JPS6136918B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for continuous production of alcohol by fermentation.

In recent years, fermented alcohol, which can be obtained without using petrochemicals, has been in the spotlight as an energy alternative to petroleum. It is produced from sugar cane, molasses harvested from sugar cane, cellulose or starch from sweet potatoes, potatoes, corn, etc., and ferments them through the action of bacterial cells. In this method, alcohol productivity is thought to depend on the bacterial cell concentration. Therefore, in order to increase the bacterial cell concentration, a method of circulating the bacterial cells and a so-called immobilized cell growth method in which yeast is encapsulated in a polysaccharide-based substance are being developed. However, in the former case, the centrifugal separator used to concentrate and separate the microbial cells becomes clogged or nozzles clogged by the solids present in the culture solution, making it increasingly difficult to circulate the microbial cells. Therefore, it is necessary to periodically clean the centrifuge, which makes the work extremely troublesome. In the latter case, for mass production on an industrial scale,
There are many problems that are technically difficult to solve.

In view of these circumstances, the present inventors have conducted extensive research to increase the bacterial cell concentration within the fermenter, and as a result, have completed the present invention.

The method for producing alcohol according to this invention is characterized by arranging two fluidized bed fermentation devices in series, culturing bacteria with alcohol fermentation ability attached to a carrier in the first stage, and culturing immobilized yeast in the second stage. This is a continuous method for producing alcohol by fermentation.

The reason why a fluidized bed type is used as the two fermentation beds, front and rear, is that the power needed to fluidize the bacterial cells adhering to the carrier can be saved and wear of the carrier can be prevented.

In the first stage, crushed vermiculite, activated carbon, zeolite, etc. are preferably used as the carrier for bacterial cell attachment from the viewpoint of fluidity of the carrier. As the bacteria having alcohol fermentation ability, Zymomonas mobilis is preferably used because it has excellent natural adhesion to the carrier.
This bacterium produces alcohol by fermenting sucrose, glucose, and fructose, among the fermentable sugars contained in cane and blackstrap molasses. Bacteria having alcohol fermentation ability are not limited to the above-mentioned bacteria as long as they have good natural adhesion. By culturing the microbial cells attached to the carrier in the first stage, the concentration of microbial cells in the tank can be increased and the productivity of alcohol from the fermentable sugar can be improved.

In the latter stage, the immobilized yeast may be any yeast having alcohol fermentation ability, and yeast of the genus Saccharomyces is particularly preferably used. Immobilized yeast is one that is immobilized by enclosing yeast in polyacrylamide gel, sodium alginate, K. carrageenan, etc. using a conventional method. By culturing the immobilized yeast in the latter stage, unreacted fermentable sugars that were not fermented in the first stage are fermented to produce alcohol and improve the alcohol fermentation yield from sugar. be able to.

Since the alcohol production method according to the present invention is configured as described above, the following effects are achieved.

(1) Since both the front and rear fermenters are of the fluidized bed type, the power needed to fluidize the bacterial cells attached to the carrier can be saved, and the abrasion of the carrier and crushing of the immobilized yeast can be prevented. can.

(2) In the first stage, a carrier is used to attach the bacterial cells, so the solid surface area on which the bacterial cells can attach can be increased, and the concentration of bacterial cells in the tank can be increased.As a result, alcohol productivity can be increased. can be significantly improved.

(3) Since immobilized yeast is cultured in the latter stage, the unreacted fermentable sugars that were not fermented in the first stage can be fermented by the yeast, and as a result, the fermentation yield can be significantly improved.

(4) Highly clear materials are not required as fermentation raw materials.

Comparative Example 1 Using a fermenter for static culture, Saccharomyces hormocensis was grown as a microorganism.
Formosensis) IFO Deposit No. 0216 (hereinafter referred to as microorganism A) was used as a fermentation raw material.
Double diluted Cane's molasses medium (yeast extract: 3g/
, (NH ₄ ) ₂ SO ₄ : 1 g/, KH ₂ PO ₄ : 1 g/ and MgCl ₂ 6H ₂ O: 0.5 g/),
Batch fermentation was carried out at a fermentation temperature of 30°C, and the fermentation characteristics were investigated over time.

Instead of the above microorganisms, baker's yeast manufactured by Kyowa Hakko Co., Ltd. (hereinafter referred to as microorganism B), Zymomonas mobilis IFO deposited No. 13756 (hereinafter referred to as microorganism C), and Zymomonas mobilis ATCC deposited No. 10988 (hereinafter referred to as microorganism The above operation was repeated using each sample (referred to as D).

Figure 1 shows the relationship between static culture time and ethanol concentration for each microorganism. As can be seen from the figure, microorganism A has the best alcohol fermentation ability (approximately 55 g/on the second day), followed by microorganism B, and microorganisms C and D have the highest alcohol fermentation ability even on the fourth day.
The alcohol concentration was only about 40g/.

Comparative Example 2 One alcohol fermentation apparatus shown in FIG. 4 was used. This main body is a glass fluidized bed type fermenter 11 with an actual volume of 0.7, and is configured to be able to control temperature and pH. The fermentation raw material is supplied to the bottom of the tank 11 by the pump 12, and the reaction solution is returned from the top to the bottom of the tank by the pump 13, and flows out from the carrier settling section 14 at the top of the tank. Immobilized yeast Saccharomyces formosensis encased in sodium alginate in this fermentation apparatus IFO Deposit No. 0216
The same sterilized 5-fold diluted Cane's molasses medium used in Comparative Example 1 as the fermentation raw material was filled at a flow rate of 0.035.
The mixture was continuously supplied to the fermenter 11 at a rate of 30° C./h, and continuous fermentation was carried out under the fermentation conditions of a temperature of 30° C. and a pH of 5.

The ethanol concentration in the effluent reaction solution after the reaction was approximately the same as in the case of batch fermentation (Comparative Example 1), about 55
It was g/.

Example A continuous alcohol fermentation apparatus shown in FIG. 2 was used. It consists of two glass fluidized bed fermentation tanks 1 and 2 arranged in series with an actual volume of 0.7,
These tanks 1 and 2 are constructed so that the temperature and pH can be controlled to optimum values. The fermentation raw material is supplied to the first stage tank 1 by the pump 3, circulated in the same tank 1 by the pump 4, then the reaction liquid is sent from the first stage tank 1 to the second stage tank 2 by the pump 5, and the same tank is circulated by the pump 6. 2 can be circulated.

A medium consisting of glucose 100 g/ yeast extract 3 g/ KH ₂ PO ₄ 1 g/ (NH ₄ ) ₂ SO ₄ 1 g/ MgCl ₂ 6H ₂ O 0.5 g/ anti-packaging agent (manufactured by Toshiba Silicon Co., Ltd.) 0.3 g/ 400ml in front tank 1, 600ml in rear tank 2
ml each, and then heat-treated crushed vermiculite (60 to 80 mesh) was added to the pre-stage tank 1 at a concentration of 5 wt/vol%, and the medium was heat sterilized.
Zymomonas was then cultured using the above medium.
100 ml of culture solution of Mobilis ATCC Deposit No. 10988 was added to the first tank 1. In addition, the immobilized yeast Saccharomyces formosensis encased in sodium alginate was deposited at IFO.
No. 0216 was added to the second tank 2 at a concentration of about 5 vol%. In both tanks 1 and 2, the pH was controlled to 4.5 and the temperature was controlled to 30° C., and the microorganisms were cultured for about 8 hours to grow these microorganisms.

Next, sterilized 5-fold diluted Cane's molasses medium (yeast extract: 3 g/,
(NH ₄ ) ₂ SO ₄ : 1 g/, KH ₂ PO ₄ : 1 g/, and
_MgCl2・_6H2O : 0.5g/), flow rate 0.07
Continuous fermentation was carried out under the above-mentioned fermentation conditions by continuously supplying the mixture to the pre-stage tank 1 at a rate of 1/h. The ethanol concentrations in the reaction solution at each outlet of both the front and rear tanks 1 and 2 were 45 g/ and 64 g/, respectively.

Next, increase the raw material supply flow rate from 0.07/h to 0.14/h.
The ethanol concentration at each flow rate was measured by increasing the flow rate sequentially to 0.21/h and 0.28/h. FIG. 3 shows the relationship between the raw material dilution rate (=raw material supply flow rate/total actual volume of the fermenter) and alcohol productivity. As can be seen from the figure, alcohol productivity improved in proportion to the dilution rate, and at a dilution rate of 0.2 h ^-1 (flow rate 0.28/h), alcohol productivity reached a high value of about 13 g/h. Moreover, the ethanol concentration of the reaction liquid flowing out from the latter stage tank 2 hardly changed.

As described above, high fermentation yields can be achieved by using two fluidized bed fermentation tanks, the front and rear tanks, and culturing bacteria with alcohol fermentation ability attached to the carrier in the first tank, and culturing immobilized yeast in the second tank. and was able to obtain high alcohol productivity. On the other hand, it has been reported that in a basic continuous culture method that does not use a carrier for attaching bacterial cells, the ethanol productivity is 2 to 3 g/h. As described above, according to the present invention, it is possible to maintain a high alcohol fermentation yield and significantly improve productivity.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between culture time and ethanol concentration for various microorganisms in batch fermentation.
Figure 2 is a schematic diagram of the fermentation equipment used in the examples, Figure 3
The figure is a graph showing the relationship between raw material dilution rate and alcohol productivity in Examples, and FIG. 4 is a schematic diagram of the fermentation apparatus used in Comparative Example 2. 1, 2...Fluidized bed fermentation tank.

Claims (1)

[Claims] 1. Continuous production of alcohol by fermentation, characterized by arranging two fluidized bed fermentation devices in series, culturing bacteria with alcohol fermentation ability attached to a carrier in the first stage, and culturing immobilized yeast in the second stage. Law.