JP4401735B2 - Ethanol production method - Google Patents

Description

  The present invention relates to a production method for producing ethanol by fermentation using biomass, particularly woody biomass such as waste building materials, and relates to a nutrient source for microorganisms used in an ethanol fermentation process.

In recent years, domestic and overseas efforts have been made to produce ethanol from natural resources such as bagasse, rice straw, and wood chips, which are renewable resources, and use them as energy and chemical raw materials. In this method, a woody biomass is hydrolyzed with an acid or an alkali to obtain a hydrolyzed solution containing a sugar derived from hemicellulose such as glucose, and this sugar is converted to ethanol by a fermentation method using a microorganism such as yeast. .
Using waste building materials as raw materials for woody biomass is very promising in terms of collecting raw materials, which is an issue of biomass resource utilization.

By the way, in the fermentation process of woody biomass, in addition to sugar solution such as glucose obtained by hydrolyzing woody biomass with acid or alkali, nutrient sources containing nitrogen and phosphorus which are essential elements for the growth of microorganisms The existence of is required.
As the nutrient source, in the case of yeast, ammonium sulfate is generally used as an inexpensive nutrient source for commercial production (see, for example, Patent Document 1). When using E. coli, corn steep liquor (hereinafter referred to as “CSL”) is used (see, for example, Non-Patent Document 1). CSL is a byproduct produced in the process of producing corn starch from corn, and is a comprehensive nutrient source including amino nitrogen, phosphorus, minerals and the like.
Japanese Patent Publication No. 63-5079 Hugh G. Lawford, Joyce D. Rousseau, "Studies on Nutrient Requirements and Cost-Effective Supplements for Ethanol・ Production by Recombinant Ecorai (Studies on Nutrient Requirements and Cost-effective Supplements for Ethanol Production by Recombinant E. coli), “Applied Biochemistry and Biotechnology” (USA) Humana Press, Inc. (Humana Press Inc.), 1996, 57/58, p. 307-326

However, there is a problem that the CSL price is higher in Japan than in the United States where corn production is large.
Therefore, the inventors considered using inexpensive food waste as a nutrient source to replace CSL. Examples of such food waste include okara, coffee candy, and tea candy. In Japan, 750,000 tons of okara is generated annually, and although it is reused for feed, fertilizer, and food, it is in surplus. In addition, 600,000 tons of coffee mash generated mainly from the soft drink factory is discarded every year except for being used as fuel in the factory. As for tea bowls, green tea bowls generate 9,000 tons annually and oolong tea bowls generate 24,000 tons annually, and these are mainly used for livestock bedding and compost raw materials.
These food wastes are cheaper than CSL, and may be available upon receipt of collection fees such as processing costs as free or waste. These food wastes contain proteins, phosphorus, and minerals as components, and have the potential to be used as a nutrient source for microorganisms.

  However, most of the nitrogen contained in okara and tea bowls is in an insoluble protein form, and as such is hardly used as a nutrient source for microorganisms. Therefore, it is necessary to pretreat and solubilize part of the protein to obtain amino nitrogen. Common methods for solubilizing insoluble proteins by pretreatment of food wastes include heat treatment and enzyme treatment, but there are problems with high cost of enzyme treatment, and heat treatment is practical at present. Is.

  The present invention has been made in view of the above circumstances, and in a production method for producing ethanol by fermenting sugar obtained from woody biomass with microorganisms, as a nutrient source for microorganisms used in the fermentation step, food An object of the present invention is to provide a method for producing ethanol having a high fermentation rate using waste from a system.

The present invention relates to a method for producing ethanol by fermenting sugar obtained from woody biomass with microorganisms, as a nutrient source for microorganisms used in the fermentation process, from the group consisting of okara, teacup, and coffee lees There is provided a method for producing ethanol, characterized by using a product obtained by heat-treating at least one selected food waste in the presence of an acid .

  According to the ethanol production method of the present invention, in the production method for producing ethanol by fermenting sugar obtained from woody biomass with microorganisms, food waste is used as a nutrient source for microorganisms used in the fermentation process. In addition, the ethanol production method has a high ethanol fermentation rate and a reduced production cost.

  The manufacturing method of this embodiment is comprised from each process of hydrolysis, neutralization, fermentation, ethanol separation, and ethanol purification of woody biomass.

(Woody biomass)
Examples of the woody biomass that is a raw material include wood chips and waste building materials. Examples of the waste building materials include waste wood building materials, waste pallets, waste packaging materials, and the like. Waste building materials may be used alone or in combination of two or more. In addition, the waste building materials may contain impurities such as fermentation inhibitors such as acetic acid, furfural, levulinic acid, formic acid, adhesives, and paints.

(Hydrolysis step)
In the hydrolysis step, conventionally known acid hydrolysis methods and alkali hydrolysis methods can be used. Of these, the acid hydrolysis method is preferred. Examples of the acid used in the acid hydrolysis method include sulfuric acid, hydrochloric acid, nitric acid and the like, but it is preferable to use sulfuric acid.

(Neutralization process)
If an acid hydrolysis method or an alkali hydrolysis method is used after the hydrolysis step, a neutralization step is necessary. Examples of the alkali used in the neutralization step after hydrolysis by the acid hydrolysis method include Ca (OH) ₂ and NaOH, but it is preferable to use relatively inexpensive Ca (OH) ₂ .

(Fermentation process)
After the neutralization step, the obtained hydrolyzate is subjected to a fermentation step. In the fermentation process, ethanol is produced by fermentation by microorganisms. At this time, it also provides the necessary nutrients for the microorganisms. In this invention, what was obtained by heat-processing food waste is used as this nutrient source. Examples of the food waste include at least one selected from the group consisting of okara, tea bowl, and coffee bowl. For example, examples of the tea bowl include a green tea bowl, a black tea bowl, and an oolong tea bowl. These food wastes are given to microorganisms after heat treatment in order to convert the contained nitrogen into amino nitrogen. It is preferable that the temperature of heat processing is 100 to 250 degreeC.

In the present invention, when water is added to the food waste and heat-treated , the acid is added together and the heat treatment is performed in the presence of the acid. Examples of such an acid include sulfuric acid, hydrochloric acid, nitric acid and the like, but it is preferable to use sulfuric acid. The food waste can be easily solubilized by heat treatment with sulfuric acid. The conditions for the sulfuric acid heat treatment are a temperature of 100 ° C. to 250 ° C., a sulfuric acid concentration of 1% by mass to 10% by mass, and a heating time of 10 minutes to 100 minutes. Among them, it is preferable that the temperature is 120 ° C. to 200 ° C., the concentration of sulfuric acid is 3% by mass to 6% by mass, and the heating time is 10 minutes to 60 minutes. If the temperature is lower than 100 ° C., the solubilization does not proceed sufficiently.
In the present embodiment, a product obtained by separately performing a sulfuric acid heat treatment of food waste is used in the fermentation process as a nutrient source for microorganisms. For example, a food waste with a biomass raw material and sulfuric acid is hydrolyzed. It is also possible to heat the sulfuric acid heat treatment of the food waste during the hydrolysis process using existing equipment.
In addition, the residue of the food waste after using it as a nutrient source can be reused as energy used in equipment by using it as boiler fuel.

  The microorganism used in the present invention is preferably at least one microorganism selected from the group consisting of bacteria and yeast. Such bacteria include genetically modified E. coli. Here, genetically modified E. coli refers to those that have been introduced into E. coli that does not have the enzyme gene required for conversion to ethanol, etc., by genetic engineering technology, allowing fermentation to ethanol, etc. . Known yeasts can be used as the yeast, and specific examples include Saccharomyces cerevisiae and Schizosaccharomyces pombe.

(Ethanol separation process / purification process)
The fermentation liquor obtained after the fermentation process is subjected to a separation process for separating ethanol produced by fermentation. As a method for separating ethanol, known methods such as distillation and pervaporation membrane are used, and distillation is preferable among them.
The separated ethanol is then subjected to a purification process. As the ethanol purification method, a known method such as distillation can be used.

Hereinafter, the present invention will be described in more detail with reference to experimental examples and examples.
[Experimental example 1-4, comparative test]

Water or sulfuric acid is added to okara (purchased from a tofu store, water content 76% by mass), heat-treated, filtered, and the total nitrogen concentration (g / L) of soluble amino eluted in the filtrate is liquid chromatographed. (Use model: D-7000 type (manufactured by Hitachi, Ltd.), column: HPX-87P (manufactured by BIO-RAD)).
Experimental Example 1: 200 ml of water was added to 100 g of okara and heat-treated at 120 ° C. for 60 minutes.
Experimental Example 2: 200 mL of 2% by mass sulfuric acid was added to 100 g of okara and heat-treated at 120 ° C. for 60 minutes.
Experimental Example 3: 200 g of 5 mass% sulfuric acid was added to 100 g of okara and heat-treated at 120 ° C for 60 minutes.
Experimental Example 4: 200 mL of 10 mass% sulfuric acid was added to 100 g of okara and heat-treated at 120 ° C for 60 minutes.
Comparative test: 200 mL of water was added to 100 g of okara.
Table 1 shows the experimental conditions and results.

Comparing Experimental Example 1 and the comparative test, by adding water to okara and heating it, a total nitrogen concentration nearly four times that of the comparative test without heating was obtained.
Moreover, when Experimental Example 1 and Experimental Example 2-4 were compared, the total nitrogen concentration obtained increased to 1.3-1.6 times by adding sulfuric acid.
From these experimental examples, it was confirmed that the heat treatment is effective as a conversion treatment of food waste to a microbial nutrient source.

[Example 1]
What was obtained by heat-processing the food-type waste in this invention was actually used as a nutrient source of microorganisms, ethanol fermentation was performed, and the fermentation rate of ethanol was investigated.
To a 300 mL flask, 50 mL of glucose 45 g / L and xylose 45 g / L were added as carbohydrates, and nutrient sources of the following sample numbers “1-A” to “1-C” were added. 11303) was inoculated and ethanol fermentation was performed at 35 ° C. and 100 rpm for 50 hours.

As a nutrient source, 200 g of water was added to 100 g of okara and heat-treated at 120 ° C. for 60 minutes, and the amount added to the medium was changed (sample numbers “1-A” to “1-C”).
Sample number “1-A”: addition amount 1.7% by mass
Sample number “1-B”: addition amount 3.3 mass%
Sample number “1-C”: addition amount 6.7% by mass

After completion of the fermentation, the ethanol concentration (g / L) in the solution was measured by gas chromatography under the following conditions.
Model used: GC353B (manufactured by GL Sciences)
Column: CP-WAX52CB (manufactured by VARIAN)
Moreover, ethanol fermentation rate (%) was calculated | required by the following formula | equation (I) from the measured ethanol concentration (g / L).
Ethanol fermentation rate (%) = (ethanol concentration) / (total added carbohydrate concentration) /0.51×100 (I)
In the formula (I), 0.51 is a coefficient, which is a mass ratio of ethanol to saccharide produced when the saccharide is completely changed into ethanol and carbon dioxide by fermentation reaction.
The experimental conditions are shown in Table 2, and the results are shown in FIG.

[Example 2-4]
As a nutrient source, a medium obtained by adding 200 mL of sulfuric acid having a changed concentration to 100 g of okara and heat-treating at 120 ° C. for 60 minutes (sample numbers “2-A” to “4-C”) is used. Fermentation was carried out in the same manner as in Example 1 except that the amount to be added was changed to obtain the ethanol fermentation rate (%). Detailed experimental conditions are shown in Table 2, and the results are shown in FIG.

[Example 5-7]
As a nutrient source, 100 g of dried green tea bowl (water content 5% by mass) was added with 200 mL of water or sulfuric acid having a different concentration, and heat-treated at 120 ° C. for 60 minutes (sample number “5-B” to “7-C”) was used and fermentation was performed in the same manner as in Example 1 except that the amount added to the medium was changed, and the ethanol fermentation rate (%) was determined. Detailed experimental conditions are shown in Table 2, and the results are shown in FIG.

[Example 8-9]
As a nutrient source, 100 g of dried oolong teacup (water content 4% by mass) was added with 200 mL of water or sulfuric acid having a different concentration, and heat-treated at 120 ° C. for 60 minutes (sample number “8-B” to “9-C”) was used and fermentation was performed in the same manner as in Example 1 except that the amount added to the medium was changed, and the ethanol fermentation rate (%) was obtained. Detailed experimental conditions are shown in Table 2, and the results are shown in FIG.

[Example 10-11]
As a nutrient source, 100 g of dried coffee cake (water content 5 mass%) was added with 200 mL of water or sulfuric acid having a different concentration, and heat-treated at 120 ° C. for 60 minutes (sample number “10-B” to “11-C”) was used and fermentation was performed in the same manner as in Example 1 except that the amount added to the medium was changed, and the ethanol fermentation rate (%) was determined. Detailed experimental conditions are shown in Table 2, and the results are shown in FIG.

[Comparative Example 1]
Fermentation was performed in the same manner as in Example 1 except that CSL 3.5% by mass (sample number “100”) was used as a nutrient source, and an ethanol fermentation rate (%) was obtained. Detailed experimental conditions are shown in Table 2, and the results are shown in FIG.

[Comparative Example 2]
As a nutrient source, fermentation was performed in the same manner as in Example 1 except that the amount of okara that was not heat-treated was added to the medium (sample numbers “200-A” to “200-C”). The fermentation rate (%) was determined. Detailed experimental conditions are shown in Table 2, and the results are shown in FIG.

[Comparative Example 3]
As a nutrient source, fermentation was performed in the same manner as in Example 1 except that the amount of green tea cake that was not heat-treated was added to the culture medium (sample numbers “300-B” to “300-C”). The fermentation rate (%) was determined. Detailed experimental conditions are shown in Table 2, and the results are shown in FIG.

[Comparative Example 4]
As a nutrient source, fermentation was performed in the same manner as in Example 1 except that the amount of oolong teacup not subjected to heat treatment was added to the medium (sample numbers “400-B” to “400-C”). The fermentation rate (%) was determined. Detailed experimental conditions are shown in Table 2, and the results are shown in FIG.

[Comparative Example 5]
As a nutrient source, fermentation was conducted in the same manner as in Example 1 except that the amount of coffee mash that was not heat-treated was added to the culture medium (sample numbers “500-B” to “500-C”). The fermentation rate (%) was determined. Detailed experimental conditions are shown in Table 2, and the results are shown in FIG.

[Comparative Example 6]
Fermentation was performed in the same manner as in Example 1 except that no nutrient source was added to the medium (sample number “600”), and the ethanol fermentation rate (%) was determined. Detailed experimental conditions are shown in Table 2, and the results are shown in FIG.

When Example 1-4 and Comparative Example 2 are compared, even if the addition amount is 6.7% by mass (sample number “200-C”), the ethanol fermentation rate is 10%. In contrast to the following, in Example 1 in which okara was heat-treated, the fermentation rate was improved to 30% or more (sample number “1-C”). Furthermore, in Example 2-4 to which sulfuric acid was added, the fermentation rate was 50% (sample number “2-C”), 60% (sample number “3-C”), 40% (sample number “4-C”). ) Improved.
From these facts, it was confirmed that by heating okara, it can be used as a nutrient source for microorganisms in the ethanol fermentation process, and ethanol can be produced at a high fermentation rate.

Comparing Example 5-11 with Comparative Example 3-5, the amount of addition of 6.7% by mass (sample number “300- C ”,“ 400-C ”,“ 500-C ”), the ethanol fermentation rate was 10% or less, whereas in Examples 5, 8, and 10 that were heat-treated, the fermentation rate was 45% (sample). No. “5-C”), 35% (Sample No. “8-C”), and 15% (Sample No. “10-C”). Furthermore, in Examples 6, 7, 9, and 11 to which sulfuric acid was added, the fermentation rates were 80% (sample number “6-C”), 70% (sample number “7-C”), and 90% (sample number), respectively. “9-C”), 70% (sample number “11-C”). The fermentation rates of Examples 6, 7, 9, and 11 were as high as the 90% fermentation rate of the CSL of Comparative Example 1. Moreover, the fermentation rate of the comparative example 6 which did not add a nutrient source did not reach 5%.
From these, it was confirmed that heat treatment of green tea bowl, oolong tea bowl, and coffee bowl can be used as a nutrient source for microorganisms in the ethanol fermentation process, and ethanol can be produced at a high fermentation rate.

It is the graph which showed the ethanol fermentation rate (%) of Example 1-4 and Comparative Example 1-2. It is the graph which showed the ethanol fermentation rate (%) of Example 5-11 and Comparative Example 3-6.

Claims (4)

In the production method of producing ethanol by fermenting sugar obtained from woody biomass with microorganisms,
As a nutrient source of microorganisms used in the fermentation process,
A method for producing ethanol, comprising using at least one food waste selected from the group consisting of okara, tea bowl, and coffee koji in the presence of an acid. .   The method for producing ethanol according to claim 1, wherein the heat treatment is performed under conditions of a sulfuric acid concentration of 1 mass% to 10 mass% and a temperature of 100C to 250C.   The method for producing ethanol according to claim 1 or 2, wherein the woody biomass is a waste building material. The method for producing ethanol according to any one of claims 1 to 3, wherein the microorganism is at least one microorganism selected from the group consisting of bacteria and yeast.

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