KR20150006696A - Method for preparing bioethanol from lignocellulosic biomass - Google Patents

Abstract

The present invention relates to a method for producing bioethanol from wood-based biomass. According to the method, the biomass is extracted with hot water before pretreatment in order to remove extractable substances such as inorganic salts. Therefore, an impurity content of an enzymatic hydrolysis material can be minimized. Moreover, generation of over-decomposed sugar products is inhibited as much as possible by pretreating the biomass from which the extractable substance is removed by hot water under a condition maximizing the xylan yield. Subsequently, fermentable sugar can be produced at low costs by only concentrating a sugar solution, obtained by enzymatic saccharification of the pre-treated solid content obtained by a solid-liquid separation without washing the solid content with water, with a separation membrane. Therefore, bioethanol can be produced at a high yield.

Description

METHOD FOR PREPARING BIOETHANOL FROM LIGNOCELLULOSIC BIOMASS BACKGROUND OF THE INVENTION < RTI ID = 0.0 > [0001] <

The present invention relates to a method for producing bioethanol from woody biomass, and more particularly, to a method for producing bioethanol by obtaining a high concentration of fermentation sugar from woody biomass and fermenting it.

To cope with global exhaustion of fossil fuels and global warming caused by greenhouse gases, research and development have been conducted to produce transportation fuels and industrial chemicals from renewable biomass. Particularly, bioethanol, which is used as a biofuel, is produced by obtaining sugar from biomass and fermenting it.

Biomass that human beings can reproduce indefinitely as long as the sun is present include lignocellulosic biomass, which mainly includes terrestrial plants, and algal biomass, which mainly includes green algae that grow in water. Cellulose, which is one of the structural components of biomass, is the most abundant substance in the world, accounting for 20% to 50% of biomass, and is a polymer condensate of glucose, which is the main nutritional cause of fermentation bacteria. Much research and development has been concentrated on developing a technique for producing glucose in a large amount and in high purity from such cellulose.

However, in woody biomass, hemicellulose (about 15 to 35%) which is susceptible to hydrolysis and weakly hydrolyzed (about 15 to 35%) and lignin (about 10 to 30%), which is difficult to be reduced to monomers having a complex structure, ). In addition, woody biomass contains components that can be extracted with water, such as water-soluble starch, free sugars, proteins, lipids, pectin, tannins, various alkaloids, organic acids and various inorganic salts. (20% to 30%), and about 5 to 20% in the neck-type biomass (Michael E. Himmel (2009) Biomass recalcitrance, Blackwell Publishing; Run-Cang Sun (2010) Cereal Straw as a Resource for Sustainable Biomaterials Biofuels, Elsevier).

Among these extractable components contained in the woody biomass, starch or free sugars can be used for the preparation of fermentation sugars, but the other components do not only act as impurities in the fermentation sugar, It must be recovered or removed.

Korean Patent Laid-Open Publication No. 2011-0040367 discloses a device for continuously discharging a liquid material by injecting hot water into a reaction tank for a predetermined time and then using vapor pressure as a continuous fraction of biomass. Although the present invention attempts to fractionate the hot water extractable material by such a device, it is difficult to discharge the liquid material through the valve at high pressure, and even when the extraction and recovery are repeated several times due to the tunneling phenomenon in the contents at the time of discharge, %, Which is a technical problem that is difficult to be practically used to remove the extractable substance.

Inbicon, which uses woody biomass as a raw material to produce bioethanol, is a method of pretreating biomass by hydrothermal treatment followed by solid-liquid separation, removing liquid matter containing a large amount of microbial inhibitors, and then washing the pretreated solid with water (Jan Larsen et al., 2012, Biomass) to remove the extractable components in the biomass and Bioenergy , 46, 36-45). This method has the advantage of obtaining a clean pretreated solid content capable of producing a high quality fermentation sugar, but it can not avoid an increase in manufacturing cost due to solid-liquid separation and repeated washing. In addition, in order to prevent contamination by lactic acid bacteria in the enzymatic saccharification or alcohol fermentation, a process of adding a certain amount of a pretreatment liquid containing microorganism growth inhibiting substances is added, resulting in complicated composition due to high temperature and high pressure reaction, The extractable components of the biomass that has been lost must also be added back. In addition, the liquid material obtained as a byproduct after the pretreatment of the biomass includes xylose and xylan as well as over-segregated products of carbohydrates such as furfural and hydroxymethylfurfural (hereinafter referred to as 'HMF'), It is difficult to add value other than low-grade products such as fertilizer because it contains protein denatured products, various organic acids, lignin decomposition products and various inorganic salts produced by maillard reaction at a high temperature such as 190 占 폚.

When glucose is produced from woody biomass, cellulose is not easily converted into glucose only in a form in which biomass is pulverized. Therefore, pretreatment and saccharification processes are generally performed in sequence. Pre-treatment of biomass refers to a process of treating biomass by crushing or crushing with physicochemical method to make each structural component of biomass easy to fraction. The saccharification of biomass is a process in which cellulose is partially or completely dissolved or dissolved in hemicellulose or lignin surrounding the cellulose in the pretreatment process and converted into glucose by physicochemical or biochemical method It says.

When the enzyme is used as a means of hydrolyzing cellulose in the saccharification process, a technique widely used for the pretreatment of biomass includes autohydrolysis or hydrothermolysis, dilute acid pretreatment, lime pretreatment ), Ammonia pretreatment (such as ARP), and steam explosion. These pretreatment technologies make the cellulose react more easily to the hydrolytic enzymes through the pretreatment effect of dissolving mainly hemicellulose or lignin in the biomass. The pretreatment efficiency varies greatly depending on the type of biomass and reaction conditions, The kinds and amounts of substances other than sugars newly generated in the saccharification process are also greatly changed. Recently, among these technologies, a hydrothermal treatment technique, which is simple and economical, and is applicable to different types of biomass, is attracting more attention.

Enzymatic hydrolysis of the pretreatment refers to a process of converting cellulose into glucose by adding a cellulase to the pretreated cellulosic material which is converted into a form that is more easily reacted with the enzyme. In order to accelerate the hydrolysis, the cellulase used in this case further contains various enzymes such as hemicellulose hydrolyzate, starch hydrolyzing enzyme and pectin hydrolyzing enzyme in consideration of the pre-treatment technique previously applied.

The sugar content prepared by using the woody biomass as a raw material and subjected to the pretreatment and saccharification processes can be widely used for two purposes. First, a saccharide (hereinafter referred to as "saccharide") in which a glucose-based monosaccharide is dissolved but a hydrolysis residue (hereinafter referred to as "glycated residue") is intact, or a slight amount of glucose , There is a simultaneous saccharification and co-fermentation method in which a fermentation strain and an additive are directly added to a pretreated product and fermented. Currently, these methods are widely used for the study and the empirical manufacture of bioalcohols. Another method is to prepare the sugar solution by solid-liquid separation after the saccharification is completed and then use it as a fermentation sugar.

Physicochemical pretreatment of woody biomass and sugar saccharification by enzyme saccharification contain various substances in addition to monosaccharide including glucose in impurities. Representative impurities include furfural produced by overdosing of sugars and aldehydes such as HMF, organic acids such as levulinic acid and formic acid, and alcohols such as methanol. In addition, hydrolysis of hemicellulose And various phenol compounds produced by the decomposition of acetic acid and lignin produced at the time of hydrolysis. These impurities may act as inhibitors of microbial growth or metabolites depending on the type of fermentation bacteria. It has been reported that phenolic compounds, the degradation products of lignin contained in the sugar solution, are the most powerful microbial inhibitors, and that furfural and HMF can act as selective inhibitors depending on the concentration, and various acids such as acetic acid, Can vary. Furfural and HMF stimulated the growth of Clostridium beijerinckii in corn stalks using a sugar solution prepared by weak acid pretreatment with sulfuric acid and enzyme saccharification, syringaldehyde) inhibited its growth (Thaddeus Ezeji et al., Biotechnology and Bioengineering , 97 (6), 1460-1468, 2007). In a study in which each substance was added to an artificially prepared sugar solution at different concentrations and the growth was tested using yeast, the influence of the fermentation on the ethanol production was not significant but the effect of HMF was slightly affected. (Jeffrey D. Keating et al., 2006, Biotechnology and Bioengineering , 93 (6), 1196-1206). Phenolic compounds significantly inhibited the growth of yeast, and acetic acid and furfural were reported to have greater inhibitory potency compared to those used alone. In the case of Corynebacterium glutamicum as an ethanol fermentation strain, growth inhibition was inhibited as the concentration of furfural and HMF increased. The growth inhibition was inhibited by Zymomonas mobilis , E. coli ) (Shinsuke Sakai et al., Applied and Environmental Microbiology , 2349-2353, 2007). In addition, phenolic compounds such as syringesuladehyde significantly inhibited the growth of the strain, but the effect of acetic acid was not large. As described above, these microbial inhibitors, which may be contained in the solution based on woody biomass, may have different effects on the growth and production of metabolites depending on the type of microorganism, so it is not easy to determine the general tendency without direct application.

Therefore, in order to utilize the saccharide produced from the biomass as it is for the microbial fermentation, it is necessary to improve the fermentation microorganism so as not to be affected by various impurities or to produce metabolites efficiently, . Yeast, which is an alcoholic fermentation strain (ethanologen) that has been domesticated to produce various alcoholic beverages from humans for a long time, is one of the fermentation strains most resistant to microbial inhibitors. In recent years, Studies are being actively carried out to improve alcohol production. Lactic acid bacteria, which are common in everyday life, are also known to be relatively less affected.

On the other hand, most industrial microorganisms such as Escherichia coli and Clostridium acetobutylicum generally have a significant reduction in growth or metabolite production by some impurities. Therefore, in order to detoxify various microbial inhibitors contained in sugar solutions prepared from woody biomass, various studies such as excessive lime over-lime and lignin peroxidase-based polymerization Has been performed. A number of other researchers have applied various chromatographies using adsorption and partitioning for the removal of these materials (Villarreal, MLM et al., Enzyme and Micrbial Technology , 40, 17-24, 2006).

On the other hand, a method of washing the pretreated product before the glycation of the enzyme is also used in order to minimize the amount of the microbial inhibitor that the sugar solution may contain. Inbicon, which operates a pilot plant-scale bio-alcohol manufacturing plant, is a method of pretreatment of biomass by hydrothermal treatment followed by solid-liquid separation to remove liquid matter containing a large amount of microbial inhibitor and then washing the pretreated solid with water (Jan Larsen et al., 2012, Biomass and Bioenergy , 46, 36-45). However, some of the pretreatment liquids containing microorganism growth inhibitor may be added again in order to prevent contamination with unwanted microorganisms such as lactic acid bacteria at the early stage of enzyme saccharification or alcohol fermentation after washing the pretreatment product. As the enzymatic saccharification and ethanol fermentation proceeds, microorganism inhibitors such as acetic acid and phenolic compounds are released from the pretreatment. Therefore, this method is very useful for alcohol fermentation using a yeast resistant to microbial inhibitors. However, Examples used in the production of sugars have not been reported. In addition, in the case of the pretreated material having a smaller average particle diameter due to pulverization or pretreatment, some of the pretreated particles may be lost during the washing process, which may result in a lowering of the sugar yield.

Accordingly, it is an object of the present invention to provide a process for producing a fermentation microorganism capable of minimizing microbial inhibitors by using a series of pretreatment and enzymatic saccharification processes, And a method for producing bioethanol in a high yield.

In order to achieve the above object,

1) adding water to the woody biomass coarsely pulverized product or powder, heating the mixture at 50 to 140 ° C for 1 to 60 minutes and dehydrating (hot water extraction step);

2) adding water to the solid content obtained in step 1 and subjecting it to hydrothermal treatment at 170 to 210 ° C for 1 minute to 30 minutes (hydrothermal pretreatment step);

3) a step (solid-liquid separation step) of obtaining a solid fraction containing a small amount of liquid material by solid-liquid separation from the hydrothermal treatment product obtained in step 2;

4) enzyme saccharification (enzyme saccharification step) at 45 to 55 ° C by the cellulase complex enzyme in the solid content obtained in step 3;

5) recovering the sugar solution from the saccharide obtained in step 4 by repeating solid-liquid separation and extraction (sugar solution recovery step);

6) filtering, concentrating and removing impurities from the sugar solution obtained in step 5 to obtain a fermentation sugar (step of obtaining per fermentation); And

7) a step of fermenting the fermented sugar obtained in step 6 with an ethanol fermentation strain (alcohol fermentation step).

The method of the present invention can minimize the impurity content of the enzyme saccharification raw material by removing the extractable substance such as proteins and inorganic salts by extracting the biomass as hot water before the pretreatment and can reduce the amount of the biomass from which the hot water extractable substance is removed in the yield per hemicellulose The fermentation sugar for alcohol fermentation can be prepared by concentrating the pretreated solid obtained by the solid-liquid separation with water without washing with water. In addition, in the subsequent refining process, the amount of the impurity load is reduced, and the purification cost is reduced. In addition, since there is no cellulose loss due to washing of the pretreated enzyme before saccharification, high sugar yield can be maintained and, at the same time, And high-temperature enzymatic saccharification, it is possible to produce bioethanol without worrying about contamination with unwanted microorganisms such as lactic acid bacteria during the saccharification period of the enzyme. Further, the hot water extractable component contained in the raw material biomass and the relatively pure pretreatment liquid containing the xylooligosaccharide, which can be a raw material for the dietary fiber or xylitol, are respectively recovered and raw materials are used to maximize the utilization efficiency of the biomass .

As used herein, the term 'fermentable sugar' refers to sugar components that can be used for alcohol fermentation to produce bioethanol and the like, and is used interchangeably with fermentation sugars or fermentable sugars.

The method for producing bioethanol of the present invention comprises a series of processes including a step of removing a hot water extractable material of a biomass, a hydrothermal pretreatment step, a solid-liquid separation step, an enzyme saccharifying step, a sugar solution recovery step, a step of obtaining a fermentation sugar, Thereby minimizing the content of impurities such as microbial inhibitors and the like, thereby producing bioethanol with a high yield.

In the method of the present invention, the first step of removing the hot water extractable material is a step of adding water to the woody biomass coarsely pulverized material or powder and heating the material at 50 to 140 DEG C for 1 to 60 minutes, followed by dewatering. The above process can be used to minimize saccharification rate and sugar yield by minimizing the amount of substances capable of inhibiting the activity of cellulose hydrolytic enzymes such as inorganic salts, which are abundantly contained in herbaceous biomass, ), And at the same time, it is effective in reducing the process cost by reducing the loading of the impurities in the purification process of the sugar solution after the enzymatic saccharification. In addition, this process recovers useful materials such as starch, free sugar, protein, lipid, pectin, tannin, alkaloids that can exhibit various physiological activities, organic acids and inorganic salts contained in the biomass as an extractable material, During the pretreatment process, these substances become unusable due to reactions such as decomposition, condensation, and deformation, or they reduce the possibility of the protein becoming toxic by maillard reaction.

The process may be performed by immersing the biomass in water and then extracting the extractable component with water at a temperature at which the water solubility of the substance is maximized. Preferably, the biomass is immersed in water and stirred at a temperature of 80 to 105 ° C. for 1 to 60 minutes to remove the aqueous solution through solid-liquid separation before the extraction of the extractable material becomes maximum. In this process, most of the extractable components contained in the biomass can be removed, which include counter-current extraction, co-current extraction, semi-batch type extraction ) And batch type extraction may be used.

The objective of this process is to extract and remove as much of the extractable material as possible from the biomass with minimal hot water. In the case of batch extraction, the biomass pulverized material is put into an extractor, extracted with hot water, and then subjected to solid-liquid separation to remove the liquid material. In this case, the removal efficiency of the extractable material is determined by a ratio And the ratio of water) increases. For example, when 1 kg of biomass is put into 20 L of water and heated to 95 캜 and subjected to solid-liquid separation, when 3 kg of solid matter and 18 L of aqueous solution are obtained, 90% of the extractable component is removed and only the remaining 10% We enter the process. However, when the extract is to be used in terms of the biomass fraction, it is preferable that the liquid ratio should not exceed 1:20 in consideration of the dehydration cost and the water treatment cost.

The removal efficiency of extractable material by hot water extraction of biomass increases with temperature at extraction and at higher temperature at solid - liquid separation. This is because most materials increase in water solubility in proportion to temperature. Therefore, the extraction and solid-liquid separation are preferably carried out at a high temperature such as 50 to 140 캜, preferably 80 to 105 캜. Also, the higher the particle size of the biomass, the shorter the immersion time. However, considering the energy cost and the efficiency of the countercurrent extraction at the time of pulverization, the size of biomass can be used as raw material for pretreatment of biomass, for example, It is advantageous to crush or crush first.

The moisture content of the extractable material after extraction is dependent on the manner of use and the equipment to which it is applied, but is preferably about 50% to 90%. A continuous centrifugal separator, a filter press, a drum filter or a screw press may be used in order to obtain the dewatered solid as much as possible in the solid-liquid separation after the extraction process, if necessary.

In the method of the present invention, the hydrothermal pretreatment step of the biomass, which is the second step, is intended to maximize the yield of sugar while minimizing the production of microbial inhibitors. When all pretreatments obtained as a result of hydrothermal treatment are enzymatically saccharified, Water treatment is performed by adding water under the condition that the yield per hemicellulose is maximized. This process can be achieved by adding water to the solid content obtained in step 1 and pretreating it at 170 to 210 DEG C for 1 minute to 30 minutes. The hydrothermal treatment may be carried out by batch type or continuous pretreatment. The amount of moisture added to the raw material in the hydrothermal pretreatment, that is, the liquid-liquid ratio, is not particularly limited as long as it is more than an amount suitable for carrying out the hydrolysis reaction of the biomass. However, since the reaction product is not washed separately after the pretreatment, It is preferable that the weight ratio of raw material to water is in the range of 1: 3 to 1:15 in consideration of carrying over to the subsequent step of the microbial growth inhibiting substance. For example, in case of batch hydrothermal treatment of herbaceous biomass for general purpose fermentation, water, or water and clay mineral are added to the recovered solid matter from the sunflower stem powder through the above step 1 to obtain a solid content ratio of 8% The mixture is then placed in a high-pressure reactor and allowed to react for 5 minutes at 190 ° C (see Korean Patent Publication No. 2012-73087 and International Publication No. WO / 2012/087068). At this temperature, the yield of xylose and xylan produced by the hydrolysis of hemicellulose is maximized, while the amount of HMF produced by the overprecipitation of the perfluorinated and cellulose is minimal. On the other hand, the yield of glucose, which can be produced in the enzymatic saccharification after the pretreatment, is lower than that in the case of pretreatment under the more severe condition. Therefore, in order to increase the sugar yield, clay minerals upon enzymatic saccharification (Korean Laid-Open Publication No. 7-73087 and International Patent Publication WO / 2012/087068) or polyethylene glycol (US Patent No. 7,972,826).

In the method of the present invention, the solid-liquid separation step, which is the third step, is a step of obtaining a solid fraction containing a small amount of liquid matter by solid-liquid separation from the hydrothermal treatment product obtained in step 2. The solid-liquid separation process may be carried out according to any solid-liquid separation process commonly used in the art, and examples thereof include centrifugal separation, suction filtration, and pressure filtration. The pretreatment solids obtained by the solid-liquid separation may contain about 2 to 4 times of the pre-treatment liquid weight. In the method for producing bioethanol of the present invention, as in many research papers, the pre- And is added to the saccharification process by a complex enzyme. It is preferable that the pretreatment liquid material contained in the solid content after solid-liquid separation is adjusted so as to contain 5% to 30% of the liquid material contained in the pretreatment material immediately after the pretreatment. The liquid material contains a microorganism growth inhibiting substance in an appropriate amount to inhibit the growth of microorganisms that can often be contaminated from the air such as lactic acid bacteria at an optimum operating temperature of the cellulose hydrolytic enzyme of about 50 ° C, The pretreatment can be saccharified for more than 72 hours. In addition, the above-mentioned liquid material enables the enzyme solution to be recovered or removed after enzymatic digestion, and the concentration of the sugar solution can be maintained at 50 ° C or higher in the concentration process using a separation membrane, thereby suppressing microbial contamination.

The pretreated liquid material recovered by the solid-liquid separation contains a small amount of xylose produced by hydrolysis of hemicellulose, a large amount of xylooligosaccharide, acetic acid, a trace amount of furfural and a water soluble lignin degradation product, Most of the impurities are removed by step 1 and can be used as an excellent raw material for reprocessing into xylitol or dietary fiber.

In the method of the present invention, the fourth step, the saccharification step, is an enzymatic saccharification of the solid obtained in step 3 at an acidity of 45 to 55 DEG C and a pH of 4.8 to 5.2. This process converts cellulose and hemicellulose contained in the pretreated biomass into monosaccharides such as glucose and xylose.

In the above step, water may be further added to the solid content obtained in step 3 when the cellulase complex enzyme is added and saccharified, but it is preferable to limit the amount of saccharide solution to obtain a high concentration sugar solution after saccharification. Therefore, the ratio of water to solid content at the time of saccharification of the enzyme is preferably 1: 3 to 1:10 by weight in terms of the weight of the solid content before the pretreatment.

The enzyme pre-treatment of water is used, the saccharification enzyme is cellulase complex containing hemicellulase, and examples thereof include cellulose Cloud host (Celluclast ^®) 1.5L or Celluclast ^® conc BG and Novozyme ^TM 188 mixed formulation, a mixture of Cellic CTec2 and Cellic HTec2 or Cellic mixture with CTec3 and hemicellulase, cellular ribozyme (Celluzyme ^®), mixed formulations of the celebrity flow (Cereflo ^®) and ultra flow (Ultraflo ^®) (above Danish Novozymes product ), Asher reora claim (Acellerase ^TM), ramie Nex (Laminex ^®) and Spanish atom (Spezyme ^®) mixture (over Genencor Int, Ltd.), Loja cement (Rohament ^®; Rohm GmbH may be mentioned the product), etc.. Since the hydrothermal pretreatment contains a small amount of hemicellulose, a hemicellulase may be added to promote the hydrolysis rate, and the mixing ratio of the cellulase and the hemicellulase is preferably about 9: 1 to 10: 0. Further, the amount of the cellulase-based enzyme used per 1 g of biomass drying is preferably 0.001 g to 0.5 g.

Enzymatic saccharification is preferably maintained under the conditions in which the hydrolytic enzyme exhibits the maximum activity, that is, in the case of a mixture of Cellic CTec2 and Cellic HTec2, at pH 4.8 to 5.2 and at a temperature of 50 ± 1 ° C. In the absence of microbial contamination, To 96 hours or more.

In the present invention, the pretreatment liquid material partially remaining in the solid content and entering the enzymatic saccharification process contains a substance capable of partially inhibiting the activity of the cellulose hydrolase such as xylose and xylooligosaccharide, . Therefore, in the present invention, the following two known methods may be used to increase the sugar yield in the enzyme hydrolysis of the pretreatment product. The first method is the addition of polyethylene glycol (PEG), which is known to enhance the activity of the cellulase hydrolases during enzymatic glycation (see U.S. Patent No. 7,972,826). This can improve the sugar yield by inhibiting the enzyme irreversibly adsorbing to the lignin on the surface of the pretreatment. However, PEG with a molecular weight of 30,000 or more is used so that it can be recovered by separation process after saccharification so as not to remain as an impurity in the production of fermentation sugar. Another method is to add a small amount of a specific clay mineral during hydrothermal treatment or enzymatic saccharification (see Korean Patent Publication No. 2012-73087 and International Patent Publication No. WO / 2012/087068). This method not only improves sugar yield without washing the pretreated solid with water, but also is advantageous for the production of a fermented sugar since the resulting sugar solution contains no additives.

In the method of the present invention, the fifth step of recovering the sugar solution is a step of recovering the sugar solution by repeating solid-liquid separation and extraction from the saccharide obtained in step 4. The recovery step may be a continuous centrifugal separation, a filter press, a batch centrifugal separation, a screw press, or the like. For example, in the batch recovery process, the saccharide is centrifuged to recover the supernatant, the saccharified residue is diluted in the same volume of water, and centrifuged to recover the saccharide solution 3 to 5 times to recover the saccharide- Can be recovered by 99% or more.

In the method of the present invention, the sixth step, obtaining the fermentation sugar, is a step of filtering, concentrating, and removing impurities from the sugar solution obtained in step 5 to obtain a fermentation sugar. The final sugar concentration of the sugar solution obtained in step 5 is diluted to a level of about 60 to 150 g / L, which is about 50% of the initial concentration. Through the concentration process, the sugar concentration can be increased to 30% or more. The concentration process may be performed using reverse osmosis, nanofiltration or the like, which is well known in the art. In addition, enzymes contained in the sugar solution may be recovered by ultrafiltration or by heating to denature the enzyme to remove the enzyme by solid-liquid separation technique.

In the present invention, the sugar solution prepared at a high concentration of 30% or more in terms of glucose concentration to prevent the microorganism from being deteriorated during the storage of the fermentation sugars is composed of a low concentration of acetic acid produced by hydrolysis of hemicellulose and an organic acid such as formic acid, And HMF, a phenolic compound produced by decomposition of lignin, and a small amount of inorganic salts derived from biomass. However, the concentrations of these impurities except sugars are very low, so that when the sugar solution is diluted to a concentration that can normally produce metabolites, it is possible to produce Escherichia coli and yeast, universal strains for the production of various chemicals and biofuels, Clostridium acetobutylicum and Clostridium beijerinckii , Lactococcus lactis and Lactobacillus sp . Which mainly produce lactic acid, which are used in the production of Lactobacillus sp . ), And Corynebacterium glutamicum ( Corynebacterium glutamicum ), which is mainly used for the production of amino acids, does not significantly affect the growth of many industrial microorganisms.

In the method of the present invention, the alcohol fermentation step of the seventh step is a step of fermenting the fermentation sugar obtained in step 6 using an ethanol fermentation strain. The fermentation step may be performed according to methods known in the art for producing ethanol from glucose. Examples of the ethanol fermentation strains include Saccharomyces cerevisiae , Escherichia coli , Clostridium beijerinckii , Clostridium acetobutylicum , and Zymomo Zymomonas mobilis , and the like, but are not limited thereto. In one embodiment of the present invention, step 7 is characterized in that yeast extract and peptone are added to the fermentation sugar obtained in step 6, and then saccharomyces cerevisiae is inoculated as an ethanol fermentation strain, ≪ / RTI > The culture may be carried out in a batch or continuous culture.

Examples of woody biomass that can be used as a raw material in the method for producing bioethanol of the present invention include herbaceous biomass and woody biomass. However, besides the woody biomass mentioned above, biomass containing cellulose as a major sugar source such as algae biomass including microalgae and algae can be used without limitation. Examples of herbaceous biomass include trunks of oil palm, frond, empty fruit bunch, sunflower stem, straw straw, straw straw, corn stalks, reeds, Examples of woody biomass include, but are not limited to, lily trees, willow trees, acacia, eucalyptus, spruce, and the like.

The method for producing bio-ethanol using the woody biomass of the present invention as a raw material is a simplest method in which biomass is fractionated to produce a high concentration sugar solution at a high yield, It is possible to maximize utilization efficiency of the biomass.

Hereinafter, the present invention will be described in more detail based on the following examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

Example 1: Preparation of fermentation sugars made of sunflower stem

The sunflower stem powder whose composition was known was weighed 360 g into the building and placed in a light wood bag. The light wood bag was heated in a 95 ° C. steamer containing 3,600 g of distilled water for 10 minutes. Then, the light gray bag was put into a centrifugal dehydrator and dehydrated. After dehydration, the light wood bag was put in a 95 ° C steamer containing 2,400 g of distilled water, and the water was fully absorbed and then recovered and dehydrated by a dehydrator. The contents of the light-gauge bag were divided into three equal parts and put in a jar of a Parr reactor (Parr Instrument Co., Ltd., USA) for 2 L, and the contents were weighed to 1,500 g each by adding distilled water. The reactor was heated and subjected to hydrothermal treatment at 190 ° C for 5 minutes. After the reaction was completed, the reactor bottle was immersed in running water, cooled rapidly, and the contents were transferred to a lightweight bag. The above process was repeated 5 times to pretreat a total of 720 g of biomass, and the whole was collected and put into a light wood bag and dehydrated by a dehydrator. The dehydrated pretreated solid was transferred to a fermenter of a fermenter (BioTron, Korea) and nonionic water was added to the total amount to 4 kg. Then, 72 g of diatomaceous earth powder (Lechem Co., Ltd., Pohang, Korea) was added and stirred. Subsequently, 64.8 mL of Cellic CTec2 and 7.2 mL of Cellic HTEC2 were added as a cellulose hydrolyzing enzyme, and the mixture was stirred at 150 rpm while maintaining the fermentation tank at 50 ± 1 ° C and pH 5.0 ± 0.1. Three days after the start of saccharification, saccharification was completed to prepare a stock solution of the sugar solution, and the amount of the saccharide was measured. Then, 1 mL of the sample was collected and used as a sample for composition analysis. The sugar contents in the fermentation tank were transferred to a light wood bag and dehydrated with a dehydrator to recover the sugar solution. The sugar solution recovered once was put in a beaker containing 800 mL of distilled water, absorbed water, and stored for 12 hours or more in a refrigerator, and dehydrated again to separate the sugar solution. This procedure was repeated two more times to collect the sugar solution, and then combined with the stock solution of the sugar solution. The sugar solution was heated at 121 ° C for 20 minutes to denature and precipitate the enzyme, then centrifuged and filtered to obtain a clear sugar solution. Thereafter, the sugar solution was added to a concentrator (self-manufactured) equipped with a reverse osmosis membrane module (RE1812-80, manufactured by Woongjin Co., Korea) and concentrated to prepare a sugar solution having a glucose concentration of 300 g / L or more Hereinafter referred to as "1 per fermentation").

The fermented sugar was analyzed by a BioRad Aminex HPX-87H column and a Waters HPLC equipped with a refractive index detector to calculate the concentration of glucose and other sugars and acetic acid, and the yield was calculated. The concentrations of furfural and HMF were measured, and the yield of the concentrated sugar solution was shown in Table 2, and the concentration of fermented sugar after concentration was shown in Table 3 below. In addition, a phenolic substance prepared from a sunflower stem pretreated product was used as a standard substance, fermented sugar was diluted 200-fold, and the absorbance at 320 nm was measured with a spectrophotometer (Beckmann, Germany) Are shown in Table 3. The contents of inorganic salts of high-concentration fermentation sugars were measured by Plasma-Atomic Emission Spectrometer (ICP-AES, Thermo Scientific, USA)

Comparative Example 1: A solution of sunflower stem raw material prepared by washing hydrothermal treatment

120 g of the sunflower stem powder used in Example 1 was weighed into a building and put into a bottle of Parr reactor (Parr Instrument Co. Ltd., USA) for 2 L and distilled water was added to give a weight of 1,500 g . The mixture was then subjected to hydrothermal treatment at 190 ° C for 5 minutes. After the reaction was completed, the reactor bottle was immersed in running water, cooled rapidly, and the contents were transferred to a lightweight bag. The above process was repeated 5 times to pretreat a total of 720 g of biomass, and the whole was collected and put into a light wood bag and dehydrated by a dehydrator. The dehydrated solid was immersed in 20 L of boiling water and dehydrated by a centrifugal dehydrator. The dehydrated pretreatment solids were transferred to a fermenter in a fermenter (BioTron, Korea) and nonionic water was added to make the total amount 4 kg. 72 g of diatomaceous earth powder was added and stirred. Then, the fermenter was sealed, placed in an autoclave, and sterilized at 121 DEG C for 60 minutes. 64.8 mL of Cellic CTec2 and 7.2 mL of Cellic HTec2 as cellulose hydrolyzate were dissolved in 430 mL of ultrapure water, filtered through a filter system (Corning product, USA) equipped with a 0.22 μm membrane filter, and then added to the fermenter in a clean bench. The fermenter was stirred at 150 rpm while maintaining the temperature at 50 1 C and a pH of 5.0 0.1. To investigate the occurrence of lactic acid bacteria, the saccharide was collected at intervals of 1 day with stirring for 3 days after the initiation of the hydrolysis of the enzyme, and the resultant was analyzed by Waters HPLC equipped with a BioRad Aminex HPX-87H column and a refractive index detector The yields of glucose and other sugars, lactic acid and acetic acid were calculated and the concentrations of the furfural and HMF were measured and are shown in Table 2 below. The sugar contents in the fermentation tank were transferred to a light wood bag and dehydrated with a dehydrator to recover the sugar solution. The sugar solution recovered once was put in a beaker containing 800 mL of distilled water, absorbed water, and stored for 12 hours or more in a refrigerator, and dehydrated again to separate the sugar solution. This operation was repeated two more times to collect the sugar solution and then combined with the stock solution of the sugar solution. The sugar solution was heated at 121 ° C for 20 minutes to denature and precipitate the enzyme, then centrifuged and filtered to obtain a clear sugar solution. The sugar solution was placed in a concentrator (self-made) equipped with a reverse osmosis membrane module and concentrated to prepare a fermentation sugar having a glucose concentration of 300 g / L or more (hereinafter referred to as "fermentation sugar 2").

The sugar solution was analyzed by HPLC to determine the concentration of each component including sugar. The results are shown in Table 3. The concentrations of phenolic substances and inorganic salts were measured in the same manner as in Example 1, and are shown in Table 3.

Comparative Example 2: Preparation of a fermentation sugar having sunflower stem as raw material without removing an extractable substance

120 g of the sunflower stem powder used in Example 1 was weighed into a building and put into a bottle of a 2 L reactor (Parr reactor: Parr Instrument Co. Ltd., USA) and distilled water was added to make the contents weight 1,500 g each. The mixture was then subjected to hydrothermal treatment at 190 ° C for 5 minutes. After the reaction was completed, the reactor bottle was immersed in running water, cooled rapidly, and the contents were transferred to a lightweight bag. The above process was repeated 5 times to pretreat a total of 720 g of biomass, and the whole was collected and put into a light wood bag and dehydrated by a dehydrator. The dehydrated pretreatment solids were transferred to a fermenter in a fermenter (BioTron, Korea) and nonionic water was added to make the total amount 4 kg. 72 g of diatomaceous earth powder was added and stirred. Subsequently, 64.8 mL of Cellic CTec2 and 7.2 mL of Cellic HTec2 were added as the cellulase hydrolyzing enzyme, and the mixture was stirred at 150 rpm while maintaining the fermentation tank at 50 ± 1 ° C. and pH 5.0 ± 0.1. After the initiation of enzyme hydrolysis, the mixture was stirred for 3 days to complete the saccharification, to prepare a stock solution of the sugar solution, and 1 ml of the sample was used for the compositional analysis. The supernatant solution was analyzed with a BioRad Aminex HPX-87H column and a Waters HPLC equipped with a refractive index detector to calculate yields of glucose and other sugars and acetic acid, and the concentrations of furfural and HMF were measured The results are shown in Table 2 below. The sugar contents in the fermentation tank were transferred to a light wood bag and dehydrated with a dehydrator to recover the sugar solution. The sugar solution recovered once was put in a beaker containing 800 mL of distilled water, absorbed water, and stored for 12 hours or more in a refrigerator, and dehydrated again to separate the sugar solution. This operation was repeated two more times to collect the sugar solution and then combined with the stock solution of the sugar solution. The sugar solution was heated at 121 ° C for 20 minutes to denature and precipitate the enzyme, then centrifuged and filtered to obtain a clear sugar solution. The sugar solution was added to a concentrator (self-made) equipped with a reverse osmosis membrane module and concentrated to prepare a fermentation sugar having a glucose concentration of 300 g / L or more (hereinafter referred to as "3 per fermented sugar").

The sugar solution was analyzed by HPLC to determine the concentration of each component including sugar. The results are shown in Table 3. The concentration of the phenolic substance and inorganic salt was measured in the same manner as in Example 1, and is shown in Table 3.

The fermentation process of Example 1, Comparative Example 1 and Comparative Example 2 was summarized as shown in Table 1 below.

Example 1 Comparative Example 1 Comparative Example 2 Removal of Extractable Substances in Biomass from Raw Materials Using Hot Water Extraction After heating at 95 ° C for 10 minutes, dehydration (total 2 times) - - Hydrothermal pretreatment Treatment at 190 占 폚 for 5 minutes Treatment at 190 占 폚 for 5 minutes Treatment at 190 占 폚 for 5 minutes Pretreatment treatment Elimination of liquid water by dehydration after cooling After cooling, the hot water washing Elimination of liquid water by dehydration after cooling Sterilization of pretreatment water - 60 minutes at 121 ° C - Enzymatic sterilization using filtration - 0.22 ㎛ membrane filtration - Enzymatic saccharification of solids 50 ± 1 ° C,
pH 5.0 ± 0.1, 150 rpm 50 ± 1 ° C,
pH 5.0 ± 0.1, 150 rpm 50 ± 1 ° C,
pH 5.0 ± 0.1, 150 rpm Enzyme removal After heating at 121 ° C for 20 minutes, After heating at 121 ° C for 20 minutes, After heating at 121 ° C for 20 minutes, concentration Reverse osmosis membrane module Reverse osmosis membrane module Reverse osmosis membrane module

Ingredients Yield (g / 100 g) and yield Example 1 Comparative Example 1 Comparative Example 2 glucose 29.6 26.3 30.3 Other party 8.5 6.9 9.8 Acetic acid 1.3 1.0 1.1 Lactic acid 0.0 0.1 0.0 HMF 0.01 0.00 0.02 Furfural 0.02 0.00 0.02

The sunflower stem used as biomass in this experiment is 35.1 g of glucose conversion of cellulose, 18.8 g of monosaccharide conversion value and 4.5 g of acetic acid of hemicellulose. As shown in Table 1, the sugar solution of Example 1 prepared by the method for producing bioethanol according to the present invention sustained enzyme saccharification without contamination of lactic acid bacteria until 72 hours, yielding a glucose yield of 29.6 g, There was also little production of over-seafood. In addition, a small amount of the liquid material containing the microbial inhibitory substance produced as a result of the pretreatment was added to the glycation of the enzyme by leaving it in the pretreatment solid content, so that the sugar yield could be increased by saccharification without contamination of the lactic acid bacteria without sterilization.

On the other hand, in Comparative Example 1 in which the enzymatic saccharification was started after washing the pretreated solid with hot water, lactic acid was generated from 24 hours after glycation, and the concentration was rapidly increased after 48 hours. Thus, the enzymatic saccharification was stopped after 48 hours. The reason why the glucose yield of Comparative Example 1 is significantly lower than that of the sugar solution of Example 1 of the present invention is that there is some reason for the shortening of the glycation time of the enzyme because some of the pretreatment products are lost to fine particles during the hot water washing process to be. Washing with hot water to remove sugars and lignin degradation products contained in the pretreatment product may be one method for increasing the purity of the sugar solution resulting from the enzymatic saccharification. However, in the enzymatic saccharification process, microorganisms such as lactic acid bacteria It is difficult to avoid contamination of the fermented sugar, which is a big obstacle to the industrial production of the fermented sugar.

In addition, the pretreatment of the biomass as it was and the solidification obtained by solid-liquid separation of the pretreated product was obtained by saccharification of the enzyme, and the sugar yield was the highest at 30.3 g. However, since the biomass was used without being extracted into hot water, Because the contained free sugar is contained in the sugar solution. However, such free sugars can easily be over-decomposed, so that production of HMF and furfural can not be avoided as shown in Table 2 above. These oversea products are impurities that must be removed in order to produce high-concentration fermentation sugars that can be applied to various microorganisms. Therefore, this may greatly increase the cost of the chromatography process during the subsequent separation and purification process.

Ingredients Composition of high concentration fermented sugar for experiment (%) 1 per fermentation 2 per fermentation 3 per fermentation glucose 30.0 30.1 30.5 Other party 8.7 7.2 9.1 Acetic acid 0.6 0.5 0.4 Lactic acid 0.0 0.1 0.0 HMF 0.03 0.01 0.02 Furfural 0.02 0.00 0.01 Phenolic material 0.72 0.31 0.58 Inorganic salts 0.31 0.16 0.82

Table 3 shows the composition of the fermented sugar prepared by hydrothermal pretreatment of the sunflower stem and the enzyme saccharification obtained by concentrating the sugar solution obtained using the membrane. When the glucose concentration was adjusted to about 30%, 1 of the fermentation starter of the present invention and 3 of the fermentation starter of Comparative Example 2 contained very small amounts of HMF and furfural. However, when the pretreated product was washed with hot water, 2 contains almost no such substances. The concentration of the phenolic substance showed no significant difference between 1 of fermentation of the present invention and 3 of fermentation of Comparative Example 2, indicating that this substance was produced as a result of the pretreatment. The pretreatment product of Comparative Example 1, which had been pretreated with hot water, contained a phenolic substance having a degree of fermentation of 2 degrees, which shows that the washing effect is limited since the phenolic substance is released into the sugar solution under the enzymatic saccharification process even after hot water washing.

The proper concentration of these impurities contained in the pretreatment acts together with the saccharification temperature of the enzyme at about 50 ° C to inhibit the generation of lactic acid bacteria. The pretreatment is washed with hot water to remove the HMF, the ferulic and the fermentation saccharide 2 is easily contaminated with lactic acid bacteria in the enzymatic saccharification process, so that it contains lactic acid after the enzymatic saccharification.

One of the most prominent features shown in Table 3 is the content of inorganic salts, which is 3 per fermentation, omitting the hot water extraction process, compared to 1 of the fermentation per 1 of the present invention in which 90% of the extractable material was removed by hot water extraction of the biomass It contains about 2.6 times or more inorganic salt. The concentration of inorganic salt is very high as compared with the concentration of inorganic salt added when cultivating industrial microorganisms, and it is presumed that the inorganic salt concentration can inhibit growth depending on the type of microorganism.

Comparative Example 3: Comparison with fermented sugar prepared by removing the extractable material by continuous fractionation method

The method of the present invention was compared with a method of removing an extractable material by continuous fractionation disclosed in Korean Patent Laid-Open Publication No. 2011-0040367.

As prior arts, in Example 2 and Test Example 1 of Korean Patent Laid-Open Publication No. 2011-0040367, there is disclosed a method of removing a hot water extractable substance by continuous fractionation, preparing a fermented sugar by hydrothermal treatment and enzyme saccharification, have. The yield of sugar per fermented sugar obtained from the prior art was 10.1 g of xylose and 28.2 g of glucose per 100 g of sunflower stem. This was the total sugar yield obtained by glycation of the pre-treatment liquid and solid obtained after pretreatment.

On the other hand, in Example 1 of the present invention, the sugar yield of the sugar solution obtained by pretreating the same biomass as that of the prior art and then subjecting the pretreated solid containing 30% or less of the liquid matter to enzyme saccharification was 8.5 g of xylose and 29.6 g. The yield of total xylose was calculated by adding 7.5 g of the xylose content obtained by saccharifying the liquid material obtained by centrifuging the xylose content from the pretreatment with an enzyme to obtain a total xylose yield of 16.0 g, It can be seen that it is far superior to the prior art in terms of the winning ratio. This is because the prior art hydrolyzes hemicellulose from the sunflower stem using a continuous fractionator and the recovery of the liquid product is incomplete when the resulting liquid product is recovered through the valve. That is, the following pretreatment involves a large amount of hemicellulose hydrolyzate and the xylose is over-cleaved at high temperature, resulting in the above results. In addition, since a large amount of fermented seafood is produced, fermented sugar is estimated to be added to the refined sugar.

Considering these results, it can be seen that the method using the continuous biomass fractionator of the prior art is not effective in completely recovering the liquid after the high temperature reaction. On the other hand, in the present invention, by using an active solid-liquid separation technique such as hot water extraction of biomass or centrifugation after pre-treatment, the fraction of biomass can be effectively obtained, so that a fermentation sugar can be produced by the most economical method.

Test Example 1: Fermentation strain test using the fermented sugar of the present invention as a nutrient source

Cultivation tests of the fermenting bacteria were carried out using fermenting sugars 1, 2 and 3 of Example 1 and Comparative Examples 1 and 2. First, 2 mL of LB, MRS and 2YTG medium were inoculated with E. coli XB, Lactobacillus paracasei 13169 And Clostridium bezeriin N8052 (pKBE4112ADH) were cultured to prepare seeds. Subsequently, media were prepared using P2, MR and LAB mediums 1, 2 and 3, respectively, of Example 1, Comparative Examples 1 and 2 instead of glucose. Specifically, P2 medium was prepared by adding 20 g / L of fermentation, 5 g / L of yeast extract, 1.5 times of vitamin, 1.5 times of inorganic salts and 1.5 times of buffer; MR medium contained 20 g / L of fermentation, 6.67 g / L of KH ₂ PO ₄ , ₄ g / L of (NH ₄ ) ₂ HPO ₄ , 0.8 g / L of citric acid and iron sulfate, calcium chloride, Molybdenum salts and boron salts were mixed with 5 ml / L of trace metal aqueous solution; LAB medium was prepared by adding 20 g / L of fermentation, 5 g / L of polypeptone, 5 g / L of yeast extract, 0.1 g / L of sodium chloride and 0.5 g / L of MgSO ₄ . Thereafter, each of the above-mentioned media was inoculated with 0.2% Lactobacillus paracasei 13169 was administered under aerobic conditions and with < RTI ID = 0.0 > Clostridium & N8052 (pKBE4112ADH), under anaerobic conditions And cultured at 37 ± 1 ° C. The growth of microorganisms was examined by measuring the optical density of the samples at intervals of 24, 48, 72 and 92 hours during the incubation. The test was performed with 2 repetitions each and the results were averaged. Each medium was prepared as glucose for the reagent, and a control was made. Then, a fermentation test was carried out in the same manner, and the results are shown in Tables 4 to 6.

Incubation time Escherichia coli XB Turbidity change of culture Glucose control 1 per fermentation 2 per fermentation 3 per fermentation 0 0.05 0.39 0.37 0.63 24 2.30 2.69 1.98 0.63 48 2.21 3.47 2.82 1.28 72 2.33 3.63 3.01 1.91 96 2.36 - 3.28 2.03

Incubation time Lactobacillus paracasei 13169 Turbidity change of culture Glucose control 1 per fermentation 2 per fermentation 3 per fermentation 0 0.20 0.46 0.55 0.48 24 2.23 5.87 6.54 6.35 48 2.54 6.88 7.50 6.86 72 2.70 7.09 7.86 6.57 96 2.80 - - 7.77

Incubation time Clostridium Bayegrinki Turbidity change of N8052 culture Control 1 per fermentation 2 per fermentation 3 per fermentation 0 0.03 0.26 0.27 0.53 24 1.30 0.45 0.31 0.54 48 2.38 2.84 0.34 1.29 72 3.50 3.03 0.34 2.87 96 3.31 - 0.34 3.13

As shown in Table 4, Escherichia coli XB showed excellent growth at 1 per fermentation than the control group prepared with glucose for the reagent. Escherichia coli XB grew better than the control in the low fermentation rate of 2 lactic acid but the fermentation yield was lower than 1 in fermentation.

On the other hand, as shown in Table 5, Lactobacillus paracasei 13169 was relatively well grown at all fermentation sugars and was most insensitive to impurities.

On the other hand, as shown in Table 6, N8052 showed almost no growth at 2 fermentation per lactic acid production, and almost equal growth at 1 fermentation per fermentation. In addition, the fermentation sugar 3 containing the most inorganic salt was slightly slower than the fermentation sugar 1 of the present invention.

Test Example 2: Preparation of bioethanol using the fermentation sugar of the present invention

Alcohol fermentation was carried out using fermenting sugars 1, 2 and 3 of Example 1 and Comparative Examples 1 and 2. First, Saccharomyce cerevisiae was cultured in 40 ml of YPD liquid medium (yeast extract 10 g / L, peptone 20 g / L and glucose 50 g / L) to prepare seeds.

Then, the control medium containing glucose as a nutrient source and the fermenting sugar 1, 2 and 3 medium were prepared as fermentation sugar as a nutrient source, respectively. Specifically, the control medium was prepared by adding 60 g / L of glucose, 10 g / L of yeast extract and 20 g / L of peptone, and 60 g / L per fermentation was added to 1, 2 and 3 medium per fermentation And the same conditions as those for the control medium were prepared. Thereafter, 7% of the seeds were inoculated into each of the above-mentioned media, and cultured at 30 +/- 1 DEG C under anaerobic conditions. Samples were collected at intervals of 6, 12, 24, 48 and 72 hours during culture and analyzed by Waters HPLC equipped with a BioRad Aminex HPX-87H column and a refractive index meter to measure the ethanol concentration. The results are averaged and shown in Table 7 after three runs of each of the above tests.

Incubation time
(time) Changes in Ethanol Yield of Ethanol Fermentation Culture Inoculum (g / L) Glucose control 1 per fermentation 2 per fermentation 3 per fermentation 0 0.10 0.31 0.23 0.40 6 2.83 1.76 1.96 1.75 12 27.8 20.5 23.7 19.5 24 28.3 31.2 30.7 31.5 48 28.1 30.8 30.6 31.5 72 28.4 30.3 30.2 30.9

As shown in Table 7 above, ethanol production was higher in all the fermentation sugars 1, 2 and 3 per fermentation than the control glucose solution. Especially, the ethanol production of 1, 2 and 3 per fermentation was higher after 24 hours of incubation, when the ethanol production was the highest in the control. As shown in Table 3, even if acetic acid is partially contained in the fermentation 1 of the present invention, it does not affect the production of ethanol as a strain or a fermentation product of the strain, and besides glucose derived from biomass, And it can be used as a carbon source of ethanol fermenting bacteria. Therefore, the fermentation sugar of the present invention is more suitable for ethanol fermentation than the reagent glucose.

Claims (11)

1) adding water to the woody biomass coarsely pulverized product or powder, heating it at 50 to 140 ° C for 1 to 60 minutes, and then dehydrating;
2) adding water to the solid content obtained in step 1 and subjecting it to hydrothermal treatment at 170 to 210 ° C for 1 minute to 30 minutes;
3) obtaining a solid fraction containing a small amount of liquid by solid-liquid separation from the hydrothermal treatment product obtained in step 2;
4) enzymatically saccharifying the solid fraction obtained in step 3 at 45 to 55 ° C with a cellulase complex enzyme;
5) recovering the sugar solution from the saccharide obtained in step 4 by repeating solid-liquid separation and extraction;
6) filtering the sugar solution obtained in step 5, concentrating and removing impurities to obtain a fermentation sugar; And
7) fermenting the fermentation sugar obtained in step 6 with an ethanol fermentation step
≪ / RTI > wherein the bioethanol is produced from woody biomass. The method according to claim 1,
Characterized in that the woody biomass coarse pulp or powder and water of step 1 is used in a weight ratio of 1: 4 to 1:20. The method according to claim 1,
Wherein step 1 is carried out at 80 to 105 < 0 > C. The method according to claim 1,
Wherein the temperature and the reaction time of the step 2 are such that the yield of the hemicellulose sugar is maximized when all pretreatments obtained from the step 2 are enzymatically saccharified. The method according to claim 1,
Characterized in that the solid-liquid separation in step (3) is carried out by centrifugal separation, suction filtration or pressure filtration. The method according to claim 1,
Characterized in that the solids obtained in step 3 comprises 5 to 30% by weight of the pre-treatment liquid of the total liquid product resulting from the pretreatment. The method according to claim 1,
Characterized in that it does not include a separate sterilization treatment step after step 3 above. The method according to claim 1,
Characterized in that the recovery of the sugar solution of step 5 is carried out by batch or continuous centrifugation, a filter press or a screw press. The method according to claim 1,
A method for producing bioethanol from wood-based biomass, characterized by applying a membrane separation technique including a reverse osmosis membrane to the sugar solution filtration, concentration, and removal of impurities in step 6 above. The method according to claim 1,
Wherein the fermentation sugar obtained in step 6 contains 30% or more of glucose. The method according to claim 1,
Wherein the ethanol fermentation strain of step 7 is selected from the group consisting of Saccharomyces cerevisiae , Escherichia coli , Clostridium beijerinckii , Clostridium acetobutylicum , A method for producing bioethanol from woody biomass, characterized in that it is selected from the group consisting of Zymomonas mobilis .