JPS6136919B2 - - 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 petrochemistry, has been in the spotlight as an energy alternative to petroleum. It uses cellulosic or starchy materials such as sugar cane, molasses collected from sugar cane, sweet potatoes, potatoes, and corn as raw materials, and ferments them continuously using 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 in the fermenter, and as a result,
The present invention has now been completed.

The method for producing alcohol according to the present invention involves arranging two fermentation apparatuses in series each equipped with a separation means for separating the carrier from the reaction solution, culturing bacteria with alcohol fermentation ability attached to the carrier in the first stage, and culturing the bacteria with alcohol fermentation ability in the second stage. This is a continuous method for producing alcohol by fermentation, which is characterized by culturing flocculent yeast in

Examples of fermentation devices equipped with separation means include those shown in the accompanying drawings. That is, in the fermentation apparatus 1 shown in FIG. 1A, a carrier settling section 4 is provided on the side of a fermentation tank 3 equipped with an agitator 2, and the carriers are allowed to settle and separate in the section 4 to prevent them from flowing out of the tank. This is how it was done. In addition, the fermentation apparatus 1 shown in FIG.
1, a carrier sedimentation tank 14 is provided outside the fermentation tank 13 equipped with an agitator 12, so that the carriers flowing out from the fermentation tank 13 are sedimented and separated in the sedimentation tank 14, and the settled carriers are returned to the fermentation tank 13. This is what I did. Further, the fermentation apparatus 21 shown in FIG. The carrier is allowed to flow down and circulated within the tank, and the carrier is separated from the reaction solution above the liquid circulation member 24. Furthermore, the fermentation apparatus 31 shown in FIG. Carbon dioxide gas is discharged and the reaction liquid is taken out from a small diameter branch. And these fermentation devices 1, 1
1, 21, and 31 are all configured so that the pH and temperature can be controlled to optimum values.

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 flocculating yeast may be any yeast having flocculating ability and alcohol fermentation ability, and those of the genus Ssccharomyces are particularly preferably used. By culturing flocculating yeast in the latter stage, unreacted fermentable sugars that were not fermented in the former stage are fermented to produce alcohol, improving 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) 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, the productivity of alcohol can be increased. can be significantly improved.

(2) Since flocculating yeast is cultured in the latter stage, 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.

(3) Since bacteria and flocculating yeast that have good adhesion to the carrier are used, the average terminal velocity of the bacterial cells is high, and therefore the bacterial cells can be separated from the reaction solution by a simple separation method, reducing equipment costs. There are big advantages in this point.

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 the 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 MgC _{2.6H 2} O: 0.5 g/) were used for batch fermentation at a fermentation temperature of 30°C, and the fermentation characteristics were evaluated over time. I looked into it.

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 2 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 (55 g/day on the second day), followed by microorganism B, and even on the fourth day, microorganisms C and D have an alcohol concentration of approximately It was only 40g/.

Comparative Example 2 A flocculating baker's yeast manufactured by Kyowa Hakko Co., Ltd. was cultured in a fermentation device 31 with an actual volume of 1.2 as shown in FIG.
A 5-culture diluted Cane's molasses medium containing the same sterilizer as that used in Comparative Example 1 was continuously supplied as a fermentation raw material at a flow rate of 0.06/h, and continuous fermentation was carried out under the fermentation conditions of a temperature of 30° C. and a pH of 5. The reaction solution was continuously drawn out using a microtube pump. The ethanol concentration in the effluent reaction solution was approximately the same as in the case of batch fermentation (Comparative Example 1), about 57 g/.

Example A fermentation apparatus shown in FIG. 3 was used. This is a system in which two devices of the same type as the fermentation device 31 with an actual volume of 1.2 shown in FIG.
42 has stirrers 43 and 44, respectively, and is configured to be able to control temperature and pH. Further, these fermentation tanks 41 and 42 are respectively equipped with substantially Y-shaped solid-liquid separation members 45 and 46 for separating the carrier from the reaction liquid, and the large-diameter branch portions 45 of the members 45 and 46
Carbon dioxide gas is discharged from a, 46a, and the small diameter branch part 4
The reaction liquid is discharged from 5b and 46b. Then, the fermentation raw material is transferred to the pre-stage tank 4 using a pump 47.
1, the reaction liquid is then sent from the former tank 41 to the latter tank 42 by a pump 48, and taken out from the latter tank 42 by a pump 49.

Medium consisting of glucose 100 g/ yeast extract 3 g/ KH ₂ P ₀₄ 1 g/ (NH ₄ ) ₂ SO ₄ 1 g/ MgC _{2.6H 2} O 0.5 g/ antifoaming agent (manufactured by Toshiba Silicon Corporation) 0.3 g/ 400ml in the first tank 41, and the second tank 42
600ml each, and 5w of heat-treated crushed vermiculite (60 to 80 mesh) was added to the pre-stage tank 41.
t/vol%, and the above medium was heat sterilized. Next, 100 ml of the culture solution of Zymomonas mobilis TACC Deposit No. 10988 cultured using the above medium was added to the former tank 41, and brewer's yeast of the genus Satucharomyces was cultured in the same manner as above.
100 ml of the culture solution of IFO Deposit No. 2018 was added to the rear tank 42. Both tanks 41 and 42 have a pH of 4.5 and a temperature of 30.
These microorganisms were grown by culturing them for about 8 hours while controlling the temperature at each temperature.

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
MgC _{2.6H 2} O: 0.5g/), flow rate
Continuous fermentation was carried out under the above fermentation conditions by continuously supplying to the pre-stage tank 41 at a rate of 0.07/h. Front and rear tanks 41, 42
The ethanol concentration in the reaction solution at each outlet of
They were 45g/ and 64g/, 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. The relationship between the raw material dilution rate (=raw material supply flow rate/total actual volume of the fermenter) and alcohol productivity is shown in FIG. 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 42 hardly changed.

As described above, high fermentation yield can be achieved by culturing bacteria with alcohol fermentation ability attached to the carrier in the first stage and cultivating flocculating yeast in the second stage, using two fermentation devices equipped with separation means. and high alcohol productivity. On the other hand, in the basic continuous culture method that does not use carriers for bacterial attachment, the productivity of ethanol is 2 to 3 g/
・It is reported that 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 A, B, C, and D are all schematic diagrams of fermentation equipment equipped with separation means. Figure 2 is a graph showing the relationship between culture time and ethanol concentration for various microorganisms in batch fermentation. Figure 3 is a graph showing the relationship between culture time and ethanol concentration for various microorganisms in batch fermentation. FIG. 4, which is a schematic diagram of the fermentation apparatus used in the examples, is a graph showing the relationship between the raw material dilution rate and alcohol productivity in the examples. 41...Front stage fermenter, 42...Late stage fermenter, 4
5, 46...Solid-liquid separation member.

Claims (1)

[Claims] 1. Two fermentation devices equipped with separation means for separating the carrier from the reaction solution are arranged in series, and bacteria with alcohol fermentation ability attached to the carrier are cultured in the first stage, and flocculating yeast is cultured in the second stage. A method for continuous production of alcohol by fermentation characterized by: