Compound microbial agent for efficiently producing acid from kitchen waste and application of compound microbial agent

Abstract

The invention discloses a compound microbial agent for efficiently producing acid from kitchen waste and application of the compound microbial agent, and belongs to the technical field of waste treatment. The compound microbial agent disclosed by the invention comprises bacillus amyloliquefaciens, bacillus tequilensis and bacillus licheniformis. According to the method, a bacillus group is selected to prepare a kitchen waste fermentation microbial inoculum, and a multi-stage fermentation culture method of a mixed flora is adopted, so that the thallus quantity and activity of the bacillus are improved, the decomposition rate of large organic matters in the kitchen waste is increased, synthesis of downstream organic acids is promoted, and the yield of the organic acids is increased; a novel microbial resource is developed for efficient acid production of the kitchen waste, and a more efficient method is provided for kitchen waste treatment and sewage treatment.

Description

Technical Field

[0001] The invention relates to the technical field of waste treatment, and in particular to a composite microbial agent for efficiently producing acid from kitchen waste and an application thereof. Background Art

[0002] Organic acids produced by microbial decomposition of macromolecules include formic acid, acetic acid, propionic acid and lactic acid, which are often used as biochemical carbon sources in sewage treatment. They are high-quality carbon sources due to their low cost, high utilization rate and environmental friendliness. The microbial acid production process is a process of hydrolysis followed by acidification, so the upstream hydrolysis efficiency directly determines the downstream acid production capacity. As the main component of domestic waste, food waste has the characteristics of comprehensive nutrients and high utilization rate, and has become a good source of organic acid carbon sources in recent years.

[0003] Commonly used food waste fermentation bacteria include lactic acid bacteria, yeast, acetic acid bacteria and Bacillus. Among them, lactic acid bacteria are the most widely used. However, the decomposition ability of lactic acid bacteria on macromolecular organic matter is limited. The degradation degree of food waste hydrolyzed by lactic acid bacteria is low. Moreover, the fermentation products of lactic acid bacteria are mostly lactic acid, and the lactic acid content in the food waste fermentation liquid fermented by lactic acid bacteria is high. Studies have shown that the phosphorus removal effect of lactic acid as a carbon source for enhanced biological phosphorus removal (EBPR) of wastewater is extremely low. The high proportion of lactic acid in organic acids has a certain impact on the application of food waste fermentation liquid in sewage treatment. Therefore, the development of other strains for food waste fermentation and acid production can expand the microbial resource library on the one hand, and improve the recycling rate of food waste on the other hand.

[0004] In addition, strain quality is also an important factor affecting the acid production of kitchen waste fermentation. High-quality strains have fast metabolism and more products, which can shorten the fermentation cycle and reduce cost investment. Microbial amplification and culture process technology can increase the number of bacteria and improve the quality of strains. At present, microbial amplification and culture mainly focuses on three to four-stage fermentation. The single strain multi-stage fermentation process technology is relatively mature in China, but there are defects in the process of mixed bacterial fermentation. First, there is a lack of theoretical basis. Second, different culture media need to be adjusted according to the fermentation level and different strains. Third, the cost of raw materials (culture medium) needs to be comprehensive under the premise of ensuring the activity of the strain. Therefore, how to supply fermentation bacteria with high fermentation acid production, stable production performance, large quantity, low cost and not contaminated by other bacteria has become a key problem to be solved in this field. Summary of the invention

[0005] The purpose of the present invention is to provide a composite microbial agent for efficient acid production from kitchen waste and its application, so as to solve the problems existing in the above-mentioned prior art. The present invention selects a bacillus group to prepare a kitchen waste fermentation agent, adopts a multi-stage fermentation culture method of a mixed bacterial group, increases the number and activity of the bacillus, increases the decomposition rate of large organic matter in kitchen waste, promotes the synthesis of downstream organic acids, increases the yield of organic acids, develops new microbial resources for efficient acid production from kitchen waste, and provides a more efficient method for kitchen waste treatment and sewage treatment.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a method for preparing a composite microbial agent for efficiently producing acid from kitchen waste, comprising the following steps:

[0008] (1) Inoculating single colonies of Bacillus amyloliquefaciens CICC 10080, Bacillus amyloliquefaciens CICC 10036, Bacillus tequilensis SHBCC D71587, and Bacillus licheniformis CICC 10291 into beef extract peptone liquid medium to prepare primary seed solution;

[0009] (2) mixing the first-level seed solutions of Bacillus amyloliquefaciens CICC 10080, Bacillus amyloliquefaciens CICC 10036, Bacillus tekila SHBCC D71587 and Bacillus licheniformis CICC 10291, and inoculating the mixture into a beef extract peptone liquid medium for cultivation to obtain a second-level seed solution;

[0010] (3) inoculating the secondary seed liquid into a fermentation medium for fermentation and culturing to obtain the composite microbial agent;

[0011] The fermentation medium uses water as a solvent and contains, by mass concentration, 2%-4% brown sugar, 1.2%-2.0% soybean meal hydrolyzate, 0.4%-0.6% dipotassium hydrogen phosphate, and 1.2%-1.8% sodium chloride.

[0012] Optionally, in step (2), the volume ratio of the primary seed solutions of Bacillus amyloliquefaciens CICC 10080, Bacillus amyloliquefaciens CICC 10036, Bacillus tequila SHBCC D71587 and Bacillus licheniformis CICC 10291 when mixed is (3-5):(1-3):(1-3):1.

[0013] Optionally, the culture temperature in step (1) and step (2) is 30° C., and the culture time is 40-50 h.

[0014] Optionally, the fermentation culture temperature in step (3) is 35±2°C and the fermentation time is 40-50h.

[0015] Optionally, the inoculation amounts in step (2) and step (3) are both 4%-8%.

[0016] The present invention also provides a composite microbial agent prepared by the above preparation method.

[0017] The present invention also provides application of the composite microbial agent in acid production by fermentation of kitchen waste.

[0018] The present invention also provides a fermentation method for efficiently producing acid from kitchen waste, comprising the steps of inoculating the composite microbial agent into kitchen waste slurry, and fermenting and culturing to produce organic acid.

[0019] Optionally, the inoculation amount is not less than 0.6% of the mass of the food waste slurry.

[0020] Optionally, the fermentation culture temperature is 50±2°C.

[0021] The present invention discloses the following technical effects:

[0022] The present invention uses a bacillus group to prepare a food waste fermentation agent. Compared with lactic acid bacteria, the bacillus of the present invention can quickly decompose organic matter, especially when treating food waste containing a large amount of organic matter, its decomposition speed and efficiency are much higher than those of lactic acid bacteria. The product is mostly volatile fatty acids, with a low lactic acid content, and the fermentation product has great application prospects. In addition, the bacillus of the present invention has strong adaptability, a certain degree of heat resistance, and a wider range of applications.

[0023] The present invention adopts a multi-stage fermentation culture method of a mixed bacillus flora, which solves the problem of decreased vitality due to incompatibility between floras that may occur when a single strain is fermented and then mixed, and reduces the preparation and acclimatization time of the composite bacterial agent. The multi-stage fermentation culture method of the present invention can increase the number and vitality of bacillus, improve the decomposition rate of large organic matter in food waste, significantly promote the synthesis of downstream organic acids, increase the yield of organic acids, develop new microbial resources for efficient acid production from food waste, and provide a more efficient method for food waste treatment and sewage treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 The acid production when the bacterial agents prepared with different culture media in Example 2 fermented the food waste;

[0026] Figure 2 This is the appearance diagram of the 20L microorganism culture fermentation tank in Example 3;

[0027] Figure 3 The microscopic examination results of the bacterial preparation after 48 hours of tertiary fermentation in Example 3;

[0028] Figure 4 The results of microbial examination after 72 hours of tertiary fermentation in Example 3;

[0029] Figure 5 The results of the test on the nutrient hydrolysis effect of the composite microbial agent in Example 3 are as follows;

[0030] Figure 6 This is the appearance diagram of the 8L food waste fermentation tank in Example 3. DETAILED DESCRIPTION

[0031] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0032] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0033] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0034] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0035] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0036] The sources of the biological materials involved in the present invention are as follows:

[0037] Bacillus amyloliquefaciens: CICC 10080; purchased from China Industrial Microbiological Culture Collection Management Center;

[0038] Bacillus amyloliquefaciens: CICC 10036; purchased from China Industrial Microbiological Culture Collection Center;

[0039] Bacillus tequila: SHBCC D71587; purchased from Shanghai Collection Biotechnology Center;

[0040] Bacillus licheniformis: CICC 10291; purchased from China Industrial Microbiological Culture Collection Center.

[0041] Unless otherwise specified, other reagents or materials involved in the embodiments of the present invention can be purchased through conventional channels; the operating methods or detection methods involved, unless otherwise specified, are carried out according to conventional methods in the art.

[0042] Example 1 Strain antagonism experiment

[0043] Bacillus amyloliquefaciens CICC 10080, Bacillus amyloliquefaciens CICC 10036, Bacillus tekila SHBCC D71587 and Bacillus licheniformis CICC 10291 were streaked on LB plates to observe whether there was antagonism between the strains. The results showed that there was no antagonism between the selected four strains, and they could grow together, which showed the potential for preparing composite microbial agents.

[0044] Example 2 Optimization of fermentation medium

[0045] After activating the four strains, single strain seed solutions were prepared respectively: a single colony was picked up using an inoculation loop and inoculated into 300 mL of liquid beef extract peptone medium, and cultured at 30° C. and 200 rpm for 48 h to prepare a primary seed solution.

[0046] The first-level seed solutions of Bacillus amyloliquefaciens CICC 10080, Bacillus amyloliquefaciens CICC 10036, Bacillus tekila SHBCC D71587 and Bacillus licheniformis CICC 10291 were mixed in a volume ratio of 4:2:2:1 to obtain a mixed seed solution. The mixed seed solution was inoculated into 1# and 2# culture media at a ratio of 5% (v / v), and cultured at 30°C and 200rpm for 48 hours to obtain a bacterial agent, and the number of viable bacteria of the two bacterial agents was detected. The results showed that the number of viable bacteria in the bacterial agent after 48 hours of culture in 1# culture media was 0.8×10 9 CFU / mL, the viable bacterial count of the inoculum after 48 hours of culture in 2# medium was 2.0×10 9 CFU / mL.

[0047] Among them, 1# culture medium: water as solvent, containing 3% brown sugar, 1.5% soybean cake powder hydrolyzate, all are mass concentrations; 2# culture medium: water as solvent, containing 3% brown sugar, 1.5% soybean cake powder hydrolyzate, 0.5% dipotassium hydrogen phosphate, 1.5% sodium chloride, all are mass concentrations.

[0048] The preparation process of soybean meal hydrolyzate is as follows:

[0049] a. Mix soybean cake powder and water in a mass ratio of 2:8 and stir evenly to form an emulsion;

[0050] b. Use 6 mol / L HCl to adjust the pH of the emulsion to 4.0, place it in a water bath at 100°C, stir intermittently for 1 hour, filter through gauze to remove impurities and retain the supernatant, which is the soybean cake powder hydrolyzate.

[0051] After the kitchen waste (collected from the harmless treatment center of kitchen waste in Jingzhou City, Hubei Province) was screened out of large substances and crushed to obtain a slurry, and the pH was adjusted to 7.0 with 30% sodium hydroxide solution for use. The treated slurry was divided into conical flasks, and 400 mL was added to each conical flask, and then inoculated with the bacterial agents prepared by the above-mentioned different culture media. The bacterial agent prepared by 1# culture medium was marked as A1, and the bacterial agent prepared by 2# culture medium was marked as A2. The inoculation amount was 0.6% (w / w), and an equal amount of water was used as a blank control, and the blank control was marked as CK. After inoculation, the shaker was placed for acid production fermentation. At 35°C and 200rpm, the VFA content was detected after 48 hours of fermentation. The detection method was distillation titration. The specific process is as follows:

[0052] 1) Take 150 mL of the fermented hydrolyzate and centrifuge at 4000 r for 10 min to obtain the supernatant;

[0053] 2) Transfer 100 mL of the supernatant to a distillation flask, add 3 mL of phosphoric acid, and distill at 105 °C;

[0054] 3) Use a conical flask pre-filled with 25 mL of deionized water to collect the condensate during the distillation process;

[0055] 4) After collecting 100 mL of condensate, continue to add 50 mL of deionized water to the distillation flask and continue distillation by heating;

[0056] 5) After collecting 150 mL of condensate, heat the conical flask, and quickly remove the liquid from the conical flask after it boils. At the same time, add 10 drops of phenolphthalein indicator and immediately titrate with 0.5 mol sodium hydroxide solution, while recording the sodium hydroxide consumption;

[0057] 6) VFA content is calculated according to the following formula:

[0058]

[0059] Where:

[0060] ρ---Organic acid content, unit: mg / L;

[0061] c------The value of the concentration of sodium hydroxide standard solution, in moles per liter (mol / L);

[0062] V2----The volume of sodium hydroxide standard solution consumed when titrating the sample, in milliliters (mL);

[0063] m-----The numerical value of the molar mass of acetic acid, in grams per mole (g / mol) (M = 60.05);

[0064] V1-----The volume of the sample taken, in milliliters (mL);

[0065] 0.7-----Correction coefficient; since this method is an empirical method, it is assumed that only 70% volatile acid will be obtained in the distillate, and this value is used for correction in the calculation.

[0066] The results are as follows Figure 1 As shown, compared with the blank control, the organic acid production of food waste fermented by the inoculant prepared with 1# culture medium increased by 7.5%; the organic acid production of food waste fermented by the inoculant prepared with 2# culture medium increased by 43.4%.

[0067] Based on the test results of live bacteria count and acid production from food waste fermentation, 2# culture medium was selected for the preparation of composite microbial agent.

[0068] Example 3 Preparation and Functional Verification of Composite Microbial Agent

[0069] 1. Preparation of composite microbial agents:

[0070] After activating the four strains, single strain seed solutions were prepared respectively: a single colony was picked up using an inoculation loop and inoculated into 300 mL of liquid beef extract peptone medium, and cultured at 30° C. and 200 rpm for 48 h to prepare a primary seed solution.

[0071] The primary seed solutions of Bacillus amyloliquefaciens CICC 10080, Bacillus amyloliquefaciens CICC 10036, Bacillus tekila SHBCC D71587 and Bacillus licheniformis CICC 10291 were mixed at a volume ratio of 4:2:2:1 to obtain a mixed seed solution. The mixed seed solution was inoculated into 300 mL of liquid beef extract peptone medium at a ratio of 5% (v / v), and cultured at 30°C and 200 rpm for 48 hours to prepare a secondary seed solution.

[0072] The secondary seed liquid was inoculated into a 20L fermenter at a ratio of 5% (v / v) for tertiary fermentation ( Figure 2 ), the fermentation medium used was the 2# medium in Example 2. Before the fermentation tank was connected to the material, the tank body was chemically sterilized: 200 mL of 0.2% sodium hypochlorite solution was evenly sprayed inside the tank body using an atomizing device; the fermentation medium was sterilized using high-pressure steam: sodium hypochlorite was volatilized for more than 12 hours at room temperature and inoculated normally. The fermentation parameters of the fermentation tank are shown in Table 1. Samples were taken for microscopic examination and the number of viable bacteria was detected at the end of 48 hours and 72 hours of fermentation. The microscopic examination results are shown in Table 1. Figure 3-Figure 4 The results of the viable bacterial count test are shown in Table 2. The results showed that after 48 hours of tertiary fermentation, the bacterial density was high and the morphology was uniform. At the same time, the bacterial cells were short rod-shaped and no autolysis was observed ( Figure 3 ); the number of viable bacteria during this period was calculated by plate counting to be 1.14×10 9 CFU / mL; 72h later, the cells showed irregular shapes, mostly oval, with few short rods, indicating that bacterial spores began to fall off during this period; at the same time, the bacterial density was significantly lower than that of the 48h period ( Figure 4 ), the number of viable bacteria during this period was 0.71×10 9 CFU / mL. Therefore, the fermentation liquid after 48h of fermentation was selected as the composite microbial agent for food waste fermentation.

[0073] Table 1 Fermentation parameters of fermenter

[0074] temperature 35±2℃ Speed 120rpm Aeration volume 4L / min Inoculation volume 5%(v / v) Cultivation time 48h

[0075] Table 2 Number of viable bacteria at different fermentation times

[0076] Fermentation time (h) <![CDATA[Viable cell count (×10 9 CFU / mL)]]> 48 1.14 72 0.91

[0077] 2. Functional verification of composite microbial agents

[0078] 2.1 Test the nutrient hydrolysis effect of the composite microbial agent:

[0079] (1) Test method for protein-degrading bacteria:

[0080] The bacteria were spotted onto a protein culture medium plate and cultured in a 37°C incubator for two days. The hydrolysis zone diameter (D) and colony diameter (d) were measured with a vernier caliper, and the ratio of the two (D / d) was calculated. The strength of the strain's protease production ability was determined based on the size of the ratio.

[0081] Protein culture medium (g / L): skimmed milk powder 50.0, soluble starch 10.0, yeast extract 5.0, KH 2 PO 4 1. MgSO 4 7H 2 O 0.2, agar 20.0, pH 7.0. Sterilize at high temperature and high pressure at 115℃ for 20min before use.

[0082] (2) Testing method for starch-degrading bacteria:

[0083] The bacteria were spotted onto a starch culture medium plate and cultured in an incubator at 37°C for two days. Then, an iodine indicator was added and the hydrolysis zone diameter (D) and colony diameter (d) were measured with a vernier caliper. The ratio of the two (D / d) was calculated. The ability of the strain to produce amylase was determined based on the ratio.

[0084] Starch medium (g / L): soluble starch 5.0, peptone 5.0, beef extract 5.0, NaCl 5.0, agar 20.0, pH 7.0. Sterilize at high temperature and high pressure at 115℃ for 20 minutes before use.

[0085] (3) Test methods for cellulose-degrading bacteria:

[0086] The bacteria were spotted onto a cellulose culture medium plate and cultured in an incubator at 37°C for two days. The hydrolysis zone diameter (D) and colony diameter (d) were measured with a vernier caliper, and the ratio of the two (D / d) was calculated. The strength of the strain's ability to produce cellulase was determined based on the size of the ratio.

[0087] Use 1mg / mL Congo red dye solution to dye it for 30 minutes, then discard the used Congo red dye solution, and then absorb 1mol / L NaCl solution for decolorization for 30 minutes. After a while, an obvious transparent circle will appear, and the diameter of the transparent circle (D) and the diameter of the colony (d) will be measured.

[0088] Cellulose (sodium carboxymethyl cellulose) medium (g / L): CMC-Na 20.0, Na 2 HPO 4 2.5, KH2 PO 4 1.5, peptone 2.5, agar 20, pH 7.0. Sterilize at high temperature and high pressure at 115℃ for 20 minutes before use.

[0089] (4) Test method for fat-degrading bacteria:

[0090] The bacteria were spotted onto a Tween-80 medium plate and cultured in an incubator at 37°C for 2 days. After the sealing film was removed, the plate was placed at 4°C for 2 days, and the surface oil was dried before staining. The hydrolysis zone diameter (D) and colony diameter (d) were measured with a vernier caliper, and the ratio of the two was calculated (D / d). The ability of the strain to produce lipase was determined based on the size of the ratio.

[0091] Tween-80 medium (g / L): peptone 10g, yeast extract 5g, NaCl 5g, CaCl 2 ·2H 2 O 0.1g, Tween-80 10mL, distilled water 1000mL, agar 20g, pH 7.0, sterilize at 121℃ for 20min before use.

[0092] Test results such as Figure 5 The results showed that protein D / d = 3.38, starch D / d = 2.13, fat D / d = 1.61, and cellulose D / d = 1.7, indicating that the composite microbial agent has a good hydrolysis effect on nutrients.

[0093] 2.2 Test the acid production function of the composite microbial agent in the fermentation of food waste:

[0094] The kitchen waste (collected from the kitchen waste harmless treatment center in Jingzhou City, Hubei Province) was screened and crushed to obtain a slurry, which was adjusted to pH 7.0 using 30% sodium hydroxide solution and placed in an 8L fermentation tank ( Figure 6 ). The mixed bacterial agent was inoculated into the food waste slurry at a ratio of 0.6% (w / w). After the food waste slurry was mixed with the bacterial agent, the tank stirring device was started. The VFA content, COD and ammonia nitrogen content were measured every 1d at 50°C. The results are shown in Table 3. The results showed that the organic acid content gradually increased from the initial 4.49g / L after inoculation, and the output after 13d could reach 33g / L (Table 1). At the same time, COD (soluble) and ammonia nitrogen increased accordingly, indicating that after inoculation of the bacterial agent, the large organic matter was decomposed by microorganisms to generate ammonia nitrogen on the one hand, and the large organic matter hydrolyzed small molecular substances on the other hand, causing an increase in soluble COD, thereby promoting the acid production capacity downstream.

[0095] Table 3 Functional verification results of compound microbial agent fermentation of food waste

[0096]

[0097]

[0098] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a composite microbial agent for efficient acid production from kitchen waste, characterized in that: The steps include: (1) Inoculating single colonies of Bacillus amyloliquefaciens CICC 10080, Bacillus amyloliquefaciens CICC 10036, Bacillus tequilensis SHBCC D71587, and Bacillus licheniformis CICC 10291 into beef extract peptone liquid medium to prepare primary seed solution; (2) mixing the first-level seed solutions of Bacillus amyloliquefaciens CICC 10080, Bacillus amyloliquefaciens CICC 10036, Bacillus tekila SHBCC D71587 and Bacillus licheniformis CICC 10291, and inoculating the mixture into a beef extract peptone liquid medium for cultivation to obtain a second-level seed solution; (3) inoculating the secondary seed liquid into a fermentation medium for fermentation and culturing to obtain the composite microbial agent; The fermentation medium uses water as a solvent and contains, by mass concentration, 2%-4% brown sugar, 1.2%-2.0% soybean meal hydrolyzate, 0.4%-0.6% dipotassium hydrogen phosphate, and 1.2%-1.8% sodium chloride.

2. The preparation method according to claim 1, characterized in that: In step (2), the volume ratio of the first-level seed solutions of Bacillus amyloliquefaciens CICC10080, Bacillus amyloliquefaciens CICC 10036, Bacillus tequila SHBCC D71587 and Bacillus licheniformis CICC10291 when mixed is (3-5):(1-3):(1-3):

1.

3. The preparation method according to claim 1, characterized in that: The culture temperature in step (1) and step (2) is 30° C., and the culture time is 40-50 h.

4. The preparation method according to claim 1, characterized in that: The fermentation temperature in step (3) is 35±2°C and the fermentation time is 40-50h.

5. The preparation method according to claim 1, characterized in that: The inoculation amounts in step (2) and step (3) are both 4%-8%.

6. A composite microbial agent prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the composite microbial agent according to claim 6 in acid production by fermentation of food waste.

8. A method for efficiently producing acid from kitchen waste, characterized in that: The method comprises the steps of inoculating the composite microbial agent according to claim 6 into the slurry of food waste, and fermenting and culturing the slurry to produce organic acid.

9. The fermentation method according to claim 8, characterized in that The inoculated amount is not less than 0.6% of the mass of the kitchen waste slurry.

10. The fermentation method according to claim 8, characterized in that The temperature of the fermentation culture is 50±2°C.

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