JP5353554B2 - Ethanol production method from woody biomass - Google Patents

Description

  The present invention relates to an ethanol production method using woody biomass as a raw material, and relates to an ethanol production method capable of improving energy efficiency and yield.

Many methods have been implemented in which woody biomass containing cellulose is used as a raw material, enzymes and microorganisms are added, and saccharification and saccharification and fermentation are performed to obtain a sugar solution and a fermentation broth.
In the old days, the production of ethanol used a process in which cellulase was reacted with cellulose as a substrate to enzymatically saccharify cellulose into glucose, and then a process in which glucose was produced by ethanol yeast was used. However, this method has a drawback that the saccharification reaction is delayed as saccharification progresses, and Patent Documents 1 to 3 disclose a method of simultaneously performing saccharification and fermentation. Hereinafter, the term “saccharification and fermentation” in the present specification refers to a method in which saccharification and fermentation proceed simultaneously in the same container. Patent Document 1 discloses a technique using a yeast that also ferments cellobiose in saccharification and fermentation. Patent Document 2 discloses a technique for obtaining a sugar solution in a saccharification step using a cellulase containing β-glucosidase before the saccharification and fermentation step.
Patent Document 3 discloses a technique in which a residue of saccharification and fermentation is subjected to methane fermentation and methane gas is used as thermal energy.
Although patent document 4 is not saccharification fermentation, the technique of collect | recovering ethanol by a catalytic reaction from the synthesis gas produced | generated by hydrothermal gasifying the residue which saccharified and fermented is disclosed.
As disclosed in Patent Documents 3 and 4, technologies using fermentation residues have been disclosed, but a process completely different from saccharification and fermentation is included, and the production line becomes complicated and the burden on costs is high when it is put to practical use. .
According to the saccharification and fermentation method, the saccharification yield is improved as compared with the case where saccharification and fermentation are performed in separate steps. However, according to the study by the present inventors, the saccharification yield is only about 70%. ing.

Japanese Patent Laid-Open No. 5-207855 JP 2002-186938 A JP 2008-104452 A JP 2005-168335 A Japanese Patent Laid-Open No. 63-137692

  The subject in this invention is providing the method of improving a saccharification yield, ie, an ethanol yield, when employ | adopting the saccharification and fermentation process which performs enzyme saccharification and ethanol fermentation simultaneously at the time of ethanol manufacture from woody biomass.

As a result of intensive studies to solve the above-mentioned problems, the present inventors can reduce the energy input to the entire process by mechanically treating the residue obtained from the saccharification and fermentation process and performing saccharification and fermentation. The inventors found that the yield was improved and completed the following invention.
That is, in order to solve the above problems, the present invention employs the following method (1).
(1) After the woody biomass pretreated before first saccharification fermentation step process the biomass to enzymatic saccharification and ethanol fermentation, solid-liquid saccharification fermentation solution obtained from the first saccharification and fermentation process is separated into liquid and residue separation step, the solid-liquid hydroxides residue alkali metal or alkaline earth metal obtained from the separation step, sulfide, alkali is immersed in an aqueous solution of one or more drugs selected from carbonates or sulfites A method for producing ethanol from woody biomass, comprising: an alkali treatment step to be treated; a mechanical treatment step for grinding the alkali-treated residue ; and a residue obtained by the mechanical treatment being returned to the first saccharification and fermentation step .

  With the present invention, there is a promising technology that can improve the yield without increasing the input energy and a method that reduces the cost burden in practical use when producing ethanol from woody biomass. Provided.

The flowchart which shows 1st embodiment of this invention. The flowchart which shows 2nd embodiment of this invention.

Hereinafter, the present invention will be described in more detail.
The woody biomass targeted by the present invention is a biomass made of wood, and bark, sawdust, wood, etc., which are generated from forest land residuals, thinned wood, lumber mills, etc. that are generated at the time of logging or timbering of trees. Chips, sawdust, pruned branches of roadside trees, etc. are common construction waste materials. In the present invention, wood-derived paper, waste paper, pulp, pulp sludge and the like are also included in the woody biomass.
Among the woody biomass mentioned above, the bark of wood is hardly used at present, and it is available in large quantities with a uniform quality at sawmills and chip factories, and it is more flexible and soluble than the wood part of wood. Therefore, it is particularly preferable because it is suitable as a raw material for saccharification and fermentation treatment.
For example, the bark of a tree species such as Eucalyptus or Acacia, which is commonly used for papermaking raw materials, can be obtained in large quantities from a sawmill or chip factory for papermaking raw materials. Preferably used.

<Pretreatment>
In the present invention, the woody biomass is pretreated so that cellulose in the woody biomass can be subjected to a saccharification and fermentation treatment.
The pretreatment can be mechanical treatment, chemical treatment, or any other treatment depending on the type of woody biomass used as a raw material.
The mechanical treatment is to make the raw woody biomass into a size and a state suitable for the saccharification and fermentation treatment in the next step by any mechanical means such as crushing, cutting and grinding. The means and the machine device to be used are not particularly limited. For example, a uniaxial crusher, a biaxial crusher, a hammer crusher, a refiner, a kneader, or the like can be preferably used.

The chemical treatment is to immerse in an aqueous solution of a chemical such as acid or alkali, hot water or the like to make it suitable for the saccharification and fermentation treatment in the next step.
The chemicals used for the chemical treatment are not particularly limited, but for example, one or more selected from alkali metal or alkaline earth metal hydroxides, sulfides, carbonates or sulfites, An alkali treatment or the like that is immersed in an aqueous solution of one or more kinds of chemicals selected from sodium, calcium hydroxide, sodium sulfide, sodium carbonate, sodium sulfite and the like is suitable as the chemical treatment. Further, chemical treatment with an oxidizing agent such as ozone or chlorine dioxide is also possible.
In addition, although the chemical addition amount used for chemical treatment can be arbitrarily adjusted according to the situation, it is 50% or less with respect to the absolute dry mass of the woody biomass used from the aspect of chemical cost reduction. In addition, it is further desirable from the viewpoint of preventing yield reduction due to elution / overdecomposition of cellulose.
In addition, any one of the mechanical treatment and the chemical treatment, which are pretreatments of these woody biomasses, may be performed as necessary. In general, it is preferable to perform chemical treatment after the mechanical treatment step.
In the chemical treatment step in the pretreatment step of the present invention, the immersion time and treatment temperature of the chemical in the aqueous solution can be arbitrarily set depending on the raw materials and chemicals used, but the treatment time is 30 minutes to 1 hour. A temperature of 80 to 130 ° C. is preferred. In addition, since the elution or excessive decomposition of cellulose in the raw material may occur due to strict processing conditions, the processing time is preferably 1 hour or less and the processing temperature is 130 ° C. or less.

<Saccharification and fermentation>
Hereinafter, the saccharification and fermentation system for woody biomass of the present invention will be specifically described with reference to the drawings. However, the present invention is not limited only to the illustrated drawings.
FIG. 1 is a process diagram showing a first embodiment of a saccharification and fermentation system for woody biomass of the present invention. In the system shown in FIG. 1, the pretreated woody biomass raw material is supplied to the first saccharification and fermentation process via the route (A), where the cellulose-degrading enzyme, alcohol yeast and medium are used in the first saccharification and fermentation process. The saccharification of cellulose and alcoholic fermentation are performed simultaneously.

Next, solid- liquid separation is performed by a filtration device, and the liquid component is sent to a distillation separation process consisting of a vacuum distillation device via a path (b) to be separated into a product alcohol fraction and a distillation residue fraction. The alcohol fraction is sent to the alcohol storage tank via the route (d).

In addition, although not shown in figure, it is preferable to sterilize previously with respect to the wood type biomass used as a raw material before a process. When miscellaneous bacteria are mixed in the woody biomass raw material, there is a problem that the miscellaneous bacteria consume sugar when the enzyme is saccharified in a later step and the yield of the product decreases.
The sterilization process may be a method in which the raw material is exposed to a pH at which bacteria are difficult to grow, such as acid or alkali, but may be a method in which the raw material is treated at a high temperature, or a combination of both. About the raw material after an acid and an alkali treatment, it is preferable to use as a raw material, after adjusting to neutrality vicinity or pH suitable for a saccharification and / or saccharification fermentation process. In addition, even when pasteurized at a high temperature, it is preferably used as a raw material after the temperature is lowered to room temperature or a temperature suitable for the saccharification and fermentation process. Thus, by feeding out the raw material after adjusting the temperature and pH, it is possible to prevent the enzyme from being exposed to the outside of the preferred pH and the preferred temperature and being deactivated.

In the first saccharification and fermentation process, appropriate moisture and enzymes and microorganisms such as alcohol yeast necessary for fermentation are added to the pretreated raw material, and the mixture is stirred and dispersed to loosen the wood biomass fibers into a slurry form. Solubilized glucose is fermented by microorganisms to obtain a fermentation product.
The concentration of the raw material is preferably 10 to 30% by mass. If it is less than 10% by mass, there is a problem that the concentration of the product is finally too low and the cost for concentrating the product is increased. Further, as the concentration exceeds 30% by mass, it becomes difficult to stir the raw material, resulting in a decrease in productivity.

Cellulose-degrading enzymes used in the saccharification and fermentation process are enzymes collectively called cellulases having cellobiohydrolase activity, endoglucanase activity, and beta-glucosidase activity.
Each cellulolytic enzyme may be added with an appropriate amount of an enzyme having each activity. However, commercially available cellulase preparations have various cellulase activities as described above, and also have hemicellulase activity. Many commercially available cellulase preparations may be used.

Commercially available cellulase preparations include Trichoderma, Acremonium, Aspergillus, Phanerochaete, Trametes, Humicola, and Humicola. There are cellulase preparations derived from the above. Commercially available products of such cellulase preparations are all trade names, for example, cellulosin T2 (manufactured by HIPI), mecerase (manufactured by Meiji Seika Co., Ltd.), Novozyme 188 (manufactured by Novozyme), multifect CX10L (manufactured by Genencor) ) And the like.
0.5-100 mass parts is preferable and, as for the usage-amount of the cellulase formulation with respect to 100 mass parts of raw material solid content, 1-50 mass parts is especially preferable.

  The reaction conditions are preferably pH 4-7. The temperature is preferably 25 to 50 ° C, more preferably 30 to 40 ° C. The saccharification and fermentation reaction is preferably a continuous type, but may be a batch type. The saccharification and fermentation reaction time varies depending on the enzyme concentration, but in the case of a batch type, it is 10 to 240 hours, more preferably 15 to 160 hours. Also in the case of a continuous type, the average residence time is 10 to 150 hours, more preferably 15 to 100 hours.

Next, fermentation and distillation will be described.
As the microorganism used for fermentation, yeast or the like is used, and a medium or the like may be added simultaneously. As the yeast, well-known yeasts described in Patent Documents 3 and 4, such as Saccharomyces cerevisiae, can be used.
Moreover, the microorganisms may be immobilized. By immobilizing microorganisms, it is possible to omit the process of sending the microorganisms together with the liquid and recovering them again in the next process, or at least reduce the burden on the recovery process and reduce the risk of losing microorganisms. You can also In addition, although there is no merit as to immobilize the microorganism, it is possible to facilitate the recovery of the microorganism by selecting an aggregating microorganism.

In the distillation step, the fermentation product is separated by distillation using a vacuum distillation apparatus. Since the fermentation product can be separated at a low temperature under reduced pressure, inactivation of the enzyme can be prevented. As the vacuum distillation apparatus, a rotary evaporator, a flash evaporator, or the like can be used.
The distillation temperature is preferably 25 to 60 ° C. If it is lower than 25 ° C., it takes time to distill the product, and the productivity is lowered. On the other hand, when the temperature is higher than 60 ° C., the enzyme is heat-denatured to be inactivated, and the amount of newly added enzyme is increased, so that economical efficiency is deteriorated.
The concentration of the fermentation product remaining in the distillation residue fraction after distillation is preferably 0.1% by mass or less. By setting it as such a density | concentration, the amount of fermentation products discharged | emitted with a solid substance in a subsequent solid-liquid separation process can be reduced, and a yield can be improved.

  In the saccharification and fermentation process, hexose derived from cellulose, ie glucose, and pentose derived from hemicellulose, ie mannose, galactose, etc. are alcoholic fermented, but the pentose remains unreacted. Some will do. In such a case, an enzyme that ferments pentose more reliably may be added, or may be treated in a separate step.

  In the present invention, a preliminary saccharification step in which only saccharification is preliminarily performed before the saccharification and fermentation step may be provided. The conditions described in the saccharification and fermentation step can be adopted for the concentration of the raw material, the enzyme to be used and the amount thereof in the preliminary saccharification step. For example, the pH is preferably 4-7. The reaction temperature is preferably 30 to 60 ° C, more preferably 35 to 50 ° C. The reaction process is preferably a continuous process, but may be a batch process. The saccharification time varies depending on the enzyme concentration, but in the case of a batch system, it is 0.5 to 72 hours, more preferably 2 to 48 hours. Also in the case of a continuous type, the average residence time is 0.5 to 48 hours, more preferably 1 to 24 hours.

<Mechanical processing of residue>
The residue obtained by solid-liquid separation from the fermentation liquid obtained from the first saccharification and fermentation treatment step is further subjected to saccharification and fermentation in the second saccharification and fermentation step by adding a mechanical treatment. This is the first embodiment of the present invention, and the flow is shown in FIG. Moreover, the form which returns the residue processed mechanically to the 1st saccharification fermentation process is 2nd embodiment of this invention, and the flow was shown in FIG.
In the case of the first embodiment, the first saccharification and fermentation process and the second saccharification and fermentation process can be independently performed by either batch processing or continuous processing.
In the case of the second embodiment, if the first saccharification and fermentation step is a batch type, the second saccharification and fermentation step is also a batch type, and the residue of the first lot of the first saccharification and fermentation step is processed in the second saccharification and fermentation step. After that, it is mixed with the lot of the second first saccharification and fermentation process, and so on. Therefore, the amount of the pre-processed product newly supplied to the lot of the first saccharification and fermentation process is adjusted so that almost the same amount is processed every lot including the residue to be mixed. In addition, after finishing several lots, it is necessary to discard the residue. The same applies to the continuous treatment, and it is preferable that both the first saccharification and fermentation step and the second saccharification and fermentation step are continuous treatments, and it is necessary to discard the residue at an appropriate timing.
The mechanical treatment of the residue is to make the residue finer by any mechanical means and make it suitable for saccharification and fermentation. Specifically, a process of cutting the residue or grinding with a shearing force is necessary. As a device, a grinder, a refiner, and a kneader used for pulp production can be used. The grinder may be either a stone type or a stone mortar type.
As the refiner, various high-concentration refiner machines used when manufacturing mechanical pulp from wood can be used. There are two types of refiner: a single disk refiner that is ground by a fixed disk and a rotating disk, a double disk refiner that is ground by two counter-rotating disks, and a disk that rotates on both sides of the fixed plate. A twin disc refiner can be used. Further, a conical disc refiner in which the rotating plate is not a flat plate but a conical shape can also be used.
A media stirring wet pulverizer can also be used. This device is a device that rotates a stirrer inserted in a pulverization vessel at a high speed to agitate the media and fibrous cellulose filled in the pulverization vessel to generate shear stress and pulverize. For example, a sand grinder is representative. Device.
Among the above treatments, a refiner is preferable because the residue after the saccharification and fermentation treatment is already flexible. For example, when a refiner treatment is employed in the pretreatment (first pretreatment) before the first saccharification and fermentation step, it is preferable to increase the degree of grinding as the pretreatment of the residue than in the first pretreatment. When both the first pretreatment and the mechanical processing of the residue are performed by the same refiner, it is preferable that the mechanical processing of the residue has a blade clearance of 0.1 mm or more narrower than that of the first pretreatment.

Chemical treatment can be performed at least before or after the mechanical treatment step of the residue treatment step.
For chemical treatment, the same chemicals and treatment conditions as in the first pretreatment are possible.

  The residue subjected to the mechanical treatment is sent to the second saccharification and fermentation step, where the saccharification and fermentation is performed in the same manner as the first saccharification and fermentation step, and is filtered and solid-liquid separated after the treatment. The liquid component is transported to the distillation process, and the solid component is used as a final residue for disposal, combustion, or lignin recovery.

EXAMPLES Next, an Example is shown and this invention is demonstrated further in detail.
In the examples shown below, “%” is based on the total mass unless otherwise specified. Ethanol concentration was measured with a biosensor (Oji Scientific Instruments), and ethanol production was calculated. Moreover, the refiner electric energy required for pre-processing and residue processing was measured using the electric power integrator. The required power was calculated as the power consumed by actually grinding the raw material minus the power required for idling power. The idling power is defined as the electric power required to operate the refiner without grinding the raw material. The yeast used was Saccharomyces cerevisiae, which was cultured in a liquid medium having the following composition at 30 ° C. for 24 hours, and the yeast cells were collected by centrifugation. As a commercially available cellulase, GC220 (cellobiohydrolase activity 100 U / mL, beta glucosidase activity 200 U / mL) manufactured by Genencor Corporation was used.

<Pre-culture liquid medium composition>
Glucose 30g / L
Polypeptone 5g / L
Yeast extract 3g / L
Malt extract 3g / L
pH 5.6

< Reference Example 1>
Chip-shaped eucalyptus globula bark was crushed by attaching a 20 mm round hole screen to a uniaxial crusher (SC-15, manufactured by Saiho Kiko Co., Ltd.) as a woody biomass raw material.
Using a 10 L stainless steel bucket, 500 g of the above raw material absolutely dry is mixed with 1.3 L of 10% sodium carbonate solution, water is added so that the total volume becomes 5 L, and then heat treatment is performed at 100 ° C. for 30 minutes. An alkali treatment was performed.
After the alkali treatment, solid-liquid separation was performed with a 40 mesh screen, and the treated product was ground with a clearance of 0.5 mm using a refiner (manufactured by Kumagai Riki Kogyo, KRK high concentration disk refiner).
After adding 5 L of pure water to the ground product and stirring for 10 minutes, a pre-processed product (hereinafter referred to as pre-processed product A) was obtained by solid-liquid separation using a 40 mesh screen. .
Pretreatment product A is put in a reaction vessel and adjusted to a concentration of 8% by adding water, and then added to 3 g / L polypeptone, 2 g / L yeast extract, and 2 g / L malt extract. The yeast cells after pre-culture and 200 mL of commercially available cellulase were added and subjected to saccharification and fermentation treatment (first saccharification and fermentation treatment) at 30 ° C. for 24 hours, and the ethanol concentration of the saccharification and fermentation broth was measured.
After the first saccharification and fermentation treatment, solid-liquid separation was performed with a 420 mesh screen to obtain a fermentation residue. The residue is treated with the above refiner with a clearance of 0.3 mm, put into an empty reaction vessel, and adjusted to a concentration of 8% by adding water, resulting in 3 g / L polypeptone, 2 g / L yeast extract, and 2 g / L malt extract. The yeast cells after culturing in 350 mL of the liquid medium and 70 mL of commercially available cellulase were added and subjected to saccharification and fermentation treatment (second saccharification and fermentation) at 30 ° C. for 24 hours, and ethanol in the saccharification and fermentation broth The concentration was measured, and the total amount with the amount of ethanol obtained by the first saccharification and fermentation treatment was calculated.

< Reference Example 2>
The amount of ethanol production was calculated in the same manner as in Reference Example 1 except that the refinement treatment of the fermentation residue was performed with a clearance of 0.2 mm.

< Reference Example 3>
The amount of ethanol production was calculated in the same manner as in Reference Example 1 except that the refinement treatment was performed on the fermentation residue with a clearance of 0.1 mm.

<Comparative Example 1>
Chip-shaped eucalyptus globula bark was crushed by attaching a 20 mm round hole screen to a uniaxial crusher (SC-15, manufactured by Saiho Kiko Co., Ltd.) as a woody biomass raw material.
500 g of the above raw material absolutely dry was mixed with 1.3 L of 10% sodium carbonate solution, water was added so that the total volume became 5 L, and then heat treatment was performed at 100 ° C. for 30 minutes to perform alkali treatment.
After the alkali treatment, solid-liquid separation was performed with a 40 mesh screen, and the treated product was ground with a clearance of 0.5 mm using a refiner (manufactured by Kumagai Riki Kogyo, KRK high concentration disk refiner).
5 L of pure water was again added to the ground product and stirred for 10 minutes, and then a pre-processed product that was washed by solid-liquid separation on a 40 mesh screen was obtained.
After adjusting the pre-treatment product to a concentration of 8%, polypeptone 3 g / L, yeast extract 2 g / L, malt extract 2 g / L are added, respectively, and yeast cells after pre-culture in 1 L of the liquid medium and 200 mL of commercially available cellulase was added, saccharification and fermentation treatment (primary saccharification and fermentation treatment) was performed at 30 ° C. for 24 hours, and the ethanol amount obtained by measuring the ethanol concentration of the saccharification and fermentation broth was calculated.

<Comparative example 2>
The amount of ethanol produced was calculated in the same manner as in Comparative Example 1 except that the treated product after the alkali treatment was refined with a clearance of 0.3 mm.

<Comparative Example 3>
The amount of ethanol produced was calculated in the same manner as in Comparative Example 1 except that the treated product after the alkali treatment was refiner treated with a clearance of 0.2 mm.

<Comparative example 4>
The amount of ethanol produced was calculated in the same manner as in Comparative Example 1 except that the treated product after the alkali treatment was refiner treated with a clearance of 0.1 mm.
The results of Examples and Comparative Examples are shown in Table 1 above.

<Comparative Example 5>
The refiner treatment of the fermentation residue was performed in the same manner as in Example 1 except that the treatment with a clearance of 0.3 mm was not performed and the second saccharification fermentation was performed as it was.

From Table 1, the residue after the enzymatic fermentation process of woody biomass can be mechanically processed with little use of electric power, and the overall ethanol yield can be improved by performing saccharification and fermentation again after mechanical processing. There was found.
In addition, the mechanical treatment of woody biomass before enzymatic saccharification consumes more power as the refiner clearance is smaller, and it was 816 wh / g at 0.1 mm, but the pretreated fiber was treated at a clearance of 0.5 mm to obtain fermentation residue. Can be reduced to a total of 228 wh / g, and the ethanol production increased. This is thought to be because the amount of electric power can be reduced because the fiber is fragmented by the fermentation treatment, and the yield of cellulose is improved by the mechanical treatment of the fermentation residue and the ethanol yield is improved.

< Reference Example 4>
It carried out similarly to the reference example 1 until the completion | finish of the 1st saccharification process.
After the first saccharification and fermentation treatment, solid-liquid separation was performed with a 420 mesh screen to obtain a fermentation residue. The fermentation residue was treated with the above refiner with a clearance of 0.3 mm (this is referred to as a residue-treated product B).
On the other hand, the pre-treatment product A before the first saccharification step was obtained again as in Reference Example 1. Pre-treatment product A and residue treatment product B are put in a reaction vessel and adjusted to a concentration of 8% by adding water, and then added to 3 g / L polypeptone, 2 g / L yeast extract, and 2 g / L malt extract, respectively. , Yeast cells after culturing in 1.35 L of the liquid medium and 270 mL of commercially available cellulase are added, saccharification and fermentation treatment (first saccharification and fermentation treatment) is performed at 30 ° C. for 24 hours, and the ethanol concentration of the saccharification and fermentation broth is measured. did.

<Comparative Example 6>
It carried out similarly to the reference example 1 until the completion | finish of the 1st saccharification process.
After the first saccharification and fermentation treatment, solid-liquid separation was performed with a 420-mesh screen to obtain a fermentation residue (referred to as fermentation residue C).
On the other hand, the pre-treatment product A before the first saccharification step was obtained again as in Example 1. Pretreatment product A and fermentation residue C are put in a reaction vessel, and after adding water to adjust the concentration to 8%, polypeptone 3 g / L, yeast extract 2 g / L, and malt extract 2 g / L are added respectively. Yeast cells after culturing in 1.35 L of the liquid medium and 270 mL of commercially available cellulase were added, saccharification and fermentation treatment (first saccharification and fermentation treatment) was performed at 30 ° C. for 24 hours, and the ethanol concentration of the saccharification and fermentation broth was measured. .
Table 2 shows the results of Reference Example 4 and Comparative Example 6 described above.

Claims (1)

After pretreatment of wood biomass, before the first saccharification fermentation step process the biomass to enzymatic saccharification and ethanol fermentation, solid-liquid separation step of saccharification fermentation solution obtained from the first saccharification and fermentation process is separated into liquid and residue, the solid-liquid hydroxides residue alkali metal or alkaline earth metal obtained from the separation step, sulfide, alkali to an alkali treatment by immersing in an aqueous solution of one or more drugs selected from carbonates or sulfites A method for producing ethanol from woody biomass, comprising: a treatment step , a mechanical treatment step of grinding the alkali-treated residue , and returning the residue obtained by the mechanical treatment to the first saccharification and fermentation step .

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