Compost with high content of nicotinic acid and nicotinamide and preparation method thereof

Abstract

The invention relates to a composting method for producing high-content nicotinic acid and nicotinamide. The method for preparing the compost comprises the following steps: (1) selecting dry pig manure as a compost raw material; (2) crushing corn straws and tobacco stems into small blocks, and fully mixing the small blocks as a bulking agent with the dry pig manure to obtain a pig manure mixture; and (3) adding a rapid decomposition inoculant into the mixture, and aerating the reactor at the same time to finally prepare the compost with high content of nicotinic acid and nicotinamide. The invention innovatively provides a functional microbial inoculum prepared by adding functional organic wastes and screening dominant strains in a pile body in situ, and the biological fertilizer with personalized nutrients is produced. The research of the invention provides theoretical support for synergistic conversion of multi-element organic wastes, directional screening of microbial agents and preparation of biological fertilizers with personalized nutrients.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of compost production, in particular to a compost with high content of nicotinic acid and nicotinamide and a preparation method thereof, and particularly to a method for resource utilization and production of personalized nutrient compost from organic wastes such as pig manure, corn straw and tobacco stems. BACKGROUND

[0002] With the rapid development of economic society, China is experiencing the world's largest and fastest urbanization process. As the world's most populous country, it is estimated that by 2050, China's urbanization rate will increase to 80% to 90%. This transformation cannot be achieved without the strong support of the agricultural system. At the same time, the scale of China's livestock breeding industry continues to expand, and the number of pigs, beef cattle, sheep and poultry slaughtered in 2022 reached 699 million, 48.4 million, 336 million and 16.14 billion, respectively, which not only guarantees meat supply but also brings a large amount of organic waste such as livestock manure, with an annual output of nearly 3.8 billion tons, and the comprehensive utilization rate is still less than 60%. It is worth noting that in the process of promoting the combination of breeding and planting, not only livestock manure is produced in the breeding link, but also a large amount of straw waste is produced in the planting link, making the sources of organic waste increasingly diversified. These wastes contain rich nutrients such as nitrogen, phosphorus and potassium, and have significant resource potential, but if not properly treated, they can easily produce nitrogen and sulfur-containing malodorous gases, causing environmental pollution. In the face of diverse and complex organic waste, traditional single treatment mode has been difficult to meet the actual demand. Promoting the coordinated treatment of livestock manure and straw and other multi-element organic waste, such as comprehensive utilization through mixed composting, is becoming an effective path to improve the resource utilization efficiency of waste and achieve sustainable agricultural development.

[0003] In the current agricultural waste treatment system, composting is a widely used biological treatment method that converts organic waste into stable, harmless and humus-rich organic fertilizer through the degradation of bacteria, fungi and other microorganisms. This process can be divided into three stages of temperature change: heating, high temperature and cooling, and specific microbial communities participate in the decomposition of organic matter at each stage. Compost products can effectively improve soil structure, enhance fertility, and promote crop growth. However, traditional compost products are rich in humus and inorganic salts, but there is a significant lack of functional organic components such as nicotinic acid and nicotinamide, which are vitamins. These substances play an important role in plant growth, not only participating in energy metabolism and redox reactions, but also having a positive regulatory effect on root development and stress resistance. Therefore, in the process of promoting the coordinated composting of livestock manure and straw and other multi-element organic waste, how to improve the content of plant beneficial components such as nicotinic acid and nicotinamide in compost products has become a key direction to improve the resource utilization value of compost and the sustainable development ability of agriculture.

[0004] In the above background, it is worth noting that tobacco waste, especially tobacco stems, contains a certain amount of nicotine. During composting, nicotine can be gradually converted into nicotinic acid and nicotinamide by the degradation of certain microorganisms, both of which are essential vitamin components for plant growth. Nicotinic acid is involved in energy metabolism and redox processes in plants, and has a promoting effect on leaf development and photosynthesis; nicotinamide, as a component of various coenzymes, plays an important regulatory role in root development and stress resistance enhancement. However, the conversion efficiency of nicotine under natural composting conditions is usually low. To promote the process, targeted strengthening can be achieved by inoculating high-temperature microbial inoculants. High-temperature inoculants not only tolerate the temperature environment during the high-temperature stage of composting, but also effectively degrade alkaloids such as nicotine during the warming and high-temperature stages, converting them into usable nicotinic acid and nicotinamide. The introduction of such inoculants not only enhances the synthesis of functional components during composting, but also strengthens the system's ability to co-process multiple wastes such as tobacco stems, livestock and poultry manure, and straw, providing a new technical path for producing high-value bio-organic fertilizers.

[0005] In the prior art, composting of multiple organic wastes such as livestock and poultry manure and straw has formed a certain foundation, but there are still some obvious limitations in process and performance:

[0006] In the study of existing composting technology, improving process conditions and enhancing fermentation efficiency has always been the main focus. A large amount of work focuses on optimizing C / N ratio, regulating ventilation or adding conventional microbial inoculants to solve the problems of long fermentation period, uneven composting, and large land occupation in traditional composting. However, these technical means, although to some extent, improve the efficiency of composting, generally ignore the targeted cultivation and enrichment of functional active ingredients in compost products. Existing compost products mainly focus on providing basic humus and inorganic nutrients, and there is no effective method to improve the content of physiological active substances such as nicotinic acid and nicotinamide that can directly participate in plant metabolism and enhance stress resistance, limiting the added value of compost products in promoting crop growth and enhancing resistance.

[0007] Secondly, in the resource utilization of tobacco waste, existing technologies focus on the removal of nicotine to reduce its toxic effects on the environment, but fail to effectively utilize nicotine as a precursor to generate high-value nicotinic acid and nicotinamide through biological transformation pathways. This not only causes resource waste, but also limits the function of compost products in promoting crop growth and stress resistance.

[0008] In addition, although high-temperature bacterial agents have been applied in composting, existing bacterial agents are mostly aimed at accelerating the decomposition of organic matter and increasing temperature, and lack efficient conversion capacity for alkaloids such as nicotine. Especially in the multi-waste co-composting system, the tolerance, synergy and functionality of the bacterial agent are still insufficient, and it is difficult to achieve efficient and directional conversion of nicotine to nicotinic substances.

[0009] In summary, the existing composting process still has obvious technical gaps in the enhancement of functional components, synergistic conversion of waste and development of special bacterial agents, and a new composting method and supporting process that can integrate multi-waste and realize directional synthesis of high-value components are urgently needed. SUMMARY

[0010] To solve the technical problems of complex components of multi-organic waste, difficult synergistic conversion and poor adaptability of microbial agents, the present application provides a compost with high content of nicotinic acid and nicotinamide and a preparation method thereof. The present application provides a multi-organic waste synergistic composting method capable of efficiently enriching physiological active substances such as nicotinic acid and nicotinamide.

[0011] The present application aims to provide a composting method for producing high content of nicotinic acid and nicotinamide, comprising the following steps:

[0012] (1) Selecting dry pig manure as compost raw material;

[0013] (2) Crushing corn stalks and tobacco stems into small pieces, as bulking agents, and mixing with the dry pig manure to obtain a pig manure mixture;

[0014] (3) Adding a rapid composting bacterial agent to the mixture, and aerating the reactor to finally prepare a compost with high content of nicotinic acid and nicotinamide.

[0015] In some embodiments of the present application, in step (2), the size of the small pieces of corn stalks and tobacco stems is 1-2 cm.

[0016] In some embodiments of the present application, in step (2), the mass ratio of corn stalks is 20%, and the weight ratio of tobacco stems is 10%.

[0017] In some embodiments of the present application, in step (2), the C / N ratio in the pig manure mixture is (25-28):1.

[0018] In some embodiments of the present application, in step (3), the aeration rate is 0.02-0.36 L / Kg DM / min, and the time is 1-49 days. Further, 0-14 days 0.36 L / Kg DM / min; 14-21 days 0.24 L / Kg DM / min; 21-28 days 0.12 L / Kg DM / min; 28-49 days 0.06 L / Kg DM / min.

[0019] In some embodiments of the present application, the rapid composting bacteria include Geobacillus thermoleovorans and / or Parageobacillus toebii.

[0020] In some embodiments of the present application, the addition amount of the rapid composting bacteria is 1%-3%.

[0021] A second object of the present application is to provide a compost with high content of nicotinic acid and nicotinamide, which is prepared by the composting method.

[0022] In some embodiments of the present application, the content of nicotinic acid in the compost is 0.4-0.8 mg / kg, and the content of nicotinamide is 1.2-1.6 mg / kg.

[0023] The above technical solutions of the present application have the following advantages compared with the prior art:

[0024] The present application promotes the biological conversion of nicotine to nicotinic acid and nicotinamide by co-composting tobacco waste rich in nicotine with livestock and poultry manure, crop straw, etc., and inoculating specific selected high-temperature bacteria. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to make the content of the present application more easily understood, the present application will be further described in detail below according to specific embodiments of the present application and in conjunction with the drawings, wherein,

[0026] Figure 1 is a schematic diagram of the composting reactor of the present application.

[0027] Figure 2 is the effect of the addition of rapid composting bacteria on (A) temperature, (B) oxygen concentration, (C) pH, (D) EC, (E) NH4 + , (F) NO3 - , (G) NH3 daily emission, and (H) NH3 cumulative emission in the composting process of the present application.

[0028] Figure 3 is the GI change in the composting process of the present application.

[0029] Figure 4 is the nicotine content change in the composting process of the present application.

[0030] Figure 5 is the Chao 1 and simpson index change in the composting process of the present application.

[0031] Figure 6 is the dominant bacterial community composition change in the composting process (A) door level (relative abundance > 1%) and (B) genus level (top 20) of the present application (bacteria with door level relative abundance less than 1% are defined as "others").

[0032] Figure 7 is the change in the composting process of the present application (A) beta diversity (application principal coordinate analysis (PCoA) characterization) and (B) physicochemical factor and main genus level bacteria correlation analysis. DETAILED DESCRIPTION

[0033] The present application will be further described below in conjunction with the drawings and specific examples, so that those skilled in the art can better understand the present application and implement it, but the examples are not as a limitation on the present application.

[0034] The composting raw material used in the present application is dry pig manure obtained after solid-liquid separation from the Huai'an Pig Farm of Wen Group. The pig manure is sampled and subjected to composting experiment within 24 hours. The corn straw is obtained from a breeding farm in Shandong Province and has been processed into small pieces of 1-2 centimeters. The tobacco stems produced by tobacco planting in Shizong County are cut into small pieces of 1-2 centimeters and dried as bulking agents.

[0035] The reactor adopts a "sandwich" structure, with a layer of 5 cm thick heat insulation cotton sandwiched between the double-layer stainless steel shell to reduce heat dissipation. The bottom of the reactor is aerated by an automatically controlled air pump, and two aeration outlets are provided on the top cover to release and collect gas. Temperature sensors connected to a computer are provided at the upper, middle and lower parts of the reactor, which automatically record the temperature of the pile every half hour. The experimental device is shown in Figure 1 .

[0036] EXAMPLE

[0037] The present embodiment provides a composting method for producing high content of nicotinic acid and nicotinamide, which is specifically shown as follows:

[0038] I. Preparation method of composting:

[0039] (1) Select dry pig manure after solid-liquid separation in the farm as the raw material of compost, and crush corn straw and tobacco stems produced in Shizong County into small pieces of 1-2 cm as bulking agents to mix with pig manure. The addition ratio of corn straw and tobacco stems is 20% and 10% by weight, respectively, and the C / N ratio of pig manure is adjusted to about 26:1. The composting experiment is carried out in a cylindrical reactor with an effective volume of 70 L. The reactor adopts a "sandwich" structure, with a 5 cm thick layer of heat insulation cotton sandwiched between the double-layer stainless steel shell to reduce heat dissipation. The bottom of the reactor is aerated by an automatically controlled air pump, and two aeration outlets are provided on the top cover to release and collect gas. Temperature sensors connected to a computer are arranged at the upper, middle and lower parts of the reactor, and the temperature of the heap is automatically recorded every half hour. The schematic diagram of the experimental device is shown in Figure 1 The main physicochemical properties of the compost raw material are determined, including pH, EC, moisture content, TC, TN, NH4 + and NO3 - .

[0040] (2) Add rapid composting bacteria to the reactor. The bacteria used are Bacteria A Geobacillus thermoleovorans (accession number CGMCC 1.3474) and Bacteria B Parageobacillus toebii (accession number CGMCC 1.7269), with a concentration of 10 9 cells / ml, and the amount used in composting is 1% of the weight of the bacteria solution based on the weight of the heap. The experiment sets up four treatment groups, named E1, E2, E3 and E4 respectively. Sample collection is carried out at 0, 3, 7, 14, 21, 28, 35 d respectively. The specific aeration rate is 0.36 L / Kg DM / min, and the specific experimental design is shown in Table 1. Each time 500 g of sample is collected from the upper, middle and lower parts of the heap, and divided into two parts. One is stored at -80 ℃ for microbial sequencing. The other is stored at 4 ℃ for physicochemical analysis. The reactor top gas is collected at 10 o'clock every morning using a 0.1 L gas bag. The grouping in the microbial analysis is named F (number of days)_ (group), for example, the first day of composting treatment 1 is named F0_1.

[0041] Table 1 Material mixing and bacteria addition method for multi-organic waste micro-aerobic composting

[0042] Experimental grouping Pig manure Corn straw Tobacco stem Bacterial agent E1 70% 30% 0% — E2 70% 20% 10% — E3 (bacterial agent A) 70% 20% 10% 1% E4 (bacterial agent B) 70% 20% 10% 1%

[0043] II. Sample property detection

[0044] (1) Physicochemical property indexes of samples

[0045] 1) The TC and TN content is determined by elemental analysis.

[0046] 2) 10 g of the sample obtained in step (2) is mixed with 100 mL of deionized water, then shaken for 30 min to obtain a water extract, and the sample pH and EC are determined.

[0047] 3) The sample obtained in step (2) is mixed with a 2 M KCl solution at a ratio of 1:10 (weight / volume) to leach NH4 + and nitrate NO3 - from the sample, and then quantitatively analyzed using a flow analyzer, and the experimental results are shown in Figure 2 .

[0048] 4) The hemicellulose, cellulose and lignin content in the sample is determined by a cellulose rapid determination instrument.

[0049] 5) The phytotoxicity and compost maturity of the finished product are analyzed by the seed germination index (GI).

[0050] (2) The determination of nicotine content in the sample is carried out by liquid chromatography, and the specific method comprises the following steps: about 0.04 g of the freeze-dried sample is weighed into a 50 mL light-resistant colorimetric tube, and 20 mL of 5% methanol is added. Ultrasonic segmentation at 40°C for 3*10 min, with an interval of 5 min each time, and an ultrasonic power of 300 w. Centrifugation at a speed of 8000 r / min for 10 min, then filtered through a 0.22 μm filter membrane, and placed in a brown chromatographic bottle. The determination is carried out by liquid chromatography. The specific method is as follows: first, prepare the nicotine standard curve by dissolving the nicotine standard in methanol to prepare a 1 mg / mL nicotine solution as the nicotine stock solution. Take 0.1, 0.2, 0.4, 0.6, 0.8, and 1.0 mL of the nicotine stock solution, respectively, and dilute the volume to 1 mL, with concentrations of 0.1, 0.2, 0.4, 0.6, 0.8, and 1.0 mg / mL, respectively. The liquid phase selects a reversed-phase C8 chromatographic column as the stationary phase, the aqueous phase is 12.5 mM potassium hexafluorophosphate aqueous solution, the organic phase is acetonitrile, the volume ratio of organic phase to aqueous phase is 5:95, the column temperature is set to 30°C, the flow rate is 1 mL / min, the injection volume is 20 μL, and the determination is carried out at a wavelength of 259 nm. The instrument used is Shimadzu LC-20A. The standard curve of peak area versus nicotine concentration is drawn with nicotine concentration as the abscissa and peak area as the ordinate.

[0051] (3) The detection of nicotinic acid and nicotinamide in the sample is also carried out by liquid chromatography, and the method is basically the same as that of nicotine, with the difference that the aqueous phase is 0.1wt% phosphoric acid solution, and the organic phase is methanol, and the volume ratio of organic phase to aqueous phase is 20:80.

[0052] (4) Pollutant gas analysis method: The gases released from the outlet of the compost reactor are collected daily and analyzed immediately. NH3, H2S and O2 are measured using portable NH3, H2S and O2 analyzers, respectively.

[0053] (5) The specific methods for microbial analysis were as follows: Microbial population characteristics during composting were analyzed using high-throughput sequencing technology. Microbial DNA was extracted from compost samples using the Omega Soil DNA Kit. The DNA concentration was determined using a UV-Vis spectrophotometer and purified. A bacterial 16S rRNA gene library was constructed using primers 515F (5'-GTGCCAGCMGCCGCGG-3') and 907R (5'-CCGTCAATTCMTTTRAGTTT-3'). An archaea 16S rRNA gene library was constructed using primers 524F10extf (5'-TGYCAGCCGCCGCGGTAA-3') and Arch958RmodR (5'-GTGCCAGCMGCCGCGG-3'). The final libraries were sequenced on the Illumina Miseq platform. The sequencing results were analyzed and processed on the Meiji Cloud platform. The experimental results are shown in [link to experimental results]. Figure 6 and Figure 7 .

[0054] Test Results

[0055] 1. Basic physicochemical properties and ammonia emissions

[0056] Depend on Figure 2 It can be seen that under different treatments, the composting temperature generally exhibited the same changes, successively experiencing a heating period, a high-temperature period, a cooling period, and a maturation period. Figure 2 -A). The difference lies in the accelerated heating rate of the tobacco straw. Compared to E1, E2 entered the high-temperature stage a day earlier, while the addition of rapid-composting microorganisms allowed treatment groups E3 and E4 to reach the high-temperature stage within 12 hours. During the high-temperature stage before the first turning, the highest temperature (70 ℃) of treatment groups E3 and E4 with the added rapid-composting microorganisms was significantly higher than that of E2 (65 ℃) and E1 (62 ℃). Furthermore, the temperature of the treatment groups with the added microorganisms rose more quickly after turning. Simultaneously, after the first 20 days of turning, the heating rate of treatment groups E3 and E4 with the added rapid-composting microorganisms was higher than that of E2. This is because the added microorganisms are thermophilic bacteria that secrete specific thermophilic cellulases, which increase the temperature of the compost pile by degrading cellulose and other organic matter. Overall, the addition of tobacco straw and rapid-composting microorganisms significantly altered the composting process, playing a positive role.

[0057] Depend on Figure 2 It can be seen that oxygen and temperature changes are negatively correlated, with oxygen demand being highest during high-temperature periods and gradually decreasing as the compost matures. Figure 2-B). The pH of the treatment group with tobacco stems was significantly higher than that of the treatment group without tobacco stems (8 vs. 7), and higher pH was more suitable for the metabolic activity of microorganisms in the pile Figure 2 -C). The EC of all treatment groups showed a downward trend as a whole Figure 2 -D) At the end of composting, the EC values of all treatments were less than 3 mS / cm, meeting the agricultural safety threshold of organic fertilizer (4 mS / cm). The NH4 + and NO3 - content of all treatment groups showed basically the same change trend Figure 2 -E, F). The difference is that the NO3 - content of the E1 treatment group at the end of composting was significantly higher than that of other treatment groups, the NH4 + content had no obvious difference with other treatment groups, and the EC value was lower than other treatment groups. This may be because the content of other metal ions in tobacco stems is high, such as K + , which increases the EC value. The addition of rapid composting bacteria makes this phenomenon more obvious, which shows that the bacteria promote the decomposition of tobacco stem fiber structure, and more metal ions are released into the pile. The NH3 emission of the inoculated treatment group is higher than that of other treatment groups, and the period of this difference is mainly in the high temperature stage Figure 2 -G, H). During the high temperature stage of composting, a large amount of organic nitrogen is mineralized into NH4 + , and then converted into NH3 under high temperature and alkaline conditions. There are more alkaline substances in tobacco stems, and the content of nicotine accounts for more than 90% of the content of alkaloids. The presence of nicotine increases the pH of the pile, and a large amount of organic nitrogen is mineralized into NH4 + under high temperature and alkaline conditions, and then converted into NH3. Nitrogen is converted into NH3 through a series of biochemical reactions during the degradation of nicotine. The degradation of bacteria to the fiber structure of tobacco stems promotes the release of more nicotine into the pile for microbial metabolic utilization, so the inoculated treatment group has higher NH3 emission. It is worth noting that nicotine will be converted into nicotinic acid and nicotinamide during the degradation process, and nicotinamide is an important component of the molecular structure of intracellular NADH and NADPH. Nicotinic acid and nicotinamide will be released outside the cell when the amount of nicotine degrading bacteria in the cell reaches a certain amount. These released nicotinic acid and nicotinamide will be used by other types of microorganisms to synthesize NADH and NADPH, enhancing metabolic capacity. Therefore, it is necessary to detect the content of nicotinic acid and nicotinamide in the pile.

[0058] By Figure 3It can be seen that during the composting process, the GI values of all treatments showed a gradual upward trend, which may be related to the degradation of plant toxic substances, volatilization and the formation of humus. At the end of composting, the GI values of all treatment groups were more than 70%, reaching the composting maturity standard. The difference is that the GI values of the tobacco stem and bacteria treatment reached more than 100 and 140% respectively at 14 days. This may be due to the addition of tobacco stems and bacteria, which accelerates the degradation of plant toxic substances, promotes the formation of NO3 - and humus, and promotes seed germination.

[0059] From Figure 4 it can be seen from the figure that the addition of tobacco stems increases the initial nicotine content of the pile, and the nicotine content of different treatment groups shows different content changes during the subsequent composting process. Figure 4 The nicotine content of E1 treatment decreased to 0 in the first week, and after 14 days, the nicotine content increased to 20 ppm, which may be due to the presence of certain nicotine pesticide residues in corn straw. Nicotine was degraded in large quantities during the high temperature period. Due to turning, some marginal materials in the pile were re-mixed into the center of the pile, causing the release of nicotine. The nicotine content of the E2 treatment group increased for a week and then gradually decreased. This may be because the fiber structure in the tobacco stem was destroyed during the high temperature period, and nicotine was released into the pile. Although there is a certain amount of nicotine-degrading bacteria in the pile, the adaptability of this group of bacteria to high temperature environment is weak, and the ability to metabolize nicotine is reduced, resulting in the accumulation of nicotine in the pile. With the consumption of easily degradable organic matter, the compost enters the cooling period, and the activity of nicotine-degrading bacteria recovers, and nicotine is degraded. Unlike the E2 treatment group, the nicotine content of the E3 and E4 treatment groups did not accumulate in the first week, and the nicotine degradation rate was also significantly higher than that of the E2 treatment group. Interestingly, the two strains of bacteria added have good cellulose degradation performance, combined with the change of composting temperature, the fiber structure of the E3 and E4 treatment groups should have higher degradation effect in the previous week, and more nicotine will be released into the pile. This indicates that there may be a positive interaction between cellulose-degrading bacteria and nicotine-degrading bacteria, and the metabolic activity of the two types of bacteria is enhanced. Figure 4 It can be seen that the addition of tobacco stems can increase the content of nicotinic acid and nicotinamide in the pile. After adding bacteria, the content of nicotinic acid and nicotinamide increases more than that without adding tobacco stems, which indicates that there is indeed an interaction between cellulose-degrading bacteria and nicotine-degrading bacteria. In summary, nicotine degradation mainly occurs during the high temperature stage, and the ability to degrade nicotine is significantly weakened during the cooling and maturation stages. Therefore, it is necessary to screen high-temperature-resistant nicotine-degrading bacteria and compound them with cellulose-degrading bacteria to prepare efficient and rapid composting bacteria suitable for demonstration sites, and promote the synergistic and efficient conversion of multiple organic waste.

[0060] The application applies high-throughput sequencing technology to determine the change of bacterial community in the composting process, and is used for analyzing the influence of the addition of garden waste on the indigenous microorganisms in the microbial inoculant in the composting. Figure 5 It can be known that the alpha diversity (i.e. (Chao 1), and Simpson index) of the four groups of treatments presents obvious changes in the composting process, indicating that the richness and evenness of the bacterial community gradually change in the composting temperature rising period, the high temperature period and the temperature decreasing period. The richness and evenness of the bacterial community obviously decrease in the high temperature stage of the composting, which may be due to the high temperature of the composting, promoting the succession and reproduction of the bacterial community. However, it is worth noting that the richness and evenness of the bacterial community in the treatment groups of adding tobacco stems and microbial inoculants are obviously improved compared with the treatment 1 group.

[0061] The application analyzes the succession of the bacterial community at the door and genus level in the composting process (such as Figure 6 -A). The bacterial community at the door level is mainly composed of Bacillota, Bacteroidota, Actinomycteota, Pseudomonodota and Chloroflexota, and the total abundance of the above-mentioned five doors is more than 92%. Bacteroidota is a kind of microorganism commonly seen in anaerobic environment. Due to the transportation and storage process, the pig manure is stored in the container, and an anaerobic environment is formed in a short time, resulting in that the Bacteroidota in the original material has a high abundance. After entering the high temperature period, the abundance of Bacteroidota in the four treatment groups obviously decreases. At the same time, it can be seen that Bacillota, Actinomycteota and Pseudomonodota have high abundance in the initial material, and these bacteria play an important role in the composting temperature rising and high temperature stage. Bacillota includes Bacillus and Geobacillus (Bacillus and Geobacillus) Figure 6-B), Bacillota is more suitable for high temperature stage. Both of them can secrete cellulose-degrading enzymes, which makes Bacillota can adapt to a wider temperature range, so it has a higher abundance in all stages of composting. It is worth noting that the addition of tobacco stems in the high temperature stage has a significant enrichment effect on Actinomycteota. Actinomycteota is the actinomycete phylum, which is responsible for the most difficult to degrade plant components such as cellulose, hemicellulose and lignin in corn straw and tobacco stems. Other studies have shown that Actinomycteota has a higher ability to degrade cellulose than Bacillota, and the enrichment of Actinomycteota helps to degrade cellulose in the compost

[13] . Therefore, the addition of tobacco stems accelerates the temperature rise rate and increases the number of days in the high temperature stage. The relative abundance of Pseudomonodota is noteworthy throughout the composting process. After the addition of tobacco stems, there is no significant decrease in the high temperature stage, which is different from other studies. The addition of tobacco stems increases the abundance of Proteobacteria, which has a significant effect on nicotine degradation in the monocytes of Proteobacteria. Combined with the changes in nicotine degradation, the nicotine content indeed decreased significantly in this stage. However, it is worth noting that the abundance of Proteobacteria in treatment 4 increased the most, but the nicotine content was the highest. At the same time, the nicotine content also has a rising trend in the cooling stage and the composting stage of composting. The content of nicotine is determined by the release amount and the degradation amount, which shows that the degradation amount of nicotine is not enough, and more efficient nicotine-degrading bacteria need to be added to the compost. The addition of tobacco stems increases the abundance of Chloroflexota in composting, which has the characteristics of degrading recalcitrant organic matter and surviving in microaerobic environments. The increase in the abundance of this type of bacteria helps to improve the ability of compost to improve soil and the degradation rate of organic matter in soil.

[0062] By Figure 7 It can be seen that the β-diversity of bacterial communities in different treatment groups shows significant differences (P < 0.05) Figure 7 -A) In the same treatment group, different composting stages also show differences. Specifically, the treatment without tobacco stems and the treatment with tobacco stems have obvious differences between groups, which shows that the addition of tobacco stems significantly changes the bacterial community structure in the compost. In contrast, the addition of different bacterial agents in the high temperature stage affects the bacterial community structure in the compost, which shows that the addition of bacterial agents can improve the performance of composting by affecting the bacterial structure. It is worth noting that after entering the cooling stage of composting, the addition of bacterial agents has little effect on the bacterial community, because the added bacterial agents are thermophilic bacterial agents with a growth temperature above 45°C.

[0063] It is of great significance to understand the relationship between the succession of microbial community and physicochemical indexes in composting process for improving the value of compost products and optimizing the composting process. In this study, the correlation between physicochemical factors (pH, NO3 ⁻ , GI, Nicotine, EC and OC) and the main bacterial genera in the aerobic composting process was analyzed by Mantel_test. As shown in Fig. Figure 7 -B, pH and GI had strong correlation with 17 kinds of bacteria (P<0.05), which played an important role in the decomposition of organic matter and nutrient transformation in the composting process. In addition, EC and OC had obvious correlation with Bacillus and Actinomyces, because Bacillus and Actinomyces played a major role in the degradation of cellulose, which helped to release the nutrients in plant cells. It could be seen that NO3⁻ content also had strong correlation with Bacillus and Actinomyces, which indicated that adding appropriate cellulose-degrading bacteria could help to improve the quality of compost. It was worth noting that Nicotine content was also mainly related to the content of Bacillus and Actinomyces, which was different from other studies. The common nicotine-degrading bacteria were Geobacter and Pseudomonas in Proteobacteria, which mainly grew at room temperature. According to the change of nicotine content, the degradation of nicotine in the high temperature and middle stage was higher than that in the maturation stage, which indicated that there were efficient high-temperature nicotine-degrading bacteria in the high temperature stage, which had higher nicotine-degrading ability. Therefore, it was necessary to screen and develop high-temperature nicotine-degrading bacteria. At the same time, some studies showed that nicotine would be converted to nicotinic acid and nicotinamide in the process of nicotine degradation, which could be excreted by nicotine-degrading bacteria. These two substances could be used as growth factors by other microorganisms.

[0064] In conclusion, the addition of 10% tobacco stems (E2) and two different bacterial agents (E3 and E4) based on E2 can significantly improve the temperature rise rate of compost, shorten the temperature rise period by 1 day and 1.5 days, respectively, increase the temperature of the initial high-temperature period of compost by 5-8 DEG C compared with the E1 treatment group, and increase the pH of the compost by about 1 compared with the E1 treatment group, thus creating a more suitable environment for compost microorganisms. The GI of the E2, E3 and E4 treatment groups reached 100%, 140% and 150% compared with the E1 (40%) at 14 days, significantly shortening the composting time. The addition of tobacco stems increases the nicotine content in the compost, and the nicotine content of the E2, E3 and E4 treatment groups is increased to 24.45, 38.52 and 24.23 ppm compared with the E1 (14.82 ppm), but the nicotinic acid and nicotinamide contents are increased compared with the E1. The addition of tobacco stems and bacterial agents improves the physicochemical properties of the compost by enriching bacteria at the genus level of Bacillota, Actinomycteota, Pseudomonodota and Chloroflexota. This study provides theoretical support for the coordinated conversion of multiple organic wastes, targeted screening of bacterial agents, and the preparation of personalized nutrient biofertilizers.

[0065] Obviously, the above embodiments are only examples for clearly illustrating the present application, and are not intended to limit the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments are not required to be exhausted, and the obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for producing a high content of nicotinic acid and nicotinamide in compost, characterized by, The method comprises the following steps: (1) selecting dry pig manure as raw material for composting; (2) crushing corn stalks and tobacco stems into small pieces as bulking agent, and mixing the small pieces with the dry pig manure to obtain a pig manure mixture; (3) adding a rapid composting bacteria agent to the mixture, and aerating the reactor to finally prepare a compost with high content of nicotinic acid and nicotinamide.

2. The method for producing high content of nicotinic acid and nicotinamide in compost according to claim 1, wherein, In step (2), the size of the small pieces of corn stalks and tobacco stems is 1-2 cm.

3. The method of producing high levels of nicotinic acid and niacinamide in compost according to claim 1, wherein, In step (2), the mass ratio of corn stalks is 15-20%, and the weight ratio of tobacco stems is 10-15%.

4. The method of producing high levels of nicotinic acid and niacinamide in compost according to claim 1, wherein, In step (2), the C / N ratio in the pig manure mixture is (25-28):

1.

5. The method of producing high levels of nicotinic acid and niacinamide in compost according to claim 1, wherein, In step (3), the aeration rate is 0.06-0.36 L / Kg DM / min, and the time is 1-49 days.

6. The method of producing high levels of nicotinic acid and niacinamide in compost according to claim 1, wherein, The rapid composting bacteria agent comprises Geobacillus thermoleovorans and / or Parageobacillus toebii.

7. The method of producing high levels of nicotinic acid and niacinamide in compost according to claim 1, wherein, The addition amount of the rapid composting bacteria agent is 1%-3%.

8. A compost having a high content of niacin and nicotinamide, characterized in that, The compost is prepared by the composting method according to any one of claims 1-7.

9. The compost of claim 8, wherein The content of nicotinic acid in the compost is 0.4-0.8 mg / kg.

10. The compost of claim 8, wherein, The content of nicotinamide in the compost is 1.2-1.6 mg / kg.

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