WO2019008680A1 - Polylactic acid producing method and polylactic acid producing device - Google Patents

Abstract

[Problem] To provide: a polylactic acid producing method which is environment-friendly and can obtain a polylactic acid having a desired molecular weight with high efficiency and for a short time in order to provide a polylactic acid that can be expected to be used as a battery material for a secondary battery or the like; and a polylactic acid producing device for producing a polylactic acid having a desired molecular weight with high efficiency and for a short time. [Solution] Used are a polylactic acid producing method comprising, in combination, a starch liquefaction step, a starch saccharization step, a lactic acid fermentation step, a decomposition treatment step and a polylactic acid producing step; and a polylactic acid producing device which uses said method.

Description

Method for producing polylactic acid and apparatus for producing polylactic acid

The present invention relates to a method for producing polylactic acid which is a biodegradable plastic, and an apparatus for producing polylactic acid.

Biodegradable plastic functions as good as normal plastic during use, and after use, it is rapidly degraded by microorganisms in the soil, for example, in soil, etc. The organic component of the soil and the plastic that becomes water and carbon dioxide are currently attracting attention due to waste problems etc., and various products have been announced so far. For example, polylactic acid obtained by dehydrating and polymerizing lactic acid obtained by fermenting starch such as corn and potato with lactic acid bacteria is mentioned, and it is used for agricultural multi films and compost bags.

Polylactic acid (hereinafter sometimes abbreviated as "PLA") is a product obtained by dehydration condensation polymerization of lactic acid (see, for example, FIG. 1 below), and conventionally, lactic acid fermentation is caused when lactic acid bacteria are caused to act on vegetable starch. It is known that lactic acid can be obtained. In addition, polylactic acid can be obtained by dehydration condensation polymerization of lactic acid by adding an appropriate amount of a catalyst in which equal amounts of ruthenium oxide and the like and titanium oxide are mixed to concentrated lactic acid and stirring, for example. It has been known. Under the present circumstances, it is necessary to discharge the water which arose in dehydration condensation polymerization reaction out of the system, and the method of carrying out decompression distillation of water conventionally is used as a method of discharging such water (for example, patent document 1) reference).

Also, as shown in FIG. 1, low molecular weight oligomers are produced from L-lactic acid, in which case dimerized L-lactide is included. It is known that this L-lactide can be ring-opened to produce high molecular weight polylactic acid.

Furthermore, after passing through a polymerization process of polylactic acid production process, in particular, in a polymerization tank to which lactic acid is supplied, lactic acid is heated for dehydration condensation polymerization to synthesize a lactic acid polymer, it is partitioned by a pair of electrodes, partition walls and partition walls In the electrodehydration tank having a dewatering part and the dewatering part provided on the cathode side of the electrode, direct current is applied to the lactic acid polymer dehydrated and polymerized in the polymerization step to electroosmotic water in the lactic acid polymer. There is disclosed a method of obtaining polylactic acid by treatment by an electro-dehydration step of transferring to a dehydrating part according to (see, for example, Patent Document 2 below FIG. 2).

In FIG. 2, in producing polylactic acid to be a polymer, lactic acid and a catalyst are mixed, and after dehydration condensation polymerization is carried out in a polymer layer, it is an apparatus for obtaining a polymer (polylactic acid) through an electric dehydration tank.

FIG. 2 is a schematic view conceptually showing the structure of a conventional polylactic acid production apparatus. The poly (lactic acid) production apparatus comprises a mixing apparatus, a polymerization tank, and an electric dehydration tank. The polylactic acid production apparatus mixes a catalyst with lactic acid in a mixing apparatus, heats the mixture in a polymerization tank to carry out dehydration condensation polymerization, and further dewaters it in an electrodehydration tank by electroosmosis to obtain a desired polylactic acid. You can get In the polylactic acid production apparatus of the present invention, a polymerization tank and an electric dehydration tank are connected by a circulation pipe, and by repeating polymerization and drying a predetermined number of times and time, polylactic acid having a desired molecular weight is obtained. It can be done.

By the way, since polylactic acid is expected to exhibit the same excellent functions as plastics and to be able to lead to a solution to problems such as waste problems, development of applications in various industries is also promoted There is.

In particular, with regard to secondary batteries that are particularly developed in recent years as consumer batteries for automobiles, power storage equipment, etc., it is expected that various problems due to disposal of conventional batteries can be solved by using biodegradable plastic as the member. ing.

However, there are problems in manufacturing the secondary battery, such as the structure and material of the secondary battery, and in particular, it is a major problem to set the basic material of the secondary battery.

Japanese Patent Application Publication No. 2003-335850 Patent No. 3734821 gazette

The present invention has been made in view of the above, and provides polylactic acid which is environmentally friendly and can be expected to be used as a battery material such as a secondary battery. In order to solve this problem, first of all, a method for producing polylactic acid capable of obtaining polylactic acid having a desired molecular weight in a high efficiency and in a short time, and to obtain polylactic acid having a desired molecular weight in a high efficiency and a short time It is an object of the present invention to provide an apparatus for producing polylactic acid.

As a result of intensive investigations, the inventor of the present invention may produce lactic acid obtained by lactic acid fermentation, for example, by purifying the lactic acid by a technique such as electrodialysis, and further polymerizing to produce polylactic acid having a desired molecular weight range. It has been found that it is possible to complete the present invention.

The first invention of the present invention relates to a method for producing polylactic acid, and specifically, it is as follows.

That is, this invention is an invention combining the following steps (i) to (v).
(I) A starch-liquefying process in which a mixture of carbohydrates derived from plants and water is heated to gelatinize the mixture of carbohydrates and water, and further lactic acid is added and steamed to be liquefied;
(Ii) a starch saccharification step of obtaining liquid sugar by causing a saccharifying enzyme to act on the liquefied starch obtained in (i);
(Iii) A mixture containing liquid sugar after adding and mixing materials for fermentation such as sodium chloride, manganese sulfate, ammonium phosphate, skimmed milk powder, soy milk, waste molasses and surfactant to the liquid sugar obtained in (ii) Lactic acid fermentation process to obtain lactic acid by fermentation in the presence of a fermentation strain such as plant-derived lactic acid bacteria
(Iv) a decomposition treatment step of decomposing the lactic acid salt into lactic acid and sodium hydroxide after the lactic acid obtained in (iii) is neutralized with sodium hydroxide to obtain a lactic acid salt;
(V) A polylactic acid production step of heating and dehydrating the lactic acid obtained in (iv), and then heating to generate polylactic acid.

In the method for producing polylactic acid according to the present invention, in the above-described starch liquefying step (i), the mixing ratio of water to starch is 70 parts by weight to 80 parts by weight of water in the mixture of carbohydrate derived from plant and water. The present invention relates to a method for producing polylactic acid, which comprises 30 parts by weight to 20 parts by weight of starch.

In the method for producing polylactic acid according to the present invention, the temperature of liquefied starch is adjusted to 50 ° C. to 65 ° C., and the hydrogen ion concentration (pH) is adjusted to 6.0 to 6.5 in the above-mentioned starch saccharification step (ii). The present invention relates to a method for producing polylactic acid.

In the method for producing polylactic acid of the present invention, after adding sodium chloride, manganese sulfate, ammonium phosphate, skimmed milk powder, soy milk, waste molasses and surfactant to liquid sugar in the above-mentioned lactic acid fermentation step (iii) The present invention relates to a method for producing polylactic acid, wherein lactic acid is obtained by fermenting a mixture containing liquid sugar in the presence of plant-derived lactic acid bacteria.

In the method for producing polylactic acid according to the present invention, the lactic acid is neutralized with sodium hydroxide to obtain a lactic acid salt in the above-mentioned decomposition treatment step (iv), and then the lactic acid salt is decomposed into lactic acid and sodium hydroxide. , Relates to a method for producing polylactic acid.

The method for producing polylactic acid according to the present invention is a method for producing polylactic acid, wherein the lactic acid is concentrated by heating and dehydrating in the above-mentioned polylactic acid production step (v), and then heating is further carried out to produce polylactic acid. Pertain to.

The apparatus for producing polylactic acid according to the present invention is an apparatus used for the method for producing polylactic acid described above,
The device is a sealable device comprising a saccharification reaction tank, a stirring device, a jacket and a condenser.
The saccharification reaction tank is provided with a raw material inlet for charging raw material starch and water, and an outlet for discharging liquefied starch, and the charged raw material starch and water are heated and stirred in the saccharification reaction tank After being gelatinized, it is a reaction vessel for adding L-lactic acid, stirring, heating and liquefying it,
The stirring device is provided with a stirring blade in the saccharification reaction tank via a stirring rod, and the raw material starch and water introduced into the saccharification reaction tank are mixed by rotating the stirring rod at a predetermined speed by the stirring device. A device for
The jacket is disposed around the periphery of the saccharification reaction tank, and comprises an oil-filled jacket provided with a water cooling jacket for cooling the saccharification reaction tank and an electric heater for heating the saccharification reaction tank below; A device to control the temperature of the
The condenser relates to a polylactic acid producing apparatus, which is an apparatus for coagulating gas components generated by heating raw material starch and water in the saccharification reaction tank.

The apparatus for producing polylactic acid according to the present invention is an apparatus used for the method for producing polylactic acid described above,
The device is a sealable device comprising a fermentation chamber, a stirring device, a heat retaining jacket, a mesh negative electrode, and an electrically insulating mount.
The fermentation chamber is a container for charging liquid sugar, lactic acid bacteria and additives which are materials for fermentation, mixing and performing at a temperature set for fermentation,
The stirring device is provided with a stirring blade in the fermentation chamber via a stirring rod, and is a device for mixing the fermentation material introduced into the fermentation chamber by rotating the stirring rod at a predetermined speed by the stirring device. Yes,
The heat insulating jacket is a member provided on the outer periphery of the fermentation chamber to keep the fermentation chamber warm,
The reticulated negative electrode is provided in the fermentation chamber via a diaphragm, and the lactic acid produced by fermentation is transferred to the center of the apparatus by charging the outside of the fermentation chamber as an anode, and the lactic acid produced by the fermentation is discharged from the lactic acid concentrate outlet. A device for discharging,
The electrically insulating mount is a member provided at the lower part of the fermentation chamber, provided with a lactic acid concentrate outlet at the center, and made of an insulating material so that the fermentation chamber and the lactic acid concentrate outlet do not conduct electricity.
The invention relates to a polylactic acid production apparatus.

The apparatus for producing polylactic acid according to the present invention is an apparatus used for the method for producing polylactic acid described above,
The apparatus is an electrodialysis apparatus including a positive electrode chamber, a fermentation liquid chamber, an auxiliary positive electrode chamber, an auxiliary negative electrode chamber, and a negative electrode chamber,
In the positive electrode chamber, a sodium sulfate solution is circulated and connected to the positive electrode so that current can be supplied to the negative electrode.
In the fermentation chamber, a fermentation solution containing lactate is circulated.
In the auxiliary positive electrode chamber, fresh water is circulated and connected to the auxiliary positive electrode so that the auxiliary negative electrode can be energized.
The auxiliary anode chamber is circulated with sodium hydroxide solution and connected to the auxiliary anode so that electricity can be supplied from the auxiliary cathode.
In the negative electrode chamber, a sodium sulfate solution is circulated and connected to the negative electrode so that current can be supplied from the positive electrode.
Between the positive electrode chamber and the fermentation liquid chamber, an anion exchange membrane diaphragm is provided on the positive electrode chamber side, and a cation exchange membrane is provided on the fermentation liquid chamber side.
A cation exchange membrane is provided between the fermentation liquid chamber and the auxiliary positive electrode chamber,
A cation exchange membrane is provided between the auxiliary positive electrode chamber and the auxiliary negative electrode chamber,
Between the auxiliary negative electrode chamber and the negative electrode chamber, an anion exchange membrane diaphragm is provided on the auxiliary negative electrode chamber side, and a cation exchange membrane is provided on the negative electrode chamber side.
There is provided a mechanism capable of controlling so that a direct current is supplied between the positive electrode and the negative electrode without connecting the auxiliary positive electrode and the auxiliary negative electrode when separating a lactate from the fermentation liquid.
The invention relates to a polylactic acid production apparatus.

Hereinafter, the present invention will be described in detail.

<Method of producing polylactic acid>
FIG. 1 shows the chemical structures of major components in the polylactic acid (PLA) production flow.

FIG. 3A and FIG. 3B show the manufacturing process or manufacturing flow of polylactic acid (PLA).

Although the flow of the manufacturing process of polylactic acid (PLA) is shown in FIG. 3A and FIG. 3B, each process is demonstrated according to a flow hereafter.

First, a carbohydrate such as a plant-derived starch (shown as a vegetable starch in FIG. 3A and a raw material starch in FIG. 3B) and water are mixed to hydrate the carbohydrate (hydration step), which is heated to gelatinize Yes (gelatinization process). Furthermore, for example, 0.1 wt% to 1.0 wt% of lactic acid is added to gelatinized starch, and the mixture is liquefied by cooking at 110 ° C. to 130 ° C. (liquefying step). A saccharifying enzyme such as amylase is allowed to act on the liquefied starch to cause monosaccharification (saccharification step). This saccharified liquid sugar is mixed with sodium chloride, manganese sulfate, ammonium phosphate, skimmed milk powder, soy milk, waste molasses, surfactant and the like, and this is reacted with plant lactic acid bacteria such as Lactobacillus Plantarm for fermentation (fermentation process) ), Get lactic acid.

After fermentation, the produced lactic acid is extracted as a lactate according to a known appropriate formulation (lactate extraction step) and purified (lactic acid purification step). The purified lactic acid is heated for condensation polymerization (polymerization step) to form polylactic acid (PLA). The polymerization can be carried out under known conditions, and if necessary, additives and catalysts can also be added. After polymerization, polylactic acid (PLA) may be purified using a known formulation.

As described above, the present invention will be further described in detail.

The method for producing PLA (polylactic acid) of the present invention is an invention comprising the following steps (i) to (v) in combination.
(I) A starch-liquefying process in which a mixture of carbohydrates derived from plants and water is heated to gelatinize the mixture of carbohydrates and water, and further lactic acid is added and steamed to be liquefied;
(Ii) a starch saccharification step of obtaining liquid sugar by causing a saccharifying enzyme to act on the liquefied starch obtained in (i);
(Iii) A mixture containing liquid sugar after adding and mixing materials for fermentation such as sodium chloride, manganese sulfate, ammonium phosphate, skimmed milk powder, soy milk, waste molasses and surfactant to the liquid sugar obtained in (ii) Lactic acid fermentation process to obtain lactic acid by fermentation in the presence of a fermentation strain such as plant-derived lactic acid bacteria
(Iv) a decomposition treatment step of decomposing the lactic acid salt into lactic acid and sodium hydroxide after the lactic acid obtained in (iii) is neutralized with sodium hydroxide to obtain a lactic acid salt;
(V) A polylactic acid production step of heating and dehydrating the lactic acid obtained in (iv), and then heating to generate polylactic acid.

Here, in the starch liquefying step (i), after the plant-derived carbohydrate and water are mixed, the mixture of carbohydrate and water is heated to gelatinize, and further lactic acid is added to be boiled and liquefied. The plant-derived carbohydrate is a polysaccharide in which a plurality of monosaccharides and the like are bound, and, for example, starch can be mentioned as an example thereof. In general, starch, which is a high molecular compound, is insoluble in water, and in the present invention, in order to make insoluble carbohydrates water soluble, it is mixed with water to obtain a mixture of carbohydrates and water, and then heated. Gelatinize. Furthermore, lactic acid is added to gelatinization and it is liquefied by steaming. The amount of lactic acid to be added is preferably, for example, 0.1% by weight to 1.0% by weight. Further, conditions for steaming are not particularly limited, but, for example, steaming may be carried out at a temperature of 110 ° C. to 130 ° C.

Starch is divided into amylose and amylopectin according to its structure, and amylose is a linear molecule having a relatively small molecular weight, and amylopectin is a highly branched molecule having a relatively large molecular weight. Although the properties of amylose and amylopectin are different, both coexist in starch, so that the raw material starch used in the present invention can be adapted to these processes because it is liquefied, gelatinized and saccharified. Starch may be used.

Specific examples of starches for starches include corn starch, so-called corn starch, corn starch, wax corn starch, high amylose corn, etc., wheat as wheat, wheat starch, and rice as rice. There are starches from beans such as broad bean, green beans and azuki beans, potato starch as potato, sweet potato starch as sweet potato, tapioca starch as tapioca, and starch from bracken and straw etc.

More specifically, examples of starch raw materials include corn as corn, so-called corn starch, so-called corn starch, corn starch, waxy corn starch, high amylose corn, etc., wheat as wheat, rice as rice, rice starch, broad bean There are starches from beans such as green beans and azuki beans, potato starch as potato, sweet potato starch as sweet potato, tapioca starch as tapioca, and starch from bracken and straw etc.

In the saccharification step (ii), a saccharifying enzyme is allowed to act on the liquefied starch obtained in the starch liquefaction step to obtain liquid sugar. As the saccharifying enzyme, an enzyme catalyzing a hydrolysis reaction of high molecular weight saccharides such as amylase, and a saccharifying enzyme capable of degrading relatively low molecular weight saccharides can be used, and can be used in this technical field. And the like can be used without limitation. Thus, lactic acid can be efficiently obtained in the lactic acid fermentation process of the following process by making a saccharifying enzyme act on saccharides, and making it monosaccharide-ized.

More specifically, examples of saccharifying enzymes that degrade carbohydrates include α-amylase (EC 3) as described in, for example, Applied Carbohydrate Science, Vol. 1, No. 1, pp. 17 to 22 (2011). .2.1.1), beta-amylase (EC 3.2.1.2), glucoamylase (EC 3.2.1.3), alpha-glucosidase (EC 3.2.1.20) It can be arbitrarily selected according to various compositions and forms of starch derived from plants and the like. Further, not only the decomposition of the raw material starch but also an oligomer during the decomposition or an intermediate product such as dextran or a disaccharide can be selected as appropriate degrading enzymes, ie, saccharifying enzymes. The saccharifying enzyme can also be obtained, for example, by Clytase (registered trademark) T10S (heat-resistant α-amylase) of Amano Enzyme Co., Ltd. or the like.

In the present invention, in the saccharification step, raw material starch is mixed with water and steamed and gelatinized, and then lactic acid is added to bring it to 90 ° C. to 105 ° C., preferably 95 ° C. to 100 ° C., for 15 minutes to 120 minutes, preferably Stirring and heating may be performed for 30 minutes to 60 minutes. The stirring conditions may be stirring by means of a container of suitable shape and stirring means such as stirring blades. The number of rotations of stirring depends on the size and shape of the container, the stirring means such as the number and shape of stirring blades, but stirring may be performed, for example, at 70 rpm (times / minute) to 100 rpm (times / minute).

The raw material starch is stirred and heated to gelatinize, and then a 50% solution of L-lactic acid (C ₃ H ₆ O ₃ ) having a molecular weight of about 90 is added by 0.1% to 1% by weight based on the amount of starch added. 110 ℃ ~ 130 ℃, preferably at ^{120 ℃ ~ 125 ℃, 1.2Kg /} cm 2 ~ 2.0Kg / cm 2, preferably from ^{1.5Kg / cm 2 ~ 1.8Kg / cm} 2 of pressure under pressure environment The mixture is stirred for 5 hours to 10 hours, preferably 7 hours to 8 hours to give liquefied starch. L-lactic acid can also be obtained, for example, by Musashino Lactic Acid (registered trademark) 90, etc. manufactured by Musashino Chemical Laboratory Co., Ltd.

In the saccharification step, the hydrogen ion concentration (pH) may be adjusted to 6.0 to 6.5 using aqueous ammonia (aqueous ammonia hydroxide), and the temperature may be 50 ° C. to 65 ° C., preferably 55 ° C. to 60 ° C. Then, add 0.1 to 1% by weight of the above saccharifying enzyme to the amount of starch added and stir for 5 to 12 hours, preferably 6 to 10 hours, more preferably 7 to 8 hours It is good to monosaccharideize by carrying out. In this process, starch liquefying enzyme is generally used for liquefying starch, but it is not preferable because the reaction time is as long as 10 hours to 15 hours and the cost is high. According to the lactic acid hydrolysis method of the present invention, it is possible to use the obtained lactic acid solution or the lactic acid solution distilled at the time of lactic acid purification as it is after lactic acid fermentation, which is effective for cost reduction and reaction time shortening. is there.

FIG. 4 is a schematic view of an apparatus used for starch saccharification in the method for producing PLA (polylactic acid) of the present invention.

FIG. 4 is a starch saccharification apparatus (401) in the present invention. The starch saccharification device (401) comprises a saccharification reaction tank (402), a stirring device (403), a jacket (404), and a condenser (405). The starch saccharification apparatus (401) inputs the raw material starch and water into the saccharification reaction tank (402) from the raw material inlet (406), and mixes them. The mixture is heated in a saccharification reaction tank (402) to be steamed and gelatinized, and then L-lactic acid is added and stirred and heated.

The temperature control of heating heats the saccharification reaction tank (402) through the oil jacket (404b) with heat generated from the electric heater (407) and cools the saccharification reaction tank (402) by the water cooling jacket (404a) Is controlled to a predetermined temperature. The control of the stirring is performed by a stirring device (403) provided with a stirring rod (403b) having a stirring blade (403a). Temperature control and agitation control of the saccharification reaction tank (402) can also be controlled automatically using a control system (not shown) such as a computer.

In addition, the saccharification reaction tank (402) may be a closed system, and may be pressurized or depressurized. Some or all of the gas components such as water vapor generated by heating and stirring are condensed in the condenser (405) and can be stored in the condensate reservoir (408). The heated, stirred, gelatinized and further liquefied starch is discharged from the content outlet (409).

With regard to the shape and size of the stirring blade (403a), the purpose is to promote efficient generation / acquisition of lactic acid, which is the object of the present invention as well as the embodiment described above, and a sufficient stirring effect can be expected. It may be of any shape or size.

Table 1 below is a comparison chart of starch saccharification methods, comparing the starch saccharification method according to an embodiment of the present invention with the conventional method. As can be seen from this table, the system of the present invention can shorten the reaction time as compared with the conventional method, and can be expected to reduce the cost.

In the lactic acid fermentation step (iii), a mixture containing liquid sugar after adding and mixing sodium chloride, manganese sulfate, ammonium phosphate, skimmed milk powder, soy milk, waste molasses and surfactant to the liquid sugar obtained in the saccharification step Ferment in the presence of plant-derived lactic acid bacteria to obtain lactic acid. The amount of material added to the liquid sugar is
0.01 wt% to 0.1 wt% of sodium chloride,
0.01 wt% to 0.5 wt% of manganese sulfate,
0.01 wt% to 0.1 wt% of ammonium phosphate,
0.1% to 1.0% by weight of skimmed milk powder,
0.1% to 1.0% by weight of soy milk,
0.1% to 1.0% by weight of waste molasses,
0.01 wt% to 0.05 wt% of surfactant
It is good to use it in the range of, mixing these and using.

Furthermore, a mixture of these is fermented in the presence of plant-derived lactic acid bacteria to obtain lactic acid. As plant-derived lactic acid bacteria used in the present invention, for example, bacteria of the genus Lactobacillus are preferable, and further, among these bacteria, Lactobacillus Plantarum is preferably used. There is no particular limitation as to the amount of addition of the plant-derived lactic acid bacteria or the timing of addition, as long as it is a method used in the technical field.

Lactic acid bacteria are a general term for bacteria that produce lactic acid by metabolism, and those that produce a large amount of lactic acid from saccharides by fermentation and do not make rotten substances that cause malodor are generally called lactic acid bacteria. Lactic acid bacteria are also classified into homo lactic acid bacteria that produce only lactic acid as the final product and hetero lactic acid bacteria that simultaneously produce other than lactic acid, such as vitamin C, alcohol, and acetic acid, from the mode of fermentation without having a TCA cycle. .

Moreover, according to the shape of the bacteria, it may be classified into globular lactobacilli and scaly lactobacilli, and fungi satisfying the following requirements are considered as lactic acid bacteria.
-Gram-positive-No. of bacilli-Coccus-No endospores-No motility-Produce 50% or more of lactic acid to glucose consumed-Necessary requirement for niacin

In the present invention, it is sufficient that lactic acid can be fermentatively produced based on a fermentation raw material obtained from starch-derived carbohydrate.

Specifically, as bacteria for lactic acid fermentation, Lactobacillus such as L. delbrueckii, L. acidophilus, L. casei, L. fructivorans, L. hilgardii, L. paracasei, L. rhamnosus, L. paracasei, L. plantarum etc. Enterococcus spp. (Etococcus sp.) Such as B. bifidum, B. adolescentis, B. bifidum, B. adolescentis etc. Bifidobacterium (Bifidobacterium), fecalis (E. faecalis), fecium (E. faecium) etc. Lactococcus, such as L. lactis, L. cremoris, Pediococcus such as P. damnosus, Leuconostoc such as L. mesenteroides, etc. Among them, Lactobacillus (Lactobacillus), and further Lactobacillus Plantarum are preferably used in the present invention.

Lactic acid fermentation is one of the types of fermentation that occurs in bacteria and animal cells in the absence of oxygen. Through lactic acid fermentation, one molecule of glucose is finally converted to two molecules of lactic acid as represented by the following formula (1).

C ₆ H ₁₂ O ₆ → 2CH ₃ CH (OH) COOH (1)

As described in the above formula (1), glucose produced from starch is fermented by a fermentation strain such as the above-mentioned lactic acid bacteria to produce lactic acid.

The bacteria used for the above-mentioned lactic acid fermentation are usually in a form for storage, and are subjected to an activation treatment or activation treatment for use in lactic acid fermentation. As a prescription for that, the strain activation apparatus (501) shown in the following FIG. 5 can be exemplified.

For example, equipment shown in FIG. 5 may be selected as equipment used for the adjustment of lactic acid bacteria.
-Containers such as wide-mouthed bottles (502 in FIG. 5, hereinafter referred to as "wide-mouthed bottles") and lids (503 in FIG. 5)
Petri dish (504 in FIG. 5)
・ Hydrogen generator (It can be illustrated in Fig. 6 below)

As a material used for the adjustment of lactic acid bacteria, for example, the following materials may be selected.
-Dried lactic acid bacteria strain-Glucose-VRB extract-Peptone-Manganese sulfate-Sodium chloride-Molasses (can be made inexpensive by using waste molasses)
These are exemplifications, and may be replaced with substitutes as appropriate depending on conditions of use, amount and the like.

In FIG. 5, the wide mouth bottle (502) is closed with a lid (503). The lid (503) can be introduced into the hydrogen _{(H 2)} gas by hydrogen _{(H 2)} introduction tube a hole for introducing a gas (510). Further, after the hydrogen (H ₂ ) gas introduced into the lid (503) comes in contact with the strain in the wide-mouthed bottle (502), a hole for exhausting is provided and can be exhausted by the exhaust pipe (511).

In FIG. 5, a petri dish having a top open or a cylindrical container with a bottom (504) is disposed inside the wide-mouthed bottle (502). A cylindrical container (504) contains peptone and a dried strain (504a), and the strain is activated by contacting with hydrogen (H ₂ ) gas introduced into the wide-mouthed bottle (502). Under the cylindrical container (504), a rack (512) is provided, and inside the rack (512), a cotton wool containing water (505) is disposed, and a wide-mouthed bottle (502) It is also a weight to prevent floating in the water for thermal insulation filled in the constant temperature bath (507). In addition, another weight may be used for the absorbent cotton containing water (505), and a humidifier (not shown) may be installed if the humidity control is necessary.

In FIG. 5, a wide mouth bottle (502) is immersed in a thermostat (507) containing water for heat retention. A temperature control heater (506) is provided in the lower part of the thermostat (507), and the water temperature (508) of the thermostat (507) is measured by a thermometer (509) and controlled. As the thermometer can measure the temperature, any thermometer can be used without departing from the object of the present invention, and a temperature sensor (not shown) may be controlled by a control system (not shown) connected to a computer etc. .

In FIG. 5, activation of the fermentation strain is carried out, for example, in hydrogen gas at a temperature of 45 ° C. and 95% relative humidity (RH), and the strain can be activated under the conditions of maintaining the environmental conditions for 24 hours. Activated strains can be used for lactic acid fermentation, as described below.

As described above, the strain can be activated by the strain activation device (501) shown in FIG. 5, but various controls such as temperature control, hydrogen gas introduction, exhaust, water amount control for temperature control, humidity control, etc. A data measurement sensor (not shown) can be installed for automatic control, and the control method can also be performed using a computer (not shown) such as a personal computer.

FIG. 6 is an example of a hydrogen generator (601) for producing hydrogen for use in activating a fermentation strain such as lactic acid bacteria. In order to generate hydrogen using the hydrogen generator (601) shown in FIG. 6, for example, the following procedure can be performed.

1) A 5 to 20% (w / v), preferably about 10% (w / v) aqueous solution of sodium hydroxide (NaOH) is electrolyzed to form a mixed gas of oxygen (O ₂ ) and hydrogen (H ₂ ) Generate
2) For example, a heating element such as an iron-based oxidation heating element (for example, HOKHIRO (registered trademark)) is placed in a container such as stainless steel in the shape of a can, and oxygen (O ₂ ) Pass gas and hydrogen (H ₂ ) gas.
3) Oxygen is consumed by the heating element, and hydrogen gas is discharged from the outlet, and introduced into the above-mentioned apparatus for activating the lactic acid bacterial strain of FIG. 5 described above.
In the case where only hydrogen (H ₂ ) gas is taken out of the generated oxygen (O ₂ ) gas and hydrogen (H ₂ ) gas, the oxygen consumption step by the heating element becomes unnecessary.

The above procedure will be described along the description of FIG.

On the left side of FIG. 6, the container (607) opened at the top is sealed with a lid (610). In the lid (610), a positive electrode (indicated as "+" in FIG. 6) and a negative electrode (indicated as "-polar" in FIG. 6) are connected to a power supply (not shown). Are connected to the positive electrode (609) and the negative electrode (608) through a tube (611) serving as a conducting wire. A container (607) contains an aqueous solution of sodium hydroxide (NaOH) (604), in which a positive electrode (609) and a negative electrode (608) are immersed. When electricity is applied, an electrolysis reaction occurs, and oxygen (O ₂ ) gas is generated at the positive electrode (609) and hydrogen (H ₂ ) gas is generated at the negative electrode (608).

The generated oxygen (O ₂ ) gas and hydrogen (H ₂ ) gas are exhausted from the hollow pipe (611) penetrating the lid (610). The pipe (611) is connected to the rubber pipe (605a), and the discharged oxygen (O ₂ ) gas and hydrogen (H ₂ ) gas are introduced through the rubber pipe (605a) to the inlet of the right container (603) (612).

On the right side of FIG. 6, the container (603) is sealed with a lid (603a). Below the container (603), oxygen (O ₂ ) gas and hydrogen (H ₂ ) gas generated in the container on the left are introduced into the container (603) on the right via the rubber pipe (605a). A port (612) is arranged from which oxygen (O ₂ ) gas and hydrogen (H ₂ ) gas are introduced. In the lid (603a), oxygen (O ₂ ) gas is consumed in contact with the heating element (602) in the container (603), and an outlet (613) for discharging the remaining hydrogen (H ₂ ) gas ) is formed so as to penetrate the cover (603a), the outlet (613) is connected to the rubber tube (605b), hydrogen _{(H 2)} gas is discharged. The exhausted hydrogen (H ₂ ) gas is introduced into the strain activation apparatus (501) shown in FIG.

Among the oxygen (O ₂ ) gas and hydrogen (H ₂ ) gas introduced from the inlet (612), the oxygen (O ₂ ) gas is placed on a frame (606) installed at the lower part of the container (603) in contact with the heating element which are (602), oxygen _{(O 2)} is consumed heating element (602) reacts and oxygen _{(O 2).} For this reason, oxygen (O ₂ ) gas and hydrogen (H ₂ ) gas introduced from the inlet (612) are consumed by oxygen (O ₂ ) by the action of the heating element (602) and substantially hydrogen ( H ₂ ) Only gas is used, and hydrogen (H ₂ ) gas is discharged from the discharge port (613) and introduced into the strain activation device (501). As seen in FIG. 6, in order to bring the heating element (602) placed on the pedestal (606) into contact with the introduced oxygen (O ₂ ) gas, the platform portion of the pedestal (606) is meshed It is good to make it shape which allows gas to pass easily, such as shape.

<Lactic acid fermentation>
As described above, lactic acid fermentation in which glucose is converted to lactic acid is performed using activated fermentation strains such as lactic acid bacteria. The details will be described below.

Since glucose produced from starch through gelatinization, liquefaction and saccharification steps usually has a sugar content of about 23 to 25 °, in lactic acid fermentation, it is further boiled down to produce liquid sugar having a sugar content of about 50 °. And this may be used as a material for lactic acid fermentation.

The following composition is mentioned as an example of the culture component for lactic acid fermentation. These components are introduced into a fermenter and fermented.
Glucose solution (sugar content 50 °) 1 liter Soy peptone 50 g
・ Manganese sulfate 1 g
・ 1 mol of molasses
・ 2g of salt
・ VRB extract 10g
・ Lactic acid (for pH adjustment) Appropriate amount ・ Active lactic acid bacteria strain

When fermentation is carried out by shaking culture method, in order to prevent contamination of bacteria, it is carried out in a facility such as clean bench which can prevent bacteria contamination from the outside air. The culture conditions are not particularly limited as long as they do not deviate from the conditions for lactic acid fermentation, and although depending on the type of fermentation strain such as lactic acid bacteria used, the temperature is usually 37 ° C. or around for 24 hours Perform fermentation for about 30 hours to ferment lactic acid. In some cases, it may be a short time of about 10 hours to 24 hours or a long time of about 30 hours to 5 days.

The equipment used for the culture is not particularly limited as long as it is generally used in this field, but for example, as shown in FIG. 7, a flask-shaped container (701) Seal tightly at 702) and culture while permeating. In the container (701), the culture material (703) such as the culture components described above and the strain are placed. This culture can also be performed by an apparatus that can be automatically controlled, and the culture conditions can be controlled sequentially while monitoring various parameters such as shaking speed, temperature, pH in the culture solution, gas and the like. The various parameters can be monitored continuously by setting a sensor capable of responding to the parameters, or part of the culture solution can be collected and measured discontinuously or periodically. When automatic control is performed, the control method can also be performed using a computer (not shown) such as a personal computer.

Alternatively, for example, lactic acid fermentation can be performed while a tank-shaped culture vessel (802) such as a fermentation apparatus (801) shown in FIG. 8 is stirred by a stirrer (805). Fermentation materials can be input from the fermenter inlet (806), and if necessary, can be used as a sampling port for monitoring pH during culture and the number of viable cells. During culture or during lactic acid fermentation, an alkali such as sodium hydroxide can be added from an alkali tank (803) to control the pH. The temperature control of the culture vessel (802) can be controlled by the jacket (804) on the side of the culture vessel (802). After the fermentation, materials and the like used for the fermentation can be discharged from the discharge port (807). The number and position of the discharge ports (807) may be determined as appropriate. For example, the fermentation residue may be discharged from the lower discharge port, and the fermentation liquid containing lactic acid may be discharged from the upper or side position.

This culture or lactic acid fermentation can be further performed by an apparatus that can automatically control, and it is also possible to control culture conditions sequentially while monitoring various parameters such as stirring speed of stirring apparatus, temperature, pH in culture solution, and gas. it can. The various parameters can be monitored continuously by setting a sensor capable of responding to the parameters, or part of the culture solution can be collected and measured discontinuously or periodically. When automatic control is performed, the control method can also be performed using a computer (not shown) such as a personal computer.

For example, glucose with a sugar content of about 50 ° is charged into the fermenter of the fermentation apparatus into which the above-mentioned culture solution components are charged, and low speed (for example, about 30 Hz) under conditions of 37 ° C to 38 ° C and pH 6.5 to 7.0. The culture is carried out under conditions such as agitation and culture. Also, it is recommended that the amount of inoculum for the activated fermentation strain at the time of culture be 100 ml to 10 liters, usually about 1 liter, as a culture solution.

Furthermore, the culture can be carried out in two or more stages. That is, on a relatively small scale, mainly cultivating a strain for fermentation, cultivating in a larger container with the number of viable cells of the strain increased to some extent, and taking lactic acid fermentation to obtain a prescription for obtaining lactic acid Can. By dividing into the first stage (for example, the term pre-culture can be used) and the second stage lactic acid fermentation (for example the term main culture can be used), a small number of strains can be increased and Lactic acid can also be obtained in large yields.

The fermentation process is a process of adding lactic acid bacteria and additives to liquid sugar with a sugar content of 20 ° to 30 ° for lactic acid fermentation, and the nutrient components necessary for the growth of liquid sugar and lactic acid bacteria in the fermentation apparatus illustrated in FIGS. Hydrogen ion concentration after adding a necessary amount of nitrogen, nitrogen, polyphenols, etc.) and a surfactant (eg sucrose fatty acid ester etc.) to make it difficult to form colonies and precipitation and stirring for 1 to 2 hours Adjusted to a neutral range (pH 6.5 to 7.5) using this product, and then adjusted the temperature of internal use products to a temperature (38 ° C to 42 ° C) suitable for the growth of lactic acid bacteria, and then culture broth of lactic acid bacteria (eg Lactobacillus Plantarum) Add (2 to 5% by weight of viable cells in 1 g of culture solution to 3 to 5 billion cells) and stir at 70 rpm (times / minute) to 100 rpm (times / minute). The activity of the bacteria is inhibited by lactic acid in the fermentation liquid as the fermentation proceeds, so it is preferable to adjust the pH using sodium hydroxide so that the pH of the fermentation liquid does not become 3.5 or less.

FIG. 9 is a graph showing the relationship between the number of viable cells in the fermentation broth and the pH in the method for producing PLA (polylactic acid) of the present invention. When the fermentation approaches the end point, the amount of carbohydrate in the fermentation solution decreases, the growth of bacteria also slows and the rate of lactic acid production becomes extremely slow, so the lactic acid concentration mechanism is activated.

FIG. 9 is a figure which shows viable count and pH in the fermented liquor in the PLA (polylactic acid) manufacturing method of this invention. The horizontal axis (X axis) is the fermentation time (in hours), and the vertical axis (Y axis) is the number of viable cells in the fermentation broth (broken line, unit is arbitrary) and pH (solid line). The pH in the fermented liquid decreases according to the lactic acid produced by the fermentation. In order to neutralize the fermented liquid, the fermented liquid is adjusted to a neutral range (pH 6.5 to 7.5) using ammonia water, and ammonia water is added at the timing of the arrow, and as a result, the fermented liquid It is shown that the pH of Al shifts to the primary side. It is shown that the viable cell count increases with the fermentation time peaking at about 6 to 10 hours and then gradually decreases. Such a relationship between the number of viable cells and the pH of the fermentation liquid varies depending on various conditions such as the type, amount, temperature and composition of the culture solution used for lactic acid fermentation, so the above example is an example under predetermined conditions It goes without saying that

The end point of the fermentation production, that is, the end point of the culture may be determined while monitoring the relationship between the number of viable bacteria in the culture solution and the pH as described below. In addition, it can also be determined while monitoring the amount of lactic acid which is the desired product, and furthermore, any method commonly used in this field can be applied.

During culture, a part of the culture solution is collected to measure the pH, and the relationship with the number of viable cells is confirmed to determine the end point. Also in this method, in the method of determining the end point, the pH of the culture solution and the number of viable cells are changed as shown in FIG.

Hereinafter, the methods shown in FIGS. 10 and 11 will be described, but other methods may be considered. Either of them may be selected as appropriate.

In the above method, the pH of the culture solution is fermented to produce lactic acid and proceed to the acidic side (pH decrease), but when reaching a predetermined pH, water for neutralizing the culture solution An alkali such as sodium oxide is added to adjust the pH to 6.5 to 7.0 (the pH is set to 7.0 in the figure), and the end point is set as the number of lactic acid bacteria reaches the growth stage and the progress to the acidity is accelerated. It is determined.

In the above method, the pH of the culture solution is fermented to produce lactic acid and proceed to the acidic side (pH decrease), but when reaching a predetermined pH, water for neutralizing the culture solution An alkali such as sodium oxide is added to adjust the pH to 6.5 to 7.0 (the pH is set to 7.0 in the figure), and the end point is determined according to the acidity of the culture solution.

The fermentation (culture) may be terminated when the number of viable bacteria of the lactic acid bacteria strain is 700 million cells (Cell) / ml-fermented solution to 1 billion cells (Cell) / ml-fermented solution. However, when a larger number of strains is required or conversely, the number of strains may be adjusted appropriately. The number of strains can be confirmed by collecting a part of the fermented solution and measuring the absorbance (turbidity) to estimate the number of strains, and if the number of strains is large, dilute the misappropriated fermented solution in stages The absorbance (turbidity) may be measured.

<Filtration separation of lactic acid solution>
As described above, although lactic acid is produced in the lactic acid-fermented fermentation liquid, it is necessary to efficiently separate the fermentation liquid and the lactic acid. As a device for that, a fermentation device provided with a lactic acid concentration mechanism illustrated in FIG. 12, an example of a filtration separation device of FIG. 13, an example of an electrodialysis device for purifying lactic acid by electrodialysis of FIG. An example of an electrodialysis apparatus for purifying lactic acid according to

In the fermentation apparatus (1201) equipped with the lactic acid concentration mechanism illustrated in FIG. 12, the negative electrode is caused by passing a direct current through a circuit in which the reticulated electrode (negative electrode (1202)) installed and formed at the central part The lactate, which is mainly sodium lactate, migrates to the inside of the diaphragm (1205) through a cylindrical diaphragm (1205) made of a cation permeable membrane or the like that separates (1202) from the fermentation chamber (1204). At the start of fermentation, the inside of the diaphragm (1205) is filled with fresh water. As a result, fermentation residues including bacteria other than lactic acid bacteria and viable bacteria remain in the fermentation chamber (1204), and lactate is concentrated inside the diaphragm (1205). In the fermenter (1201) illustrated in FIG. 12, although the volume ratio of the fermentation chamber (1204) to the concentration chamber is about 10: 1, even a volume ratio of 1: 1 to 20: 1 functions sufficiently. As the volume ratio is increased, the concentration ratio of lactate also increases and the efficiency of fermentation also improves. However, practically, it is preferable to set the upper limit to about 30: 1.

FIG. 12 shows the structure of a fermentation apparatus (1201) equipped with a lactic acid concentration mechanism in the method for producing PLA (polylactic acid) of the present invention. In FIG. 12, the left side is a cross-sectional view of the fermenter (1201) viewed from above, and the right side is a cross-sectional view viewed from the lateral direction.

The fermentation apparatus (1201) comprises a fermentation chamber (1204), a reticulated negative electrode (1202) provided in the fermentation chamber via a diaphragm (1205), and a stirring device for stirring the fermentation broth in the fermentation chamber (1204) (1207) and a heat insulating jacket (1203) provided on the outer periphery of the fermentation chamber (1204) for keeping the fermentation chamber (1204) warm.

The fermenter (1201) inputs a liquid sugar, a lactic acid bacterium and an additive, which are materials for fermentation, into a fermentation chamber (1204), mixes these, and is performed at a temperature set for fermentation.

In the fermentation process, the pH drops with the production of lactic acid, so the fermentation liquid is adjusted to a neutral range (pH 6.5 to 7.5) using ammonia water. Therefore, it is preferable to provide a pH sensor or measuring device (not shown) and an ammonia water feeding device (not shown).

When the fermentation process is completed, lactic acid is accumulated in the fermentation liquid, and it is necessary to separate the lactic acid from the fermentation liquid. For this reason, in the above embodiment, a reticulated negative electrode (1202) is provided inside the fermentation chamber (1204) through the diaphragm, and the outside of the fermentation chamber (1204) is used as an anode. After being moved to the center of the apparatus by charging (indicated by-)), the lactic acid is discharged from the lactic acid concentrate outlet (1209) held by the electrically insulating frame (1210). As shown in FIG. 12, the electrically insulating mount (1210) is provided in the lower part of the fermentation chamber (1204), and a lactic acid concentrate outlet (1209) is provided at the center, and the fermentation chamber (1204) and the lactic acid concentrate outlet (1210) are provided. And a member made of an insulating material so as not to conduct electricity.

The temperature control of the fermentation liquid may be performed by an electric heater (not shown), a cooler (not shown) or the like. The control of the stirring is performed by a stirring device (1207) provided with a stirring rod (1213) having a stirring blade (1206, 1211). Temperature control and agitation control of the fermentation chamber (1204) can also be controlled automatically using a control system (not shown) such as a computer. In addition, the fermentation chamber (1204) may be a closed system, and may be pressurized or depressurized.

With regard to the shape and size of the stirring blade (1206, 1211), the purpose is to promote efficient generation / acquisition of lactic acid, which is the object of the present invention as well as the embodiment described above, and a sufficient stirring effect can be expected. It may be of any shape or size as long as it is.

Moreover, since foam may be generated during fermentation, a known antifoaming agent may be added as appropriate. If foam is generated during fermentation, it may be discharged from a foam discharge pipe (not shown) or may be discharged from a return pipe (1208).

In the above embodiment, an electrode or the like for electrically separating lactic acid produced by fermentation from a fermentation liquid is incorporated, but when separately separated after lactic acid fermentation, a fermentation liquid containing lactic acid from the fermentation chamber is It can also be taken out and separated separately by separation means. In that case, an electrode or the like for electrically separating lactic acid from the fermentation liquid in the above embodiment may be omitted.

FIG. 13 shows the structure of an electrodialysis apparatus (1301) according to the present invention, which is a longitudinal sectional view of the apparatus.

The electrodialysis apparatus (1301) of the present invention has a concentration of 10% to 20% sodium sulfate solution as an electrode solution in a positive electrode chamber (indicated as "A" in the figure) and a negative electrode chamber (indicated as "E" in the figure). It circulates in the same circulation circuit, and, for example, from the fermenter as shown in the fermentation chamber (1204) of FIG. 12 described above in the fermentation solution chamber (indicated as “B” in the figure), the filtered fermentation solution (1313) )).

In addition, fresh water (1314) is circulated to the lactate solution chamber and lactic acid solution chamber (indicated as "C" in the figure), and 0.1 N hydroxylated to the sodium hydroxide solution chamber (indicated as "D" in the figure). The sodium solution (1315) is circulated. In order to separate the lactic acid salt contained in the fermented liquid (1313), an auxiliary positive electrode (by 1304, according to the auxiliary positive chamber (indicated as "C" in the figure)) and an auxiliary negative electrode (1305, auxiliary negative chamber (in the figure, "D ) Is floated (not connected), and a direct current is applied between the positive electrode (1302) and the negative electrode (1303).

As described above, the control mechanism for passing a direct current between the positive electrode and the negative electrode with the auxiliary positive electrode and the auxiliary negative electrode in a floating (non-connected) state may be used without any problem as long as the device has a commonly used function. it can. For example, each electrode may be electrically connected and controlled by a computer system (not shown).

At this time, the hydroxide ion (indicated as "OH-" in the figure) in the fermented liquid (1313) in the fermentation liquid chamber (indicated as "B" in the figure) is a positive electrode room (indicated as "A" in the figure) And a positive electrode chamber (indicated as "A" in the figure) which permeates through a diaphragm (the diaphragm is formed of an anion permeable membrane (1317)) separating the fermentation liquid chamber (indicated as "B" in the figure). Moves to the electrode solution (1312, 1306) side, and hydrogen ions (H +) move from the electrode solution (1312, 1306) to the fermentation solution (1313) in the fermentation chamber (indicated as "B" in the figure). Do.

The lactic acid salt in the fermented liquid (1313) in the fermented liquid chamber (indicated as "B" in the figure) is a fermented liquid chamber (indicated as "B" in the figure) and a lactic acid solution chamber and a lactic acid solution chamber (indicated in the figure). , And "C") (the diaphragm is formed of a cation permeable membrane (1318)) to move toward the auxiliary positive electrode chamber (indicated as "C" in the figure). Also, sodium ions (Na +) and hydrogen ions (H +) move from the auxiliary positive electrode chamber (indicated as "C" in the drawing) to the auxiliary negative electrode chamber (indicated as "D" in the drawing), and the negative electrode chamber (Fig. Middle (denoted as “E”)) The hydroxyl ion (OH-) moves. As a result, the lactate salt is separated and concentrated in the lactate solution chamber and the lactic acid solution chamber (shown as "C" in the figure).

In addition, if the purpose of producing lactic acid (1308) by the electrodialysis apparatus (1301) of the present invention can be achieved for the above fresh water (1314), for example, ion exchange water etc. Water from which the components of

As described above, when the separation and concentration of the lactate is completed, the auxiliary positive electrode (1304) in the auxiliary positive electrode chamber (denoted "C" in the figure) and the auxiliary negative electrode (1305) in the auxiliary negative electrode chamber (denoted "D" in the figure). The auxiliary positive electrode chamber is moved from the lactate solution (1309) to the auxiliary negative electrode chamber (indicated as "D" in the drawing) from the lactate solution (1309) by direct current. The lactate solution (1309) (indicated as "C" in the figure) is a lactic acid solution. Sodium hydroxide (1310) concentrated in the auxiliary negative electrode chamber (indicated as "D" in the figure) can be used for neutralization of the fermentation solution in the fermentation process. Thus, the electrodialysis apparatus (1301) according to the present invention has the function of separating lactate from the fermented liquid (1313) and the function of decomposing the lactate into lactic acid (1308) and sodium hydroxide (1310). It is rational because one process can use only one electrodialysis apparatus, and equipment costs can be significantly reduced (for example, about half) in terms of equipment installation costs.

As described above, after the separation and concentration of the lactate is completed, the auxiliary positive electrode (1304) and the auxiliary negative electrode (1305) are subjected to a direct current to transfer sodium ions from the lactate solution (1309) to the auxiliary negative electrode chamber. The control mechanism for converting the lactic acid salt solution (1309) into a lactic acid solution can be used without any problem as long as it has an apparatus or the like that is normally used. For example, each electrode may be electrically connected and controlled by a computer system (not shown).

FIG. 14: is an example of the filtration separation apparatus (1401) for filtering the lactic acid fermented fermentation liquid and supplying a filtrate to an electrodialysis apparatus.

Fermented liquid is subjected to solid-liquid separation using a centrifuge (not shown), and in the case of a large facility, it is preferable to use a decanter. The supernatant is introduced into the filtration device (1401) shown in FIG. 14 and filtered by this separator. The filtration device (1401) is the supernatant liquid which has been centrifuged, and the separation liquid is first subjected to a large pore filtration cartridge (1402, 100 μm in FIG. 14), and then to a medium pore filtration cartridge (1403, 20 μm in FIG. 14). Finally, the small pore filtration cartridge (1404, 5 μm in FIG. 14) is sequentially passed through and filtered. Depending on the conditions and properties of the separation liquid, if you use four or five-stage filtration cartridges with different pore sizes as needed in addition to the three stages, or if the separation liquid is highly clear Alternatively, a two-stage filtration cartridge may be used. The separated liquid from the centrifuge may be transferred to a filtration device, or the filtrate may be transferred from the filtration device to the next step such as an electrodialysis device by using a pressure pump or the like.

The concentrated solution, viable bacteria, dead bacteria and other solid matter separated from the supernatant by the centrifugal separator as described above can be reused in the above-mentioned fermentation process.

Purification of Lactic Acid by Electrodialysis
The filtrate filtered and separated as described above can be further recovered as a sodium lactate solution by electrodialysis. As an apparatus therefor, an example of an electrodialysis apparatus for purifying lactic acid by electrodialysis in FIG. 15 and an example of an electrodialysis apparatus for purifying lactic acid by bipolar electrodialysis in FIG. 16 will be described.

FIG. 15 is an example of an electrodialysis (ED) apparatus for purifying lactic acid by electrodialysis.

The electrodialysis (ED) device involved in the compound separation shown in FIG. 15 has a cation permeable membrane at the center of the device, an anode on the left side of the device and a cathode on the right side, and the compound is electrodialyzed by energization. Be done.

As described above, the lactic acid solution separated by filtration exists as sodium lactate, and this is introduced into an electrodialysis (ED) apparatus and energized to conduct electricity from the side of the anode (indicated by "+" in the figure). It permeates through the cation permeable membrane and moves to the side of the cathode (indicated by "-" in the figure). After electrodialysis, the remaining solution is stored in the anode side container provided at the lower part of the device, and the water and lactic acid are stored in the cathode side container, and finally, a sodium lactate solution is obtained. This sodium lactate solution is introduced into the following bipolar electrodialysis (PD) device.

FIG. 16 is an example of a bipolar electrodialysis (PD) device that electrolyzes a sodium lactate solution obtained by an electrodialysis (ED) device to separate it into lactic acid and sodium hydroxide.

The bipolar electrodialysis (PD) according to the compound separation shown in FIG. 16 has an anion-permeable membrane on the left side of the central part of the apparatus and a cation-permeable membrane on the right side of the central part of the apparatus. The anode on the left side of the device (not shown), provided with cathode (not shown) on the right, of the sodium lactate solution by energizing, (in the figure, "CHCOOH ^-" and displayed) lactate ions anion permeable Sodium ions (indicated as "Na ⁺ " in the figure) pass through the cation-permeable membrane and move to the cathode side through the membrane to the anode side.

After energization, a solution of about 1% by weight of lactic acid initially becomes a lactic acid solution in a container provided on the left side of the lower part of the device, and this solution is used as a raw material for producing polylactic acid. In the container provided at the lower center of the apparatus, at first, the sodium lactate solution becomes a thin solution with the passage of time after energization, and this can be reused. In the container provided on the lower right side of the apparatus, a solution of about 1% by weight of sodium hydroxide initially becomes a sodium hydroxide solution with the passage of time after energization, and this can be reused.

The above-described electrodialysis apparatus according to the present invention will be described with reference to FIG. 17 as a comparison of the electrodialysis apparatus according to the present invention as an example of the conventional electrodialysis apparatus.

As shown in FIG. 17, a solution containing lactic acid (fermented liquid, shown as 1703 in FIG. 17) is introduced into the chamber of dialysis device 1 (1701) (the second chamber (b1) from the left in FIG. 17), This solution is circulated. Electrolyte (1705) is introduced into the respective chambers of dialysis device 1 (1701) and dialysis device 2 (1702) (in FIG. 17, right end (d1, d2) and left end chamber (a1, a2) of the respective devices). , This solution is circulated. Also, water (indicated as 1704 in FIG. 17) is introduced into the chamber (the second chamber (c1) from the right in FIG. 17) of the dialysis device 1 (1701), and separately the chamber (dialysis device 2 (1702)) At 17 the second chamber (c2) from the right is passed. When the separation and concentration of lactate is completed, the auxiliary positive electrodes (1709, 1711) on the left side of the respective chambers of the dialysis device 1 (1701) and the dialysis device 2 (1702) and the auxiliary negative electrodes (1708, 1710) on the right side of the respective chambers. The lactate solution in the auxiliary positive electrode chamber (c1) becomes a lactic acid solution by moving sodium ions from the lactate solution to the auxiliary negative electrode chamber (b2) through a direct current, and sodium hydroxide (1707) in the auxiliary negative electrode chamber (c2) ) Is concentrated. After concentration, the lactic acid solution is discharged from the chamber of dialysis device 2 (1702) (the third chamber (b2) from the right in FIG. 17), and the water is the chamber of dialysis device 2 (1702) (the right from FIG. 17). It is discharged from the second chamber (c2)).

As described above, the conventional electrodialysis apparatus is different from the apparatus of the present invention in that two apparatuses of the dialysis apparatus 1 (1701) and the dialysis apparatus 2 (1702) are required.

In the polylactic acid production step (v), the lactic acid obtained in the decomposition treatment step is concentrated by heating and dehydrating, and then it is further heated to produce polylactic acid. The lactic acid obtained in the decomposition treatment step is a crude lactic acid containing some other components. The crude lactic acid is heated and dewatered, but the heating temperature is preferably in the range of 120 ° C. to 130 ° C. After heating, dehydrating and concentrating, heating is performed again, and the temperature is in the range of 150 ° C. to 160 ° C. It is preferable to The lactic acid is concentrated by heating and dehydrating crude lactic acid, but the amount and rate of concentration may be suitably determined, in particular. Polylactic acid can be obtained by this process.

As a molecular weight of polylactic acid, it is preferable that the molecular weight and the like be determined according to the application, rather than simply having a high molecular weight. For example, when using it as the resin raw material for secondary batteries, resin is manufactured by metal complexing mixed lactide, ring-opening and polymerizing lactide. The molecular weight of the polylactic acid in this case is preferably 2,000 Da (dalton) to 20,000 Da, preferably 5,000 Da (dalton) to 10,000 Da.

Since lactic acid extracted and separated by the above-mentioned electrodialysis apparatus contains various organic acids, it is necessary to remove them and purify them into pure lactic acid. This process is called lactic acid purification process, and it has been conventionally performed by ion adsorption separation method or electrodialysis method that focuses on selective adsorptivity of ion exchange resin, but it takes time and effort in pre-treatment etc. There were restrictions such as having to do.

On the other hand, in the present invention, crude lactic acid is heated and stirred in a closed vessel to produce low molecular weight PLA (polylactic acid), and after slow cooling and solidification, it is reheated under reduced pressure to repel impurities. It has been found that the purity of lactic acid can be dramatically increased by As a result, the lactic acid purification work, which had conventionally taken a few dozen hours, was completed in several hours, and the work of the next step could be carried out continuously.

FIG. 17 is a schematic view showing the structure of a polymerization apparatus according to the present invention, and lactic acid purification, lactide formation, high molecular weight PLA (polylactic acid) polymerization, PLA (polylactic acid) purification and the like can be continuously performed.

FIG. 19 shows the structure of the polymerization apparatus according to the present invention.

FIG. 19 shows the structure of the polymerization apparatus (1901) of the present invention, and shows a cross-sectional view of the apparatus in the longitudinal direction. In the cross-sectional view, the left side of the center line represents the outer surface of the reaction vessel (1902) and the lid (1903) at the top of the reaction vessel, and the internal structure inside the reaction vessel is shown by a dotted line.

As shown in FIG. 19, the polymerization apparatus (1901) of the present invention comprises a reaction vessel (1902) and a lid (1903), a stirrer (1904), a jacket (1908, 1909), an electric heater (1910) and And a water-cooled condenser (1906) and an aggregation liquid reservoir (1907). In the polymerization apparatus (1901), the raw materials are charged into the reaction vessels (1902, 1903) from the raw material inlet (1911) and mixed. The contents after reaction are discharged from the contents outlet (1912).

The temperature control of the contents in the reaction vessel (1902, 1903) is conducted by transferring heat from the electric heater (1910) to the oil-filled jacket (1909) for heating and heating the reaction vessel (1902, 1903) to adjust the reaction temperature Therefore, the cooler (not shown) is controlled to a predetermined temperature by cooling the reaction vessel (1902, 1903) via the water cooling jacket (1908). The control of the stirring is performed by a stirring device (1904) provided with a stirring blade (1905). Temperature control and agitation control of the reaction vessels (1902, 1903) can also be automatically controlled using a control system (not shown) such as a computer.

In addition, the reaction vessels (1902, 1903) may be sealed systems, and may be pressurized or depressurized. Water vapor and the like generated by heating and stirring are condensed by a water-cooled condenser (1906) and can be stored in a condensate reservoir (1907). The condensate reservoir (1907) can be connected to a vacuum pump or the like to reduce the pressure.

With regard to the shape and size of the stirring blade (1905), the purpose is to promote efficient generation / acquisition of lactic acid, which is the object of the present invention as well as the embodiment described above, as long as sufficient stirring effect can be expected. It may be of any shape or size.

FIG. 18 is a control diagram of the lactic acid purification process of the present invention.

FIG. 18 shows a control diagram of the lactic acid purification process of the present invention. The horizontal axis (X axis) is the reaction time (minutes (min.)), And the vertical axis (Y axis) is the temperature in the reaction vessel (unit ° C.). The above control diagram will be described in chronological order for the case of using the polymerization apparatus of FIG.

First, after evaporating the water at 120 ° C to 130 ° C (denoted as "dehydration" in Fig. 18), the crude lactic acid extracted by the purification treatment using an electrodialysis apparatus etc. is further heated to 150 ° C to 160 ° C. The low molecular weight PLA (polylactic acid) is formed by stirring for 1 hour to 2 hours.

Then, the resultant is gradually cooled and crystallized (indicated as “cooling crystallization” in FIG. 18), whereby the organic acid other than lactic acid is separated. At this time, the stirring device may be stopped (indicated as “stopping stirring” in FIG. 18) to promote crystallization.

Then, for example, it is reheated under a reduced pressure environment of -20 mmHg to -50 mmHg with respect to atmospheric pressure (indicated as "reduced pressure" in FIG. 18) (indicated as "reheat melting" in FIG. 18) to transpiration impurities. It may be removed (indicated as "impurity transpiration" in FIG. 18).

In this series of operations, if the pressure in the reaction vessel is lowered excessively or the temperature of the contents in the reaction vessel is higher than 160 ° C., not only the impurities but also the transpiration of lactic acid increases, and the yield of purified lactic acid increases. Can get worse.

By this series of operations, the generation degree of lactic acid (yield of purified lactic acid) is as shown in FIG. 20 below.

As shown in FIG. 20, by heating and dewatering crude lactic acid, it is possible to discharge water of about 10% by weight to 15% by weight, and low molecular weight polylactic acid generated by heating and dehydration of crude lactic acid (“low molecular weight PLA in FIG. Can be discharged by heating approximately 5% by weight to approximately 6% by weight, and can be discharged by approximately 5% by weight to approximately 6% by weight by reheating and dehydrating, and 75% by weight to 80% by weight as purified lactic acid. The yield is about% by weight.

In the method for producing polylactic acid according to the present invention, in the above-described starch liquefying step (i), the mixing ratio of water to starch is 70 parts by weight to 80 parts by weight of water in the mixture of carbohydrate derived from plant and water. The starch content is preferably 30 parts by weight to 20 parts by weight.

Further, the mixture of sugar and water may be stirred by means of a container of suitable shape and stirring means such as a stirring blade. The number of rotations of stirring depends on the size and shape of the container, the stirring means such as the number and shape of stirring blades, but stirring may be performed, for example, at 70 rpm (times / minute) to 100 rpm (times / minute).

Then, it is preferable to gelatinize by heating to 90 ° C. to 105 ° C. while stirring, and stirring is continued for 15 minutes to 120 minutes after the temperature of the mixture of heated saccharide and water reaches 90 ° C. It is good to gelatinize.

After stirring as described above, starch derived from plant-derived L-lactic acid can be liquefied by heating at a predetermined temperature. The amount of L-lactic acid to be added may be 0.1% by weight to 1.0% by weight. After adding lactic acid, the temperature of the contents may be heated to 110 ° C. to 130 ° C., and stirring may be continued for 4 hours to 10 hours. Under such conditions, starch can be appropriately liquefied.

In the method for producing polylactic acid according to the present invention, the temperature of liquefied starch is adjusted to 50 ° C. to 65 ° C., and the hydrogen ion concentration (pH) is adjusted to 6.0 to 6.5 in the above-mentioned starch saccharification step (ii). Is preferred. It is a weakly alkaline solution for adjusting the pH, and it is preferable to use an aqueous ammonia solution so as not to suppress the activity of the saccharifying enzyme.

As a saccharifying enzyme used in saccharifying liquefied starch, one or two or more kinds of the above-mentioned enzymes may be used, and for example, amylase and the like can be used. The setting of the above temperature and pH can be appropriately set according to the optimum pH and heat resistance of the saccharifying enzyme to be used.

The amount of saccharifying enzyme to be used is not particularly limited as long as it achieves the purpose of the present invention, and for example, addition of 0.1% by weight to 1.0% by weight as a ratio to the amount of input starch is mentioned. If it is this range, a saccharification process will be performed appropriately. In the saccharification step, stirring is usually continued for 5 hours to 12 hours to carry out saccharification or monoglycation.

In the method for producing polylactic acid of the present invention, after adding sodium chloride, manganese sulfate, ammonium phosphate, skimmed milk powder, soy milk, waste molasses and surfactant to liquid sugar in the above-mentioned lactic acid fermentation step (iii) The mixture containing liquid sugar is fermented in the presence of plant-derived lactic acid bacteria to obtain lactic acid.

The amount of these materials used is, for example, a monosaccharide liquid having a sugar content of 20 or more and less than 30.
0.01 wt% to 0.1 wt% of sodium chloride,
0.01 wt% to 0.1 wt% of manganese sulfate,
0.01 wt% to 0.1 wt% of ammonium phosphate,
0.1% to 1.0% by weight of skimmed milk powder,
0.1% to 1.0% by weight of soy milk,
0.1% to 1.0% by weight of waste molasses,
0.01 wt% to 0.05 wt% of surfactant
It is good to be mixed in the range of

Furthermore, after mixing the above materials, the temperature of the mixture is adjusted to 50 ° C. to 65 ° C., the hydrogen ion concentration is adjusted to 6.5 to 7.0, and a suspension of activated lactic acid bacteria such as Lactobacillus Plantarum is used. Good to add.

The amount of plant-based lactic acid bacteria to be added may be 2% by weight to 5% by weight of a suspension having about 3 to 5 billion viable cells in 1 g of culture solution. With this number of bacteria, an adequate amount of lactic acid can be efficiently obtained by the culture carried out in the present invention.

Lactic acid fermentation is carried out in a suitable container containing the above-mentioned materials and plant-based lactic acid bacteria, but various conditions such as stirring at the time of fermentation include stirring by means of a container of suitable shape and stirring means such as a stirring blade Good. The number of rotations of stirring depends on the size and shape of the container, the stirring means, for example, the number and shape of stirring blades, but stirring is performed, for example, at 70 rpm (times / minute) to 100 rpm (times / minute) Stirring may be continued for lactic acid fermentation.

Furthermore, in the lactic acid fermentation step (iii), it is preferable to use a fermentation apparatus equipped with a mechanism for electrically concentrating lactic acid to be purified.

In the method for producing polylactic acid according to the present invention, the lactic acid is neutralized with sodium hydroxide to obtain a lactic acid salt in the above-mentioned decomposition treatment step (iv), and then the lactic acid salt is decomposed into lactic acid and sodium hydroxide. . It is because polylactic acid can be efficiently obtained by further decomposing after neutralization with sodium hydroxide.

Further, in the method for producing polylactic acid of the present invention, in the above-mentioned polylactic acid production step (v), after the lactic acid is concentrated by heating and dehydration, it is further heated to produce polylactic acid. In the lactic acid purification process, as various conditions such as stirring, it is preferable to stir using a container having an appropriate shape and a stirring means such as a stirring blade. The number of rotations of the stirring depends on the size and shape of the container, the stirring means, for example, the number and shape of the stirring blades, but it may be carried out by stirring at 70 rpm (times / minute) to 100 rpm (times / minute) .

More specifically, the content in the container is placed in a pressure-resistant container and crude lactic acid is put therein, and the temperature in the range of 120 ° C. to 130 ° C. is stirred, for example, at 70 rpm (rotations / minute) to 100 rpm (rotations / minute). After heating and dehydrating, stirring may be further continued at a temperature in the range of 150 ° C. to 160 ° C. for 1 hour to 2 hours to produce relatively low molecular weight polylactic acid.

After stopping the stirring, the product for internal use is cooled to normal temperature of about 25 ° C. to be crystallized, heated again to make the temperature in the range of 150 ° C. to 160 ° C., and the inside of the container is -20 mmHg to -50 mmHg against atmospheric pressure. The purified lactic acid can be obtained by evaporating the impurities by stirring at 70 rpm (times / minute) to 100 rpm (times / minute) for 1 hour to 2 hours.

Industrial application field

The present invention relates to a method and an apparatus for producing a lactic acid-based biodegradable plastic (PLA), and can provide convenience to the entire field of producing PLA (polylactic acid) using plant starch as a raw material. Moreover, the manufacturing apparatus of the present invention can provide convenience in the business field related to each apparatus.

According to the present invention, a method for producing polylactic acid capable of obtaining polylactic acid having a desired molecular weight with high efficiency and in a short time, and polylactic acid capable of obtaining polylactic acid with high efficiency and a sufficient molecular weight in a short time A manufacturing apparatus can be provided.

In addition, by using the method for producing polylactic acid of the present invention and the apparatus for producing polylactic acid, it is possible to continuously carry out from the production of lactic acid to the polymerization of polylactic acid, and also the miniaturization of equipment and low cost. It is also possible to simplify the operation, simplify the operation and reduce the manufacturing cost.

It is a figure which shows the chemical structure of the main component in the manufacturing flow of polylactic acid. It is the schematic which shows notionally the structure of the lactic acid manufacturing apparatus in a prior art. It is explanatory drawing of the manufacturing process of the polylactic acid in this invention. It is a figure which shows the manufacturing flow of the polylactic acid in this invention. It is a schematic diagram of the apparatus used for the starch saccharification process in the polylactic acid manufacturing method of this invention. It is a schematic diagram of the strain activation apparatus (an example) which processes a strain in order to use it for lactic acid fermentation. It is a schematic diagram of a hydrogen generator (an example) for producing hydrogen for using a strain for activation of a strain for fermentation. It is a schematic diagram of a container (an example) for fermenting using a strain. It is a schematic diagram of a fermenter (another example) for fermenting using a strain. It is a graph which shows a relationship with viable count and pH in the fermented liquid in the polylactic acid manufacturing method of this invention. It is an example of the method of determining the end point of the fermentation in the manufacturing method of the polylactic acid of this invention. It is another example of the method of determining the end point of the fermentation in the manufacturing method of the polylactic acid of this invention. It is sectional drawing which shows the structure of the fermentation apparatus provided with the lactic acid concentration mechanism in the manufacturing method of the polylactic acid of this invention. It is a structure of the electrodialysis apparatus of this invention, and an apparatus longitudinal cross-sectional view is shown. It is a schematic diagram of the filtration separation apparatus (an example) for filtering the fermentation liquid by which lactic acid fermentation was carried out in the manufacturing method of the polylactic acid of this invention, and supplying a filtrate to an electrodialysis apparatus. It is a schematic diagram of the electrodialysis (ED) apparatus (an example) which refines | purifies lactic acid by electrodialysis in the manufacturing method of the polylactic acid of this invention. Schematic diagram of bipolar electrodialysis (PD) apparatus (one example) for electrolyzing sodium lactate solution obtained by electrodialysis (ED) apparatus in the method for producing polylactic acid of the present invention to separate into lactic acid and sodium hydroxide It is. It is an example of the electrodialysis apparatus by a prior art, and an apparatus longitudinal cross-sectional view is shown. It is a control diagram of the lactic acid purification process of the present invention. The structure of the polymerization apparatus (an example) in the manufacturing method of the polylactic acid of this invention is shown. It is a figure which shows the yield of the refinement | purification lactic acid in this invention.

Hereinafter, the present invention will be more specifically described in the examples. However, the present invention is not limited to this.

The following equipment was used for analysis.
The sugar content was measured using a sugar scale.
The iodine reaction of starch was generally according to known procedures.
The molecular weight of poly (lactic acid) was measured using GPC (Gel Permeation Chromatography) by high performance liquid chromatography (Nippon Industrial Sales), calibrated with a standard polymer, and the molecular weight was measured. The formulation of the GPC measurement was performed based on the explanatory data of the apparatus used (eluent, column temperature: normally performed at normal temperature, detector: using a refractometer etc. for PLA detection). The column used was appropriately selected depending on the expected molecular weight of the sample to be measured.

Example 1
1. Production of Glucose from Starch The materials and formulations described below are for use in production in a 30 liter container, and if the shape and size of the production container are to be changed, the preparation amount etc. may be appropriately changed. Good.

1-1) Materials used Corn starch was used as a carbon source. Besides corn starch, potatoes, tapioca and the like can also be used.

Water used purified water. For example, ion exchange water, distilled water and the like can be used, and in the case of distilled water, trace metals may be added as needed.

The enzyme klytase (manufactured by Amano Enzyme Co., Ltd.) was used to hydrolyze starch. Chrysase contains α-amylase as a type of enzyme (Category). Depending on the grade, the properties of the enzyme α-amylase vary, but in the present invention, it can be applied if it is intended to liquefy the starch, for example, if it is that of Amano Enzyme Co., the krytase E5CC, the krytase SD8, the high temperature Use heat-resistant α-amylase containing klystase T10S for liquefaction of starch under some conditions, use klystase PL45 for degrading α-1, 6 glucosidic bond in the raw material molecule depending on the raw material, pullanase "Amano" 3 etc. Can. In this example, chrystase T10S was used.

Gluczyme (Amano Enzyme, which contains a degrading enzyme such as glycoamylase, in order to hydrolyze starch to a certain extent by the action of chrytase and hydrolyze the partially hydrolyzed starch (dextran) to glucose (glucosose) which is a monosaccharide Company company) was used. Gluczyme contains glycoamylase as a type of enzyme (Category). The nature of the enzyme glycoamylase varies depending on the grade, but in the present invention, any enzyme capable of hydrolyzing to glucose (glucos) which is a monosaccharide can be applied. For example, if it is Amano Enzyme's, Gluczyme AF6, Gluczyme NL4 2. Dizyme GPK (including glycoamylase and purners) for degrading α-1, 6 glucosidic bond in the raw material molecule can be used. Gluczyme AF6 (or Gluczyme NL 4.2) was used in this example.

Appropriate amounts of lactic acid and sodium hydroxide were used as pH adjusters.

1-2) Flow of glucose production from starch When starch is used as a raw material, it shows a flow of hydrolysis to glucose.
1) Put 25 liters of purified water into a 30 liter container.
2) Put the stirring blade from the stirring device into the container and stir at a rotational speed of 70 rpm to 100 rpm (around 50 Hz). In addition, the stirring apparatus may be previously integrated in the container.
3) While stirring is continued, 7 kg of starch (corn starch) as a raw material is added little by little to the container, and the stirring is further continued.
4) While stirring, check the pH of the solution in the container, and adjust it with sodium hydroxide (NaOH) so that the pH is 6.0 or near.
5) Transfer the container to a heating device and heat it. In addition, a heating apparatus may be previously integrated in the container.
6) Check the temperature of the solution in the container and maintain the stirring speed until the solution temperature reaches 70 ° C. (around 50 Hz). When the liquid temperature reaches 70 ° C., the stirring speed is set to be slow (around 30 Hz).
7) When the solution temperature reaches 95 ° C, continue stirring for 10 minutes to 15 minutes.
8) While stirring, add 20 g of klytase powder little by little to the vessel and continue stirring. It takes about 1 minute to put in the whole powder of chrystase.
9) Increase the stirring speed to a rotational speed of 70 rpm to 100 rpm (around 50 Hz) and stir for 1 hour. At this time, it is preferable to scrape off the saccharified starch attached to the rotating shaft or the like.
10) Confirm that the input in the container is totally liquefied.
11) Measure the sugar content of the solution in the container. Confirm that the sugar content is around 25 °.
12) Take a part of the solution in the container and perform the iodine reaction. Make sure that there is no color change in the iodine reaction.
13) Cool to lower the liquid temperature in the container. In addition, a cooling device may be previously integrated in the container.
14) While stirring is continued, slowly add 20 g of gluclime (liquid) into the vessel little by little and continue the stirring. It takes about 1 minute to put all the liquid gluclime in.
15) While stirring, set the temperature of the solution in the vessel to 60 ° C.
16) Check the pH of the solution and adjust it with sodium hydroxide (NaOH) so that the pH is at or near 6.5.
17) Continue stirring for about 2 hours at a rotational speed of 70 rpm to 100 rpm (near 50 Hz).
18) Measure the sugar content of the solution in the container. Check that the sugar content is 25 ° or more.
According to the above formulation, glucose was produced using starch as a raw material.

1-3) Preparation of lactic acid bacteria Using glucose produced from starch, it is fermented from lactic acid bacteria to produce lactic acid.

The lactic acid bacteria used for lactic acid fermentation include the above-mentioned strains, but in the examples, it is necessary to activate the strains. In order to activate, the following materials and devices are used, and the activation process is performed by the strain activation apparatus shown in FIG.

The following was used as an apparatus and material used for adjustment of lactic acid bacteria.
・ Dry lactic acid bacteria strain (Lactobacillus (Lactobacillus (Lactobacillus) Plantarum species)
Glucose (obtained by the above prescription)
-Containers such as wide-mouthed bottles (502 in FIG. 5, hereinafter referred to as "wide-mouthed bottles") and lids (503 in FIG. 5)
・ VRB extract peptone petri dish (504 in Fig. 5)
· Manganese sulfate · salt · molasses (can be made inexpensive by using waste molasses)
· Hydrogen generator (using the one described in Fig. 6)

FIG. 6 is an example of a hydrogen generator used to activate a lactic acid bacteria strain. The lactic acid fermentation strain was activated in hydrogen gas at a temperature of 45 ° C. and a relative humidity (RH) of 95%, and the environmental conditions were maintained for 24 hours.

1-4) Lactic acid fermentation Since glucose generated from starch through gelatinization, liquefaction and saccharification steps usually has a sugar content of about 23-25 °, it is further boiled down to obtain liquid sugar with a sugar content of about 50 °. It manufactured and used this as the material for lactic acid fermentation.

The culture components for lactic acid fermentation had the following composition. These components were charged into a fermenter and fermented.
Glucose solution (sugar content 50 °) 1 liter Soy peptone 50 g
・ Manganese sulfate 1 g
・ 1 mol of molasses
・ 2g of salt
・ VRB extract 10g
・ Lactic acid (for pH adjustment) Appropriate amount ・ Active lactic acid bacteria strain

When fermentation was carried out by shaking culture method, it was carried out in a clean bench to prevent contamination. The culture conditions were at 37 ° C. for about 24 to 30 hours. The end point of the culture was determined while monitoring the relationship between the number of viable cells in the culture solution and pH as shown below.

Dextrose with a sugar content of about 50 ° is put into the fermenter of the fermenter to which the above culture solution components have been added, and culture is carried out by stirring at low speed under the conditions of 37 ° C to 38 ° C and pH 6.5 to 7.0. The The inoculum size of the active lactic acid bacteria strain was one liter as a cultured solution.

The culture broth composition was as follows.
Glucose solution (sugar content 50 °) 1 liter soy peptone 500 g
・ Waste molasses 500g
・ One liter of cultured strain solution

As culture conditions, pH 6.5 to 7.0 and stirring were performed at 30 Hz.

During the culture, a part of the culture solution was collected to measure the pH, and the relationship with the number of viable cells was confirmed to determine the end point.

The culture was terminated when the number of viable bacteria of the lactic acid bacteria strain was 700 million cells (Cell) / ml-culture solution to 1 billion cells (Cell) / ml-culture solution.

1-5) Filtration and Separation of Lactic Acid Solution Although lactic acid is produced in the lactic acid-fermented fermentation solution as described above, it is necessary to efficiently separate the fermentation solution and the lactic acid. As a device therefor, the filtration and separation of the milk lactic acid solution was performed by the filtration separation device of FIG. In the filtration separation device of FIG. 14, as a filtration cartridge, filtration was performed in the order of 100 μm size → 20 μm size → 5 μm size.

1-6) Purification by Electrodialysis of Lactic Acid The filtrate filtered and separated as described above can be further collected by electrodialysis as a sodium lactate solution. As a device therefor, the lactic acid was purified by the electrodialysis apparatus for purifying lactic acid by the electrodialysis of FIG. 15 and the bipolar electrodialysis of FIG.

1-7) Synthesis of Polylactic Acid Using a polymerization apparatus having a tubular polymerization tank and an electric dehydration tank shown in FIG. 18, lactic acid was produced according to the following procedure.

(1) Drying step 0.5 parts by mass of obtained 99.5 parts by mass of lactic acid having a concentration of 20% and a catalyst (a mixture of ruthenium oxide and titanium oxide at a mass ratio of 50% by mass) and a stirrer (1904) The mixture was stirred at 150 rpm for 10 minutes. At this time, the pH of the mixture was about 3.5 to 4 and the temperature was 90.degree. The resulting mixture was then evaporated to dryness at 110-120 ° C. for 0.5 hours. At this time, the concentration of lactic acid was approximately 60% by mass.

(2) Polymerization / Dehydration Step While using the polymerization apparatus (1901) shown in FIG. 18, the mixture of the obtained lactic acid and the catalyst is circulated between the polymerization tank and the electric dehydration tank at 10 mass% per minute, 240 Polymerization and dehydration were performed for a minute. At this time, in the electrodehydration tank, dehydration was conducted by causing a direct current to flow through the polylactic acid at an electroosmotic voltage of 4.8 V between the electrodes. The temperature of the polymerization tank was 140 to 145 ° C. for the first 90 minutes, and 115 to 120 ° C. for the remaining 150 minutes. It was about 10,000 Da when the weight average molecular weight of the obtained polylactic acid was measured using GPC (gel permeation chromatography) by high performance liquid chromatography.

401 starch saccharification device 402 saccharification reaction tank 403 stirring device 403a stirring blade 403b stirring rod 404 jacket 405 condenser material inlet 407 electric heater 408 condensation liquid reservoir 409 content outlet 501 strain activation device 502 wide mouth bottle 503 lid 504 cylindrical container 504a Peptone and dried strain 505 Containing water in cotton wool 506 Temperature control heater 507 Constant temperature bath 508 Water temperature 509 Thermometer 510 Tube for introduction 511 Exhaust tube 512 Mounting frame 601 Hydrogen generator 602 Heating element 603 Container 603 a Lid 604 Sodium hydroxide Aqueous solution 605a Rubber tube 605b Rubber tube 606 Mounting frame 607 Container 608 Negative electrode 609 Positive electrode 610 Lid 611 Tube 612 Inlet 613 Discharge port 701 Container 702 Lid 703 Material for culture 801 Fermentation equipment 802 Fermentation tank 802 Alkaline tank 804 Jacket 805 Stirring equipment 806 Fermentation tank inlet 807 Discharge port 1201 Fermentation equipment 1202 Negative electrode 1203 Heat retention jacket 1204 Fermentation chamber 1205 Diaphragm 1206 Stirring blade 1207 Stirring device 1208 Return pipe 1209 Lactate concentrate outlet 1210 Electrical insulating frame 1211 Stirring blade 1212 Power source 1213 Stir bar 1301 Electrodialysis device 1302 Positive electrode 1303 Negative electrode 1304 Auxiliary positive electrode 1305 Auxiliary negative electrode 1306 Electrode liquid 1307 Desalting liquid 1308 Lactate 1309 Lactate Solution 1310 Sodium hydroxide solution 1311 Electrode solution 1312 Electrode solution 1313 Fermentation liquid 1314 Fresh water 1315 0.1 N sodium hydroxide solution 1316 Electrode liquid 1317 Anion permeable membrane 1318 Cation permeable membrane 1401 Filtration device 1402 Filtration cartridge (large pore)
1403 filtration cartridge (hole)
1404 filtration cartridge (small hole)
1701 Dialysis machine 1
a1 chamber of the dialysis device 1 b1 chamber of the dialysis device 1 c1 chamber of the dialysis device 1 d1 chamber of the dialysis device 1 1702 dialysis device 2
a2 Room 2 of dialyzer 2 Room 2 of dialyzer 2 Room 2 of dialyzer 2 Room 2 of dialyzer 2 1703 Fermented liquid 1704 Water 1705 Electrolyte 1706 Lactic acid 1707 Sodium hydroxide 1708 Auxiliary negative electrode 1709 Auxiliary positive electrode 1710 Auxiliary negative electrode 1711 Auxiliary positive electrode 1901 polymerization apparatus 1902 reaction vessel 1903 lid (reaction vessel)
1904 Stirring device 1905 Stirring blade 1906 Water-cooled condenser 1907 Condensate reservoir 1908 Water-cooled jacket 1909 Oil-filled jacket 1910 Electric heater 1911 Raw material inlet 1912 Content outlet

Claims (9)

1. A method for producing polylactic acid, which comprises combining the following steps (i) to (v);
   (I) A starch-liquefying process in which a mixture of carbohydrates derived from plants and water is heated to gelatinize the mixture of carbohydrates and water, and further lactic acid is added and steamed to be liquefied;
   (Ii) a starch saccharification step of obtaining liquid sugar by causing a saccharifying enzyme to act on the liquefied starch obtained in (i);
   (Iii) A lactic acid fermentation step of obtaining lactic acid by fermenting the liquid material obtained in (ii) with the material for fermentation after adding and mixing it to a mixture containing liquid sugar in the presence of the fermentation strain,
   (Iv) a decomposition treatment step of decomposing the lactic acid salt into lactic acid and sodium hydroxide after the lactic acid obtained in (iii) is neutralized with sodium hydroxide to obtain a lactic acid salt;
   (V) A polylactic acid production step of heating and dehydrating the lactic acid obtained in (iv), and then heating to generate polylactic acid.
2. In the starch liquefaction step (i), the mixture ratio of water and starch in the mixture of plant-derived saccharide and water is 30 parts by weight to 20 parts by weight of starch to 70 parts by weight to 80 parts by weight of water. Item 2. A method for producing polylactic acid according to Item 1.
3. The polylactic acid according to claim 1 or 2, wherein in the starch saccharification step (ii), the temperature of liquefied starch is adjusted to 50 ° C to 65 ° C, and the hydrogen ion concentration (pH) is adjusted to 6.0 to 6.5. Production method.
4. In the lactic acid fermentation step (iii), after adding and mixing sodium chloride, manganese sulfate, ammonium phosphate, skimmed milk powder, soy milk, waste molasses and surfactant to liquid sugar in the presence of vegetable lactic acid bacteria in a mixture containing liquid sugar The method for producing polylactic acid according to any one of claims 1 to 3, wherein lactic acid is obtained by fermenting at
5. The decomposition treatment step (iv) according to any one of claims 1 to 4, wherein the lactic acid salt is decomposed into lactic acid and sodium hydroxide after the lactic acid is neutralized with sodium hydroxide to obtain a lactic acid salt. Method of polylactic acid.
6. The method for producing polylactic acid according to any one of claims 1 to 5, wherein in the polylactic acid production step (v), the lactic acid is concentrated by heating and dehydrating, and then heating is further carried out to produce polylactic acid. .
7. An apparatus used for the method for producing polylactic acid according to any one of claims 1 to 6,
   The device is a sealable device comprising a saccharification reaction tank, a stirring device, a jacket and a condenser.
   The saccharification reaction tank is provided with a raw material inlet for charging raw material starch and water, and an outlet for discharging liquefied starch, and the charged raw material starch and water are heated and stirred in the saccharification reaction tank After being gelatinized, it is a reaction vessel for adding L-lactic acid, stirring, heating and liquefying it,
   The stirring device is provided with a stirring blade in the saccharification reaction tank via a stirring rod, and the raw material starch and water introduced into the saccharification reaction tank are mixed by rotating the stirring rod at a predetermined speed by the stirring device. A device for
   The jacket is disposed around the periphery of the saccharification reaction tank, and comprises an oil-filled jacket provided with a water cooling jacket for cooling the saccharification reaction tank and an electric heater for heating the saccharification reaction tank below; A device to control the temperature of the
   The condenser is an apparatus for aggregating gas components generated by heating the raw material starch and water in the saccharification reaction tank.
   Poly lactic acid production equipment.
8. An apparatus used for the method for producing polylactic acid according to any one of claims 1 to 6,
   The device is a sealable device comprising a fermentation chamber, a stirring device, a heat retaining jacket, a mesh negative electrode, and an electrically insulating mount.
   The fermentation chamber is a container for charging liquid sugar, lactic acid bacteria and additives which are materials for fermentation, mixing and performing at a temperature set for fermentation,
   The stirring device is provided with a stirring blade in the fermentation chamber via a stirring rod, and is a device for mixing the fermentation material introduced into the fermentation chamber by rotating the stirring rod at a predetermined speed by the stirring device. Yes,
   The heat insulating jacket is a member provided on the outer periphery of the fermentation chamber to keep the fermentation chamber warm,
   The reticulated negative electrode is provided in the fermentation chamber via a diaphragm, and the lactic acid produced by fermentation is transferred to the center of the apparatus by charging the outside of the fermentation chamber as an anode, and the lactic acid produced by the fermentation is discharged from the lactic acid concentrate outlet. A device for discharging,
   The electrically insulating mount is a member provided at the lower part of the fermentation chamber, provided with a lactic acid concentrate outlet at the center, and made of an insulating material so that the fermentation chamber and the lactic acid concentrate outlet do not conduct electricity.
   Poly lactic acid production equipment.
9. An apparatus used for the method for producing polylactic acid according to any one of claims 1 to 6,
   The apparatus is an electrodialysis apparatus including a positive electrode chamber, a fermentation liquid chamber, an auxiliary positive electrode chamber, an auxiliary negative electrode chamber, and a negative electrode chamber,
   In the positive electrode chamber, a sodium sulfate solution is circulated and connected to the positive electrode so that current can be supplied to the negative electrode.
   In the fermentation chamber, a fermentation solution containing lactate is circulated.
   In the auxiliary positive electrode chamber, fresh water is circulated and connected to the auxiliary positive electrode so that the auxiliary negative electrode can be energized.
   The auxiliary anode chamber is circulated with sodium hydroxide solution and connected to the auxiliary anode so that electricity can be supplied from the auxiliary cathode.
   In the negative electrode chamber, a sodium sulfate solution is circulated and connected to the negative electrode so that current can be supplied from the positive electrode.
   Between the positive electrode chamber and the fermentation liquid chamber, an anion exchange membrane diaphragm is provided on the positive electrode chamber side, and a cation exchange membrane is provided on the fermentation liquid chamber side.
   A cation exchange membrane is provided between the fermentation liquid chamber and the auxiliary positive electrode chamber,
   A cation exchange membrane is provided between the auxiliary positive electrode chamber and the auxiliary negative electrode chamber,
   Between the auxiliary negative electrode chamber and the negative electrode chamber, an anion exchange membrane diaphragm is provided on the auxiliary negative electrode chamber side, and a cation exchange membrane is provided on the negative electrode chamber side.
   There is provided a mechanism capable of controlling so that a direct current is supplied between the positive electrode and the negative electrode without connecting the auxiliary positive electrode and the auxiliary negative electrode when separating a lactate from the fermentation liquid.
   Poly lactic acid production equipment.

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