JP2011152067A - Method for producing ethanol - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing ethanol by using bark not having been utilized effectively as a cellulose-based biomass not competing with a food by a concurrent saccharification and fermentation method. <P>SOLUTION: The method for producing the ethanol includes: a pretreatment step for preparing fine bark slurry having pH 4-7 by subjecting the bark raw material to a treatment with an alkali solution containing calcium hydroxide and a treatment for mechanically finely pulverizing the pulp raw material; a step of a concurrent saccharification and fermentation treatment for treating the fine bark slurry by the concurrent saccharification and fermentation method; an ethanol and enzyme-recovering step for recovering the formed ethanol from a fermented liquid and returning an enzyme-containing liquid to the step of the concurrent saccharification and fermentation treatment; and a calcium hydroxide-recovering step for recovering the calcium component contained in a fermentation residual fraction separated from the fermentation liquid as a state of calcium hydroxide, and circulating the calcium hydroxide as the calcium hydroxide for the alkali solution. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing ethanol by a simultaneous saccharification and fermentation method in which saccharification and fermentation are simultaneously performed from a bark raw material.

  A tree is divided into an inner xylem and an outer bark with a formation layer where cell division is active as a boundary. The bark accounts for about 10-15% of the total tree mass. In particular, in young eucalyptus, the bark has a relatively low lignin content as compared with the xylem, and is soft and rich in soluble components.

The bark is divided into an outer bark of dead tissue and an inner bark of living tissue.
The outer bark mainly consists of pericytes or cork layers, which protects the wood tissue from mechanical damage and reduces fluctuations in temperature and humidity.
The inner bark consists of mentor elements, parenchyma cells and thick-walled cells. The mentor elements have the function of transporting fluids and nutrients, and the parenchyma has the function of storing nutrients such as starch and is interposed between the mentor elements of the inner bark. . Thick wall cells function as a supporting tissue, are observed in layers like the xylem rings, and are differentiated into bast fibers and scleroids by shape.

  Bark tissue is roughly divided into fine substances including fibers, cork cells, and parenchyma cells. Bark fibers are chemically similar to xylem fibers and are composed of cellulose, hemicellulose and lignin. A fine substance containing cork cells and parenchyma contains a large amount of extracted components, and the cork cell walls are rich in suberins and the fine substance fraction is rich in polyphenols. Thus, bark, unlike xylem, contains many useful soluble components, the amount of which reaches 20-40% of the dry mass, and the fiber fraction has the same fiber as xylem. Has excellent properties. However, bark is not used in timber applications and can be returned to the soil as a fertilizer in the plantation along with branches and roots when pulping in the papermaking process to reduce pulp quality even if mixed slightly. It is peeled off and incinerated at a lumber mill or chip factory, and is not effectively used as woody biomass.

At present, pine, acacia, eucalyptus, etc. are planted as pulp materials for papermaking. Among them, there are more than 500 types of eucalyptus, fast growing, short logging period of 7 to 10 years and growing in dry areas, so it is widely planted all over the world not only for papermaking but also for greening purposes.
On the other hand, effective use of biomass is attracting attention in order to reduce CO ₂ emissions derived from fossil fuels from the viewpoint of preventing global warming. However, in recent years, the production of bioethanol from food-based biomass such as corn has caused an increase in food prices and has caused serious problems such as food shortages in developing countries. Therefore, production of bioethanol from woody biomass that does not compete with food, that is, lignocellulose, has attracted attention.

When using lignocellulose, saccharification that decomposes cellulose into monosaccharides such as glucose is an important step. Unlike starch, lignocellulosic material has a low proportion of cellulose that is saccharified even if it is enzymatically treated as it is. The reason is that lignin and hemicellulose are bound to cellulose. Therefore, it is necessary to make the cellulose easily enzymatically saccharified by physical or chemical pretreatment. As the physical pretreatment, pressure hot water treatment, pretreatment by steaming and explosion are studied (see Patent Documents 1 to 4).
In addition, alkali pretreatment has been studied as a chemical pretreatment (see Patent Documents 5 to 9).

  In each of the above proposals, lignocellulose needs to be pulverized from several mm to several hundred μm in advance, and further, since it is processed under high temperature and high pressure, there is a problem that the energy required for the processing is large and the reaction apparatus is expensive. Generally, the smaller the particle size, the greater the energy required for grinding.

Under such circumstances, NEDO (Independent Administrative Institution New Energy and Industrial Technology Development Organization) pays attention to the above-mentioned bark and reports research results on bark saccharification. In the case of bark, there are few problems of the above-mentioned grinding energy. However, the pretreatment such as alkali treatment is necessary.
On the other hand, as a method for producing ethanol from lignocellulose, there are a step of reacting cellulase with lignocellulose to enzymatically saccharify cellulose to glucose, and then a method of producing ethanol by fermenting glucose with ethanol yeast. It was adopted. However, since this method has a drawback that the saccharification reaction in the saccharification step becomes slower as saccharification progresses, a parallel saccharification and fermentation method in which saccharification and fermentation are performed simultaneously as in Patent Documents 10 to 13 has been studied. Prior Patent Document 9 also describes parallel saccharification and fermentation.
Even when bark is used as a lignocellulose raw material, the situation is the same, and it is considered preferable to employ a parallel saccharification and fermentation method.

JP 2006-136263 A JP 2007-20555 A JP-A-10-117800 JP 59-204997 A Japanese Patent No. 3493026 Japanese Patent Publication No. 63-28597 Japanese Unexamined Patent Publication No. 59-192093 JP 59-192094 A JP 2008-092910 A Japanese Patent Laid-Open No. 05-20785 JP 2002-186938 A JP 2008-104452 A JP 2005-168335 A JP 2004-344084 A

New Energy and Industrial Technology Development Organization, Proceedings of FY2008 Biomass Energy Related Business Results Report Meeting A-4 (February 11, 2009, Professor Kazuhiko Fukushima, Graduate School of Bioagricultural Sciences, Nagoya University)

As described above, when using bark as a raw material, a method of performing pretreatment by alkali treatment and saccharification and fermentation by a concurrent saccharification and fermentation method is considered as a preferred method, but the pH of the slurry in the fermenter that performs the concurrent saccharification and fermentation is: Since it is preferable to adjust to pH 4-7 which is a suitable pH for enzyme saccharification and fermentation, in many cases, it is necessary to neutralize with an acid.
Moreover, since an enzyme is expensive, it is necessary to isolate | separate an enzyme from a saccharification fermentation liquid, and to circulate and use an enzyme again in a saccharification fermentation tank. Therefore, alkali ions and counter ions are accumulated in the saccharification and fermentation tank, and in order to industrially produce continuously, it is an important issue to prevent inhibition of saccharification reaction and fermentation reaction due to ion concentration.

  The present invention, as a result of earnest research to solve the above-mentioned problems when trying to produce ethanol by a parallel saccharification and fermentation method using bark as a cellulosic biomass, adopts calcium hydroxide as an alkali compound for alkali treatment. Thus, the inventors have obtained the knowledge that it is possible to easily avoid inhibition of saccharification reaction and fermentation reaction due to accumulation of alkali ions and counter ions, and have reached the following invention.

(1) A pretreatment step of preparing a fine bark slurry having a pH of 4 to 7 from the fine bark by making the bark raw material into a fine bark by a treatment with an alkali solution containing calcium hydroxide and a treatment for mechanically refining;
A parallel saccharification and fermentation treatment step of separating the liquid fraction containing the produced ethanol and enzyme and the fermentation residue fraction after treating the fine bark slurry by the concurrent saccharification and fermentation method,
Recovering ethanol from the liquid fraction containing ethanol and enzyme, and recovering the enzyme-containing liquid to the parallel saccharification and fermentation treatment step;
The calcium content contained in the fermentation residue fraction separated from the liquid fraction containing ethanol and enzyme produced in the concurrent saccharification and fermentation treatment step is recovered as calcium hydroxide and circulated as calcium hydroxide for the alkaline solution. Calcium hydroxide recovery process,
A method for producing ethanol from a bark raw material, comprising:

(2) In the pretreatment step, a calcium-containing treatment solution comprising a treated alkaline solution separated from the fine bark after the alkali solution treatment and the mechanical refining treatment and a washing treatment solution after washing the fine bark with water A calcium hydroxide recovery step of recovering the calcium content contained in the calcium hydroxide state and circulating as calcium hydroxide for the alkaline liquid,
The method for producing ethanol from the bark raw material according to item (1), comprising:

(3) In the pretreatment step, the fine bark-containing slurry obtained by the treatment with the alkali solution containing calcium hydroxide and the treatment for mechanically refining is separated into a fine bark portion and a treated alkaline solution, After the bark is washed with water and the washing treatment liquid is separated, the fine bark is dispersed in water to prepare a fine bark slurry having a pH of 4 to 7, characterized in (1) or (2) A method for producing ethanol from the bark raw material according to the item.

(4) Item (1) to Item (3), wherein the step of preparing a fine bark slurry by dispersing the fine bark in water includes a step of further neutralizing the slurry. The method of manufacturing ethanol from the bark raw material of any one of these.

(5) The calcium hydroxide recovery step separates the calcium carbonate precipitate produced by the action of carbon dioxide on the calcium-containing treatment liquid generated in the pretreatment step, and calcinates it to convert it into calcium oxide. The method for producing ethanol from a bark raw material according to any one of items (1) to (4), wherein the method comprises a process including a process of refining and recovering as calcium hydroxide.

(6) The calcium hydroxide recovery step includes calcination of a fermentation residue fraction obtained by separating a liquid fraction containing ethanol and an enzyme in the parallel saccharification and fermentation treatment step, thereby converting the calcium content contained therein to calcium oxide. It is a process including a process of converting to saponification and further reducing and recovering as calcium hydroxide, and producing ethanol from the bark raw material according to any one of items (1) to (5) how to.

(7) The ethanol and enzyme recovery step for recovering the generated ethanol from the liquid fraction containing the generated ethanol and the enzyme and returning the enzyme-containing solution to the concurrent saccharification and fermentation treatment step is a fermentation residue associated with the enzyme-containing solution. A method for producing ethanol from a bark raw material according to any one of items (1) to (6), which is a step including a treatment for removing a component.

(8) Step of preparing a fine fermentation residue slurry by further mechanically refining at least a part of the fermentation residue fraction separated from the liquid fraction containing ethanol and enzyme produced in the concurrent saccharification and fermentation treatment step And a parallel saccharification and fermentation treatment step for separating the fine fermentation residue slurry into a liquid fraction containing ethanol and enzyme and a fermentation residue fraction containing the produced ethanol and enzyme, and a liquid fraction containing the produced ethanol and enzyme. The produced ethanol is recovered, and the enzyme-containing liquid fraction is returned as an enzyme source for the parallel saccharification and fermentation treatment step, and the calcium content is hydroxylated from the production ethanol and enzyme recovery step and the fermentation residue fraction separated in the parallel saccharification and fermentation treatment step. Additional ethanol to be processed in an additional ethanol production process consisting of a calcium content recovery process that recovers as calcium state Min and having a step of recovering the (1) to (7) A method for producing ethanol from bark material according to any one of clauses.

(9) Combine at least a part of the liquid fraction containing the produced ethanol and the enzyme in the additional ethanol production step with the liquid fraction containing the produced ethanol and the enzyme obtained from the first concurrent saccharification and fermentation treatment step. The method for producing ethanol from the bark raw material according to (8), characterized in that it is treated in the first production ethanol and enzyme recovery step.

(10) The method for producing ethanol from the bark raw material according to any one of (1) to (9), wherein the raw bark is a bark of a tree belonging to the genus Eucalyptus .

(11) Any one of the items (1) to (10), characterized in that a microorganism belonging to the genus Isachenchia orientalis is used as the yeast for fermentation in the concurrent saccharification and fermentation treatment step. A method for producing ethanol from the bark raw material described in 1.

  The present invention enables efficient enzymatic saccharification and fermentation treatment of bark raw materials in industrial continuous production, and industrial production of bioethanol from bark that has not been industrially used as a woody resource. It will open up a new path. In addition, during saccharification and fermentation, the pH in the system is lowered by the carbon dioxide gas generated as the reaction proceeds, so it is generally necessary to add chemicals to maintain the pH at about 4-7. However, in the case of the method of the present invention, it is sufficient to leave a certain amount of calcium hydroxide, so there is no need to separately prepare chemicals for pH adjustment.

It is process drawing which shows one Embodiment for implementing the method of manufacturing ethanol from the bark raw material of this invention.

Hereinafter, the manufacturing method of ethanol from the bark raw material of this invention is explained in full detail.
In the ethanol production method of the present invention, the bark of a woody plant is used as a raw material. The bark raw material is not particularly limited, but it is preferable to use a bark of a tree belonging to the genus Eucalyptus because the bark is thick and has a high sugar content (cellulose). As the tree species belonging to the genus Eucalyptus (eucalyptus), grandis species, globulus species, nitens species, camaldulensis species, degrupta species, viminalis species, Examples include Europhylla species, Dunnii, and hybrids thereof.

  Eucalyptus bark contains a large amount of calcium oxalate as an inorganic component. In the process of producing ethanol of the present invention, it is recovered and used as a calcium component together with calcium hydroxide derived from calcium hydroxide used as an alkaline solution. Therefore, it is particularly suitable as the bark raw material of the present invention.

  In the present invention, a bark raw material is immersed in an alkaline liquid containing calcium hydroxide as an alkali compound, a pretreatment process for performing a finer bark raw material by performing an alkaline liquid treatment and a mechanical finer treatment, and the refinement The treated bark is treated according to a concurrent saccharification and fermentation process in which a saccharification enzyme and an ethanol-fermenting microorganism are used to produce ethanol.

The bark raw material can be used as it is as it is available, but it can be used as long as it is cut or pulverized from several tens of cm ² to several cm ² in consideration of handling properties during transportation. It can be supplied to the pretreatment process. When the size of the bark raw material is large, the shape and size may be adjusted by mechanical processing such as a cutting machine, chipper, crusher, and hammer crusher. The finer the bark raw material, the higher the saccharification efficiency in the subsequent concurrent saccharification and fermentation treatment step. However, in the case of the method of the present invention, it is less if the bark is first mechanically refined after alkali treatment. It becomes possible to refine | miniaturize with energy amount, and the process which pulverizes the dry bark raw material before a pre-processing process can be abbreviate | omitted.

The amount of alkali compound added to the bark raw material in the pretreatment step is not particularly limited as long as it is an amount that softens the bark. For example, it is 0.1 mass part or more with respect to 100 mass parts of dry bark, Preferably it is 0.1-50 mass parts, More preferably, it is 6-20 mass parts.
Although the temperature for alkali treatment will not be specifically limited if it is the temperature which softens a bark, Preferably it is 10 to 300 degreeC, More preferably, it is 25 to 95 degreeC, Most preferably, it is 60 to 95 degreeC. In the case of less than 10 ° C., the alkali treatment effect may be reduced.

The alkali treatment is particularly preferably performed under normal pressure in that it can be carried out with simple equipment and the input energy can be reduced.
The alkali treatment time is not particularly limited as long as it is sufficient to soften the raw material and promote saccharification of the raw material, but is preferably 1 minute to 72 hours, more preferably 1 minute to 17 hours, most preferably 1 minute to 2 hours.

In the present invention, the bark raw material is immersed in calcium hydroxide-containing water as alkali compound-containing water, and further heated as necessary to perform alkali treatment.
In the present invention, immersing in calcium hydroxide-containing water as an alkali compound may immerse the bark raw material in a state in which the alkaline compound is previously dissolved and / or mixed in water. It may be poured into water at the same time, or the bark raw material and the alkali compound may be mixed in advance and then immersed in water. In any case, it is only necessary that the bark raw material is finally softened in a state of being immersed in alkali compound-containing water.

In the present invention, calcium hydroxide is used as the alkali compound. Calcium hydroxide is less expensive than other alkali compounds and has low solubility, so that it can be easily recovered as a precipitate and reused. Further, even when the solution becomes a diluted solution by washing or the like, it is precipitated as calcium carbonate when neutralized with carbon dioxide, so that the calcium content can be easily recovered.
In the case of calcium hydroxide, even if it is called an alkaline aqueous solution, it has a low solubility, so that a solid content not dissolved is also present at the same time.
The alkali compound concentration of calcium hydroxide-containing water is 0.05% by mass or more, preferably 0.05 to 10% by mass, more preferably 1 to 4% by mass.

The amount of calcium hydroxide added may be an amount that can soften the bark raw material and promote the saccharification reaction by the enzyme. Preferably, it is 0.1-50 mass parts with respect to 100 mass parts of dry bark raw materials. If the amount is less than 0.1 parts by mass, the effect of promoting saccharification by alkali treatment of the raw material may not be sufficient, and if it exceeds 50 parts by mass, the effect reaches a peak.
5-20 mass parts is suitable for the addition amount of water with respect to 1 mass part of dry bark raw materials. When there is more addition amount of water than 20 mass parts, energy required for a heating will increase and an energy balance will deteriorate. When the amount of water added is less than 5 parts by mass, the contact between the bark raw material and calcium hydroxide becomes insufficient, and a sufficient saccharification promoting effect may not be obtained. Since calcium hydroxide has a low solubility of 1.7 g / L, in the alkali treatment step, a sufficient amount of water is added so that the aqueous calcium hydroxide solution is in contact with the raw bark and solid calcium hydroxide. This is very important.

There is no particular limitation on the refining process step for mechanically refining the bark simultaneously with the alkali dipping or after the alkali dipping. Specifically, the bark is ground by a refiner, a grinder or the like.
Said grinding process is a process which grinds a bark raw material with a shearing force. As a device, a grinder and a refiner 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.

  You may refine | miniaturize a bark raw material by performing an alkali treatment and a kneading process simultaneously with a kneading machine with water containing an alkali compound. The kneading treatment is to make the bark fine by applying physical force while mixing with an aqueous solution of an alkali compound, and the apparatus used in the kneading treatment can be a kneader, a disperser, an extruder, a mixer, or the like. However, among these, an apparatus called a kneader whose main purpose is kneading is preferable, and a biaxial kneader is particularly preferably used. Since eucalyptus bark is particularly soft, it can be easily refined simply by treatment with a kneader or the like in the presence of an alkali compound.

In the case of refinement treatment by kneading treatment, the amount of alkali compound added to the bark raw material is not particularly limited as long as it is an amount that can soften the bark, and varies depending on conditions, and can be appropriately selected as necessary. .
For example, the alkali compound is 0.1 part by mass or more, preferably 1 part by mass or more, more preferably 5 parts by mass or more with respect to 100 parts by mass of the dry bark. Even if it is used in excess of 30 parts by mass, the effect reaches a peak and there is a possibility that chemicals and cleaning water are wasted.

  In the case of the refinement | miniaturization process by a kneading process, the range of 1-6 will be suitable if the addition amount ratio of the alkali containing water with respect to a bark is displayed with ml of alkali containing water with respect to 1 g of dry bark. When the addition amount ratio is less than 1, there is a possibility that the alkali treatment for the bark is not sufficiently performed and the saccharification rate is inferior, and the mechanical energy required for fiberization is also increased. When the amount ratio exceeds 6, the heat energy required for heating during the kneading process may increase and become inefficient.

Although the refinement | miniaturization process temperature by a kneading process will not be specifically limited if it is the temperature which can soften a bark, Preferably it is 25-300 degreeC, More preferably, it is 90-200 degreeC. If the temperature is lower than 25 ° C, the reaction may not be completed sufficiently, and if it exceeds 300 ° C, there is a problem of excessive decomposition. The refining time by the kneading process is a time sufficient to soften the bark. If there is, it is not particularly limited, but it is preferably in the range of 30 seconds to 10 minutes.

The finer the bark that has been refined by the kneading process, the higher the subsequent saccharification efficiency. However, since the required energy amount increases, the fiber size is preferably in an appropriate range. Specifically, the average fiber length of the fibers is preferably 2 to 4 mm, and the average fiber diameter is preferably 100 to 400 μm.
By performing the above-described refinement treatment, it is possible to improve the saccharification reaction efficiency by the enzyme in the subsequent concurrent saccharification and fermentation treatment step. In addition, since the bark raw material is softened by the alkali treatment, the energy cost required for the refinement treatment is not a problem as compared with the yield improvement effect.

In the present invention, the bark raw material is concentrated after the pretreatment step including the alkali treatment and the refinement treatment, or after the pretreatment step consisting of the alkali treatment and the kneading treatment. In addition, saccharification and fermentation treatment is performed in the concurrent saccharification and fermentation treatment step with saccharification enzyme and yeast by performing washing, pH adjustment and the like.
The concurrent saccharification and fermentation treatment is carried out by adopting reaction conditions such as the type of enzyme, reaction time, reaction temperature and the like employed in a normal lignocellulosic biomass saccharification treatment method. At the same time, it is carried out by adding yeast and medium for fermenting ordinary sugar.

Cellulolytic enzymes used for saccharification of bark are so-called cellulases, which have cellobiohydrolase activity, endoglucanase activity, and betaglucosidase 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. Since many products are available, commercially available cellulase preparations may be used.

Commercial cellulase preparations include Trichoderma, Acremonium, Aspergillus, Phanerocheet, 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.

  In the present invention, yeast or the like is used as the microorganism for fermentation, and a medium or the like may be added simultaneously. As the yeast, a well-known yeast such as Saccharomyces cerevisiae can be used, but preferably a salt-tolerant yeast is used. As the salt-tolerant yeast, those of the genus Isachenchia orientalis are preferable, and any strain can be used as long as it is capable of growing even in the range of 37 ° C. to 45 ° C. and does not substantially produce protease. . Particularly preferred is alcohol fermentable yeast MF-121 of the genus Issatchenkia orientalis. This strain was deposited with the Patent Organism Depositary, National Institute of Advanced Industrial Science and Technology on May 22, 2003, and was assigned the deposit number FERM P-19368. This strain is described in detail in Patent Document 14.

  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. When this microorganism is used, there is an advantage that the fermentation reaction proceeds stably even when the salt concentration in the reaction vessel increases, and since the fermentation proceeds at a high temperature, the progress of the enzyme reaction is also promoted.

  The pH of the concurrent saccharification and fermentation reaction 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 and fermentation time varies depending on the enzyme concentration, but in the case of a batch type, 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.

  The concentration of the raw material in the saccharification and fermentation process 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.

In addition, before the saccharification and fermentation treatment step, it is preferable to sterilize the bark raw material in advance. When various germs are mixed in the bark raw material, a problem arises that when performing saccharification and fermentation, the germs consume sugar 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 it as a raw material after adjusting to neutrality vicinity or pH suitable for a saccharification and / or saccharification fermentation process 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 present invention, it is preferable to increase the saccharification efficiency by crushing the bark raw material using a uniaxial crusher before the pretreatment step and then performing an alkali treatment in the pretreatment step.
The uniaxial crusher includes a rotary blade attached to a rotary rotor, a pusher that presses a raw material against the rotary blade, and a fixed blade attached to the pusher, and the gap between the rotary blade and the fixed blade This is a device for crushing raw materials.
When the bark raw material is processed using a uniaxial crusher, the bark can be made fibrous with relatively little input energy. The finer the bark of the fiber, the higher the later saccharification efficiency. However, since the amount of energy required for the refinement increases, the size of the fiber is preferably in an appropriate range. Specifically, as a fiber distribution, it is preferable that the ratio of fibers having a fiber length of 3 mm or more is 20% or more of the whole. Further, the ratio of fibers having a fiber length of 3 mm or more is preferably 20% or more and the ratio of fibers having a length of 10 mm or less is preferably 50% or less. Most preferably, the ratio of fibers having a fiber length of 3 mm or more is 20% or more, and the ratio of fibers having a length of 10 mm or more is 10% or less.

In the method of the present invention, since the alkali compound used for the alkali treatment in the pretreatment step is calcium hydroxide, it is possible to separate the bark and the alkali solution after the alkali treatment and return the alkali solution to the alkali treatment step. It can be done relatively easily.
As a method for separating the bark and the alkaline solution after the alkali treatment, the solution is drained after the alkali treatment. As a method for removing liquid, in addition to filtration under normal pressure using a filter or the like, pressure filtration, suction filtration, or centrifugal separation means can be appropriately used.
In the separated lysate, calcium hydroxide as a solid is present in addition to dissolved calcium hydroxide. In the case of the present invention, about 20 to 70% by mass is present in the liquid removal with respect to the input calcium hydroxide. This liquid component can be recycled as it is for alkali treatment.

Through the circulation, the liquid content containing calcium hydroxide is reused for the alkali treatment, so that the amount of calcium hydroxide and water used can be reduced. In addition, since calcium hydroxide adheres to the solid content (bark content) after liquid removal and is postponed, it is necessary to add calcium hydroxide at the time of reuse. Further, if necessary, the organic component may be removed by filtration or the like in the course of the circulating process, and then returned for alkali treatment.
Further, in some cases, calcium hydroxide may be regenerated from the separated liquid through calcination or the like.

The bark that has been drained after the alkali treatment is subjected to a fine treatment by mechanical means as described above. Specifically, the bark is preferably ground by a shearing force.
In the grinding treatment, water may be supplied as necessary. For example, in the case of refiner treatment, it is preferable that 2 parts by mass or more of water is present with respect to 1 part by mass of bark absolutely dry solids. More preferably, water is 5 to 20 parts by mass.
The grinding treatment may be performed immediately after the alkali treatment, followed by the concentration treatment. In that case, the alkali penetrates from the surface of the new fiber generated by grinding, and the effect of the alkali treatment is increased. On the other hand, if fine fibers are generated, there is a risk that the concentration efficiency is lowered.

After the alkali treatment with calcium hydroxide, it is preferable to provide a washing step of washing the bark from which the alkaline solution has been separated by dehydration or the bark that has been subsequently ground with water. In the washing treatment, water is added to the treated product, and the calcium hydroxide adhering to the alkaline treated product is washed away or dissolved in water and discharged. In the washing step, washing can be performed by a fall washer, a concentration washing machine, a pulp washing apparatus, or the like. In addition to the calcium hydroxide component, the calcium oxalate component contained in the bark raw material is also discharged into the effluent of this step. Since the solubility of these calcium components is low, a solid part can be recovered as a solid component by solid-liquid separation, and this can be baked into calcium oxide and then reconstituted (digested) for reuse as calcium hydroxide. Is possible.
Here, before solid-liquid separation, carbon dioxide may be supplied to the slurry to neutralize the liquid and promote the recovery of calcium solids.

Part or all of the liquid containing calcium hydroxide separated in the solid-liquid separation step can be neutralized with carbon dioxide and recovered as calcium carbonate. The produced calcium carbonate is collected as a precipitate in a precipitation tank or the like. Calcium hydroxide can be regenerated from the recovered calcium carbonate and reused for the alkali treatment of the present invention.
The liquid from which calcium carbonate has been removed can be reused as water used in the alkali treatment step and the washing step. In addition, since the environmental load is low, it can be discarded as it is.
Carbon dioxide used in the neutralization step may be a gas, a solid, or a state dissolved in a liquid.
In the case of producing ethanol by subjecting the raw material subjected to the pretreatment of the present invention to concurrent saccharification and fermentation, carbon dioxide is generated as a by-product. Therefore, it is more preferable to recover this carbon dioxide and use it for neutralization. .

  You may perform a grinding process after a washing process, without performing a grinding process at the time of the alkali process by a calcium hydroxide. In this method, there is an advantage that separation of bark and liquid in the washing step is easy. However, since the alkali concentration at the time of the grinding treatment is lowered, the treatment effect by the alkali solution is reduced, and the grinding energy may be increased.

In the present invention, it is possible to provide a distillation step after the concurrent saccharification and fermentation treatment step. 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.

  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.

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

In the ethanol production method of the present invention, after the residue obtained from the saccharification and fermentation process is mechanically treated, it can be further saccharified and fermented.
The mechanical treatment of the residue is to further grind the residue into a state suitable for saccharification and fermentation by any mechanical means. As an apparatus used for the grinding treatment, an apparatus similar to that used in the grinding treatment (first grinding treatment) in the mechanical treatment performed immediately after the alkali treatment step, such as a grinder or a refiner, can be used. Since the residue after fermentation has already become flexible, the use of a refiner is particularly preferred among the above. Moreover, when the refiner process is employ | adopted in the first grinding process, it is preferable to raise the degree of grinding rather than the first grinding process as a grinding process of a fermentation residue. When both the initial grinding process and the fermentation residue grinding process are performed with the same refiner, the mechanical treatment of the fermentation residue may reduce the blade clearance by 0.1 mm or more compared to the initial pretreatment. preferable.

Alkaline treatment can be performed at least before or after the mechanical treatment step of the fermentation residue treatment step.
For the alkali treatment, the same chemicals and treatment conditions as those for the alkali treatment of the bark raw material described above are possible.

Hereinafter, the mechanical treatment of the fermentation residue will be described.
When the mechanically processed fermentation residue obtained from the parallel saccharification and fermentation process is further subjected to the parallel saccharification and fermentation process, the saccharification and saccharification process is different from the first parallel saccharification and fermentation process (first parallel saccharification and fermentation process). A first embodiment (refer to the flow in FIG. 1) in which a fermentation treatment step (second concurrent saccharification and fermentation treatment step) is provided and fermented, and a first parallel saccharification and fermentation treatment step (first) There is a second embodiment of returning to the saccharification and fermentation process step.
In the case of the first embodiment, the first concurrent saccharification and fermentation treatment step and the second concurrent saccharification and fermentation treatment step can be independently performed by either batch processing or continuous processing.

  In the case of the second embodiment, if the first parallel saccharification and fermentation process is a batch type, the second parallel saccharification and fermentation process is also a batch type, and the fermentation residue of the first lot of the first parallel saccharification and fermentation process is After being processed in the second parallel saccharification and fermentation treatment step, it is mixed with the lot of the second parallel saccharification and fermentation treatment step in the first parallel saccharification and fermentation treatment step, and then subjected to the saccharification and fermentation treatment. Therefore, the amount of the pre-treatment product newly supplied as the second lot in the first parallel saccharification and fermentation process is adjusted so that almost the same amount is processed every lot, including the fermentation residue to be mixed. Is done. 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 parallel saccharification and fermentation treatment step and the second parallel saccharification and fermentation treatment step are continuous treatments, and it is necessary to discard the residue at an appropriate timing. The reason why the residue is appropriately discarded is to prevent organic substances other than cellulose from gradually accumulating and inhibiting the saccharification reaction.

  In the case of the first embodiment, the fermentation residue from the first parallel saccharification and fermentation process step subjected to the mechanical treatment is sent to the second parallel saccharification and fermentation process step, and the saccharification and fermentation as in the first parallel saccharification and fermentation process step. And after the treatment, it is filtered and solid-liquid separated. The liquid content is sent to the distillation process, and the solid content is used as the final residue for the calcium content recovery.

Since calcium hydroxide is used as the alkali treatment, calcium oxide can be obtained by firing the fermentation residue, or separating and firing the inorganic component from the residue. This can be dehydrated (digested) to form calcium hydroxide and used for alkali treatment. Further, when the bark is eucalyptus, calcium oxalate in the bark remains as a residue, so that there is an advantage that a large amount of calcium oxide can be obtained by baking the residue.
In particular, in the method of performing the above-described residue grinding treatment, the method of baking the residue in the above-mentioned second concurrent saccharification and fermentation treatment step is the most rational.

The following examples illustrate the method of the present invention with reference to FIG.
[Bark crushing treatment]
In the “bark crushing step 1” in the process chart of FIG. 1, the chip-shaped eucalyptus globulus bark that has passed through a 10 cm screen is crushed using a uniaxial crusher (SC-15, manufactured by Saiho Kiko) under the following conditions. did.
A bark of 723 g (corresponding to an absolute dry mass of 500 g) of bark having a water content of 30.8% by mass was put into a hopper of a uniaxial crusher, and operation was performed using a screen with a round hole of φ20 mm. The bark crushed with a uniaxial crusher was taken in a 10 L stainless steel bucket.

[Alkali treatment]
In the “alkali treatment step 2” in the “pretreatment step” in the process chart of FIG. 1, 62.5 g of calcium hydroxide powder (12.5% by mass against dry bark) may be added to the above crushed bark. After mixing, water was added so that the total amount of water was 5 L. This was also mixed well and then kept at 90 ° C. for 40 minutes for alkali treatment.

(Solid-liquid separation)
After the alkali treatment, in the “solid-liquid separation step 3” in the “pre-treatment step” in the process diagram of FIG. 1, the alkali-treated product and the liquid component which are solid components by centrifugal dehydration using a 40-mesh synthetic fiber mesh The concentration process which isolate | separates was performed.
The alkali-treated concentrate (Wet) was about 1.9 Kg, and the water content was 73.2% by mass. The amount of the liquid was 3.1 kg. This liquid was stored as filtrate (a).

[Grinding]
In the “grinding step 4” in the “pretreatment step” in the process diagram of FIG. 1, the alkali treatment concentrate from the above “solid-liquid separation step” is refined (manufactured by Kumagai Riki Kogyo, KRK high concentration disc refiner). And ground with a clearance of 0.5 mm.

〔Washing〕
In the “cleaning step 5” in the “pretreatment step” in the process diagram of FIG. 1, 5 L of pure water is added to the ground product and stirred for 10 minutes, followed by solid-liquid separation on a 40 mesh screen. In this way, a pretreated product [this is pretreated fine bark (b)] was obtained. The separated liquid was stored as filtrate (c).

[Concurrent saccharification and fermentation treatment]
In the “first parallel saccharification and fermentation process step 6” in the “parallel saccharification and fermentation process step” in the process diagram of FIG. 1, the pretreated fine bark (b) is placed in a reaction vessel, and water is added to adjust the concentration to 8%. After that, the yeast cells were added by polypeptone 5 g / L, yeast (MF-121) extract 3 g / L, and malt extract 3 g / L, and collected by washing centrifugation after pre-culture in the liquid medium 3 L. And 250 mL of commercially available cellulase (Multifect CX16L, Genencor Kyowa Co., Ltd.) was added, and the first saccharification and fermentation treatment (first concurrent saccharification and fermentation treatment) was performed at 37 ° C. for 20 hours, and the ethanol concentration of the fermentation broth was measured.

(Solid-liquid separation)
After the first parallel saccharification and fermentation process in the “first parallel saccharification and fermentation process”, solid-liquid separation is performed on the 40-mesh screen in “solid-liquid separation process 7” in the process diagram of FIG. Obtained.

〔distillation〕
Fermentation liquid containing the produced ethanol and enzyme obtained by separating the treatment liquid subjected to the first concurrent saccharification and fermentation treatment in “first parallel saccharification and fermentation treatment process 6” in the process diagram of FIG. 1 in “solid-liquid separation process 7” ( m) was distilled in “Distillation Step 8” to obtain ethanol (e). Moreover, the enzyme-containing liquid (f) from which ethanol was removed was returned to the first concurrent saccharification and fermentation treatment step (first concurrent saccharification and fermentation treatment step 6).

(Solid-liquid separation)
The enzyme-containing solution (f) from which ethanol has been removed in the distillation step is treated in the “solid-liquid separation step 9”, and the enzyme solution (g) is subjected to the first concurrent saccharification and fermentation treatment step (first concurrent saccharification and fermentation treatment step 6). The solid content was returned to the “baking step 10” as the final residue (h).

[Second grinding]
In the “second grinding step 12” in the process diagram of FIG. 1, the fermentation residue separated in the solid-liquid separation step from the fermentation liquid from the first concurrent saccharification and fermentation treatment step was treated with a refiner with a clearance of 0.3 mm.

[Second concurrent saccharification and fermentation treatment]
In the “second parallel saccharification and fermentation treatment step 13” in the process diagram of FIG. 1, the fermentation residue (d) treated in the second grinding step is placed in an empty reaction vessel, and water is added to adjust the concentration to 8%. , The same polypeptone 5 g / L, yeast extract 3 g / L, and malt extract 3 g / L as those used in the “first concurrent saccharification and fermentation treatment step 6”, and precultured in 1 L of the liquid medium. The yeast cells collected by subsequent washing centrifugation and 70 mL of commercially available cellulase were added, and the parallel saccharification and fermentation treatment (second parallel saccharification and fermentation treatment) was performed at 37 ° C. for 20 hours, and the ethanol concentration of the fermentation broth was measured. And the total amount with the ethanol amount obtained by the 1st simultaneous saccharification and fermentation process was computed. The total amount of ethanol was 58 g.

(Solid-liquid separation)
The saccharification and fermentation broth from the second parallel saccharification and fermentation treatment step in the process diagram of FIG. 1 is separated into solid and liquid in a “solid-liquid separation step 14” by a 40-mesh screen and the final residue (k) and additional ethanol are added. And the fermented liquor (j) containing an enzyme was obtained. The separated fermented liquid (j) is “distilled” together with the fermented liquid (m) containing the produced ethanol and enzyme obtained by separating the fermented liquid from the first parallel saccharification and fermentation process in the solid-liquid separation process. It was sent to Step 8 ”and distilled.

[Treatment of residue and filtrate]
The final residue (k) separated from the fermentation broth from the second parallel saccharification and fermentation treatment step 13 and the enzyme content obtained from the distillation step 8 of the fermentation broth from the first (first) parallel saccharification and fermentation treatment step 6 The final residue (h) separated from the liquid (f) in the solid-liquid separation step 9 was baked together with the “baking step 10” to convert the contained calcium content into calcium oxide.
Further, the “filtrate (a)” obtained from the “solid-liquid separation step 3” of the treated product from the “alkali treatment step 2” of the bark raw material and the alkali-treated bark obtained from the “solid-liquid separation step 3”. The “filtrate (c)” from the “washing step 5” is sent together to the “precipitation step 15”, blown carbon dioxide to separate calcium carbonate as a precipitate, and then sent to the “calcination step 16”. Firing and conversion to calcium oxide. The total amount of calcium oxide obtained from each baking step of the filtrate and fermentation residue was about 92 g. This amount is much higher than the amount expected from the input calcium hydroxide, and most of the calcium content such as calcium oxalate contained in the bark raw material was also converted to calcium oxide and recovered as calcium oxide. Presumed. Calcium oxide from both firing steps 10 and 16 was converted to calcium hydroxide in the digestion (settlement) step 11.

According to the present invention, ethanol can be produced using bark that has not been effectively used and is discarded or left as a raw material in accordance with a very simple process and using inexpensive chemicals. Since a method that can be put into practical use is provided, it opens the way to the practical application of bioethanol production that does not compete with food.

1: Bark crushing process 2: Alkali treatment process 3: Solid-liquid separation process 4: Grinding process 5: Washing process 6: First concurrent saccharification and fermentation treatment process 7: Solid-liquid separation process 8: Distillation process 9: Solid-liquid separation process 10: Firing step 11: Digestion (conversion) step 12: Grinding step 13: Second concurrent saccharification and fermentation treatment step 14: Solid-liquid separation step 15: Precipitation step 16: Firing step a: Treated alkaline solution b: Pretreatment Fine bark c: Washing liquid d: Fermentation residue e: Recovered ethanol f: Enzyme-containing liquid g: Enzyme liquid h: Final residue j: Fermentation liquid k: Fermentation residue l: Calcium carbonate m: Fermentation liquid

Claims (11)

A pre-treatment step of preparing a fine bark slurry having a pH of 4 to 7 from the fine bark by subjecting the bark raw material to a fine bark by a treatment with an alkali solution containing calcium hydroxide and a mechanical fine treatment;
A parallel saccharification and fermentation treatment step of separating the liquid fraction containing the produced ethanol and enzyme and the fermentation residue fraction after treating the fine bark slurry by the concurrent saccharification and fermentation method,
Recovering ethanol from the liquid fraction containing ethanol and enzyme, and recovering the enzyme-containing liquid to the parallel saccharification and fermentation treatment step;
The calcium content contained in the fermentation residue fraction separated from the liquid fraction containing ethanol and enzyme produced in the concurrent saccharification and fermentation treatment step is recovered as calcium hydroxide and circulated as calcium hydroxide for the alkaline solution. Calcium hydroxide recovery process,
A method for producing ethanol from a bark raw material, comprising: In the pre-treatment step, the calcium-containing treatment liquid includes the treated alkaline liquid separated from the fine bark after the alkali liquid treatment and the mechanical refining treatment, and the water washing treatment liquid after washing the fine bark. Calcium hydroxide recovery step of recovering calcium content as calcium hydroxide and circulating as calcium hydroxide for the alkaline liquid,
The method for producing ethanol from the bark raw material according to claim 1, wherein   In the pretreatment step, the fine bark-containing slurry obtained by the treatment with the alkali solution containing calcium hydroxide and the mechanical refining treatment is separated into a fine bark portion and a treated alkaline solution, and the fine bark portion is separated. From the bark raw material according to claim 1 or 2, which is a step of preparing a fine bark slurry having a pH of 4 to 7 by dispersing the fine bark in water after washing with water and separating the washing treatment liquid. A method for producing ethanol.   4. The method according to claim 1, wherein the step of preparing the fine bark slurry by dispersing the fine bark content in water includes a step of further neutralizing the slurry. To produce ethanol from raw bark raw material.   The calcium hydroxide recovery step separates the calcium carbonate precipitate produced by the action of carbon dioxide on the calcium content-containing treatment liquid generated in the pretreatment step, and calcinates it to convert it into calcium oxide, which is further reduced. The method of manufacturing ethanol from the bark raw material of any one of Claims 1-4 characterized by the process including the process collect | recovered as calcium hydroxide.   The calcium hydroxide recovery step converts the calcium content contained in the parallel saccharification and fermentation treatment step by calcining the fermentation residue fraction obtained by separating the liquid fraction containing the produced ethanol and the enzyme into calcium oxide. The method for producing ethanol from a bark raw material according to any one of claims 1 to 5, wherein the method further comprises a process comprising a process of further refining and recovering as calcium hydroxide.   The produced ethanol is recovered from the produced ethanol and the liquid fraction containing the enzyme, and the enzyme-containing solution is returned to the parallel saccharification and fermentation treatment step. The ethanol and enzyme recovery step removes the fermentation residue accompanying the enzyme-containing solution. The method of manufacturing ethanol from the bark raw material of any one of Claims 1-6 characterized by the process including the process to perform.   A step of preparing a fine fermentation residue slurry by further mechanically refining at least a part of the fermentation residue fraction separated from the liquid fraction containing ethanol and enzyme produced in the parallel saccharification and fermentation treatment step; A parallel saccharification and fermentation treatment step for separating a fine fermentation residue slurry into a liquid fraction containing ethanol and enzyme and a fermentation residue fraction by performing a simultaneous saccharification and fermentation treatment, and a production ethanol from the liquid fraction containing the production ethanol and enzyme Collected ethanol to return the enzyme-containing liquid fraction as an enzyme source for the parallel saccharification and fermentation treatment step and the enzyme recovery step, and the calcium content from the fermentation residue fraction separated in the parallel saccharification and fermentation treatment step to a state of calcium hydroxide As an additional ethanol production process consisting of a calcium content recovery process It characterized by having a step of yield, a method for producing ethanol from the bark material according to any one of claims 1-7.   At least part of the liquid fraction containing the produced ethanol and the enzyme in the additional ethanol production step is combined with the liquid fraction containing the produced ethanol and the enzyme obtained from the first concurrent saccharification and fermentation treatment step. The method for producing ethanol from a bark raw material according to claim 8, wherein the ethanol is treated in an ethanol recovery step and an enzyme recovery step.   The method for producing ethanol from a bark raw material according to any one of claims 1 to 9, wherein the raw bark is a bark of a tree belonging to the genus Eucalyptus. The bark raw material according to any one of claims 1 to 10, wherein a microorganism belonging to the genus Isachenchia orientalis is used as a yeast for fermentation in the concurrent saccharification and fermentation treatment step. How to manufacture.

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