JPH07112436B2 - Method for producing alcohol by repeated batch fermentation - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing alcohol efficiently by appropriately repeating batch fermentation.

More specifically, the present invention provides that the flow rate of the fermentation exhaust gas is 0.35 to 0.1 m ³ per hour per 1 liter of the fermentation liquor.
Alternatively, the present invention relates to a method for efficiently producing alcohol by moving to the next batch fermentation when the time when the temperature becomes lower than that is set as the end point of fermentation.

The batch fermentation method of the present invention has a high alcohol productivity and is extremely efficient as compared with the conventional batch fermentation method, and thus has a great contribution to the alcohol production world.

[0004]

2. Description of the Related Art Generally, batch fermentation is the mainstream method for producing alcohol by fermentation. In recent years, alternative fermentation methods such as a repeated batch method, a semi-continuous method, and a continuous method have been studied, and some of them are being put to practical use. Conventionally, in the batch system or the repeated batch system, as a method of confirming the end point of fermentation, a method of measuring an alcohol concentration or a method of measuring a residual sugar amount has been adopted. Further, as an empirical simple confirmation method, the state of the fermentation exhaust gas generated from the surface of the fermented liquid can be observed, the density of the fermented liquid can be measured, or the turbidity of the fermented liquid can be observed or measured to determine the end point of the fermentation. It has also been confirmed. Therefore, those that require a long time for analysis and measurement,
There were many things that required experience and skill to confirm the judgment. This is due to the fact that the simple analysis and measurement technology of fermentation liquor is behind, and the raw material used is a natural agricultural product and contains an extremely large number of components. Further, since the quality of raw materials, the activity of yeast, the type and number of mixed bacteria, etc. change delicately each time, the pattern of the fermentation process varies greatly even when the same method is used. In addition, the conventional fermentation process has many batch processes, and since the use of liquor is rarely used more than once, the yeast activity is reduced due to the influence of alcohol produced. There was almost no need to grasp the end of fermentation quickly before moving to the next step. Furthermore, attempts have been made to increase the fermentation rate itself, and studies have been made on methods for shortening the time required for analysis and measurement, but few have been put to practical use. Despite the strong demand for rapid and accurate analytical and measurement methods for fermentation control in the practical application of repeated batch methods, semi-continuous methods, continuous methods, etc., which have recently been widely studied. Since the analysis takes time, the conventional method that cannot increase the number of times of sampling or the number of samples is used as it is. Due to this, the practical application of a fast and stable fermentation method has been delayed.

[0005]

DISCLOSURE OF THE INVENTION The present invention overcomes the drawbacks of these conventional methods and allows each batch of fermentation to be carried out rapidly with high-density cells, and the completion of fermentation can be grasped accurately and promptly. The purpose of the present invention is to provide an alcohol production method by a continuous batch fermentation method that is stable for a long period of time and then switches to the next batch.

In the present invention, it has been found that the end of batch fermentation can be determined by using a gas flow meter of the type that measures velocity head.

Further, in the present invention, a gas flow meter of the method for measuring the velocity head is used, and the flow rate of the fermentation exhaust gas is 0.35 to 0.1 m ³ or less per hour per fermentation liquid, preferably, Efficient production of alcohol could be achieved by terminating the batch fermentation when it reached 0.3 to 0.15 m ³ and promptly shifting the yeast to the next batch fermentation.

In the present invention, first, the raw material is fed to the liquor mother tank 1 shown in FIG. 1 so that the sugar concentration becomes 9 to 16%, and water is added. A sterilization treatment is performed at a sterilization temperature of 90 to 120 ° C. for 0.5 to 1 hour and then cooled. After that, yeast is inoculated and liquor mother, which is a starter of fermentation, is charged. In this liquor mother preparation, an appropriate subsidy agent such as ammonium sulfate is added if necessary. Although there is some guideline for the amount to be added, the quickest method is to carry out a flask test using the same raw material and predetermine the optimum addition concentration. Upon yeast inoculation, seed yeast that has been cultivated in a flask in advance is aseptically added to prevent contamination of various bacteria. The liquor mother tank is not particularly limited as long as it has a material and a structure that can withstand heating conditions for sterilization. Generally, steam heating is the mainstream, but it is equipped with auxiliary equipment such as a thermometer, pressure gauge, and safety valve. Regarding ventilation, consideration was given so that the disinfected air was uniformly dispersed from the bottom of the tank to the entire sugar solution. The stirrer is necessary when the raw materials used tend to settle or when the viscosity of the liquor increases. Recently, mechanical agitation is often omitted, since it is limited to the agitation effect caused by aeration. That is, if the ventilation method is appropriate, the stirring device may not necessarily be attached. Of the various conditions, the most important is temperature control during culture, but generally the temperature of the fermentation broth is controlled near the optimum temperature of the yeast used. The optimum temperature of yeast is 3 excluding special ones.
It is 0 to 32 ° C. It is desirable to install a heater and a cooler as the temperature control device, or to attach a device that has both functions, but except for cold regions, generally only a combination of a temperature sensor and a cooling device, especially a heating device is attached. It has not been. In other words, fermentation is a type of exothermic reaction, and under normal conditions, the temperature of the fermentation liquor rises to a temperature above the permissible range for yeast growth. This is because the heater is not necessarily required except for the ground. A cooling capacity that can control the temperature within an allowable range even with the maximum heat generation is sufficient. If the temperature rises abnormally due to the heat of fermentation and exceeds the control temperature range, the yeast is damaged and the subsequent fermentation is adversely affected. Cultivation of the mother of liquor after inoculation with yeast is carried out at 30 to 32 ° C. for 24 to 48 hours while continuously aerated at 0.025 to 0.050 VVM for 24 hours. After this, the liquor after culturing is added to the main mash prepared in advance and fermented to generate alcohol. Determine by considering the growth process.

[0008] This mash is prepared by pouring the raw material into the main fermentation tank of 2 in Fig. 1 and adding water so that the sugar concentration becomes a predetermined value, similar to the sake mash. The sugar concentration of this mash is about 15 to 25%, but it is better to adjust it according to the number of yeasts in the liquor used, and the target is 0.06 per 1 × 10 ⁸ live yeast in consideration of contamination by various bacteria. It is desirable to prepare so that the amount of sugar is about 0.16 g. Since this is the goal to finish one batch of repetition within 24 hours, the sugar amount relative to the number of yeasts must be set to a small value in order to ripen in a shorter time and move to the next cycle. . The cycle time of one batch of the present invention is set to 24 hours, which includes the preparation time and fermentation time at the time of switching, and this is desirable when considering the production system in the actual factory. Further, as a method of controlling the number of yeasts in the main mash, there is a method of changing the amount of liquor added to the main mash, that is, the amount of liquor used. Regarding yeast, there are times when it is in an aerobic respiration state and when it is in an anaerobic fermentation state, so it is necessary to consider it in fermentation management. The difference between the two states is slight, but it appears as a delay or shortening of the fermentation time. With repeated batch fermentation, the number of yeasts gradually increases with each cycle as compared with the case of liquor mother. In the present invention, a method of increasing the sugar concentration by 1 to 3% for each batch is adopted in accordance with the pace of increase in the number of yeasts, and within the range of the amount of sugars relative to the number of yeasts. Then, when the number of yeasts reaches almost the maximum value, considering the alcohol tolerance of the strain, the charged sugar concentration is set to the upper limit value at which repeated batch fermentation can be continued, and thereafter, the charging and fermentation under the conditions are repeated. During this period, stirring is continuously performed and stopped only when the yeast is settled at the time of switching and the supernatant is drawn out. On the other hand, the aeration may be changed a little while observing the yeast condition, but it is sufficient to carry out the aeration at 0.025 VVM for 1 to 4 hours.
However, if too much yeast metabolizes the respiratory system,
The so-called "sugar eating phenomenon" appears, and the result is that the fermentation rate of alcohol does not increase despite the consumption of sugar, so it is desirable to reduce the aeration rate a little when the number of yeasts increases. It should be noted that the upper limit of the concentration of sugar charged in the repeated batch fermentation method is naturally determined by the alcohol resistance of the strain used, and therefore it is necessary to carry out a confirmation test in advance. The structure and material of the main fermentation tank are basically the same as those of the liquor culture tank, but in principle, continuous aeration is performed only in the first batch in the main fermentation process of the present invention, so a stirring effect due to aeration cannot be expected. Considering the second and subsequent batches, it is better to have a stirrer. Even in static fermentation without stirring, fermentation will proceed but the end time will be delayed. Particularly, in the case of a flocculating yeast, stirring is necessary, and the effect cannot be neglected. Considering the yeast used and the shape of the main fermentation tank, it is necessary to select the most suitable stirring device and determine the operating conditions during operation. In the repeated batch fermentation, the ripened mash is extracted for each batch. However, it is desirable to extract the ripened mash from the side and bottom of the tank depending on the yeast used, that is, the aggregating yeast and the non-aggregating yeast. Further, when a flocculating yeast is used, it is desirable to install a sight glass so that a 20 to 30% volume of the liquor settled portion left as the liquor of the next batch can be observed. In addition to observing the agglutination state, color, sedimentation property, etc. of yeast, the vitality and total number of yeast can be estimated visually.

As the yeast to be used, a flocculating yeast which does not require a centrifuge is desirable, but a non-flocculating yeast is also provided with a centrifuge to recover the yeast at the end of each batch and return it to the main fermentation tank. By adopting a method of reuse by recycling, batch fermentation can be continued for a long period of time. In short, in order to repeat the batch fermentation as many times as possible and maintain a stable and good fermentation state for a long period of time, how to keep the yeast activity and the viable cell ratio high is an important point. When using natural raw materials, it is often the case that reproducibility of the fermentation process cannot be obtained mainly due to variations in medium composition. It is known that many other factors such as temperature, pH, aeration and stirring are also involved. Therefore, in the rapid batch fermentation method such as the present method, it is required to detect the end of fermentation early and shift to the next batch promptly. In consideration of such circumstances, we devised to detect the end of fermentation as soon as possible by measuring the flow rate of fermentation exhaust gas containing CO ₂ as a main component,
It is a method of the present invention to shift to a switching operation. A French patent (Patent No. 260651)
As proposed in 4), this French patent merely uses carbon dioxide flow measurement to predict progress and development in batch fermentation of wine, and to control and control fermentation.

Therefore, this French patent has a different purpose from the method of measuring the flow rate of fermentation exhaust gas for predicting the time until the end of fermentation of each cycle and detecting the end of fermentation in the repeated batch fermentation method of the present invention. ing. The present invention
Is the difference between the total pressure of the fluid in the pipe and the static pressure, that is, the dynamic pressure.
Know the flow velocity by and then find the flow velocity and the cross section of the pipe
A gas flow meter that calculates the flow rate from the product
Gas flow meter that measures the head of water
Management Technology Lecture "Institute of Pollution Resources, Institute of Industrial Technology, Thermal Management Technology Course
Pp. 175-182) edited by Yoshiyoshi Editorial Committee (Maruzen)
Specifically, the fermentation exhaust gas from the fermenter is used.
The velocity head of the fermentation exhaust gas is measured at the exhaust port or exhaust pipe.
Insert a Pitot tube which is one of the gas flow meters of the
Measure the total pressure and static pressure, find the dynamic pressure from the difference,
The gas flow rate Q is calculated from the following equation shown in Table 1 below.

[0011]

[Table 1]

An annubar flow meter may be used instead of the Pitot tube. The flow rate thus measured is recorded with time or continuously immediately after the start of fermentation. Then, the time from the drawn curve or the decrease value of the speed per unit time to the end of fermentation can be predicted. Furthermore, if the measurement is continued as it is, the gas flow rate will approach zero, so by determining the end of fermentation by the gas flow rate value beforehand, even those who are not familiar with the method of fermentation management can easily, quickly and accurately The end of fermentation can be detected. In order to almost complete the alcohol fermentation and to minimize the influence of the produced high-concentration alcohol on the yeast itself, the fermentation exhaust gas flow rate is 0.1 to 0.3 m ³ / k.
It is appropriate to consider the end of fermentation when the time reaches l · hr and start the switching operation. However, when a strain with strong alcohol tolerance is used or when fermentation is carried out at a relatively low sugar concentration, fermentation may be continued to a lower flow rate. It is also an effective method to determine whether to continue the fermentation or to interrupt and switch the fermentation by observing the flow rate of the fermentation exhaust gas immediately before the end of the fermentation and determining whether or not the curve shows the boat bottom type. In other words, the phenomenon that the vitality of yeast is reduced due to the influence of alcohol and salts produced in the fermentation liquor and the flow rate of fermentation exhaust gas rapidly decreases during fermentation, and then a slight amount of fermentation exhaust gas flows out for a long time is observed. However, if the fermentation of the batch is not continued for a long time, and conversely before this phenomenon appears, the fermentation time may be slightly extended. However, in the case of the final batch, the same yeast is not used any more, and thus the fermentation can be continued even if the same phenomenon appears. If the measurement range of the Pitot tube is inappropriate, a method of changing the diameter of the fermentation exhaust gas tube or using a plurality of exhaust gas tubes having different diameters may be adopted. The output of the fermentation exhaust gas flow rate and the equipment used at the time of cycle switching, such as an agitator, a timer, an automatic valve, and an input of a pump, etc., can be automated in a sequence by incorporating them in a sequence in the control device.

In the case of repeated batch fermentation, there is a great feature that it is not necessary to prepare the mother liquor every time the main mash is charged. However, if there is a delay in the switching operation, the yeast itself is generally damaged by the produced alcohol, and both the viable cell count and the viable cell rate of the yeast are generally lowered. Also,
On the contrary, even if a new sugar solution is added, the growth of various bacteria becomes active, and even if aeration is performed for activation, the production amount of alcohol and the fermentation rate gradually decrease. According to the present invention, it is possible to accurately determine the switching time, which is extremely important in carrying out the repeated batch fermentation method, so that fermentation management becomes easy. Furthermore, if a sugar solution is prepared so that the amount of sugar is less than a certain amount relative to the number of live yeast, that is, if the concentration of sugar to be fed is changed stepwise so that it is not unreasonable for yeast, stable batch fermentation with good alcohol productivity can be achieved. The law can continue for a long time. Further, if the switching operation is automated, it is possible to save a lot of labor.

The present invention will be further described below with reference to examples and comparative examples.

[0015]

[Example 1]

Raw sugar was added to a liquor tank so that the sugar concentration was 16%, and 0.25% of ammonium sulphate was added to prepare liquor. After sterilization and cooling, pre-cultured aggregating yeast Saccharomyces cerevisiae
Sterilely inoculated with ATCC 26603 strain and kept at 32 ° C for 24 hours
Incubated for hours. During this period, continuous ventilation was performed at 0.025 VVM. The sugar concentration charged in the first batch of the main mash was 16.3%, and ammonium sulfate was added at 0.02%. Sake mother was added to this to start the main fermentation. Aeration is 0.025VV after addition of liquor
M was continuously applied for 24 hours, and stirring was similarly continued for 24 hours. Ventilation after the 2nd batch is 0.05VV after switching
Only 2 hours on M. In addition, the sugar concentration was set as low as 17.3% in the second batch in consideration of the number of yeasts. However, the target for the third batch was 20% and the target for the fourth to twelfth batches was 22% although it varied somewhat, and a total of 12 cycles were performed. The flow rate of fermentation exhaust gas is L-type Pitot tube and Dustuck sampler ES
-302ET (manufactured by Okano Seisakusho) was used for continuous measurement, and the end of fermentation of each batch was set to 0.3 m ³ / kl · hr. After the fermentation was completed, the stirring was stopped, the yeast was allowed to settle, the supernatant was withdrawn, and a new sugar solution was added to transfer to the next batch.

The results are shown in FIG. 2, and the flow rate of the fermentation exhaust gas at that time is shown in FIG. From the 4th to 5th batches, the decrease curve of the exhaust gas flow rate became steep, indicating that the fermentation process was good. In such a case, it becomes easy to judge the end of fermentation by the gas flow meter.

[0018]

[Comparative Example 1]

For the purpose of comparison with the present invention, a fermentation test was carried out by the conventional method of addition (batch method). For sake mother, non-aggregating yeast Saccharomyces cere
It prepared like Example 1 using visiae strain 396 (IFO 0216). The sugar concentration is 16
Approximately 17% was added as a target, and from about 20 hours after the addition of liquor, the additive containing sugar of about 42% was added over about 20 hours. 3% and 33% by volume of the added amount of liquor and soy sauce, respectively.
Is. Ammonium sulfate was added in an amount of 0.02% to sugar, and both aeration and stirring were carried out for 3 hours after the addition of liquor (aeration amount was 0.05 VVM). Table 2 shows the results of analysis of the fermented liquid fermented at 32 ° C. Since the fermentation is completed as much as possible, the fermentation rate is slightly higher than that in Example 1. However, considering that the number of fermentation days is at least 4 days, the efficiency, that is, the alcohol productivity (g / l · hr) is about 1/4 of the result of Example 1.
In addition, this batch-type addition method requires preparation of liquor and soy sauce each time. When the fermentation exhaust gas flow rate course measured by the same method as in Example 1 is averaged, it becomes as shown in FIG.
It can be seen that the fermentation process is slower than in Example 1, and the amount of gas generated in the latter half is small but lasts for a long time. Therefore, it is difficult to determine the end of fermentation by the flow rate of fermentation exhaust gas as in the present invention.

[0020]

[Table 2]

[0021]

Example 2

Liquor is the non-aggregating yeast Saccharomy
ces cerevisiae 396 strain (IFO 0
216) was used and prepared similarly to Example 1. The preparation of this mash was basically performed in the same manner as in Example 1. However, the sugar concentration is 17% for the first batch, the second batch, 20% for the third batch to the sixth batch, and 21% for the seventh batch.
22% was continued from the batch number to the 17th batch. The yeast was collected by a centrifuge under the conditions of 1400 G for 2 minutes, and the sedimented product was added to the next batch as liquor mother every time. The recovered amount of cells in the final batch was about 50 g / l (wet weight). The results are shown in FIG. 5, and part of the flow rate of the fermentation exhaust gas measured by the same method as in Example 1 is shown in FIG. As can be seen from this, even in the non-aggregating yeast, the effect of the present invention can be obtained by introducing the centrifugal separator, as in the case of the aggregating yeast shown in Example 1.

[Brief description of drawings]

FIG. 1 is a process flow diagram for carrying out alcoholic fermentation using a flocculating yeast in the present invention. 1: Liquor tank, 2: Main fermentation tank, 3: Scrubber, 4: Liquor transfer pump, 5: Aging mash extraction pump, 6: Stirrer, 7: Flow meter sensor, 8: Aeration line, 9: Raw material supply line

FIG. 2 is a graph showing a fermentation process in Example 1.

FIG. 3 is a graph showing the flow rate of fermentation exhaust gas in the second, third, fourth, fifth, eighth, and twelfth batches of Example 1.

FIG. 4 is a graph showing the progress of the alcohol fermentation exhaust gas flow rate by the adding method of Comparative Example 1.

FIG. 5 is a graph showing a fermentation process in Example 2.

FIG. 6 is a graph showing the flow rate of fermentation exhaust gas in the 5th, 10th, and 16th batches of Example 2.

Claims (2)

[Claims] 1. A method for producing alcohol by a repeated batch fermentation method using a sugar raw material or a starch raw material, characterized in that the end of fermentation is predicted or determined by a gas flow meter of a method of measuring a velocity head. Alcohol production method. 2. The fermentation is judged to be completed when the flow rate of the fermentation exhaust gas is 0.35 to 0.1 m ³ or less per hour for 1 kl of the fermentation broth or when the flow rate of fermentation flue gas is equal to or less than that. The method for producing alcohol according to the item.