Microbial flocculant as well as preparation method and application thereof

Abstract

The invention discloses a microbial flocculant and a preparation method and application thereof, the microbial flocculant is composed of a composite strain, a composite fermentation broth extract and an auxiliary agent according to a mass ratio of (5-10): (1-5): (1-2), and the composite strain is composed of bacillus licheniformis, bacillus cereus, bacillus cereus and saccharomycetes according to a mass ratio of (10-30): (5-10): (5-10): (10-20). The compound fermentation liquor extract is obtained by freezing and drying a supernatant obtained by centrifuging a mixed fermentation liquor of bacillus licheniformis fermentation liquor, bacillus cereus fermentation liquor, bacillus cereus and saccharomycetes fermentation liquor according to a mixing volume ratio of 1: 1: 1: 1, wherein the mixed fermentation liquor is prepared from bacillus licheniformis fermentation liquor, bacillus cereus fermentation liquor, bacillus cereus and saccharomycetes fermentation liquor; the auxiliary agent is composed of sodium alginate, chitosan and gelatin in a mass ratio of (1-5): (1-3): (1-2). The flocculation rate of the microbial flocculant in sewage treatment can reach 90% or above, and the microbial flocculant has a good flocculation effect.

Description

Technical Field

[0001] The invention relates to the field of environmentally friendly microorganisms, and in particular to a microbial flocculant and a preparation method and application thereof. Background Art

[0002] Flocculants are widely used in sewage treatment. Traditional flocculants can generally be divided into inorganic flocculants, organic synthetic polymer flocculants, and natural organic polymer flocculants. Inorganic flocculants include aluminum sulfate, polyaluminum chloride, polyferric sulfate, polyferric chloride, alum, etc.; organic synthetic polymer flocculants include polyethylene oxide, polystyrene sulfonate, polyacrylamide derivatives, etc.; natural organic polymer flocculants include cellulose, polyglucosamine, sodium alginate and microbial flocculants. Many inorganic flocculants and organic synthetic polymer flocculants have been widely used due to their good flocculation effect and low cost. However, people have found that they have great insecurity and potential secondary pollution problems during use. In addition, natural polymer flocculants also have disadvantages such as weak flocculation activity and high cost of use. Bioflocculants are obtained by fermentation and refining of bacteria, fungi and other microorganisms using microbial technology. They are mainly composed of glycoproteins, polysaccharides, proteins and DNA using microbial technology. They are generally made by microbial fermentation and organic solvent extraction. They are a new type of non-toxic and efficient water treatment agent without secondary pollution. They are composed of special macromolecular metabolites produced by microorganisms that can agglomerate and precipitate non-degradable solid suspended particles, bacterial cells and colloidal particles in liquids. Since microbial flocculants can overcome the inherent defects of inorganic polymers and synthetic organic polymer flocculants, they have the characteristics of high efficiency, non-toxicity and no secondary pollution, and are biodegradable and safe, and have good application prospects in the field of environmental protection.

[0003] Therefore, developing a new type of bioflocculant that is safe, non-toxic, has high flocculation activity, and has no secondary pollution has important practical significance for human health and environmental protection. Summary of the invention

[0004] In view of the problems existing in the prior art, one of the purposes of the present invention is to provide a microbial flocculant, which has good flocculation effect and good application prospect.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a microbial flocculant, the raw materials of which include a composite bacterial strain, a composite fermentation broth extract and an auxiliary agent, and the mass ratio of the composite bacterial strain, the composite fermentation broth extract and the auxiliary agent is (5-10): (1-5): (1-2); The composite strain is composed of Bacillus licheniformis, Bacillus chestnut brown, Bacillus cereus and yeast. The Bacillus licheniformis is a strain with a preservation number of CCTCC NO: M2022862, the Bacillus chestnut brown is a strain with a preservation number of CCTCC NO: M2022863, the Bacillus cereus is a strain with a preservation number of CCTCC NO: M2022867, and the yeast is a strain with a preservation number of CCTCC NO: M2022868. The mass ratio of the Bacillus licheniformis, the Bacillus chestnut brown, the Bacillus cereus and the yeast is (10-30): (5-10): (5-10): (10-20); The composite fermentation broth extract is obtained by extracting the supernatant of a mixture of Bacillus licheniformis fermentation broth, Bacillus chestnut fermentation broth, Bacillus cereus and yeast fermentation broth after centrifugation; The auxiliary agent consists of sodium alginate, chitosan and gelatin.

[0006] Preferably, the live bacteria concentration of the Bacillus licheniformis, Bacillus chestnutii, and Bacillus cereus is ≥ 1×10 9 CFU / mL, the live bacteria concentration in the yeast strain is ≥1×10 8 CFU / mL.

[0007] Preferably, the composite fermentation broth extract is obtained by freeze-drying the supernatant of a mixed fermentation broth of Bacillus licheniformis fermentation broth, Bacillus chestnut brown fermentation broth, Bacillus cereus and yeast fermentation broth in a mixed volume ratio of 1:1:1:1 after centrifugation.

[0008] Preferably, the mass ratio of sodium alginate, chitosan and gelatin is (1-5): (1-3): (1-2).

[0009] Another object of the present invention is to provide a method for preparing the microbial flocculant, which utilizes agricultural waste to produce microbial flocculants, thereby realizing resource utilization of agricultural waste and reducing environmental pollution. The method comprises the following steps: Bacillus licheniformis, Bacillus chestnut brown, and Bacillus cereus were inoculated into seed culture medium respectively, and cultured in a shaking incubator at 28-35°C for 16-24h to prepare seed solution; Then, the seed liquid of each bacterial species is inoculated into the fermentation medium of each bacterial strain at a ratio of 1% to 10% for fermentation culture for 48 to 96 hours to obtain fermentation liquid of different bacterial species; After the fermentation culture is completed, 1-3% protective agent is added and stirred evenly to protect the bacteria and aid coagulation. The fermentation liquid is then centrifuged at 4-8°C for 15-20 min, and the sludge precipitate and supernatant are collected respectively. The sludge precipitate is dried at low temperature to obtain high-concentration strains of different strains and mixed evenly to obtain a composite strain. Add 2 to 4 times the volume of pre-cooled anhydrous ethanol to the fermentation supernatant, centrifuge at 10000 to 12000 r / min for 10 to 15 minutes to collect the precipitate, wash it twice with an ethanol solution with a volume fraction of 70% to 75%, and freeze-dry it to obtain a composite fermentation broth extract, and fully mix the composite strain and the composite fermentation broth extract to obtain a microbial flocculant.

[0010] Preferably, the seed culture medium of Bacillus licheniformis, Bacillus chestnut brown and Bacillus cereus used in the preparation method of the microbial flocculant is beef extract peptone culture medium, and the culture medium formula is: beef extract 3g / L, peptone 10g / L, NaCl 5g / L, pH7.4-7.6.

[0011] Preferably, the yeast seed culture medium used in the preparation method of the microbial flocculant is YEPD culture medium, the culture medium formula is: 20g / L glucose, 3g / L yeast powder, 10g / L tryptone, and the initial pH is 7.0-7.2.

[0012] Preferably, the Bacillus licheniformis fermentation medium used in the preparation method of the microbial bioflocculant is composed of 20-40 g / L wheat bran, 2-5 g / L glucose, 10-20 g / L soybean powder, 2-3 g / L dipotassium hydrogen phosphate, 1-2 g / L potassium dihydrogen phosphate, 0.1-0.3 g / L ferrous sulfate, 0.2-0.4 g / L magnesium sulfate heptahydrate, and 0.2-0.5 g / L sodium chloride, and the initial pH is 7.2-8.0. Preferably, the formula of the chestnut brown Bacillus fermentation medium used in the preparation method of the microbial bioflocculant is: 30-50 g / L corn cob powder, 2-5 g / L sucrose, 15-30 g / L soybean cake powder, 0.1-0.5 g / L magnesium chloride, 0.001-0.003 g / L manganese sulfate, and pH 7.0-7.2.

[0013] Preferably, the formula of the Bacillus cereus fermentation medium used in the preparation method of the microbial bioflocculant is: 10-30 g / L rice husk powder, 3-8 g / L corn steep liquor, 10-20 g / L mushroom residue powder, 1-3 g / L potassium dihydrogen phosphate, 1-3 g / L dipotassium hydrogen phosphate, 0.2-0.4 g / L magnesium sulfate heptahydrate, 0.3-0.8 g / L sodium chloride, 0.1-0.5 g / L calcium chloride, and the initial pH is 6.5-7.5.

[0014] Preferably, the yeast fermentation medium used in the preparation method of the microbial bioflocculant is composed of 30-50 g / L bran, 10-20 g / L soybean meal, 5-10 g / L corn flour, 5-15 g / L rice bran, 2-8 g / L corn steep liquor, 0.4-2.5 g / L ammonium sulfate, 0.1-0.5 g / L potassium dihydrogen phosphate and 0.03-0.3 g / L magnesium sulfate, and the initial pH is 4.5-6.5.

[0015] Preferably, the fermentation conditions of Bacillus licheniformis, Bacillus chestnut brown, Bacillus cereus and yeast used in the preparation method of the microbial flocculant are: inoculation amount 1-10%, fermentation temperature 28-35°C, rotation speed 150-240 r / min, constant temperature shaking box culture for 48-96 h.

[0016] Preferably, the strain protective agent is sorbitol, and the percentage of the protective agent to the fermentation broth is 1%. Preferably, the drying temperature of each bacterial strain is 35° C. to 45° C., and the water content of the composite bacterial strain after drying is less than 20%.

[0017] Another object of the present invention is to provide an application of the microbial flocculant in sewage treatment. The microbial flocculant of the present invention has a significant flocculation effect, and the flocculation rate can reach more than 90%. It can be widely used in the flocculation of various water bodies such as domestic sewage and black and smelly water in rivers, and is of great significance to the treatment and restoration of water bodies in different environments.

[0018] Preferably, the usage amount of the microbial flocculant is 0.05%~0.5%.

[0019] Compared with the prior art, the present invention has the following advantages: (1) The flocculant of the present invention is composed of multiple strains of Bacillus licheniformis, Bacillus chestnut brown, Bacillus cereus, yeast, their metabolic flocculation components and auxiliary agents, and has a high-efficiency and rapid flocculation effect.

[0020] (2) The present invention utilizes agricultural waste bran as the main carbon source to produce bioflocculant, which can realize the resource utilization of waste, turn waste into treasure, reduce environmental pollution, and reduce production costs. (3) The flocculants produced by the strains of Bacillus licheniformis, Bacillus chestnut brown, Bacillus cereus and yeast involved in the present invention have high flocculation activity and good flocculation effect. The obtained biological flocculants have significant flocculation effect, with a flocculation rate of more than 90%, and have good application prospects.

[0021] (4) The present invention has low production cost, simple production process, and is easy to realize industrial production and promotion.

[0022] (5) The materials used and substances produced in the preparation process of the microbial flocculant of the present invention will not cause environmental pollution and are safe to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 This is a comparison chart of the flocculation rates of microbial flocculants 1 to 6 on kaolin suspension in Test Example 1; Figure 2 This is a comparison chart of the flocculation rates of microbial flocculants 1 to 6 on domestic sewage in Test Example 2; Figure 3 This is a comparison chart of the flocculation rates of microbial flocculants 1 to 6 on black and smelly river water in Test Example 3. DETAILED DESCRIPTION

[0025] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the embodiments of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0026] In the present invention, all the raw materials mentioned can be purchased commercially or / and prepared by known means, and unless otherwise specified, they all meet the requirements of standard chemical products.

[0027] The experimental methods used in the present invention are all conventional methods unless otherwise specified.

[0028] In the present invention, Bacillus licheniformis ( Bacillus paralicheniformis ) strain, deposited in China Center for Type Culture Collection on June 13, 2022, with the deposit number CCTCC NO: M2022862; Bacillus chestnut brown Bacillus badius) strain, deposited in China Center for Type Culture Collection on June 13, 2022, with the deposit number: CCTCC M 2022863; Bacillus cereus ( Bacillus cereus ) strain, deposited in China Center for Type Culture Collection on June 13, 2022, with the deposit number CCTCC NO: M2022867; Yeast ( Rhodotorula sp. ) strain, deposited in the China Center for Type Culture Collection on June 13, 2022, with the deposit number: CCTCC M 2022868.

[0029] In the present invention, the preparation method of each strain and composite fermentation broth extract is: (1) Strain activation: Bacillus licheniformis, Bacillus chestnut brown, and Bacillus cereus were streaked onto beef extract peptone plate culture medium (culture medium formula: beef extract 3 g / L, peptone 10 g / L, NaCl 5 g / L, agar powder 20 g / L, pH 7.4-7.6) under aseptic conditions, and cultured in a constant temperature incubator at 30°C for 24 h; yeast strains were streaked onto YEPD plate culture medium (culture medium formula: glucose 20 g / L, yeast powder 3 g / L, trypsin 10 g / L, agar powder 20 g / L, pH 7.0-7.2) under aseptic conditions, and cultured in a constant temperature incubator at 28°C for 36 h.

[0030] (2) Preparation of strain seed solution: Pick the Bacillus licheniformis, Bacillus chestnut brown, and Bacillus cereus from the plate culture medium and inoculate them into a 500mL Erlenmeyer flask containing 100mL of culture medium (culture medium formula: 3g / L beef extract, 10g / L peptone, 5g / L NaCl, pH 7.4-7.6), culture them at 30°C for 16h-24h, and observe under a microscope. The strains are in the logarithmic growth phase and free of foreign bacteria, thereby obtaining the Bacillus licheniformis, Bacillus chestnut brown, and Bacillus cereus seed solutions; pick the yeast from the plate culture medium and inoculate them into a 500mL Erlenmeyer flask containing 100mL of culture medium (culture medium formula: 20g / L glucose, 3g / L yeast powder, 10g / L tryptone, pH 7.0-7.2), culture them at 30°C for 24h-36h, and observe under a microscope. Free of foreign bacteria, thereby obtaining the yeast seed solution.

[0031] (3) Preparation of culture materials: Weigh the components of the culture medium, adjust the initial pH and add them to a 3 L shake flask.

[0032] Among them: Bacillus licheniformis fermentation medium: wheat bran 20-40 g / L, glucose 2-5 g / L, soybean powder 10-20 g / L, dipotassium hydrogen phosphate 2-3 g / L, potassium dihydrogen phosphate 1-2 g / L, ferrous sulfate 0.1-0.3 g / L, magnesium sulfate heptahydrate 0.2-0.4 g / L, sodium chloride 0.2-0.5 g / L, initial pH is 7.2-8.0. Bacillus chestnut fermentation medium: corn cob powder 30~50g / L, sucrose 2~5 g / L, soybean cake powder 15~30 g / L, magnesium chloride 0.1~0.5 g / L, manganese sulfate 0.001~0.003g / L, pH 7.0~7.2; Bacillus cereus fermentation medium: rice husk powder 10-30 g / L, corn steep liquor 3-8 g / L, mushroom residue powder 10-20 g / L, potassium dihydrogen phosphate 1-3 g / L, dipotassium hydrogen phosphate 1-3 g / L, magnesium sulfate heptahydrate 0.2-0.4 g / L, sodium chloride 0.3-0.8 g / L, calcium chloride 0.1-0.5 g / L, initial pH 6.5-7.5; Yeast fermentation medium: bran 30~50 g / L, soybean meal 10~20 g / L, corn flour 5~10 g / L, rice bran 5~15 g / L, corn steep liquor 2~8 g / L, ammonium sulfate 0.4~2.5 g / L, potassium dihydrogen phosphate 0.1~0.5 g / L and magnesium sulfate 0.03~0.3 g / L, with an initial pH of 4.5~6.5.

[0033] (4) Preparation of fermentation broth: Under sterile conditions, the seed liquid of Bacillus licheniformis, Bacillus chestnut brown, and Bacillus cereus was transferred to a 3L shaking flask at an inoculation rate of 1-8%, respectively, and the fermentation temperature was 30-35°C, and the rotation speed was 150-240 r / min in a constant temperature shaking box for 48-72 h. The fermentation was examined under a microscope, and the fermentation bacteria count (≧10 9 The fermentation broth of Bacillus licheniformis, Bacillus chestnut brown and Bacillus cereus was obtained by measuring the spore rate (≧95%) and / or spore rate level (≧95%); the yeast seed liquid was transferred to a 3L shaking flask at an inoculation rate of 5-10% under sterile conditions, and the fermentation temperature was 28-32°C and the rotation speed was 150-240 r / min in a constant temperature shaking box for 72-96 h. The fermentation bacteria amount (≧10 8 / mL), to obtain the yeast fermentation broth.

[0034] (5) Fermentation broth pretreatment: After the fermentation culture of Bacillus licheniformis, Bacillus chestnut brown, Bacillus cereus and yeast is completed, 1% of a protective agent is added to each of them and stirred evenly. Then, the fermentation broth of Bacillus licheniformis, Bacillus chestnut brown, Bacillus cereus and yeast is centrifuged at 4-8°C for 15-20 min, and the sludge precipitate and supernatant of each strain are collected.

[0035] (6) Preparation of strains: The bacterial sludge of the Bacillus licheniformis, Bacillus chestnut brown, Bacillus cereus and yeast were precipitated and dried at 35-45° C. to obtain high-concentration strains of Bacillus licheniformis, Bacillus chestnut brown, Bacillus cereus and yeast.

[0036] (7) Preparation of composite fermentation broth extract: The fermentation supernatants of Bacillus licheniformis, Bacillus chestnut brown, Bacillus cereus and yeast were mixed uniformly in a volume ratio of 1:1:1:1, 2 to 4 times the volume of pre-cooled anhydrous ethanol was added to the mixed fermentation supernatant, and the precipitate was collected by centrifugation at 10000-12000 r / min for 10-15 min, and the precipitate was washed twice with 70% to 75% ethanol solution by volume, and freeze-dried to obtain a composite fermentation broth extract.

[0037] Example 1 This embodiment provides a microbial flocculant, and the preparation method thereof is as follows: The Bacillus licheniformis, Bacillus chestnut brown, Bacillus cereus and yeast strains are mixed uniformly in a mass ratio of 10:5:5:10 to prepare a composite strain 1; the auxiliary agents sodium alginate, chitosan and gelatin are mixed uniformly in a mass ratio of 2:2:1 to prepare a composite auxiliary agent 1; and then the composite strain 1, the composite fermentation liquid extract and the auxiliary agent 1 are fully mixed uniformly in a mass ratio of 5:3:1 to obtain a microbial flocculant 1.

[0038] Example 2 This embodiment provides a microbial flocculant, and its preparation method is basically the same as that of Example 1, except that in this embodiment, the mass ratio of Bacillus licheniformis, Bacillus chestnut brown, Bacillus cereus and yeast strains is adjusted to 20:10:10:20; the mass ratio of auxiliary agents sodium alginate, chitosan and gelatin is adjusted to 3:2:2; the mass ratio of composite strains, composite fermentation broth extract and auxiliary agents is adjusted to 10:5:2, and the mixture is fully mixed to obtain microbial flocculant 2.

[0039] Example 3 This embodiment provides a microbial flocculant, and its preparation method is basically the same as that of Example 1, except that in this embodiment, the mass ratio of Bacillus licheniformis, Bacillus chestnut brown, Bacillus cereus and yeast strains is adjusted to 30:5:10:10; the mass ratio of auxiliary agents sodium alginate, chitosan and gelatin is adjusted to 1:3:2; the mass ratio of the composite strain, the composite fermentation broth extract and the auxiliary agent is adjusted to 8:1:2, and the mixture is fully mixed to obtain microbial flocculant 3.

[0040] Example 4 This embodiment provides a microbial flocculant, and its preparation method is basically the same as that of Example 1, except that in this embodiment, the mass ratio of Bacillus licheniformis, Bacillus chestnut brown, Bacillus cereus and yeast strains is adjusted to 25:8:8:15; the mass ratio of auxiliary agents sodium alginate, chitosan and gelatin is adjusted to 3:2:1; the mass ratio of the composite strain, the composite fermentation broth extract and the auxiliary agent is adjusted to 6:4:1, and the mixture is fully mixed to obtain microbial flocculant 4.

[0041] Comparative Example 1 This comparative example provides a microbial flocculant, and its preparation method is basically the same as that of Example 1, except that in this comparative example, the mass ratio of Bacillus licheniformis, Bacillus chestnut brown, Bacillus cereus and yeast strains is adjusted to 5:4:8:10; the mass ratio of auxiliary agents sodium alginate, chitosan and gelatin is adjusted to 1:5:3; the mass ratio of the composite strain, the composite fermentation broth extract and the auxiliary agent is adjusted to 3:6:3, and the mixture is fully mixed to obtain microbial flocculant 5.

[0042] Comparative Example 2 This comparative example provides a microbial flocculant, and its preparation method is basically the same as that of Example 1, except that in this comparative example, the mass ratio of Bacillus licheniformis, Bacillus chestnut brown, Bacillus cereus and yeast strains is adjusted to 20:15:15:10; the mass ratio of auxiliary agents sodium alginate, chitosan and gelatin is adjusted to 1:2:4; the mass ratio of the composite strains, the composite fermentation broth extract and the auxiliary agents is adjusted to 5:4:4, and the mixture is fully mixed to obtain microbial flocculant 6.

[0043] Test Example 1: A 0.4% kaolin suspension was prepared, and the flocculation rates of the microbial flocculants 1 to 6 prepared in Examples 1 to 4 and Comparative Examples 1 to 2 were measured respectively according to the following method.

[0044] Determination method: Add 0.4g 60 mesh kaolin, 80ml distilled water, 5ml 1% CaCl2, and 2g flocculant to a 100ml measuring cylinder, mix, add distilled water to 100ml, adjust pH to 7.0, shake well, let stand for 5 minutes, measure the turbidity of the upper phase at 550nm with a spectrophotometer, and use the turbidity of the upper phase without flocculant as the control. The degree of flocculation is determined by the reduction of turbidity. The flocculation rate is used to quantitatively represent the flocculation activity.

[0045]

[0046] A: Optical density of the upper phase solution at 550nm B: Optical density of the treated upper phase at 550 nm.

[0047] See attached for the results Figure 1 The flocculation rate of the microbial flocculants 1~4 treatment groups can reach more than 90%. The flocculation effect of microbial flocculants 1~4 is significantly better than that of microbial flocculants 5~6, and the flocculation effect of microbial flocculants 5~6 is relatively weak.

[0048] Test Example 2 Take 500mL of domestic sewage with a pH of 7.79 and a turbidity of 390 NTU. Mix the microbial flocculants 1 to 6 with the domestic sewage sample at a final concentration of 0.1%, place in a 30℃ shaker, rotate at 240 r / min and react for 15 minutes. After standing for 20 minutes, measure the flocculation rate. The flocculation rate measurement results are attached. Figure 2 Compared with the control group without adding composite microbial flocculants, the water body became significantly clearer, and the flocculation rate of the treatment group of microbial flocculants 1 to 4 reached more than 90%, and the flocculation effect of microbial flocculants 1 to 4 was significantly better than that of microbial flocculants 5 to 6.

[0049] Test Example 3: Take 500mL of black and smelly river water with a pH of 8.22 and a turbidity of 115 NTU. Mix the microbial flocculants 1 to 6 with the black and smelly river water at a final concentration of 0.05%, place in a 30℃ shaker at a speed of 240 r / min for 15 minutes. After standing for 20 minutes, measure the flocculation rate. The results of the flocculation rate are shown in the attached Figure 3 Compared with the control group without adding composite microbial flocculants, the water body was obviously clarified, the suspended particles settled to the bottom, and the turbidity of the treatment group of microbial flocculants 1~4 was reduced by more than 90%. The microbial flocculants had a good flocculation effect, and the flocculation effect of microbial flocculants 1~4 was better than that of microbial flocculants 5~6.

[0050] The test results of test examples 1-3 show that the flocculant composed of multiple strains of Bacillus licheniformis, Bacillus chestnut brown, Bacillus cereus, yeast, their metabolic flocculation components and additives has a high-efficiency and rapid flocculation effect. And by controlling the proportion of each component of the flocculant, the flocculation rate of the flocculant is as high as 90% or more, which has a good application prospect.

[0051] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A microbial flocculant, characterized in that: The raw materials include composite bacteria, composite fermentation broth extract and auxiliary agent, and the mass ratio of the composite bacteria, the composite fermentation broth extract and the auxiliary agent is (5-10): (1-5): (1-2); The composite strain is composed of Bacillus licheniformis, Bacillus chestnut brown, Bacillus cereus and yeast. The Bacillus licheniformis is a strain with a preservation number of CCTCC NO: M2022862, the Bacillus chestnut brown is a strain with a preservation number of CCTCC NO: M2022863, the Bacillus cereus is a strain with a preservation number of CCTCC NO: M2022867, and the yeast is a strain with a preservation number of CCTCC NO: M2022868. The mass ratio of the Bacillus licheniformis, the Bacillus chestnut brown, the Bacillus cereus and the yeast is (10-30): (5-10): (5-10): (10-20); The composite fermentation broth extract is obtained by extracting the supernatant of a mixture of Bacillus licheniformis fermentation broth, Bacillus chestnut fermentation broth, Bacillus cereus and yeast fermentation broth after centrifugation; The auxiliary agent consists of sodium alginate, chitosan and gelatin.

2. The microbial flocculant according to claim 1, characterized in that: The live bacteria concentration of the Bacillus licheniformis, Bacillus chestnutii and Bacillus cereus is ≥ 1×10 9 CFU / mL, the live bacteria concentration in the yeast strain is ≥1×10 8 CFU / mL.

3. The microbial flocculant according to claim 1, characterized in that: The composite fermentation broth extract is obtained by freeze-drying the supernatant of a mixed fermentation broth of Bacillus licheniformis fermentation broth, Bacillus chestnut fermentation broth, Bacillus cereus and yeast fermentation broth in a mixed volume ratio of 1:1:1:1 after centrifugation.

4. The microbial flocculant according to claim 1, characterized in that: The mass ratio of the sodium alginate, chitosan and gelatin is (1-5): (1-3): (1-2).

5. The method for preparing the microbial flocculant according to any one of claims 1 to 4, characterized in that: The steps include: Bacillus licheniformis, Bacillus chestnut brown, and Bacillus cereus were inoculated into seed culture medium respectively, and cultured in a shaking incubator at 28-35°C for 16-24h to prepare seed solution; The seed liquid of each strain was inoculated into the fermentation medium of each strain at a ratio of 1% to 10% for fermentation culture for 48 to 96 hours to obtain the fermentation liquid of different strains; After the fermentation culture is completed, the auxiliary agent is added and stirred evenly to protect the bacteria. The fermentation liquid is centrifuged at 4-8°C for 15-20 min, and the bacterial sludge precipitate and the supernatant are collected respectively. The bacterial sludge is precipitated and dried at low temperature to obtain strains of different strains, which are mixed evenly to obtain a composite strain. Add 2 to 4 times the volume of pre-cooled anhydrous ethanol to the fermentation supernatant, centrifuge at 10000 to 12000 r / min for 10 to 15 minutes to collect the precipitate, wash it twice with an ethanol solution with a volume fraction of 70% to 75%, and freeze-dry it to obtain a composite fermentation broth extract, and fully mix the composite strain and the composite fermentation broth extract to obtain a microbial flocculant.

6. The method for preparing a microbial flocculant according to claim 5, characterized in that: The drying temperature of each bacterial strain is 35° C. to 45° C., and the water content of the composite bacterial strain after drying is less than 20%.

7. Use of the microbial flocculant according to any one of claims 1 to 4, or the microbial flocculant prepared by the preparation method according to any one of claims 5 to 6 in sewage treatment.

8. The use in sewage treatment according to claim 7, characterized in that: The usage of the microbial flocculant is 0.05%~0.5%.

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