Application of kaolin to reduction of antibiotic resistance propagation risk of compost product

Abstract

The invention discloses application of kaolin to reduction of antibiotic resistance propagation risk of compost products, only kaolin is added into livestock and poultry manure compost fermentation raw materials for aerobic composting, and the expression abundance of ARGs and MGEs in the compost products is reduced based on the unique antibacterial activity of kaolin to human pathogenic bacteria.

Description

Technical Field

[0001] The present invention belongs to the technical field of biochemical toxicity risk suppression in solid waste, and particularly relates to an application of kaolin in reducing the risk of antibiotic resistance transmission in compost products. Background Art

[0002] Livestock and poultry manure is an important source of organic fertilizer in agricultural production. However, applying untreated or incompletely composted manure to farmland soil can cause significant damage to crops, resulting in seedling burns and root smoke. Furthermore, livestock and poultry manure contains numerous pathogens and parasite eggs, and applying it directly as organic fertilizer can spread pests and diseases, as well as human illnesses. Aerobic composting kills pathogens and parasite eggs before application. Furthermore, with the assistance of microorganisms, it also decomposes and transforms macromolecular organic matter into a stable, mature humus-like substance.

[0003] However, traditional aerobic composting models have numerous drawbacks. Direct application of animal manure containing antibiotic residues to farmland increases the abundance and diversity of ARGs in the soil, increasing the risk of interspecies heterogeneous growth (HGT) between species and leading to resistance of some clinical pathogens to human antibiotics. Studies have shown that ARGs in clinical pathogens may originate from bacteria in the farmland environment. For example, the CTX-Ms gene in infectious Klebsiella species may originate from different Klebsiella species in the soil. Therefore, controlling the spread of ARGs and ARB contamination is crucial for ensuring the safe reuse of livestock and poultry manure.

[0004] Existing research has shown that the use of additives such as biochar, bamboo charcoal, and bamboo vinegar can reduce the abundance of ARGs during composting. However, these additives are expensive and difficult to recycle, making their practical application difficult.

[0005] Kaolin is an inexpensive clay mineral. Its typical applications are the removal of antibiotics (such as norfloxacin) from water and the reduction of heavy metal selection pressure. Both applications are based on its adsorption properties. Common sense suggests that applications based on adsorption generally require higher usage levels. Summary of the Invention

[0006] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide an application of kaolin to reduce the risk of antibiotic resistance transmission in compost products. This is a new use of kaolin. When used in composting, it can reduce the risk of antibiotic resistance transmission in compost products at a low cost and improve the quality of compost products.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] An application of kaolin to reduce the risk of antibiotic resistance transmission in compost products. Only kaolin is added to the livestock and poultry manure compost fermentation raw materials for aerobic composting. Based on the unique antibacterial activity of kaolin against human pathogens, the expression abundance of ARGs and MGEs in the compost product is reduced.

[0009] In one embodiment, the livestock and poultry manure composting fermentation raw material is a mixture of fresh livestock and poultry manure and straw with sterile water added to adjust the moisture content. For example, the livestock and poultry manure is pig manure, and the straw is wheat straw.

[0010] In one embodiment, the moisture content of livestock and poultry manure is 77±3%, the total carbon content is 405±5 g / kg, and the total nitrogen content is 20±1 g / kg; the moisture content of straw is 6±1%, the total carbon content is 413±5 g / kg, and the total nitrogen content is 10±2 g / kg, and the C / N and moisture content of the mixture are adjusted to 25-30:1 and 50-60%, respectively.

[0011] In one embodiment, the amount of kaolin added is 1% by weight of the dry weight of the compost fermentation raw materials.

[0012] In one embodiment, the aerobic composting is carried out by natural fermentation and decomposition in a reaction vessel, during which ventilation and oxygen supply are regularly performed and the compost is turned to ensure sufficient oxygen content and avoid the formation of an anaerobic microenvironment. The entire composting process lasts for 35±3 days.

[0013] In one embodiment, the total relative abundance of ARGs transcripts in the compost product is reduced by 0.99 log compared to the blank treatment.

[0014] In one embodiment, the transcript abundances of tetM, tetW, and tetO among the ARGs were reduced by 98.9%, 99.9%, and 99.8%, respectively, after composting.

[0015] In one embodiment, the total expression level of intI1 and intI2 in the compost product MGEs was downregulated by 0.98 log compared with the blank treatment.

[0016] The principles of the present invention are as follows:

[0017] Composting is a well-known sustainable practice that can reduce the abundance of ARGs in livestock and poultry manure. Kaolin is an inexpensive clay mineral with a wide range of applications in the environmental field. Studies have shown that kaolin has unique antimicrobial activity against human pathogenic bacteria (HPB), and the composition of bacterial communities is affected by kaolin. Kaolin has an extremely high inhibition rate (99.3-100.0%) on the growth of different resistant Escherichia coli. Kaolin treatment is simple to implement in the composting process, cost-effective, and has high efficiency in removing ARGs at the transcriptional level. The addition of kaolin inhibits the transfer of ARGs by downregulating the expression of MGEs, thereby reducing the risk of antibiotic resistance transmission in compost products.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The main raw materials used in the present invention involve agricultural solid waste livestock and poultry manure and crop straw, which are made into organic fertilizer through composting, thereby realizing the resource utilization of agricultural waste.

[0020] (2) In the present invention, wheat straw is used as a compost conditioner, and its appropriate length of 2-3 cm (obtained by manual cutting) helps promote the degradation of refractory organic matter by microorganisms during the composting process, thereby promoting the fermentation process of the composting reaction.

[0021] (3) Adding a very small amount of kaolin (typically 1%) reduced the total relative abundance of ARGs transcripts by 0.99 log. In addition, the total expression levels of intI1 and intI2 in MGEs were downregulated by 0.98 log after kaolin treatment.

[0022] (4) Kaolin is a cheap clay mineral that is widely used in the environmental field. Its addition to compost further realizes the recycling of resources, improves the agricultural value of compost products, and has important practical significance for the application and promotion of compost products.

[0023] At the same time, the equipment used in the present invention has a simple structure, the additives are green and low-cost, the overall operation is convenient and simple, and the compost product is stable and safe. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of a composting device of the present invention.

[0025] Figure 2 It is the change in the relative abundance of ARGs transcripts after the composting process of the present invention.

[0026] Figure 3 It is the change of the expression level of ARGs and MGEs after the composting process of the present invention. DETAILED DESCRIPTION

[0027] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0028] In order to reduce the risk of antibiotic resistance transmission in compost products, the present invention uses kaolin as an auxiliary additive to study the effect of kaolin on the expression level of ARGs during the composting process, providing a theoretical basis and technical support for the resource utilization and promotion of livestock and poultry manure.

[0029] In the following examples, a mixture of fresh pig manure and wheat straw was used as a raw material for livestock and poultry manure composting fermentation, and kaolin was added as an additive for aerobic composting to study the effect of kaolin on the expression levels of ARGs and MGEs in the compost product.

[0030] refer to Figure 1 As shown, in the embodiment of the present invention, composting is carried out in a reaction barrel 1 with a working volume of approximately 60L (58cm high, 40cm in diameter). The bottom of the reaction barrel 1 is connected to a forced aeration device 2 for timed ventilation at a ventilation rate of 0.35L / kg(DW) / h. A thermometer 3 is installed on the side wall to monitor the temperature inside the barrel in real time. The total carbon, total nitrogen content, and moisture content of the fresh pig manure and wheat straw used for composting were measured as follows:

[0031] Fresh pig manure has a moisture content of 77±3%, a total carbon content of 405±5g / kg, and a total nitrogen content of 20±1g / kg;

[0032] The moisture content of wheat straw is 6±1%, the total carbon content is 413±5g / kg, and the total nitrogen content is 10±2g / kg.

[0033] Mix fresh pig manure and wheat straw in a weight ratio of 3.85:1, adjusting the initial C / N ratio of the entire compost system to 25:1. Add sterile water to maintain a moisture content of around 60%. When using, shred the wheat straw into 2-3 cm pieces.

[0034] The experiment involved three treatments: a control (CK) with no kaolin added, and four other treatments, designated T1, T2, T3, and T4, with kaolin added at 0.5%, 1%, 1.5%, and 2% of the dry weight of the compost. The composting process, which lasted 35 days, was conducted under natural fermentation. The compost was manually turned regularly until mature, ensuring adequate oxygen levels throughout the system and preventing the development of an anaerobic microenvironment. Maintaining a compost temperature above 55°C for three days or above 50°C for five to seven days met the hygienic standards for compost safety.

[0035] The study found that only expressed antibiotic resistance genes (ARGs) are functionally "active" genes, showing antibiotic resistance characteristics, and their health risks at the transcriptional level should be taken seriously. After composting, the total relative abundance of ARGs transcripts in the treatment with 1% kaolin was significantly decreased compared with day 0 (P < 0.05), decreasing by 0.68 log, and also significantly decreased compared with the control group (CK) (P < 0.05), decreasing by 0.99 log. Figure 2 As shown. Therefore, the addition of 1% kaolin significantly downregulated the expression of ARGs. Compared with day 0, the addition of 1% kaolin can significantly reduce the expression of most high-risk resistance genes. This treatment has the best effect on tetM, tetW and tetO among the high-risk resistance genes. The abundance of their corresponding transcripts decreased significantly after composting (P<0.05), decreasing by 98.9%, 99.9% and 99.8%, respectively. Figure 3 As shown in the figure. Furthermore, after adding 1% kaolin, the total expression levels of intI1 and intI2 among MGEs were downregulated by 0.98 log compared to the blank treatment. In summary, adding 1% kaolin can effectively reduce the expression abundance of high-risk ARGs and MGEs in compost products, thereby reducing the risk of antibiotic resistance transmission in compost products. Furthermore, kaolin treatment is simple to implement and cost-effective during the composting process, and its addition to compost further promotes resource recycling.

Claims

1. An application of kaolin to reduce the risk of antibiotic resistance transmission in compost products, characterized in that: Only adding kaolin to the livestock and poultry manure compost fermentation raw materials for aerobic composting can reduce the expression abundance of ARGs and MGEs in the compost product.

2. The use of kaolin according to claim 1 to reduce the risk of spreading antibiotic resistance in compost products, characterized in that: The livestock and poultry manure composting fermentation raw material is a mixture of fresh livestock and poultry manure and straw with sterile water added to adjust the moisture content.

3. The use of kaolin to reduce the risk of antibiotic resistance transmission in compost products according to claim 2, characterized in that: The livestock and poultry manure has a moisture content of 77±3%, a total carbon content of 405±5 g / kg, and a total nitrogen content of 20±1 g / kg; the straw has a moisture content of 6±1%, a total carbon content of 413±5 g / kg, and a total nitrogen content of 10±2 g / kg, and the C / N and moisture content of the mixture are adjusted to 25-30:1 and 50-60%, respectively.

4. The use of kaolin to reduce the risk of spreading antibiotic resistance in compost products according to claim 2 or 3, characterized in that: The amount of kaolin added is 1% by weight of the dry weight of the compost fermentation raw materials.

5. The use of kaolin to reduce the risk of spreading antibiotic resistance in compost products according to claim 4, characterized in that: The aerobic composting is carried out in a reaction vessel through natural fermentation and decomposition. During the process, ventilation and oxygen supply are carried out regularly and the compost is turned to ensure sufficient oxygen content and avoid the formation of an anaerobic microenvironment. The entire composting process lasts for 35±3 days.

6. The use of kaolin to reduce the risk of antibiotic resistance transmission in compost products according to claim 4, characterized in that: The fresh livestock and poultry manure is fresh pig manure, and the straw is wheat straw.

7. The use of kaolin to reduce the risk of spreading antibiotic resistance in compost products according to claim 6, characterized in that: The total relative abundance of ARGs transcripts in compost products was reduced by 0.99 log compared with the blank treatment.

8. The use of kaolin to reduce the risk of spreading antibiotic resistance in compost products according to claim 6, characterized in that: The transcript abundances of tetM, tetW, and tetO among the ARGs decreased by 98.9%, 99.9%, and 99.8%, respectively, after composting.

9. The use of kaolin to reduce the risk of spreading antibiotic resistance in compost products according to claim 6, characterized in that: The total expression levels of intI1 and intI2 in the compost product MGEs were downregulated by 0.98 log compared with the blank treatment.

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