JPH04179488A - Continuous method for fermenting alcohol using agglutinative microorganism - Google Patents

Abstract

PURPOSE:To enable stable continuous operation for a long period while keeping microbial cells in a fermenter at a high concentration and carry out alcoholic fermentation with excellent productivity by fermenting saccharides according to a fermentation method in specific two stages using an agglutinative microorganism. CONSTITUTION:An agglutinative microorganism is used as an alcoholic fermentative microorganism to continuously produce alcohol from saccharides. In the process, the agglutinative microorganism having high fermentation activity is continuously cultured in a stirred type microbial cell growth vessel having an oxygen feeder and a microbial cell separator, and the aforementioned microorganism is then fed from the above-mentioned microbial cell growth vessel to a fermenter for continuously producing the alcohol at a high concentration to carry out fermentation of the saccharides.

Description

[Detailed description of the invention] (Industrial application field) This invention ferments sugar using microorganisms that flocculate sugar.

This invention relates to a method for continuously producing alcohol.

(Problems to be solved by conventional techniques and inventions) Generally,
When continuous fermentation of alcohol from saccharides is performed, fermentation microorganisms are inhibited from fermentation and growth by the produced alcohol, resulting in a decrease in the viable rate and fermentation activity in the fermenter. In addition, in an environment with high alcohol concentration, the fermentation activity of bacterial cells decreases, making it necessary to maintain the alcohol concentration in the fermenter at a low level, and a large amount of energy is required for concentration and separation in the subsequent process. shall be.

Conventionally, it has been difficult to maintain, for example, an ethanol concentration of 70 g/ρ or higher and to operate stably and continuously for a long period of time.

Various methods and devices have been proposed to solve the above drawbacks. In other words, in order to increase the fermentation productivity of alcohol, it is necessary to increase the bacterial cell concentration in the fermenter, and one way to achieve this is to use immobilized yeast ("Alcohol Handbook", Hakko Kogyo Foundation). Published by the Association (March 15, 1986), No. 146-14
(page 7), a method of supporting bacterial cells (Zaiyo "Alcohol Handbook" pages 149-150), a method of recovering bacterial cells from fermentation mash by centrifugation etc. and returning them to the fermenter (
``Alcohol Handbook,'' page 146) has been proposed. However, these methods have problems such as high cost of the carrier and deterioration of the carrier itself. Further, there was a problem that the mechanical cost and operating cost of the centrifugal separator were high.

On the other hand, there is a method in which flocculating yeast is used, and a sedimentation separation tank is installed in a tower-type fermenter, and these are arranged in two stages in series to produce fermentation (Zuyang "Alcohol Handbook", pages 150-151).
J, FERMENT, BIOENG,.

Vol, 69. No. 1.39-45.1990) has been proposed, but in a tower-type fermenter, if the bacterial cell concentration increases, stirring in the fermenter becomes insufficient, resulting in one-sided flow, etc., and the fermentation yield decreases. was there. In addition, there were problems such as the formation of aggregates of bacterial cells, which caused blockage of the liquid feeding line.

(Means for Solving the Problems) As a result of various studies in order to solve these problems, the present inventors found that a method for maintaining a high bacterial cell concentration in a fermenter was to use flocculating microorganisms to produce sugars. The alcohol fermentation method is carried out in two stages. In the first stage, a stirred bacterial growth tank equipped with an oxygen supply device and a sedimentation device for separating and concentrating bacterial cells is used to increase the number of flocculating microorganisms. Fermentation activity can be increased by continuous culturing at a high concentration, and by adopting a sedimentation separation device for bacterial cell separation and concentration from this growth tank to the second stage fermenter that essentially continuously produces narcol. It is possible to continuously supply a high concentration of microorganisms, maintain a high bacterial cell concentration in the second stage fermenter, and maintain a high alcohol concentration while allowing stable continuous operation over a long period of time, overcoming the above problems. Based on this knowledge, the present invention was made.

That is, this invention continuously produces alcohol from sugars using coagulating microorganisms as alcohol fermenting microorganisms, and the method is carried out in at least two stages, and the first stage is equipped with an oxygen supply device and a bacterial cell separation device. A flocculent microorganism with essentially high fermentation activity is continuously cultivated in a stirred type bacterial growth tank, and the microorganism is supplied from this fermenter to a second stage fermenter that continuously produces essentially high concentration alcohol. The present invention relates to a continuous fermentation production method for alcohol, which is characterized by:

In this method, the flocculating microorganism used for alcohol fermentation is yeast or bacteria whose cell concentration can be concentrated using a sedimentation separator. As such microorganisms, microorganisms whose cell growth is particularly promoted under aerobic conditions are preferable. For example, Saccharomyces cer
A flocculating yeast of the genus Evisiae is used.

By using this flocculating microorganism, it is easy and inexpensive to maintain a high bacterial cell concentration, and the cost of bacterial cell proliferation can be reduced. Furthermore, it becomes possible to effectively utilize bacterial cells in alcohol fermentation. On the other hand, if the fermentation is not flocculating, the bacteria will accompany the fermentation process and flow out of the fermenter, causing problems such as not only the bacteria will not be utilized, but also the concentration of bacteria will be low (and the volume of the fermenter will increase).

In the method of the present invention, sugars such as glucose, shakerose, fructose, xylose, galactose, theobiose, starch saccharification liquid, molasses, sugar cane or sugar beet juice are supplied to the fermenter.

In the method of this invention, the optimal oxygen supply conditions to the bacterial growth tank in the first stage are determined depending on the type of bacterial cells;
1500 mol/m”-hr, preferably 50-1
It is desirable to supply in the range of 000 a+ol/m"・hr. When supplying air or air containing high concentration oxygen, supply air containing an amount of oxygen comparable to the respective oxygen supply rate. The amount of oxygen supplied to the stage is preferably in the range of 0 to 300 IIIO1/I!13.hr; in this case, alcoholic fermentation does not require much oxygen, so it can be lower than that in a growth tank, and depending on the microorganism, it may even be zero.

In the method of the present invention, a nutrient solution necessary for cell growth, such as yeast extract, malt extract, polypeptone, etc., can be added to the first-stage growth tank and the second-stage fermentation tank.

In the method of the present invention, it is preferable that the first stage growth tank is equipped with a gas dispersion device for supplying oxygen.

In the method of this invention, the first-stage growth tank is equipped with a stirring blade to sufficiently stir the highly concentrated bacterial cells and sugars. The stirring blade may be of any type as long as it can sufficiently stir the inside of the fermenter, but it is preferable to use propellers, ribbon blades, or other blades with a small shearing force. This is because if the shear force is large, it will have an adverse effect on the flocculation performance of the bacterial cells, and the sedimentation of the bacterial cells may become insufficient in the bacterial sedimentation separation tank, making it impossible to maintain a high bacterial cell concentration.

In the method of the present invention, the fermenter in the second stage is not necessarily a stirring tank, but a basic fermenter can be used, but a device for mixing inside the fermenter is required. For example, an air lift fermenter is used. It is preferable to use a stirring type fermenter in order to appropriately control the mixing state.

The bacterial cell sedimentation separation device used in the first and second stage propagation tanks and fermentation tanks may be installed inside or outside the tank, but the bacterial cell concentration in either tank is 10 g/I2 or more as body weight, preferably 50 to 120
g#! It is desirable to maintain the

Further, part or all of the effluent from which bacterial cells have been separated by the sedimentation separation device of the first growth tank can be sent to the second stage fermentor or product line. Also, if the effluent contains almost no sugar and alcohol, it may be discarded.

On the other hand, part or all of the isolated bacterial cells from the first-stage propagation tank is sent to the second-stage fermentation tank, and the remaining part is returned to the first-stage multiplication tank.

In the method of this invention, a first stage growth tank and a second stage growth tank are provided.
It is possible to independently change the content concentration and rate of saccharides fed to the fermenters of each stage, and the feed concentration of the growth tank is preferably 1 to 20%.

The sugar content concentration supplied to the second stage fermenter is preferably 20% or more, more preferably 20 to 50%.

Further, the residual sugar concentration in the first stage tank is preferably 50 g/
1 or less, more preferably 10 g/l or less, and the residual sugar concentration in the second stage fermenter is preferably 10 g/ρ or less. If this concentration is high, carbon dioxide gas generated during fermentation in the sedimentation separator will not only cause insufficient sedimentation and separation of bacterial cells, causing a decrease in the concentration of bacterial cells in the fermenter, but also cause unfermented sugars to flow out. The fermentation yield of alcohol also decreases due to the increase in alcohol.

In this invention, it is preferable that the alcohol concentration in the first stage growth tank is 70 g/ρ or less.

If it exceeds 70 g/l, the alcohol will inhibit the growth of the bacteria, which will not only kill the bacteria and reduce the bacterial cell concentration, but also inhibit alcohol fermentation and reduce the fermentation rate. The alcohol concentration is 70
Ferment to g/I2 or more, preferably 80 to 150 g/I2.

The fermentation temperature is determined depending on the type of bacteria, but is usually 15 to 65°C, preferably 25 to 40°C.

In the method of the invention, an alcohol recovery device, such as a condenser or a scrubber, can also be provided to recover alcohol in the fermentation exhaust gas from the fermenter.

Next, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 is a flow sheet showing an embodiment of the present invention, in which saccharide is supplied from line 4, and oxygen or air is supplied from line 5 to the stirring type bacterial growth tank 1 at the first stage.

The flocculating microorganisms used for alcohol fermentation are more likely to grow under aerobic conditions. Nutrient liquid necessary for bacterial growth can also be added from line 4 and line 13.

The stirring type bacterial cell growth tank 1 is equipped with a gas dispersion device for supplying oxygen, and is also equipped with a stirring blade for sufficiently stirring highly concentrated bacterial cells and sugars. The shape of the stirring blade is preferably one with a small shearing force, such as a propeller or a ribbon blade. The fermentation liquid in the stirring type bacterial growth tank 1 is transferred to the line 22 (separation tank 3 inside the fermentation tank).
line 22 and line 23 are not necessary if
is sent to sedimentation separation tank 3.

Further, the effluent separated by the sedimentation separator 3 of the propagation tank passes through line 8, and part or all of it is sent to the second stage alcohol fermenter 2 or via line 9 to line 11.

If the effluent contains almost no sugar or alcohol, it is sent to line 10 via line 9 and discharged.

On the other hand, the precipitated and separated bacterial cells pass through line 6, a necessary amount is sent to alcohol fermentation tank 2 through line 7, and the remaining part is returned to bacterial cell growth tank 1.

Further, the fermentation gas is discharged through the line 16 of the propagation tank 1 and the line 20 of the sedimentation tank 3. The alcohol contained in the fermentation gas is transferred to a line 25 by an alcohol recovery device 24.
The fermentation gas is discharged through line 26.

As the second stage fermenter 2, for example, an air lift type fermenter is used. Furthermore, the fermentation gas discharged from the line 14 in the fermenter 2 can be circulated back to the fermenter 2 via the line 15.12 to obtain a stirring effect. Preferably, a stirring tank type fermenter can be used to appropriately control the mixing state. Alcoholic fermentation gas is discharged through line 14 and line 21.

The alcohol fermentation finished liquid passes through line 23 to settling tank 3
3, the bacterial cells are separated, and the liquid containing the bacterial cells is returned to the fermenter 2 through line 17. Note that, if necessary, it is possible to pull out the bacterial cells through the line 18, and the extracted bacterial cells can be sent to the bacterial cell growth tank 1 through the line 19.

The bacterial cell sedimentation separation layer 33 may be provided inside the fermenter or outside the fermenter. Furthermore, the concentration and/or supply rate of saccharides can be changed independently to the growth tank 1 and the fermentation tank 2. Further, the sugar content concentration supplied from the line 13 to the alcohol fermenter 2 is preferably 20% or more.

Furthermore, the sugar concentration in the bacterial growth tank 1 and the alcohol fermentation tank 2 is operated at 50 g/ρ or less, preferably 10 g/12 or less.

(Examples) Next, the method of the present invention will be specifically explained using Examples and Comparative Examples.

Example 1 As the sugar, Philippine molasses containing 56.6% fermentable sugar was used. The composition of the fermentation culture solution is ammonium sulfate 3g/Q as a nutrient source and Adekanol LG2 as an antifoaming agent.
94 (trade name) was set at 0.1 ml/°C. The sugar composition is
The above molasses was diluted with water to give a sugar concentration of 80 g/42.300 g/l for the bacterial cell growth tank and the alcohol fermenter, respectively.

These fermentation media were sterilized at 120°C for 10 minutes and then supplied to each fermenter.

Saccharomyces cer as an agglutinating microorganism
Ethanol fermentation was performed using Evisiae IR-2 according to FIG. The flocculating microorganisms are subjected to a preculture in a conventional manner before being introduced into the method according to the invention.

A molasses medium containing a sugar concentration of 80 g/l was introduced into the bacterial growth tank 1 through line 4 at a flow rate of 0.187 h-' dilution rate. At that time, the inoculation amount was 10% of the fermenter. Oxygen supply was performed by bubbling air into the growth tank. The oxygen supply rate was 140 mol/m"・hr. The stirring blade was a propeller type, and the rotation speed was 20 Orpm. The fermentation temperature was 30°C, and the pH at that time was 4.75.
It was maintained at ~4.8.

At this time, the bacterial cell concentration in the growth tank 1 is 120g dry weight.
/l, alcohol concentration is 48g/ρ, residual sugar concentration is 0.1
g/l. This fermentation liquor was introduced into the sedimentation separator 3, and the entire amount of this effluent was introduced into the alcohol fermenter 2. At this time, the bacterial cell concentration in the effluent was 13 g/ρ. In addition. The entire amount of isolated bacterial cells was returned to bacterial cell growth tank 1.

On the other hand, a molasses medium with a sugar concentration of 300 g/I2 was supplied to the alcohol fermenter 2 at a dilution rate of 0.075 h-', and oxygen was supplied using air at a supply rate of 22.3 mol/ms·hr. The stirring blade was a propeller type, and the rotation speed was 1100 rpm. The fermentation temperature was 30°C. The pH at this time was 4.
It was kept at 75-4.8. Alcohol fermenter 2 at this time
The bacterial cell concentration within the tank was maintained at a high level of 90 to 100 g/l, and the alcohol concentration was maintained at a high concentration of 80 g/ρ. Residual sugar concentration is 2g/l
It became below. In addition, the dilution rate with respect to the total fermenter volume in this test was 0.118 h-'. Under the above operating conditions, stable continuous operation for more than 500 hours was possible.

Comparative Example 1 An alcohol fermentation test was carried out using only one tank using alcohol fermenter 2. As the fermentation medium, the same molasses medium as in Example 1 was used. The sugar concentration was t80 g/l, and the dilution rate was adjusted to the dilution rate for the total fermenter volume in Example 1. Other fermentor conditions were the same as in Example 1.

As a result, the bacterial cell concentration in the fermenter gradually decreased to 30%.
g/4, the alcohol concentration also decreased, and stable operation was not possible.

Also, assuming a sugar concentration of 300 g/l, the dilution rate is 0.05 h-1.
Similarly, when fermentation was carried out in only one tank, the residual sugar concentration was 10
Since the concentration exceeded 0 g/l, sedimentation separation was difficult and stable operation was not possible.

(Effects of the Invention) According to the present invention, flocculating microorganisms are cultured and multiplied at high density under optimal conditions in the first-stage bacterial growth tank, the tank capacity is reduced, and the second-stage fermentation tank It has an excellent effect of being able to achieve alcoholic fermentation with high bacterial cell concentration, high sugar concentration, and high alcohol concentration. Specifically, with this invention, the bacterial cell concentration in the alcohol fermenter can be reduced to 90-100g/I2, and the alcohol concentration can be reduced to 80g74.
I was able to hold more than that. The residual sugar concentration was 2 g/I2 or less, and the fermentation yield was improved. Under these fermentation conditions and the above operating conditions, stable continuous operation for more than 500 hours was possible.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing one embodiment of the method of the present invention. 1... Bacteria growth tank 2, alcohol fermentation tank 3.33... Separation tanks 4-23... Line 24... Alcohol recovery device 25.26... Line

Claims (1)

[Scope of Claims] (1) In the continuous production of alcohol from sugars using coagulating microorganisms as alcohol-fermenting microorganisms, the method is carried out in at least two stages, and in the first stage an oxygen supply device and bacterial cells are used. A fermenter in which flocculating microorganisms with essentially high fermentation activity are continuously cultured in a stirring type bacterial growth tank equipped with a separation device, and a second stage of essentially highly concentrated alcohol is continuously produced from this fermenter. A continuous fermentation production method for alcohol characterized by supplying microorganisms to. (2) Oxygen supply rate to the first stage bacterial growth tank is 1 to 1.
500mol/m^3. 2. The method of claim 1, wherein the method is provided as a range of hr. (3) The method according to claim 1 or 2, wherein the bacterial cell concentration in the fermenter is maintained at 10 g/l or more. (4) The method according to claim 1, 2, or 3, wherein the first-stage growth tank and the second-stage fermenter can each independently change the concentration and rate of saccharide to be supplied. (5) The concentration of sugars supplied to the second stage fermenter is 2
5. The method according to claim 4, wherein the amount is 0% or more. (6) The production method according to claim 1, 2, 3 or 4, wherein the production method is operated at a residual sugar concentration in the first stage and second stage growth tanks and fermentation tanks of 50 g/l or less.