Application of a microalga in the removal of selenium from water

Abstract

This invention discloses the application of a microalgae in the removal of selenium from water. This invention is based on the inventors' discovery that Coelastrum sp. GX03 has a selenium-removing effect. This algal strain can grow in selenium-polluted water and efficiently remove selenium, indicating its potential application in removing selenium from water.

Description

Technical Field

[0001] This invention relates to the field of biological treatment of pollutants, and particularly to the application of a microalgae in the removal of selenium from water. Background Technology

[0002] Selenium, depending on its dosage, can function as both an essential micronutrient and a toxin. While selenium has positive effects on organisms at low concentrations, it is toxic at high concentrations, posing a threat to biological and human health. Due to human activities such as mining and smelting, excessive selenium levels in aquatic environments are frequently reported. Selenium in water exists primarily in the forms of selenite and selenate, with selenite being more toxic than selenate. On the other hand, selenium is an essential trace element for the human body and plays an important role in antioxidation, anti-aging, and antiviral activity. However, more than one billion people worldwide suffer from selenium deficiency, making selenium supplementation an urgent need. However, the dosage boundary for inorganic selenium supplementation is very narrow, while organic selenium supplements are safer and more effective. Therefore, converting selenium into organic selenium through microbial processing is an important strategy.

[0003] Microalgae, with their rapid growth, small size, large specific surface area, and strong tolerance to pollutants, have broad application prospects in water pollutant removal. Some studies have also reported on the removal and conversion of selenium by microalgae. Compared with traditional chemical or physical treatment technologies, microalgae removal / conversion of selenium has advantages such as low cost, sustainability, and eco-friendliness. However, research on the toxic effects of selenium on different microalgae and their removal and conversion of different concentrations of selenium remains limited. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings and deficiencies of the prior art and to provide an application of a microalga in the removal of selenium from water.

[0005] The objective of this invention is achieved through the following technical solution: the application of a microalga in the removal of selenium from water. The microalga is named Coelastrum sp. GX03, with accession number CCTCC NO: M20241314, accession date June 20, 2024, and deposited at the China Center for Type Culture Collection, Wuhan University, Wuhan, China.

[0006] The application of the above-mentioned microalgae in removing selenium from water includes the following steps: adding microalgae seed solution to selenium-polluted water for cultivation to remove selenium.

[0007] The algal culture solution is a microalgae culture solution cultured to the logarithmic growth phase; preferably obtained by the following steps: inoculating the microalgae culture solution into the culture medium and culturing it to the logarithmic growth phase or the stationary phase.

[0008] The culture is preferably carried out at 25-30℃, light intensity of 10000-12000 lux, and light-dark time of 10-14h:10-14h; more preferably, it is carried out at 28±0.5℃, light intensity of 10000±1000 lux, and light-dark time of 16h:8h.

[0009] The culture medium is preferably TAP liquid culture medium.

[0010] The composition of TAP liquid culture medium is as follows: 2.42 g of tris(hydroxymethyl)aminomethane, 25 mL of TAP salt solution, 1 mL of phosphate solution, 1 mL of trace element solution, and 1 mL of CH3COOH.

[0011] The composition of the TAP salt solution is as follows: NH4Cl 15g / L, MgSO4·7H2O 4g / L, CaCl2·2H2O 2g / L.

[0012] The phosphate solution has the following composition: K2HPO4 28.8g / 100mL, KH2PO4 14.4g / 100mL.

[0013] The composition of the trace element solution is as follows: Na₂EDTA·2H₂O 5.00 g / 100 mL, ZnSO₄·7H₂O 2.2 g / 100 mL, H₃BO₃ 1.14 g / 100 mL, MnCl₂·4H₂O 0.5 g / 100 mL, FeSO₄·7H₂O 0.5 g / 100 mL, CoCl₂·6H₂O 0.16 g / 100 mL, CuSO₄·5H₂O 0.16 g / 100 mL, (NH₄)₆Mo₇O 24 ·4H2O 0.11g / 100mL.

[0014] The amount of microalgae species or microalgae solution added is based on the OD of algal cells in the water. 680 Calculated as 0.1 to 0.2; more preferably based on the OD of algal strains in the water. 680 Calculated as 0.1.

[0015] The selenium in the selenium-polluted water is inorganic selenium; preferably a tetravalent selenium compound, such as sodium selenite.

[0016] The selenium concentration in the selenium-polluted water body is below 8 mg / L; preferably below 4 mg / L; more preferably 2 to 4 mg / L.

[0017] The present invention has the following advantages and effects compared with the prior art:

[0018] This invention discovers that Coelastrum sp. GXO3 can efficiently remove selenium, thus Coelastrum sp. GXO3 has the potential to remove selenium from water. Attached Figure Description

[0019] Figure 1 These are experimental photos of Coelastrum sp. GX03 cultured in TAP medium with different concentrations of selenium for 0, 4, and 8 days.

[0020] Figure 2 The OD values ​​of Coelastrum sp. GX03 in TAP medium with different concentrations of selenium are... 680 Result image.

[0021] Figure 3 The figure shows the chlorophyll content of Coelastrum sp. GX03 in TAP medium with different concentrations of selenium; where (a) is the chlorophyll a content, (b) is the chlorophyll b content, and (c) is the carotenoid content.

[0022] Figure 4 The graph shows the changes in two chlorophyll fluorescence parameters of Coelastrum sp. GX03 in TAP medium with different concentrations of selenium; where (a) is Fv / Fm and (b) is Pi_abs.

[0023] Figure 5 These are graphs showing the selenium removal effect of Coelastrum sp. GX03 on days 4 and 8 at different selenium concentrations. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0025] Example 1: Evaluation of the toxicity of sodium selenite to this algae

[0026] To evaluate the growth of the microalga Coelastrum sp. GX03, isolated, purified, and identified in our laboratory, in a medium containing sodium selenite. This experiment involved adding sodium selenite to TAP liquid medium to simulate selenium-containing wastewater, followed by the addition of the algal inoculum for cultivation.

[0027] (1) The TAP liquid culture medium was autoclaved at 121℃ for 16 minutes. After cooling, 400 mL was poured into 1000 mL glass Erlenmeyer flasks, and 18 flasks were divided into 1 control group and 5 experimental groups, with 3 replicates for each group.

[0028] (2) Selenium stock solution was added to the sterilized TAP liquid medium in the experimental group to achieve final selenium concentrations of 0.02, 0.2, 2, 4, and 8 mg / L, respectively. Coelastrum sp. GX03 algae was inoculated, with an initial algal concentration of OD0.02. 680 =0.1, incubated at an incubator temperature of 28.0±0.5℃, light intensity of 10000±1000 lux, day-night ratio of 16h:8h, and shaken 2-3 times a day; a control group without selenium stock solution was also set up.

[0029] (3) Samples were taken on days 0, 2, 4, 6 and 8 of the experiment to determine the growth index of Coelastrum sp.GX03. Figure 1 Photos of the experimental process. OD of Coelastrum sp. GX03 680 The results are as follows Figure 2 As shown, low concentrations of selenium (0.02 mg / L) had no significant effect on GX03 cell density, but high concentrations of selenium (≥0.2 mg / L) significantly inhibited its growth, and cell density gradually decreased with increasing concentration. Following the method described in the reference (Lichtenthaler HK, Wellburn AR, Determination of total carotenoids and chlorophyll a and b of leaf extracts in different solvents), the chlorophyll content of GX03 cells under different selenium treatments was detected. The contents of chlorophyll a (Chla), chlorophyll b (Chlb), and carotenoids (Cars) were measured as follows: Figure 3 As shown in the results on day 8, treatments with 0.02 and 0.2 mg / L selenium slightly increased pigment accumulation, while the other selenium treatments significantly decreased it. (Based on OD...) 680 The growth rate of GX03 on day 8 compared with Chla (Table 1) showed that low selenium concentration had a positive effect on the growth rate of GX03, while high selenium concentration had a significant negative effect. The measured Fv / Fm and Pi_abs results for GX03 are shown below. Figure 4 This reflects that high concentrations of selenium severely damage the photosystem of GXO3, inhibiting its photosynthetic performance.

[0030] Table 1 uses OD as the unit of measurement. 680 Or, the specific growth rate (d) of GX03 under different selenium concentrations calculated by Chla. -1 )

[0031]

[0032] Note: Different letters in the same row indicate significant differences (p<0.05).

[0033] (4) On day 8 of the experiment, the algal solutions treated with CK, 0.02 mg / L, 0.2 mg / L, and 2 mg / L selenium were freeze-dried into algal powder samples. The biomass yield, lipid yield, elemental composition, methane potential, and calorific value of Coelastrum sp. GX03 were determined. The results of algal biomass yield and lipid yield analysis under different treatments are shown in Table 2. The maximum algal biomass under the 0.02 mg / L selenium treatment was 0.960 ± 0.084 g / L, which was slightly higher than that of the control group, the 0.2 mg / L selenium treatment, and the 2 mg / L selenium treatment. In terms of biomass yield, the biomass yield of the 0.02 mg / L selenium treatment (120 ± 11 mg / L / d) was slightly higher than that of the control group, the 0.2 mg / L selenium treatment, and the 2 mg / L selenium treatment. The difference between the treatments was not significant. This indicates that although different concentrations of selenium affected the growth and photosynthetic system of GX03, GX03 basically eliminated the negative impact of the super-tolerant concentration of selenium on its biomass accumulation over time. The lipid contents of algae treated with 0.02, 0.2, and 2 mg / L selenium were 6.41±2.12%, 7.98±4.13%, and 7.04±1.80%, respectively, and the lipid yields were 7.84±3.32 mg / L / d, 9.37±4.81 mg / L / d, and 7.85±2.26 mg / L / d, respectively. There were no significant differences among the selenium-treated groups, but compared with the control group (22.9±2.7% lipid content and 21.0±1.1 mg / L / d lipid yield), both showed a significant decrease, with the lipid yield decreasing by 65-72%.

[0034] Table 2. GX3 biomass and lipid production capacity under different treatments.

[0035]

[0036] Note: Different letters in the same column indicate significant differences (p<0.05), and the same applies below.

[0037] The elemental composition analysis results of the dry algal biomass under different treatments are shown in Table 3. The nitrogen content (8.34%) of algae treated with 2 mg / L selenium was significantly lower than that of other treatments, while the carbon content and carbon-nitrogen ratio of algae treated with 0.02 mg / L selenium were significantly lower than those of the control group. In terms of theoretical methanogenic potential and calorific value, the selenium treatments were significantly lower than the control group, with reductions of 10.4%, 9.2%, and 7.2%, and 3.5%, 2.6%, and 2.2%, respectively.

[0038] Table 3. Elemental composition, methane potential, and calorific value assessment of GX3 under different treatments.

[0039]

[0040] In summary, although selenium stress significantly reduced the lipid content of GX03, it had little impact on the biomass' methane potential and calorific value. This indicates that GX03 can remove selenium under selenium stress, and the harvested algal biomass still possesses strong bioenergy potential. Therefore, it has promising application prospects.

[0041] Example 2: Evaluation of the sodium selenite removal capacity of this algae

[0042] This study evaluated the ability of the microalga Coelastrum sp. GX03, isolated, purified, and identified in our laboratory, to remove inorganic selenium in a simulated sodium selenite-containing medium. The experiment involved adding sodium selenite to TAP liquid medium to simulate selenium-polluted water, followed by the addition of the algal strain for cultivation.

[0043] (1) Put TAP liquid culture medium into a high-pressure steam sterilizer for sterilization at 121℃ for 16 min. After cooling, 400 mL is poured into 1000 mL glass Erlenmeyer flasks, and 18 flasks are divided into 1 control group and 5 experimental groups, with 3 replicates for each group.

[0044] (2) Selenium stock solution was added to the sterilized TAP liquid medium of the experimental group to make the final selenium concentrations 0.02, 0.2, 2, 4 and 8 mg / L respectively. Coelastrum sp. GX03 algae was inoculated and the initial algal concentration was set at OD. 680 =0.1, incubated at an incubator temperature of 28.0±0.5℃, light intensity of 10000±1000 lux, day-night ratio of 16h:8h, and shaken 2-3 times a day; a control group without selenium stock solution was also set up.

[0045] (3) Samples were taken on days 4 and 8 of the experiment, and the concentration of selenium in the culture medium was determined by inductively coupled plasma mass spectrometry according to HJ 700-2014. The removal effect of Coelastrum sp. GX03 on sodium selenite on days 4 and 8 is as follows: Figure 5 As shown, on day 4, the 0.2 mg / L and 2 mg / L groups were significantly higher than other treatments (75.2% and 71.0%, respectively); while on day 8, the 2 mg / L and 4 mg / L groups had high removal rates, with the 4 mg / L treatment achieving a removal rate of 87.7%. Furthermore, a selenium concentration of 8 mg / L may exceed the tolerance range of GX03, resulting in a lower removal rate. Therefore, the optimal selenium concentration for selenium removal / conversion is below 8 mg / L, preferably below 4 mg / L, and more preferably 2–4 mg / L. Simultaneously, this algae may have the potential to convert selenium into organoselenium for the production of organic selenium supplements.

[0046] The preferred embodiments of this invention have been described in detail, but it should be understood that the technical solutions of this invention are not limited to the specific implementation details described above. Under the guidance of the technical concept of this invention, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the protection scope of this invention.

Claims

1. The application of a microalga in the removal of selenium from water, characterized by: The microalgae mentioned is called *Algae spp.* Coelastrum sp.) GX03, accession number CCTCC NO: M20241314, accession date June 20, 2024, deposited at the China Center for Type Culture Collection, Wuhan University, Wuhan, China.

2. The application of microalgae in removing selenium from water according to claim 1, characterized in that... The process includes the following steps: adding microalgae strains or microalgae solutions to selenium-polluted water for cultivation.

3. The application of microalgae in removing selenium from water according to claim 2, characterized in that: The microalgae solution mentioned is an algae solution cultured to the logarithmic growth phase or the stationary phase.

4. The application of microalgae in removing selenium from water according to claim 3, characterized in that: The microalgae solution is obtained through the following steps: inoculating microalgae into a culture medium and culturing them to the logarithmic growth phase or the stationary phase.

5. The application of microalgae in removing selenium from water according to claim 4, characterized in that: The cultivation conditions are as follows: 25-30℃, light intensity of 10000-12000 lux, and light-dark time of 10-14h.

6. The application of microalgae in removing selenium from water according to claim 4, characterized in that: The culture medium is TAP liquid medium.

7. The application of microalgae in removing selenium from water according to claim 2, characterized in that: The amount of microalgae species or microalgae solution added is based on the OD of algal cells in the water. 680 Calculated as 0.

1.

8. The application of the microalgae according to any one of claims 1 to 7 in the removal of selenium from water, characterized in that: The selenium mentioned is inorganic selenium.

9. The application of microalgae in removing selenium from water according to claim 8, characterized in that: The selenium mentioned is sodium selenite.

10. The application of microalgae in removing selenium from water according to claim 9, characterized in that: The selenium concentration in selenium-polluted water bodies is below 8 mg / L.

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