JP6375645B2 - Ethanol production method from lignocellulose - Google Patents

Description

The present invention relates to a method for efficiently producing ethanol by suppressing contamination of various germs occurring in a process that causes problems in a method for producing ethanol from biomass containing lignocellulose.

Attempts to produce ethanol from biomass resources such as bagasse, rice straw, and wood chips, which are renewable resources, and to use them as energy and chemical raw materials are underway in Japan and overseas.
As a method for producing monosaccharides and small saccharides as fermentation substrates from polysaccharides contained in plant biomass, there is an enzymatic saccharification method in which hydrolysis is performed using an enzyme or a microorganism that produces the enzyme. By enzymatic decomposition, cellulose and hemicellulose contained in the biomass are decomposed to produce hexoses such as glucose, galactose and mannose, and pentoses such as xylose and arabinose. These hexose and pentose sugars are assimilated by yeast and converted to ethanol.

Since raw materials, medium components, water, enzymes, yeast, and the like supplied to the ethanol production process may contain various germs, it is desirable to remove the germs as much as possible before supplying them to the production process. In the process of producing ethanol continuously, if miscellaneous bacteria grow in the process during production, the growth of yeast is suppressed and ethanol productivity is lowered. Therefore, in a continuous ethanol production process, it is an important issue to increase the productivity of ethanol to efficiently suppress contamination with a simple method.

In order to solve the above problem, a method for inhibiting the growth of various bacteria using acidic electrolyzed water in a method for producing ethanol from a saccharide raw material has been reported (Patent Document 1). In addition, in a method for producing ethanol from a fruit juice, a method for suppressing the growth of various bacteria using an acidic substance has been reported (Patent Document 2). However, in the above method, it is necessary to make the pH of the culture solution acidic, so that the culture cannot be performed under the culture conditions suitable for the action of the enzyme and the growth of yeast, or not only the culture apparatus but also the production line (pipe), etc. There is a concern that the effect is insufficient as a method aiming at suppression of various bacteria in the entire process including.
Therefore, in the process of continuously producing ethanol, the growth of bacteria in the entire process including not only the culture tank but also the line is suppressed, and even if bacteria are contaminated from the outside during continuous operation, It is desired to develop a method for efficiently suppressing the above in a simple manner.

JP 2009-261377 A JP 2011-167164 A

    An object of the present invention is to efficiently produce a variety of bacteria generated in an ethanol production process (all processes including a device such as a culture tank and a line) in a method for producing ethanol from lignocellulose-containing biomass by a simple method. It is providing the ethanol production method with high productivity by suppressing.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention produced ethanol from a lignocellulosic raw material by producing ethanol after washing the ethanol production equipment with an alkaline aqueous solution. The inventors have found that it is possible to suppress contamination with germs occurring in the production facility, and that ethanol productivity can be maintained at a high level, and the following invention has been completed.

(1) A method for producing ethanol from a lignocellulosic material, wherein ethanol is produced after washing the ethanol production facility with an alkaline aqueous solution in the method for producing ethanol from a lignocellulosic material.

(2) The method for producing ethanol from a lignocellulosic raw material according to (1), wherein the concentration of the alkaline aqueous solution is 1 to 10 % by mass.

(3) The method for producing ethanol from a lignocellulosic material according to (1) or (2), wherein the alkaline aqueous solution is circulated in the ethanol production process.

(4) The method for producing ethanol from a lignocellulosic raw material according to any one of (1) to (3), wherein the time for contacting the ethanol production facility with an alkaline aqueous solution is 1 minute or longer. .

(5) The method for producing ethanol from a lignocellulosic raw material according to any one of (1) to (4), wherein the temperature of the alkaline aqueous solution is 35 to 85 ° C.

According to the present invention, in the method for producing ethanol from lignocellulosic raw materials, it is possible to suppress contamination of germs occurring in the ethanol production facility, and the ethanol productivity can be maintained at a high level.

It is a figure which shows the process of manufacturing ethanol from the lignocellulose raw material of this invention.

  Hereinafter, the present invention will be described in more detail.

<Lignocellulose raw material>
As a lignocellulosic raw material used as a raw material in the method of the present invention, as a woody system, chips or bark of papermaking trees, forest land residual materials, thinned wood, etc., sprouts generated from stumps of woody plants, sawmills, etc. Sawdust or sawdust that is generated, pruned branches and leaves of street trees, building waste, etc., and herbaceous agricultural waste such as kenaf, rice straw, straw, corn cob, bagasse, industrial crop residues such as oil crops and rubber, and Examples include wastes (for example, EFB: Empty Fruit Bunch), herbaceous energy crops Eliansus, Miscanthus, and Napiergrass.
Further, as biomass, food waste such as paper derived from wood, waste paper, pulp, pulp sludge, sludge, sewage sludge, and the like can be used as raw materials. These biomasses can be used alone or in combination. The biomass can be used as a dry solid, a solid containing water, or a slurry.

  Examples of the woody lignocellulosic raw material include Eucalyptus genus plants, Salix genus plants, Poplar genus plants, Acacia genus plants, and Cryptomeria genus plants. Plants, genus Acacia and willow genus are preferable because they can be easily collected in large quantities as raw materials. Among the lignocellulosic raw materials derived from woody plants, forest land remnants (including bark and leaves) and bark are preferable. For example, bark of tree species such as Eucalyptus genus or Acacia genus commonly used for papermaking raw materials can be obtained in large quantities stably from lumber mills and chip factories for papermaking raw materials. Preferably used.

<Mechanical treatment process>
In the present invention, the lignocellulose raw material can be subjected to mechanical treatment. Examples of the mechanical treatment include any mechanical means such as cutting, cutting, crushing, and grinding. By the mechanical treatment, lignocellulose is easily saccharified in the chemical treatment step of the next step. The apparatus used in the mechanical treatment is not particularly limited, and for example, a cutting apparatus, a single-screw crusher, a twin-screw crusher, a hammer crusher, a refiner, a kneader, a ball mill, or the like can be used.

As a pre-process or post-process of the mechanical treatment, a foreign matter removing step by washing or the like for removing foreign matter (foreign matter other than lignocellulose such as stone, dust, metal, plastic) can be introduced.
Examples of the method for washing the raw material include a method of removing water from the foreign material mixed with the raw material by spraying water on the raw material, or a method of removing the foreign material by immersing the raw material in water and sedimenting the foreign material. Moreover, the method of isolate | separating a foreign material from a raw material using apparatuses, such as a metal trap, is mentioned.
If foreign materials are included in the raw materials, there is a possibility of causing damage to equipment parts used in mechanical processing such as refiner discs (plates), and causing problems in the manufacturing process such as clogging of piping. Therefore, it is desirable to introduce a foreign substance removing step.

<Chemical treatment>
Next, the mechanically treated lignocellulose raw material is then chemically treated. The chemical used in the chemical treatment is selected from one or more alkaline chemicals selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate and sodium hydrogen carbonate, or sodium sulfite and the above alkaline chemicals A pretreatment including a chemical treatment of immersing in a solution containing one or more alkaline chemicals. Further, chemical treatment with an oxidizing agent such as ozone or chlorine dioxide is also possible.
The chemical treatment is preferably performed as a post-treatment of the pretreatment in combination with the mechanical treatment.

  The amount of chemicals used in the chemical treatment can be arbitrarily adjusted according to the situation, but lignocellulose can be used to reduce the cost of chemicals and to prevent the yield from decreasing due to cellulose dissolution and over-decomposition. It is desirable that it is 70 mass parts or less with respect to 100 mass parts of absolutely dry of a system raw material. Although the immersion time and the processing temperature of the chemical | medical solution in chemical processing can be arbitrarily set with the raw material and chemical | medical agent to be used, processing time 20-120 minutes and processing temperature 80-230 degreeC are preferable. By tightening the processing conditions, elution or excessive decomposition of cellulose in the raw material may occur, so that the processing time is preferably 90 minutes or less and the processing temperature is preferably 200 ° C. or less.

As the chemical treatment, 10 to 70% by mass of sodium sulfite and 0.1 to 20% by mass of alkali as a pH adjuster can be added to the lignocellulose raw material (dry weight). When sodium sulfite is added alone to the lignocellulose in the above-mentioned addition amount and heat-treated, an organic acid such as acetic acid is generated during hydrolysis, so that the pH is lowered and the hydrolyzed solution becomes acidic. When hydrolysis is continued under acidic conditions, the problem arises that xylose produced by hydrolysis is converted to furfural. Since furfural is an inhibitor of ethanol fermentation, it is desirable not to produce it as much as possible. Moreover, since the yield of xylose which is a fermentation substrate falls, ethanol production efficiency falls as a result. By adding sodium sulfite and alkali as a pH adjuster to the lignocellulose raw material in the above-mentioned amount and heat-treating, the pH during hydrolysis is maintained from neutral to weakly alkaline. Yield reduction can be suppressed.

  Examples of the alkali used as the pH adjuster include sodium hydroxide, potassium hydroxide, sodium carbonate and the like, but are not particularly limited to these chemicals.

When the heat treatment is performed by adding 10 to 70% by mass of sodium sulfite and 0.1 to 20% by mass of alkali as a pH adjuster with respect to the lignocellulose raw material (dry weight), the heat treatment temperature is 80 -200 degreeC is preferable and 120-180 degreeC is more preferable. Moreover, although heat processing time can be performed in 10 to 300 minutes, 30 to 120 minutes are preferable. By tightening the processing conditions, elution or excessive decomposition of cellulose in the raw material may occur, so that the processing temperature is preferably 180 ° C. or lower and the processing time is 120 minutes or shorter.

(Grinding treatment)
In the present invention, it is desirable to grind the lignocellulose raw material obtained by the chemical treatment. Examples of the grinding device used in the grinding treatment include a refiner and a ball mill. When a refiner is used, the refiner disk (plate) clearance is preferably ground within a range of 0.1 to 2.0 mm, and more preferably within a range of 0.1 to 1.0 mm. As a refiner to be used, a single disk refiner, a double disk refiner, or the like can be used, and any refiner that can set the clearance of the opposing disk within a range of 0.1 to 2.0 mm can be used without particular limitation. it can. If the disc clearance exceeds 2.0 mm, the sugar yield obtained by saccharification or concurrent saccharification and fermentation is added, which is not preferable. On the other hand, if the disc clearance is lower than 0.1 mm, the yield of the hydrolyzate (solid content) after grinding with a refiner is not preferable. Also, if the disc clearance is lower than 0.1 mm, the electricity consumption required for the operation of the refiner increases, which is not preferable.

The material of the refiner disk (plate), the disk mold, the disk surface blade mold, the direction of the blade with respect to the disk surface, etc. should be used without any limitation as long as the material and shape are effective. Can do.

  The lignocellulosic raw material subjected to the above-mentioned grinding treatment can be solid-liquid separated into an aqueous solution and a solid content, and the solid content can be used as a raw material for saccharification or concurrent saccharification and fermentation. As a method for solid-liquid separation, for example, an apparatus that can be separated into an aqueous solution and a solid content using a screw press or the like and can be used without limitation as long as it can be separated into an aqueous solution and a solid content.

It is preferable to perform sterilization treatment before saccharification or parallel saccharification fermentation using the raw material after the solid separation. When miscellaneous bacteria are mixed in the lignocellulosic biomass raw material, there is a problem that the miscellaneous bacteria consume sugar when the enzyme is saccharified and the yield of the product decreases.
The sterilization treatment 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 treatment is performed 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.

  The lignocellulose raw material subjected to the pretreatment is supplied to the saccharification step or the primary concurrent saccharification and fermentation step.

<Saccharification process>
The lignocellulosic raw material that has been subjected to pretreatment suitable for the enzymatic saccharification reaction is mixed with an appropriate amount of water and an enzyme to form a raw material suspension, which is supplied to the saccharification step. Lignocellulose-based raw materials are saccharified (cellulose → glucose, hemicellulose → glucose, xylose) by enzymes (cellulase, hemicellulase).

<Concurrent saccharification and fermentation process>
The lignocellulosic raw material that has been pretreated suitable for the enzymatic saccharification reaction is mixed with an appropriate amount of water and enzyme to form a raw material suspension, and further mixed with microorganisms such as yeast and supplied to the parallel saccharification and fermentation process. The The lignocellulosic material is saccharified by an enzyme, and the produced saccharide is fermented to ethanol by a fermentation microorganism (such as yeast).

It is preferable that the suspension concentration of the lignocellulosic material used in the saccharification process or the concurrent saccharification and fermentation process is 1 to 30% by mass. If it is less than 1% by mass, there is a problem in that the concentration of the product is ultimately too low and the cost for concentrating the product becomes high. Moreover, as the concentration exceeds 30% by mass, it becomes difficult to stir the raw materials, resulting in a problem that productivity is lowered.

Cellulolytic enzymes used in the saccharification step or the concurrent saccharification and fermentation are enzymes collectively called cellulases having cellobiohydrolase activity, endoglucanase activity, and betaglucosidase activity.
Each cellulolytic enzyme may be added with an appropriate amount of an enzyme having the respective activity. However, commercially available cellulase preparations have the above-mentioned various cellulase activities and also have hemicellulase activity. Since many products are available, a commercially available cellulase preparation may be used.

Commercial cellulase preparations include the genus Trichoderma, the genus Acremonium, the genus Aspergillus, the genus Phanerochaete, the genus Trametes, the genus Humicola, and the like. There are cellulase formulations derived from 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) ), GC220 (manufactured by Genencor).
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 pH of the reaction solution in the saccharification step or the concurrent saccharification and fermentation step is preferably maintained in the range of 3.5 to 10.0, more preferably in the range of 4.0 to 7.5.

  The temperature of the reaction solution in the saccharification step or the concurrent saccharification and fermentation step is not particularly limited as long as it is within the optimum temperature range of the enzyme, preferably 25 to 50 ° C, and more preferably 30 to 40 ° C. The reaction is preferably continuous, but may be semi-batch or batch. The reaction time varies depending on the enzyme concentration, but in the case of a batch system, 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.

<Fermentation process>
When performing a saccharification process and a fermentation process with another reaction tank, the process liquid after the said saccharification process is transferred to a fermentation process, and fermentation is performed using a fermentation microorganism.

In the fermentation process or the concurrent saccharification and fermentation process, fermented microorganisms that can ferment sugars (hexose sugar, pentose sugar) are used. Examples of fermenting microorganisms include Saccharomyces cerevisiae, Pichia stipais, and Candida shihatae sapiens. -Bacteria such as mobilis (Zymomonas mobilis). In addition, genetically modified microorganisms (yeast, bacteria, etc.) produced using genetic recombination techniques can also be used. As the genetically modified microorganism, a microorganism capable of simultaneously fermenting hexose and pentose can be used without particular limitation.

  Microorganisms may be immobilized. Immobilizing microorganisms can eliminate the step of separating and re-recovering microorganisms in the next step, so that at least the burden required for the recovery step can be reduced, and the loss of microorganisms can be reduced. . Moreover, the collection of microorganisms can be facilitated by selecting microorganisms having aggregating properties.

<Solid-liquid separation process>
The culture solution discharged from the parallel saccharification and fermentation process or the fermentation process is transferred to a solid-liquid separator and separated into a liquid component (filtrate) and a solid component (residue). As an apparatus for performing solid-liquid separation, a screw press, a screen, a filter press, a belt press, a rotary press, or the like can be used. As the screen, a vibrating screen to which a vibrating device is added can be used. The mesh size used in the solid-liquid separation is preferably 1.25 to 600 mesh, more preferably 60 to 600 mesh.

The liquid component (filtrate) separated in the solid-liquid separation process is transferred to the ethanol distillation process.

<Ethanol distillation process>
The culture solution discharged from the concurrent saccharification and fermentation process or the fermentation process can be subjected to distillation separation of a fermentation product (ethanol or the like) by an ethanol separation apparatus such as a vacuum distillation apparatus in the distillation process. 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 and deactivated, and the amount of newly added enzyme increases, resulting in poor economic efficiency.
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 distillation residue after separation of the fermentation product (such as ethanol) after distillation can be separated into a residue and a liquid by a solid-liquid separator. The separated residue contains enzymes, lignin, and fermenting microorganisms. The enzyme adsorbed on the residue can be released and recovered and reused. Lignin can be recovered as a combustion raw material and used as energy, or lignin can be recovered and used effectively. Fermentation microorganisms (such as yeast) can be separated from the residue and reused in the saccharification or concurrent saccharification and fermentation process.

[CIP cleaning process]
In the present invention, before the ethanol production facility is operated, the ethanol production facility (saccharification and fermentation tank, piping connected to the saccharification and fermentation tank, piping connected to the concentrating tower) is sterilized with an alkaline aqueous solution (hereinafter referred to as “CIP” cleaning). I do. Examples of the alkali used for “CIP” washing include sodium hydroxide and potassium hydroxide. A chemical for enhancing the bactericidal effect can be added to the alkali.
By performing the “CIP” cleaning, it is possible to suppress the contamination of germs occurring in the ethanol production facility, and the ethanol productivity can be maintained at a high level.

  The alkali concentration of the alkaline aqueous solution used in the “CIP cleaning step” is preferably 1 to 10% by mass, more preferably 2 to 8% by mass, and particularly preferably 3 to 7% by mass. On the other hand, if it exceeds 10% by mass, the effect of suppressing germs reaches its peak and the cost increases.

The time for contacting the ethanol production facility with the alkaline aqueous solution may be 1 minute or longer, preferably 5 minutes or longer, and more preferably 10 minutes or longer. The temperature of the alkaline aqueous solution is not particularly limited, but is preferably 35 to 85 ° C. because the effect of suppressing various germs increases. In addition, it is preferable to repeatedly circulate the alkaline aqueous solution in the ethanol production process because the effect of suppressing various germs increases.

EXAMPLES Next, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited by these Examples.

[Example 1]
[CIP cleaning process]
At the ethanol production facility (Kure Factory), the ethanol production facility was continuously operated for 14 days by the method described in [Pretreatment] to [Residue Separation] to perform ethanol production (first operation). The operation was stopped on the 14th day after the operation was started. 4 mass% sodium hydroxide for sterilization of saccharification and fermentation equipment (saccharification and fermentation tank, piping connected to saccharification and fermentation tank, piping connected to concentrating tower) of ethanol production process according to CIP work procedure manual of ethanol production equipment (Kure factory) Performed with aqueous solution. After the CIP cleaning, ethanol production was continuously performed again for 14 days by the method described in [Pretreatment] to [Residue separation] below (second operation).

[Pretreatment process]
A single-shaft crusher (SC-15, manufactured by Saiho Kiko Co., Ltd.) with a 20 mm round hole screen made of chip-like eucalyptus globula woodland residue (70% bark, 30% branches and leaves, hereinafter referred to as “raw material”). It was put into a hopper and crushed. Air was sprayed uniformly and continuously onto the rotor at a flow rate of 500 ml per minute for 1 kg of raw material (dry weight) at the bottom of the crushing rotor. The power consumption (kWh / t: dry weight) required for the operation of the uniaxial crusher was measured using a power integrator.

[Chemical treatment process]
After adding 200 g of 97% sodium sulfite and 10 g of sodium hydroxide to 1 kg (absolute dry weight) of the raw material, water was added to adjust the volume of the aqueous solution to 8 L. The raw material suspension was mixed and then heated at 120 ° C. for 1 hour. The raw material suspension after the heat treatment was crushed with a refiner (manufactured by Kumagai Riki Kogyo Co., Ltd., KRK high concentration disc refiner) with the disc (plate) clearance set to 1.0 mm. Next, the raw material suspension after the grinding treatment was subjected to solid-liquid separation (dehydration) using a 60 mesh (250 μm) screen, and washed with water until the electric conductivity of the solution reached 30 μS / cm. The saccharification treatment was performed using the solid content after solid-liquid separation as a raw material.

[Concurrent saccharification and fermentation process]
Saccharomyces cerevisiae (commercially available yeast, trade name: trade name: Maurivin: Mauri) as yeast in a liquid medium (glucose 30 g / L, polypeptone 5 g / L, yeast extract 3 g / L, malt extract 3 g / L, pH 5.6) in advance. Yeast Australia Pty Limited) was cultured at 30 ° C. for 24 hours.
1 was added to the saccharification and fermentation tank BR1 shown in FIG. 1 so that the polypeptone was 5 g / L, the yeast extract was 3 g / L, and the malt extract was 3 g / L, and water was added to adjust the final volume to 0.8 m ³ . A culture solution containing yeast cells was added to the saccharification and fermentation tank BR1 and cultured for 24 hours. When the density of yeast grew to 1 × 10 ⁸ / ml, 50 L of a commercially available cellulase solution (Multifect CX10L, Genencor) and 100 kg (dry weight) of raw material were added to the saccharification and fermentation tank BR1. Next, water was added to the saccharification and fermentation tank BR1 to adjust the final volume of the culture solution to 1 m ³ . The pH of the culture solution was adjusted to 5.0, and primary parallel saccharification and fermentation was started at 30 ° C. Saccharification and fermentation were carried out by setting the retention time of the culture solution in the saccharification and fermentation tank BR1 (time for the raw material suspension to pass through the saccharification and fermentation tank BR1: capacity / flow rate of the saccharification and fermentation tank BR1) to 20 hours. That is, from the start of saccharification and fermentation, a raw material suspension (raw material suspended in water) having a solid content concentration (per dry weight) of 10% by mass at a flow rate of 50 L / h is a raw material supply port 1 of the saccharification and fermentation tank BR1 From continuously. On the other hand, the raw material suspension was discharged at 50 L / h from the culture liquid outlet 2 of the saccharification and fermentation tank BR1 simultaneously with the start of the raw material supply, and transferred to the solid-liquid separation process. The cellulase solution was continuously added to the culture tank BR1 at 2.5 L / h. When the culture solution decreased during continuous operation, the final volume of the culture solution was maintained at 1 m ³ by automatically adding a medium. The pH of the culture medium during the culture was maintained at 5.0.

[Solid-liquid separation process]
The raw material suspension discharged from the primary saccharification and fermentation step is subjected to solid-liquid separation using a solid-liquid separator S: screw press (SHX-200 x 1500 L, screen size 1.2 mm (14 mesh) manufactured by Togoku Industry Co., Ltd.). The solid (residue) and liquid (filtrate) were separated.

[Ethanol distillation process]
The liquid component separated by the solid-liquid separation is an aqueous solution containing ethanol at a distillation temperature of 40 ° C., a heating temperature of 80 ° C., and a supply liquid amount of 95 L / h using a vacuum distillation apparatus EV (Evapor PEP-1, Okawara Seisakusho). And concentrated.

[Residue separation step]
The concentrated liquid separated from the vacuum distillation apparatus EV is operated at a rotational speed of 4500 rpm and a differential speed of 5.0 rpm in a decanter centrifuge (IHI, HS-204L type), and the solid content (residue A) and liquid content (filtrate) Separated. The liquid was transferred to the saccharification and fermentation tank BR1 via line 7.

<Data measurement>
After 14 days (336 hours) from the start of the parallel saccharification and fermentation, the culture solution was collected from the outlet 2 of the parallel saccharification and fermentation tank BR1, and the cell density of ethanol, yeast, and general bacteria (miscellaneous bacteria) was measured. The ethanol concentration was measured with a glucose sensor (BF-400 manufactured by Oji Scientific Instruments).
The results are shown in Table 1.

[Comparative Example 1]
In Example 1, all tests were performed in the same manner as in Example 1 except that [CIP cleaning step] was omitted. The results are shown in Table 1.

Table 1

  As shown in Table 1, after performing the first ethanol production, before introducing the second ethanol production, the [CIP cleaning step] was introduced (Example 1) and not inserted (Comparative Example 1). ), The concentration of ethanol contained in the culture solution discharged from the culture tank was high.

According to the present invention, it is possible to suppress contamination of germs generated in an ethanol production facility, so that ethanol productivity can be maintained at a high level.

1: Raw material supply port 2: Parallel saccharification and fermentation tank discharge port 3: Solid content transfer line 4: Liquid content transfer line 5: Concentrated liquid transfer line after distillation 6: Residue discharge line 7: Liquid content circulation line BR1: Parallel saccharification and fermentation tank S: Solid-liquid separator EV: Vacuum distillation apparatus C: Residue separator

Claims (7)

In a method for producing ethanol from lignocellulosic raw materials,
A lignocellulosic system comprising a step of washing an ethanol production facility including a saccharification and fermentation tank with an alkaline aqueous solution, and a saccharification and fermentation step in which saccharification and fermentation is performed in the saccharification and fermentation tank and ethanol is produced after the washing step. A method for producing ethanol from raw materials. The method for producing ethanol from a lignocellulosic raw material according to claim 1, wherein the concentration of the alkaline aqueous solution is 1 to 10% by mass. The method for producing ethanol from a lignocellulosic raw material according to claim 1 or 2, wherein the alkaline aqueous solution is circulated in the ethanol production process. The method for producing ethanol from a lignocellulosic material according to any one of claims 1 to 3, wherein the time for contacting the ethanol production facility with an alkaline aqueous solution is 1 minute or more. The method for producing ethanol from a lignocellulosic raw material according to any one of claims 1 to 4, wherein the temperature of the alkaline aqueous solution is 35 to 85 ° C. The saccharification and fermentation step is performed according to any one of claims 1 to 5, wherein the lignocellulosic raw material is subjected to chemical treatment and grinding treatment, and the saccharification and fermentation step is performed using the solid content after solid-liquid separation of the ground suspension as a raw material. A method for producing ethanol from the lignocellulosic raw material described. The method for producing ethanol from a lignocellulosic raw material according to any one of claims 1 to 6, wherein the alkaline aqueous solution is an alkaline aqueous solution containing only sodium hydroxide or potassium hydroxide as an alkali.

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