Escherichia coli coated calcium carbonate composite powder, block and preparation method thereof

Abstract

The application discloses an Escherichia coli coated calcium carbonate composite material powder, a block and a preparation method thereof. The preparation method comprises the following steps: mixing and stirring natural Escherichia coli expressing GFP and a buffer solution containing calcium ions to obtain a suspension; adding an aqueous solution containing carbonate ions into the suspension, and after the adding is completed, centrifuging, washing and drying to obtain the Escherichia coli coated calcium carbonate composite material powder. The application effectively combines the natural Escherichia coli expressing GFP and calcium ions to inhibit the crystal type conversion, and after the titration is completed, the centrifugation and washing are rapidly performed, so that the single vaterite powder with stable crystal type is successfully prepared, and then the composite material block is prepared through a cold sintering process. The operation method is simple, the cost is low, and the application is suitable for large-scale production, so that a new research idea is provided for preparing a large-size heterogeneous composite material which can realize the synergistic improvement of strength and toughness and has a macroscopic geometric shape.

Description

Technical Field

[0001] This invention relates to the field of biomimetic composite materials technology, and in particular to a powder, bulk, and preparation method of Escherichia coli-coated calcium carbonate composite material. Background Technology

[0002] With historical development and technological progress, the requirements for structural materials in various engineering fields have become increasingly stringent, such as low density, high strength, high hardness, and toughness. However, among these properties, strength and toughness are often mutually exclusive. Ceramic materials, the most representative example, are widely used in engineering structural materials, but their high density and low toughness are significant limitations. Therefore, lightweight natural biomaterials have attracted widespread attention from researchers, especially biomaterials such as bones, teeth, and shells. Although composed of brittle minerals and organic polymers or nanoparticles, these materials possess high strength and toughness. However, most of the novel shell-like reinforced materials currently prepared are small in size, making industrial production difficult, and most biomimetic structural materials still do not satisfactorily achieve a variety of superior properties. Therefore, inspired by the growth process of heterogeneous structures in biomaterials, there is a desire to prepare biomimetic composite materials with large size and synergistically enhanced mechanical and functional properties.

[0003] In biomineral materials, the inorganic mineral component mainly consists of crystals formed from common compounds such as calcium carbonate, calcium phosphate, and silicon dioxide. Calcium carbonate includes three crystal forms, with aragonite being the least stable. However, the microstructure of aragonite, consisting of spherical particles clustered together at approximately 50 nm, is advantageous for subsequent bulk preparation studies. However, current domestic research, without additives to inhibit crystal transformation, shows that pure aragonite particles prepared via co-precipitation react with low concentrations (10-20 mM) of calcium and carbonate ions, hindering large-scale preparation of aragonite powder. Calcium carbonate prepared using high concentrations (≥50 mM) of calcium ions and carbonate typically exhibits both aragonite and calcite crystal forms, resulting in lower purity.

[0004] Therefore, it is urgent to improve the existing preparation methods to achieve large-scale preparation of pure spherical aragonite-type calcium carbonate and obtain heterogeneous composite materials with macroscopic geometry that synergistically achieve high strength and high toughness. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose an Escherichia coli-coated calcium carbonate composite material powder, bulk material and its preparation method, which solves the technical problems that the pure spheroidal aragonite type calcium carbonate powder often cannot be prepared on a large scale due to the low concentration, and that existing biomimetic structural materials cannot achieve a synergistic improvement in large size, high strength and high toughness.

[0006] In a first aspect, the present invention provides a method for preparing Escherichia coli-coated calcium carbonate composite material powder, comprising the following steps:

[0007] Provide a calcium-containing buffer solution, an aqueous solution containing carbonate ions, and native E. coli expressing GFP;

[0008] Naturally expressed GFP E. coli was mixed with a calcium-containing buffer solution to obtain a suspension;

[0009] An aqueous solution containing carbonate ions was added dropwise to the suspension. After the addition was complete, the mixture was centrifuged, washed, and dried to obtain E. coli-coated calcium carbonate composite material powder.

[0010] In a second aspect, the present invention provides an Escherichia coli-coated calcium carbonate composite material powder, which is obtained by the preparation method of the Escherichia coli-coated calcium carbonate composite material powder provided in the first aspect of the present invention.

[0011] Thirdly, the present invention provides a method for preparing Escherichia coli-coated calcium carbonate composite material blocks, comprising the following steps:

[0012] Escherichia coli-coated calcium carbonate composite material powder was used to obtain Escherichia coli-coated calcium carbonate composite material blocks through a cold sintering process; wherein the sintering temperature was 37~250℃, the holding time was 2~3h, the heating rate was 5~10℃ / min, and the applied pressure was 500~700MPa.

[0013] Fourthly, the present invention provides an Escherichia coli-coated calcium carbonate composite material block, which is obtained by the preparation method of the Escherichia coli-coated calcium carbonate composite material block provided in the third aspect of the present invention.

[0014] Compared with the prior art, the beneficial effects of the present invention include:

[0015] This invention effectively blocks the crystal transformation by utilizing the strong interaction between naturally occurring GFP-expressing *E. coli* and calcium ions. Following carbonate titration, rapid centrifugation and washing successfully prepares stable and uniform spherulite powder. This powder is then cold-sintered to produce fluorescent composite material blocks. This invention is simple to operate, low-cost, suitable for large-scale production, and has a wide range of applications. It provides a new research approach for preparing large-scale heterogeneous composite materials with synergistic improvements in strength and toughness and unique macroscopic geometries. Attached Figure Description

[0016] Figure 1These are X-ray electron diffraction patterns of CaCO3@E. coli powder prepared under different theoretical concentrations of calcium ions and carbonate ions after mixing in Examples 1-4 of this invention.

[0017] Figure 2 This is the X-ray electron diffraction pattern of the CaCO3@E. coli powder prepared in Comparative Example 1 of this invention;

[0018] Figure 3 These are X-ray electron diffraction patterns of CaCO3@E. coli composite material blocks prepared at different heating temperatures in Examples 1 and 5-9 of this invention;

[0019] Figure 4 These are X-ray electron diffraction patterns of pure calcium carbonate material blocks prepared at different heating temperatures in Comparative Examples 2-6 of this invention;

[0020] Figure 5 These are scanning electron microscope images of CaCO3@E. coli composite material blocks prepared at different heating temperatures in Examples 1 and 5-9 of this invention;

[0021] Figure 6 These are flexural strength diagrams of CaCO3@E. coli composite material blocks prepared at different heating temperatures in Examples 1 and 5-9 of this invention, and pure calcium carbonate material blocks prepared in Comparative Example 3;

[0022] Figure 7 These are fracture toughness diagrams of the CaCO3@E. coli composite material block prepared in Example 6 of this invention and the pure calcium carbonate material block prepared in Comparative Example 3. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0024] In a first aspect, the present invention provides a method for preparing Escherichia coli-coated calcium carbonate composite material powder, comprising the following steps:

[0025] S1. Provide a calcium-containing buffer solution, an aqueous solution containing carbonate ions, and native E. coli (E. coli / GFP) that has expressed GFP.

[0026] S2. Mix and stir the naturally expressed GFP E. coli with a calcium-containing buffer solution to obtain a suspension;

[0027] S3. An aqueous solution containing carbonate ions is added dropwise to the suspension. After the addition is complete, the mixture is centrifuged, washed, and dried to obtain Escherichia coli-coated calcium carbonate (CaCO3@E. coli) composite powder.

[0028] In this embodiment, in step S1, the calcium ions in the calcium-containing buffer solution are derived from at least one of calcium chloride and calcium nitrate.

[0029] In this embodiment, in step S1, the concentration of calcium ions in the calcium ion-containing buffer solution is 0.02~0.1mol / L.

[0030] In this embodiment, in step S1, the calcium-containing buffer solution also includes N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (hepes), and the concentration of hepes is 0.01~0.03 mol / L.

[0031] In this embodiment, in step S1, the pH of the calcium ion-containing buffer solution is 6.9~7.1, and more specifically 7.

[0032] In this embodiment, in step S1, the carbonate ions in the aqueous solution containing carbonate ions originate from sodium carbonate.

[0033] In this embodiment, in step S1, the concentration of carbonate ions in the aqueous solution containing carbonate ions is 0.02~0.1mol / L.

[0034] In this embodiment, in step S1, the aqueous solution containing carbonate ions also includes sodium chloride, and the concentration of sodium chloride is 0.09~0.11 mol / L. This invention maintains the pH of the system at neutral by introducing sodium chloride.

[0035] In this embodiment, the volume ratio of the calcium ion-containing buffer solution to the carbonate ion-containing aqueous solution is 1:(0.9~1.1).

[0036] In this embodiment, the volume of the aqueous solution containing carbonate ions is 25~50mL.

[0037] In this embodiment, in step S1, the number of naturally occurring E. coli expressing GFP is 10. 9 indivual.

[0038] In this embodiment, step S1, the culture process of E. coli that naturally expresses GFP includes:

[0039] The first naturally expressed GFP E. coli, the first Kana antibiotic, and the first LB sterile solution were mixed and subjected to the first shaker reaction to obtain the first product;

[0040] Add the second LB sterile solution and the second Kana antibiotic to the first product, and carry out a second shaker reaction to obtain the second product;

[0041] IPTG antibiotic was added to the second product, and a third shaker reaction was carried out. Then, by centrifugation and washing, a second natural E. coli expressing GFP was obtained.

[0042] In this invention, by adding the antibiotic kana during the culture of naturally expressed GFP Escherichia coli, the growth and reproduction of other bacterial species can be inhibited, resulting in the generation of more Escherichia coli; by adding the antibiotic IPTG, it can be made to have fluorescent properties.

[0043] The concentrations of the first LB sterile solution and the second LB sterile solution were both 20-30 g / L, and further 25 g / L.

[0044] The concentrations of both the first and second kana antibiotics were 40–60 μg / mL.

[0045] The volume ratio of the first LB sterile solution to the first kana antibiotic is (1000~1200):1.

[0046] During the first shaker reaction, the temperature was 37℃, the time was 12~14h, and the shaker speed was 200~250rpm.

[0047] The volume ratio of the first LB sterile solution to the second LB sterile solution and the second kana antibiotic is (50~60):(2800~3200):1.

[0048] During the second shaker reaction, the temperature was 37℃, the time was 2-4 hours, and the shaker speed was 200-250 rpm.

[0049] The concentration of IPTG antibiotics is 0.4~0.6mM.

[0050] The volume ratio of the first LB sterile solution to the IPTG antibiotic is (15~20):1.

[0051] During the third shaking reaction, the temperature was 37℃, the time was 2-4 hours, and the shaking speed was 200-250 rpm.

[0052] In this embodiment, in step S2, the mixing temperature is room temperature, the mixing time is 0.5~1.5h, and the mixing speed is 400~450rpm.

[0053] In this embodiment, in step S3, the temperature of the drop is room temperature, and the dropping rate is 2.5~3.5 mL / min.

[0054] In this embodiment, the drying method in step S3 is freeze drying.

[0055] The freeze-drying temperature is -50 to -40 ℃, and the time is 12 to 24 h.

[0056] In a second aspect, the present invention provides an Escherichia coli-coated calcium carbonate composite material powder, which is obtained by the preparation method of the Escherichia coli-coated calcium carbonate composite material powder provided in the first aspect of the present invention.

[0057] Thirdly, the present invention provides a method for preparing Escherichia coli-coated calcium carbonate composite material blocks, comprising the following steps:

[0058] Escherichia coli-coated calcium carbonate composite material powder was used to obtain Escherichia coli-coated calcium carbonate composite material blocks through a cold sintering process.

[0059] In this embodiment, the sintering temperature is 37~250℃, including but not limited to 37℃, 75℃, 150℃, 200℃, 250℃, etc., the holding time is 2~3h, the heating rate is 5~10℃ / min, and the applied pressure is 500~700MPa.

[0060] Fourthly, the present invention provides an Escherichia coli-coated calcium carbonate composite material block, which is obtained by the preparation method of the Escherichia coli-coated calcium carbonate composite material block provided in the third aspect of the present invention.

[0061] Example 1

[0062] (1) Weigh 0.5549 g of calcium chloride and 0.238 g of hepes using an electronic balance and dissolve them in 50 mL of deionized water. Stir at 450 rpm for 10 min to ensure the solids are fully and evenly dissolved. Adjust the pH of the system to 7 using a 2 M NaOH solution to prepare a CaCl2 / hepes mixed aqueous solution. Weigh 0.5307 g of sodium carbonate and 0.29 g of sodium chloride and dissolve them in 50 mL of deionized water. Stir at 450 rpm for 10 min to ensure the solids are fully and evenly dissolved to prepare a NaCO3 / NaCl mixed aqueous solution.

[0063] (2) At room temperature, 25g of LB broth (LB) was weighed using an electronic balance and dissolved in 1L of deionized water. The solution was stirred at 350 rpm for 15 min and then poured into 300mL, 300mL, 300mL, and 100mL conical flasks, respectively. The solution was then sterilized to obtain sterile LB solution. After the sterile LB solution cooled, 100mL of the sterile LB solution was poured into three 15mL centrifuge tubes (5-6mL capacity). A small amount of E. coli / GFP bacteria and 5μL of kana antibiotic (50μg / mL concentration) were added to each of the three centrifuge tubes. The mixture was then reacted on a shaker for 12 h (shaker speed 220rpm, temperature 37℃). The mixture was then poured into the three conical flasks and 100μL of kana antibiotic was added to each flask. Kana antibiotic (50 μg / mL) was added and reacted on a shaker under the same conditions for about 3 hours until obvious bacterial growth was observed. Then, 300 μL of IPTG antibiotic (0.5 mM) was added, and the mixture was reacted on a shaker for another 3 hours. The bacteria were then collected by centrifugation. After washing three times with deionized water, E. coli / GFP-IPTG strains were obtained. It was calculated that each Erlenmeyer flask contained approximately 10 E. coli / GFP-IPTG strains. 9 indivual.

[0064] (3) At room temperature, E. coli / GFP-IPTG strain (10 9 The solution was poured into 50 mL of a CaCl2 / E. coli mixed aqueous solution and stirred at 450 rpm for 1 h to obtain a CaCl2 / E. coli-E. coli suspension. 50 mL of a NaCO3 / NaCl mixed aqueous solution was added dropwise to the CaCl2 / E. coli-E. coli suspension at a rate of 2.5 mL / min at room temperature. During the titration, the solution was stirred at a constant speed until white flocculent particles appeared. This process continued until the NaCO3 / NaCl mixed aqueous solution was completely added, resulting in a precipitate dispersion. The precipitate dispersion was rapidly centrifuged, washed five times with deionized water, and freeze-dried to obtain CaCO3@E. coli composite powder. The freeze-drying temperature was -50 to -40 °C, and the time was 16 h.

[0065] (4) The CaCO3@E. coli composite powder was heated at 37℃ and subjected to a pressure of 700MPa simultaneously for 2h, with a heating rate of 10℃ / min, to obtain CaCO3@E. coli composite block.

[0066] Example 2

[0067] Compared with Example 1, the only difference is that step (1) is adjusted as follows:

[0068] (1) Weigh 0.27745g of calcium chloride and 0.119g of hepes using an electronic balance and dissolve them in 25mL of deionized water. Stir at 450rpm for 10min to ensure the solids are fully and uniformly dissolved. Adjust the pH of the system to 7 using a 2M NaOH solution to prepare a CaCl2 / hepes mixed aqueous solution. Weigh 0.26535g of sodium carbonate and 0.145g of sodium chloride and dissolve them in 25mL of deionized water. Stir at 450rpm for 10min to ensure the solids are fully and uniformly dissolved to prepare a NaCO3 / NaCl mixed aqueous solution.

[0069] Example 3

[0070] Compared with Example 1, the only difference is that step (1) is adjusted as follows:

[0071] (1) Weigh 0.11098g of calcium chloride and 0.119g of hepes using an electronic balance and dissolve them in 25mL of deionized water. Stir at 450rpm for 10min to ensure the solids are fully and uniformly dissolved. Adjust the pH of the system to 7 using a 2M NaOH solution to prepare a CaCl2 / hepes mixed aqueous solution. Weigh 0.10614g of sodium carbonate and 0.145g of sodium chloride and dissolve them in 25mL of deionized water. Stir at 450rpm for 10min to ensure the solids are fully and uniformly dissolved to prepare a NaCO3 / NaCl mixed aqueous solution.

[0072] Example 4

[0073] Compared with Example 1, the only difference is that step (1) is adjusted as follows:

[0074] (1) Weigh 0.05549 g of calcium chloride and 0.119 g of hepes using an electronic balance and dissolve them in 25 mL of deionized water. Stir at 450 rpm for 10 min to ensure the solids are fully and evenly dissolved. Adjust the pH of the system to 7 using a 2 M NaOH solution to prepare a CaCl2 / hepes mixed aqueous solution. Weigh 0.05307 g of sodium carbonate and 0.145 g of sodium chloride and dissolve them in 25 mL of deionized water. Stir at 450 rpm for 10 min to ensure the solids are fully and evenly dissolved to prepare a NaCO3 / NaCl mixed aqueous solution.

[0075] Example 5

[0076] Compared with Example 1, the only difference is that step (4) is adjusted as follows:

[0077] (4) The CaCO3@E. coli composite powder was heated at 75℃ and subjected to a pressure of 700MPa simultaneously for 2h, with a heating rate of 10℃ / min, to obtain CaCO3@E. coli composite block.

[0078] Example 6

[0079] Compared with Example 1, the only difference is that step (4) is adjusted as follows:

[0080] (4) The CaCO3@E. coli composite powder was heated at 100℃ and subjected to a pressure of 700MPa simultaneously for 2h, with a heating rate of 10℃ / min, to obtain CaCO3@E. coli composite block.

[0081] Example 7

[0082] Compared with Example 1, the only difference is that step (4) is adjusted as follows:

[0083] (4) The CaCO3@E. coli composite powder was heated at 150℃ and subjected to a pressure of 700MPa simultaneously for 2 hours. The heating rate was 10℃ / min to obtain CaCO3@E. coli composite block.

[0084] Example 8

[0085] Compared with Example 1, the only difference is that step (4) is adjusted as follows:

[0086] (4) The CaCO3@E. coli composite powder was heated at 200℃ and subjected to a pressure of 700MPa simultaneously for 2h, with a heating rate of 10℃ / min, to obtain the CaCO3@E. coli bulk composite material.

[0087] Example 9

[0088] Compared with Example 1, the only difference is that step (4) is adjusted as follows:

[0089] (4) The CaCO3@E. coli composite powder was heated at 250℃ and subjected to a pressure of 700MPa simultaneously for 2h, with a heating rate of 10℃ / min, to obtain CaCO3@E. coli composite block.

[0090] Comparative Example 1

[0091] Compared with Example 1, the only difference is that in step (3), after the addition is completed, the mixture is stirred at a constant speed of 450 rpm for 12 hours to obtain a precipitate dispersion.

[0092] Comparative Example 2

[0093] Compared with Example 1, the only difference is that in step (3), E. coli / GFP-IPTG strain was not used, and pure calcium carbonate powder was prepared directly using CaCl2 / hepes mixed aqueous solution and NaCO3 / NaCl mixed aqueous solution (heating temperature 37℃).

[0094] Comparative Example 3

[0095] Compared with Example 6, the only difference is that in step (3), E. coli / GFP-IPTG strain was not used, and pure calcium carbonate powder was prepared directly using CaCl2 / hepes mixed aqueous solution and NaCO3 / NaCl mixed aqueous solution (heating temperature 100℃).

[0096] Comparative Example 4

[0097] Compared with Example 7, the only difference is that in step (3), E. coli / GFP-IPTG strain was not used, and pure calcium carbonate was prepared directly using CaCl2 / hepes mixed aqueous solution and NaCO3 / NaCl mixed aqueous solution (heating temperature 150℃).

[0098] Comparative Example 5

[0099] Compared with Example 8, the only difference is that in step (3), E. coli / GFP-IPTG strain was not used, and pure calcium carbonate powder was prepared directly using CaCl2 / hepes mixed aqueous solution and NaCO3 / NaCl mixed aqueous solution (heating temperature 200℃).

[0100] Comparative Example 6

[0101] Compared with Example 9, the only difference is that in step (3), E. coli / GFP-IPTG strain was not used, and pure calcium carbonate powder was prepared directly using CaCl2 / hepes mixed aqueous solution and NaCO3 / NaCl mixed aqueous solution (heating temperature 250℃).

[0102] experimental group

[0103] XRD tests were performed on the CaCO3@E. coli composite powders prepared in Examples 1-4 and Comparative Example 1. The test results are shown in the figure. Figure 1 and 2 .

[0104] XRD tests were performed on the CaCO3@E. coli composite material blocks prepared in Examples 1, 5-9 and the pure calcium carbonate material blocks prepared in Comparative Examples 2-6. The test results are shown in [Figure 1]. Figure 3 and 4 .

[0105] SEM tests were performed on the CaCO3@E. coli composite material blocks prepared in Examples 1 and 5-9 above. The test results are shown in [Figure 1]. Figure 5 .

[0106] The flexural strength of the CaCO3@E. coli composite material blocks prepared in Examples 1 and 5-9 above, as well as the pure calcium carbonate material block prepared in Comparative Example 3, was tested. The test results are shown in [Figure 1]. Figure 6 .

[0107] Fracture toughness tests (single-sided notched beam) were performed on the CaCO3@E. coli composite material block prepared in Example 6 and the pure calcium carbonate material block prepared in Comparative Example 3. The test results are shown in […]. Figure 7 .

[0108] Please see Figure 1 ,pass Figure 1 It can be seen that Examples 1-4 of the present invention can all achieve the successful preparation of pure spheroidal aragonite particles, indicating that when the solution volume is 50 mL, the method of the present invention (centrifugation directly after titration) can obtain stable pure spheroidal aragonite crystals in the range of calcium ion and carbonate concentrations of 10-50 mM. Furthermore, no crystal transformation occurred when the solution volume was doubled, indicating that the process of the present invention is stable and suitable for large-scale production.

[0109] Please see Figure 2 ,pass Figure 2 It can be seen that after complete titration, continuing to stir for 12 hours will cause some crystals to transform into calcite. This also shows that the process parameters of the present invention can prepare pure spheroidal calcium carbonate with stable crystal form and in a shorter time.

[0110] Please see Figures 3-4 ,pass Figures 3-4 It can be seen that temperature and pressure both affect the crystal transformation of aragonite, but the degree of crystal transformation is greatly reduced under the influence of E. coli / GFP.

[0111] Please see Figure 5 ,pass Figure 5 It can be seen that at a heating temperature of 37℃, rod-shaped pores left by E. coli still exist. However, as the heating temperature increases, the block becomes denser, and the remaining pores deform and disappear.

[0112] Please see Figure 6 ,pass Figure 6It can be seen that the block prepared by the method of the present invention at a heating temperature of 100℃ has the highest bending strength, and the CaCO3@E. coli composite block of the present invention has a higher bending strength than the pure calcium carbonate material block, indicating that the addition of E. coli / GFP leads to a significant improvement in the mechanical properties of the composite material.

[0113] Please see Figure 7 ,pass Figure 7 It can be seen that with the incorporation of E. coli / GFP, the interfacial interaction between E. coli and CaCO3 leads to crack deflection, which significantly improves its toughness.

[0114] In summary, this invention effectively blocks calcite formation through the strong interaction between E. coli / GFP and CaCO3, and inhibits calcite formation by rapid centrifugation and washing after titration, resulting in spherical aragonite powder composed of nanoparticles. The synthesis process uses only calcium source and carbonate ions, along with a sodium chloride solution to maintain neutrality; no other surfactants, directing agents, templates, or other organic substances are required, resulting in a high-purity product free of impurities. Furthermore, the absence of a stirring step after titration significantly shortens production time, reduces costs, and improves efficiency. This invention is simple to operate, low-cost, suitable for large-scale production, and has a wide range of applications, providing a new research approach for novel biomimetic materials.

[0115] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing an E. coli-coated calcium carbonate composite powder, characterized by, Includes the following steps: Provide a calcium-containing buffer solution, an aqueous solution containing carbonate ions, and E. coli expressing GFP; The GFP-expressing E. coli and the calcium-containing buffer solution were mixed and stirred to obtain a suspension; The aqueous solution containing carbonate ions was added dropwise to the suspension. After the addition was complete, the mixture was centrifuged, washed, and dried to obtain E. coli-coated calcium carbonate composite material powder. The concentration of calcium ions in the calcium ion-containing buffer solution is 0.02~0.1 mol / L; The calcium-containing buffer solution further includes N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid, and the concentration of N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid is 0.01~0.03 mol / L; The pH of the calcium-containing buffer solution is 6.9~7.1; The concentration of carbonate ions in the aqueous solution is 0.02~0.1 mol / L. The volume ratio of the calcium-containing buffer solution to the carbonate-containing aqueous solution is 1:(0.9~1.1). The temperature at which the drops are added is room temperature, and the rate of addition is 2.5~3.5 mL / min.

2. The method for preparing Escherichia coli-coated calcium carbonate composite material powder according to claim 1, characterized in that, In the calcium-containing buffer solution, the calcium ions are derived from at least one of calcium chloride and calcium nitrate.

3. The method for preparing Escherichia coli-coated calcium carbonate composite material powder according to claim 1, characterized in that, In the aqueous solution containing carbonate ions, the carbonate ions are derived from sodium carbonate.

4. The method for preparing Escherichia coli-coated calcium carbonate composite material powder according to claim 1, characterized in that, The aqueous solution containing carbonate ions also includes sodium chloride, and the concentration of sodium chloride is 0.09~0.11 mol / L.

5. The method for preparing Escherichia coli-coated calcium carbonate composite material powder according to claim 1, characterized in that, The volume of the aqueous solution containing carbonate ions is 25-50 mL; and / or, The number of the E. coli expressing GFP is 10 9 individuals.

6. The method for preparing Escherichia coli-coated calcium carbonate composite material powder according to claim 1, characterized in that, The culture process of the E. coli expressing GFP includes: The first E. coli expressing GFP, the first Kana antibiotic, and the first LB sterile solution were mixed and subjected to the first shaker reaction to obtain the first product; Add a second LB sterile solution and a second Kana antibiotic to the first product, and perform a second shaker reaction to obtain a second product; IPTG antibiotic was added to the second product, and a third shaker reaction was performed. Following centrifugation and washing, a second E. coli strain expressing GFP was obtained. The concentrations of both the first LB sterile solution and the second LB sterile solution are 20-30 g / L; and / or, The concentrations of both the first and second kana antibiotics are 40–60 μg / mL; and / or, The concentration of the IPTG antibiotic is 0.4~0.6 mM; and / or, The volume ratio of the first LB sterile solution to the first Kana antibiotic is (1000~1200):1; and / or, The volume ratio of the first LB sterile solution to the second LB sterile solution and the second Kana antibiotic is (50~60):(2800~3200):1; and / or, The volume ratio of the first LB sterile solution to IPTG antibiotic is (15~20):1; and / or, During the first shaker reaction, the temperature was 37°C, the time was 12-14 hours, and the shaker speed was 200-250 rpm; and / or, During the second shaker reaction, the temperature is 37℃, the time is 2~4 hours, and the shaker speed is 200~250 rpm; and / or, During the reaction process in the third shaking table, the temperature is 37℃, the time is 2~4h, and the shaking table speed is 200~250rpm.

7. The method for preparing Escherichia coli-coated calcium carbonate composite material powder according to claim 1, characterized in that, The mixing temperature is room temperature, the mixing time is 0.5~1.5h, and the mixing speed is 400~450rpm.

8. A calcium carbonate composite material powder coated with Escherichia coli, characterized in that, The Escherichia coli-coated calcium carbonate composite material powder is obtained by the preparation method of the Escherichia coli-coated calcium carbonate composite material powder according to any one of claims 1 to 7.

9. A method for preparing Escherichia coli-coated calcium carbonate composite material blocks, characterized in that, Includes the following steps: The Escherichia coli-coated calcium carbonate composite material powder of claim 8 is subjected to a cold sintering process to obtain Escherichia coli-coated calcium carbonate composite material blocks; wherein... The sintering temperature is 37~250℃, the holding time is 2~3h, the heating rate is 5~10℃ / min, and the applied pressure is 500~700MPa.

10. A block of calcium carbonate composite material coated with Escherichia coli, characterized in that, The Escherichia coli-coated calcium carbonate composite material block is obtained by the preparation method of the Escherichia coli-coated calcium carbonate composite material block according to claim 9.

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