A method for preparing a tobacco stem extract and its use as a microbial corrosion inhibitor

Abstract

The application discloses a preparation method of tobacco stem extract and application of the tobacco stem extract as a microbial corrosion inhibitor, and belongs to the field of metal microbial corrosion and protection. The preparation method comprises the following steps: cleaning collected tobacco stems, airing the tobacco stems, grinding the tobacco stems into powder to obtain tobacco stem powder, dispersing the tobacco stem powder in an ethanol aqueous solution, soaking, filtering the solution, concentrating the filtrate, and drying to obtain the tobacco stem extract. Through antibacterial and corrosion characterization experiments, it is proved that when the concentration of the tobacco stem extract reaches 200 mg / L, the tobacco stem extract can realize broad-spectrum antibacterial effect on gram-negative bacteria and gram-positive bacteria, effectively inhibit the initial adhesion of microorganisms on the metal surface, eliminate the formed mature biofilm, and has obvious inhibition effect on microbial corrosion. The raw material of the tobacco stem extract is cheap and easy to obtain, the preparation method is simple, the process is green and environment-friendly, the antibacterial and corrosion inhibition effect is remarkable, and the efficient prevention and control of microbial corrosion of metal materials in the environment can be realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metal microbiologically influenced corrosion and protection, and particularly relates to a preparation method of tobacco stem extract and application thereof as a microbiologically influenced corrosion inhibitor. BACKGROUND

[0002] Microbiologically influenced corrosion (MIC) refers to metal corrosion related to the action of microorganisms existing in the corrosion system. It is reported that the economic loss caused by MIC accounts for more than 20% of the total corrosion loss, among which nearly 40% of internal corrosion and 30% of external corrosion in oil and gas pipelines are related to MIC. Sulfate-reducing bacteria are one of the main microorganisms causing MIC. The biofilm formed by microorganisms on the material surface can significantly change the physical and chemical environment around it, including the content of dissolved oxygen, ion concentration and pH value, etc. This change, together with the extracellular electron transfer function of microorganisms, together causes the acceleration of material corrosion. In view of this problem, researchers have proposed various prevention and control strategies, among which dispersing the biofilm to inhibit MIC has been proved to have significant effect.

[0003] Current technologies for dispersing biofilm mainly focus on two directions: material surface modification and bactericide development. In the field of material surface modification, although technologies such as enzyme treatment, chemical modification and morphology control can delay the aggregation of biofilm, there are problems such as complex process and high cost. Compared with the above, adding bactericide is still the preferred protection method in the industry due to its simple operation and high efficiency. However, the application of traditional bactericides also has its limitations: narrow antibacterial spectrum (only effective against single gram-negative / positive bacteria), environmental accumulation risk (environmental pollution) and single functionality. Based on the above technical status, there is an urgent need in the field to develop a new type of green bactericide, which should have the following characteristics: (1) using renewable natural resources as raw materials to ensure environmental friendliness; (2) having broad-spectrum bactericidal properties, capable of killing both gram-positive and gram-negative microorganisms; (3) strong resistance to environmental interference, stable in various complex working conditions (aerobic / anaerobic); (4) having both bactericidal and corrosion inhibition functions.

[0004] Tobacco stem, as a byproduct of tobacco processing, is rich in active ingredients such as polyphenols and alkaloids, and can kill microorganisms. The characteristic groups in its molecular structure, such as aromatic ring, oxygen-containing functional group and nitrogen heterocycle, provide an ideal precursor for constructing corrosion inhibitor molecules with both chemical adsorption and hydrophobic anchoring functions. By extracting active ingredients from tobacco stems to prepare a microbiologically influenced corrosion inhibitor, the functions of bactericidal corrosion inhibition and high-value utilization of agricultural and forestry waste can be realized at the same time. However, there is currently no report on the application of active substances extracted from tobacco stems to the prevention of microbiologically influenced corrosion. SUMMARY

[0005] The application aims to provide a preparation method of tobacco stem extract with simple process and low cost and application of the tobacco stem extract as a microbial corrosion inhibitor.

[0006] The preparation method of the tobacco stem extract comprises the following steps:

[0007] Step 1: washing collected tobacco stems and then air-drying;

[0008] Step 2: grinding the air-dried tobacco stems into powder to obtain tobacco stem powder;

[0009] Step 3: dispersing the tobacco stem powder in an ethanol aqueous solution and soaking for 2-3 hours;

[0010] Step 4: filtering the solution and concentrating the filtrate;

[0011] Step 5: drying the obtained concentrate to obtain the tobacco stem extract.

[0012] Further, in the step 3, the volume fraction of ethanol in the ethanol aqueous solution is 40%-50%.

[0013] Further, in the step 5, the concentrate is dried in an oven at 45-55°C for 2-3 days to obtain the tobacco stem extract.

[0014] The tobacco stem extract has a microbial corrosion inhibition effect and can be applied as a microbial corrosion inhibitor. The specific application method comprises:

[0015] Step 1: mixing the tobacco stem extract with an ethanol aqueous solution to form an ethanol aqueous solution of the tobacco stem extract as a microbial corrosion inhibitor;

[0016] Step 2: applying the microbial corrosion inhibitor to a microbial corrosion environment to achieve the purpose of microbial corrosion inhibition.

[0017] Further, the volume fraction of ethanol in the ethanol aqueous solution is 40%-60%, and the mass concentration of the tobacco stem extract in the ethanol aqueous solution is 0.2-10 g / L.

[0018] Further, the microbial corrosion environment includes soil environment, atmospheric environment and marine environment. The tobacco stem extract can reduce microbial activity in the microbial corrosion environment, inhibit microbial adhesion to the surface of metal materials, kill mature biofilms and inhibit microbial corrosion of metals.

[0019] Furthermore, step 2 includes the following steps: adding the tobacco stem extract of the present invention to anaerobic Gram-negative bacterial suspension containing metal material and aerobic Gram-positive bacterial suspension for co-culture to complete the microbial corrosion inhibition experiment.

[0020] Furthermore, the metal material is selected from carbon steel and stainless steel, preferably Cu-Cr steel, X80 steel and 316L stainless steel.

[0021] Furthermore, the Gram-negative bacteria are sulfate-reducing bacteria, specifically *Desulfovibriovulgaris* (ATCC 7757), and the Gram-positive bacteria are *Bacillus licheniformis* (ATCC 14580).

[0022] This invention verifies the corrosion inhibition performance of tobacco stem extract through comparative experiments. The experiment employed a parallel control design, setting up an experimental group with added tobacco stem extract and a blank control group without any inhibitors under the same environmental conditions. Test results show that the presence of tobacco stem extract in the system significantly reduces the microbial corrosion rate of metallic materials, acting as a corrosion inhibitor with an inhibition efficiency exceeding 98%.

[0023] The beneficial effects of this invention are:

[0024] 1. The preparation process of this invention is simple, efficient, and cost-effective: The preparation process of tobacco stem extract used in this invention can be completed at room temperature, without the need for complex equipment or harsh reaction conditions. Furthermore, the raw materials are widely available and inexpensive, giving it a significant advantage for industrial-scale production.

[0025] 2. Outstanding environmental friendliness: Using tobacco processing waste as raw material, the extraction process adopts a green solvent system, realizing resource recycling.

[0026] 3. Excellent corrosion inhibition performance: Nicotine active molecules in tobacco stem extract can form a dense protective film on the metal surface through chemical adsorption, achieving a corrosion inhibition efficiency of 85% for carbon steel in 10g / L NaCl solution.

[0027] 4. Significant biofilm inhibition ability: The active substances in tobacco stem extract can penetrate the cell membrane and enter microbial cells, destroying cell structure, leading to cell death, and inhibiting biofilm formation. Experiments have confirmed that 200 mg / L tobacco stem extract can completely inhibit biofilm formation and kill more than 90% of the existing biofilm.

[0028] 5. Broad-spectrum antibacterial activity: At a low concentration of 200 mg / L, it showed significant antibacterial effects against both Desulfovibrio (Gram-negative) and Bacillus licheniformis (Gram-positive), solving the problem of narrow antibacterial spectrum of traditional bactericides. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the embodiments. All experimental reagents used in the following embodiments are conventional biochemical reagents. All experiments in the embodiments were repeated at least three times to ensure the reproducibility of the experimental results.

[0030] In the following examples, the preparation process of the tobacco stem extract solution as a microbial corrosion inhibitor is as follows: first, tobacco stem extract is prepared, and then it is mixed with 50% ethanol aqueous solution to prepare a tobacco stem extract solution with a mass concentration of 10.0 g / L.

[0031] In the following examples, the corrosion materials used were Cu-Cr steel, X80 steel, and 316L stainless steel. The Cu-Cr steel chemical composition (mass percentage): 0.25% C, 0.6% Cu, 0.6% Ni, 2.0% Cr, 0.25% Mo, with Fe as the balance. The X80 carbon steel chemical composition (mass percentage): 0.07% C, 1.82% Mn, 0.19% Si, 0.045% S, 0.045% P, 0.17% Ni, 0.01% Mo, 0.026% Cr, with Fe as the balance. The 316L stainless steel chemical composition (mass percentage): 0.019% C, 1.18% Mn, 0.43% Si, 10.5% Ni, 16.78% Cr, 2.09% Mo, 0.032% P, 0.0006% S, with Fe as the balance. The dimensions of all the metal materials used are 10mm×10mm×2mm.

[0032] Example 1

[0033] Rinse the collected tobacco stems with tap water and then air dry them in a well-ventilated, cool environment. Grind the dried tobacco stems into powder using a grinder to obtain tobacco stem powder. Then, disperse 4g of tobacco stem powder in 100mL of an aqueous solution containing 50% ethanol (volume fraction) and soak for 2-3 hours. After filtering the solution, concentrate the filtrate using a rotary evaporator until no liquid drips. Finally, dry the resulting concentrate in an oven at 50℃-55℃ for three days to obtain tobacco stem extract. Mix the tobacco stem extract with a 50% ethanol aqueous solution to prepare a tobacco stem extract solution with a mass concentration of 10.0g / L for later use.

[0034] Example 2

[0035] In Example 2, the culture medium used for the desulfurization Vibrio was ATCC1249 medium, which consisted of yeast extract 1.0 g / L, sodium citrate 5.0 g / L, sodium lactate 3.5 g / L, calcium sulfate 1.0 g / L, ammonium chloride 1.0 g / L, magnesium sulfate 2.0 g / L, ferrous ammonium sulfate hexahydrate 1.0 g / L, and potassium phosphate 0.5 g / L.

[0036] (1) Analysis of the antibacterial properties of tobacco stem extract

[0037] Two mL of a 10.0 g / L tobacco stem extract solution was added to 98 mL of *Vibrio desulfurans* bacterial culture as the experimental group, with a tobacco stem extract concentration of 200 mg / L. The same *Vibrio desulfurans* bacterial culture without added tobacco stem extract served as the blank control group. Both groups were anaerobically cultured at a constant temperature of 30℃ for 7 days. After the 7-day culture period, the number of *Vibrio desulfurans* cells was counted using a hemocytometer. Compared to the blank control group, the number of *Vibrio desulfurans* cells in the experimental group decreased by more than 99.99% (calculated using Formula 1), indicating that the tobacco stem extract has an antibacterial effect in inhibiting the growth of *Vibrio desulfurans*.

[0038] Formula 1:

[0039] N: Cell count in culture medium after 7 days without the addition of tobacco stem extract;

[0040] N′: The number of cells in the culture medium after 7 days of culture with added tobacco stem extract.

[0041] (2) Performance analysis of tobacco stem extract in inhibiting biofilm formation of Vibrio desulfurans

[0042] Two mL of a 10.0 g / L tobacco stem extract solution was added to 98 mL of *Vibrio desulfurans* bacterial solution as the experimental group, with a tobacco stem extract concentration of 200 mg / L. A *Vibrio desulfurans* bacterial solution without added tobacco stem extract served as the blank control group. Polished Cu-Cr steel samples (working area 10 mm × 10 mm, polished to 1000#) were irradiated under a UV lamp for 30 min to ensure sterility. The samples were then placed in a culture medium and anaerobically cultured at 30℃ for 7 days. After 7 days, the samples were removed, and the biofilm was fixed with 4% glutaraldehyde for 4 h. The biofilm was then dehydrated using a gradient of ethanol (30%, 50%, 70%, 90%, 100%), followed by gold sputtering to ensure conductivity. The morphology of the biofilm was observed using a scanning electron microscope. After culturing in the culture medium for 7 days, a dense biofilm formed on the surface of the control group sample, while no microbial cells colonized the surface of the experimental group sample, indicating that tobacco stem extract can inhibit the formation of desulfurized Vibrio biofilm on the surface of metal materials.

[0043] (3) Performance analysis of tobacco stem extract in eliminating mature desulfurization Vibrio biofilm

[0044] The polished Cu-Cr steel samples were irradiated under a UV lamp for 30 minutes to ensure sterility. The samples were then placed in a culture medium inoculated with *Vibrio desulfurans* and anaerobically cultured at 30°C for 3 days to ensure biofilm formation on the sample surface. On the fourth day, tobacco stem extract solution was added to the culture medium, and the samples were anaerobically cultured again for 2 days. After removal and drying, the samples were stained with live / dead dyes and observed under a laser confocal microscope to assess cell morphology. Compared to the control group without tobacco stem extract, a large number of cells attached to the sample surface treated with tobacco stem extract died, and the proportion of live cells in the biofilm decreased from 87% in the control group to 5% in the experimental group. Biomass in the biofilm was detected using an ATP assay kit; the biomass in the biofilm on the sample surface of the control group decreased by 92.5% compared to the control group. Cell viability of the biofilm was detected using a CCK-8 assay kit; the cell viability in the experimental group was only 3% (calculated using Equation 2). This indicates that tobacco stem extract can effectively eliminate mature *Vibrio desulfurans* biofilm.

[0045] Formula 2:

[0046] OD S490 : The absorbance of samples containing inoculation culture medium, CCK solution, and tobacco stem extract solution;

[0047] OD C490 : The absorbance of samples with control culture medium and CCK solution;

[0048] OD M490 : The absorbance of samples containing inoculation culture medium and CCK solution.

[0049] (4) Electrochemical analysis of the inhibitory effect of tobacco stem extract on Vibrio desulfurization microbial corrosion

[0050] Cu-Cr steel (10mm×10mm×3mm) was used as the experimental sample, and epoxy resin was used as the working electrode. Under anaerobic conditions, 4 mL of a 10.0 g / L tobacco stem extract solution was added to 196 mL of Vibrio desulfurization bacterial solution as the experimental group, with a tobacco stem extract concentration of 200 mg / L. The same Vibrio desulfurization bacterial solution without tobacco stem extract was used as the blank control group. Both the experimental and blank control groups were cultured for 7 days. Using a three-electrode system, the corrosion electrochemical performance of the Cu-Cr steel samples in the blank control and experimental groups was tested daily using an electrochemical workstation, including open-circuit potential, linear polarization resistance, and electrochemical impedance. The test results showed that the polarization resistance and charge transfer resistance of the samples significantly increased after the addition of tobacco stem extract, indicating that microbial corrosion was inhibited. Potentiodynamic polarization testing was performed on day 7, and the corrosion current density (i) of the samples was obtained by Tafel fitting. corr Compared with the blank control group, the i of the samples in the experimental groupcorr From 24.2 μA / cm 2 Decreased to 0.5 μA / cm 2 Its corrosion inhibition rate is 97.9% (calculated using Formula 3).

[0051] Formula 3:

[0052] ′ corr Corrosion current density of samples cultured for 7 days without the addition of tobacco stem extract;

[0053] i corr Corrosion current density of samples after culturing with tobacco stem extract for 7 days.

[0054] (5) Pitting corrosion weight loss analysis of the inhibitory effect of tobacco stem extract on Vibrio desulfurization microbial corrosion.

[0055] Under anaerobic conditions, 4 mL of a 10.0 g / L tobacco stem extract solution was added to 196 mL of Vibrio desulfurization bacterial solution as the experimental group, with a tobacco stem extract concentration of 200 mg / L. The same Vibrio desulfurization bacterial solution without added tobacco stem extract served as the blank control group. Cu-Cr steel test samples were added to both the experimental and blank control groups and cultured anaerobically for 7 days. After removing corrosion products and biofilm, the mass of the samples before and after immersion was measured using a balance. The mass losses W and W′ of the test samples in the experimental and control groups were obtained, respectively. Compared with the blank control group, the weight loss of the test samples in the experimental group was 5.6 mg / cm³. 2 Decreased to 0.3 mg / cm 2 The corrosion inhibition rate was 94.6% (calculated using Equation 4). The maximum pitting depth on the sample surface decreased from 13.9 μm to 2.6 μm.

[0056] Formula 4:

[0057] W: Mass loss of the sample after 7 days of culture without the addition of tobacco stem extract;

[0058] W′: Mass loss of the sample after culturing for 7 days with added tobacco stem extract.

[0059] Example 3

[0060] In Example 3, the culture medium used for Bacillus licheniformis was LB medium, which consisted of 10.0 g / L sodium chloride, 10.0 g / L tryptone, and 5.0 g / L yeast extract.

[0061] (1) Analysis of the antibacterial properties of tobacco stem extract

[0062] A 2 mL solution of 10.0 g / L tobacco stem extract was added to 98 mL of Bacillus licheniformis bacterial suspension as the experimental group, with a tobacco stem extract concentration of 200 mg / L. The same Bacillus licheniformis bacterial suspension without tobacco stem extract was used as the blank control group. Both groups were aerobically cultured at 30℃ for 7 days. After the 7-day culture period, the number of Bacillus licheniformis cells was calculated using the plate spreading method. Compared with the blank control group, the number of Bacillus licheniformis cells in the experimental group decreased by more than 99.99% (calculated using Formula 1), indicating that the tobacco stem extract has an antibacterial effect in inhibiting the growth of Bacillus licheniformis.

[0063] (2) Performance analysis of tobacco stem extract in inhibiting Bacillus licheniformis biofilm formation

[0064] A 2 mL solution of 10.0 g / L tobacco stem extract was added to 98 mL of Bacillus licheniformis bacterial suspension as the experimental group, with a tobacco stem extract concentration of 200 mg / L. The same Bacillus licheniformis bacterial suspension without tobacco stem extract was used as the blank control group. Polished Cu-Cr steel samples (working area 10 mm × 10 mm, polished to 1000#) were irradiated under UV light for 30 min to ensure sterility. The samples were then placed in a culture medium and aerobically cultured at 30℃ for 7 days. After 7 days, the samples were removed, and the biofilm was fixed with 4% glutaraldehyde for 4 h. The biofilm was then dehydrated using a gradient of ethanol (30%, 50%, 70%, 90%, 100%), followed by gold sputtering to ensure conductivity. The morphology of the biofilm was observed using a scanning electron microscope. After culturing in the culture medium for 7 days, a dense biofilm formed on the surface of the control group sample, while no microbial cells colonized the surface of the experimental group sample, indicating that tobacco stem extract can inhibit the formation of Bacillus licheniformis biofilm on the surface of metal materials.

[0065] (3) Performance analysis of tobacco stem extract in eliminating biofilm of mature Bacillus licheniformis

[0066] The polished Cu-Cr steel samples were irradiated under a UV lamp for 30 minutes to ensure sterility. The samples were then placed in a culture medium inoculated with *Bacillus licheniformis* and subjected to aerobic pre-culture at 30°C for 3 days to ensure biofilm formation on the sample surface. On the fourth day, tobacco stem extract solution was added to the culture medium, and the samples were cultured again for 2 days. After removal and drying, the samples were stained with live / dead dyes and observed under a laser confocal microscope to assess cell state. Compared to the control group without tobacco stem extract, a large number of cells attached to the sample surface died after treatment with tobacco stem extract, and the proportion of live cells in the biofilm decreased from 84% in the control group to 2% in the experimental group. The biomass of the biofilm was detected using an ATP assay kit; the biomass on the sample surface in the control group decreased by 92.3% compared to the control group. Cell viability of the biofilm was detected using CCK-8 time and assay; the cell viability in the experimental group was only 5% (calculated using formula 2). This indicates that tobacco stem extract can effectively eliminate mature *Bacillus licheniformis* biofilm.

[0067] (4) Electrochemical analysis of the inhibitory effect of tobacco stem extract on Bacillus licheniformis microbial corrosion

[0068] Cu-Cr steel (10mm×10mm×3mm) was used as the experimental sample, and epoxy resin was used as the working electrode. Under aerobic conditions, 4 mL of a 10.0 g / L tobacco stem extract solution was added to 196 mL of Bacillus licheniformis bacterial solution as the experimental group, with a tobacco stem extract concentration of 200 mg / L. The same Bacillus licheniformis bacterial solution without tobacco stem extract was used as the blank control group. Both the experimental and blank control groups were cultured for 7 days. Using a three-electrode system, the corrosion electrochemical performance of the Cu-Cr steel samples in the blank control and experimental groups was tested daily using an electrochemical workstation, including open-circuit potential, linear polarization resistance, and electrochemical impedance. The test results showed that the polarization resistance and charge transfer resistance of the samples significantly increased after the addition of tobacco stem extract, indicating that microbial corrosion was inhibited. Potentiodynamic polarization tests were performed after 7 days, and the corrosion current density (i) of the samples was obtained by Tafel fitting. corr Compared with the blank control group, the i of the samples in the experimental group corr From 15.9 μA / cm 2 Decreased to 0.5 μA / cm 2 Its corrosion inhibition rate is 96.9% (calculated using Formula 3).

[0069] (5) Pitting corrosion weight loss analysis of the inhibitory effect of tobacco stem extract on Bacillus licheniformis microbial corrosion.

[0070] Under aerobic conditions, 2 mL of a 10.0 g / L tobacco stem extract solution was added to 98 mL of Bacillus licheniformis bacterial suspension as the experimental group, with a tobacco stem extract concentration of 200 mg / L. The same Bacillus licheniformis bacterial suspension without added tobacco stem extract served as the blank control group. Cu-Cr steel test samples were added to both the experimental and blank control groups and cultured for 7 days. After removing corrosion products and biofilm, the mass of the samples before and after immersion was measured using a balance. The mass losses W and W′ of the test samples in the experimental and control groups were obtained, respectively. Compared with the blank control group, the weight loss of the test samples in the experimental group was 4.3 mg / cm³. 2 Decreased to 0.5 mg / cm 2 The corrosion inhibition rate was 88.4% (calculated using Formula 4). The maximum pitting depth on the sample surface decreased from 10.4 μm to 2.1 μm.

[0071] Example 4

[0072] The experimental solution in Example 4 consisted of sodium chloride at a concentration of 10.0 g / L.

[0073] (1) Electrochemical analysis of the corrosion inhibition properties of tobacco stem extract

[0074] Cu-Cr steel, X80 steel, and 316L stainless steel (10mm×10mm×3mm) were used as experimental samples, sealed with epoxy resin as the working electrode. Under anaerobic conditions, 4 mL of a 10.0 g / L tobacco stem extract solution was added to 196 mL of experimental solution as the experimental group, with a tobacco stem extract concentration of 200 mg / L. An experimental solution without tobacco stem extract was used as the blank control group. Both experimental and blank control groups were cultured for 7 days. Using a three-electrode system, the corrosion electrochemical performance of the Cu-Cr steel, X80 steel, and 316L stainless steel samples in the blank control and experimental groups was tested daily using an electrochemical workstation, including open-circuit potential, linear polarization resistance, and electrochemical impedance. The test results showed that the polarization resistance and charge transfer resistance of the samples significantly increased after the addition of tobacco stem extract, indicating that corrosion was inhibited. Potentiodynamic polarization tests were performed after 7 days, and the corrosion current density (ii) of the Cu-Cr steel, X80 steel, and 316L stainless steel samples was obtained by Tafel fitting. corr Compared with the blank control group, the i values ​​of Cu-Cr steel, X80 steel, and 316L stainless steel samples in the experimental group were significantly higher. corr From 2.2 μA / cm 2 0.4μA / cm 2 0.08μA / cm 2 Decreased to 233 nA / cm 2 58nA / cm 2 12nA / cm 2Their corrosion inhibition rates all reach over 85% (calculated using formula 3).

[0075] (2) Analysis of pitting corrosion and weight loss of the corrosion inhibition properties of tobacco stem extract

[0076] Two mL of a 10.0 g / L tobacco stem extract solution was added to 98 mL of experimental solution as the experimental group, with a tobacco stem extract concentration of 200 mg / L. An experimental solution without added tobacco stem extract served as the blank control group. Cu-Cr steel, X80 steel, and 316L stainless steel samples were added to both the experimental and blank control groups and incubated for 7 days. After removing corrosion products and biofilm, the mass of Cu-Cr steel and X80 steel before and after immersion was measured using a balance, and the weight loss was calculated. Compared to the blank control group, the weight loss of Cu-Cr steel and X80 steel samples in the experimental group decreased from 1.6 mg / cm³ to 1.6 mg / cm³. 2 and 2.8 mg / cm 2 Decreased to 0.2 mg / cm 2 and 0.5 mg / cm 2 The corrosion inhibition rates were 87.5% and 82.1%, respectively (calculated using Formula 4). The maximum pitting depths on the surfaces of Cu-Cr steel, X80 steel, and 316L stainless steel samples decreased from 6.7 μm, 5.8 μm, and 3.0 μm to 2.8 μm, 2.4 μm, and 1.6 μm, respectively.

[0077] In summary, the antibacterial and corrosion characterization experiments in this invention demonstrated that when the concentration of tobacco stem extract reaches 200 mg / L, it can achieve broad-spectrum antibacterial effects against both Gram-negative and Gram-positive bacteria. It can effectively inhibit the initial adhesion of microorganisms to metal surfaces and eliminate existing mature biofilms, and also has a significant inhibitory effect on microbial corrosion. The tobacco stem extract is an inexpensive and readily available raw material, the preparation method is simple and environmentally friendly, and the antibacterial and corrosion-inhibiting effects are significant, enabling efficient control of microbial corrosion of metallic materials in the environment.

Claims

1. The application of a tobacco stem extract as a microbial corrosion inhibitor, characterized in that, The preparation method of the tobacco stem extract includes the following steps: Step 1: Wash the collected tobacco stems and then let them dry; Step 2: Grind the dried tobacco stems into powder to obtain tobacco stem powder; Step 3: Disperse the tobacco stem powder in an ethanol-water solution and soak for 2-3 hours; Step 4: Filter the solution and then concentrate the filtrate; Step 5: Dry the obtained concentrate to obtain tobacco stem extract; An ethanol-water solution of tobacco stem extract was used as a microbial corrosion inhibitor, specifically referring to sulfate-reducing bacteria *Desulfovibrio* and *Bacillus licheniformis*. When the concentration of tobacco stem extract reached 200 mg / L, the antibacterial efficiency against sulfate-reducing bacteria *Desulfovibrio* and *Bacillus licheniformis* reached over 99.99%, the inhibition rate against microbial corrosion of metal materials reached over 85%, and the proportion of live cells in the biofilm on the surface of metal materials was reduced to below 5%.

2. The application according to claim 1, characterized in that, In step 3, the volume fraction of ethanol in the aqueous ethanol solution is 40%-50%.

3. The application according to claim 1, characterized in that, In step 5, the concentrate is dried in an oven at 45℃-55℃ for 2-3 days to obtain tobacco stem extract.

4. The application according to claim 1, characterized in that, Application methods include: Step 1: Mix the tobacco stem extract with an ethanol aqueous solution with a volume fraction of 40%-60% to form an ethanol aqueous solution with a tobacco stem extract mass concentration of 0.2g / L-10g / L, which serves as a microbial corrosion inhibitor; Step 2: Apply microbial corrosion inhibitors to the microbial corrosion environment to achieve the purpose of inhibiting microbial corrosion.

5. The application according to claim 4, characterized in that, The microbial corrosion environment includes soil environment, atmospheric environment and marine environment.

6. The application according to claim 4, characterized in that, The steps of step 2 include: adding tobacco stem extract to anaerobic sulfate-reducing Vibrio desulfurization culture containing metal materials and aerobic Bacillus licheniformis culture for co-culture to complete the microbial corrosion inhibition experiment; the metal materials are selected from carbon steel and stainless steel.