Acid-resistant and high-temperature-resistant cellulose degradation complex microbial inoculant for vinasse decomposition as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of microorganisms, and particularly relates to an acid-resistant and high-temperature-resistant cellulose degradation complex microbial inoculant for vinasse decomposition and a preparation method and application thereof. The composite microbial inoculant disclosed by the invention comprises aspergillus fumigatus, rhizomucor minuta and Rasamsoniacomposticola, and the mass ratio of the solid microbial inoculant of the aspergillus fumigatus to the solid microbial inoculant of the rhizomucor minuta to the solid microbial inoculant of the Rasamsoniacomposticola is (1 to 5) to (1 to 3) to (1 to 3). The complex microbial inoculant is used for vinasse composting, has the advantages of acid resistance, high temperature resistance, high composting efficiency and high cellulose degradation rate, and has a good application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of microbiology, and particularly relates to an acid-resistant and high-temperature-resistant cellulose-degrading composite microbial agent for vinasse composting, a preparation method thereof, and uses thereof. Background Art

[0002] Vinasse is a by-product of liquor production. The annual output of vinasse in China reaches tens of millions of tons. Vinasse has high moisture content, high acidity, large quantity and concentration, and is rich in nutrients such as cellulose, fermentation products, and unused starch, protein, and trace elements. If not processed in time, it is extremely easy to rot and deteriorate. Therefore, the resource-based, harmless, and reduction treatment of vinasse is very necessary.

[0003] Producing organic fertilizer from vinasse is an effective way to utilize vinasse resourcefully. The organic substances such as protein, amino acid, fat, cellulose, and hemicellulose contained in vinasse have the effect of improving soil structure and soil microbial community, and nitrogen, phosphorus, potassium, and trace elements can improve the disease resistance of crops, making it an excellent organic fertilizer source.

[0004] Most of the organic substances contained in vinasse are unstable. Direct application without composting will cause a series of problems such as odor, heat generation, leachate, and the occurrence of pests and diseases. Through aerobic composting, these problems can be solved. Aerobic composting technology is often used for the treatment of solid waste. Under certain external conditions, microorganisms are used to degrade organic matter and convert it into stable humus. The natural composting of solid waste takes a long time and the degradation is not thorough. Microbial agents (composting agents) are often added to accelerate the degradation of the substrate, shorten the fermentation cycle, and improve the quality of compost products. Vinasse has a high acidity, with a pH value between 3.4 and 4.0. It is difficult for microorganisms to colonize in vinasse and carry out rapid composting fermentation, and there are a large number of metabolic inhibitors of microorganisms, making the degradation more difficult. Therefore, adding a composting agent suitable for vinasse composting to effectively and rapidly degrade vinasse and promote the composting of aerobic compost is a key step in producing organic fertilizer from vinasse.

[0005] Although certain results have been achieved in the research on producing vinasse biological organic fertilizer by adding composting agents. For example, "CN202010307768.9 A production process for fermenting organic fertilizer using Maotai-flavor liquor vinasse" discloses the role of Aspergillus fumigatus in vinasse composting; "CN202080026937.X A method for producing fermentation products" discloses the role of Rhizomucor pusillus in vinasse composting. However, due to the different adaptation environments and metabolic pathways of different microorganisms, the organic substances suitable for their fermentation and decomposition are also different. Therefore, for the aerobic composting of vinasse, in order to achieve the best effect, how to select the best microbial composition and its ratio is an urgent problem to be solved in this field. Summary of the Invention

[0006] In view of the problems of the prior art, the present invention provides an acid-resistant and high-temperature-resistant cellulose-degrading composite microbial inoculum for distiller's grains composting, its preparation method and uses.

[0007] A microorganism which is a strain with a preservation number of CGMCC NO.40857, CGMCC NO.40858 or CGMCC NO.40859 preserved in the General Microbiology Center of the China Committee for Culture Collection of Microorganisms.

[0008] The present invention also provides a composite microbial inoculum, comprising: Aspergillus fumigatus, Rhizomucor pusillus and Rasamsonia composticola, wherein the mass ratio of the solid microbial inoculums of Aspergillus fumigatus, Rhizomucor pusillus and Rasamsonia composticola is (1 - 5):(1 - 3):(1 - 3).

[0009] Preferably, the mass ratio of the solid microbial inoculums of Aspergillus fumigatus, Rhizomucor pusillus and Rasamsonia composticola is 1:1:1.

[0010] Preferably, the homology of the ITS rDNA sequence of Aspergillus fumigatus and the ITS rDNA sequence of Aspergillus fumigatus with GenBank accession number OP482428.1 is greater than 99%;

[0011] and / or, the homology of the ITS rDNA sequence of Rhizomucor pusillus and the ITS rDNA sequence of Rhizomucor pusillus with GenBank accession number KJ527032.1 is greater than 99%;

[0012] and / or, the homology of the ITS rDNA sequence of Rasamsonia composticola and the ITS rDNA sequence of Rasamsonia composticola with GenBank accession number JF417481.1 is greater than 99%.

[0013] Preferably, the Aspergillus fumigatus is a strain with a preservation number of CGMCC NO.40857 preserved in the General Microbiology Center of the China Committee for Culture Collection of Microorganisms;

[0014] and / or, the Rhizomucor pusillus is a strain with a preservation number of CGMCC NO.40858 preserved in the General Microbiology Center of the China Committee for Culture Collection of Microorganisms;

[0015] and / or, the Rasamsonia composticola is a strain with a preservation number of CGMCC NO.40859 preserved in the General Microbiology Center of the China Committee for Culture Collection of Microorganisms.

[0016] Preferably, the solid bacterial agent is a solid obtained by culturing Aspergillus fumigatus, Rhizomucor pusillus, and Rasamsonia composticola in a solid medium and then drying.

[0017] The present invention also provides a method for preparing the above composite bacterial agent, which includes the following steps:

[0018] Step 1: Culture Aspergillus fumigatus, Rhizomucor pusillus, and Rasamsonia composticola separately to obtain the cultures of the three strains of bacteria.

[0019] Step 2: Dry and crush the cultures, and then mix them in proportion to obtain the composite bacterial agent.

[0020] Preferably, during the culturing process in Step 1, the inoculation temperature is 30°C - 50°C; the culturing temperature after inoculation is 35 - 45°C.

[0021] And / or, in Step 1, the culture medium used for culturing is composed of water and bran at a weight ratio of 0.6 - 0.9:1.

[0022] And / or, in Step 1, the culturing time is 2.5 days - 4 days.

[0023] And / or, in Step 2, after drying the cultures, the water content is controlled at 10% - 12%.

[0024] The present invention also provides the use of the above composite bacterial agent in distiller's grains composting.

[0025] The present invention also provides a method for distiller's grains composting, which is to mix distiller's grains, water, and the above composite bacterial agent and then carry out composting.

[0026] Preferably, during the composting process, the water content is controlled at 50% - 60%.

[0027] And / or, the addition amount of the composite bacterial agent is 0.1% - 0.5% of the weight of the distiller's grains.

[0028] And / or, the composting time is 25 - 35 days.

[0029] The present invention provides a composite microbial agent for distiller's grains composting. In the composite microbial agent of the present invention, the strains are all isolated from distiller's grains, grow well at pH 3.0 - pH 7.0, can adapt to the special environment of distiller's grains, are easy to colonize in distiller's grains and rapidly compost and ferment. The strains in the composite microbial agent all have cellulase activity and can degrade cellulose, and the strains can all grow well at 30°C - 50°C. Among them, the optimal growth temperature of Aspergillus fumigatus is 30°C - 40°C, the optimal growth temperature of Rhizomucor pusillus is 35°C - 45°C, and the optimal growth temperature of Rasamsonia composticola is 40°C - 50°C. Different strains act together at different stages of distiller's grains decomposition to improve the substrate utilization rate, extend the duration of high temperature, and shorten the distiller's grains decomposition cycle. Therefore, the composite microbial agent of the present invention has good application prospects in the composting of distiller's grains.

[0030] Obviously, based on the above content of the present invention, according to the common general knowledge and customary means in the art, without departing from the above basic technical idea of the present invention, various other forms of modification, substitution or change can also be made.

[0031] The following is a further detailed description of the above content of the present invention through specific embodiments in the form of examples. However, this should not be understood as limiting the scope of the above subject matter of the present invention to the following examples. All technologies implemented based on the above content of the present invention belong to the scope of the present invention. Description of the Drawings

[0032] Figure 1 It is a graph showing the temperature change trend during the composting process in Example 3;

[0033] Figure 2 It is a graph showing the pH change trend during the composting process in Example 3;

[0034] Figure 3 It is a graph showing the conductivity change trend during the composting process in Example 3. Detailed Description of the Invention

[0035] In the following examples and experimental examples, the reagents and raw materials used are all commercially available products.

[0036] The culture media used in the following examples are:

[0037] 1. Primary screening culture medium:

[0038] The components and the weight percentages of each component are respectively: sodium carboxymethylcellulose 1%, dipotassium hydrogen phosphate 0.1%, magnesium sulfate heptahydrate 0.01%, ferrous sulfate heptahydrate 0.01%, manganese sulfate 0.003%, congo red 0.002%, agar 2.0%, and the remaining component is water.

[0039] The pH of the culture medium is 5.0.

[0040] 2. Rescreening medium:

[0041] (1) Beef extract peptone medium: The components and their respective weight percentages are as follows: beef extract 0.3%, peptone 1.0%, sodium chloride 0.5%, and the remaining component is water.

[0042] Adjust the pH of the medium to 3.0, 4.0, 5.0, 6.0, and 7.0 respectively.

[0043] (2) Potato juice liquid medium: 200 grams of potatoes, add 1000 milliliters of water, boil for 20 minutes, filter with four layers of gauze, make the filtrate up to 1000 milliliters in volume, and add 20 grams of glucose.

[0044] Adjust the pH of the medium to 3.0, 4.0, 5.0, 6.0, and 7.0 respectively.

[0045] 3. PDA medium:

[0046] 200 grams of potatoes, add 1000 milliliters of water, boil for 20 minutes, filter with four layers of gauze, make the filtrate up to 1000 milliliters in volume, add 20 grams of glucose, and 15 grams of agar.

[0047] The pH of the PDA medium is 6.0.

[0048] 4. Solid fermentation medium:

[0049] Water and bran are uniformly mixed in a weight ratio of 0.7:1.

[0050] Example 1 Isolation and Identification of Acid-Resistant and Heat-Tolerant Cellulose-Degrading Bacteria

[0051] I. Isolation

[0052] (1) Primary screening

[0053] Samples were taken from the temperature-rising period, high-temperature period, temperature-dropping period, and composting period of the naturally piled strong-flavor liquor distiller's grains (purchased from Chengdu Fuhua Huannong Feed Co., Ltd.). After pulverization, 25 g was added to 225 mL of sterile physiological saline, and shaken at room temperature for 30 min (180 r / min) to prepare a 10 -1 bacterial suspension; after standing for 30 min, 1 mL of the supernatant was taken and added to 9 mL of sterile physiological saline and mixed evenly to prepare a 10 -2 bacterial suspension; and so on, to prepare 10 -3 、10 -4 、10 -5 、10 -6 bacterial suspensions; 10 -4 、10 -5 、10 -61 mL of the bacterial suspension at each dilution was placed in a sterile Petri dish, and carboxymethyl cellulose sodium-Congo red medium melted and cooled to 45 °C was added and mixed evenly. After solidification, it was placed in a constant temperature incubator at 45 °C for 7 days. If there was a colorless transparent circle around the grown colonies, the strain could degrade cellulose. The strains producing colorless transparent circles were selected for streak isolation until pure strains were obtained.

[0054] (2) Re-screening

[0055] The bacteria obtained from the primary screening were respectively inoculated into nutrient broth peptone media with different pH values and cultured in a constant temperature shaking incubator at 30 °C, 35 °C, 40 °C, 45 °C, and 50 °C for 5 days; the fungi obtained from the primary screening were respectively inoculated into potato juice liquid media with different pH values and cultured in a constant temperature shaking incubator at 30 °C, 35 °C, 40 °C, 45 °C, and 50 °C for 7 days; the strains that grew well at pH 3.0 - pH 7.0 and 30 °C - 50 °C were acid- and heat-tolerant cellulose-degrading bacteria. The antagonistic effects between the strains were detected by the mixed culture plate method. Strains without a transparent circle between them indicated no antagonistic effect and could be used for the formulation of compound microbial agents. Three strains were obtained and numbered ZY-16, ZY-25, and ZY-43 respectively.

[0056] II. Identification

[0057] (1) Identification of strain ZY-16

[0058] After being cultured on a PDA medium plate at 30 °C for 4 days, the diameter of strain ZY-16 reached 2.6 cm. The mycelium was initially white and then turned smoky gray, and the reverse side was colorless. No exudate was produced, and no soluble pigment was produced. The mycelium was non-septate, branched, with a vesicle axis, no vesicle stalk, and the sporangiospores were spherical. It was heat-resistant and grew well at 50 °C.

[0059] The molecular biological characteristics of strain ZY-16 were as follows: When the ITS rDNA sequence was compared with the GenBank database, the homology with the ITS rDNA sequence of Aspergillus fumigatus was greater than 99%.

[0060] Based on the above morphological and genetic characteristics, this acid- and heat-tolerant cellulose-degrading strain could be identified as Aspergillus fumigatus, and it was deposited in the China General Microbiological Culture Collection Center on October 25, 2023. The deposit address was: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences; the deposit number was CGMCC NO. 40857; the taxonomic name was Aspergillus fumigatus.

[0061] (2) Identification of strain ZY-25

[0062] After being cultured on a PDA medium plate at 30 °C for 4 days, the diameter of strain ZY-25 reached 8.6 cm. The mycelium was initially white and then turned dark gray, with the reverse side being colorless. There was no exudate produced and no soluble pigment produced. The mycelium was septum-free, branched, with a columella, no apophysis, and the sporangiospores were spherical. It was heat-resistant and grew well at 50 °C.

[0063] The molecular biological characteristics of strain ZY-25 were as follows: When the ITS rDNA sequence was compared with the GenBank database, the homology with the ITS rDNA sequence of Rhizomucorpusillus was greater than 99%.

[0064] Based on the above morphological and genetic characteristics, this acid- and heat-resistant cellulose-degrading bacterium could be identified as Rhizomucorpusillus. The strain was deposited in the China General Microbiological Culture Collection Center on October 25, 2023. The deposit address was: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences; the deposit number was CGMCC NO. 40858; the taxonomic name was Rhizomucorpusillus.

[0065] (3) Identification of strain ZY-43

[0066] Strain ZY-43 grew rapidly on a PDA medium plate. When cultured at 45 °C for 4 days, the diameter was 6.3 - 6.7 cm. The front side was light bright yellow, and the reverse side was dark gray. There was no exudate produced and no soluble pigment produced. The mycelium was relatively thin, and cleistothecia were produced, which were spherical. The asci were smooth, and the ascospores were spherical, single or in chains. It was heat-resistant and grew well at 50 °C.

[0067] The molecular biological characteristics of strain ZY-43 were as follows: When the ITS rDNA sequence was compared with the GenBank database, the homology with the ITS rDNA sequence of Rasamsonia composticola was greater than 99%.

[0068] Based on the above morphological and genetic characteristics, this acid- and heat-resistant cellulose-degrading bacterium could be identified as Rasamsonia composticola. The strain was deposited in the China General Microbiological Culture Collection Center on October 25, 2023. The deposit address was: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences; the deposit number was CGMCC NO. 40859; the taxonomic name was Rasamsonia composticola.

[0069] Example 2 Composite Bacterial Agent and Its Preparation Method

[0070] This example provides a compound microbial agent prepared from the isolated ZY-16, ZY-25, and ZY-43 in Example 1.

[0071] The preparation method is as follows:

[0072] (1) Weigh 25 g - 30 g of the solid fermentation medium into a 500 mL Erlenmeyer flask and sterilize it at 121 °C for 30 minutes;

[0073] (2) Respectively take the fresh-activated, vigorously growing, and spore-rich Aspergillus fumigatus ZY-16, Rhizomucor pusillus ZY-25, and Rasamsonia composticola ZY-43 strains, add 5 mL of sterile normal saline, shake to disperse the spores to make a spore suspension. After the solid fermentation medium cools to below 50 °C, inoculate the spore suspension and incubate statically at 40 °C for 3 days;

[0074] (3) Dry the above cultures at 45 °C for 12 h - 24 h respectively, control the water content to 10% - 12%, and obtain the solid microbial agents of individual strains after pulverization. Mix the solid microbial agents of the three strains evenly in a mass ratio of 1:1:1, and encapsulate them in a self-sealing bag to obtain the compound microbial agent.

[0075] Weigh the above compound microbial agent product and count it according to GB4789 (mold counting method). The viable count in the compound microbial agent is 1.0×10 7 CFU / g or more, and the number of miscellaneous bacteria is less than 0.2%.

[0076] Composting method for distiller's grains in Example 3

[0077] This example uses the compound microbial agent prepared in Example 2 for composting distiller's grains. Specifically as follows:

[0078] I. Experimental grouping

[0079] In addition to the experimental group provided with the compound microbial agent, this example also provides the composting effects of commercial microbial agents and single-component microbial agents as control experimental groups. Specifically:

[0080] The composting raw materials are 10 kg of distiller's grains dry powder (the distiller's grains dry powder is obtained by pulverizing the Luzhou-flavor distiller's grains purchased from Chengdu Fuhua Huannong Feed Co., Ltd.) and 5 kg of water. The following proportions of adding microbial agents are all calculated based on the weight of the distiller's grains dry powder.

[0081] Z1: Without adding microbial agent;

[0082] Z2: Add a common composting microbial agent (EM microbial agent, Henan Wobao Biotechnology Co., Ltd.), and the addition amount is 0.3% of the weight of the distiller's grains;

[0083] Z3: Add the compound microbial agent in Example 2, and the addition amount is 0.3% of the weight of the distiller's grains;

[0084] Z4: Add the ZY-16 solid bacterial agent (i.e., the solid obtained by drying the single-strain culture obtained in Example 2 according to the method of Example 2), and the addition amount is 0.3% of the weight of the distillers grains;

[0085] Z5: Add the ZY-25 solid bacterial agent (i.e., the solid obtained by drying the single-strain culture obtained in Example 2 according to the method of Example 2), and the addition amount is 0.3% of the weight of the distillers grains;

[0086] Z6: Add the ZY-43 solid bacterial agent (i.e., the solid obtained by drying the single-strain culture obtained in Example 2 according to the method of Example 2), and the addition amount is 0.3% of the weight of the distillers grains.

[0087] II. Composting method

[0088] After mixing the raw materials of the compost and the bacterial agent, pile them into a conical shape. Measure the temperature and water content every day. When the water content is lower than 50%, add water to keep the water content between 50% and 60% throughout the process. The composting experiment lasts for 30 days. Collect 100 g samples from each pile every 5 days. After drying the samples, conduct physical and chemical index analysis.

[0089] III. Experimental results

[0090] A. Temperature change during composting

[0091] During the composting process, temperature is a key indicator to characterize whether the composting starts and proceeds smoothly. The temperature changes of the three treatments are as Figure 1 shown. The rise in compost temperature indicates that the composting starts. The temperatures of all treatments rise after the composting starts. Z3 (adding the composite bacterial agent of the present invention) enters the high-temperature period (above 50°C) on the fourth day, earlier than other treatment experimental groups. Z1 (without adding bacterial agent), Z2 (adding EM bacterial agent), Z4 (adding ZY-16 solid bacterial agent), Z5 (adding ZY-25 solid bacterial agent), Z6 (adding ZY-43 solid bacterial agent) enter the high-temperature period on the 7th day, 6th day, 5th day, 5th day, and 6th day respectively. The high-temperature duration of Z3 is 11 days, and the high-temperature durations of Z1, Z2, Z4, Z5, and Z6 are 3 days, 7 days, 8 days, 9 days, and 9 days respectively. The highest temperature of the Z3 treatment is 55°C (on the 7th day), higher than other treatments. Therefore, adding the composite bacterial agent of the present invention can extend the high-temperature period and increase the temperature of the compost pile.

[0092] B. Change in pH during composting

[0093] The pH value of the distillers grains is between 3.4 and 4.0, and the final compost with a pH value between 6.5 and 7.5 is regarded as a mature compost. Therefore, the pH value increases during the distillers grains composting process. The change in pH value during the composting process is as Figure 2As shown, the pH values of each experimental group treatment increased during the composting process. The pH value of Z3 exceeded 6.5 on the 20th day, and the pH values of Z4, Z5, and Z6 exceeded 6.5 on the 25th day, the 25th day, and the 30th day respectively. The pH values of Z1 and Z2 were still below 6.5 on the 30th day. Therefore, the composite microbial agent of the present invention can shorten the composting cycle.

[0094] C. Changes in Electrical Conductivity (EC) during Composting

[0095] Electrical conductivity reflects the salinity of the compost substrate. Excessive soluble salts will have a negative impact on plant growth. It is generally considered that an electrical conductivity value below 4000 μs / cm will not cause toxicity to plants. The initial electrical conductivity of distiller's grains was 3930 μs / cm. Therefore, the electrical conductivity decreases during the composting process of distiller's grains. The changes in electrical conductivity during composting are as Figure 3 shown. The electrical conductivities of the six treatments all decreased gradually. The rate of decrease of Z3 was slightly higher than that of other treatments. At 30 days, the electrical conductivities of the six treatments were all below 4000 μs / cm and would not cause toxicity to plants.

[0096] D. Changes in Cellulose during Composting

[0097] For the six treatments, the cellulose content decreased. At the end of composting, the cellulose degradation rates of Z1, Z2, Z3, Z4, Z5, and Z6 were 19.62%, 24.08%, 33.36%, 29.71%, 27.63%, and 26.94% respectively. It shows that the addition of the microbial agent is beneficial to the degradation of cellulose during composting. The addition of the solid microbial agent of the strain of the present invention has a better effect on degrading cellulose than the common microbial agent, and the addition of the composite microbial agent has a better effect on degrading cellulose than the addition of a single microbial agent.

[0098] From the comparative experimental data of this example, it can be seen that the composite microbial agent provided by the present invention has a better composting effect than the commercial microbial agent or the microbial agent of a single strain in the prior art. It can effectively improve the composting efficiency and increase the cellulose degradation rate in distiller's grains.

[0099] From the above examples, it can be seen that the present invention provides a composite microbial agent for distiller's grains composting, which has the advantages of acid and high temperature tolerance, high composting efficiency, and high cellulose degradation rate, and has good application prospects.

Claims

1. A microorganism, characterized in that: it is a strain with the preservation number of CGMCC NO.40857, CGMCC NO.40858 or CGMCC NO.40859 preserved by the General Microbiology Center of the China Committee for Culture Collection of Microorganisms.

2. A compound microbial agent, characterized in that, comprising: Aspergillus fumigatus, Rhizomucor pusillus and Rasamsonia composticola, wherein the mass ratio of the solid microbial agents of Aspergillus fumigatus, Rhizomucor pusillus and Rasamsonia composticola is (1 - 5):(1 - 3):(1 - 3).

3. The compound microbial agent according to claim 2, characterized in that: the mass ratio of the solid microbial agents of Aspergillus fumigatus, Rhizomucor pusillus and Rasamsonia composticola is 1:1:

1.

4. The compound microbial agent according to claim 2, characterized in that: the homology of the ITS rDNA sequence of Aspergillus fumigatus and the ITS rDNA sequence of Aspergillus fumigatus with the GenBank number OP482428.1 is greater than 99%; and / or, the homology of the ITS rDNA sequence of Rhizomucor pusillus and the ITS rDNA sequence of Rhizomucor pusillus with the GenBank number KJ527032.1 is greater than 99%; and / or, the homology of the ITS rDNA sequence of Rasamsonia composticola and the ITS rDNA sequence of Rasamsonia composticola with the GenBank number JF417481.1 is greater than 99%.

5. The compound microbial agent according to claim 2, characterized in that: the Aspergillus fumigatus is a strain with the preservation number of CGMCC NO.40857 preserved by the General Microbiology Center of the China Committee for Culture Collection of Microorganisms; and / or, the Rhizomucor pusillus is a strain with the preservation number of CGMCC NO.40858 preserved by the General Microbiology Center of the China Committee for Culture Collection of Microorganisms; and / or, the Rasamsonia composticola is a strain with the preservation number of CGMCC NO.40859 preserved by the General Microbiology Center of the China Committee for Culture Collection of Microorganisms.

6. The compound microbial agent according to claim 2, characterized in that: the solid microbial agent is a solid obtained by culturing Aspergillus fumigatus, Rhizomucor pusillus and Rasamsonia composticola in a solid medium and then drying.

7. The preparation method of the compound microbial agent according to any one of claims 2 - 6, characterized in that, comprising the following steps: Step 1, respectively culture Aspergillus fumigatus, Rhizomucor pusillus and Rasamsonia composticola to obtain the cultures of the three strains; Step 2, dry and crush the cultures, and then mix them according to the ratio to obtain the product.

8. The preparation method according to claim 7, characterized in that: During the cultivation process of Step 1, the inoculation temperature is 30°C - 50°C; the cultivation temperature after inoculation is 35 - 45°C; and / or, in Step 1, the culture medium used for cultivation is composed of water and bran in a weight ratio of 0.6 - 0.9:1; and / or, in Step 1, the cultivation time is 2.5 days - 4 days; and / or, in Step 2, after the culture is dried, the water content is controlled at 10% - 12%.

9. Use of the compound microbial agent according to any one of claims 2 - 6 in distiller's grains composting.

10. A method for distiller's grains composting, characterized in that: After mixing distiller's grains, water and the compound microbial agent according to any one of claims 2 - 6, composting is carried out.

11. According to the method for distiller's grains composting described in claim 10, characterized in that: During the composting process, the water content is controlled at 50% - 60%; and / or, the addition amount of the compound microbial agent is 0.1% - 0.5% of the weight of distiller's grains; and / or, the composting time is 25 - 35 days.

Images