KR101476348B1 - Method for manufacturing of ligno cellulo bio ethanol - Google Patents

Abstract

The present invention relates to a method for producing ligno-cellulosic bio-ethanol. A waste liquid generated during a step of producing a carbonized pellet by semi-carbonizing a ligno-cellulosic biomass is collected and fermented using yeasts, so that bio-ethanol is produced. Accordingly, a sustainable and industrially usable producing technique can be provided.

Description

METHOD FOR MANUFACTURING OF LIGNO CELLULO BIO ETHANOL [0002]

The present invention relates generally to a wood-based bio-ethanol manufacturing technology, and more particularly, to a bio-ethanol production method for producing bio-ethanol by recovering a waste liquid produced during the production of carbonized pellets by semi-carbonizing a woody biomass, To a new method for producing wood-based bio-ethanol capable of providing usable manufacturing techniques.

Currently, most of the fuel ethanol is produced from hexoses such as corn starch and sugar cane syrup using yeast (Saccharomyces cerevisiae) (beer or wine fermented yeast). However, these sugars are a relatively expensive source of raw materials and have competitive value as food. Starch and sugars are only a fraction of total hydrocarbons in plants. The main types of plant hydrocarbons present in stems, leaves, shells, pods, hulls, etc. are structural cell walls, polymers, cellulose and hemicellulose. Thus, there is a need for a technique for producing ethanol from lignocellulose such as cellulose, hemicellulose, and lignin from plants or trees, rather than from corn or sugarcane.

Current methods of saccharifying woody hydrocarbons, i.e., lignocelluloses, include acid utilization and enzyme-assisted hydrolysis. Acid hydrolysis, however, usually requires heat and has several disadvantages including the use of energy, the generation of acidic wastes, and the generation of toxic compounds that interfere with subsequent microbial fermentation. Thus, enzyme hydrolysis is a preferred alternative.

However, since there is no microorganism decomposing lignocellulose in nature, for example, a patent document 10-0292079 entitled " Ethanol Production by a Combination Host "has heretofore been used as a microorganism for converting pyruvate to ethanol by using a gene transformation technique Is proposed. However, microorganisms such as xylose and arabinose, which are derived from hemicellulose, and which decompose from pentose to pyruvate are not known. In addition, many research groups have attempted to express xylose-utilizing genes from hexose degrading yeast, but they have not succeeded.

[references]

1. Bae, Hyeong-Jong, "Practical use of cellulose hydrolysis system for biomass conversion of biomass," Rural Development Administration report, 2011

2. Chung chang-ho, Cellulosic ethanol production, Korean J. Biotechnol. Bioeng. 23: 1-7 (2008)

3. Kim hee-young et al., Materials and balances of bioethanol production process by concentrated acid saccharification process from lignocellulosic biomass. Clean Technology, 17: 156-165 (2011)

4. Thiago Oliveria Rodrigues, Patrick Louis Albert Rousset, 2009, of torrefaction on energy properties of Eucalyptus grandis wood, Cerne, Kavras, v. 15, n. 4, pp. 446-452.

5. Korea Forest Service, 2009, The quality standard of wood pellet. No. 2009-2.

6. Margalit Y. Winery Technology & Operation. The Wine Appreciation Guild, San Francisco, CA, USA. pp. 1-12 (2003)

7. Miller GL. Use of dinitrosalicylic acid regent for determination of reducing sugar. Anal. Chem. 31: 426-428 (1959)

8. Son HS, Park BD, Ko BK, Lee CH. Quality characteristics of Takju produced by adding different amounts of water. Korean J. Food Sci. Technol. 43: 453-457 (2011)

9. Seo HB, Han JG, Choi WS, Lee OK, Lee SM, Choi SH, Lee HY, Jung KH. Bioethanol production from wood biomass hydrolysate with supercritical water treatment. Korean J. Biotechol. Bioeng. 23: 494-498 (2008)

10. Ha SJ, Kim SR, Kim HJ, Du J, H.D. Cate J, Jin YS. continuous co-fermentation of cellobiose and xylose by engineered saccharomyces cerevisiae. Bioresource technology. 149: 525-531 (2013)

The present invention has been made in order to solve the problems of the prior art described above and to provide various additional advantages. Specifically, the present invention relates to a process for producing a carbonized pellet The present invention aims to provide a novel woody bioethanol production method capable of providing a sustainable and commercially available production technology by collecting the waste liquid produced in the production of bioethanol.

The above object is achieved by a method for producing wood-based bio-ethanol provided according to the present invention.

According to an aspect of the present invention, there is provided a method for producing wood-based bio-ethanol, comprising collecting a waste liquid generated during the production of a carbonized pellet by subjecting a ligno cellulo biomass to a torrefaction process, , And fermentation using yeast at 25 to 32 ° C to produce bioethanol.

In one embodiment, the woody biomass is woody sawdust comprising cellulose, semicellulose, and lignin; The semi-carbonization is carried out by a process of applying heat at 220 to 280 ° C under oxygen depletion conditions; The main components of the carbonized pellets are cellulose and lignin; The waste liquid may contain a pentose component which is produced by decomposing hemicellulose by heat.

In another embodiment, the pentose contained in the waste solution may comprise xylose or arabinose.

In another embodiment, the yeast is selected from the group consisting of Pichia stipitis strain, Pachysolen tannophilus strain, Candida shehatae var. Insectosa strain, And may be at least one of the pentose degrading strains consisting of the Candida tropicalis strain.

In yet another embodiment, the yeast further comprises at least one of six saccharide degrading strains consisting of a Saccharomyces bayanus strain and a Saccharomyces cerevisiae strain .

The present invention having the above-mentioned constitution can provide sustainable and commercially available manufacturing technology by producing bioethanol by collecting waste liquid produced in the process of producing carbonized pellets by semi-carbonizing woody biomass And a novel woody bioethanol production method is realized.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart showing a method for producing woody bio-ethanol according to an embodiment of the present invention; FIG.
Figure 2 is a reference diagram illustrating the constituents of woody biomass.
Figure 3 is a flow chart illustrating intermediate products for the production of ethanol from mixed sugar of pentane and hexane.
4 is a graph showing changes in wood-based components according to semi-carbonation conditions.
FIG. 5 is a graph showing changes in sugar content according to fermentation period using six yeasts in a mixed model system of glucose and xylose.
FIG. 6 is a graph showing the change of reducing sugar according to fermentation period using six yeasts in a mixed model system of glucose and xylose.
FIG. 7 is a graph showing changes in sugar content according to fermentation period using six yeasts in a glucose model system. FIG.
FIG. 8 is a graph showing changes in reducing sugar according to fermentation period using six yeasts in a glucose model system. FIG.
9 is a graph showing changes in sugar content according to fermentation period using six yeasts in a xylose model system.
10 is a graph showing the change of reducing sugar according to fermentation period using six yeasts in a xylose model system.
11 is a graph showing changes in sugar content according to fermentation period using six yeasts in a waste liquid generated in a half-carbonization process.
FIG. 12 is a graph showing changes in reducing sugar according to fermentation period using six yeasts in a waste liquid generated in a half-carbonization process. FIG.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a flow chart showing a method 100 for producing woody bio-ethanol according to an embodiment of the present invention.

In the illustrated example, the woody bioethanol production method 100 is a method of producing a carbonized pellet 130 by using a ligno cellulo biomass 110 as a raw material and subjecting it to a torrefaction treatment 120 The waste liquid 140 produced in the manufacturing process is collected and fermented (150) to produce ethanol (160).

The semi-carbonization process 120 is a process in which woody biomass is carbonized by treating it at a high temperature of 220 to 280 ° C in an oxygen-deficient or oxygen-deficient environment. By this semi-carbonization process, the cellulose and lignin components in the woody biomass can be made of carbonized pellets 130 having high calorie and low absorption. In addition, the gas generated during the semi-carbonization process can be recycled as an energy source. The waste liquid 140 containing pentose is collected from the hemicellulose component decomposed in the semi-carbonization process 120 according to the present invention. This waste solution is a mixture of pentane and hexane. The bioethanol can be prepared (160) by inoculating a yeast strain capable of degrading pentose and hexose into the waste solution (140) and fermenting at about 30 ° C.

Fig. 2 is a reference diagram illustrating the constituents of woody biomass. Fig. The woody biomass may be selected from the group consisting of cellulose, hemicellulose, lignin, Cellulose is a linear polymer in which glucose is linked by a -1,4-bond. Hemicellulose is linked to glucose by a -1,4 or -1,6-bond. Xylose, which is an orthophosphate, Arabinose is a polymer in which xylenes and arabinan are polymerized, and lignin is a polymer of various aromatic compounds and is a t component that keeps the plant skeleton.

Table 1 below summarizes the characteristics of the constituents of woody biomass.

Constituent material characteristic Degree of polymerization cellulose
(cellulose) Glucose polymer, B-1,4 bonded to form a linear microfibril and linear structure again hydrogen bond crystal structure 300-15,000 Hemicellulose
(hemicellulose) xylose is the main component and also contains a small amount of arabinos, mannose, galactose, etc., branched structure 70-200 Lignin
(lignin) Coniferyl, coumaryl, polyphenolic materials with complex structure as a polymer of sinapyl alcohol -

Xylose, a major component of the resulting hemicellulose degradation, is pentose. Saccharomyces cerevisiae , which is generally used to produce bioethanol, has a problem that it produces ethanol by using hexose as an energy source, but does not decompose pentose.

Wood chips and wood pellets using woody biomass are carbon-neutral and relatively difficult to put into practical use. Recently, they are rapidly spreading in Europe, and since 2009, carbon pellets industry has improved the heat generation and hygroscopicity of wood pellets Which is rapidly replacing. In the case of carbonized pellets, a large number of mass-production plants are already in operation in Europe, and the pelletization rate is relatively fast. However, the energy recovery rate of hemicellulosic is low at 80% because of the low hemicellulose recovered in the semi-carbonization process. This is due to the fact that gas components in hemicellulose decomposition components are recovered and recycled in the process but liquid decomposition products containing ozone sugar such as xylose and arabinose are not recycled. Therefore, in order to accelerate the practical use rate of carbonized pellets, it is required to improve the energy yield and reduce the manufacturing cost by developing a technology for raising the energy recovery rate of the waste liquid waste.

The present invention implements a method for producing bio-ethanol from a semi-carbonized product containing a sugar component in association with a semi-carbonization process of a woody biomass. Accordingly, the present invention provides bio-ethanol production technology that can reduce the production cost by omitting the pre-treatment and saccharification processes in the existing wood-based bio-alcohol production technology and can increase the energy recovery rate of the semi-carbonization process.

Figure 3 is a flow chart illustrating intermediate products for the production of ethanol from pentoses and hexoses.

The waste liquid recovered in the semi-carbonization process consists mainly of degradation products of hemicellulose, and pentoses such as xylose and arabinose are mixed with hexoses such as glucose. They are each degraded to pyruvate by yeast strain, and pyruvate can be converted to ethanol via acetaldehyde. The present invention utilizes Pichia stiptis (Candida tropicalis) and Saccharomyces cerevisiae (Saccharomyces cerevisiae). These strains are yeasts which are capable of growing under the conditions of waste liquid collected after the production of carbonized pellets and have excellent fermentation ability.

The yeast provided by the present invention is as follows. Six-sugar fermentation can utilize at least one of six saccharide degrading strains consisting of Saccharomyces bacillus strain and Saccharomyces cerevisiae strain among the yeast strains . In the 5-valent fermentation, Pichia stipitis strain, Pachysolen tannophilus strain, Candida shehatae var. Insectosa strain, and Candida tropicallis strain, And at least one of the pentose degrading strains consisting of the Candida tropicalis strain may be used. In addition, the alcohol fermenting yeast may include yeast (6 kinds) used for manufacturing wine, beer, and makgeolli, and other yeasts isolated from natural products.

According to one embodiment, the recycled waste wood is fermented to produce ethanol by semi-carbonizing the plain wood sawdust.

The white wood sawdust used in this example was purchased from a water reclamation site in Hwasun Gun, Jeollanam-do and dried at 105 ° C for 4 hours and then pulverized to 30mesh or less. Elemental analysis was performed by injecting semi-carbonized sawdust (about 17 mg) into an automatic element analyzer (Vario MACRO / elementar). The composition ratio of C, H, N and S was analyzed. The sample was injected, and the average calorific value was measured after three high calorific values were measured. The moisture absorption rate was measured by using a mechanical oven (HB-502M) at 105 for 4 hours and then stored in a relative humidity of 75% (HB-105LP) : 2008).

In the semi-carbonization process, a stirrer (D-1692) was preheated and the temperature of the heat plate at the bottom was set to reach 300 ° C. Then sawdust was introduced and the temperature of the sawdust was set to a half- ° C, 280 ° C, 290 ° C) and then half-carbonized for 30 minutes. After the completion of the reaction, the vacuum was transferred to the storage tank using a transfer device and cooled to below 100 ° C. The gas produced during the reaction time was cooled by using a heat exchanger, and the collected odor was removed by primary collection and scrubbing using a scrubber. Non-condensable gas passed through the scrubber was incinerated by a heat source for drying. The nitrogen was not added during the reaction period, one dose of sawdust is 20kg, the water content of the emissions was 5%, the generated gas is 1.5m ³ / min.

A stirrer type roaster (JIS-E04) was used to obtain optimum pyrolysis conditions. When the temperature of the hot plate reached the set temperature, 2 kg of sawdust was introduced, and after the sample temperature reached the set temperature, The reaction time was fixed to 10 minutes. The change of the reaction temperature (sample temperature) was changed to 210 ℃, 220 ℃ and 230 ℃. The gas generated during pyrolysis was forcibly evacuated using a blower, and when it was allowed to stand in the air after pyrolysis, it was cooled in a closed container after pyrolysis in order to prevent ignition.

The reaction time was fixed to 30 minutes and the reaction temperature was changed to 260 ° C., 270 ° C., 280 ° C. and 290 ° C., and the pyrolysis was carried out to measure the amount of heat, ash, energy yield, In order to derive the optimal reaction time, the pyrolysis temperature was fixed at 260 ℃, which is the derived optimum reaction temperature, and the reaction time was 10, 20, 30, 40 minutes, and the optimum reaction time was derived by evaluating the calorific value, ash, energy yield, element composition change, and absorptivity (storage stability).

Hemicellulose and celluloses were assayed by Van Soest method to analyze changes in hemicellulose, cellulose and lignin, lignin was quantified by 72% sulfuric acid hydrolysis method (TAPPI method T222 om-88), Van Soest method Hemicellulose and cellulose were calculated using the following equations (1) and (2). The ash content analysis was carried out by the method described in the wood pellet quality standard.

Hemicellulose (%) = NDF (%) - ADF (%) (1)

Cellulose (%) = ADF (%) - Ligand (%) (2)

Four strains ( Pichia stipitis, Pachysolen tannophilus, Candida shehatae var. Insectosa, Candida tropicalis ) were purchased from KCTC. Two strains ( Saccharomyces bayanus EC-1118, Saccharomyces cerevisiae K1 -V1116) was further used. The seed culture was inoculated in YM (yeast extract 0.3%, malt extract 0.3%, peptone 0.5%, glucose 1%) medium and incubated in an incubator at 30 ° C for 48 hours.

A model system was constructed and tested for the ability to use glucose and xylose for each yeast. In the model system, yeast extract 1% and peptone 2% were added to 40 mL of distilled water, 3% of glucose and 3% of xylose were added, and the pH was adjusted to 5.5 with 1N NaOH. In addition, glucose consumption and xylose monosaccharide content of each strain were separately measured by adding glucose (3%) and xylose (3%). After seeding culture of 10% of the culture volume was inoculated, samples were collected at 0, 2, 4, 6, 10, and 14 days after incubation at 30 ℃.

After adding 1% yeast extract and 2% peptone to 40 mL of the recovered waste solution or hydrolyzate, the pH was adjusted to 5.5 with 1N NaOH. The seed culture corresponding to 10% of the culture volume was inoculated, and the sample was collected at 0, 2, 4, 6, 10, and 14 days after culturing in a 30 incubator.

After centrifugation (4, 4000 rpm, 10 min) using a centrifuge (Combi 514R, Hanil Science Industrial, Kangreung, Korea), the supernatant was taken and analyzed using a digital refractometer (PR-32, The total acidity was measured by titration with 0.1 N NaOH, and the amount of NaOH consumed was measured by using tartaric acid (%). The pH was measured with a pH meter (pH-250L, ISTEK, Seoul, Korea) ). Reducing sugar content was measured by colorimetric method using dinitrosalicylic acid (DNS). The culture supernatant was diluted 50-fold. Diluted solution (1 mL) was added with 3 mL of a DNS reagent, followed by reaction at 100 ° C for 5 minutes. The solution was immediately cooled to obtain a colorimetric solution using a spectrophotometer (UV-1601, Shimadzu, Kyoto, Japan) The absorbance was measured at 550 nm and the standard curve (y = 3.1107x-0.2845, r2 = 0.994) was generated using glucose. Alcohol content was measured by distillation method in which 100 mL of the sample was sieved by sieving the wine. The specific gravity of the distilled solution was measured by using a distillation scale (Scale: 0-10; 10-20, Deakwang Inc., Seoul, Korea) after adjusting the volume to 100 mL by adding tertiary distilled water. Alcohol content was expressed as% (v / v) concentration by calibration with 15 using a Gay-Lussac table.

Samples from the 2nd and 14th days of fermentation were collected and analyzed for ethanol content. Bioethanol content was analyzed by gas charmatography (HP6890, Agilent). The oven temperature was adjusted to 150 ° C and the injector and FID temperature were adjusted to 250 ° C. In this case, a flame inonization detector (FID) was used and INNOWax column (30 mm, 0.25 m, Agilent 19091N-113) was used. N ₂ was flowed with carrier gas at 50 mL / min.

Elemental analysis and calorific value analysis of sawdust material are shown in Table 2 below. The calorific value of the sawdust was 4883.58 kcal / kg, the ash content was 0.28% and the water content was 38.6%.

element N (%) C (%) S (%) H (%) Calorific value (Kcal / kg) sawdust 0.636 51.50 0.190 5.164 4883.58

The hemicellulose and cellulose changes of woody biomass before and after the semi-carbonization process are shown below in order to verify the bioethanol production potential of the hydrolyzate produced in the manufacturing process of carbonized pellets.

Hemicellulose decreased from 27.42% to 5.44% at 260 ℃ for 30 minutes, and decreased to 0.71% at 270 ℃ for 30 minutes. The cellulase was degraded more than 97% 270 ℃ and 4.52%, respectively. The content of lignin increased with the increase of reaction temperature. The contents of lignin increased up to 75.42% at 260 ℃ for 30 minutes and 79.18% at 270 ℃ for 17 hours. Heat value, ash, energy yield, element composition change, and absorptivity (storability) were evaluated and optimum conditions were determined at 260 ℃ for 30 minutes. The reducing sugar of 57 g / L in the waste solution of the treated group at 260 ° C for 30 minutes was analyzed to be fermented using yeast.

Temperature Hemicellulose
(%) Cellulose
(%) Lignin
(%) Ash
(%) unknown
(%) Gravimetric yield (%) CON 27.42 11.70 17.51 1.57 41.80 - 260 5.44 10.06 75.42 3.67 5.41 69.11 270 0.71 4.52 79.18 4.03 11.56 62.05

* The reaction time is 30 minutes after the sample temperature reaches the set temperature

Fig. 4 is a graph showing the change of the wood-based component according to the semi-carbonization condition. The fermentation was carried out at 30 ° C for 7 days using Candida tropicalis strain and Saccharomyces cerevisiae strain, which is a hexane-utilizing strain, and the results are shown in Table 4 below.

The pH of the hydrolyzate before fermentation was slightly lowered from 4.37 to 4.29 and 4.32 after fermentation, while the total acidity increased from 0.19% to 0.31% and 0.28%. Sugar content decreased from 6.4 to 4.8 and 5.4. Reducing sugar content decreased from 57g / L to 31g / L and 48g / L. 5 Candida tropicalis strains were higher than those of Saccharomyces cerevisiae yeast strains, and the yeast was found to be precipitated under the hydrolyzate, suggesting that yeast growth and fermentation Was found to occur well.

Before fermentation After fermentation Candida tropicalis Saccharomyces cerevisiae pH 4.37 4.29 4.32 Total acidity (%) 0.19 0.31 0.28 Soluble solids () 6.4 4.8 5.4 Reducing sugar (g / L) 57 31 48

A model system was constructed and tested to determine the ability of glucose and xylose for each yeast. The model system was prepared by adding 1% yeast extract and 2% peptone to 40 mL of distilled water, adding 3% glucose and 3% xylose, and adjusting the pH to 5.5 with 1N NaOH. The sugar content of the pre-fermentation model was 8.5, and the change during the fermentation process in the model system is shown in FIG. FIG. 5 is a graph showing changes in sugar content according to a fermentation period using six yeasts in a mixed model system of glucose and xylose.

Saccharomyces bayanus and Saccharomyces cerevisiae strains were used on the 2nd day of fermentation and Candida tropicalis strain on the 4th day of fermentation was less than 6.5. Pachysolen tannophilus strains and Candida shehatae strains were continuously consumed until 10th day of fermentation and showed a value of 6.7 on the 14th day of fermentation. The Pachysolen tannophilus strain and Candida shehatae strain consumed the sugar slowly, but the final sugar content did not show any significant difference until the 14th day of fermentation. On the other hand, Pichia stipitis showed a sugar change of less than 1 during the fermentation period.

Figure 6 shows the changes in reducing sugar during the fermentation process using six yeasts in the model system. FIG. 6 is a graph showing changes in reducing sugar according to fermentation period using six yeasts in a mixed model system of glucose and xylose. FIG.

On the 0th day of fermentation, the content of reducing sugar was 6.3%, and the content of reducing sugar of Candida tropicalis, Saccharomyces bayanus and Saccharomyces cerevisiae was 2.9-3.4% after 2 days of fermentation. After 14 days, The content of reducing sugar was 2.6-2.9%. The Pachysolen tannophilus and Candida shehatae strains showed relatively low fermentation rate, but on the 14th day of fermentation, the content of reducing sugar was 2.8%. Among 6 strains, Pichia stipitis showed the least change of reducing sugar during fermentation period, which is similar to that of.

A new model system was prepared by adding 3% of glucose and 3% of xylose to each individual glucose and xylose monosaccharide. 7 and 8 show changes in the reducing sugar and the reducing sugar in the model system containing only glucose. FIG. 7 is a graph showing changes in sugar content according to fermentation periods using six yeasts in a glucose model system, and FIG. 8 is a graph showing changes in reducing sugar according to fermentation periods using six yeasts in a glucose model system.

The initial sugar content of the initial model system showed 6 values. On the 4th day of fermentation , the values of Candida tropicalis, Saccharomyces bayanus and Saccharomyces cerevisiae were 4.3 and then the fermentation was completed. In the experimental group supplemented with Pachysolen tannophilus and Candida shehatae , glucose consumption was observed until the 8th day of fermentation, which is similar to the glucose consumption pattern in the model system in which glucose and xylose were simultaneously added. During the fermentation period, the content of reducing sugar was similar to that of. Five strains except Pichia stipitis had different fermentation rates, but it was concluded that fermentation can be performed using glucose at the concentration of 3% glucose.

The changes in the reducing sugar and in the model system in which only xylose was added as the only carbon source are shown in FIGS. 9 and 10. FIG. 9 is a graph showing the change of sugar content according to the fermentation period using six yeasts in the xylose model system, and FIG. 10 is a graph showing the change in reducing sugar according to the fermentation period using six yeasts in the xylose model system to be.

There was almost no change of reducing sugar in all experimental groups until the 4th day of fermentation. However, sugar consumption was observed at the 8th day after fermentation except Saccharomyces cerevisiae, Saccharomyces bayanus, and Pichia stipitis . Saccharomyces strains with good glucose utilization did not change sugar significantly because they did not consume xylose. In the bioethanol production using biomass, it is important to select strains that can utilize hemicellulose hydrolyzate cellobiose and monosaccharide xylose, so it is generally considered to be difficult to apply Saccharomyces strains used for manufacturing wine . On the other hand , all of the experimental groups added with Candida tropicalis, Pachysolen tannophilus and Candida shehatae showed less than 4.6 on the 8th day of fermentation and less than 0.6% of reducing sugar. In addition, the Pichia stipitis strain showed little change on the eighth day of fermentation, but the content of reducing sugar decreased to 1.8%. Unusual was the increase in the content of reducing sugar on the 12th day of fermentation, suggesting that the metabolites generated during the xylose metabolism affected the test results.

Fermentation was carried out using six strains in order to grasp the fermentation pattern of the waste liquid, hydrolyzate, generated in the process of manufacturing carbonized pellets. The results are shown in FIGS. 11 and 12. FIG. 11 is a graph showing the change in sugar content according to the fermentation period using six yeasts in the waste liquid generated in the semi-carbonization process, and FIG. 12 is a graph showing changes in the sugar content during the fermentation period using six yeasts It is a graph showing the change of reducing sugar.

The initial sugar content of the hydrolyzate was 8.5, and the experimental groups using Saccharomyces bayanus, Saccharomyces cerevisiae, and Candida tropicalis decreased to less than 5.6 after 2 days of fermentation. Pachysolen tannophilus and Candida shehatae strains consumed glucose continuously until 10th day of fermentation and final sugar content was around 6. On the other hand, the experimental group using Pichia stipitis consumed almost no sugar and the final sugar content was 7.5. In the fermentation using hydrolyzate, the content of reducing sugar was similar to the change. Saccharomyces bayanus, Saccharomyces cerevisiae, and Candida tropicalis strains showed 3% reduction sugar content in 2 days after fermentation. The contents of reducing sugar decreased by 14 days after fermentation and the content of final reducing sugar was about 3% in the experimental groups using Pachysolen tannophilus and Candida shehatae strains. The Pichia stipitis strain showed the highest value of more than 5% in the final reducing sugar content.

The content of ethanol produced as a result of fermentation of the hydrolyzate is shown in Table 5 below. In the second day of fermentation, the ethanol content of Candida tropicalis, Saccharomyces bayanus, and Saccharomyces cerevisiae was higher than 1.56% , and the fermentation rates of Pichia stipitis, Pachysolen tannophilus and Candida shehatae were 0.31% or less Respectively. On the 14th day of fermentation, ethanol content was 1.68-1.84% in all experimental groups except Pichia stipitis . Ethanol content of the fermented group was highest in Saccharomyces bayanus and Saccharomyces cerevisiae . These results indicate that all of the five yeasts except for Pichia stipitis can be used as yeast for the production of bioethanol using hydrolyzate. Especially, considering the fermentation rate, Saccharomyces bayanus, Saccharomyces cerevisiae, Candida tropicalis strains are used Would be efficient.

Yeast Ethanol (%) Day 2 Day 14 Pichia stipitis 0.18 0.38 Pachysolen tannophilus 0.24 1.76 Candida shehatae 0.31 1.75 Candida tropicalis 1.56 1.68 Saccharomyces femaleus 1.84 1.83 Saccharomyces cerevisiae 1.63 1.84

Developed countries such as Europe and the US have introduced Renewable Portfolio Standards (RPS) since 2002, and despite the fact that forest-based biomass is in short supply due to the continuous expansion of the proportion of wood pellet fuel Agricultural waste such as oilseed rape, sunflower stand, cornstalks and waste mushroom badges are used as compost with low added value, or have low calorific value compared to forest biomass and high ash content and are not utilized as energy resources. Agricultural products such as oilseed rape, sunflower barn, and cornstalks are expected to have a higher hemicellulose content than wood, resulting in a higher rate of ozone conversion and bioethanol yield.

Up to now, bio-ethanol production technology using woody biomass has been focused on the development of a technology for fermenting hexose, such as saccharification of cellulose and glucose, and development of technology for saccharification and fermentation of pentose derived from hemicellulose is relatively inadequate . The most known ethanol-producing microorganisms to date are yeast-derived Saccharomyces cerevisiae, which have a high ethanol conversion rate but have a disadvantage in that xylose, which is a degradation product of hemicellulose, can not be used. The present invention enables saccharification and fermentation of pentose sugar as well as pentose sugar, thereby contributing to improvement of the yield of the woody bio-ethanol and commercialization of the bio-ethanol.

Currently, bioethanol has been commercialized mainly in Brazil and the US, and its production has increased greatly. However, all of these products are produced from biomass such as sugar cane or corn, which has already caused unstable grain prices. Will increase the unit price of bioethanol as soon as possible, so there is room for fuel price and even fuel supply problem.

Cellulose is the most abundant polymer on the planet, and it is an ingredient that can not be digested by humans unlike starch or sugar which is present in corn and sugarcane. It is based on wood-based ethanol fuel, Since it does not use the feedstock for fuel production, it is expected to contribute to easing competition with agricultural land and stabilizing food resource prices and supply and demand.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Therefore, it should be pointed out that the scope of the present invention is not limited to the described embodiments, but should be construed according to the appended claims.

Claims (5)

 The waste liquid produced during the production of carbonized pellets by the torrefaction of Ligno cellulo biomass is collected and fermented using yeast at 25 to 32 ° C to produce bioethanol ≪ / RTI > The method according to claim 1,
Wherein the woody biomass is woody sawdust comprising cellulose, semi-cellulose, and lignin;
The semi-carbonization is carried out by a process of applying heat at 220 to 280 ° C under oxygen depletion conditions;
The main components of the carbonized pellets are cellulose and lignin;
Wherein the waste liquid comprises a pentose component produced by decomposition of hemicellulose by heat. 3. The method of claim 2,
Wherein the pentane contained in the waste solution comprises xylose or arabinose. ≪ RTI ID = 0.0 > 11. < / RTI > The method of claim 3,
The yeast,
Pichia stipitis strain,
Pachysolen tannophilus strain,
A Candida shehatae var. Insectosa strain,
Candida tropicalis strain
Wherein the biodegradable microorganism is at least one selected from the group consisting of five degrading bacteria. 5. The method of claim 4,
The yeast,
Saccharomyces bayanus strain, and
Saccharomyces cerevisiae strain
Wherein the biodegradable microorganism further comprises at least one of six-sugar-degrading strains of the plant.

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