Method for Promoting Degradation of Polychlorinated Biphenyls (PCBs) by Pseudomonas JD37 With Nanoscale Zero-Valent Iron (nZVI) and Use Thereof

Abstract

The present disclosure provides a method for promoting degradation of polychlorinated biphenyls (PCBs) by Pseudomonas JD37 with nanoscale zero-valent iron (nZVI) and use thereof. The method includes the following steps: adding nZVI and Pseudomonas JD37 in an environment having PCBs, and promoting degradation of the PCBs by the Pseudomonas JD37 with the nZVI. The nZVI increases an active oxygen content produced by extracellular metabolism of the Pseudomonas JD37, thus promoting degradation of the PCBs. Therefore, the method of the present disclosure is suitable for degrading the PCBs in water and soil for environmental restoration.

Claims

1. A method for promoting degradation of polychlorinated biphenyls (PCB s) by Pseudomonas JD37 with nanoscale zero-valent iron (nZVI), comprising the following steps: adding nZVI and Pseudomonas JD37 in an environment having PCBs, and promoting degradation of the PCBs by the Pseudomonas JD37 with the nZVI; wherein the environment comprises water and soil.

2. The method for promoting degradation of PCBs by Pseudomonas JD37 with nZVI according to claim 1, wherein the nZVI has a size of 20 nm to 100 nm.

3. The method for promoting degradation of PCBs by Pseudomonas JD37 with nZVI according to claim 1, wherein the Pseudomonas JD37 is Pseudomonas JD37 in middle and late stages of a logarithmic growth phase, and is prepared by the following steps: inoculating a Pseudomonas JD37 strain into a liquid medium after sterilization, and conducting shaking culture until bacterial cells are in the middle and late stages of the logarithmic growth phase.

4. The method for promoting degradation of PCBs by Pseudomonas JD37 with nZVI according to claim 3, wherein the liquid medium has a pH value of 6.5 to 7.5, and comprises 5 g/L to 10 g/L of tryptone, 2 g/L to 5 g/L of a yeast extract, 5 g/L to 10 g/L of sodium chloride, and water as a solvent; and the shaking culture is conducted at 28 C. to 30 C. and 150 rpm to 200 rpm for 12 h to 18 h.

5. The method for promoting degradation of PCBs by Pseudomonas JD37 with nZVI according to claim 1, wherein when the environment is water, the nZVI is added in an amount of mg/L to 100 mg/L; when the environment is water, the Pseudomonas JD37 has an OD.sub.600 value of 0.1 to 0.3; and the environment having PCBs has 0.01 mg/L to 1.0 mg/L of the PCBs.

6. The method for promoting degradation of PCBs by Pseudomonas JD37 with nZVI according to claim 1, wherein when the environment is soil, the nZVI is added in an amount of 10 mg/L to 1,000 mg/L.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 shows an impact of zero-valent iron with different sizes on extracellular hydroxyl radicals of Pseudomonas JD37; and

[0021] FIG. 2 shows an impact of zero-valent iron with different sizes on extracellular superoxide radicals of Pseudomonas JD37.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] To make the objective, technical solution, and advantages of the present disclosure clearer, the present disclosure will be further described in detail with reference to the drawings and examples. It should be understood that the specific examples described here are only used to explain the present disclosure, rather than all the examples. All other examples obtained by those of ordinary skill in the art based on the examples of the present disclosure without creative efforts should fall within the protection scope of the present disclosure.

[0023] In the following examples, the experimental methods in which specific conditions are not stated are generally conducted according to conventional conditions or according to the conditions recommended by the manufacturer. The materials, reagents, etc. used in the following examples are all commercially available, unless otherwise specified.

Example 1 (nZVI.SUB.100 .Group)

[0024] (1) Shake-Flask Culture of Pseudomonas JD37

[0025] 10 g of tryptone, 5 g of a yeast extract, and 10 g of sodium chloride were added into 1,000 mL of water, mixed well, adjusted to a pH value of 7.0, put into a 2,000 mL Erlenmeyer flask, autoclaved at 121 C. for 20 min, and cooled to a room temperature to obtain a liquid medium; a slant strain of Pseudomonas JD37 (Pseudomonas chlororaphis subsp. aurantiaca JD37, preserved in the CGMCC with a deposit number of CGMCC No. 1.10967) was inoculated into the liquid medium with an inoculation loop at an inoculum size of 2 loops; the Erlenmeyer flask was placed in a shaking incubator and incubated at 30 C. and 180 rpm for 18 h to obtain a shake-flask culture solution; and the shake-flask culture solution was centrifuged at 4,000 rpm and 4 C. for 10 min to obtain Pseudomonas JD37 cells.

[0026] (2) Degradation of PCBs by Pseudomonas JD37

[0027] In this example, the PCB was 2,4,4-trichlorodiphenyl (PCB28).

[0028] 1.0 mg of the PCB28 was dissolved in 10 mL of an acetone solution as a PCB stock solution used in the experiment, where the acetone was chromatographically-pure grade. 100 L of the stock solution was added to a 200 mL Erlenmeyer flask, 10 mg of nZVI (nZVI.sub.100) with a size of 100 nm was added after the acetone volatilized, a mixture was added into 100 mL of a sterilized and cooled base salt medium, and then added with 0.4 g of glucose as a growth carbon source of the Pseudomonas JD37, to obtain a medium containing PCB28; the Pseudomonas JD37 cells prepared in step (1) were inoculated into the Erlenmeyer flask with the PCB28-containing medium, adjusted to OD.sub.600=0.1, the Erlenmeyer flask was put into a shaking incubator, and incubated by shaking at 30 C. and 180 rpm; a culture solution was extracted at 1 h, 4 h, 8 h, 18 h, 24 h, 48 h, and 72 h separately, and a concentration of PCB28 was measured in the culture solution; a calculated half-life of PCB28 degradation by Pseudomonas JD37 was 8.1 h.

[0029] The base salt medium included: 2.8 g/L disodium hydrogen phosphate, 1.0 g/L potassium dihydrogen phosphate, 0.5 g/L ammonium sulfate, 0.1 g/L magnesium chloride hexahydrate, 0.05 g/L calcium salt tetrahydrate, 0.5 mg/L disodium EDTA, 0.01 mg/L zinc sulfate heptahydrate, mg/L manganese chloride tetrahydrate, 0.03 mg/L boric acid, 0.02 mg/L cobalt chloride hexahydrate, 0.001 mg/L copper chloride dihydrate, 0.002 mg/L nickel chloride hexahydrate, and mg/L sodium molybdate dihydrate.

Example 2 (nZVI.SUB.20 .Group)

[0030] (1) Shake-Flask Culture of Pseudomonas JD37

[0031] 10 g of tryptone, 5 g of a yeast extract, and 10 g of sodium chloride were added into 1,000 mL of water, mixed well, adjusted to a pH value of 7.0, put into a 2,000 mL Erlenmeyer flask, autoclaved at 121 C. for 20 min, and cooled to a room temperature to obtain a liquid medium; a slant strain of Pseudomonas JD37 (Pseudomonas chlororaphis subsp. aurantiaca JD37, preserved in the CGMCC with a deposit number of CGMCC No. 1.10967) was inoculated into the liquid medium with an inoculation loop at an inoculum size of 2 loops; the Erlenmeyer flask was placed in a shaking incubator and incubated at 30 C. and 180 rpm for 18 h to obtain a shake-flask culture solution; and the shake-flask culture solution was centrifuged at 4,000 rpm and 4 C. for 10 min to obtain Pseudomonas JD37 cells.

[0032] (2) Degradation of PCBs by Pseudomonas JD37

[0033] In this example, the PCB was 2,4,4-trichlorodiphenyl (PCB28).

[0034] 1.0 mg of the PCB28 was dissolved in 10 mL of an acetone solution as a PCB stock solution used in the experiment, where the acetone was chromatographically-pure grade. 100 L of the stock solution was added to a 200 mL Erlenmeyer flask, 10 mg of nZVI (nZVI.sub.20) with a size of 20 nm was added after the acetone volatilized, a mixture was added into 100 mL of a sterilized and cooled base salt medium, and then added with 0.4 g of glucose as a growth carbon source of the Pseudomonas JD37, to obtain a medium containing PCB28; the Pseudomonas JD37 cells prepared in step (1) were inoculated into the Erlenmeyer flask with the PCB28-containing medium, adjusted to OD.sub.600=0.1, the Erlenmeyer flask was put into a shaking incubator, and incubated by shaking at 30 C. and 180 rpm; a culture solution was extracted at 1 h, 4 h, 8 h, 18 h, 24 h, 48 h, and 72 h separately, and a concentration of PCB28 was measured in the culture solution; a calculated half-life of PCB28 degradation by Pseudomonas JD37 was 13.2 h.

[0035] The base salt medium included: 2.8 g/L disodium hydrogen phosphate, 1.0 g/L potassium dihydrogen phosphate, 0.5 g/L ammonium sulfate, 0.1 g/L magnesium chloride hexahydrate, 0.05 g/L calcium salt tetrahydrate, 0.5 mg/L disodium EDTA, 0.01 mg/L zinc sulfate heptahydrate, mg/L manganese chloride tetrahydrate, 0.03 mg/L boric acid, 0.02 mg/L cobalt chloride hexahydrate, 0.001 mg/L copper chloride dihydrate, 0.002 mg/L nickel chloride hexahydrate, and mg/L sodium molybdate dihydrate.

[0036] Blank Group (CK Group)

[0037] (1) Shake-Flask Culture of Pseudomonas JD37

[0038] 10 g of tryptone, 5 g of a yeast extract, and 10 g of sodium chloride were added into 1,000 mL of water, mixed well, adjusted to a pH value of 7.0, put into a 2,000 mL Erlenmeyer flask, autoclaved at 121 C. for 20 min, and cooled to a room temperature to obtain a liquid medium; a slant strain of Pseudomonas JD37 (Pseudomonas chlororaphis subsp. aurantiaca JD37, preserved in the CGMCC with a deposit number of CGMCC No. 1.10967) was inoculated into the liquid medium with an inoculation loop at an inoculum size of 2 loops; the Erlenmeyer flask was placed in a shaking incubator and incubated at 30 C. and 180 rpm for 18 h to obtain a shake-flask culture solution; and the shake-flask culture solution was centrifuged at 4,000 rpm and 4 C. for 10 min to obtain Pseudomonas JD37 cells.

[0039] (2) Degradation of PCBs by Pseudomonas JD37

[0040] In this example, the PCB was 2,4,4-trichlorodiphenyl (PCB28).

[0041] 1.0 mg of the PCB28 was dissolved in 10 mL of an acetone solution as a PCB stock solution used in the experiment, where the acetone was chromatographically-pure grade. 100 L of the stock solution was added to a 200 mL Erlenmeyer flask, a resulting mixture was added to 100 mL of a sterilized and cooled base salt medium after the acetone volatilized, and then added with 0.4 g of glucose as a growth carbon source of the Pseudomonas JD37, to obtain a medium containing PCB28; the Pseudomonas JD37 cells prepared in step (1) were inoculated into the Erlenmeyer flask with the PCB28-containing medium, adjusted to OD.sub.600=0.1, the Erlenmeyer flask was put into a shaking incubator, and incubated by shaking at 30 C. and 180 rpm; a culture solution was extracted at 1 h, 4 h, 8 h, 18 h, 24 h, 48 h, and 72 h separately, and a concentration of PCB28 was measured in the culture solution; a calculated half-life of PCB28 degradation by Pseudomonas JD37 was 16.5 h.

[0042] The base salt medium included: 2.8 g/L disodium hydrogen phosphate, 1.0 g/L potassium dihydrogen phosphate, 0.5 g/L ammonium sulfate, 0.1 g/L magnesium chloride hexahydrate, 0.05 g/L calcium salt tetrahydrate, 0.5 mg/L disodium EDTA, 0.01 mg/L zinc sulfate heptahydrate, mg/L manganese chloride tetrahydrate, 0.03 mg/L boric acid, 0.02 mg/L cobalt chloride hexahydrate, 0.001 mg/L copper chloride dihydrate, 0.002 mg/L nickel chloride hexahydrate, and mg/L sodium molybdate dihydrate.

Comparative Example 1 (mZVI Group)

[0043] (1) Shake-Flask Culture of Pseudomonas JD37

[0044] 10 g of tryptone, 5 g of a yeast extract, and 10 g of sodium chloride were added into 1,000 mL of water, mixed well, adjusted to a pH value of 7.0, put into a 2,000 mL Erlenmeyer flask, autoclaved at 121 C. for 20 min, and cooled to a room temperature to obtain a liquid medium; a slant strain of Pseudomonas JD37 (Pseudomonas chlororaphis subsp. aurantiaca JD37, preserved in the CGMCC with a deposit number of CGMCC No. 1.10967) was inoculated into the liquid medium with an inoculation loop at an inoculum size of 2 loops; the Erlenmeyer flask was placed in a shaking incubator and incubated at 30 C. and 180 rpm for 18 h to obtain a shake-flask culture solution; and the shake-flask culture solution was centrifuged at 4,000 rpm and 4 C. for 10 min to obtain Pseudomonas JD37 cells.

[0045] (2) Degradation of PCBs by Pseudomonas JD37

[0046] In this example, the PCB was 2,4,4-trichlorodiphenyl (PCB28).

[0047] 1.0 mg of the PCB28 was dissolved in 10 mL of an acetone solution as a PCB stock solution used in the experiment, where the acetone was chromatographically-pure grade. 100 L of the stock solution was added to a 200 mL Erlenmeyer flask, 10 mg of zero-valent iron (mZVI) with a size of 5 m was added after the acetone volatilized, a mixture was added into 100 mL of a sterilized and cooled base salt medium, and then added with 0.4 g of glucose as a growth carbon source of the Pseudomonas JD37, to obtain a medium containing PCB28; the Pseudomonas JD37 cells prepared in step (1) were inoculated into the Erlenmeyer flask with the PCB28-containing medium, adjusted to OD.sub.600=0.1, the Erlenmeyer flask was put into a shaking incubator, and incubated by shaking at 30 C. and 180 rpm; a culture solution was extracted at 1 h, 4 h, 8 h, 18 h, 24 h, 48 h, and 72 h separately, and a concentration of PCB28 was measured in the culture solution; a calculated half-life of PCB28 degradation by Pseudomonas JD37 was 16.1 h.

[0048] The base salt medium included: 2.8 g/L disodium hydrogen phosphate, 1.0 g/L potassium dihydrogen phosphate, 0.5 g/L ammonium sulfate, 0.1 g/L magnesium chloride hexahydrate, 0.05 g/L calcium salt tetrahydrate, 0.5 mg/L disodium EDTA, 0.01 mg/L zinc sulfate heptahydrate, mg/L manganese chloride tetrahydrate, 0.03 mg/L boric acid, 0.02 mg/L cobalt chloride hexahydrate, 0.001 mg/L copper chloride dihydrate, 0.002 mg/L nickel chloride hexahydrate, and mg/L sodium molybdate dihydrate.

Comparative Example 2 (-Fe.SUB.2.O.SUB.3 .Group)

[0049] Compared with Comparative Example 1, the difference was only in that hematite (-Fe.sub.2O.sub.3) with a size of 20 nm was used to replace the zero-valent iron (mZVI) with a size of 5 m, and a calculated half-life of PCB28 degradation by Pseudomonas JD37 was 14.8 h.

Comparative Example 3 (-Fe.SUB.2.O.SUB.3 .Group)

[0050] Compared with Comparative Example 1, the difference was only in that maghemite (-Fe.sub.2O.sub.3) with a size of 20 nm was used to replace the zero-valent iron (mZVI) with a size of 5 m, and a calculated half-life of PCB28 degradation by Pseudomonas JD37 was 19.1 h.

Comparative Example 4 (Fe.SUB.3.O.SUB.4 .Group)

[0051] Compared with Comparative Example 1, the difference was only in that magnetite (Fe.sub.3O.sub.4) with a size of 20 nm was used to replace the zero-valent iron (mZVI) with a size of 5 m, and a calculated half-life of PCB28 degradation by Pseudomonas JD37 was 16.9 h.

Comparative Example 5 (FeSO.SUB.4 .Group)

[0052] Compared with Comparative Example 1, the difference was only in that FeSO.sub.4 was used to replace the zero-valent iron (mZVI) with a size of 5 m, and a calculated half-life of PCB28 degradation by Pseudomonas JD37 was 15.2 h.

Comparative Example 6 (Fe.SUB.2.(SO.SUB.4.).SUB.3 .Group)

[0053] Compared with Comparative Example 1, the difference was only in that Fe.sub.2(SO.sub.4).sub.3 was used to replace the zero-valent iron (mZVI) with a size of 5 m, and a calculated half-life of PCB28 degradation by Pseudomonas JD37 was 18.3 h.

[0054] The contents of hydroxyl radicals during the degradation of PCBs by Pseudomonas JD37 in Example 1, Example 2, and the blank group were measured, respectively, and the measurement results were shown in FIG. 1. The absorption spectra of superoxide radicals during the degradation of PCBs by Pseudomonas JD37 in Example 1, Example 2, and the blank group were measured, respectively, and the measurement results were shown in FIG. 2. It was seen from FIG. 1 and FIG. 2 that nZVI could promote the production of extracellular hydroxyl radicals of Pseudomonas JD37, especially nZVI with a size of 100 nm could significantly promote the production of extracellular hydroxyl radicals of Pseudomonas JD37; the nZVI could also promote the production of extracellular superoxide radicals of Pseudomonas JD37, especially nZVI with a size of 100 nm could obviously promote the production of extracellular superoxide radicals of Pseudomonas JD37. Therefore, Pseudomonas JD37 in Example 1 had the minimum degradation half-life, which was obviously shorter than that of the blank group. In summary, nZVI can promote the degradation of PCBs by Pseudomonas JD37.

[0055] Through the degradation half-life of PCB28 in Comparative Example 1 to Comparative Example 6, it can be seen that other iron-containing materials cannot promote the degradation of PCBs by Pseudomonas JD37.

[0056] The above descriptions are merely preferred examples of the present disclosure, and are not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, and the like made within the spirit and principle of the present disclosure shall fall within the protection scope of the present disclosure.