JPH0338835B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) This invention relates to a method for fermentative production of ethanol. (Prior Art) The usual raw material for producing ethanol by fermentation is molasses, and molasses contains non-fermentable sugars in addition to sucrose, glucose, and fructose. Non-fermentable sugars are sugars that cannot normally be fermented by the microorganisms used when the sugars are subjected to alcoholic fermentation, such as lactose, xylose, rhamnose, cellobiose, trehalose, melibiose, raffinose, etc. be. Raffinose is contained in large amounts in molasses, which is a raw material for sugar beets, but when Saccharomyces sp is used as a microorganism, one-third of the amount is converted to fructose and two-thirds is converted to melbiose. The content of non-fermentable sugars varies depending on the raw material source, but the content ranges from about 5 to 11% of the total sugars in molasses. Molasses containing non-fermentable sugars is supplied to the fermenter as a raw material, a certain amount of fermentation liquor is continuously extracted from the fermenter, and product ethanol is separated and recovered from the extracted fermentation liquor. In a continuous ethanol production method in which the residual liquid after separation and recovery is returned to the fermenter, accumulation of non-fermentable sugars must be prevented. If non-fermentable sugars accumulate in the system, the concentration of non-fermentable sugars increases, the osmotic pressure of the fermentation liquid increases, the fermentation efficiency of microorganisms decreases, and eventually the cell membranes of microorganisms are damaged and the microorganisms die. . Similarly, the ash contained in the raw molasses that enters the system accumulates in the system, and its concentration increases, which increases the osmotic pressure of the fermentation liquid, reduces the fermentation efficiency of microorganisms, and eventually damages the cell membranes of microorganisms. and the microorganisms die. There is no economical method for separating and recovering only non-fermentable saccharides from the system. Therefore, the process stream is divided into two at an appropriate position in the system, and one divided stream containing an amount of non-fermentable saccharides corresponding to the amount of non-fermentable saccharides that enters the system as contained in the raw molasses enters the system. Extracted to the outside continuously or intermittently. (Problems to be Solved by the Invention) A disadvantage of this method for preventing the accumulation of non-fermentable sugars is that along with the non-fermentable sugars, useful fermentable sugars and, in some cases, a small amount of the product ethanol are also lost. As mentioned above, non-fermentable sugars are the total sugars in molasses,
Since the content reaches a minimum of 5% and a maximum of 11%, it is difficult to overlook the amount of useful components escaping when extracted from the system. (Means for Solving the Problems) This invention involves converting non-fermentable saccharides into useful fermentable saccharides by enzymes at the position where non-fermentable saccharides are most concentrated during the process, and then This method prevents the accumulation of non-fermentable sugars in the system by converting the fermentable sugars produced by the conversion into the product ethanol in the fermenter. In the method of the invention, carbohydrases and/or sugar isomerases are used as enzymes for converting non-fermentable sugars into fermentable sugars. Carbohydrase is a general term for galactosidase, melibiase, glucosidase, etc., and it processes non-fermentable sugars such as lactose, raffinose, melibiose, cellobiose, and trehalose.
Converted to fermentable sugars such as galactose, glucose, and fructose. Glucose isomerase is a common name established for industrial purposes, and is a general term for enzymes that mutually transfer aldose and ketose. For example, it converts xylose, a non-fermentable sugar, to xylulose, a fermentable sugar. . In the method of this invention, 75wt of non-fermentable saccharide is added to fermentable saccharide, although it varies depending on the saccharide raw material.
It is preferable to carry out ethanol fermentation by controlling the content to 60wt% or less, and more preferably to 60wt% or less. In the method of this invention, it is effective to use an electrodialysis device to prevent the accumulation of ash in order to prevent the accumulation of non-fermentable sugars, and to extract the inorganic salts in the fermentation liquid to the outside of the system. . Originally, enzymes are catalysts formed within the cells of living organisms, and they are organic compounds with a complex structure.As they have poor heat resistance, they lose their activity in places where the fermentation liquid is exposed to high temperatures, such as in an ethanol evaporation tank. Therefore, it is appropriate to use the product under temperature conditions as close to room temperature as possible. Therefore, in the current state of the art, it is desirable that the fermented liquor passed through the two-stage ethanol evaporator and then subjected to enzyme treatment is treated with the enzyme. For example, a fermentation liquor that has been subjected to an enzyme treatment in which non-fermentable sugars are converted to fermentable sugars immediately after being discharged from a first evaporator is subjected to a second evaporation treatment before being supplied to the next fermenter. It's okay. In this invention, it is extremely effective to remove water and concentrate sugar content using a reverse osmosis device before and after the fermentation liquid is subjected to enzyme treatment. When concentration is performed using a reverse osmosis device prior to enzyme treatment, the higher the sugar concentration, the higher the enzyme treatment rate, as long as the enzyme is within the limit of substrate damage. If concentration is performed using a reverse osmosis device, the concentration of fermentable sugars in the fermentation liquid supplied to the primary fermenter and subsequent fermenter will increase, and the fermentation rate in the fermenter will increase. , the effective volume of the fermenter increases, making it possible to downsize it, and the ethanol concentration in the fermenter effluent also increases. The reverse osmosis membrane used in the reverse osmosis device should be one that does not substantially allow sugar to pass through, does not allow ethanol to pass through as much as possible, and has as high heat resistance as possible, and should not allow salt content in the fermentation liquid to pass through. Regarding this, it is desirable that the permeability be as high as possible because there will be no increase in osmotic pressure due to increases in salt concentration, and the activity of microorganisms will be maintained. In this invention, when a two-stage ethanol evaporator is used, the evaporation in the first evaporator is
0.8~1.2ata・75~105℃ or 1.2~10ata・95
The temperature is within the range of ~180°C, and the evaporation of the fermentation liquid in the second evaporation tank is within the range of 20-200 mmHg and 25-65°C. In this invention, when a two-stage ethanol evaporator is used, the evaporated air in the first evaporator and/or the pressurized evaporated air in the second evaporator is supplied to the condenser, and the evaporated air in the second evaporator is supplied to the condenser. The fermentation liquor of the evaporator effluent is advantageously used as an absorption liquor for ethanol in the condenser effluent gas and/or the second evaporator exhaust gas. In this invention as well, a minimum amount of fermentation liquid is extracted from the system in order to discharge accumulated substances from the system, but the enzymes contained in the extracted fermentation liquid are naturally lost, and enzymes are needed to compensate for this loss. Replenishment is necessary. In this invention, it is effective that the carbohydrase and/or glucose isomerase used are immobilized enzymes that are immobilized on a carrier. Since enzymes are usually water-soluble, enzymes for converting non-fermentable saccharides to fermentable saccharides may be added directly to the fermentation broth, but in order to reduce the amount of enzyme supplementation required, Furthermore, immobilization of enzymes tends to improve both heat resistance and chemical resistance, that is, resistance to substances that are raw materials and other components that inhibit enzyme activity. , the use of immobilized enzymes immobilized on carriers is effective. Various methods have been researched and proposed for enzyme immobilization, but the most common and simple method is to prepare a mixed aqueous solution of sodium alginate and the enzyme, and then add this aqueous solution to a calcium chloride aqueous solution. Dropwise, small particles of water-insoluble calcium alginate containing the enzyme are produced. The fermentation liquid to be enzyme-treated is caused to flow through the packed bed made up of the small particles. As another method, the enzyme and resin monomer powder are mixed, molded into a desired shape, and then the resin supporting the enzyme is cured by radiation or ultraviolet rays to form an immobilized enzyme. In the method of this invention, immobilized microorganisms, flocculent microorganisms, or planktonic microorganisms are used as microorganisms in the fermenter. When flocculent microorganisms or planktonic microorganisms are used as microorganisms in the fermenter, the microorganisms are separated from the fermentation liquor before the fermentation liquor extracted from the fermenter is supplied to the evaporator or heat exchanger,
It is sent back to the fermenter. In the method of this invention, the ethanol concentration in the fermenter is maintained below 8 wt%. Conventionally, when raw sugars are cellulose-based, that is, produced from wood, bagasse, rice straw, wheat straw, or other resources, the large amount of xylose derived from hemicellulose in these resources has been a serious problem. However, in the method of the present invention, xylose, which is a non-fermentable saccharide, is converted into xylulose, which is a fermentable saccharide, by the action of glucose isomerase, and finally recovered as product ethanol by the action of microorganisms. (Effects of the Invention) According to the method of the present invention, it is possible to prevent non-fermentable sugars from accumulating in a fermenter during ethanol fermentation, and to perform ethanol fermentation efficiently and continuously. According to this invention, non-fermentable saccharides are also converted into useful fermentable saccharides, which are also used as fermentation raw materials to produce ethanol, which is an excellent effect. (Example) The method of this invention is explained by an example and a comparative example.
This will be explained in more detail. Example 1 The method of the present invention was carried out according to the flow sheet shown in FIG. In Figure 1, an aqueous solution containing nutrients, etc. in addition to fermentable sugars (cane molasses from the Philippines)
hr was supplied to the first fermenter 1 from line 21. The first fermenter 1 contained bead-shaped immobilized yeast (Saccharomyces cerevisiae on a calcium alginate carrier).
(fixed) was filled with 2500. In the upper part of fermenter 1, 99.7 kg/hr of ethanol was produced. Of this, 0.3Kg/hr is the carbon dioxide gas generated, which is 95.3Kg/hr.
The remaining 99.4Kg/
hr is fermentable sugars 5.0Kg/hr, non-fermentable sugars 22.0
Kg/hr is supplied from the line 23 to the heat exchanger 7 for preheating, and then the line 24 is supplied to the upper part of the first evaporation tank 3.
Supplied from. Ethanol is released from the top of this evaporation tank.
Steam consisting of 89.2 Kg/hr and water 143.7 Kg/hr is discharged from line 28 and supplied to heat exchanger 7, where it is condensed. On the other hand, the amount of ethanol in the evaporation residue extracted from the bottom of the first evaporation tank 3 into the line 25 was 10.2 Kg/hr. This evaporation residual liquid is HR99 (product name) manufactured by DDS.
The line 2 is supplied to a reverse osmosis membrane device 5 equipped with a membrane.
6, 917.9 Kg/hr of water was taken out as permeate. The concentrated liquid taken out from the reverse osmosis membrane device 5 to the line 27 contains ethanol 10.2Kg/hr and fermentable sugars.
5.0Kg/hr, non-fermentable sugars 22.0Kg/hr, water 726.1
It was Kg/hr. This concentrated liquid is supplied to the upper part of the second evaporation tank 4, and from the top of the second evaporation tank 4, ethanol is
Steam consisting of 7.9Kg/hr and water 199.9Kg/hr is supplied from the line 30 to the vacuum pump 6 and compressed to atmospheric pressure, and then supplied to the heating coil provided in the second evaporation tank 4 to generate the necessary At the same time as supplying heat of vaporization, 7.9Kg/hr of ethanol is condensed from line 31.
I got it. On the other hand, ethanol 2.3Kg/hr, fermentable sugars 5.0Kg/hr, non-fermentable sugars 22.0Kg/hr, water 526.2
The evaporation residue consisting of Kg/hr was fed from line 29 to the immobilized enzyme reactor 9. The immobilized enzyme reactor 9 contains E coli-derived galactosidase immobilized on polyacrylamide and commercially available immobilized glucose isomerase at 1:1.
They were mixed at a ratio of 1:1 and filled 1,000 times. In the immobilized enzyme reactor 9, non-fermentable sugars are converted to fermentable sugars. Non-fermentable sugars 22.0
Kg/hr decreased to 12Kg/hr, fermentable sugars 5.0Kg/hr.
hr increased to 15.0Kg/hr from line 41 to washing tower 8.
was supplied to. Carbon dioxide gas is emitted from the top of washing tower 8.
102.1Kg/hr, water 1.8Kg/hr are discharged from line 43, and fermentable sugars 15Kg/hr are discharged from the bottom of washing tower 8.
Ethanol 2.6 Kg/hr, water 528.7 Kg/hr, non-fermentable sugars 12.0 Kg/hr, and ash 20.0 Kg/hr were supplied to the second fermenter 2 from the line 32. Similar to the first fermenter 1, the second fermenter 2 contains bead-shaped immobilized yeast (on a calcium alginate carrier).
fixed Saccharomyces cerevisiae)
500 filled. In the second fermenter 2, ethanol 0.01Kg/
hr, water 0.2Kg/hr is carbon dioxide gas generated 6.8Kg/hr
Both are discharged from line 33, and from line 34 9.7Kg/hr of ethanol, 1.0Kg/hr of fermentable sugars, and water are discharged.
528, 5Kg/hr, non-fermentable sugars 12.0Kg/hr, ash content
It was possible to produce a fermented liquid containing 20.0 kg/hr. Throughout the entire process, 106.8 Kg/hr of ethanol (average concentration 10.9 wt%) was produced. Therefore, assuming that the total amount of fermentable saccharides and non-fermentable saccharides were converted to ethanol as 100%, the ethanol yield was 94.1%. The results are shown in Table 1. Example 2 The method of the present invention was carried out according to the flow sheet shown in FIG. In this case, the same procedure as in Example 1 was carried out except that the electrodialyzer 10 was provided. In FIG. 2, the same symbols as in FIG. 1 indicate the same things. Therefore, in FIG. 2, the first fermenter 1, the second fermenter 2,
The packing material for each of the immobilized enzyme reactors 9 was as described in Example 1.
It is similar to Before the evaporation residual liquid distilled from the lower part of the first evaporation tank 3 was supplied to the reverse osmosis membrane device 5, the ash content in the evaporation residual liquid was separated in an electrodialysis device 10, and the ash content was discharged through a line 47. Operated under the conditions shown in Table 1, throughout the process,
Ethanol 106.9Kg/hr (average concentration 18.9wt%) was produced. Therefore, assuming that the total amount of fermentable saccharides and non-fermentable saccharides were converted to ethanol as 100%, the ethanol yield was 94.2%. The results are shown in Table 1. Comparative Example 1 Example 1 except that the immobilized enzyme reactor 9 was not used.
Ethanol fermentation was carried out in the same manner as above according to the flow sheet shown in FIG. In this figure, the same symbols as in FIG. 1 indicate the same things. In FIG. 4, the filler and filling amount of the first fermenter 1 and the second fermenter 2 were the same as in Example 1. By operating under the conditions shown in Table 1, 2.6 kg/hr of ethanol and fermentable sugars were produced from the line 34 of the second fermenter 2.
1.0Kg/hr, water 528.6Kg/hr, non-fermentable sugars 22.0
A fermentation liquid was obtained with an ash content of 20.0 Kg/hr and an ash content of 20.0 Kg/hr. Example 3 The method of the present invention was carried out according to the flow sheet shown in FIG. The figure shows line 3 of immobilized enzyme reactor 2.
The procedure was the same as in Example 2, except that the fermentation liquor from No. 4 was partially circulated to line 23 through circulation line 45, and the operation was carried out in the same manner as in Example 2 under the conditions shown in Table 1. In Figure 3, rice straw is pretreated with alkaline and then hydrolyzed using cellulase to produce sugars (fermentable sugars such as glucose derived from cellulose and non-fermentable sugars such as xylose derived from hemicellulose). ) into the first fermenter 1 as raw material
2300 and 2000 were filled into the second fermenter 2, respectively. The immobilized enzyme reactor 9 was filled with 2000 glucose isomerase alone. Throughout the entire process, 159.2 Kg/hr of ethanol (average concentration 15.6 wt%) was produced. Therefore, assuming that the total amount of fermentable saccharides and non-fermentable saccharides were converted to ethanol as 100%, the ethanol yield was 97.3%. The results are shown in Table 1. This result shows that the circulation line 45 significantly improved the yield.

【table】

【table】

【table】 [Brief explanation of drawings]

Figure 1 shows an embodiment of the present invention in which an electrodialysis device is not installed but an immobilized enzyme reactor is installed.
Fig. 2 shows an embodiment of the present invention in which an electrodialysis device and an immobilized enzyme reactor are installed, and Fig. 3 shows an embodiment in which an electrodialysis device and an immobilized enzyme reactor are installed. This is an embodiment of the present invention in which most of the fermentation liquor is circulated to the fermentation liquor discharged from the upper part of the first fermenter, and Figure 4 shows a comparative example in which an electrodialysis device and an immobilized enzyme reactor are not installed. be. Explanation of symbols: 1...First fermenter, 2...Second fermenter, 3...First evaporator, 4...Second evaporator, 5
... Reverse osmosis membrane device, 6 ... Vacuum pump, 7 ... Heat exchanger, 8 ... Washing tower, 9 ... Immobilized enzyme reactor, 10 ... Electrodialysis device, 21, 22 ... Line, 23 , 24... line, 25, 26... line, 27, 28... line, 29, 30... line, 31, 32... line, 33, 34... line, 41, 42... line, 43, 44... line, 45, 46... line, 47... line.

Claims (1)

[Claims] 1. A method in which a fermented liquor extracted from a fermenter and substantially free of microorganisms is subjected to evaporation treatment, and ethanol in the fermented liquor is transferred to the gas phase, separated, and recovered. , after the fermentation liquor flowing out of the evaporator is treated with carbohydrase and/or glucose isomerase to convert non-fermentable sugars that are not utilized by the microorganisms in the fermenter into fermentable sugars, the raw fermenter and/or other supplied to the fermenter,
A fermentation production method for ethanol characterized by the following.