Method for resource utilization of agricultural waste and application thereof

Abstract

The application provides a method and application of agricultural waste resource utilization, and belongs to the technical field of environmental pollution treatment; the extracellular electron respiration capacity of the electroactive microorganism Shewanella oneidensis MR-1 (referred to as MR-1) is utilized; agricultural waste is used as an organic carbon source for anaerobic respiration of the microorganism; dye wastewater is efficiently degraded; and thus the agricultural waste is used for resource utilization; the method uses the agricultural waste as the only carbon source, does not need to add other carbon sources, and one-time addition of the agricultural waste is not needed, so that the treatment cost is greatly reduced, and the operation is simple and easy to implement; the method has important practical significance for promoting resource utilization of the agricultural waste and treatment of the dye wastewater.

Description

Technical Field

[0001] This invention belongs to the field of environmental pollution control technology, specifically relating to a method and application for the resource utilization of agricultural waste. Background Technology

[0002] Agricultural waste, including crop straw and livestock manure, is rich in organic carbon. However, the conversion rate of agricultural waste into resources remains low, leading not only to resource waste but also exacerbating environmental pollution. Currently, the large-scale accumulation of agricultural waste has caused serious environmental problems, threatening not only the sustainable development of agriculture but also posing potential harm to human health. Therefore, how to effectively treat agricultural waste in an environmentally friendly manner and achieve its resource utilization has become a major issue that urgently needs to be addressed.

[0003] Currently, the utilization of agricultural waste is mainly concentrated in fertilizer manufacturing and energy production, while its potential application value in wastewater treatment has not been fully explored, especially as a potential carbon source for the biodegradation of dye wastewater. Dye wastewater is a common type of industrial wastewater, containing large amounts of organic dyes and other harmful substances, most of which have carcinogenic, teratogenic, and mutagenic effects. Direct discharge of this wastewater poses a serious threat to the environment and human health. Currently, methods for decolorizing and degrading dye wastewater include physical, chemical, and biological methods. Among these, biological methods are considered the most promising for dye wastewater treatment due to their environmental friendliness and lower cost, especially the biological method utilizing electroactive microorganisms to degrade dyes, which is highly favored due to its non-specific degradation characteristics. When electroactive microorganisms undergo anaerobic respiration, they release electrons, which attack pollutants, causing their degradation and thus providing new possibilities for the efficient, economical, and environmentally friendly treatment of dye wastewater. However, electroactive microorganisms typically rely on small-molecule organic carbon sources such as lactic acid and pyruvic acid during anaerobic respiration. These carbon sources are relatively expensive, which to some extent limits their industrial application in the field of environmental pollution bioremediation. Expanding the range of carbon sources for electroactive microorganisms will greatly promote their practical application in the bioremediation of organic pollutants.

[0004] Therefore, it is necessary to develop a new method for the resource utilization of agricultural waste, which can effectively treat agricultural waste, reduce the cost of dye wastewater treatment, and achieve the goal of treating waste with waste and recycling resources. Summary of the Invention

[0005] To address some shortcomings in existing technologies, this invention provides a method and application for the resource utilization of agricultural waste. This invention utilizes the extracellular electronic respiration capacity of the electroactive microorganism *Shewanella oneidensis* MR-1 (MR-1 for short) to use agricultural waste as an organic carbon source for its anaerobic respiration, thereby efficiently degrading dye wastewater and achieving the resource utilization of agricultural waste. The method of this invention uses agricultural waste as the sole carbon source, eliminating the need for additional carbon sources, and the one-time addition of agricultural waste significantly reduces treatment costs and is simple and easy to implement. This method has significant practical implications for promoting the resource utilization of agricultural waste and the treatment of dye wastewater.

[0006] To achieve the above objectives, the present invention employs the following technical means:

[0007] This invention first provides a method for the resource utilization of agricultural waste, the method comprising:

[0008] (1) The agricultural waste is cleaned, dried, crushed and screened to obtain uniform and fine agricultural waste powder, which is then sterilized to obtain sterilized agricultural waste powder for later use.

[0009] (2) Activate the electroactive microorganisms and culture them to the late logarithmic growth phase. Collect the bacterial cells by centrifugation and resuspend them to obtain bacterial solution for later use.

[0010] (3) The sterilized agricultural waste powder and bacterial solution were added to the dye wastewater to form a uniform mixture. Then the pH value of the mixture was adjusted and nitrogen was introduced to remove oxygen, forming a dye degradation system under anaerobic conditions.

[0011] (4) The dye degradation system is carried out at a constant temperature to realize the resource utilization of agricultural waste.

[0012] Preferably, in step (1), the agricultural waste includes one or more of peanut shells, wheat straw, rice straw, and corn cobs;

[0013] The particle size of agricultural waste powder after screening should not exceed 100 mesh.

[0014] Preferably, in step (1), the sterilization method includes high-pressure steam sterilization, i.e., sterilization at 103.4 kPa and 121.3 °C for 30 min.

[0015] Preferably, in step (2), the electroactive microorganisms include one or more of Shewanella oneidensis MR-1, Shewanella putrefactions, Geobacter sulfurreducens, and Rhodofoferax ferrireducens; preferably Shewanella oneidensis MR-1.

[0016] Preferably, Shewanella oneidensis MR-1 is activated and inoculated into liquid LB medium, and cultured with shaking at 30°C and 200 rpm until the late logarithmic growth stage.

[0017] Preferably, in step (2), the concentration of the bacterial solution is 4–6 × 10⁻⁶. 7 CFU / mL.

[0018] Preferably, in step (3), the mass concentration ratio of sterilized agricultural waste powder to dye wastewater in the mixture is 1 to 10:1; the volume percentage of bacterial solution is 6% to 12%.

[0019] The dye pollutants in the dye wastewater include one or more of the following: nitroso dyes, anthraquinone dyes, quinone imine dyes, phenazine dyes, and azo dyes of different polarities.

[0020] Preferably, in step (3), the pH value of the mixture is adjusted to 6.5 to 7.5.

[0021] Preferably, in step (4), the degradation reaction is carried out at 25–35°C and 195–205 rpm.

[0022] The present invention also provides a system for the resource utilization of agricultural waste, the system comprising agricultural waste powder, bacterial liquid of electroactive microorganisms and dye wastewater.

[0023] The present invention also provides the application of the above system in the treatment of agricultural waste and / or the degradation of dyes; the dyes include one or more of nitroso dyes, anthraquinone dyes, quinone imine dyes, phenazine dyes and azo dyes of different polarities.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) The method described in this invention utilizes agricultural waste as a carbon source for microbial biodegradation of dyes, enabling microorganisms to directly absorb the organic matter to support their growth and metabolic activities. Compared to physical treatment methods that use agricultural waste as an adsorbent to treat dye wastewater, this invention eliminates the need for complex adsorbent preparation and modification, and avoids the need to treat agricultural waste that has adsorbed dye pollutants (improper treatment may lead to secondary pollution). Furthermore, current agricultural waste adsorbents have low adsorption capacity, poor adsorption performance stability, and poor treatment effect, making them unsuitable for treating different dye wastewaters. In contrast, this invention not only has a simple process, significantly saving time and economic costs, but also exhibits good degradation effect on dye wastewater, can degrade different dye wastewaters, has a wide range of applications, and causes no secondary pollution, demonstrating higher practicality and economy.

[0026] (2) The method of this invention uses agricultural waste as the sole carbon source, requiring no additional carbon source materials. Furthermore, agricultural waste is added directly and in one step during the dye degradation process, eliminating the need for pre-fermentation treatment. This makes the process simple and quick. Compared to traditional methods that require fermentation of agricultural waste followed by the use of the fermentation liquid as a carbon source for microbial degradation of pollutants, this invention offers a simpler process, eliminating the need for sealed fermentation equipment and operations. It is convenient to operate and manage, and reduces investment costs. Simultaneously, it allows for direct initiation of the degradation process, significantly shortening the overall treatment time and greatly improving treatment efficiency. This results in more efficient resource utilization of agricultural waste and dye degradation.

[0027] (3) The method described in this invention operates under mild reaction conditions and requires no additional chemical reagents, thereby greatly reducing the risk of secondary pollution and meeting the requirements of environmental protection and sustainable development. The method described in this invention should be able to effectively treat various types of agricultural waste and various dye wastewaters, avoiding environmental pollution and resource waste, while reducing the cost of dye wastewater treatment and achieving the goal of treating waste with waste and recycling resources. This not only helps to promote the reduction, resource recovery, and harmless treatment of agricultural waste, but also has significant implications for promoting environmental protection and sustainable development. Attached Figure Description

[0028] Figure 1 This is a diagram illustrating the mechanism by which MR-1 utilizes agricultural waste to degrade dye wastewater.

[0029] Figure 2 This is a diagram showing the degradation effect of MR-1 on yellow soap using different agricultural wastes.

[0030] Figure 3 This is a graph showing the degradation effect of MR-1 on Reactive Brilliant Blue KN-R using different agricultural wastes.

[0031] Figure 4This is a graph showing the degradation effect of MR-1 on naphthol green B using different agricultural wastes. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto. Unless otherwise expressly defined, all technical terms used herein follow the common understanding of those skilled in the art. The use of these terms is intended only to describe specific embodiments and not to limit the scope of protection of the present invention. Unless otherwise specifically indicated, all raw materials, reagents, instruments, and equipment involved in the present invention can be obtained commercially or prepared by existing methods.

[0033] The formulations of the solid LB agar plate, liquid LB agar plate, and mineral salt solution used in the following examples are as follows:

[0034] Solid plate LB medium: 5 g / L yeast extract, 10 g / L tryptone, 10 g / L sodium chloride, 2% agar, deionized.

[0035] Liquid LB medium: 5 g / L yeast extract, 10 g / L tryptone, 10 g / L sodium chloride, prepared by deionization.

[0036] Mineral salt solution: 50 mM biological buffer, 7.5 mM sodium hydroxide, 28.0 mM ammonium chloride, 1.3 mM potassium chloride, 100.0 mM sodium chloride, 4.3 mM sodium dihydrogen phosphate dihydrate, 1.0 mL / L vitamin stock solution, 1.0 mL / L amino acid stock solution, and 1.0 mL / L trace element stock solution. Each liter of vitamin stock solution contains: 2.0 mg biotin, 2.0 mg folic acid, 10.0 mg pyridoxine hydrochloride, 5.0 mg riboflavin, 5.0 mg vitamin B1, 5.0 mg niacin, 5.0 mg vitamin B5, and 0.1 mg vitamin B2. 12Each liter of vitamin stock solution contains: 5.0 mg p-aminobenzoic acid and 5.0 mg lipoic acid; 2.0 g L-glutamic acid, 2.0 g L-arginine and 2.0 g DL-serine; each liter of trace element stock solution contains: 15.0 mg C6H9NO3, 30.0 mg MgSO4·7H2O, 5.0 mg MnSO4·H2O, 10.0 mg NaCl, 1.0 mg FeSO4·7H2O, 1.0 mg CaCl2·2H2O, 0.999 mg CoCl2·6H2O, 1.3 mg ZnCl2, 0.0999 mg CuSO4·5H2O, 0.0996 mg AlK(SO4)2·12H2O, 0.1002 mg H3BO3, 0.2495 mg Na2MoO4·2H2O, 0.2401 mg NiCl2·6H2O and 0.2507 mg Na2WO4·2H2O.

[0037] The electroactive microorganism used in the following examples is *Shewanella oneidensis* MR-1. This electroactive microorganism can also be replaced by one or more of *Shewanella putrefactions*, *Geobacter sulfurreducens*, and *Rhodofoferax ferrireducens*. *Shewanella oneidensis* MR-1 is a model electroactive microorganism, donated by Professor Nelson of the University of California, and is deposited at the American Type Culture Collection (ATCC) under strain number ATCC700500. TM .

[0038] The preparation steps of the bacterial suspension of Shewanella oneidensis MR-1 (hereinafter referred to as MR-1) involved in the following examples are as follows:

[0039] (1) Take the MR-1 bacteria frozen in glycerol from the -80℃ freezer. After thawing, use a pipette to accurately transfer an appropriate amount of bacterial culture into a test tube containing liquid LB medium. Then place the test tube in a constant temperature shaking incubator at 30℃ and 200rpm and incubate overnight to ensure that the strain is fully recovered and proliferated.

[0040] (2) Remove the test tubes that have been incubated overnight from the constant temperature shaking incubator, use an inoculation loop to take an appropriate amount of bacterial solution, and streak it onto a solid LB agar plate. After streaking, place the plate in a 30°C constant temperature incubator and incubate it again overnight to obtain single colonies.

[0041] (3) Use a pipette to accurately pick up a single colony of MR-1 from a solid LB agar plate and inoculate it into 50 mL of liquid LB agar. Then, place the inoculated culture medium in a constant temperature shaking incubator at 30℃ and 200 rpm and shake for 12 h until the bacterial culture enters the late logarithmic growth stage.

[0042] (4) During the late logarithmic growth phase, transfer 50 mL of bacterial culture to a sterile centrifuge tube and centrifuge at 8000 rpm for 5 min. After centrifugation, remove the supernatant and collect the bacterial pellet. Then, resuspend the bacterial cells using a mineral salt solution. Repeat this centrifugation and resuspension process twice. Finally, adjust the concentration of the bacterial resuspension to 4–6 × 10⁻⁶ using spectrophotometry. 7 CFU / mL, for later use.

[0043] Example 1:

[0044] In this embodiment, the dye wastewater used was commercially available, containing the weakly polar azo dye, Soap Yellow. The agricultural waste used was self-collected peanut shells, wheat straw, rice straw, and corn cobs. This was to investigate the degradation effect of MR-1 on Soap Yellow using different agricultural wastes. The mechanism by which MR-1 degrades dye wastewater using agricultural waste is as follows: Figure 1 As shown, the implementation steps are as follows:

[0045] (1) The collected agricultural waste peanut shells, wheat straw, rice straw and corn cob were thoroughly washed with deionized water, then dried in an oven at 105°C, then chopped and further crushed by a pulverizer, and finally sieved through a 100-mesh sieve to obtain uniform and fine peanut shell powder, wheat straw powder, rice straw powder and corn cob powder.

[0046] Weigh out 0.005g each of peanut shell powder, wheat straw powder, rice straw powder, or corn cob powder and place them in an autoclave. Sterilize them at 103.4kPa and 121.3℃ for 30 minutes to eliminate potential microbial contamination. The resulting sterilized peanut shell powder, wheat straw powder, rice straw powder, or corn cob powder is sterilized agricultural waste powder and is ready for use.

[0047] (2) Weigh 0.005g of the weakly polar azo dye Soap Yellow and dissolve it in 50mL of mineral salt solution to prepare as simulated Soap Yellow dye wastewater for later use.

[0048] (3) Add 3 mL of MR-1 bacterial solution and 0.005 g of sterilized peanut shell powder, wheat straw powder, rice straw powder or corn cob powder to 50 mL of yellow dye wastewater to form a uniform mixture. Then adjust the pH of the mixture to 6.5-7.5 and then introduce nitrogen gas into it for 15 min to drive away the oxygen and form a dye degradation system under anaerobic conditions.

[0049] (4) Place the dye degradation system in a constant temperature shaking box and react at 30℃ and 200rpm. Take samples at regular intervals. After centrifuging the samples, measure the absorbance of the supernatant with a UV-Vis spectrophotometer. Calculate the dye degradation rate according to the measured absorbance value using the following formula.

[0050]

[0051] In the formula, A0 is the initial absorbance of the dye solution; A t The absorbance of the dye solution at time t is given.

[0052] Figure 2 This graph shows the degradation effect of MR-1 bacteria on yellow dye wastewater using different agricultural wastes. As can be seen, MR-1 bacteria can achieve a 99% degradation rate in 24 hours using any one of corn cobs, peanut shells, wheat straw, and rice straw as a carbon source. This indicates that all four agricultural wastes can serve as effective carbon sources for MR-1 in degrading dye wastewater, although the utilization rates differ slightly, with corn cobs showing the fastest utilization rate. This process simultaneously achieves the resource utilization and efficient degradation of agricultural waste.

[0053] Example 2:

[0054] In this embodiment, the dye wastewater used was that of the anthraquinone dye Reactive Brilliant Blue KN-R (commercially available). The agricultural waste consisted of peanut shells, wheat straw, rice straw, and corn cobs collected from farmland. This was to investigate the degradation effect of MR-1 on methylene blue using different agricultural wastes. The implementation steps are as follows:

[0055] (1) The collected agricultural waste peanut shells, wheat straw, rice straw and corn cob were thoroughly washed with deionized water, then dried in an oven at 105°C, then chopped and further crushed by a pulverizer, and finally sieved through a 100-mesh sieve to obtain uniform and fine peanut shell powder, wheat straw powder, rice straw powder and corn cob powder.

[0056] Weigh out 0.005g each of peanut shell powder, wheat straw powder, rice straw powder, or corn cob powder and place them in an autoclave. Sterilize them at 103.4kPa and 121.3℃ for 30 minutes to eliminate potential microbial contamination. The resulting sterilized peanut shell powder, wheat straw powder, rice straw powder, or corn cob powder is sterilized agricultural waste powder and is ready for use.

[0057] (2) Weigh 0.005g of anthraquinone dye Reactive Brilliant Blue KN-R and dissolve it in 50mL of mineral salt solution to prepare as simulated Reactive Brilliant Blue KN-R dye wastewater for later use.

[0058] (3) Add 3 mL of MR-1 bacterial solution and 0.005 g of sterilized peanut shell powder, wheat straw powder, rice straw powder or corn cob powder to 50 mL of reactive brilliant blue KN-R dye wastewater to form a uniform mixture. Then adjust the pH of the mixture to 6.5-7.5 and then introduce nitrogen gas into it for 15 min to drive away the oxygen and form a dye degradation system under anaerobic conditions.

[0059] (4) Place the dye degradation system in a constant temperature shaking box and react for 1 to 3 days at 30°C and 200 rpm. Take samples regularly. After centrifuging the samples, measure the absorbance of the supernatant with a UV-Vis spectrophotometer. Calculate the dye degradation rate according to the measured absorbance value using the following formula.

[0060]

[0061] In the formula, A0 is the initial absorbance of the dye solution; A t The absorbance of the dye solution at time t is given.

[0062] Figure 3 These are graphs showing the degradation effect of MR-1 on methylene blue using different agricultural wastes. Figure 3 It can be seen that after 48 hours of reaction, corn cobs, peanut shells, wheat straw, and rice straw can all serve as carbon sources for MR-1 and be effectively utilized, achieving efficient degradation of methylene blue dye wastewater with a degradation rate of up to 85%. This process realizes the resource utilization of agricultural waste.

[0063] Example 3:

[0064] In this embodiment, the dye wastewater used was that of the commercially available metal-coated composite dye naphthol green B. The agricultural waste used was peanut shells, wheat straw, rice straw, and corn cobs collected from farmland. This was to investigate the degradation effect of MR-1 on naphthol green B using different agricultural wastes. The implementation steps are as follows:

[0065] (1) The collected agricultural waste peanut shells, wheat straw, rice straw and corn cob were thoroughly washed with deionized water, then dried in an oven at 105°C, then chopped and further crushed by a pulverizer, and finally sieved through a 100-mesh sieve to obtain uniform and fine peanut shell powder, wheat straw powder, rice straw powder and corn cob powder.

[0066] Weigh out 0.005g each of peanut shell powder, wheat straw powder, rice straw powder, or corn cob powder and place them in an autoclave. Sterilize them at 103.4kPa and 121.3℃ for 30 minutes to eliminate potential microbial contamination. The resulting sterilized peanut shell powder, wheat straw powder, rice straw powder, or corn cob powder is sterilized agricultural waste powder and is ready for use.

[0067] (2) Weigh 0.005g of the metal composite dye naphthol green B and dissolve it in 50mL of mineral salt solution to prepare as simulated naphthol green B wastewater for later use.

[0068] (3) Add 3 mL of MR-1 bacterial solution, 0.005 g of sterilized peanut shell powder, wheat straw powder, rice straw powder or corn cob powder to 50 mL of naphthol green B dye wastewater to form a uniform mixture. Then adjust the pH of the mixture to 6.5-7.5 and then introduce nitrogen gas into it for 15 min to drive away the oxygen and form a dye degradation system under anaerobic conditions.

[0069] (4) Place the dye degradation system in a constant temperature shaking box and react for 1 to 3 days at 30°C and 200 rpm. Take samples regularly. After centrifuging the samples, measure the absorbance of the supernatant with a UV-Vis spectrophotometer. Calculate the dye degradation rate according to the measured absorbance value using the following formula.

[0070]

[0071] In the formula, A0 is the initial absorbance of the dye solution; A t The absorbance of the dye solution at time t is given.

[0072] Figure 4 This graph shows the degradation effect of MR-1 on naphthol green B using different agricultural wastes. As can be seen from the graph, after 30 hours of reaction, corn cobs, peanut shells, wheat straw, and rice straw can all serve as carbon sources for MR-1 and be effectively utilized, thus achieving highly efficient degradation of naphthol green B dye wastewater with a degradation rate as high as 98%. This process realizes the resource utilization of agricultural waste.

[0073] In summary, this invention directly uses different types of agricultural waste as carbon sources for MR-1, successfully achieving efficient and low-cost degradation of dye pollutants. The method described in this invention exhibits good applicability to various types of dyes, with a dye degradation rate reaching up to 99%. The system described in this invention is a highly efficient and low-consumption dye degradation system that can operate stably in a neutral environment without the need for additional chemical reagents, thereby reducing operating costs. The agricultural waste resource utilization and / or dye degradation system described in this invention has excellent performance and practicality, demonstrating broad application prospects.

[0074] The embodiments described above are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for the resource utilization of agricultural waste, characterized in that, The method includes: (1) The agricultural waste is washed, dried, crushed and screened to obtain uniform and fine agricultural waste powder, and then sterilized to obtain sterilized agricultural waste powder for later use; the agricultural waste includes one or more of peanut shells, wheat straw, rice straw and corn cobs. The particle size of agricultural waste powder after screening should not exceed 100 mesh; (2) The electroactive microorganisms were activated and cultured to the late logarithmic growth phase. The cells were collected by centrifugation and resuspended to obtain a bacterial solution for later use. The electroactive microorganisms included Shewanella oneneidae. Shewanella oneidensis MR-1, Shewanella putrefaction Shewanella putrefaciens、 sulfur-reducing bacteria Geobacter sulfurreducens Iron-reducing red bacteria Rhodofoferax ferrireducens One or more of the following; The concentration of the bacterial solution is 4~6×10⁻⁶. 7 CFU / mL; (3) The sterilized agricultural waste powder and bacterial solution were added to the dye wastewater to form a uniform mixture. Then the pH value of the mixture was adjusted and nitrogen was introduced to remove oxygen, forming a dye degradation system under anaerobic conditions. In the mixed solution, the mass concentration ratio of sterilized agricultural waste powder to dye wastewater is 1~10:1; the volume percentage of bacterial solution is 6%~12%; the dye pollutants in the dye wastewater include one or more of nitroso dyes, anthraquinone dyes, quinone imine dyes, phenazine dyes and azo dyes of different polarities. The pH of the mixture is adjusted to 6.5-7.5; (4) The dye degradation system is carried out at a constant temperature to realize the resource utilization of agricultural waste; The degradation reaction was carried out at 25-35°C and 195-205 rpm.

2. The method for resource utilization of agricultural waste according to claim 1, characterized in that, The electroactive microorganism is *Schizium anisopliae*. Shewanella oneidensis MR-1; Oneda Shiva Shewanella oneidensis After activation, MR-1 was inoculated into liquid LB medium and cultured with shaking at 30°C and 200 rpm until the late logarithmic growth stage.

3. A system for realizing the resource utilization of agricultural waste according to any one of claims 1 to 2, characterized in that, The system comprises agricultural waste powder, bacterial liquid of electroactive microorganisms, and dye wastewater.

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