JPH10313887A - Production of lactic acid from organic waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently obtain lactic acid that is useful in the fields of chemistry and food products in high concentration and selectivity by adding proper levels of saccharides and water to a specific organic waste and allowing a microorganism to act thereon. SOLUTION: Nitrogen-containing organic wastes comprising one or more of garbage from kitchen, waste from food factories, unutilized organic resource or excessive sludge are combined with suitable amounts of saccharides such as glucose and water. Further, the temperature, pH and the dissolved oxygen concentration are controlled, and a lactic acid bacterium or a combination thereof with a microorganism that can assist the activity of the lactic acid bacterium is allowed to act thereon thereby producing lactic acid. In addition to the microorganisms, lactobacillus-fermented sludge refuse and/or excessive sludge are preferably admixed to the fermentation mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to homes, apartments,
The present invention relates to a method for producing lactic acid from organic waste discharged from hotels, restaurants, catering industry, municipalities, food industry, alcoholic beverage industry, dairy industry, waste liquid treatment sludge, and the like.

[0002]

2. Description of the Related Art At present, organic waste discharged from households, apartment houses, hotels, restaurants, catering industry, municipalities, food industry, liquor and beverage industry, dairy industry, waste liquid treatment sludge and the like containing various effective resources is known. It is mainly treated by incineration, landfill and ocean dumping. Also, in some cases, a method has been proposed in which compost (compost) or livestock feed is not directly discarded and recycled. On the other hand, a technique for producing a desired organic acid by appropriately mixing organic waste has also been developed.

[0003]

However, when treating organic waste by landfill, there is a problem of lack of landfills, and incineration requires large facilities.
Further, there is a problem that an odor is generated. In addition, the method of recycling organic waste as compost or feed requires a long processing time, because of the imbalance between these demands and the amount of organic waste to be treated, and low added value.
Not a valid solution.

On the other hand, lactic acid has a great demand in the chemical and food industries as a raw material for various useful substances or as a component for process treatment, and can be used as a raw material for biodegradable plastics which are decomposed in the natural environment. Therefore, reduction of the production cost is eagerly desired. However, in the method of producing an organic acid from existing organic waste, it is necessary to mix the composition of organic components such as garbage so as to be a component suitable for the production of an organic acid. If organic waste with no composition is discharged as garbage,
There was a problem that lactic acid could not be produced from this alone. The present invention has been made in view of the above circumstances, and is a method for efficiently producing lactic acid that can be used as a raw material for biodegradable plastics from a large amount of organic waste that is discarded. The aim is to provide a method.

[0005]

According to the present invention, there is provided a semiconductor device comprising:
The method for producing lactic acid from the organic waste described is garbage,
Add appropriate sugars and water to organic waste containing one or two or more wastes from food factories, unused organic resources, or excess sludge and containing nitrogen to allow microorganisms to act. Lactic acid is produced at a high concentration and with high selectivity. The method for producing lactic acid from organic waste according to claim 2 comprises one or more of garbage, waste from food factories, unused organic resources, or excess sludge, and contains nitrogen. It is characterized by adding moderate amount of carbohydrate and water to organic waste, and furthermore, by controlling the temperature, pH and dissolved oxygen concentration, the microorganisms act to produce lactic acid with high concentration and high selectivity. And Here, adding a suitable amount of carbohydrate and water, and further causing the microorganism to act while controlling the temperature, pH, and dissolved oxygen concentration means that conditions suitable for the activity of the microorganism include carbohydrate, water, temperature, and pH. And controlling the dissolved oxygen concentration.

According to a third aspect of the present invention, there is provided a method for producing lactic acid from organic waste, wherein the microorganisms include a lactic acid bacterium or a lactic acid bacterium and a bacterium which assists the activity of the lactic acid bacterium. Here, bacteria that help the activity of lactic acid bacteria
For example, it refers to bacteria that contribute to lactic acid fermentation such as hydrolytic bacteria.

[0007] The method for producing lactic acid from organic waste according to claim 4 is a method for producing lactic acid from one or more of garbage, waste from food factories, unused organic resources, and excess sludge. Of organic waste A containing glucose, saccharide B such as glucose, sucrose and starch, and water C as follows: A = (1-10) × B, C = (0.3-5) × ( A +
B) at a weight ratio of (B), keeping the temperature from room temperature to 55 ° C., and maintaining the pH above 3 to 12 and below, and appropriately maintaining the anaerobic state, and removing microorganisms that naturally adhere to the organic waste. Lactic acid is produced at a high concentration and selectively. Here, the organic waste is calculated as a wet weight containing water.
To the organic waste A, a sugar B such as glucose, sucrose, starch, etc. and water C were added [A = (1-1)
0) × B] means that the organic waste is added to the organic waste at a ratio of 1 to 10 with respect to the sugar 1 by weight. This is uneconomical if the organic waste is less than 1 per carbohydrate, and the activity of lactic acid bacteria is worsened. If it is more than 10, the activity of lactic acid bacteria is greatly reduced and the concentration of Because the production of lactic acid can no longer be expected,
It is preferable to use 3 to 8 organic wastes per carbohydrate. Further, the weight ratio of [C = (0.3-5) × (A + B)] is defined assuming that the total weight of the organic waste and the saccharide is 1,
It means to contain 0.3 to 5 times water. This is because if the water content is less than 30%, the water activity of the lactic acid bacteria is lost, and if the water content is more than 5 times, there is a problem that other bacteria grow. It is preferable to increase the water content by 0.5 to 3 times, and water or a water-soluble solution is added to compensate for the shortage.

Further, to maintain the temperature from room temperature to 55 ° C., to maintain the pH above 3 and below 12 and to appropriately maintain the anaerobic state, and to appropriately act on microorganisms to produce lactic acid means that It is to prepare conditions suitable for the activity of lactic acid bacteria, and it is preferable to control the temperature of the atmosphere liquid to the range of normal temperature to 55 ° C, more effectively 20 ° C to 50 ° C. Also, maintaining the pH above 3 and below 12 is due to the pH
When the pH is 3 or less, or when the pH exceeds 12, the acidity or alkalinity of the atmosphere liquid is too strong, and the activity of the microorganisms is reduced or killed. The pH is adjusted to a condition suitable for the activity of the microorganisms. It is preferable to adjust the pH to 5 to 1
It is more preferable to control the value in the range of 0. In addition, to maintain the anaerobic state appropriately here, in addition to adjusting the ventilation and anaerobic state to make it mainly anaerobic state suitable for the activity of lactic acid,
This includes maintaining anaerobic conditions. The microorganism that naturally adheres to the organic waste is a microorganism that naturally adheres to and mixes with the organic waste without any special addition of bacteria.
For example, various lactic acid bacteria, hydrolytic bacteria, various bacteria such as acid-producing bacteria that produce acids other than lactic acid are present attached to organic waste, and by setting conditions suitable for lactic acid fermentation, Highly selective and high-concentration lactic acid fermentation can be performed without adding bacteria. Specifically, for example, Corynebacterium, Lactobacillus, Lamibacterium, Actinomyces, Bifidobacterium, Bacillus (Babacillus)
C., micrococcus (Micrococc)
), Pseudomonas and the like, and many of them have both functions of hydrolysis and acid generation.

The method for producing lactic acid from organic waste according to claim 5 is a method for producing lactic acid according to claim 4,
A lactic acid bacterium and / or a bacterium that assists the activity of the lactic acid bacterium is added to the microorganism. The method for producing lactic acid from organic waste according to claim 6 is the method for producing lactic acid according to any one of claims 1 to 5, wherein, in addition to the microorganisms, lactic acid-fermented sludge and / or Alternatively, surplus sludge is introduced. This is because, for example, organic waste with very few bacteria that are naturally attached and mixed, such as those sent directly from factories online, are lactic acid bacteria, hydrolytic bacteria, a mixture of lactic acid bacteria and hydrolytic bacteria, Alternatively, it means that lactic acid-fermented sludge slag and / or surplus sludge, which are often found in the generation of bacteria, are introduced to further adjust the conditions of lactic acid fermentation. In the method for producing lactic acid according to claims 1 to 6, the saccharide is a monosaccharide such as glucose, sucrose, and starch;
Any sugars such as oligosaccharides and polysaccharides can be used.
This is because organic waste is used as a material for producing lactic acid, and not only lactic acid bacteria but also various bacteria such as hydrolytic bacteria naturally adhere to and mix with organic waste. This is because even polysaccharides are decomposed by hydrolytic bacteria and contribute to activation of lactic acid bacteria. However, lactic acid bacteria, hydrolyzing bacteria, or lactic acid-fermented sludge and / or excess sludge, which often generate bacteria, are used for organic wastes that have very few bacteria attached and mixed naturally. It is preferred that the lactic acid fermentation conditions be adjusted to make the lactic acid fermentation work.

In claims 1 to 6, high concentration of lactic acid means 10 g / L or more, and high selectivity means that the ratio of lactic acid per organic acid is 80% or more. Further, the organic waste containing nitrogen means that when the organic waste does not contain nitrogen, 1 to 5% of nitrogen is added to the organic waste. Nitrogen can be contained by introducing other organic waste containing, fermented lactic acid fermented sludge and / or excess sludge. This is because in the absence of nitrogen, the activity of the lactic acid bacterium is greatly reduced, and the production of high-concentration lactic acid cannot be expected. Here, the unused organic resources are not used,
Alternatively, it refers to organic resources that have been used but have been discarded in a valuable state.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a method for producing lactic acid from organic wastes. Hereinafter, experimental examples performed to confirm the operation and effects of the method for producing lactic acid of the present invention will be described. . In the experiment, a mixture of bonito soup cake and kelp soup cake, which is an example of organic waste from a food factory and also an unused organic resource, a mixture of bonito soup cake and shiitake soup cake, and red bean shell were used as samples. Was done. In addition, an experiment was performed using rice shochu waste liquid lees, potato shochu waste liquid lees, and beer wort lees from a beer factory as examples of wastes from a brewery. Furthermore, an experiment was conducted using a sample of excess sludge originating from a wastewater treatment pond of a milk factory, which is an example of excess sludge. In order to examine the effect of the addition of carbohydrates in the method of the present invention, in Experimental Examples 1, 2, and 3, glucose, which is a monosaccharide, sucrose, which is a disaccharide, and polysaccharide, were used as organic carbohydrates. And a case where no carbohydrate was added was compared and examined. Further, a case in which water was contained more than 5 times the total of the organic waste and the saccharide was examined in Experimental Example 6. Furthermore, as a bacterium acting on organic waste, it is not a bacterium which naturally adheres to and mixes with organic waste, but is a lactic acid bacterium, Lactobacillus delbrueque, which is widely used industrially.
Comparative study was also carried out in Experimental Example 7 in the case where illus delbrueckii) was allowed to act.

(Experimental Example 1) 2% to 20% of one-to-one organic waste from a food factory, bonito and kelp
The soup stock obtained after adding water and boiling to remove the soup was used as a sample. To 8 g of the dashi cake, glucose, sucrose and starch were added in an amount of 2 g each, and 3 types of 10 g each were added.
g, add water to a 50 ml centrifuge tube, and add
The fermentation was carried out in a constant temperature bath at 0 ° C. Initial pH is 10 and 12
The pH was returned to 10 every hour. After 72 hours of fermentation, the centrifuge tube was centrifuged to precipitate solids, and the liquid phase was recovered.
The lactic acid concentration in the liquid phase was measured.

[0013]

[Table 1]

As shown in Table 1, lactic acid is produced in a high concentration and in a high selectivity from the addition of glucose, sucrose, and starch, and the comparative example in which no sugar is added. Shows that almost no lactic acid is formed.

(Experimental Example 2) Dashi after removing the soup by adding water to 2 to 20% and adding water so as to make it 2 to 20%, which is an organic waste from a food factory. Cake was used as a sample. Glucose, sucrose, and starch were added to 8 g of this dashi cake, respectively, and 2 g of each was added, and 3 types of 10 g were added to each, and 4 types of solid samples of only 10 g of dashi cake without adding carbohydrate were each added to a total of 30 g. Iodine water was added, put in a 50 ml centrifuge tube, and fermented in a thermostat at 37 ° C. Initial pH 10
And the pH was returned to 10 every 12 hours. After 72 hours of fermentation, the centrifuge tube was centrifuged to precipitate solids, then the liquid phase was recovered, and the lactic acid concentration in the liquid phase was measured.

[0016]

[Table 2]

As shown in Table 2, the lactic acid was produced in a high concentration and in a highly selective manner from the addition of any of the carbohydrates of glucose, sucrose, and starch. Shows that almost no lactic acid is formed.

(Experimental Example 3) Red bean husk, which is an organic waste from a food factory processed for producing bean paste, was used as a sample. For 8 g of this red bean shell, glucose,
Sucrose and starch were added in 2g each, 3g each in 10g, and 10g red bean hull without sugar
Water was added to each of the four solid samples to a total of 30 g, placed in a 50 ml centrifuge tube, and fermented in a 37 ° C. thermostat. The initial pH was set to 10, and the pH was returned to 10 every 12 hours. After 72 hours of fermentation, the centrifuge tube was centrifuged to precipitate solids, then the liquid phase was recovered, and the lactic acid concentration in the liquid phase was measured.

[0019]

[Table 3]

As shown in Table 3, in this experimental example using red bean husks as the organic waste, although the amount of lactic acid produced was smaller than in other experimental examples, the red bean husk used as the organic waste was used. Is thought to be due to the low nitrogen content. Nevertheless, the amount of lactic acid is 10 g / l in comparison with the other organic acids produced, acetic acid, propionic acid and formic acid, from the addition of glucose, sucrose and starch.
As described above, it is selectively generated at a high concentration of 10 times or more. On the other hand, lactic acid was hardly produced from the comparative example to which no saccharide was added.

(Experimental Example 4) A suspended solid content of rice shochu waste liquid lees was used as a sample. To 8 g of the rice shochu lees, 2 g each of glucose, sucrose, and starch were added, and water was added to each of the three types of solid samples, each of which was 10 g, to a total of 30 g. The fermentation was carried out in a constant temperature bath at 0 ° C. The initial pH was set to 10, and the pH was returned to 10 every 12 hours. After 72 hours of fermentation, the centrifuge tube was centrifuged to precipitate solids, then the liquid phase was recovered, and the lactic acid concentration in the liquid phase was measured.

[0022]

[Table 4]

As shown in Table 4, in this experimental example using rice shochu slag, the amount of lactic acid produced was smaller than in the other experimental examples. Can be Nevertheless, even if glucose, sucrose or starch is added, lactic acid is more than 10 g / l and more than 10 times as much as acetic acid, propionic acid, formic acid and butyric acid, which are other organic acids produced. It can be seen that it is produced with high concentration and high selectivity.

(Experimental Example 5) A suspended solid content of potato shochu waste liquid lees was used as a sample. To 8 g of this shochu lees, 2 g each of glucose, sucrose, and starch were added, and water was added to each of the three types of solid samples of 10 g each so that the total amount became 30 g. Fermentation in a thermostat. The initial pH was set to 10, and the pH was returned to 10 every 12 hours. After 72 hours of fermentation, the centrifuge tube was centrifuged to precipitate solids, then the liquid phase was recovered, and the lactic acid concentration in the liquid phase was measured. As shown in Table 5, it can be seen that lactic acid was produced at a high concentration and with high selectivity, regardless of the type of saccharide added.

[0025]

[Table 5]

(Experimental Example 6) Next, an experiment was conducted in which the content of water was changed using a suspended solid content of potato shochu waste liquid lees as a sample.
To 2 g of shochu lees, add 0.3 g each of glucose, sucrose, and starch, and add water to each of the three types of solid samples of 2.3 g each so that the total amount becomes 30 g, and put into a 50 ml centrifuge tube. , And fermented in a thermostat at 37 ° C. The initial pH is 10 and the pH is adjusted every 12 hours.
Was returned to 10. After 72 hours of fermentation, the centrifuge tube was centrifuged to precipitate solids, then the liquid phase was recovered, and the lactic acid concentration in the liquid phase was measured.

[0027]

[Table 6]

In Experiments 5 and 6, the same potato shochu sac and the same carbohydrate were used, and the experiment was conducted by changing the content of water with respect to the organic waste and the carbohydrate. In the comparative example in which the water content is about 12 times that of the organic waste and saccharide, it can be seen that lactic acid is formed only at a very low concentration.

(Experimental Example 7) Next, in order to see the effect of the present invention, as a comparative example, a case where lactic acid bacteria (Lactobacillus delbruecki) were allowed to act without causing bacteria that naturally adhered and mixed with organic waste to act. Was tested below. A steam-sterilized suspension solid of potato shochu waste liquid lees was used as a sample. To 8 g of this shochu lees, 2 g each of glucose, lactose, and starch were added, and water was added to each of the three types of solid samples, each of which was 10 g, to a total of 30 g. 0.1% of the used lactic acid bacterium solution was added, and the mixture was fermented in a thermostat at 37 ° C. The initial pH was set to 10, and the pH was returned to 10 every 12 hours. After 72 hours of fermentation, the centrifuge tube was centrifuged to precipitate solids, then the liquid phase was recovered, and the lactic acid concentration in the liquid phase was measured.

[0030]

[Table 7]

The results are shown below. When starch is used as a saccharide, no lactic acid is produced. From this, when organic waste is steam-sterilized and then lactic acid bacteria widely used industrially are added, only saccharides such as glucose and disaccharide lactose are monosaccharides. It does not contribute to lactic acid fermentation because starch, which is a polysaccharide, is not affected by hydrolytic bacteria mixed in organic waste.

(Experimental Example 8) Beer wort cake was used as a sample. To 8 g of this wort cake, glucose, sucrose, and starch were added in an amount of 2 g each, and water was added to each of the three types of solid samples, each of which was 10 g, to a total of 30 g. The fermentation was carried out in a constant temperature bath at 0 ° C. The initial pH was set to 10, and the pH was returned to 10 every 12 hours. After 72 hours of fermentation, the centrifuge tube was centrifuged to precipitate solids, then the liquid phase was recovered, and the lactic acid concentration in the liquid phase was measured. The results are shown below, and it can be seen that lactic acid is produced at a high concentration and with high selectivity.

[0033]

[Table 8]

(Experimental Example 9) Excess sludge originating from a wastewater treatment pond of a milk factory was used as a sample. To 8 g of the excess sludge, glucose, sucrose, and starch were added in 2 g each, and three types of solid samples each having 10 g were added.
Add water so that the total amount is 30g, and add 50m
and fermented in a 37 ° C. thermostat. The initial pH was set to 10, and the pH was returned to 10 every 12 hours.
After 72 hours of fermentation, the centrifuge tube was centrifuged to precipitate solids, then the liquid phase was recovered, and the lactic acid concentration in the liquid phase was measured. The results are shown below, and it can be seen that lactic acid is produced at a high concentration and with high selectivity.

[0035]

[Table 9]

In the experimental examples 1 to 6, 8 and 9, glucose, sucrose and starch were used as carbohydrates, and bacteria that naturally adhered to and mixed with the organic waste were allowed to act. It can be seen that lactic acid is produced in high concentration and high selectivity even when the saccharide is used. Also,
When low-cost raw materials such as brown sugar and cassava starch are used as saccharides, waste liquids containing a large amount of saccharides such as molasses and confectionery industrial waste, wastes, and mixtures thereof are used as saccharides, or The method of the present invention is also applicable to the case where organic waste is used for general saccharification by physical, scientific or biochemical methods, and is included in the method of the present invention.

In the above experimental examples 1 to 6, 8 and 9, fungi naturally adhering to and mixed with organic wastes from food factories and brewing factories and excess sludge originating from wastewater treatment ponds of milk factories. Although experiments were conducted on the case where it was made to act, for example, lactic acid bacteria such as lactic acid bacteria and hydrolytic bacteria, even when organic waste with very few bacteria attached and mixed naturally, for example, sent directly online from a food factory, etc. It is possible to carry out the method of the present invention by adding a bacterium which assists the action of the above, or by adding any one or more of other organic waste, sludge which has been fermented with lactic acid, and excess sludge. Included in the invention method. In the case where the organic waste does not contain or has a small amount of nitrogen, for example, one or two or more of nitrogen-containing organic waste, lactic acid-fermented sludge, and excess sludge are used. The method of the present invention can be applied by adding the nitrogen content to, for example, 1 to 5% of the organic waste, and the case is also included in the method of the present invention. In the experimental examples 1 to 9 described above, the water content is only about twice as much as the organic waste and the carbohydrate, and only 12 times as much as the water content. In the case of 5 times, lactic acid is produced with high concentration and high selectivity and is included in the method of the present invention.

In the above experimental example, the pH was adjusted at an initial stage and every 12 hours with a well-known pH adjuster. A pH sensor, a temperature sensor, and a dissolved oxygen concentration sensor were attached to the container containing the organic waste. The present invention also includes a case where a pH, a temperature, and a dissolved oxygen concentration are measured by installing a pH adjusting device, a heating device, and an oxygen blowing device.

According to the method of the present invention, a high concentration
Lactic acid produced in a highly selective manner is separated and purified into high-purity lactic acid before and after concentration by a known method or several methods.

[0040]

According to the method for producing lactic acid from organic waste according to any one of claims 1 to 6, organic waste comprising garbage, waste from food factories, unused organic resources, or excess sludge. By adding a suitable amount of sugar and water to the product and allowing the microorganism to act, it has become possible to produce highly useful lactic acid at a high concentration and with high selectivity. From the lactic acid thus obtained, a biodegradable plastic can be produced chemically or by a fermentation method, lactic acid itself can be used as a food additive, and after a chemical treatment, It can also be used as a raw material for various chemical products. Furthermore, while containing various effective resources, it also played a major role in the treatment of organic waste that had been treated mainly by incineration, landfill, and ocean dumping. In particular, in the method for producing lactic acid from organic waste according to claim 2, microorganisms are added to organic waste by adding a suitable amount of saccharide and water, and further controlling the temperature, pH, and dissolved oxygen concentration. Since it is allowed to act, the conditions are suitable for the activity of lactic acid bacteria, and lactic acid can be produced with high concentration and high selectivity. In the method for producing lactic acid from organic waste according to the third aspect, since the microorganisms include lactic acid bacteria or bacteria that assist the activity of lactic acid bacteria and lactic acid bacteria, lactic acid can be produced with high concentration and high selectivity. The method for producing lactic acid from organic waste according to claim 4 comprises one or more of garbage, waste from food factories, unused organic resources, or excess sludge, and contains nitrogen. To the organic waste A, saccharide B such as glucose, sucrose, starch and water C are added at the following ratio, and the temperature is kept from normal temperature to 55 ° C. Since the microorganisms that naturally adhere to the organic waste are allowed to act while appropriately maintaining the anaerobic state below, conditions suitable for the activity of lactic acid bacteria are obtained, and lactic acid is produced at a high concentration and selectively. Can be done. The method for producing lactic acid from organic waste according to claim 5, wherein lactic acid bacteria and / or bacteria that assist the activity of the lactic acid bacteria are added to the microorganisms, so that organic wastes with few naturally attached and mixed bacteria are added. However, lactic acid can be produced at a high concentration and with high selectivity. 7. The method for producing lactic acid from organic waste according to claim 6, wherein in addition to the microorganism, sludge and / or surplus sludge fermented with lactic acid is added, and the organic matter with a small amount of bacteria attached and mixed naturally. Lactic acid can be produced at a high concentration and with high selectivity even for toxic waste.

Claims (6)

[Claims] An organic waste containing one or two or more of raw garbage, waste from a food factory, unused organic resources, or excess sludge, and containing nitrogen content, containing a suitable amount of sugar and water. A method for producing lactic acid from organic waste, characterized in that lactic acid is produced in a high concentration and with high selectivity by adding microorganisms to the microorganisms. 2. An organic waste containing one or two or more of raw garbage, waste from a food factory, unused organic resources, or excess sludge, and containing nitrogen, and a suitable amount of sugar and water. A method of producing lactic acid from organic waste, characterized in that lactic acid is produced at a high concentration and with high selectivity by allowing microorganisms to act under a controlled temperature, pH and dissolved oxygen concentration. . 3. The method for producing lactic acid from organic waste according to claim 1, wherein the microorganism includes a lactic acid bacterium or a bacterium that assists the activity of the lactic acid bacterium and the lactic acid bacterium. 4. An organic waste A containing one or two or more of raw garbage, waste from a food factory, unused organic resources, or excess sludge, and containing nitrogen, glucose, shoe, etc. Sugar B such as sucrose, starch and the like and water C are added in the following weight ratios, and the temperature is kept from normal temperature to 55 ° C., and the pH is more than 3 and is 12 or less, and the anaerobic state is appropriately maintained. A method for producing lactic acid from organic waste, characterized in that lactic acid is produced at a high concentration and with high selectivity by causing microorganisms that naturally adhere to the organic waste to act. A = (1-10) × B C = (0.3-5) × (A + B) 5. The method for producing lactic acid from organic waste according to claim 4, wherein lactic acid bacteria and / or bacteria that help the activity of the lactic acid bacteria are added to the microorganism. 6. The method for producing lactic acid from organic waste according to claim 1, wherein sludge and / or excess sludge fermented with lactic acid is added to the microorganisms.