA into small pieces is desirable from the viewpoint of energy-saving decomposition treatment of PVA waste.

  In addition, when a growing cell is used in the decomposition method of the present invention, the amount of cells increases in a shorter time, so that the decomposition of PVA can proceed efficiently. Therefore, for example, as shown in FIG. 1, the degradation method of the present invention preferably includes a step (B) of pre-culturing bacteria before the step (C) of incubation.

  The type of medium used in the step of pre-culturing the fungus is not particularly limited. For example, it is preferable to use a medium used for culture of normal wood-rotting fungi such as potato dextrose agar medium or enzyme preparation. it can.

  The temperature condition in the step of pre-culturing the bacterium is not particularly limited, but is generally preferably 10 ° C. or higher, more preferably 20 ° C. or higher, from the viewpoint of good growth of the bacterium. . Moreover, it is preferable that it is 45 degrees C or less similarly from a viewpoint of the favorable growth of a microbe, and it is more preferable if it is 40 degrees C or less.

  The number of days of culture in the step of pre-culturing the fungus varies depending on the type of fungus used, and is not particularly limited. However, from the viewpoint of sufficient growth of the fungus, it is generally preferably 1 day or more, From the viewpoint of sufficient survival of bacteria, it is preferably 30 days or less.

  According to the decomposition method of the present invention as described above, it becomes possible to efficiently decompose PVA without using a fungus to dissolve or immerse in water, and further, energy-saving PVA waste decomposition It is thought that it leads to the processing method.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

Preparation for experiment 1. Preparation of PVA film
As PVA, three types of polyvinyl alcohol shown in Table 1 or polyvinyl alcohol obtained by copolymerizing one type of ethylene with 4% were molded into a PVA film having a thickness of 90 to 100 μm by a 70 ° C. drum casting method. . This PVA film was cut to a size of 50 mm square, and PVA film samples No. 1 to 4 were produced.

2. Bacterial strains In the following Examples and Comparative Examples, the bacteria used in the PVA film sample degradation test are shown in Table 2 below. In addition, each bacterium may be represented by a corresponding test bacterium abbreviation in Table 2.

3. Pre-culture of the used strain As a medium for pre-culture of the used strain, 39.0 g of potato dextrose powder (Nissui Pharmaceutical Co., Ltd .: containing potato leachate powder 4.0 g, glucose 20.2 g, agar 15.0 g) and ion-exchanged water 1.0 L A potato-dextrose medium having the following composition was prepared. The potato-dextrose medium was sterilized at 121 ° C. for 15 minutes in an autoclave, then dispensed in 15 ml portions into a sterilized petri dish (BIOBIK φ90 mm), and solidified to prepare a potato-dextrose medium plate. Subsequently, the used strains listed in Table 2 were inoculated on the potato-dextrose medium plate and cultured at 30 ° C. for 10 days.

Example 1
(i) Bacteria treatment
Prepare a low nitrogen synthesis medium with the composition shown in Table 3 as a medium for PVA film sample decomposition test. After sterilization (121 ° C, 15 minutes), dispense 15 ml each into a sterilized petri dish (BIOBIK φ90 mm). And solidified to prepare a test agar medium. One PVA film sample (No. 1 in Table 1) that had been sterilized by immersion in 70% ethanol for 30 seconds and washed in sterile water for 5 minutes was placed on the medium.

  A potato-dextrose medium plate pre-cultured with the test bacteria a was punched out with a cork borer (manufactured by AS ONE Co., Ltd.) to prepare a bacterial pellet having a diameter of 9 mm and a thickness of 3 mm. One bacterial pellet was placed on the PVA film on the above medium to inoculate it. The medium inoculated in this manner was incubated for 28 days in a thermostatic chamber at 30 ° C. and a humidity of 90%.

  After the incubation, a PVA film sample was collected from the petri dish. After washing mycelia and medium attached to the PVA film sample with ion-exchanged water, freezing the PVA film sample at -80 ° C, then using a vacuum freeze dryer FZ-1 type (LABCONCO) at room temperature (25 ° C) ) And dried at 10 mmHg for 15 to 20 hours.

(ii) Weight reduction rate The weight of the obtained bacteria-treated PVA film sample was measured, and the weight reduction rate from the weight of the film sample at the start of the test was determined based on the following formula.

Weight reduction rate (%) = (film weight at start of test−bacteria treated film sample weight) ÷ film weight at start of test × 100

  In addition, on the above PVA film sample decomposition test medium, No. 1 in Table 1 was obtained. After placing one PVA film sample described in 1 and incubating in the same manner as above without inoculating it, the weight loss rate of the recovered film was determined in the same manner as described above. Table 4 shows values obtained by subtracting this value as a blank value from the weight reduction rate of the above-mentioned fungus-treated sample.

Examples 2-9
A blank from the weight reduction rate of the film after the fungus treatment was performed in the same manner as in Example 1 except that the combination of the test bacteria (selected from the genus Bacillus a-c), the PVA film sample, and the medium for degradation test was changed. The value obtained by subtracting the value was obtained. The results are shown in Table 4.

Comparative Example 1
In the same manner as in Example 1, except that the test bacterium d, which is one of the wood white rot fungi that has been reported to have decomposed aqueous polyvinyl alcohol, was used as the test bacterium. A value obtained by subtracting the blank value from the weight reduction rate was determined. The results are shown in Table 4.

Comparative Examples 2-6
A value obtained by subtracting the blank value from the weight reduction rate of the film after the bacteria treatment was determined in the same manner as in Comparative Example 1 except that the combination of the PVA film sample and the degradation test medium was changed. The results are shown in Table 4.

From the results of Example 1, it was found that the weight reduction of the solid PVA film was caused by the bacterial treatment using the test bacteria a. That is, it was confirmed that the test bacterium a was effective in decomposing solid PVA.
Moreover, from the results of Examples 1 to 6, it was confirmed that the test bacterium a was effective for various solid PVA decompositions having different degrees of polymerization and / or saponification. Moreover, it was also confirmed that the test bacterium a was effective for solid PVA degradation in either the high nitrogen synthesis medium or the low nitrogen synthesis medium.
In addition, from the results of Example 7, it was confirmed that the test bacterium a was also effective in decomposing solid PVA containing a copolymer component.
Moreover, from the result of Example 8, it was confirmed that the test bacterium b belonging to Gloeophyllum trabeum as well as the test bacterium a is also effective for decomposing solid PVA like the test bacterium a.
Furthermore, from the result of Example 9, although not Gloeophyllum trabeum, the test bacterium c belonging to the genus Pleurotus as well as the test bacteria a and b is also effective in decomposing solid PVA as in the test bacteria a and b. It was confirmed that there was.

On the other hand, from the results of Comparative Examples 1 to 6, the degree of polymerization and / or the degree of saponification of either the high nitrogen synthetic medium or the low nitrogen synthetic medium depending on the bacterial treatment using the test bacterium d which is a white rot fungus. Various different PVA films were hardly degraded.
From the above, it was found that the genus Bacillus genus used in the present invention has an effect not seen in conventional microorganisms in the degradation of solid PVA.

Example 10
No. in Table 1 One PVA pellet sample was heated in an autoclave at 110 ° C. for 20 minutes to prepare a 2 wt% PVA aqueous solution. The PVA aqueous solution was added to a liquid medium obtained by removing agar from the low nitrogen synthesis medium shown in Table 3 so that the PVA concentration would be 0.03% by weight, thereby preparing a medium for degradation test. 200 ml of the above-described medium for degradation test and 8 pellets of the test bacteria a prepared in the same manner as in Example 1 were added to a culture bottle (manufactured by Taitec Co., Ltd., φ55 mm) containing a rotor, and 30 ° C.
The stirring culture was performed at 200 rpm. Using the filtrate obtained by filtering the culture solution on day 0 and day 8 through a filter (Millipore, pore size 0.2 μm), the filtrate was subjected to gel filtration chromatography (column TSK gel GMPW _XL , manufactured by Tosoh Corporation). The molecular weight of the PVA inside was measured. Pullulan (produced by Hayashibara Biochemical Laboratories, Inc.) was used as a molecular weight standard substance. As a result, the average molecular weight of PVA was 93,000 on the 0th day, but decreased to 24000 on the 8th day, indicating that PVA was decomposed. That is, it was confirmed that the test bacterium a also has an aqueous PVA decomposition ability.

  According to the decomposition method of the present invention, PVA wastes, particularly solid PVA wastes such as fibers and films that are hardly soluble in water because they are hardly soluble in water, can be decomposed in an energy-saving manner.

It is process drawing showing an example of the decomposition processing method of PVA of this invention.

Claims (3)

  A method for decomposing a vinyl alcohol polymer, comprising the step of bringing a cultivated genus Gloeophyllum.sp or a culture of the bacterium into contact with a vinyl alcohol polymer.   The method according to claim 1, wherein the vinyl alcohol polymer is a solid vinyl alcohol polymer.   The method according to claim 1 or 2, wherein the genus Bacillus genus Mushroom is Gloeophyllum trabeum and Gloeophyllum stratum.

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