METHOD FOR STRENGTHENING BIOLOGICAL MANGANESE OXIDATION USING MAGNETIC FIELD AND USE THEREOF

Abstract

The present disclosure discloses a method for strengthening a biological manganese oxidation using a magnetic field and use thereof. The method includes steps of inoculating a manganese-oxidizing microorganism into a culture medium containing Mn.sup.2+, performing magnetization treatment in a culture process, and then collecting a biogenic manganese oxide. The method includes steps of performing a primary magnetic field treatment at a magnetic field intensity of 0.2-50 mT for 1-5 h when culturing is performed for 6-12 h, continuing culturing after the primary magnetization treatment, and performing magnetization treatment once every other 24 h for culture time of 72 h. A magnetic field is applied to accelerate an oxidation rate of a manganese-oxidizing microorganism to Mn.sup.2+and a biological manganese oxidation rate is respectively improved by 36.4% and 23.8% under an action of an alternating magnetic field or a constant magnetic field within 72 h.

Claims

1. A method for strengthening a biological manganese oxidation using a magnetic field, comprising steps of inoculating a manganese-oxidizing microorganism into a culture medium containing Mn.sup.2+, performing magnetization treatment in a culture process, and then collecting a biogenic manganese oxide.

2. The method for strengthening a biological manganese oxidation using a magnetic field according to claim 1, wherein the magnetization treatment is as follows: performing a primary magnetization treatment at a magnetic field intensity of 0.2-50 mT for 1-5 h when culturing is performed for 6-12 h, continuing culturing after the primary magnetization treatment, and performing magnetization treatment once every other 24 h for culture time of 72 h.

3. The method for strengthening a biological manganese oxidation using a magnetic field according to claim 2, wherein the magnetic field is an alternating magnetic field or a constant magnetic field.

4. The method for strengthening a biological manganese oxidation using a magnetic field according to claim 1, wherein the manganese-oxidizing microorganism is a manganese-oxidizing bacterium or a manganese-oxidizing fungus.

5. The method for strengthening a biological manganese oxidation using a magnetic field according to claim 1, wherein the culture medium is a liquid culture medium.

6. The method for strengthening a biological manganese oxidation using a magnetic field according to claim 5, wherein the culture medium is an HAY liquid culture medium and comprises the following components: 0.246 g/L of sodium acetate, 0.15 g/L of yeast powder, 0.05 g/L of magnesium sulfate heptahydrate, 5 mg/L of dipotassium hydrogen phosphate, and 2 mL/L of a mineral salt, a buffer solution in the culture medium is HEPES with a final concentration of 20 mM, and a pH is 6.5.

7. The method for strengthening a biological manganese oxidation using a magnetic field according to claim 6, wherein the mineral salt contains the following components: 3.7 g of calcium chloride dihydrate, 0.44 g of zinc sulfate heptahydrate, 0.29 g of sodium molybdate dihydrate, 2.5 g of boric acid, 5 mg of copper sulfate pentahydrate, and 1.0 g of ferric chloride hexahydrate.

8. The method for strengthening a biological manganese oxidation using a magnetic field according to claim 1, wherein the manganese-oxidizing microorganism is inoculated into a culture medium containing Mn.sup.2+ and cultured in an oscillator at a rotating speed of 200 rpm in a dark place at 30° C. for 72 h.

9. A method for accelerating a removal of Cd.sup.2+ in a water body or a solid matrix by a biogenic manganese oxide, wherein the biogenic manganese oxide is prepared using the method according to claim 1, and the method specifically comprises the following steps: collecting and freeze-drying the magnetized biogenic manganese oxide, adding the biogenic manganese oxide into a water body or a solid matrix containing Cd.sup.2+, and performing reaction at 25° C., a pH of 7.0 and 10 mM of KNO.sub.3.

10. A method for accelerating a removal of Cd.sup.2+ in a water body or a solid matrix by a biogenic manganese oxide, wherein the biogenic manganese oxide is prepared using the method according to claim 2, and the method specifically comprises the following steps: collecting and freeze-drying the magnetized biogenic manganese oxide, adding the biogenic manganese oxide into a water body or a solid matrix containing Cd.sup.2+, and performing reaction at 25° C., a pH of 7.0 and 10 mM of KNO.sub.3.

11. A method for accelerating a removal of Cd.sup.2+ in a water body or a solid matrix by a biogenic manganese oxide, wherein the biogenic manganese oxide is prepared using the method according to claim 3, and the method specifically comprises the following steps: collecting and freeze-drying the magnetized biogenic manganese oxide, adding the biogenic manganese oxide into a water body or a solid matrix containing Cd.sup.2+, and performing reaction at 25° C., a pH of 7.0 and 10 mM of KNO.sub.3.

12. A method for accelerating a removal of Cd.sup.2+ in a water body or a solid matrix by a biogenic manganese oxide, wherein the biogenic manganese oxide is prepared using the method according to claim 4, and the method specifically comprises the following steps: collecting and freeze-drying the magnetized biogenic manganese oxide, adding the biogenic manganese oxide into a water body or a solid matrix containing Cd.sup.2+, and performing reaction at 25° C., a pH of 7.0 and 10 mM of KNO.sub.3.

13. A method for accelerating a removal of Cd.sup.2+ in a water body or a solid matrix by a biogenic manganese oxide, wherein the biogenic manganese oxide is prepared using the method according to claim 5, and the method specifically comprises the following steps: collecting and freeze-drying the magnetized biogenic manganese oxide, adding the biogenic manganese oxide into a water body or a solid matrix containing Cd.sup.2+, and performing reaction at 25° C., a pH of 7.0 and 10 mM of KNO.sub.3.

14. A method for accelerating a removal of Cd.sup.2+ in a water body or a solid matrix by a biogenic manganese oxide, wherein the biogenic manganese oxide is prepared using the method according to claim 6, and the method specifically comprises the following steps: collecting and freeze-drying the magnetized biogenic manganese oxide, adding the biogenic manganese oxide into a water body or a solid matrix containing Cd.sup.2+, and performing reaction at 25° C., a pH of 7.0 and 10 mM of KNO.sub.3.

15. A method for accelerating a removal of Cd.sup.2+ in a water body or a solid matrix by a biogenic manganese oxide, wherein the biogenic manganese oxide is prepared using the method according to claim 7, and the method specifically comprises the following steps: collecting and freeze-drying the magnetized biogenic manganese oxide, adding the biogenic manganese oxide into a water body or a solid matrix containing Cd.sup.2+, and performing reaction at 25° C., a pH of 7.0 and 10 mM of KNO.sub.3.

16. A method for accelerating a removal of Cd.sup.2+ in a water body or a solid matrix by a biogenic manganese oxide, wherein the biogenic manganese oxide is prepared using the method according to claim 8, and the method specifically comprises the following steps: collecting and freeze-drying the magnetized biogenic manganese oxide, adding the biogenic manganese oxide into a water body or a solid matrix containing Cd.sup.2+, and performing reaction at 25° C., a pH of 7.0 and 10 mM of KNO.sub.3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 shows scanning electron microscope (SEM) images and energy-dispersive X-ray spectroscopy (EDX) analysis diagrams of biogenic manganese oxides generated by magnetization/no-magnetization according to the present disclosure, wherein (a and b are a control group at magnifications of 1×10.sup.5 and 2×10.sup.5 respectively, and c is an energy-dispersive X-ray spectroscopy diagram of a marked place at 1; and d and e are an experimental group at magnifications of 1×10.sup.5 and 2×10.sup.5 respectively under an action of a magnetic field, and f is an energy-dispersive X-ray spectroscopy diagram of a marked place at 2);

[0026] FIG. 2 shows an influence of magnetization on reaction kinetics of removing Cd.sup.2+ in a water body by biogenic manganese oxides; and

[0027] FIG. 3 shows a manganese oxidation rate of Pseudomonas putida MnB1 at an initial dose of 400 μM Mn.sup.2+ under a magnetic field condition as a change of culture time.

DESCRIPTION OF THE EMBODIMENTS

[0028] A manganese oxidation rate used by the present disclosure is determined in the following manner: a manganese-oxidizing microorganism is cultured, a sample is taken at an interval of specific time, after the sample is filtered by a 0.45 μm filter membrane, a concentration of residual Mn.sup.2+ in a culture solution is tested by an inductively coupled plasma emission spectrometer (Agilent, 5110 series), and the biological manganese oxidation rate is tested according to the following formula:

[0029] biological manganese oxidation rate (%)=(C.sub.0-C.sub.t)/C.sub.0*100%;

[0030] in the formula:

[0031] C.sub.0 is the content of Mn.sup.2+ ions in an initial culture solution; and

[0032] C.sub.t is the content of residual Mn.sup.2+ ions in the culture solution at the time t.

[0033] In the following examples, methods are conventional methods unless otherwise specified and reagents are conventionally commercially available unless otherwise specified.

EXAMPLE 1

[0034] A method for strengthening a biological manganese oxidation using a magnetic field specifically includes the following steps:

[0035] Strain culture: a liquid culture medium (culture medium for shake-flask culture) for culturing a manganese-oxidizing microorganism is an HAY culture medium and includes the following components: 0.246 g/L of sodium acetate, 0.15 g/L of yeast powder, 0.05 g/L of magnesium sulfate heptahydrate, 5 mg/L of dipotassium hydrogen phosphate, and 2 mL/L of a mineral salt (3.7 g of calcium chloride dihydrate, 0.44 g of zinc sulfate heptahydrate, 0.29 g of sodium molybdate dihydrate, 2.5 g of boric acid, 5 mg of copper sulfate pentahydrate, and 1.0 g of ferric chloride hexahydrate), a buffer solution in the culture medium is HEPES with a final concentration of 20 mM, and a pH is 6.5.

[0036] The manganese-oxidizing microorganism (Cladosporium sp. XM01, China General Microbiological Culture Collection Center, and preservation No.: CGMCC NO. 21083) is inoculated into the HAY liquid culture medium (an inoculation amount of 1×10.sup.5 conidia/mL), Mn.sup.2+ with a final concentration of 400 μM and 20 mM of an HEPES buffer solution at a pH of 6.5 are added in a filtration mode, and the microorganism is cultured in an oscillator shake flask at a rotating speed of 200 rpm in a dark place at 30° C. A primary alternating magnetization treatment is performed at a magnetic field intensity of 2-10 mT for 3 h when culturing is performed for 9 h, culturing is continued after the primary magnetization treatment, magnetization treatment is performed once every other 24 h for culture time of 72 h, a sample is taken and filtered by a 0.45 μm filter membrane, a concentration of residual Mn.sup.2+ in a culture solution is tested by an inductively coupled plasma emission spectrometer (Agilent, 5110 series), and thus the manganese oxidation rate is calculated. The control group is not magnetized. As shown in Table 1, the biological manganese oxidation rate under magnetization is obviously improved compared with the control group, wherein the biological manganese oxidation rate is improved by 36.4% at 72 h.

EXAMPLE 2

[0037] The steps different from example 1 are that: after inoculation and culture for 6 h, an alternating magnetic field treatment is performed, then magnetization treatment is performed once every other 24 h for 3 h each treatment time at a magnetic field intensity of 2-10 mT, a manganese oxidation rate at 72 h is shown in Table 1, and compared with the control group, the manganese oxidation rate is improved by 20.8%.

EXAMPLE 3

[0038] The steps different from example 1 are that: after inoculation and culture for 12 h, an alternating magnetic field treatment is performed, then magnetization treatment is performed once every other 24 h for 3 h each treatment time at a magnetic field intensity of 2-10 mT, a manganese oxidation rate at 72 h is shown in Table 1, and compared with the control group, the manganese oxidation rate is improved by 11.9%.

EXAMPLE 4

[0039] The steps different from example 1 are that: after inoculation and culture for 9 h, an alternating magnetic field treatment is performed, then magnetization treatment is performed once every other 24 h for 1 h each treatment time at a magnetic field intensity of 2-10 mT, a manganese oxidation rate at 72 h is shown in Table 1, and compared with the control group, the manganese oxidation rate is improved by 7.1%.

EXAMPLE 5

[0040] The steps different from example 1 are that: after inoculation and culture for 9 h, an alternating magnetic field treatment is performed, then magnetization treatment is performed once every other 24 h for 5 h each treatment time at a magnetic field intensity of 2-10 mT, a manganese oxidation rate at 72 h is shown in Table 1, and compared with the control group, the manganese oxidation rate is improved by 17.3%.

EXAMPLE 6

[0041] The steps different from example 1 are that: after inoculation and culture for 9 h, a constant magnetic field treatment is performed, then magnetization treatment is performed once every other 24 h for 3 h each treatment time at a magnetic field intensity of 0.2-20 mT, a manganese oxidation rate at 72 h is shown in Table 1, and compared with the control group, the manganese oxidation rate is improved by 10.4%.

EXAMPLE 7

[0042] The steps different from example 1 are that: after inoculation and culture for 9 h, a constant magnetic field treatment is performed, then magnetization treatment is performed once every other 24 h for 5 h each treatment time at a magnetic field intensity of 0.2-20 mT, a manganese oxidation rate at 72 h is shown in Table 1, and compared with the control group, the manganese oxidation rate is improved by 23.8%.

EXAMPLE 8

[0043] The steps different from example 1 are that: after inoculation and culture for 9 h, a constant magnetic field treatment is performed, then magnetization treatment is performed once every other 24 h for 5 h each treatment time at a magnetic field intensity of 0.2-50 mT, a manganese oxidation rate at 72 h is shown in Table 1, and compared with the control group (not magnetized), the manganese oxidation rate is improved by 1.3%.

TABLE-US-00001 TABLE 1 Biological manganese oxidation rates of different examples at 72 h Biological manganese oxidation No. Process mode rate (72 h) 1 Control group 58.3% 2 Example 1 94.7% 3 Example 2 79.1% 4 Example 3 70.2% 5 Example 4 65.4% 6 Example 5 75.6% 7 Example 6 68.7% 8 Example 7 82.1% 9 Example 8 59.6%

[0044] It can be seen from Table 1 that how long after inoculation and culture, magnetization treatment, a magnetic field intensity and treatment time have very important influences on the biological manganese oxidation rate. Through data in example 1, the biological manganese oxidation rate is improved by 36.4% compared with the control group when a primary alternating magnetic field treatment is performed at a magnetic field intensity of 0.2-10 mT for 3 h when culturing is performed for 9 h.

EXAMPLE 9

[0045] Scanning electron microscope (SEM) images and energy-dispersive X-ray spectroscopy (EDX) analysis diagrams of biogenic manganese oxides generated under an action of a magnetic field or not.

[0046] The manganese-oxidizing microorganism (Cladosporium sp. XM01, China General Microbiological Culture Collection Center, and preservation No.: CGMCC NO. 21083) is inoculated into the HAY liquid culture medium (an inoculation amount of 1 x10.sup.5 conidia/mL), Mn.sup.2+ with a final concentration of 400 μM and 20 mM of an HEPES buffer solution at a pH of 6.5 are added in a filtration mode, and the microorganism is cultured in an oscillator shake flask at a rotating speed of 200 rpm in a dark place at 30° C. A primary alternating magnetic field treatment is performed at a magnetic field intensity of 0.2-10 mT for 3 h when culturing is performed for 9 h , culturing is continued after the primary magnetization treatment, magnetization treatment is performed once every other 24 h, a biogenic manganese oxide is collected 3 d later, a culture solution is centrifuged at 5,000 r/min for 10 min, a biogenic manganese oxide suspension is then washed with sterile water three times to wash away ions on a surface, and the biogenic manganese oxide is freeze-dried and subjected to a scanning electron microscope observation and an energy-dispersive X-ray spectroscopy analysis.

[0047] A result of the scanning electron microscope images combined with the energy-dispersive X-ray spectroscopy analysis is shown in FIG. 2. Compared with the scanning electron microscope images of control groups 2a and 2b, FIGS. 2d and 2e show that the magnetized biogenic manganese oxide is still a nano-scale manganese oxide, has an irregular shape and a poor crystallinity. However, the biogenic manganese oxide has a small particle size and a large specific surface area after the magnetization treatment, and accelerates adsorption and oxidation performances on heavy metals or trace organic pollutants in a water body or a solid matrix.

[0048] It can be seen from FIGS. 2c and 2f that the carbon content of an extracellular metabolite (biogenic manganese oxide) of the manganese-oxidizing microorganism after the magnetization treatment is obviously reduced, while the content of manganese is obviously increased by 15%, which indicates that the magnetic field accelerates biomineralization of the manganese-oxidizing microorganism and increases a manganese oxidation rate.

EXAMPLE 10

[0049] Influence of magnetic field on reaction kinetics of removing Cd.sup.2+ in water body by biogenic manganese oxides

[0050] The manganese-oxidizing microorganism (Cladosporium sp. XM01, China General

[0051] Microbiological Culture Collection Center, and preservation No.: CGMCC NO. 21083) is inoculated into the HAY liquid culture medium (an inoculation amount of 1×10.sup.5 conidia/mL), Mn.sup.2+ with a final concentration of 400 μM and 20 mM of an HEPES buffer solution at a pH of 6.5 are added in a filtration mode, and the microorganism is cultured in an oscillator shake flask at a rotating speed of 200 rpm in a dark place at 30° C. A primary alternating magnetic field treatment is performed at a magnetic field intensity of 0.2-10 mT for 3 h when culturing is performed for 9 h , culturing is continued after the primary magnetization treatment, magnetization treatment is performed once every other 24 h, a biogenic manganese oxide is collected 3 d later, a culture solution is centrifuged at 5,000 r/min for 10 min, a biogenic manganese oxide suspension is then washed with sterile water three times to wash away ions on a surface, and the biogenic manganese oxide is freeze-dried at −50° C. using a freeze-drying agent and then stored in a 26° C. aerobic incubator for later use.

[0052] A reaction of removing Cd.sup.2+ from a water body by the biogenic manganese oxide is performed in a fully mixed reactor. 0.3 g/L of the biogenic manganese oxide is added into water containing 21.9 mg/L of Cd.sup.2+ at a pH of 7.0 and 10 mM of KNO.sub.3.

[0053] As shown in FIG. 2, reaction kinetics of the magnetized biogenic manganese oxide on removing Cd.sup.2+ is obviously faster than that of a control group. The magnetized biogenic manganese oxide can remove Cd.sup.2+ within 60 min by 62% and the unmagnetized biogenic manganese oxide can only remove Cd.sup.2+ by 47% even after 180 min.

EXAMPLE 11

[0054] The magnetic field can improve a dehydrogenase activity (NADH dehydrogenase and succinate dehydrogenase) and an electron transfer chain activity of a manganese-oxidizing microorganism. An action mechanism is that the different manganese-oxidizing microorganisms have a common action and play a role in accelerating a biological manganese oxidization process. Therefore, it can be inferred that when the magnetic field intensity is 0.2-50 mT in the present application, the magnetic field has both positive influences on manganese-oxidizing fungi and manganese-oxidizing bacteria. Besides, the positive influence on the mainstream manganese-oxidizing bacteria or manganese-oxidizing fungi at present can be realized.

[0055] In order to verify that when the magnetic field intensity is 0.2-50 mT in the present application, the manganese-oxidizing fungi and the manganese-oxidizing bacteria are positively influenced. The applicant performs an experiment on the most common manganese-oxidizing microorganisms before:

[0056] currently, the manganese-oxidizing bacteria are mainly concentrated on these three model bacteria: Pseudomonas putida MnB1 and GB−1, gram-negative bacteria, produce a manganese oxide on a cell surface, and live mainly in fresh water and soil; Bacillus SG−1, a gram-positive rod-shaped bacterium, produces manganese-oxidizing spores; and Leptothrix discophora SS-1 and SP-6 are flaky bacteria living in fresh water and deposit a manganese oxide on their cell sheaths. In order to investigate an influence of the magnetic field on common manganese-oxidizing bacteria, a common manganese-oxidizing bacterium Pseudomonas putida MnB1 is selected. The strain is given by associate professor Tong Man, China University of Geosciences, Wuhan. The influence of the magnetic field on a manganese oxidation of the Pseudomonas putida MnB1 is investigated. The specific experimental steps and results are as follows:

[0057] after the strain stored in a 4° C. refrigerator is activated of for 6-8 h, the strain is inoculated into an LP liquid culture medium at a ratio of 5%, Mn.sup.2+ with a final concentration of 400 μM and an HEPES buffer solution (20 mM, pH 7.5) are added in a 0.22-μM filter membrane filtration mode, and the strain is cultured in an oscillator shake flask at a rotating speed of 200 rpm in a dark place at 25° C. A primary magnetization treatment is performed at a magnetic field intensity of 0.2-50 mT for 5 h when culturing is performed for 6 h, culturing is continued after the primary magnetization treatment, and magnetization treatment is performed once every other 24 h for culture time of 96 h. Samples are taken at 0 h, 24 h, 36 h, 48 h, 56 h, 72 h, 84 h and 96 h, respectively and filtered by a 0.45-μm filter membrane. A concentration of residual Mn.sup.2+ in a culture solution is tested by an inductively coupled plasma emission spectrometer (Agilent, 5110 series), and the manganese oxidation rate is calculated. The results are shown in FIG. 3. As can be seen from the figure, the magnetic field significantly increases the manganese oxidation rate compared to the control group, for example, at 56 h the manganese oxidation rate is increased by 17.0%. From the above results, it can be seen that in the present application, when the magnetic field intensity is 0.2-50 mT, the magnetic field also has a positive influence on the manganese-oxidizing bacteria. Besides, the positive influence on the mainstream manganese-oxidizing bacteria or manganese-oxidizing fungi at present can be realized.

[0058] The above description of the examples is intended to facilitate a person of ordinary skill in the art to understand and use the present disclosure. Obviously, a person skilled in the art can easily make various modifications to these examples, and apply a general principle described herein to other examples without creative efforts. Therefore, the present disclosure is not limited to the above examples. All improvements and modifications made by a person skilled in the art according to implication of the present disclosure without departing from the spirit of the present disclosure should fall within the protection scope of the present disclosure.