Biological agent for reducing heavy metals in feed and preparation method thereof

Abstract

The invention relates to the technical field of feed additives, and particularly discloses a biological agent for reducing heavy metals in feed and a preparation method. The biological agent is prepared from the following raw materials in parts by weight: 100 to 150 parts of bacillus subtilis, 25 to 50 parts of saccharomycetes, 25 to 50 parts of lactic acid bacteria compound bacteria, 200 to 300 parts of ZnO-BT / BC composite material and 50 to 80 parts of humic acid, wherein the ZnO-BT / BC composite material is a composite material formed by loading nano zinc oxide and bentonite on biochar. And uniformly mixing bacillus subtilis, saccharomycetes, lactic acid bacteria compound bacteria, the ZnO-BT / BC composite material and humic acid to obtain the biological agent for reducing the heavy metals in the feed.

Description

Technical Field

[0001] The present invention relates to the technical field of feed additives, and in particular to a biological bacterial agent for reducing heavy metals in feed and a preparation method thereof. Background Art

[0002] With the rapid development of industrialization and urbanization, environmental pollution is becoming increasingly serious, especially heavy metal pollution. Heavy metals can accumulate in organisms through the food chain, ultimately endangering human health. As an important input for livestock and poultry farming, the safety of feed is directly related to the quality and safety of livestock and poultry products.

[0003] Traditional methods for detoxifying heavy metals in feed mainly include physical adsorption, chemical precipitation and chelating agent methods. In recent years, methods for removing heavy metals using microorganisms have also emerged. Microorganisms can remove heavy metals through various pathways such as adsorption, precipitation, oxidation-reduction and methylation, with the advantages of low cost, high efficiency and environmental friendliness. Therefore, methods for removing heavy metals using microorganisms have gradually attracted attention.

[0004] In the related technology, patent CN104109053A discloses a microbial fertilizer for reducing pesticide and heavy metal residues and its preparation method. The raw material ratio of the fertilizer is: 50 kg of carboxymethyl starch, 80 kg of rice yellow bacterium fermentation broth, 100 kg of Aspergillus glaucoides fermentation broth, 100 kg of Bacillus subtilis fermentation broth, 3 kg of chitin, 2 kg of nucleotides, 20 kg of potassium nitrate, 20 kg of dipotassium hydrogen phosphate, 50 kg of potassium humate, and 1500 kg of water.

[0005] However, the above-mentioned microbial fertilizers only degrade heavy metals through the metabolism of a few strains, and the removal effect of heavy metals is limited, which is difficult to meet actual needs. Summary of the invention

[0006] In order to improve the removal effect of heavy metals in feed, the present application provides a biological agent for reducing heavy metals in feed and a preparation method.

[0007] In the first aspect, the present application provides a biological agent for reducing heavy metals in feed, which adopts the following technical solution:

[0008] A biological microbial agent for reducing heavy metals in feed comprises the following raw materials in parts by weight: 100-150 parts of Bacillus subtilis, 25-50 parts of yeast, 25-50 parts of lactic acid bacteria composite bacteria, 200-300 parts of ZnO-BT / BC composite material, and 50-80 parts of humic acid. The ZnO-BT / BC composite material is a composite material formed by co-loading nano zinc oxide and bentonite on biochar.

[0009] By adopting the above technical scheme, Bacillus subtilis secretes extracellular polysaccharide (EPS) to encapsulate Cu 2+ 、Cd 2+ Bacillus subtilis metabolizes to produce organic acids such as citric acid and oxalic acid, which dissolve insoluble heavy metal salts (such as lead phosphate and cadmium carbonate) in feed, promote their release and adsorption onto ZnO-BT / BC. Yeast can reduce heavy metals through reductase and combine with humic acid to form precipitation. Lactic acid bacteria degrade feed fiber, release active functional groups such as carboxyl, and enhance the chelation of humic acid and heavy metals. Humic acid maintains the weak acidity of the feed digestion environment and enhances the metabolic efficiency of Bacillus subtilis, yeast and lactic acid bacteria.

[0010] In the ZnO-BT / BC composite material, biochar is a porous material with a specific surface area of ​​300-800m 2 / g, with a high loading amount of bentonite and nano zinc oxide, thus forming a composite material in which nano zinc oxide and bentonite are co-loaded on biochar; after loading, biochar can also prevent bentonite from structural dissociation in an acidic environment and improve the stability of nano zinc oxide. Therefore, the biochar in the ZnO-BT / BC composite material adsorbs heavy metal ions through interlayer pores, and the hydroxyl and carboxyl groups on the surface of bentonite form stable coordination bonds with heavy metals. The surface active sites of nano zinc oxide can form chemical adsorption with heavy metals through coordination bonds. Moreover, biochar can limit the rapid release of bentonite and nano zinc oxide, avoiding premature inactivation of the ZnO-BT / BC composite material. Therefore, a trinity functional system of "adsorption-passivation-slow release" is formed, taking into account both high efficiency and safety. The bentonite in the ZnO-BT / BC composite material can also form a "humic acid-metal-bentonite" ternary complex with heavy metals to reduce the free concentration of heavy metals.

[0011] Therefore, the biological agent for reducing heavy metals in feed of the present application helps to improve the removal effect of heavy metals in feed.

[0012] In a specific embodiment, the preparation method of the ZnO-BT / BC composite material comprises the following steps:

[0013] Dissolve Zn(NO3)2·6H2O in water to obtain a Zn(NO3)2 solution with a concentration of 0.01-0.1 mol / L, dissolve NaOH in water to obtain a NaOH solution with a pH of 10-12, and disperse bentonite in water to obtain a bentonite suspension with a concentration of 0.1-0.5 g / mL;

[0014] Add the biochar to the Zn(NO3)2 solution and stir evenly to obtain a suspension;

[0015] Add NaOH solution to the suspension to adjust the pH to 9.0-10.0, stop adding NaOH solution, then add bentonite suspension, stir evenly to obtain a reaction solution;

[0016] The reaction solution was centrifuged to separate the solid from the supernatant, and the solid was washed with deionized water and dried to obtain a ZnO-BT / BC composite material.

[0017] By adopting the above technical solution, zinc nitrate (Zn(NO3)2·6H2O) is used as a zinc precursor, which is low in price and easily soluble in water. By adjusting the pH of the suspension to alkaline (pH9-10), nano zinc oxide can be directly precipitated. The porous structure of biochar provides loading sites for nano zinc oxide. Nano zinc oxide is evenly loaded in the form of crystals, and the chemical bonding is more stable. Bentonite dissociates between layers under alkaline conditions to form nano channels. After bentonite is combined with biochar, the specific surface area of ​​the composite material can be increased.

[0018] In a specific feasible implementation method, the biochar is pre-treated as follows: HNO3 and water are mixed in a volume ratio of 1:(10-15) to obtain a nitric acid solution, the biochar is added to the nitric acid solution, heated in a water bath at 40-60°C, stirred for 1-4 hours, 1 mol / L NaOH solution is added to adjust the pH to 6-7, stirring is stopped, centrifugation is performed to separate the solid and the supernatant, the solid is washed, and then dried to complete the pretreatment of the biochar.

[0019] By adopting the above technical solution, nitric acid reacts with biochar under the above water bath heating conditions to generate oxygen-containing functional groups such as carboxyl and phenolic hydroxyl groups, significantly improving the surface polarity of biochar and increasing the porosity of biochar, providing more loading sites for nano zinc oxide and reducing agglomeration. Acidic treatment dissolves some heavy metal impurities in biochar and can also avoid secondary pollution in subsequent composite materials.

[0020] In a specific embodiment, the bentonite is sodium bentonite with a particle size of 200-300 meshes.

[0021] By adopting the above technical solution, the 200-300 mesh sodium bentonite has a larger specific surface area, which helps to improve the adsorption capacity of the composite material. In addition, the interlayer spacing of the sodium bentonite interlayer structure is about 1.2-1.5nm, which can accommodate the insertion of nano ZnO to form a BT-ZnO heterogeneous structure, thereby enhancing the selective adsorption of heavy metal ions.

[0022] In a specific embodiment, the biological agent for reducing heavy metals in feed further comprises the following raw materials in parts by weight: 50-100 parts of diatomaceous earth.

[0023] By adopting the above technical solution, diatomaceous earth has a nanoscale pore structure and can form a heterogeneous complex with ZnO-BT / BC, capture heavy metal colloidal particles through electrostatic adsorption, and achieve the effect of synergistic adsorption of insoluble heavy metal salts.

[0024] In a specific embodiment, the biological agent for reducing heavy metals in feed further comprises the following raw materials in parts by weight: 10-20 parts of vitamin C.

[0025] By adopting the above technical solution, vitamin C can remove the active oxygen generated during the storage of the biological agent, which helps to protect the protein and nucleic acid of the bacteria in the biological agent from oxidative degradation, thereby maintaining the activity of the biological agent.

[0026] In a specific embodiment, the biological agent for reducing heavy metals in feed further comprises the following raw materials in parts by weight: 80-120 parts of skim milk powder, 30-50 parts of maltodextrin and 10-30 parts of glycerol.

[0027] By adopting the above technical solution, skim milk powder is used as a slow-release carbon source to slowly release energy during storage, maintain the metabolic activity of the bacteria, and protect the membrane structure of the bacteria. Maltodextrin forms a gel to form a gel structure, which can embed and fix the bacteria, reduce mechanical damage, and also has an antioxidant effect, delaying the denaturation of bacterial proteins. Glycerol, as an osmotic regulator, can stabilize the lipid bilayer of the cell membrane and prevent the cell membrane from rupturing during the drying process.

[0028] In the second aspect, the present application provides a method for preparing a biological agent for reducing heavy metals in feed, which adopts the following technical scheme:

[0029] A method for preparing a biological agent for reducing heavy metals in feed is as follows: Bacillus subtilis, yeast, lactic acid bacteria composite bacteria, ZnO-BT / BC composite material, and humic acid are uniformly mixed to obtain a biological agent for reducing heavy metals in feed.

[0030] In summary, this application has the following beneficial effects:

[0031] 1. This application improves the removal effect of heavy metals in feed through the synergistic combination of bacteria, ZnO-BT / BC composite materials and humic acid, which helps to reduce heavy metals in feed.

[0032] 2. Diatomaceous earth is preferably used in the present application, which can capture heavy metal colloidal particles through electrostatic adsorption, thereby achieving the effect of synergistic adsorption of insoluble heavy metal salts.

[0033] 3. Vitamin C is preferably used in the present application, which helps to protect the proteins and nucleic acids of the bacteria in the biological agent from oxidative degradation, thereby maintaining the activity of the biological agent. DETAILED DESCRIPTION

[0034] Unless otherwise specified, the raw materials used in this application are all commercially available. Among them, the viable count of Bacillus subtilis is 1.24×10 11 cfu / g, the number of live yeast cells is 1.24×10 11 cfu / g, the lactic acid bacteria compound is Muque brand 4-bacteria compound probiotics, with a live bacteria count of 100 billion cfu / g.

[0035] Humic acid was Yishunfa brand free acid humic acid. Biochar was 180-200 mesh plant straw charcoal. Bentonite was purchased from Weifang Haoyuan Bentonite Factory.

[0036] The basic composition of skimmed milk powder is as follows: lactose 54.5%, protein 32.9%, minerals 7.9%, water 3.8%, and fat 0.9%.

[0037] Maltodextrin was purchased from Shandong Xinxiong Biology, CAS No. 9050-36-6.

[0038] The present application is further described in detail below with reference to examples and comparative examples.

[0039] Example

[0040] Example 1

[0041] The present embodiment provides a biological agent for reducing heavy metals in feed, comprising the following raw materials: 125 g of Bacillus subtilis, 35 g of yeast, 35 g of lactic acid bacteria composite bacteria, 250 g of ZnO-BT / BC composite material, and 65 g of humic acid.

[0042] The ZnO-BT / BC composite material was prepared according to the following steps:

[0043] Dissolve Zn(NO3)2·6H2O in water to obtain a Zn(NO3)2 solution with a concentration of 0.05 mol / L. Dissolve NaOH in water to obtain a NaOH solution with a pH of 10. Disperse bentonite in water to obtain a bentonite suspension with a concentration of 0.3 g / mL. The bentonite is a sodium-based bentonite with a particle size of 200-300 mesh.

[0044] Add 500 g of biochar into 10000 mL of Zn(NO3)2 solution and stir well to obtain a suspension.

[0045] Under stirring, NaOH solution was added dropwise to the suspension, and the pH of the suspension was monitored in real time during the stirring process. When the pH of the suspension was adjusted to 9.0, the addition of NaOH solution was stopped. 100 mL of bentonite suspension was added, and stirring was continued for 4 hours to obtain a reaction solution.

[0046] The reaction solution was centrifuged to separate the solid from the supernatant, and the solid was washed with deionized water and then spray-dried to obtain a ZnO-BT / BC composite material.

[0047] The preparation method of the biological agent for reducing heavy metals in feed is as follows:

[0048] Bacillus subtilis, yeast, lactic acid bacteria, ZnO-BT / BC composite material and humic acid are mixed evenly according to proportion to obtain a biological bacterial agent for reducing heavy metals in feed.

[0049] Example 2

[0050] The only difference between this embodiment and embodiment 1 is that the biological agent for reducing heavy metals in feed includes the following raw materials: 100 g of Bacillus subtilis, 50 g of yeast, 50 g of lactic acid bacteria composite bacteria, 300 g of ZnO-BT / BC composite material, and 80 g of humic acid.

[0051] Example 3

[0052] The only difference between this embodiment and embodiment 1 is that the biological agent for reducing heavy metals in feed includes the following raw materials: 150 g of Bacillus subtilis, 25 g of yeast, 25 g of lactic acid bacteria composite bacteria, 200 g of ZnO-BT / BC composite material, and 50 g of humic acid.

[0053] Example 4

[0054] The difference between this embodiment and embodiment 1 is that, in the process of preparing the ZnO-BT / BC composite material, Zn(NO3)2·6H2O is dissolved in water to obtain a Zn(NO3)2 solution with a concentration of 0.01 mol / L. Bentonite is dispersed in water to obtain a bentonite suspension with a concentration of 0.1 g / mL.

[0055] Example 5

[0056] The difference between this embodiment and embodiment 1 is that, in the process of preparing the ZnO-BT / BC composite material, Zn(NO3)2·6H2O is dissolved in water to obtain a Zn(NO3)2 solution with a concentration of 0.1 mol / L. Bentonite is dispersed in water to obtain a bentonite suspension with a concentration of 0.5 g / mL.

[0057] Example 6

[0058] The only difference between this embodiment and embodiment 1 is that, in the process of preparing the ZnO-BT / BC composite material, NaOH is dissolved in water to obtain a NaOH solution with a pH of 12, and the NaOH solution is added dropwise to the suspension under stirring. The pH of the suspension is monitored in real time during stirring, and when the pH of the suspension is adjusted to 10.0, the addition of the NaOH solution is stopped.

[0059] Example 7

[0060] The only difference between this embodiment and embodiment 1 is that the bentonite is sodium-based bentonite with a particle size of 100-150 meshes.

[0061] Example 8

[0062] The only difference between this embodiment and embodiment 1 is that the bentonite is sodium-based bentonite with a particle size of 250-300 meshes.

[0063] Example 9

[0064] The only difference between this embodiment and embodiment 1 is that, in the process of preparing the ZnO-BT / BC composite material, the biochar is treated in advance as follows: HNO3 and water are mixed evenly in a volume ratio of 1:10 to obtain a nitric acid solution, and then the biochar is added to the nitric acid solution, heated to 40°C in a water bath, stirred for 4 hours under insulation, and then kept stirring, and 1 mol / L NaOH solution is added to adjust the pH to 6, the stirring is stopped, and the solid and the supernatant are separated by centrifugation. After washing the solid, it is dried to complete the pretreatment of the biochar.

[0065] Example 10

[0066] The only difference between this embodiment and embodiment 1 is that, in the process of preparing the ZnO-BT / BC composite material, the biochar is pre-treated as follows: HNO3 and water are evenly mixed in a volume ratio of 1:15 to obtain a nitric acid solution, and then the biochar is added to the nitric acid solution, heated to 60°C in a water bath, stirred for 1 hour under insulation, and then kept stirring, and 1 mol / L NaOH solution is added to adjust the pH to 7, the stirring is stopped, and centrifugation is performed to separate the solid and the supernatant. After washing the solid, it is dried to complete the pretreatment of the biochar.

[0067] Embodiment 11

[0068] The difference between this embodiment and embodiment 1 is that the biological agent for reducing heavy metals in feed includes the following raw materials: 125g of Bacillus subtilis, 35g of yeast, 35g of lactic acid bacteria composite bacteria, 250g of ZnO-BT / BC composite material, 65g of humic acid, and 50g of diatomaceous earth. The preparation method of the biological agent for reducing heavy metals in feed is as follows:

[0069] Bacillus subtilis, yeast, lactic acid bacteria, ZnO-BT / BC composite material, humic acid and diatomaceous earth are mixed evenly according to proportion to obtain a biological bacterial agent for reducing heavy metals in feed.

[0070] Example 12

[0071] The difference between this embodiment and embodiment 1 is that the biological agent for reducing heavy metals in feed includes the following raw materials: 125g of Bacillus subtilis, 35g of yeast, 35g of lactic acid bacteria composite bacteria, 250g of ZnO-BT / BC composite material, 65g of humic acid, and 100g of diatomaceous earth. The preparation method of the biological agent for reducing heavy metals in feed is as follows:

[0072] Bacillus subtilis, yeast, lactic acid bacteria, ZnO-BT / BC composite material, humic acid and diatomaceous earth are mixed evenly according to proportion to obtain a biological bacterial agent for reducing heavy metals in feed.

[0073] Example 13

[0074] The difference between this embodiment and embodiment 1 is that the biological agent for reducing heavy metals in feed includes the following raw materials: 125g of Bacillus subtilis, 35g of yeast, 35g of lactic acid bacteria, 250g of ZnO-BT / BC composite material, 65g of humic acid, and 10g of vitamin C. The preparation method of the biological agent for reducing heavy metals in feed is as follows:

[0075] Bacillus subtilis, yeast, lactic acid bacteria, ZnO-BT / BC composite material, humic acid and vitamin C are mixed evenly according to proportion to obtain a biological bacterial agent for reducing heavy metals in feed.

[0076] Embodiment 14

[0077] The difference between this embodiment and embodiment 1 is that the biological agent for reducing heavy metals in feed includes the following raw materials: 125g of Bacillus subtilis, 35g of yeast, 35g of lactic acid bacteria, 250g of ZnO-BT / BC composite material, 65g of humic acid, and 20g of vitamin C. The preparation method of the biological agent for reducing heavy metals in feed is as follows:

[0078] Bacillus subtilis, yeast, lactic acid bacteria, ZnO-BT / BC composite material, humic acid and vitamin C are mixed evenly according to proportion to obtain a biological bacterial agent for reducing heavy metals in feed.

[0079] Embodiment 15

[0080] The difference between this embodiment and embodiment 1 is that the biological agent for reducing heavy metals in feed includes the following raw materials: 125g of Bacillus subtilis, 35g of yeast, 35g of lactic acid bacteria composite bacteria, 250g of ZnO-BT / BC composite material, 65g of humic acid, 80g of skim milk powder, 30g of maltodextrin and 10g of glycerol. The preparation method of the biological agent for reducing heavy metals in feed is as follows:

[0081] Bacillus subtilis, yeast, lactic acid bacteria composite bacteria, ZnO-BT / BC composite material, humic acid, skim milk powder, maltodextrin and glycerol are mixed uniformly according to proportion to obtain a biological bacterial agent for reducing heavy metals in feed.

[0082] Example 16

[0083] The difference between this embodiment and embodiment 1 is that the biological agent for reducing heavy metals in feed includes the following raw materials: 125g of Bacillus subtilis, 35g of yeast, 35g of lactic acid bacteria composite bacteria, 250g of ZnO-BT / BC composite material, 65g of humic acid, 120g of skim milk powder, 50g of maltodextrin and 30g of glycerol. The preparation method of the biological agent for reducing heavy metals in feed is as follows:

[0084] Bacillus subtilis, yeast, lactic acid bacteria composite bacteria, ZnO-BT / BC composite material, humic acid, skim milk powder, maltodextrin and glycerol are mixed uniformly according to proportion to obtain a biological bacterial agent for reducing heavy metals in feed.

[0085] Embodiment 17

[0086] The difference between this embodiment and embodiment 1 is that the biological agent for reducing heavy metals in feed includes the following raw materials: 125g of Bacillus subtilis, 35g of yeast, 35g of lactic acid bacteria composite bacteria, 250g of ZnO-BT / BC composite material, 65g of humic acid, 50g of diatomaceous earth, 10g of vitamin C, 80g of skim milk powder, 30g of maltodextrin and 10g of glycerol. The preparation method of the biological agent for reducing heavy metals in feed is as follows:

[0087] Bacillus subtilis, yeast, lactic acid bacteria composite bacteria, ZnO-BT / BC composite material, humic acid, diatomaceous earth, vitamin C, skim milk powder, maltodextrin and glycerol are mixed evenly according to proportion to obtain a biological bacterial agent for reducing heavy metals in feed.

[0088] Comparative Example

[0089] Comparative Example 1

[0090] The difference between this comparative example and Example 1 is that the biological agent for reducing heavy metals in feed includes the following raw materials: 125g of Bacillus subtilis, 35g of yeast, and 35g of lactic acid bacteria. The preparation method of the biological agent for reducing heavy metals in feed is as follows:

[0091] Bacillus subtilis, yeast and lactic acid bacteria are mixed evenly according to proportion to obtain a biological bacterial agent for reducing heavy metals in feed.

[0092] Comparative Example 2

[0093] The difference between this comparative example and Example 1 is that the biological agent for reducing heavy metals in feed includes the following raw materials: 125g of Bacillus subtilis, 35g of yeast, 35g of lactic acid bacteria composite bacteria, and 250g of ZnO-BT / BC composite material. The preparation method of the biological agent for reducing heavy metals in feed is as follows:

[0094] Bacillus subtilis, yeast, lactic acid bacteria and ZnO-BT / BC composite materials are mixed evenly according to proportion to obtain a biological bacterial agent for reducing heavy metals in feed.

[0095] Comparative Example 3

[0096] The difference between this comparative example and Example 1 is that the biological agent for reducing heavy metals in feed includes the following raw materials: 125g of Bacillus subtilis, 35g of yeast, 35g of lactic acid bacteria, and 65g of humic acid. The preparation method of the biological agent for reducing heavy metals in feed is as follows:

[0097] Bacillus subtilis, yeast, lactic acid bacteria and humic acid are mixed evenly according to proportion to obtain a biological bacterial agent for reducing heavy metals in feed.

[0098] Comparative Example 4

[0099] The difference between this comparative example and Example 1 is that the biological agent for reducing heavy metals in feed includes the following raw materials: 125g of Bacillus subtilis, 250g of ZnO-BT / BC composite material, and 65g of humic acid. The preparation method of the biological agent for reducing heavy metals in feed is as follows:

[0100] Bacillus subtilis, ZnO-BT / BC composite material and humic acid are mixed evenly according to proportion to obtain a biological bacterial agent for reducing heavy metals in feed.

[0101] Comparative Example 5

[0102] The difference between this comparative example and Example 1 is that the biological agent for reducing heavy metals in feed includes the following raw materials: 35g yeast, 250g ZnO-BT / BC composite material, and 65g humic acid. The preparation method of the biological agent for reducing heavy metals in feed is as follows:

[0103] According to the proportion, 35 g of yeast, ZnO-BT / BC composite material and humic acid were uniformly mixed to obtain a biological agent for reducing heavy metals in feed.

[0104] Comparative Example 6

[0105] The difference between this comparative example and Example 1 is that the biological agent for reducing heavy metals in feed includes the following raw materials: 35g of lactic acid bacteria composite bacteria, 250g of ZnO-BT / BC composite material, and 65g of humic acid. The preparation method of the biological agent for reducing heavy metals in feed is as follows:

[0106] According to the proportion, 35 g of lactic acid bacteria composite bacteria, ZnO-BT / BC composite material and humic acid were uniformly mixed to obtain a biological bacterial agent for reducing heavy metals in feed.

[0107] Performance testing

[0108] The following performance tests were performed on the biological agents for reducing heavy metals in feed prepared in Examples 1-17 and Comparative Examples 1-6:

[0109] The biological agents of each embodiment and comparative example were stored in a dark environment at 35° C. and 40% humidity for 30 days. According to GB 20287-2006 Agricultural Microbial Agents, the number of viable bacteria of the biological agents on the 0th day and the 30th day was measured respectively. The survival rate of the strains in the biological agent was calculated according to the following formula: survival rate = number of viable bacteria of the biological agent on the 30th day ÷ number of viable bacteria of the biological agent on the 0th day × 100%.

[0110] Using Pb 2+ (100mg / kg), Cd 2+ (50mg / kg), As 3+ (30mg / kg) corn flour was used as feed. Biological agent, feed and water were weighed according to the weight ratio of biological agent: feed: water = 1:100:50, the water was heated to 45°C, and then the biological agent and water were mixed evenly, and then added to the feed, stirred evenly, heated to 37°C, and oscillated at a constant temperature for 24 hours, and the heavy metal concentration in the supernatant was determined (ICP-MS), and the heavy metal adsorption rate was calculated according to the heavy metal adsorption rate = (1-heavy metal concentration in supernatant ÷ original heavy metal concentration in feed) × 100%.

[0111] The test results are shown in Table 1.

[0112] Table 1

[0113]

[0114]

[0115] Combining Example 1 and Comparative Examples 1-6 and Table 1, it can be seen that compared with Example 1, the Pb 2+ Adsorption rate, Cd 2+ Adsorption rate, As 3+ The adsorption rate was significantly reduced, and the survival rate of the strains did not change much. This shows that under the raw material ratio and preparation method of Example 1, it is helpful to improve the removal effect of heavy metals in feed and reduce the heavy metals in feed. Moreover, in the case of lack of any one of the strains, ZnO-BT / BC composite materials, and humic acid, the removal effect of heavy metals is poor.

[0116] Combining Examples 1-6 and Table 1, it can be seen that the Pb in Examples 1-6 2+ Adsorption rate, Cd 2+ Adsorption rate, As 3+ The adsorption rate is relatively high, and the survival rate of the bacteria is above 80%, which shows that within the range of raw material ratios and process conditions of Examples 1-6, it is helpful to prepare a biological bacterial agent with good heavy metal removal effect.

[0117] Combining Examples 1, 7-8 and Table 1, it can be seen that compared with Example 1, the Pb 2+ Adsorption rate, Cd 2+ Adsorption rate, As 3+ The adsorption rates are all small, which indicates that the use of sodium bentonite with a particle size of 200-300 mesh can help further improve the removal effect of ZnO-BT / BC composite materials and biological agents on heavy metals.

[0118] Combining Examples 1, 9-17 and Table 1, it can be seen that compared with Example 1, the Pb 2+ Adsorption rate, Cd 2+ Adsorption rate, As 3+ The adsorption rate or bacterial survival rate increases, which indicates that the addition of diatomaceous earth, vitamin C, skimmed milk powder, maltodextrin and glycerol can improve the heavy metal removal effect of biological agents or the survival rate of bacterial strains.

[0119] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A biological agent for reducing heavy metals in feed, characterized in that: The invention comprises the following raw materials in parts by weight: 100-150 parts of Bacillus subtilis, 25-50 parts of yeast, 25-50 parts of lactic acid bacteria, 200-300 parts of ZnO-BT / BC composite material and 50-80 parts of humic acid. The ZnO-BT / BC composite material is a composite material formed by co-loading nano zinc oxide and bentonite on biochar.

2. The biological agent for reducing heavy metals in feed according to claim 1, characterized in that: The preparation method of the ZnO-BT / BC composite material comprises the following steps: Dissolve Zn(NO3)2·6H2O in water to obtain a Zn(NO3)2 solution with a concentration of 0.01-0.1 mol / L, dissolve NaOH in water to obtain a NaOH solution with a pH of 10-12, and disperse bentonite in water to obtain a bentonite suspension with a concentration of 0.1-0.5 g / mL; Add the biochar to the Zn(NO3)2 solution and stir evenly to obtain a suspension; Add NaOH solution to the suspension to adjust the pH to 9.0-10.0, stop adding NaOH solution, then add bentonite suspension, stir evenly to obtain a reaction solution; The reaction solution was centrifuged to separate the solid from the supernatant, and the solid was washed with deionized water and dried to obtain a ZnO-BT / BC composite material.

3. The biological agent for reducing heavy metals in feed according to claim 2, characterized in that: The biochar is pre-treated as follows: HNO3 and water are mixed in a volume ratio of 1:(10-15) to obtain a nitric acid solution; the biochar is added to the nitric acid solution, heated in a water bath at 40-60°C, stirred for 1-4 hours, and then a 1 mol / L NaOH solution is added to adjust the pH to 6-7, stirring is stopped, centrifugation is performed to separate the solid and the supernatant, the solid is washed, and then dried to complete the pretreatment of the biochar.

4. The biological agent for reducing heavy metals in feed according to claim 2, characterized in that: The bentonite is sodium-based bentonite with a particle size of 200-300 meshes.

5. The biological agent for reducing heavy metals in feed according to claim 1, characterized in that: The biological agent for reducing heavy metals in feed also includes the following raw materials in parts by weight: 50-100 parts of diatomaceous earth.

6. The biological agent for reducing heavy metals in feed according to claim 1, characterized in that: The biological agent for reducing heavy metals in feed also includes the following raw materials in parts by weight: 10-20 parts of vitamin C.

7. The biological agent for reducing heavy metals in feed according to claim 1, characterized in that: The biological agent for reducing heavy metals in feed also includes the following raw materials in parts by weight: 80-120 parts of skim milk powder, 30-50 parts of maltodextrin and 10-30 parts of glycerol.

8. A method for preparing a biological agent for reducing heavy metals in feed according to any one of claims 1 to 7, characterized in that: Bacillus subtilis, yeast, lactic acid bacteria composite bacteria, ZnO-BT / BC composite materials and humic acid are uniformly mixed to obtain a biological bacterial agent for reducing heavy metals in feed.

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