Brevibacillus laterosporus r81 producing capsular polysaccharide and application thereof in dye decolorization

Abstract

The present application belongs to the field of microbial technology, and particularly relates to a Brevibacillus laterosporus R81 producing capsular polysaccharide and application of the Brevibacillus laterosporus R81 in dye decolorization. The present application provides a Brevibacillus laterosporus R81, which has been biologically preserved with a preservation number of CCTCC NO: M20221010. The Brevibacillus laterosporus R81 of the present application has a capsule, can adsorb anthraquinone dyes through capsular polysaccharide, and has excellent dye decolorization capacity; after the Brevibacillus laterosporus R81 cell is modified and treated by pectinase, the self-aggregation property of the cell is strengthened, and the cell is convenient for recycling from wastewater. Meanwhile, the strain R81 has good repeatability and the property of dye desorption and recycling; after the cell adsorbing RB19 is treated by 0.5 mol / L NaOH solution for 6 h, the adsorbed RB19 can be desorbed, and the desorbed cell has the ability of adsorbing RB19 again.

Description

Technical Field

[0001] This invention belongs to the field of microbial technology, specifically relating to a strain of Bacillus retroflexus R81 that produces capsular polysaccharides and its application in dye decolorization. Background Technology

[0002] Dyes are widely used in industries such as plastics, rubber, inks, leather, food, and papermaking, with the printing and dyeing industry being the primary application area. Currently, with the increasing number and scope of bans on azo dyes, and the advantages of anthraquinone dyes such as bright colors and good colorfastness, the use of anthraquinone dyes in the printing, dyeing, and textile industries is increasing year by year. However, most anthraquinone dyes are aromatic hydrocarbons and heterocyclic compounds with stable conjugated structures. They are not only structurally complex but also possess potential toxicity, have high chemical oxygen demand (COD) while relatively low biological oxygen demand (BOD), making them difficult to degrade and resulting in well-known, difficult-to-treat organic wastewater. Therefore, the treatment of anthraquinone dye wastewater has become one of the major environmental challenges urgently needing to be addressed.

[0003] Currently, the main methods for treating dyeing and printing wastewater are divided into physical, chemical, and biological methods. Physical and chemical methods mainly include adsorption, membrane separation, chemical precipitation, photodecomposition, electrochemical methods, chemical oxidation, and reduction. Membrane separation utilizes selectively permeable membranes of various pore sizes to separate and purify mixtures, offering advantages such as high separation efficiency and simple processes. However, its large-scale application is limited by high equipment investment, potential membrane fouling risks, and the need for secondary wastewater treatment. Chemical oxidation uses strong oxidants to break unsaturated double bonds in dye molecules, forming low-molecular-weight organic or inorganic compounds, thereby reducing wastewater color and achieving wastewater purification. For example, the advanced oxidation process for wastewater based on H2O2 / UV technology offers advantages such as high decolorization and COD removal rates in a short time, and no sludge generation. However, this method has poor dye universality, low decolorization efficiency for treating high-color wastewater, and generates harmful byproducts, resulting in high economic costs. While electrochemical oxidation can effectively destroy organic compounds without producing harmful byproducts, its high operating cost limits its application. Adsorption methods remove dyes based on the spontaneous accumulation or aggregation of pollutants on the surface of porous solid adsorbents. Activated carbon, activated diatomaceous earth, natural montmorillonite, fibers, and cinders are commonly used adsorbents in this method, especially activated carbon, which is widely used for removing multiple dyes. However, the cost of using and regenerating adsorbents significantly limits the practical application of adsorption methods. Adsorption methods require adsorbents with high affinity for the target dye, regenerability, and low preparation and usage costs.

[0004] In recent years, highly efficient biosorbent materials prepared based on the biosorption of fungi, bacteria, algae, etc., have shown excellent practical application potential in the adsorption and removal of pollutants such as heavy metals and dyes. Biosorption is the adsorption of pollutants by biological cells using their special structure, metabolism, and products through extracellular precipitation, cell surface complexation, ion exchange, redox reactions, and inorganic microprecipitation. In the field of biosorption technology for dyeing and printing wastewater, the key indicator determining the application value of biosorbent materials is their adsorption performance, which is affected by factors such as temperature, pH, dye concentration, and pretreatment methods of the adsorbent. Therefore, developing biosorbent materials that are adaptable to varying environments, possess high adsorption performance, and are cost-effective to prepare and use will contribute to the development of industrial-scale biosorption decolorization technology.

[0005] Studies have shown that extracellular polysaccharides (EPS) have certain flocculation and sedimentation effects and adsorption properties on harmful substances such as pigments, heavy metals, and suspended particles in dyeing and printing wastewater, and can be developed as adsorbents for wastewater treatment and other fields. EPS are water-soluble macromolecular sugars secreted by microorganisms outside the cell wall, including mucopolysaccharides secreted in the form of mucus and capsular polysaccharides attached to the surface of microbial cells. Although various EPS-based bioflocculants or adsorbents have been developed, and methods and technologies for dye decolorization exist, the currently developed EPS-based biosorbents have poor decolorization effects on dyeing and printing wastewater, and the low yield and high production cost of extracellular polysaccharides limit the large-scale application of EPS-based biosorbents. Therefore, it is necessary to find more efficient and lower-cost EPS-based biosorbents. Summary of the Invention

[0006] The purpose of this invention is to provide a capsule-producing Bacillus retroflexus R81 strain for decolorization of dyeing and printing wastewater, overcoming the factors that restrict its large-scale application, such as low EPS yield and high production cost.

[0007] This invention provides a strain of Bacillus retroflexus R81, which is deposited at the China Center for Type Culture Collection (CCTCC) with accession number CCTCC NO: M 20221010.

[0008] The present invention also provides the application of Bacillus retroflexus R81 described in the above technical solution in dye decolorization.

[0009] Preferably, the dye comprises anthraquinone dye.

[0010] The present invention also provides a dye adsorbent, said dye adsorbent comprising one or more of the following a) to d):

[0011] a) The *Bacillus lateralis* R81 described in the above technical solution;

[0012] b): Bacterial cells isolated from a fermentation culture containing Bacillus retroflexus R81 described in a);

[0013] c): Modified bacterial cells obtained by modifying the bacterial cells described in b);

[0014] d): Capsular polysaccharides isolated from the bacterial cells described in b) or the modified bacterial cells described in c).

[0015] Preferably, the bacterial cells are modified using pectinase; the modification treatment lasts for 2 hours at a temperature of 40°C.

[0016] The present invention also provides a method for decolorizing dyeing and printing wastewater, the method comprising the following steps: mixing the dye adsorbent described in the above technical solution with the dyeing and printing wastewater for decolorization.

[0017] Preferably, the volume ratio of the dye adsorbent to the dyeing wastewater is 1:5; the OD of the dye adsorbent... 600 It is 0.5.

[0018] Preferably, the decolorization time is 10-12 hours, the temperature is 30-35°C, and the rotation speed is 100-120 r / min.

[0019] Preferably, after decolorization, the process further includes a step of collecting the dye adsorbent for reuse.

[0020] Preferably, the collection step includes: settling the dye adsorbent, dissolving it, and obtaining a regenerated adsorbent;

[0021] The sedimentation method includes adjusting the pH of the decolorized mixture to 9-10.

[0022] Beneficial effects:

[0023] This invention collected sludge samples from the sewer and sewage outlet of a textile company's dyeing and printing workshop in Shandong Province and isolated a strain of *Bacillus laterosporus* R81, which has a capsule. This strain, its fermentation broth, and the bacterial cells and capsular polysaccharides isolated from the fermentation broth possess anthraquinone dye decolorization capabilities, and the decolorization effect can be further enhanced after modification of the bacterial cells. The results of the examples show that the molar ratio of each monosaccharide in the capsular polysaccharide of *Bacillus laterosporus* R81 described in this invention is D-galacturonic acid: galactose: fucose: D-mannose: D-mannuronic acid: xylose: glucose: L-guluronic acid = 27.7:13.3:6.09:3.16:2.26:1.34:1.08:0.98. This strain can adsorb anthraquinone dyes through capsular polysaccharides. After 48 hours of cultivation at an initial concentration of 200 mg / L Reactive Blue 19, the decolorization rate reached 86%, demonstrating a high decolorization capacity for anthraquinone dyes. Furthermore, the modification treatment endowed the strain with self-aggregation properties, enhancing its application effect in the decolorization of dyeing and printing wastewater.

[0024] Biological Preservation Information

[0025] Brevibacillus laterosporus R81 was deposited on July 4, 2022, at the China Center for Type Culture Collection (CCTCC), Wuhan University, Wuhan, China, 430072, China, with accession number CCTCCNO: M 20221010. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly described below.

[0027] Figure 1 The results of morphological observation of strain R81 are as follows: Figure 1 In the table, A represents the colony results from plate culture, B represents the Gram staining results, C represents the electron microscopy results, D represents the spore staining results, and E represents the capsule staining results.

[0028] Figure 2 Phylogenetic tree of Bacillus lateralis R81;

[0029] Figures 3-4 The results of the response surface optimization experimental design were analyzed for carbon source concentration, nitrogen source concentration, and temperature.

[0030] Figure 5 The results of PMP pre-column derivatization high performance liquid chromatography (external standard method) analysis of monosaccharide components of capsular polysaccharides of Bacillus laterosporus R81;

[0031] Figure 6The results of the adsorption kinetic analysis of the dye adsorption mechanism in Bacillus lateralis R81 cells;

[0032] Figure 7 The results of isotherm analysis of the dye adsorption mechanism of Bacillus laterosporus R81 cells;

[0033] Figure 8 The effect of pectinase treatment on pigment adsorption of Bacillus lateralis R81 cells;

[0034] Figure 9 The changes in Bacillus laterosporus R81 cells after pectinase treatment are shown in Figure A, where A is the electron microscopy result before pectinase treatment and B is the electron microscopy result after pectinase treatment.

[0035] Figure 10 The effect of different dosing methods on the adsorption of dye by Bacillus lateralis R81 cells. Detailed Implementation

[0036] This invention provides a strain of Bacillus laterosporus R81, which is deposited at the China Center for Type Culture Collection (CCTCC) with accession number CCTCC NO: M 20221010.

[0037]

[0038] The present invention also provides the application of Bacillus retroflexus R81 described in the above technical solution in dye decolorization.

[0039] In this invention, the dye preferably includes anthraquinone dyes, more preferably one or more of Alizarin red S, Disperse blue 56, Acid blue 80, Reactive blue 19, and Reactive blue 4, and more preferably Reactive blue 19.

[0040] The present invention also provides a dye adsorbent, wherein the dye adsorbent comprises one or more of the following a) to d):

[0041] a) The *Bacillus retroflexus* R81 described in the aforementioned technical solution;

[0042] b): Bacterial cells isolated from a fermentation culture containing Bacillus retroflexus R81 described in a);

[0043] c): Modified bacterial cells obtained by modifying the bacterial cells described in b);

[0044] d): Capsular polysaccharides isolated from the bacterial cells described in b) or the modified bacterial cells described in c).

[0045] In this invention, the method for preparing the fermentation culture containing Bacillus retroflexus R81 preferably includes the following steps:

[0046] Activated Bacillus laterosporus R81 was inoculated into a fermentation medium for fermentation culture to obtain a fermentation culture broth containing Bacillus laterosporus.

[0047] This invention involves activating Bacillus laterosporus R81 to obtain an activated culture medium of Bacillus laterosporus.

[0048] In this invention, the activation method preferably includes: placing Bacillus retroflexus R81 in an activation culture medium for activation culture to obtain Bacillus retroflexus activated culture solution.

[0049] In this invention, the activation culture medium preferably comprises 2% agar powder and the remainder being enrichment culture medium. The enrichment culture medium preferably comprises 50 mg Reactive Blue 19, 0.5 g NH4Cl, 50 g NaCl, and 1000 mL of an inorganic salt mixed solution. The pH of the enrichment culture medium is preferably 6.5–7.0. The inorganic salt mixed solution preferably comprises 0.2 g / L KH2PO4, 0.8 g / L Na2HPO4, 0.02 g / L MnSO4·H2O, 0.2 g / L MgSO4·7H2O, 0.2 g / L CaCl2, and the remainder being water. The pH of the inorganic salt mixed solution is preferably 7.0.

[0050] In this invention, the activation culture temperature is preferably 30-37°C, more preferably 30°C; the activation culture rotation speed is preferably 120-150 r / min, more preferably 120 r / min; and the activation culture time is preferably 18-48 h, more preferably 48 h.

[0051] After obtaining the activated culture medium of Bacillus laterosporus, the present invention preferably inoculates the activated culture medium of Bacillus laterosporus into a fermentation medium for fermentation culture to obtain a fermentation culture medium containing Bacillus laterosporus.

[0052] In this invention, the fermentation medium preferably comprises: a carbon source of 9 g / L to 21 g / L, a nitrogen source of 8 g / L to 10 g / L, 0.5 g NH4Cl, 50 g NaCl, and 1000 mL of inorganic salt solution. The concentration of the carbon source in the fermentation medium is preferably 9 g / L; the carbon source preferably includes one or more of glucose, lactose, maltose, sucrose, fructose, and citric acid, more preferably one or more of glucose, sucrose, and citric acid, and even more preferably glucose. The concentration of the nitrogen source in the fermentation medium is preferably 8 g / L; the nitrogen source preferably includes one or more of peptone, yeast extract, ammonium sulfate, ammonium chloride, and ammonium dihydrogen phosphate, more preferably peptone and / or ammonium chloride, and even more preferably peptone. The pH of the fermentation medium is preferably 6 to 9, more preferably 6 to 8, and even more preferably 7.

[0053] In this invention, the fermentation temperature is preferably 25-35°C, more preferably 30°C; the fermentation speed is preferably 120-200 r / min, more preferably 120-160 r / min, and more preferably 120 r / min; and the fermentation time is preferably 48-36 h, and more preferably 36 h.

[0054] The fermentation culture broth containing Bacillus laterosporus R81 obtained by the preparation method of the present invention contains a high density of Bacillus laterosporus R81. Bacillus laterosporus R81 has capsular polysaccharides that can decolorize dyes.

[0055] This invention isolates bacterial cells from a fermentation broth containing *Bacillus laterosporus* R81. Preferably, the method for preparing the bacterial cells includes centrifuging the fermentation broth, collecting the precipitate, and obtaining the bacterial cells. The centrifugation speed is preferably 8000 r / min, and the centrifugation time is preferably 20 min. This invention allows for direct decolorization of dyes by collecting bacterial cells from the fermentation broth, resulting in lower costs compared to preparing dye adsorbents using free extracellular polysaccharides.

[0056] This invention modifies the bacterial cells to obtain modified bacterial cells. Preferably, this invention utilizes pectinase to modify the bacterial cells; the modification treatment time is preferably 2 hours, and the temperature is preferably 40°C. The modification treatment method of this invention preferably includes: resuspending the bacterial cells in a phosphate buffer solution at pH 7.0 to obtain a bacterial suspension; mixing the bacterial suspension with pectinase, treating at 40°C for 2 hours, centrifuging, and collecting the precipitate, which is the modified bacterial cell. After modification, the intercellular adhesion of the bacterial cells is significantly improved. In the mixture of the bacterial suspension and the pectinase of this invention, the ratio of the effective viable count of *Bacillus laterosporus* R81 to the enzyme activity of pectinase is preferably 10. 10 CFU: 1000U; the preferred effective viable count of Bacillus retrosporum R81 in the bacterial suspension is 10. 10 cfu / mL. The capsular polysaccharide in the bacterial cells described in this invention is rich in galacturonic acid and has a pectin-like structural characteristic. Modifying the strain with pectinase can improve the decolorization effect of the strain cells and endow the strain with self-aggregating properties, thereby enhancing the application effect of the strain in the decolorization of dyeing and printing wastewater.

[0057] This invention relates to the isolation of capsular polysaccharides from the bacterial cells or modified bacterial cells. In this invention, the method for isolating the capsular polysaccharides preferably includes the following steps:

[0058] The bacterial cells or modified bacterial cells are mixed with SDS solution and cultured, and the first supernatant is collected.

[0059] Mix the first supernatant with trichloroacetic acid solution, stir, and collect the second supernatant;

[0060] The second supernatant was dialyzed, and the dialyzed solution was collected;

[0061] The dialyzed solution was mixed with anhydrous ethanol, allowed to stand, and the precipitate was collected; the precipitate contained the capsular polysaccharide.

[0062] In this invention, the bacterial cells or modified bacterial cells are mixed with an SDS solution and cultured, and the first supernatant is collected. In this invention, the SDS concentration in the SDS solution is preferably 2% by mass; the mass-to-volume ratio of the bacterial cells to the SDS solution is preferably 0.5 g: 100 mL; the preferred culture conditions are: 5–20 °C, 120 r / min shaking culture for 30 min. The preferred method for collecting the first supernatant is centrifugation; the preferred centrifugation speed is 8000 r / min; and the preferred centrifugation time is 20 min.

[0063] After obtaining the first supernatant, the present invention mixes the first supernatant with a trichloroacetic acid solution, stirs, and collects the second supernatant. In the present invention, the trichloroacetic acid content in the trichloroacetic acid solution is preferably 80% by mass and volume; the trichloroacetic acid content in the mixture of the first supernatant and the trichloroacetic acid solution is preferably 4% by mass and volume. The stirring time is preferably 2 hours. The stirring is preferably performed at room temperature. The second supernatant is preferably collected by centrifugation; the centrifugation speed is preferably 10000 r / min; the centrifugation time is preferably 45 minutes, and the temperature is preferably 4°C.

[0064] After obtaining the second supernatant, the present invention dialyzes the second supernatant and collects the dialyzed solution. Preferably, the dialysis in this invention uses a dialysis bag with a molecular weight cutoff of 14 kDa; the dialysis time is preferably 48 hours. Preferably, the dialysis fluid is changed every 8 hours during the dialysis process; the dialysis fluid is preferably distilled water. In this embodiment of the invention, the portion retained in the dialysis bag is collected, which is the dialyzed solution.

[0065] After obtaining the dialyzed solution, the present invention mixes the dialyzed solution with anhydrous ethanol, allows it to stand, and collects the precipitate; the precipitate contains the capsular polysaccharide. The preferred volume ratio of the dialyzed solution to anhydrous ethanol is 1:2; the preferred standing time is 12 hours, and the preferred temperature is 4°C. The preferred method for collecting the precipitate is centrifugation; the preferred centrifugation speed is 10000 r / min; the preferred centrifugation time is 45 minutes, and the preferred temperature for separating the capsular polysaccharide is 4°C.

[0066] The capsular polysaccharide isolated from the above-mentioned bacterial cells by this invention has a molar ratio of D-galacturonic acid:galactose:fucose:D-mannose:D-mannuronic acid:xylose:glucose:L-guluronic acid = 27.7:13.3:6.09:3.16:2.26:1.34:1.08:0.98, which can adsorb dyes in wastewater and achieve a decolorization effect.

[0067] Based on the fermentation culture broth described in this invention, the bacterial cells in the fermentation culture broth, the modified bacterial cells, and one or more of the capsular polysaccharides isolated from the bacterial cells or modified bacterial cells, the application in dye decolorization is also within the scope of protection of this invention. In this invention, the dye preferably includes anthraquinone dyes, more preferably Alizarin Red, Disperse Blue 56, Acid Blue 80, Reactive Blue 19, and Reactive Blue 4, and more preferably Reactive Blue 19.

[0068] The present invention also provides a method for decolorizing dyeing and printing wastewater, the method comprising the following steps: mixing the dye adsorbent described in the above technical solution with the dyeing and printing wastewater for decolorization.

[0069] In this invention, the preferred volume ratio of the dye adsorbent to the dyeing wastewater is 1:5; the OD of the dye adsorbent... 600 The pH value is preferably 0.5; the pH value of the dyeing and printing wastewater is preferably 3 to 4.

[0070] In this invention, the decolorization time is preferably 10-12 hours; the decolorization temperature is preferably 30-35°C, more preferably 32°C; and the decolorization speed is preferably 100-120 r / min, more preferably 110 r / min.

[0071] In this invention, after decolorization, the mixture is preferably left to stand for 1-2 hours, and the pH of the resulting mixture is adjusted to 9-10 to obtain the settled dye adsorbent. This invention preferably uses NaOH to adjust the pH.

[0072] After obtaining the settled dye adsorbent, the present invention preferably uses a phosphate buffer solution to dissolve the settled dye adsorbent to obtain a regenerated adsorbent. In the present invention, the pH value of the phosphate buffer solution is preferably 3-4; the mass-to-volume ratio of the settled dye adsorbent to the phosphate buffer solution is preferably 1g:2mL. The regenerated adsorbent of the present invention can decolorize dyeing and printing wastewater, realizing the reuse of the dye adsorbent. In the present invention, the dye adsorbent is preferably reused 8-10 times. Example results show that bacterial cells that have adsorbed RB19 can desorb the adsorbed RB19 after being treated with 0.5mol / L NaOH solution for 6 hours, and the desorbed bacterial cells have the ability to adsorb RB19 again.

[0073] To further illustrate the present invention, the following detailed description, in conjunction with the accompanying drawings and embodiments, describes a Bacillus lateralis R81 strain that produces capsular polysaccharides and its application in dye decolorization, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0074] Example 1

[0075] 1.1 Test Materials

[0076] The culture medium used in the embodiments of this invention is as follows:

[0077] (1) Inorganic salt mixed solution: 0.2g / L KH2PO4, 0.8g / L Na2HPO4, 0.02g / L MnSO4·H2O, 0.2g / L MgSO4·7H2O, 0.2g / L CaCl2. Nutrients can be added later to adjust the pH to 7.0.

[0078] (2) Enrichment medium: Dissolve 50mg Active Blue 19, 0.5g NH4Cl, 50g NaCl in 1000mL of inorganic salt mixed solution, pH 6.5~7.0, autoclave at 121℃ for 20min.

[0079] (3) Isolation medium: 2% agar powder plus enrichment medium, autoclave at 121℃ for 20 min.

[0080] (4) Slant culture medium: Nutrient broth (NB) medium.

[0081] (5) Seed culture medium: 50mg Active Blue 19, 0.5g NH4Cl, 10g NaCl, dissolved in 1000mL inorganic salt solution, pH 7.0, autoclaved at 121℃ for 20min.

[0082] (6) Decolorizing medium: Dissolve 100mg Active Blue 19, 0.5g NH4Cl, 50g NaCl in 1000mL inorganic salt solution, pH 7.0, autoclave at 121℃ for 20min.

[0083] The main instruments and equipment used in the embodiments of the present invention are shown in Table 1 below. In addition, common laboratory consumables such as centrifuge tubes and Erlenmeyer flasks were also used in the experiment.

[0084] Table 1 Experimental Instruments and Models

[0085]

[0086] 1.2 Isolation and Identification of Bacillus Laterosporus R81

[0087] (1) Strain isolation

[0088] Sludge samples were collected from the sewer system of the dyeing and printing workshop and the sewage outlet of the wastewater treatment workshop of a textile company in Shandong. 1g of sludge sample was mixed with a small amount of sterile water, and then 5mL of the water sample was added to a 250mL Erlenmeyer flask containing 50mL of enrichment medium. The flask was incubated at 30℃ and 150rpm for 96 hours (at least three replicates per sludge sample). During this period, 1mL of the enrichment solution was collected every 24 hours and the bacterial strains were isolated using a serial dilution-spreading method on an isolation medium. A dilution of 10-1 was selected.-1 10 -2 10 -3 10 -4 and 10 -5 The enriched solutions were spread onto isolation media and incubated upside down at 25°C for 24–48 h. Colonies with a clear zone were selected and isolated and purified by streak plating. Twelve single colonies from the purified strain were transferred to slant agar (numbered DC1–12) and incubated at 25°C for 24 h, then stored at 4°C for later use.

[0089] Strains DC1-12, stored at 4℃, were activated and cultured on isolation medium. Single colonies were then picked and inoculated into 15mL test tubes containing 5mL of decolorizing medium. Undyed decolorizing medium served as a negative control (machine zeroed), and no bacterial cells were added as a blank control (A0). Seed culture was prepared by shaking at 25℃ and 150 rpm for 24 hours. Then, the seed culture was inoculated at 2% of the culture into 15mL / 50mL Erlenmeyer flasks of decolorizing medium and cultured at 30℃ and 120 rpm for 48 hours. After 48 hours of culture, the cultures of each strain were centrifuged at 8000 rpm, and the supernatant was collected. The decolorization rate was calculated using a spectrophotometer according to the following formula. The results are shown in Table 2.

[0090]

[0091] A t A0 is the absorbance of the culture medium at a characteristic wavelength after 48 hours of incubation (t); A0 is the absorbance of the culture medium at a characteristic wavelength at t=0. The characteristic wavelength of Active Blue 19 is 585 nm.

[0092] Table 2. Decolorization of Reactive Blue 19 by strains DC1-12 after 48 hours of degradation.

[0093]

[0094]

[0095] As shown in Table 2, among the 12 strains screened in the early stage, strain DC1 had the best decolorization effect on Reactive Blue 19, and it was named R81.

[0096] (2) Morphological identification

[0097] The R81 cells obtained in step (1) were inoculated into isolation medium and cultured at 30℃ and 120 r / min for 12 h. The morphology of the cells was observed using scanning electron microscopy, and Gram staining, capsule staining, and spore staining were performed for microscopic observation of the bacterial cells. The results are as follows: Figure 1 Middle A~E.

[0098] As shown in Figures A-E, strain R81 colonies are round, flat, with a central protrusion, irregular edges with many notches, milky white in color, glossy, opaque, and easily picked up when dry. Gram staining for microscopic observation of the bacterial cells reveals short, stout rod-shaped, Gram-positive cells. Spore staining indicates that it produces spores, consistent with the morphological characteristics of *Bacillus laterosporus*. Capsule staining shows the presence of a capsule on the bacterial cell surface.

[0099] (3) Physiological and biochemical identification

[0100] Based on the analysis of the physiological and biochemical characteristics of strain R81 in Bergey's Manual of Systematic Bacteriology, the results showed that the strain was nitrate-reducing positive, gelatinase positive, and urease negative, which is consistent with the physiological and biochemical characteristics of Bacillus laterosporus.

[0101] (4) Molecular biological identification

[0102] Genomic DNA was extracted from strain R81 using a genomic DNA extraction kit. PCR amplification was performed using universal primers 27-f (SEQ ID NO.2: 5′-AGAGTTTGATCCTGGCTCAG-3′) and 1492-r (SEQ ID NO.3: 5′-GGTTACCTTGTTACGACTT-3′) for bacterial 16S rRNA. The amplified products were sent to Anhui Bioengineering Technology Co., Ltd. for sequencing, yielding the nucleotide sequence as described in SEQ ID NO.1. Blast homology analysis was performed on the obtained 16S rRNA gene partial sequence. High homology sequences were selected, and a phylogenetic tree was constructed using the neighbor-joining method with MEGA 4.0 software. Bootstrap value analysis was performed after 1000 repeated sampling to assess the confidence level of the phylogenetic tree and determine the evolutionary position of the strain. The phylogenetic tree of strain R81 is as follows: Figure 2 As shown. According to Figure 2 It can be seen that strain R81 is most closely related to Bacillus laterosporus, and therefore strain R81 is identified as belonging to Bacillus laterosporus, named Bacillus laterosporus R81, and deposited on July 4, 2022 at the China Center for Type Culture Collection (CCTCC), address: Wuhan University, Wuhan, China, postcode: 430072, accession number: CCTCC NO: M 20221010.

[0103] 1.3 Broad-spectrum decolorization analysis of Bacillus laterosporus R81

[0104] (1) Preparation of decolorizing medium containing different dyes: Based on the decolorizing medium in step 1.1, replace Reactive Blue 19 with any one of Disperse Blue 56, Reactive Blue 4, Acid Blue 80, Alizarin Red and Eosin Y to prepare a decolorizing medium with Disperse Blue 56, Reactive Blue 4, Acid Blue 80, Eosin Y and Alizarin Red as the only carbon source.

[0105] (2) Take strain R81 stored at 4℃, activate it in isolation medium, inoculate it into seed medium, and shake it at 25℃ and 150r / min for 24h to prepare seed liquid. Then, transfer it to the above decolorization medium with different dyes as the only carbon source at an inoculation amount of 2% (v / v). Repeat the operation 3 times, which are recorded as replicate 1, replicate 2 and replicate 3 respectively. Use a blank medium without inoculation as control group (A0). Shake it at 25℃ and 150r / min for 24h. Then, centrifuge at 8000r / min for 15min and take the supernatant. Decolorization rate is determined according to step 1.2. The results are shown in Table 3 below.

[0106] Table 3. Decolorization effect of Bacillus laterosporus R81 on different dyes.

[0107]

[0108] As can be seen from Table 3, the *Bacillus lateralis* R81 of this invention has a decolorizing effect on a variety of dyes, especially alizarin red, disperse blue 56 and acid blue 80, and has a broad-spectrum decolorizing effect.

[0109] 1.4 Effects of different carbon sources on the decolorization effect of Bacillus lateralis R81

[0110] (1) Preparation of decolorizing culture medium containing different carbon sources: Based on the decolorizing culture medium in step 1.1, glucose, lactose, maltose, sucrose, fructose, citric acid and sodium acetate were added to the decolorizing culture medium at a concentration of 10 g / L to prepare selective culture medium containing different carbon sources.

[0111] (2) Strain R81, stored at 4℃, was activated and cultured in isolation medium, then inoculated into seed culture medium. Seed culture was prepared by shaking at 25℃ and 150 rpm for 24 h. Then, 1 mL of seed culture was pipetted into a 50 mL Erlenmeyer flask (containing 20 mL of selective culture medium, i.e., 5% inoculation). This process was repeated twice, for a total of three times, designated as Replication 1, Replication 2, and Replication 3. A blank culture medium without inoculation was used as the control group (A0). All samples were placed in a 30℃, 120 rpm shaking incubator for 48 h. After 48 h, the samples were removed and centrifuged at 10000 rpm for 10 min. The supernatant was collected, and its OD value was measured. 585The decolorization rate was determined according to step 1.2, and the results are shown in Table 4 below.

[0112] Table 4. Effects of different carbon sources on the decolorization effect of Bacillus retrosporum R81

[0113]

[0114] As shown in Table 4, glucose is the optimal carbon source for the fermentation of Bacillus lateralis R81.

[0115] 1.5 Effects of different nitrogen sources on the decolorization effect of Bacillus lateralis R81

[0116] (1) Preparation of decolorizing medium containing different nitrogen sources: Based on the decolorizing medium in step 1.1, 10 g / L glucose was used as an additional carbon source, and peptone, urea, yeast extract, ammonium sulfate, ammonium chloride and ammonium dihydrogen phosphate were used as additional nitrogen sources respectively. The additional nitrogen sources were added to the decolorizing medium at a concentration of 8 g / L to prepare selective medium containing different nitrogen sources.

[0117] (2) Same as step 1.4 (2), except that the selective medium composed of different carbon sources is replaced with a selective medium composed of different nitrogen sources. The decolorization effect is shown in Table 5 below.

[0118] Table 5. Effects of different nitrogen sources on the decolorization effect of Bacillus retrosporum R81

[0119]

[0120] As can be seen from Table 5, peptone is the optimal carbon source for the fermentation of Bacillus retroflexus R81.

[0121] 1.6 Effect of different pH values ​​on the decolorization effect of Bacillus laterosporus R81

[0122] (1) Preparation of decolorizing medium at different pH: Based on the decolorizing medium in step 1.1, glucose was added as an additional carbon source and peptone was added as an additional nitrogen source, so that the concentrations of glucose and peptone were 10 g / L and 8 g / L respectively, and the pH was adjusted to 5, 6, 7, 8 and 9.

[0123] (2) Same as step 1.4 (2), except that the decolorizing medium composed of different carbon sources is replaced with a decolorizing medium of different pH. The decolorization effect is shown in Table 6 below.

[0124] Table 6. Effects of different pH values ​​on the decolorization effect of Bacillus retrosporum R81

[0125]

[0126] As shown in Table 6, Bacillus lateralis R81 has a good decolorization effect under pH conditions of 6–9.

[0127] 1.7 Effect of different temperatures on the decolorization effect of Bacillus laterosporus R81

[0128] (1) Preparation of decolorizing medium: Based on the decolorizing medium in step 1.1, 10 g / L glucose was used as an additional carbon source and 8 g / L peptone was used as an additional nitrogen source. The pH was adjusted to 7 to obtain the decolorizing medium.

[0129] (2) Same as step 1.4 (2), except that 1 mL of seed culture is inoculated into a 50 mL Erlenmeyer flask (the Erlenmeyer flask contains 20 mL of the decolorizing medium from step 1.7 (1)) using a pipette. The operation is repeated twice, for a total of 3 times, and is recorded as repeat 1, repeat 2 and repeat 3 in sequence. A blank medium without inoculation is used as the control group (A0). The medium is cultured at temperatures of 20℃, 25℃, 30℃ and 35℃ respectively, and the culture speed is 120 rpm. The final decolorization effect is shown in Table 7 below.

[0130] Table 7. Effects of different temperatures on the decolorization effect of Bacillus retrosporum R81

[0131]

[0132]

[0133] As shown in Table 7, Bacillus retroflexus R81 has a good decolorization effect at 30-35℃, and the optimal fermentation temperature is 30℃.

[0134] 1.8 Effect of different rotation speeds on the decolorization effect of Bacillus lateralis R81

[0135] (1) Preparation of decolorizing medium: Based on the decolorizing medium in step 1.1, 10 g / L glucose was used as an additional carbon source and 8 g / L peptone was used as an additional nitrogen source. The pH was adjusted to 7 to obtain the decolorizing medium.

[0136] (2) Same as step 1.4 (2), except that 1 mL of seed culture is inoculated into a 50 mL Erlenmeyer flask (the Erlenmeyer flask contains 20 mL of the decolorizing medium from step 1.7 (1)) using a pipette. The operation is repeated twice, for a total of 3 times, and is recorded as repeat 1, repeat 2 and repeat 3 in sequence. A blank medium without inoculation is used as the control group (A0). The culture is carried out at rotation speeds of 80 rpm, 120 rpm, 160 rpm and 200 rpm respectively. The culture temperature is 30℃. The final decolorization effect is shown in Table 8 below.

[0137] Table 8. Effects of different rotation speeds on the decolorization effect of Bacillus retrosporum R81

[0138]

[0139]

[0140] As shown in Table 8, Bacillus retrospora R81 has a good decolorization effect under the condition of 120-200 r / min, and the optimal culture speed is 120 r / min.

[0141] 1.9 Response Surface Optimization Experiment

[0142] (1) Based on the conclusions of steps 1.4 to 1.8, a response surface methodology was used to optimize the carbon source concentration, nitrogen source concentration, and temperature. Specifically, based on the decolorized medium in step 1.1, glucose was used as an additional carbon source and peptone as a nitrogen source. The medium consisted of glucose, peptone, 100 mg Reactive Blue 19, 0.5 g NH4Cl, 50 g NaCl, and 1000 mL of a mixed organic salt solution (0.2 g / L KH2PO4, 0.8 g / L Na2HPO4, 0.02 g / L MnSO4·H2O, 0.2 g / L MgSO4·7H2O, 0.2 g / L CaCl2, adjusted to pH 7.0). Three replicates were set up for the experimental treatment, which were designated as replicate 1, replicate 2, and replicate 3, respectively. One uninoculated culture was used as the control group A0. 20 mL of culture medium was prepared in a 50 mL Erlenmeyer flask. Using a pipette, inoculate 1 mL of the seed culture from step 1.4 into the culture medium and incubate in a shaking incubator at 120 rpm for 48 h. After 48 h, remove the incubator and centrifuge at 10000 rpm for 10 min. Collect the supernatant and measure its OD value. 585 The decolorization rate of the strain at different temperatures was calculated, with specific glucose concentration, peptone concentration, and temperature parameters. The decolorization results are shown in Table 9 below. Figures 3-4 .

[0143] Table 9. Decolorization effect of Bacillus retroflexus R81 with different combinations of carbon source concentration, nitrogen source concentration, and temperature.

[0144]

[0145] Note: OD in the table 585 This is the average of the three sets of data.

[0146] According to Table 9 and Figures 3-4It can be seen that the optimal glucose concentration is 9 g / L, the optimal peptone concentration is 8 g / L, and the optimal culture temperature is 30℃. In summary, *Bacillus laterosporus* R81 showed the best decolorization effect under the following decolorization medium and culture conditions: 9 g / L glucose, 8 g / L peptone, 100 mg Reactive Blue 19, 0.5 g NH4Cl, 50 g NaCl, dissolved in 1000 mL of inorganic salt solution, pH 7.0, autoclaved at 121℃ for 20 min; culture conditions: 30℃, 120 rpm shaking incubator for 48 h.

[0147] Example 2

[0148] 1.1 Preparation of Bacillus laterosporus R81 cell-type EPS biosorbent

[0149] Strawberry strain R81, preserved at 4℃, was streaked onto LB agar plates and cultured overnight. Single colonies were then inoculated into 50mL / 250mL Erlenmeyer flasks in decolorized medium (9g / L glucose, 8g / L peptone, 0.5g NH4Cl, 50g NaCl, dissolved in 1000mL inorganic salt solution, pH 7.0, autoclaved at 121℃ for 20min). Seed culture was prepared by shaking and culturing at 30℃ and 150rpm for 24h. Then, the seed culture was inoculated at 2% in 50mL Erlenmeyer flasks containing 15mL of isolation medium (specific composition as shown in Example 1). After shaking and culturing at 30℃ and 120rpm for 48h, the bacterial pellet was collected by centrifugation at 8000rpm for 15min. The pellet was resuspended in phosphate buffer (pH 7.0) to prepare a cell concentration of 102. 10 Cellular EPS biosorbent with cfu / mL.

[0150] 1.2 Preparation of capsular polysaccharide from Bacillus laterosporus R81

[0151] (1) The activated Bacillus laterosporus R81 was inoculated at a rate of 2% into the optimized culture medium (9 g / L glucose, 8 g / L peptone, 0.5 g NH4Cl, 50 g NaCl, dissolved in 1000 mL inorganic salt solution, pH 7.0, autoclaved at 121℃ for 20 min), and cultured at 30℃ and 120 r / min for 36 h. The cells were then obtained by centrifugation at 8000 r / min for 20 min.

[0152] (2) Add 100 mL of 2% SDS solution to the bacterial cells from step (1), and shake at 120 r / min for 30 min. Centrifuge at 8000 r / min for 20 min, add 80% (m / v) trichloroacetic acid (TCA) solution to the supernatant to a final concentration of 4% (m / v), stir at room temperature for 2 h, centrifuge at 10000 r / min at 4℃ for 45 min, and put the supernatant into a dialysis bag with a molecular cutoff of 14 kDa for dialysis for 48 h, changing the distilled water every 8 h. Take the dialysis solution, add twice the volume of anhydrous ethanol, refrigerate at 4℃ for 12 h, and centrifuge at 10000 r / min at 4℃ for 45 min. Dissolve the precipitate in distilled water to obtain crude polysaccharide of Bacillus laterosporus R81;

[0153] (3) Purification of capsular polysaccharides by anion exchange chromatography: DEAE cellulose DE-52 ion exchange gel was loaded into the chromatography column, and the column was equilibrated with Na2HPO4-NaH2PO4 buffer (0.05 mol / L, pH=7). 2 mL of the crude polysaccharide solution from step (2) was loaded each time, and eluted sequentially with elution buffer and Na2HPO4-NaH2PO4 buffer containing 0.05, 0.1, 0.2 and 0.3 mol / L NaCl. The flow rate was 3 mL / min, and 9 mL was collected per tube, with 3 tubes collected for each gradient. After dialysis for 48 h using a dialysis bag with a cutoff of 14 kDa, capsular polysaccharide samples of Bacillus laterosporus R81 were obtained.

[0154] (4) The polysaccharide sample of Bacillus retrosporus R81 obtained in step (3) was acid-hydrolyzed, and the monosaccharide composition was analyzed by PMP pre-column derivatization high-performance liquid chromatography (Dai Jun, Zhu Song, Tang Jian, et al. Analysis of monosaccharide composition of Dunaliella salina polysaccharide by PMP pre-column derivatization high-performance liquid chromatography [J]. Journal of Analytical Testing, 2007(02):206-210.). The results are as follows. Figure 5 As shown.

[0155] according to Figure 5 It can be seen that the capsular polysaccharide of Bacillus laterosporus R81 is rich in D-galacturonic acid, which is the same as the main component of plant pectin. Specifically, it is composed of D-galacturonic acid, galactose, fucose, D-mannose, D-mannuronic acid, xylose, glucose, and L-guluronic acid. The molar ratio of each monosaccharide is D-galacturonic acid: galactose: fucose: D-mannose: D-mannuronic acid: xylose: glucose: L-guluronic acid = 27.7: 13.3: 6.09: 3.16: 2.26: 1.34: 1.08: 0.98.

[0156] Example 3

[0157] Analysis of the dye adsorption mechanism of Bacillus lateralis R81

[0158] 1.1 Adsorption Kinetics Analysis

[0159] The bacterial suspension obtained in Example 2 was added to a 250 mL Erlenmeyer flask containing 50 mL of 50 mg / mL Reactive Blue 19 dyeing wastewater. The experiment was repeated 3 times, and the solution was shaken in a shaker at 30 °C and 150 r / min. The decolorization rate was measured every 12 h. The results are shown in Table 11.

[0160] Table 11 Decolorization effect of Bacillus lateralis R81 suspension at different treatment times

[0161]

[0162] The obtained decolorization rate data were used to establish pseudo-first- and second-order kinetic models using Sigma Plot for Windows Version 10.0 (SystatSoftware, San Jose, CA, US). The results are as follows: Figure 6 .

[0163] According to Table 11 and Figure 6 It can be seen that both the pseudo-first-order and pseudo-second-order kinetic models can describe the dye removal well, indicating the existence of chemisorption kinetics in the decolorization process. For induced cells, the pseudo-second-order kinetic model is slightly better than the pseudo-first-order kinetic model, while for non-induced cells, the pseudo-first-order kinetic model is slightly better than the pseudo-second-order kinetic model. This may be because the pseudo-first-order kinetic model is more suitable for the initial stage of adsorption, while the pseudo-second-order kinetic model is more suitable for long-term adsorption processes.

[0164] (2) Isotherm analysis

[0165] The bacterial suspension obtained in Example 2 was added to a 250 mL Erlenmeyer flask containing 50 mL of Reactive Blue 19 dyeing and printing wastewater with different initial concentrations (50, 100, 200, 400, 600, 800, 1000, 1200, 1500 mg / L). The experiment was repeated three times. The flask was shaken at 30℃ and 150 r / min. The decolorization rate was measured after 48 h. The results are shown in Table 12.

[0166] Table 12 Decolorization effect of Bacillus lateralis R81 suspension at different Reactive Blue 19 concentrations

[0167]

[0168]

[0169] The obtained decolorization rate data were analyzed for adsorption kinetics using the Pseudo-first-order model and the Pseudo-second-order model. The results are as follows: Figure 7 middle.

[0170] According to Table 12 and Figure 7 It can be seen that the decolorization equilibrium data of R81 cells fit the Langmuir model better. The applicability of the Langmuir model indicates that RB19 is adsorbed onto the surface of R81 cells as a monolayer and exhibits chemisorption. Electron microscopy images also indirectly prove that high concentrations of RB19 do not deform the cells, but only increase their density.

[0171] Example 4

[0172] 1. Modification treatment of Bacillus laterosporus R81

[0173] Bacillus retroflexus R81, preserved on 4℃ slant agar plates, was streaked onto LB agar and incubated overnight. Single colonies were then inoculated into a preferred decolorized medium (9 g / L glucose, 8 g / L peptone, 0.5 g NH4Cl, 50 g NaCl, dissolved in 1000 mL inorganic salt solution, pH 7.0, autoclaved at 121℃ for 20 min) in 50 mL / 250 mL Erlenmeyer flasks and cultured with shaking at 30℃ and 150 rpm for 24 h to prepare a seed culture. Then, the seed culture was inoculated at a 2% inoculation rate into a 15 mL / 50 mL Erlenmeyer flask and cultured with shaking at 30℃ and 120 rpm for 48 h. The bacterial pellet was collected by centrifugation at 8000 rpm for 15 min and resuspended in phosphate buffer (pH 7.0) to prepare a cell concentration of 102. 10 The bacterial suspension was prepared by adding pectinase to a final concentration of 1000 U / mL and treating it at 40°C for 2 hours. The pectinase-treated bacterial suspension was then autoclaved at 115°C for 15 minutes to obtain the R81 bacterial dye adsorbent.

[0174] (1) Unmodified Bacillus laterosporus brevis suspension and modified Bacillus laterosporus suspension were mixed with equal volumes of 100 mg / L RB19 and allowed to stand at 30℃ for 1–2 h. The effect of modification on Bacillus laterosporus brevis suspension was observed. The results are as follows: Figure 8 As shown.

[0175] according to Figure 8 It can be seen that the modification of strain R81 cells with pectinase enhances the adsorption of Active Blue 19, and the cells exhibit self-aggregation or flocculation.

[0176] (2) Scanning electron microscopy was used to observe unmodified Bacillus laterosporus R81 and modified Bacillus laterosporus R81. The results are as follows: Figure 9 As shown.

[0177] according to Figure 9 It can be seen that the three-dimensionality of the bacterial cells was significantly reduced after treatment, and the cells aggregated into a sheet-like structure. This indicates that the negative charge of the bacterial capsule polysaccharide was weakened after pectinase treatment, and intercellular aggregation occurred. This is also consistent with... Figure 8 This corresponds to the phenomenon in the middle.

[0178] 2. Adsorption effect of R81 bacterial dye adsorbent:

[0179] The R81 bacterial dye adsorbent obtained in step 1 was added in batches or all at once to anthraquinone dyeing wastewater with an initial pigment concentration of 100 mg / L. The batch or all-time addition steps are as follows:

[0180] One-time addition: Add 4 mL of R81 bacterial dye adsorbent to 20 mL of anthraquinone dyeing wastewater with an initial pigment concentration of 100 mg / L;

[0181] Add in batches: Take 1 mL of R81 bacterial dye adsorbent + 3 mL of water and add it to 20 mL of anthraquinone dyeing wastewater with an initial pigment concentration of 100 mg / L. Then add 1 mL of centrifuged R81 bacterial dye adsorbent every 12 h.

[0182] The decolorization rate was calculated every 12 hours, and the results are shown in Tables 13-14 below. Figure 10 .

[0183] Table 13 Effect of a single application on dye adsorption by strain R81

[0184]

[0185]

[0186] Table 14 Effect of batch addition on dye adsorption by strain R81

[0187]

[0188]

[0189] According to Tables 13-14 and Figure 10 It can be seen that, whether added at once or in batches, the decolorization rate of anthraquinone dye reaches 75% after 24 hours, and the Bacillus lateralis R81 of this invention has a good dye decolorization effect.

[0190] As can be seen from the above, the *Bacillus lateralis* R81 of this invention has a decolorizing effect on a variety of dyes, especially alizarin red, disperse blue 56 and acid blue 80, and has a broad-spectrum decolorizing effect.

[0191] Example 5

[0192] A method for decolorizing dyeing and printing wastewater, the process is as follows:

[0193] 300-350L of pretreated dyeing and printing wastewater (pH 3-4) is injected into the adsorption tank, and then R81 bacterial dye adsorbent (OD) is added. 600nm =0.5) with 1:5 (V 吸附剂 :V 印染废水 The sample was added to the adsorption tank and adsorbed and decolorized at 30–35℃ and 100–120 r / min for 10–12 hours with stirring. Stirring was stopped after decolorization was completed. The dyeing and printing wastewater being treated was acidic wastewater (pH 3–4) with a reactive blue concentration of 1980–100 mg / L. After treatment, the reactive blue concentration in the wastewater was reduced to 10–20 mg / L.

[0194] Example 6

[0195] The process for reusing R81 bacterial dye adsorbent is as follows:

[0196] (1) After decolorization in Example 5, the adsorbent was allowed to stand for 1-2 hours to settle. 50-60 L of adsorbent settled at the bottom of the adsorption tank was pumped into the desorption tank using a water pump. NaOH was then added to the adsorption tank while stirring at 100-120 r / min until the pH reached 9-10. The addition of NaOH was stopped, and stirring was continued for 3-4 hours. The adsorbent was then allowed to stand for 1-2 hours until it had settled completely. The supernatant containing dye was recovered, and the settled adsorbent was allowed to enter the regeneration tank by gravity. Twice the volume of pH 3-4 phosphate buffer solution was added to the regeneration tank, and the mixture was stirred at 100-120 r / min for 3-4 hours. The resulting mixture was the regenerated adsorbent, which was then added to the next batch of dyeing and printing wastewater for decolorization.

[0197] (2) Repeat step (1) 7 to 9 times, that is, the R81 bacterial dye adsorbent is recycled 8 to 10 times. The decolorization effect on wastewater each time is shown in Table 15.

[0198] Table 15. Recycling effect of R81 bacterial cell dye adsorbent

[0199]

[0200]

[0201] As can be seen from Table 10, the R81 bacterial dye adsorbent provided by the present invention can be recycled, and the decolorization rate can still reach 43.79% after 10 recycling cycles.

[0202] As can be seen from the above, the *Bacillus laterosporus* provided by this invention can adsorb anthraquinone dyes through capsular polysaccharides, exhibiting excellent dye decolorization ability, good reusability, and dye recyclability. Furthermore, modifying *Bacillus laterosporus* R81 cells with pectinase enhances the cell's self-aggregation properties.

[0203] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A strain of Bacillus laterosporus ( Brevibacillus laterosporus R81, the Bacillus retroflexus R81, is deposited at the China Center for Type Culture Collection, with accession number CCTCCNO: M20221010.

2. The application of Bacillus retroflexus R81 as described in claim 1 in dye decolorization; The dye is one or more of Alizarin Red, Disperse Blue 56, Acid Blue 80, Reactive Blue 19, and Reactive Blue 4.

3. A dye adsorbent, characterized in that, The dye adsorbent includes one or more of the following a) to d): a): Bacillus retroflexus R81 as described in claim 1; b): Fermentation culture containing Bacillus retroflexus R81 described in a) or bacterial cells isolated from fermentation culture containing Bacillus retroflexus R81 described in a); c): Modified bacterial cells obtained by modifying the bacterial cells described in b) using pectinase; The modification treatment lasted for 2 hours at a temperature of 40°C. d): Capsular polysaccharides isolated from the bacterial cells described in b) or the modified bacterial cells described in c).

4. A method for decolorizing dyeing and printing wastewater, characterized in that, The decolorization method includes the following steps: mixing the dye adsorbent according to claim 3 with dyeing and printing wastewater for decolorization.

5. The decolorization method according to claim 4, characterized in that, The volume ratio of the dye adsorbent to the dyeing wastewater is 1:5; the OD of the dye adsorbent... 600 It is 0.

5.

6. The decolorization method according to claim 4, characterized in that, The decolorization time is 10-12 hours, the temperature is 30-35℃, and the rotation speed is 100-120 r / min.

7. The decolorization method according to claim 6, characterized in that, After decolorization, the process also includes a step of collecting the dye adsorbent for reuse.

8. The decolorization method according to claim 7, characterized in that, The collection steps include: settling the dye adsorbent, dissolving it, and obtaining a regenerated adsorbent; the settling method includes adjusting the pH of the decolorized mixture to 9-10.

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