Dye degradation system and method using rice straw as carbon source

Abstract

The application discloses a dye degradation system and method with rice straw as a carbon source, and belongs to the technical field of wastewater treatment. The application successfully constructs an economical combined degradation system by combining the ability of white rot fungi to decompose macromolecular organic matter and the characteristics of the power generation microorganism MR-1 to degrade pollutants in a broad spectrum and efficiently. The system uses rice straw as a carbon source, uses white rot fungi to degrade the rice straw, obtains a degraded straw solution, and then uses the power generation microorganism MR-1 to perform anaerobic respiratory metabolism on the degraded straw solution, releases electrons, and transmits the electrons to dye pollutants, so as to degrade dye wastewater. The combined degradation system can not only make up for the deficiency of the power generation microorganism MR-1 in utilizing macromolecular organic matter carbon sources, but also can significantly reduce the cost of carbon sources, and simultaneously realize the dual goals of wastewater treatment and solid waste resource utilization. The method is environmentally friendly, treats waste with waste, and has potential to be popularized and applied in practical application.

Description

TECHNICAL FIELD

[0001] The application relates to a dye degradation system and method taking rice straw as a carbon source, and belongs to the technical field of wastewater treatment. BACKGROUND

[0002] The biological method is considered as the most promising dye wastewater treatment technology due to low cost, environmental friendliness and simple operation, but the current biological treatment technology mainly relies on microbial enzyme catalysis to degrade organic dyes, has specificity, and is difficult to adapt to various dyes, and thus has poor effect.

[0003] The electrogenic microorganism is different from ordinary microorganisms, can degrade various types of dyes, has broad spectrum, and thus is high in efficiency and popular, and mainly relies on the electrons released into the environment in the anaerobic respiratory metabolism process to degrade pollutants.

[0004] Therefore, if the carbon source cost of the electrogenic microorganism pollution remediation can be reduced, the dye wastewater treatment difficulty problem can be solved, and the practical application of the electrogenic microorganism in the water environment remediation field can be promoted. SUMMARY

[0005] In view of some defects in the prior art, the application provides a dye degradation system and method taking rice straw as a carbon source, and particularly relates to a degradation system taking rice straw as a carbon source and using electrogenic microorganisms and fungi in combination and a dye degradation method.

[0006] To achieve the above technical purpose, the technical scheme adopted by the application is as follows:

[0007] The application first provides a dye degradation system taking rice straw as a carbon source, the system comprising white rot fungi and electrogenic microorganism MR-1, and the system taking rice straw as a carbon source.

[0008] The application further provides a dye degradation method taking rice straw as a carbon source, the method comprising:

[0009] The white rot fungi are cultured in a PDB culture medium to form fungal pellets, the white rot fungi pellets are added into a mineral salt culture medium containing rice straw to obtain a degraded straw solution; the degraded straw solution, a bacterial solution of the electrogenic microorganism MR-1 and dye pollutants are mixed, and the mixed solution is placed in a shaking table under anaerobic conditions to fully react to degrade the dyes.

[0010] Further, the degradation reaction condition of the rice straw is that the reaction temperature is 30±0.5℃, and the shaking table rotation speed is 200±5rpm; the bacteria solution of the electricity-producing microorganism MR-1 is obtained by resuspension of the mineral salt medium without carbon source; the mineral salt medium does not contain carbon source; the concentration of the bacteria solution of the electricity-producing microorganism MR-1 is 4-6×10 8 CFU / mL; and the concentration of the rice straw in the mineral salt medium containing rice straw is 100mg / L.

[0011] The formula of the mineral salt medium is as follows: 0.3g NaOH, 1.4977g NH4Cl, 0.097g KCl, 0.6708g NaH2PO4, 5.844g NaCl, 1mL of vitamin mother liquor, 1mL of amino acid mother liquor, and 1mL of trace element mother liquor are contained in each liter of the medium, and no lactic acid carbon source is contained.

[0012] Specifically, the preparation of the white rot fungus small ball includes:

[0013] First, the white rot fungus is inoculated on the PDA medium, and is placed in an incubator at 30℃ in dark conditions for inverted culture for 7 days until the white rot fungus completely covers the surface of the medium. Then, 4 white rot fungus blocks with a diameter of 8mm are moved to a conical flask containing 100mL PDB medium, and the conical flask is placed in a shaking table at 30℃ and 200rpm for aerobic shaking culture for 7 days, and the white rot fungus forms a fungus ball with a diameter of 3mm, which is ready for use.

[0014] Further, the rice straw is 100-mesh rice straw powder; the concentration of the dye pollutant in the mixed solution is 100mg / L; and the dye pollutant includes strong polar azo dye methyl orange, weak polar azo dye methyl red, and metal complex dye naphthol green B.

[0015] Further, the use amount ratio of the degraded straw solution, the bacteria solution of the electricity-producing microorganism MR-1, and the dye pollutant in the mixed solution is 47mL:3mL:0.005g; the anaerobic condition includes that high-purity nitrogen is introduced into the mixed solution to remove oxygen and then the mixed solution is sealed; and the reaction condition is that the reaction temperature is 30±0.5℃, and the shaking table rotation speed is 200±5rpm.

[0016] Specifically, the preparation of the electricity-producing microorganism MR-1 includes:

[0017] First, take the appropriate amount of strain MR-1 stored in a -80℃ refrigerator and melt it, then inoculate it on a solid plate LB medium. Then, invert it in a 30℃, dark environment incubator for culture until single colony colonies are grown. Then, inoculate the single colony colonies into 50mL liquid LB medium and place it in a 30℃, 200rpm shaker for culture to the late logarithmic growth phase. Finally, collect the bacteria with a 50mL centrifuge tube at 7000rpm for 5min, resuspend the bacterial pellet with mineral salt medium, and adjust the bacterial concentration to 4-6x10 8 CFU / mL.

[0018] The application also provides a use of the degradation system or the method in degradation of dye pollutants.

[0019] The beneficial effects of the application are as follows:

[0020] (1) The application first constructs a degradation system using rice straw as a carbon source, white rot fungi and electricity-producing microorganism MR-1 in combination, degrades dye pollutants, realizes the dual goals of pollution control and agricultural solid waste resource utilization, and has important environmental and social benefits.

[0021] (2) The system can realize the utilization of rice straw, an agricultural biomass waste, and also provides a new method for the treatment of dye pollutants.

[0022] (3) The degradation of the application for dye pollutants is not specific, and it has good degradation effect on strong polar azo dye methyl orange, weak polar azo dye methyl red, and metal complex dye naphthol green B. The degradation rate of the application for azo dye methyl orange can reach 95.9%; the degradation rate of azo dye methyl red can reach 97.2%; and the degradation rate of metal complex dye naphthol green B can reach 95.9%. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is the mechanism diagram of the MR-1 and white rot fungi combined system using rice straw as a carbon source to degrade pollutants.

[0024] Figure 2 is the degradation effect diagram of the MR-1 and white rot fungi combined degradation system using rice straw as a carbon source on strong polar azo dye methyl orange.

[0025] Figure 3 is the degradation effect diagram of the MR-1 and white rot fungi combined degradation system using rice straw as a carbon source on weak polar azo dye methyl red.

[0026] Figure 4is a degradation effect diagram of a MR-1 and white rot fungus combined degradation system taking rice straw as a carbon source on metal composite dye naphthol green B. DETAILED DESCRIPTION

[0027] In order to make the technical personnel in the art better understand the technical solutions of the present application, the preferred embodiments of the present application are described in detail below, but the following embodiments do not limit the protection scope of the present application.

[0028] In the embodiments of the present application, those not described in detail are completed by using conventional experimental methods, the processes involved in the embodiments are understood and easily realized by the technical personnel in the art according to the product manual or the basic knowledge in the art, and the materials or reagents without special description are conventional commercially available materials, so they are not described in detail.

[0029] The strain MR-1 described in the present application is a model electrogenic microorganism, which is donated by Professor Nelson of the University of California, USA, and is preserved in the American Type Culture Collection Center (ATCC), with the strain number being ATCC700500 TM ; this strain can be directly purchased from the center. The white rot fungus strain described in the present application is purchased from the China General Microbiological Culture Collection Center (CGMCC).

[0030] Liquid LB medium, solid plate LB medium, mineral salt medium, PDA medium and solid plate PDB medium are all commonly used in the art, and can be purchased or prepared according to the conventional formula.

[0031] Mineral salt medium containing 100-mesh rice straw: replace the lactic acid as a carbon source in the conventional mineral salt medium with 100-mesh sieved rice straw.

[0032] Embodiment:

[0033] A low-carbon source cost dye anaerobic biodegradation system, white rot fungus first hydrolyzes rice straw to generate carbohydrates such as glucose and xylose, and further metabolizes them into small-molecule organic matter such as ethanol. The electrogenic microorganism MR-1 utilizes small-molecule organic matter such as glucose and ethanol for anaerobic respiratory metabolism, releases electrons, and finally transmits the electrons to the dye pollutants, realizing efficient degradation of the pollutants, and the whole process is as shown in Figure 1 .

[0034] The specific implementation steps are as follows:

[0035] (1) Take out an appropriate amount of strain MR-1 stored in a-80℃ refrigerator, melt it, and inoculate it on a solid plate LB medium, and then invert it in a 30℃, dark environment incubator for culture until single colony is grown.

[0036] (2) Using a pipette, aspirate activated single colonies and inoculate them into 50 mL of liquid LB medium. Incubate at 30°C and 200 rpm with shaking for 12 h until the late logarithmic phase. Finally, collect the bacterial cells by centrifugation at 7000 rpm for 5 min in a 50 mL centrifuge tube. Resuspend the bacterial pellet in mineral salt medium and adjust the bacterial concentration to 4–6 × 10⁻⁶. 8 CFU / mL, for later use.

[0037] (3) Prepare solid plate PDA medium, inoculate the white rot fungus onto the PDA medium, and incubate it upside down in a constant temperature incubator at 30°C and in the dark for 7 days until the white rot fungus completely covers the surface of the medium.

[0038] (4) Using an 8mm diameter punch, transfer four white rot fungal blocks from step (3) into an Erlenmeyer flask containing 100mL of PDB medium. Place the Erlenmeyer flask in a shaker at 30℃ and 200rpm for aerobic shaking culture for 7 days. Culture until the white rot fungi form fungal spheres with a diameter of 3mm, then set aside for use.

[0039] (5) Take out the 8 white rot fungal balls from step (4), add them to a mineral salt culture medium containing 100 mesh rice straw, place them in a shaker, and react them at (30±0.5)℃ and (200±5)rpm.

[0040] (6) Add 47ml of the degraded rice straw solution from step (5), 3ml of the bacterial solution from step (2), and 0.005g of dye (methyl orange, methyl red, or naphthol green B) to the serum bottle and mix. Then, purge the mixture with high-purity nitrogen for 15 minutes to remove oxygen, and then seal it.

[0041] Experimental treatment group (MR-1 and white rot fungus combined), negative control group A (MR-1 only), and negative control group B (white rot fungus only) were set up, with three replicates in each group.

[0042] (7) Place the suspension prepared in step (6) into a shaker and incubate it at (30±0.5)℃ and (200±5)rpm. Take samples from the experimental group and the control group, and take the solution in the reaction system into centrifuge tubes and centrifuge at 12000rpm for 5min. After centrifugation, take the supernatant and measure the absorbance of the reaction system solution at its maximum absorption wavelength to calculate the dye degradation rate of the reaction system.

[0043] (8) The degradation rate is calculated using the following formula:

[0044]

[0045] In the formula, OD t The initial absorbance of the dye solution; OD tThe absorbance of the dye solution at degradation time t.

[0046] The rice straw used was obtained from farmland in Zhenjiang (sterilized for use), and the pollutants used were the strong polar azo dye methyl orange, the weak polar azo dye methyl red, and the metal complex dye naphthol green B.

[0047] The degradation effects of the white rot fungus and MR-1 combined degradation system using rice straw as a carbon source on different structural types of dye pollutants, including the strong polar azo dye methyl orange, the weak polar azo dye methyl red, and the metal complex dye naphthol green B, are shown in Figure 2 , Figure 3 and Figure 4

[0048] As can be seen from Figure 2 , the degradation rate of the azo dye methyl orange by the white rot fungus and MR-1 combined degradation system can reach 95.9% at 120h, while the negative control group A is only 45.7% and the negative control group B is only 5.8%.

[0049] As can be seen from Figure 3 , the degradation rate of the azo dye methyl red by the white rot fungus and MR-1 combined degradation system can reach 97.2% at 96h, while the negative control group A is only 50.2% and the negative control group B is only 11.9%.

[0050] As can be seen from Figure 4 , the degradation rate of the metal complex dye naphthol green B by the white rot fungus and MR-1 combined degradation system can reach 95.9% at 120h, while the negative control group A is only 53.3% and the negative control group B is only 11.1%.

[0051] Therefore, Figures 2-4 the results show that the electricity-producing microorganism successfully degrades dye pollutants in the environment using rice straw through the white rot fungus and MR-1 combined degradation system, and the degradation rate of the combined degradation system on different types of dyes all reaches more than 95%, among which the degradation rate of the weak polar azo dye reaches 97.2% within 96 hours, which is the best; the degradation effects of the strong polar azo dye and the metal complex dye are second, but the degradation rates at 120 hours are all as high as 95.9%, which is also very high.

[0052] ​In summary, the combined degradation system of the electrogenic microorganism MR-1 and white rot fungi with rice straw as carbon source showed good degradation ability for different structural types of dye pollutants, such as different polar azo dye wastewater and metal complex dye wastewater, and had broad-spectrum degradation ability. At the same time, the system could use cheap agricultural waste such as rice straw as carbon source, which significantly reduced the cost of carbon source required for the remediation of environmental pollutants by electrogenic microorganisms. More importantly, the system converted waste rice straw into valuable carbon source in a way of waste treatment, realized the recycling of resources, and had important practical significance for the treatment of pollutants.

Claims

1. A method for dye degradation using rice straw as a carbon source, characterized in that, The method uses rice straw as a carbon source and combines white-rot fungi and electrogenic microorganism MR-1 for degradation. The degradation method includes: culturing white-rot fungal cells in PDB medium until fungal spheres are formed; adding the white-rot fungal spheres to a mineral salt medium containing rice straw for degradation reaction to obtain a degraded straw solution; mixing the degraded straw solution, the bacterial solution of electrogenic microorganism MR-1, and the dye contaminant; and placing the mixed solution in a shaker under anaerobic conditions to fully react and degrade the dye; the concentration of rice straw in the mineral salt medium containing rice straw is 100 mg / L, and the rice straw is 100 mesh rice straw powder; the ratio of the degraded straw solution, the bacterial solution of electrogenic microorganism MR-1, and the dye contaminant in the mixed solution is 47 mL: 3 mL: 0.005 g.

2. The method according to claim 1, characterized in that, The conditions for the degradation reaction of rice straw are: reaction temperature 30±0.5℃ and shaking speed 200±5rpm.

3. The method according to claim 1, characterized in that, The bacterial suspension of the electrogenic microorganism MR-1 was obtained by resuspending it in a carbon-free mineral salt medium, and the concentration of the bacterial suspension of the electrogenic microorganism MR-1 was 4–6 × 10⁻⁶. 8 CFU / mL.

4. The method according to claim 1, characterized in that, The dye contaminants include the strongly polar azo dye methyl orange, the weakly polar azo dye methyl red, and the metal complex dye naphthol green B.

5. The method according to claim 1, characterized in that, The oxygen-free conditions include: passing high-purity nitrogen gas into the mixed solution to remove oxygen, and then sealing it.

6. The method according to claim 1, characterized in that, The reaction conditions for the degradation dye are: reaction temperature 30±0.5℃, shaking speed 200±5rpm.

7. The application of the method according to any one of claims 1-6 in the degradation of dye contaminants.

Images