CN115109727A - A compound bacterial agent and its application in improving the quality of mushroom residue compost products - Google Patents

Abstract

The invention provides a composite inoculant and its application in improving the quality of mushroom residue compost products. The active components of the composite inoculant are Bacillus subtilis DPPG-26, Pseudomonas putida SRPG-396, Trichoderma reesei DGW1 and Microbacillus oxydans YD4. Both Bacillus subtilis DPPG-26 and Pseudomonas putida SRPG-396 in the composite inoculum of the present invention have strong phosphorus-dissolving ability, and Bacillus subtilis DPPG-26 has a wide suitable growth temperature, and can grow at 10- 60°C maintains high activity; Trichoderma reesei DGW1 and Microbacillus oxydans YD4 in the compound bacterial agent have strong cellulose degradation ability, and Trichoderma reesei DGW1 has strong ability to resist external harmful factors, It has strong enzyme production capacity in a wide pH (4.0-8.0) environment. The application of the compound inoculant realizes the rapid entry of the mushroom residue compost into the high temperature period, improves the compost temperature and the degree of composting, the total phosphorus content, available phosphorus content and humus of the compost product increase significantly, and the seed germination index is greater than 215%, effectively improving the compost product. quality.

Description

A compound bacterial agent and its application in improving the quality of mushroom residue compost products

technical field

The invention belongs to the technical field of environmental microorganisms, and relates to a compound bacterial agent and its application in improving the quality of mushroom residue compost products.

Background technique

At present, there are as many as 4 million tons of waste mushroom residues produced by the cultivation of shiitake mushrooms in China every year. If the mushroom residues are not disposed of reasonably and safely, such as incineration, landfill, open burning and random accumulation on the land, it will cause serious environmental problems. However, the mushroom residue contains a lot of nutrients, including polysaccharides, amino acids, hydrocarbons and trace elements, etc., which can be fully utilized as resources. At present, it has been reported that the use of fungus residues to develop useful products, such as organic fertilizers, green adsorbents, animal feed and biochar, etc. However, considering the economic effect and technical feasibility, most of the fungus residues are mainly used for the production of organic fertilizers, and only a small part is used for the production of other products.

The development of bio-organic fertilizers using mushroom residues to realize resource utilization is the trend of sustainable economic development. However, the conversion of mushroom residues into bio-organic fertilizers often has problems such as low degree of humification and low nutrient content. Nutrients are often biologically stabilized during composting, and the available phosphorus in the compost is often converted to moderately stable phosphorus, resulting in a significant reduction in the available phosphorus content of the compost product. In addition, the mushroom residue contains a large amount of lignocellulose, which is one of the important factors restricting the resource utilization of mushroom residue. At present, the biological treatment method of adding cellulose degrading bacteria is green, economical and effective, and is widely used. However, due to the unbalanced ratio of carbon and nitrogen nutrients in the waste residues and the large amount of cellulose, it is difficult to degrade the mushroom residues directly by adding general cellulose-degrading bacteria.

However, most of the currently commercially available compound inoculants are used in agricultural wastes with low lignocellulose content such as straw, and the degradation effect on the mushroom residues is not significant. In addition, the effect of improving the nutrient content of compost products is greatly reduced, which limits the utilization efficiency of nutrients in compost by plants. Therefore, it is particularly important to develop a high-efficiency cellulose-degrading compound inoculant for the characteristics of the refractory mushroom residue and the low nutrient content of its compost products.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a compound bacterial agent and its application in improving the quality of mushroom residue compost products, so as to solve the problems raised in the above background technology.

The object of the present invention can be realized through the following technical solutions:

A compound bacterial agent, which comprises the preservation number of CGMCC No.9393 Bacillus subtilis DPPG-26 (Bacillus subtilis), the preservation number of CGMCC No.9397 Pseudomonas putida SRPG-396 (Pseudomonas putida), Trichoderma reesei DGW1 (Trichodermareesei) and Microbacterium oxydans YD4.

Strain DPPG-26 has strong phosphorus-dissolving properties, and the dissolved amount of inorganic phosphorus is 60.58 mg/L. In addition, strain DPPG-26 has the ability to produce siderophil, fix nitrogen and secrete IAA; strain SRPG-396 also has relatively high solubility. Strong phosphorus solubility, the dissolved amount of inorganic phosphorus is 82.41mg/L, and it has strong salt tolerance; strain DGW1 and strain YD4 have high cellulose degradation ability, and their cellulase activities are 112.71U respectively /g and 9.74U/g; the results of the phylogenetic tree alignment of the ITS constructs showed that the strain DGW1 had the highest homology with Trichoderma. Combined with the phylogenetic tree alignment and morphological observations of the ITS constructs, the strain DGW1 was identified as Trichoderma reesei; according to the comparison results of the developmental tree of the 16S rDNA construction sequence, the strain YD4 has the highest homology with Microbacteria. Combined with the analysis results of the developmental tree construction of the 16S rDNA construction sequence and the physiological and biochemical shape, the strain YD4 was identified as Microbacterium oxydans.

Using the screened high-efficiency cellulose-degrading bacteria and functional strains with phosphorus-dissolving and salt-tolerance, 5 bacterial groups were combined by factorial design, and a total of 7 treatments together with the commercial inoculum control were used to determine the physical and chemical indicators and products of the 7 composting treatments. Nutrient content, high-efficiency compound bacterial agents were obtained, including Bacillus subtilis DPPG-26, Pseudomonas putida SRPG-396, Trichoderma reesei DGW1 and Microbacillus oxydans YD4.

The microbial combination of the present invention is applied in improving the quality of Lentinus edodes compost products.

A compound inoculum is composed of the Trichoderma reesei DGW1 bacterial solution described in a concentration of not less than ^{10 9 /} ml and a Bacillus subtilis DPPG-26 Bacillus subtilis SRPG- 26. The described Pseudomonas putida SRPG-396 and the described Microbacillus oxidans YD4 bacterial solution are mixed in equal volume ratio; wherein the concentration of each bacterial solution is the same.

Described compound bacterial agent, its physiological characteristic is:

(1) The number of effective viable bacteria of the strain is high, and the liquid is inoculated, the fungal concentration is above 10 ⁹ cells/ml, and the bacterial concentration is above 10 ⁹ CFU/ml;

(2) Bacillus subtilis DPPG-26 and Pseudomonas putida SRPG-396 have strong phosphorus-dissolving ability, and Trichoderma reesei DGW1 and Microbacillus oxydans YD4 have strong cellulose degradation ability;

(3) The strains contained in the compound inoculant are harmless to crops and non-pathogenic to humans and animals.

The preparation method of the compound bacterial agent is as follows: the Bacillus subtilis DPPG-26, the Pseudomonas putida SRPG-396 and the Microbacillus oxydans YD4 are respectively inoculated into the LB liquid medium, and cultured at 30° C. and 170 rpm for 2 days The strain Trichoderma reesei DGW1 was inoculated into the PDA medium, cultivated at 30°C for 3 days, and the medium was rinsed with distilled water to obtain a spore suspension; after the cultivation, the concentration was adjusted with distilled water, so that the bacterial concentration was 10 ⁹ CFU/ml or more, fungal spores more than 10 ⁹ /ml; then the four fermentation broths are mixed in equal volume ratios to obtain the compound bacterial agent.

Among them, the concentration of bacteria was calculated by the OD value, and the number of spores of fungi was counted with a hemocytometer.

A method for improving the quality of Lentinus edodes mushroom residue composting products by a compound bacterial agent, which comprises the following steps:

S1: Mixing of raw materials: Crush the shiitake mushroom residue to 2-3cm, then fully mix the crushed mushroom residue with chicken manure to form a uniform mixture with a C/N ratio of 20, and adjust the moisture content in the mixture to 50- 55%, the uniform mixture is placed in the composting foam box, and the mass ratio of mushroom residue to chicken manure in the mixture is 2:1;

S2: compound bacterial agent inoculation: inoculate the compound bacterial agent of the present invention in the uniform mixture, the inoculation amount is 1.5-2% of the mass of the fermentation raw material, and the material is fully mixed and fermented;

S3: Compost fermentation: bottom aeration is adopted, and the aeration rate is 0.4L·min ^-1 ·kg ^-1 . The first two weeks of the composting period are manually turned twice a week, and then once a week, for a total of 25-30 days of fermentation. , to obtain high-quality compost products.

Compared with the prior art, the advantages of a composite bacterial agent of the present invention and its application in improving the quality of Lentinus edodes mushroom residue compost products are: Bacillus subtilis DPPG-26 and Pseudomonas putida SRPG in the composite bacterial agent. -396 has a strong ability to dissolve phosphorus, and Bacillus subtilis DPPG-26 has a wide range of suitable growth temperatures and can maintain high activity at 10-60 ° C; Trichoderma reesei DGW1 and oxidative Microbacterium YD4 has strong cellulose degradation ability, and Trichoderma reesei DGW1 has strong ability to resist external harmful factors, and can have strong enzyme production ability in a wide pH (4.0-8.0) environment;

The compound bacterial agent of the present invention comprises Bacillus subtilis DPPG-26, Pseudomonas putida SRPG-396, Trichoderma reesei DGW1 and Microbacillus oxydans YD4, and is used for the decomposing and fermenting of refractory mushroom residues with complementary functions. And the synergistic effect is obvious, which can significantly prolong the mesophilic period of compost, and significantly increase the content of humus and available phosphorus in compost.

Description of drawings

Figure 1: Schematic diagram of the Congo red staining hydrolysis circles of strain DGW1 and strain YD4.

Figure 2: Schematic diagram of the filter paper disintegration test of strain DGW1 and strain YD4.

Figure 3: Schematic diagram of the phylogenetic tree constructed by strain DGW1 based on 18S rDNA sequence homology.

Figure 4: Schematic diagram of the phylogenetic tree constructed by strain YD4 based on 16S rDNA sequence homology.

Figure 5: Morphology of strain DGW1: (a) Morphology of strain DGW1; (b) Morphology of spores of strain DGW1; (c) Morphology of hyphae of strain DGW1;

Figure 6: Schematic diagram of compost temperature changes.

Fig. 7 Schematic diagram of pH and EC changes in compost.

Fig. 8 Schematic diagram of E4/E6 and GI changes during composting.

Fig. 9 Diagram of organic matter content and available phosphorus content at the end of composting.

Figure 10 Schematic diagram of compost temperature change.

Fig. 11 Changes of compost maturity indicators (a) TOC, (b) TN, (c) C/N, (d) NH ₄ ⁺ -N, (e) NO ₃ -N, (f) GI.

Figure 12 Graph of changes in total phosphorus and available phosphorus during composting.

Figure 13. Changes in the content of different phosphorus components during composting.

Figure 14. Bar graph of humus results comparing (a) HS, (b) HA, (c) FA during composting.

Detailed ways

The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

Example 1: Screening of efficient cellulose-degrading strains

Use a sterilized mortar to smash 10g of discarded bacterial residue, add it to 90mL of sterile water, continue to grind for 5min, shake and mix at 170r/min for 30min, after gradient dilution, draw 100μL of each and evenly spread on LB medium, Bengal red medium and modified Gao's No. 1 medium were placed at 28°C for inversion culture for 1-7 days, and the colony growth status was observed and recorded. Single colonies with different shapes and more were picked out, streaked for several times, purified, and preserved.

The strains screened from the rotten mushroom residues were inoculated into the medium with sodium carboxymethyl cellulose as the sole carbon source, and single colonies were selected for streak isolation and culture, and 35 strains with cellulose-degrading ability were obtained. After Congo red staining, as shown in Figure 1, it was found that the hydrolysis circles of strains DGW1 and YD4 were relatively large and clear. Combined with the filter paper disintegration test, the comprehensive cellulose degradation ability of the strain was further judged. The results of the filter paper disintegration experiment are shown in Figure 2. After 7 days of culture, it was found that both can degrade the filter paper to a paste. The enzyme activities of the two were determined to further determine their cellulose degradation ability. The results showed that the filter paper enzyme activity of strain DGW1 reached 112.71U/g, and the filter paper enzyme activity of strain YD4 reached 11.27U/g, confirming that both strains DGW1 and YD4 have strong fiber degrading ability.

Molecular biological identification of strains DGW1 and YD4. The gene of strain DGW1 was extracted and amplified by PCR, and the amplified product was subjected to agarose electrophoresis. BLASTN was used for sequence similarity alignment, and DGW1 (Fig. 3) and YD4 were classified and identified (Fig. 4). Through the morphological observation of the strain (Fig. 5), it was confirmed that the strain DGW1 was Trichoderma reesei, and the physiological and biochemical characteristics of the strain YD4 were determined (Table 1), and the strain YD4 was confirmed to be Microbacterium oxydans. Table 1 Physiological and biochemical indicators of strain YD4

Embodiment 2: the creation of compound bacterial agent and its application in shiitake mushroom residue composting

A total of 7 treatments were designed in this experiment, 5 bacterial groups were combined by factorial design, and a total of 7 treatments together with the commercial inoculum control, see Table 2 for details; the initial moisture content of each treatment was adjusted to 50-55%, and put into compost. In the foam box, the bottom of the compost was aerated, and the compost was manually turned twice a week for the first two weeks of the composting process, and once a week thereafter. Changes in compost temperature were measured during composting and samples were taken to measure changes in compost physicochemical properties.

The purchased commercial inoculants include cellulose-degrading bacteria such as Bacillus subtilis, Bacillus licheniformis, Bacillus lateralis, and Lactobacillus plantarum.

Table 2 The creation of compound inoculants with different treatments and the application of inoculum of compost

Analysis of composting process results

The change in temperature throughout the composting process is shown in Figure 6. The temperature of CK and T6 treatments exceeded 55℃ on the 3rd day (the mesophilic stage), and the other inoculation treatments entered the mesophilic stage on the 2nd day. The mesophilic periods of T1 and T5 remained the longest (6d), followed by T2, T3 and T4 (5d), and the shortest mesophilic periods were CK (3d) and T6 (4d). Among them, the mesophilic period of T1, T2, T3, T4 and T5 exceeded 5d, which met the compost harmless standard. In addition, when the compost temperature is lower than 40 ℃, it indicates that the compost has matured. Among all treatments, T5 treatment (13d) was the fastest to enter the decomposing stage, which was 2d shorter than CK. Therefore, it can be preliminarily judged that the inoculum-agent combination T5 treatment can improve the composting efficiency, which has a longer mesophilic period.

During composting, changes in pH during composting are caused due to microbial ammoniation and mineralization. The pH of each treatment in the present invention increased from 6.42, 6.8, 6.57, 6.75, 6.58, 6.73 and 6.33 to 8.02, 8.06, 8, 8.07, 8.16, 8.13 and 8.07, respectively (Fig. 7a). During the mesophilic period of composting, the pH value of the T5 and T6 treatments rose faster, implying that the two treatments had higher microbial activity. According to the TMECC, 2002 standard, the pH value of decomposed compost should be 5.5–8.5, and the pH value of all treatments in this example can meet this requirement.

EC directly reflects the salt content of compost and the toxicity of compost products. Compost products are considered non-toxic when EC<4mS/cm. At the end of composting, the EC dropped to 3.3, 2.8, 3.05, 2.9, 2.95, 3.04 and 3.18 for each treatment (Fig. 7b). This is opposite to the trend of pH value change. The EC content was the lowest in the T5 treatment, which indicated that the T5 treatment would convert a large amount of small-chain organic acids and various ions into stable compounds during the decomposing stage. Therefore, T5 microbial inoculum can promote the maturation of compost.

The humic substances in compost products mainly include humic acid and fulvic acid. The ratio of the optical density of humic acid and fulvic acid (E4/E6) can reflect the degree of binding of the aromatic structure of humus, indicating the level of humus and the level of compost maturity. In short, higher E4/E6 values mean lower compost maturity. The changes in E4/E6 during composting are shown in Fig. 8a. The final E4/E6 for all treatments were 7.06, 6.5, 6.22, 6.25, 7.05, 6.15 and 7.11, respectively. The E4/E6 of the inoculated group was lower than that of the CK treatment, which indicated that the inoculation of microbial inoculants in the compost promoted the formation of humus and improved the compost maturity. Among them, the T5 treatment had the lowest E4/E6, which means that the inoculant combination of the T5 treatment can effectively improve the compost maturity.

The GI of each treatment showed a gradually increasing trend (Fig. 8b), which indicated that the biotoxicity of the compost was gradually decreasing as the composting progressed. Since the composting raw materials are dry chicken manure and dry fungus residue, the toxicity of the composting raw materials itself is not high, so the GI exceeds 80% in the initial stage of composting. The GI of T5 treatment reached a maximum of 215 at the end of composting, which indicated that the microbial inoculum inoculated with T5 treatment promoted compost maturity and reduced compost toxicity.

Figure 9a shows the organic matter content at the end of composting, and the organic matter content of T5 treatment was significantly lower than that of other treatments. The organic matter loss rate of the inoculum combination in T5 treatment was the largest, indicating that microorganisms used organic matter for active growth and reproduction during composting, which also indirectly indicated that T5 treatment could prolong the mesophilic period of composting (Fig. 9a). When the organic matter content of the compost drops to 60%, it can be considered that the unstable organic matter of the compost has been completely degraded, and finally the compost is mature and stable. Therefore, all treatments in this test can be considered to have reached maturity.

Since the T5-treated inoculum combination resulted in the highest organic matter degradation rate, the T5 level also had the highest available phosphorus content (Fig. 9b). The effective phosphorus content of the inoculated microbial inoculum was significantly higher than that of the control group, which may be because there may be a certain synergy between the microbial inoculum and the indigenous microbial flora, which can better play the role of phosphorus release.

The composting treatment application of the compound bacterial agent of embodiment 3

A total of 2 treatments were designed in this experiment to further verify the effect of compound inoculants on the composting of mushroom residues. A total of 2 treatments were designed with SL-44+Rs-198+YD4+DGW1 compound inoculants (CMA) and commercial inoculants (CK). ; Adjust the concentration with distilled water, so that the bacterial concentration is above 10 ⁹ CFU/ml, and the fungal spore is above 10 ⁹ /ml; Then the four fermentation broths are mixed according to the volume ratio of 0.8: 1.2: 0.8: 1.2 to obtain a composite bacterial agent .

Design of mushroom residue raw materials: Crush the mushroom residue to 2-3cm, then fully mix the crushed mushroom residue with sheep dung to form a uniform mixture with a C/N ratio of 20, and adjust the moisture content in the mixture to 55- 60%, place the homogeneous mixture in a composting foam box, and the mass ratio of shiitake mushroom residue to sheep manure in the mixture is 2:1.2.

Compound bacterial agent inoculation: the compound bacterial agent of the present invention is inoculated into the uniform mixture, and the inoculation amount is 1.5% of the mass of the fermentation raw material, and the material is fully mixed before fermentation.

Compost fermentation: bottom aeration was adopted, and the aeration rate was 0.4L·min ^-1 ·kg ^-1 . During the first two weeks of the composting period, the compost was manually turned twice a week, and then turned once a week, for a total of 25-30 days of fermentation to obtain High quality compost product. Sampling was carried out on the 0th, 1st, 5th, 20th, and 30th day of the composting period, respectively, and the physical and chemical properties of the compost were measured when the composting temperature changed.

Analysis of the results of various indicators in the composting process

After the composting process continued for 30 days, the compost temperature was close to room temperature. Both CK treatment and CMA treatment could enter the mesophilic phase (>55°C) on the 1st day, but the CMA treatment could reach a higher temperature level (66°C) on the 6th day than the CK treatment (61°C). In addition, both treatments can be maintained at high temperature (>55 °C) for 13 d. During the thermophilic period, a large number of pathogenic bacteria and toxic substances are inactivated, and organic matter is rapidly decomposed. Subsequently, the temperature of the compost continued to drop, indicating that the compost was gradually mature. When the temperature of the heap tends to room temperature, it indicates that the microorganisms in the heap basically stop degrading activities, and the compost tends to mature.

As shown in Table 3, the moisture content of both treatments decreased continuously as the composting progressed. During the mesophilic period of composting, a large amount of heat is generated due to the metabolism of composting microorganisms, causing a large amount of water in the compost to evaporate. However, the water content of CMA treatment was significantly lower than that of CK treatment, because CMA treatment had higher temperature and longer mesophilic period than CK treatment. During the maturity and cooling periods of the compost, the temperature of the compost tends to room temperature, and the moisture content in the compost tends to be stable.

As composting progressed, the pH of the CK and CMA treatments exhibited a weakly alkaline range of 6.92-8.40 and 7.06-8.23, respectively (Table 3). During the composting period, the pH value of the two treatments increased continuously. After 11 d of composting, the pH value of the composted compost increased significantly, which may be due to the formation of organic acids in the compost. In the early stage of composting, the pH value of the compost in the CMA treatment was higher than that in the CK treatment, which may be due to the fact that the inoculum was in an alkaline state during the cultivation process, thereby increasing the initial pH value of the compost. At the end of the composting stage, the pH value of the CMA treatment was lower than that of the CK treatment, which may be due to the inoculation of the compound bacterial agent, which promoted the secretion of organic acids by microorganisms in the composting habitat.

The electrical conductivity (EC) of CK treatment and CMA treatment fluctuated continuously in the range of 1.40-2.212 (Table 3), and the final EC of both treatments met safety standard requirements (<4 mS/cm).

Table 3 Changes in physicochemical parameters in composting

Figure 11a shows changes in total organic carbon (TOC) during composting. During the mesophilic period of composting, the TOC content decreased significantly. After 30 d of composting, the TOC content of CMA treatment was lower than that of CK treatment, which may be due to the higher microbial activity of this treatment.

The total nitrogen (TN) of CK and CMA treatments gradually increased during composting, but part of nitrogen was excreted out of the compost in the form of ammonia gas during composting (Fig. 11b). And the changes of total nitrogen in the two treatments had similar results. At the end of composting, the total nitrogen content of the CMA treatment was significantly higher than that of the CK treatment, indicating that the inoculation of the compound bacterial agent would reduce the loss of nitrogen in the compost.

C/N is an important index in compost, which can reflect the maturity of compost. As shown in Fig. 11c, C/N gradually decreased during composting, which may be due to the higher mineralization rate of organic carbon than organic nitrogen during composting. According to previous reports, C/N in the final stage of composting is 10-15, and it can be considered that the compost has been decomposed. Therefore, both treatments were fully decomposed.

As shown in Fig. 11d, the NH ₄ ⁺ -N content of the two treatments showed a trend of first increasing and then decreasing throughout the composting process. Ammonia gas is produced by ammoniation and subsequently dissolved in water, thereby increasing the NH ₄ ⁺ -N content of the compost. With the volatilization of ammonia and the conversion of NH ₄ ⁺ -N to NO ₃ ^- -N, the NH ₄ ⁺ -N content in the compost began to decrease. When entering the cooling period, the NH ₄ ⁺ -N content tends to be stable. The NH ₄ ⁺ -N content was relatively stable at the later stage of maturity. Compared with the CK treatment, the overall NH ₄ ⁺ -N content was higher in the CMA treatment, which was due to the higher temperature and pH favoring the ammoniation.

Figure 11e shows the change of NO ₃ ^- -N content during composting, and the NO ₃ ^- -N content showed a gradually increasing trend throughout the composting process. In the early stage of composting, the content of NO ₃ ^- -N increased slowly. After the end of the mesophilic period, nitrifying microorganisms proliferated, and the NH ₄ ⁺ -N in the compost was converted into NO ₃ ^- -N, resulting in a gradual increase in the content of NO ₃ ^- -N in the compost. , which indicates that the compost is gradually maturing. At the end of composting, the content of NO ₃ ^- -N in the CMA treatment was higher than that in the CK treatment, which may be because the inoculation of the compound bacterial agent promoted the growth and metabolism of nitrifying bacteria. It can be seen that the inoculation of mixed bacterial agent can effectively improve the quality of compost products.

The GI of both treatments showed an upward trend throughout the composting process (Fig. 11f). At the same time, the GI of both treatments at the end of composting exceeded 200%, which could meet the compost maturity standard (>80%). In addition, the seed germination rate of CMA treatment was significantly higher than that of CK treatment, indicating that the inoculation of compound inoculants will improve the compost maturity, which may be related to the improvement of the metabolic activity of microorganisms in the compost and the positive interaction between microorganisms.

As shown in Figure 12a, compared with the initial stage of composting, the final total phosphorus concentration in the CK treatment and CMA treatment increased by 27.02% and 33.15%, respectively. It can be seen that the inoculation of the compound bacterial agent increased the total phosphorus content of the final composting product. The available phosphorus content of both treatments increased continuously throughout the composting process, but the available phosphorus concentration (Olsen-P) of the CMA treatment was significantly higher than that of the CK treatment (Fig. 12b). The compound inoculant indirectly affects the content of phosphorus components in compost by improving the interaction between microorganisms.

The sequential extraction of phosphorus in different extracting solutions reflects the changes of unstable phosphorus, relatively unstable phosphorus, relatively stable phosphorus and stable phosphorus during the composting process, which also reflects the solubilization degree of inorganic phosphorus by compound inoculants during the composting process. Figure 13 shows the distribution of different phosphorus components during composting. During composting, except for HCl-Po, other phosphorus components were increased in both CK and CMA treatments, which may be due to concentration effects and degradation of organic matter. The available phosphorus included H ₂ OP and NaHCO ₃ -P in the compost, which were increased by 0.29% and 1.5% in the CMA treatment at the end of composting, respectively, compared with the CK treatment. HCl-P was the most unstable P in the phosphorus component, and it was found that the CK treatment was higher than the CMA treatment at the end of the composting stage, which means that the addition of the compound inoculant was beneficial to the conversion of stable phosphorus into available phosphorus. And the residual phosphorus of the CMA treatment was higher than that of the CK treatment as a whole.

Humification, the process of converting organic matter into humus (HS), is also a key step in compost carbon sequestration, which directly affects compost fertility and stability. During the composting process, the HS of CMA treatment and CK treatment decreased from 120.18 g/kg to 114.18 g/kg and from 118.16 g/kg to 104.17 g/kg, respectively (Fig. 14a). Notably, the HS content of the CMA treatment at the end of composting was significantly higher than that of the CK treatment

Humic acid (HA) is a substance with large molecular weight and high stability in HS, and contains various functional groups such as carboxyl group and phenolic hydroxyl group. As composting progressed, the HA of both treatments increased gradually (Fig. 14b). At the end of composting, the HA in CMA treatment and CK treatment increased to 34.37% and 31.86%, respectively, which means that CMA treatment had higher microbial activity, and microorganisms synthesized a large number of stable HA molecules.

Fulvic acid (FA) has the characteristics of small molecular weight, high activity and high degree of oxidation, which means that FA produced in compost is easier to be metabolized and absorbed by microorganisms than HA. Therefore, during the composting process, the FA of both treatments decreased continuously (Fig. 14c). At the end of composting, the FA of CMA treatment was slightly higher than that of CK treatment, but the inoculation of CMA inoculum had no significant effect on FA content.

Contents not described in detail in this specification belong to the prior art known to those skilled in the art. The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which the present invention pertains can make various modifications or additions to the described specific embodiments or substitute in similar manners, but will not deviate from the spirit of the present invention or go beyond the definition of the appended claims range.

Claims (6)

1. The compound microbial inoculum comprises active ingredients of the compound microbial inoculum, wherein the active ingredients of the compound microbial inoculum comprise bacillus subtilis DPPG-26, pseudomonas putida SRPG-396, trichoderma reesei DGW1 and microbacterium oxydans YD 4.

The compound microbial inoculum is prepared from the compound microbial inoculum with the concentration of not less than 10 ⁹ Bacterial/ml Trichoderma reesei DGW1 bacterial liquid and concentration not less than 10 ⁹ CFU/ml Bacillus subtilis DPPG-26, Pseudomonas putida SRPG-396 and oxidizingThe microbacterium YD4 is mixed in equal volume ratio; wherein the concentration of each bacterium liquid is the same; wherein:

the compound microbial inoculum is prepared by the following method: respectively inoculating the bacillus subtilis DPPG-26, the pseudomonas putida SRPG-396 and the microbacterium oxydans YD4 into an LB culture medium, and culturing at 30 ℃ and 170rpm for 48-50 h; inoculating the strain Trichoderma reesei DGW1 into a PDA culture medium, culturing at 30 ℃ for 72-75h, and repeatedly flushing the culture medium with distilled water to obtain spore suspension; adjusting the concentration with distilled water to make the bacteria concentration at 10 ⁹ CFU/ml or above, fungal spore is 10 ⁹ More than one per ml; then, mixing the four fermentation liquors according to the volume ratio of 0.8-1.2: 0.8-1.2: 0.8-1.2: 0.8-1.2, and mixing to obtain the composite microbial inoculum.

2. The complex microbial inoculum according to claim 1, wherein the preservation number of the bacillus subtilis DPPG-26 is CGMCC No. 9393; the strain preservation number of the pseudomonas putida SRPG-396 is CGMCC No. 9397.

3. The complex microbial inoculum of claim 1, wherein the trichoderma reesei DGW1 and the microbacterium oxydans YD4 are obtained by screening waste mushroom dregs and have high-efficiency cellulose degradation capability.

4. The application of the compound microbial inoculum in improving the quality of mushroom fungus residue compost products is applied to mushroom fungus residue compost raw materials, wherein the compost raw materials further comprise one or more of chicken manure and sheep manure.

5. The method for treating mushroom dregs by using the composite microbial inoculum is characterized by comprising the following steps of:

s1: grinding the mushroom dregs to 2-3cm, and then fully mixing the ground mushroom dregs with the chicken manure or the sheep manure to form a uniform mixture with a C/N ratio of 1.8-2.0, wherein the mass ratio of the mushroom dregs to the chicken manure or the sheep manure is 2: 1.0-2: 1.2, adjusting the water content in the mixture to 50-60%;

s2: adding a complex microbial inoculum into the mixture, wherein the addition amount of the complex microbial inoculum is 1.5-2% of the mass of the fermentation raw materials, and fermenting after fully and uniformly mixing the materials;

s3: and (3) adopting bottom aeration, manually turning the compost twice every week in the first two weeks during the composting period, then turning the compost once every week, and fermenting for 25-30 days to obtain a high-quality compost product.

6. The method for treating mushroom dregs by using the composite microbial inoculum according to claim 5, wherein the application of the composite microbial inoculum realizes that mushroom dregs compost quickly enters a high-temperature period, the compost temperature and the decomposition degree are improved, the total phosphorus content, the available phosphorus content and humus of a compost product are obviously increased, the seed germination index is more than 215%, and the quality of the compost product is effectively improved.

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