JPH0369514B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing alcohol, and in particular, to a first reaction tank containing immobilized microorganisms (hereinafter referred to as immobilized yeast) formed by immobilizing microorganisms capable of producing alcohol. The present invention relates to a method for producing alcohol, which comprises a step of carrying out alcoholic fermentation by continuously or intermittently supplying a medium suitable for culture. Processes of this type are known and can be operated stably with alcohol production yields of usually 60-80%. However, when the production yield is increased to, say, 80-100%, the activity of the immobilized yeast, for example, decreases, inhibiting its growth, and sometimes even killing some of the yeast, along with the increase in the alcohol concentration produced. Therefore, there is a limit to the stable increase in alcohol production yield. In other words, in the conventional batch method, for example, if blackstrap molasses is used as a raw material, stable production can be maintained at an alcohol production concentration of about 13-14%, whereas in the known method using immobilized yeast, stable production cannot be maintained. It is said that the upper limit of alcohol concentration that can be maintained is approximately 11%. In this case, the number of viable bacteria that separates from the immobilized yeast and flows into the mash is approximately 10 ⁶ -10 ⁸ cells/ml, which is approximately the same as the number of viable bacteria found in the mash of the batch method. It is.

The present inventor focused on this outflowing viable bacteria, and first, the mash liquid overflowing from the first reaction tank is received in a second reaction tank, and fermentation is continued in the second reaction tank. Disclosed a method for producing alcohol (Patent Application No. 108161/1983). By this method,
Highly concentrated alcohol can be produced at a sufficient production rate by omitting the seed fermentation step required in conventional batch methods.

The purpose of the present invention is to further improve the above-mentioned method, and by adding sugar to the mash liquid flowing out from the immobilized yeast in the first reaction tank, post-fermentation in the second reaction tank is carried out. This is based on the knowledge that production efficiency can be further improved.

The method of the present invention is characterized in that the mash liquid flowing out from the immobilized yeast in the first reaction tank is sent to the second reaction tank, and after sugar is added to the mash liquid, secondary fermentation is performed.

By the method of the present invention, highly concentrated alcohol can be stably produced at a good production yield.
Although it is difficult to obtain an alcohol concentration equivalent to that of the conventional batch method using a method using known immobilized yeast, the method of the present invention can produce alcohol at a concentration as high as that of the batch method in good yield. It can be produced continuously or intermittently.

The invention will now be described in detail.

The immobilized yeast used in the method of the present invention is not particularly limited as long as it is one in which alcohol-producing bacteria such as yeast are immobilized with a known gelling material and then placed in a suitable container. When an appropriate medium is continuously or intermittently supplied to the immobilized yeast, the yeast grows within the gel carrier and alcohol fermentation takes place. However, in alcoholic fermentation using immobilized yeast, cell leakage from the carrier is observed regardless of the immobilization method and materials used. Bacterial cell leakage from the carrier is related to, for example, the characteristics of the material of the carrier, and the leakage of bacterial cells is greater with a loose carrier than with a rigid carrier. Therefore, in order to carry out the secondary fermentation of the present invention, It is advantageous to choose a carrier that is easily released from the body. Examples of practical carriers include alginate, carrageenan, pectin, etc., and calcium alginate is particularly excellent.

Since the method of the present invention does not carry out alcoholic fermentation only in the first reaction tank, it is not necessary to carry out fermentation in the first reaction tank until the yeast is killed, unlike the known batch method. On the contrary, in the method of the present invention, the yeast in the first reaction tank is grown appropriately and then transferred to the second reaction tank.
It is important to feed the reactor. For this purpose, the sugar concentration in the first reaction tank should be adjusted, for example, at the inlet 15-20.
%, outlet 2-5%, outlet alcohol concentration 6.9-9
%. Thereby, the bacterial cell concentration at the outlet can be set to, for example, 10 ⁸ -10 ⁹ cells/ml. Other conditions are the same as those for normal alcoholic fermentation.

In the method of the present invention, the alcohol concentration in the first reaction tank can be kept lower than in the case of using a single reaction tank, so the lifespan of the immobilized microbial cells can be kept significantly longer.

In the second reaction tank, a final sugar concentration of 19-30% and a mash alcohol concentration of 11-18% are possible, and the necessary sugar solution and mash from the first tank can be received in the second reaction tank for a certain period of time. After that, post-fermentation is usually carried out for about 12-72 hours. The conditions for post-fermentation are not particularly different from those for normal alcoholic fermentation, but
It is desirable to increase the concentration of viable bacteria supplied to the second reaction tank as much as possible. For this purpose, it is proposed according to the invention to vent the mash that comes into contact with the immobilized yeast from the lower part of the first reaction vessel. The amount of ventilation depends on the equipment elements of the reaction tower (carrier shape, equipment height, etc.), but for a tank with a liquid depth of 3 m,
By aerating preferably 0.0001 VVM (Vol-air/Vol-tank, min) at 0.01 VVM or more, a high amount of viable bacterial cells can be obtained depending on the amount of aeration. Due to the increased ventilation rate, ventilation of about 10VVM is not a problem when operating under aerobic conditions. As a result, the concentration of viable bacteria in the runoff mash can be increased to 10 ⁸ -10 ⁹ cells/ml, yielding 2 to 5 times the amount of viable bacteria compared to the batch method, and shortening fermentation time. .

In the second reaction tank, for example, a mixed solution of mash and sugar solution can be fermented in a batch manner,
Alternatively, the mash may be continuously taken out after fermenting the mixed liquid for a certain period of time. The second reaction tank is preferably a complete mixing tank type reactor, and the reaction rate can be increased by further stirring, especially when using highly flocculating microorganisms such as yeast. Further, in the second reaction tank, it is preferable to use carbon dioxide gas generated in the immobilization reaction tank for stirring. Since the alcohol concentration in the second reaction tank is high, contamination by various bacteria is slight.

By collecting the bacterial cells flowing out of the second reaction tank using, for example, a centrifuge and returning them to the second reaction tank, the concentration of bacterial cells in the tank can be increased and the residence time in the tank can be shortened. Furthermore, by reducing the pressure or venting the second reaction tank, some or most of the alcohol can be removed from the liquid, thereby reducing alcohol inhibition in the second reaction tank, thereby reducing production. You can expect to improve your sexual performance.

The present invention does not expect the effect of simply connecting immobilized continuous fermentation and batch fermentation. The bacterial cell concentration in the mash flowing out from the immobilized continuous fermenter can be increased by aeration, and the fermentation rate is extremely slow or impossible with the conventional batch method or immobilized continuous method. You can get more moromi than that. For example, as in Example 1,
Sugar solution residence time in the first reaction tank is 2.5 hours and the second
An alcoholic mash of 14.6v/v% can be obtained in 48 hours of batch fermentation in a reactor. If only an immobilization reaction vessel is used to achieve this, the death of yeast in the reaction vessel cannot be prevented, which immediately leads to a decrease in alcohol concentration and an increase in residual sugar. This cannot be achieved even with the immobilization method in which the reaction vessels are multi-staged or the sugar solution is successively added in stages. The batch method only yields 13.0% v/v in 96 hours.

As described above, the present invention rationally combines the ability to grow yeast well in the first reaction tank and the use of the second reaction tank for alcohol production under conditions that kill the yeast, thereby taking advantage of the advantages of both. This is a new alcoholic fermentation method that has been skillfully used.

According to the method of the present invention, since the amount of yeast in the immobilization reaction tank is well-propagated, long-term stable operation is possible with a good production yield of alcohol at a high concentration.

Example 1 1 part of a wine yeast culture solution was added to 9 parts of a sterilized 3.3% sodium alginate aqueous solution and mixed. This mixed solution was dropped into a 2% calcium chloride aqueous solution through a nozzle to form a spherical gel with a diameter of 4 mm. The obtained gel was packed into two columns each having a capacity of 1.5 times each. A waste molasses aqueous solution added with water to give a sugar concentration of 150 g/hour was passed through one column (designated No. 1) at a rate of 1.2/hour. No.1
The mash in the column is led to the second reaction tank, and in parallel
Molasses with a sugar concentration of 60w/v% was added at 0.31/hr. The capacity of the second reaction tank was 80, and stirring was performed at 2 rpm using a small stirrer. After 24 hours, the reception of the sugar solution and No. 1 column mash was stopped, and stirring was continued for 48 hours. Analysis of the mash revealed that the alcohol concentration was 14.6%, and the yield based on the sugar used was 94% of the theoretical value, which was good.

Similarly, for the remaining column above,
A molasses aqueous solution with a sugar concentration of 150 g/hour was passed upward through the tower at a rate of 1.2/hour. Similarly, ventilation was performed at a rate of 0.3/min. After 100 hours, after sufficient yeast proliferation had progressed,
Sugar concentration was increased to 240g/. At the same time, the tower passing rate decreased by 0.3/hour. The alcohol concentration in the produced mash is 11.0v/v%, and the residual sugar concentration is 5.0-
It was as high as 5.5w/v%. Additionally, the tower speed was increased by 0.1.
/ hour, the alcohol concentration is
12.0v/v% was obtained. When I continued to pass through the tower, the alcohol concentration in the mash decreased after 7 days.
The alcohol concentration did not improve even when the alcohol concentration was lowered to 10.0% and the passing rate was further reduced.

As a control, a batch fermentation was also carried out. In the same manner as above, 10 ml of koji seed culture solution was prepared using wine yeast strain No. 2. Transfer this culture solution to a 500ml fermentation tube containing 15% sugar concentration molasses and 200ml of medium containing 0.1% ammonium sulfate.
ml, and 24 hours later, 50 ml of 60 w/v% sugar solution was added. Thereafter, alcohol analysis of the mash in the fermentation tube was performed every 24 hours. The alcohol concentration reached a maximum value of 13.0% 96 hours after the start of the reaction. The yield at this time remained at 90% of the theoretical value.

Comparing the experimental examples, it was found that the method according to the present invention provided the highest concentration of alcohol in good yield.

Example 2 Aqueous solution 1 containing 1.0% Na-type Katupa carrageenan [Mitsubishi Acetate Co., Ltd., Soagina MV-101] and 0.5% locust bean gum [Mitsubishi Acetate Co., Ltd., Soarlocust-A-200] was heat sterilized. After cooling, add 0.05 ml of yeast culture solution of Brewing Association Wine Yeast No. 2 and mix well. The mixed solution was dripped through a nozzle into an immobilization tank/fermentation tank containing 2 2% KCl aqueous solution that had been separately sterilized to form a bead-shaped gel. After standing still for 1 hour, molasses containing 16w/v% sugar and 0.1/min air were supplied from the bottom of the fermenter to prevent the residual sugar in the overflowing mash from increasing significantly.
The amount of sugar solution supplied was gradually increased. After 6 days, molasses was fed at a rate of 0.8/hour, and a mash of 9.5 v/v% was continuously obtained. This mash was led to a second fermentor with a capacity of 25, molasses containing 60 w/v% sugar was added at a rate of 0.2/h, and the supply of mash and sugar solution was stopped after 24 hours. When the second fermenter was maintained as it was and the mash was analyzed after 48 hours, 15.0 v/v% ethanol was found.

By mixing the sugar solution with the first tank mash and continuing fermentation, a mash with higher alcohol content can be obtained compared to the conventional batch method. A high-concentration alcohol mash was stably obtained semi-continuously for 3 months.

Claims (1)

[Claims] 1. A medium suitable for culturing the microorganism is continuously or intermittently supplied to a first reaction tank filled with immobilized microorganisms having immobilized microorganisms having alcohol-producing ability while venting from the bottom, and fermentation is carried out. 1
A method for producing high-concentration alcohol, which is characterized in that the mash from the reaction tank is sent to a second reaction tank not filled with immobilized microorganisms, sugar is added thereto, and fermentation is completed in a batch manner.