Composite plant essential oil and emulsion for antagonizing bacterial biofilm as well as preparation method and application of composite plant essential oil and emulsion

Abstract

The invention belongs to the technical field of biology, and particularly discloses a composite plant essential oil for antagonizing a bacterial biofilm, which is composed of cinnamon essential oil and star anise essential oil. The compound plant essential oil disclosed by the invention consists of the cinnamon essential oil and the star anise essential oil which have a synergistic effect, have good bacteriostatic activity on salmonella, escherichia coli and the like, can inhibit the formation of a bacterial biofilm, and have a strong removal effect on the formed bacterial biofilm; and when being used for removing bacterial biofilms, the cleaning agent has the characteristics of good removal effect, low toxicity and the like.

Description

Technical Field

[0001] The invention relates to the field of biotechnology, and in particular to a composite plant essential oil and emulsion for antagonizing bacterial biofilms, and a preparation method and application thereof. Background Art

[0002] As an important zoonotic pathogen, Salmonella poses a major threat to global public health. According to estimates by the World Health Organization, there are up to 600 million cases of illness caused by contaminated food each year, of which about 350 million are caused by pathogenic bacteria, one of which is Salmonella. Salmonella has a wide range of hosts, including poultry, cattle, pigs and other livestock and wild animals, pets, fish and rodents. There are also asymptomatic infected animals that spread pathogens through feces. Salmonella in feces continues to contaminate crops, especially vegetables and fruits, through soil and water sources, all of which make it very difficult to monitor and control pathogens.

[0003] The colonization of Salmonella under natural conditions depends on the formation of bacterial biofilm (BF) on its surface. BF is a membrane-like biological community formed by the matrix composed of extracellular polymers secreted by bacteria, in which bacteria can form a highly organized community. The formation of BF provides a protective barrier for Salmonella, enabling it to resist the host's immune response and adverse physical or chemical factors in the environment. Removing biofilm can reverse the resistance of bacteria to antibiotics, reduce the minimum inhibitory concentration of drugs, and effectively remove bacteria that were previously difficult to remove. Existing physical or chemical methods have limitations in their application for the removal of biofilms. Physical methods such as ultrasound, electromagnetic fields, plasma and irradiation can destroy the structure of biofilms, but their application areas are limited, for example, they cannot complete the removal of deep biofilms. Chemical methods involve the use of chemical reagents such as sodium hypochlorite, hydrogen peroxide, ozone and peracetic acid for cleaning and disinfection, which may have a negative impact on the environment, produce waste liquid, waste gas or waste solids, and may contain toxic, harmful or difficult to degrade substances. At the same time, there are safety risks in the chemical treatment process, such as the corrosiveness, irritation or flammability of chemicals may lead to safety accidents. And this physical and chemical means are powerless against bacterial biofilms on food. Summary of the invention

[0004] In view of the above shortcomings, the present invention provides a composite plant essential oil for antagonizing bacterial biofilm, which can effectively inhibit and remove bacterial biofilm, exert a greater antagonistic effect while reducing the amount of essential oil used as much as possible, and has a synergistic effect. The specific technical scheme is as follows:

[0005] The invention discloses a composite plant essential oil for antagonizing bacterial biofilm. The composite plant essential oil consists of cinnamon essential oil and star anise essential oil.

[0006] Preferably, in the above-mentioned composite plant essential oil, the volume ratio of the cinnamon essential oil to the star anise essential oil is 1:40-100.

[0007] Preferably, in the above-mentioned composite plant essential oil, the volume ratio of the cinnamon essential oil to the star anise essential oil is 1:80.

[0008] On the other hand, the present invention also provides a plant essential oil emulsion for antagonizing bacterial biofilm, wherein the plant essential oil emulsion comprises the above-mentioned composite plant essential oil.

[0009] Preferably, in the above-mentioned plant essential oil emulsion, the plant essential oil emulsion comprises the following raw materials, calculated by volume percentage: 0.05-0.8% of composite plant essential oil, 0.5-2% of Tween-80, and the balance of water.

[0010] On the other hand, the present invention also provides a method for preparing the above-mentioned plant essential oil emulsion, comprising the following steps:

[0011] (1) Extraction of cinnamon essential oil: cinnamon powder is added with 6 to 8 times water for steam distillation to obtain an oil-water mixture, sodium chloride is added and allowed to stand for stratification, and the upper layer of liquid is collected to obtain cinnamon essential oil;

[0012] (2) Extraction of star anise essential oil: add 8 to 10 times water to star anise powder and perform steam distillation to obtain an oil-water mixture, add sodium chloride and allow to stand for stratification, collect the upper liquid, and obtain star anise essential oil;

[0013] (3) Cinnamon essential oil and star anise essential oil are mixed in proportion, Tween-80 is added and mixed evenly, and then dispersed in water and ultrasonically dispersed to obtain a plant essential oil emulsion.

[0014] Preferably, in the above-mentioned preparation method, in step (1), the steam distillation extraction is carried out for 1.5 to 3 hours, and the sodium chloride addition ratio is 0.08 to 0.12 g / ml; in step (2), the steam distillation extraction is carried out for 1.5 to 3 hours, and the sodium chloride addition ratio is 0.08 to 0.12 g / ml.

[0015] On the other hand, the present invention also provides the use of the above-mentioned composite plant essential oil in the preparation of medicines or daily chemicals for resisting bacteria or antagonizing bacterial biofilm.

[0016] Preferably, in the above application, the bacteria is Salmonella, Escherichia coli or Staphylococcus aureus.

[0017] On the other hand, the present invention also provides the use of the plant essential oil emulsion in preparing daily chemicals for antagonizing bacterial biofilm or removing bacterial biofilm.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The composite plant essential oil of the present invention is composed of cinnamon essential oil and star anise essential oil, which have a synergistic effect, have good antibacterial activity against Salmonella, Escherichia coli, etc., can inhibit the formation of bacterial biofilms, and have a strong clearing effect on the already formed bacterial biofilms. Even after 4 times dilution, the formation of biofilms can still be reduced by about 80%.

[0020] 2. The present invention can reduce the minimum inhibitory concentration of star anise essential oil to 1 / 4 of the original value through the composite synergistic effect of cinnamon essential oil and star anise essential oil, which can significantly reduce the amount of essential oil used and reduce costs.

[0021] 3. The composite essential oil and the emulsion thereof of the present invention are of pure natural origin, green and environmentally friendly, and have the characteristics of good removal effect and low toxicity for removing bacterial biofilm, and can be applied to use in various fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 This is a screening diagram of the biofilm forming ability of 8 strains of Salmonella in Test Example 1 of the present invention. Figure 1 From left to right in the middle are the bacteria numbered C6272, C6273, C6277, C6304, C6458, C6465, C6469, and C42;

[0024] Figure 2 This is a diagram showing the inhibitory effect of essential oils on biofilm in Experimental Example 3 of the present invention: CEO is cinnamon essential oil, SAEO is star anise essential oil, and SCEO is a composite essential oil;

[0025] Figure 3 This is a diagram showing the removal effect of the composite essential oil on mature biofilm in Experimental Example 3 of the present invention.

[0026] Figure 4 The pixel quantity diagram of bacterial agglomerates adhered under a scanning electron microscope in Experimental Example 3 of the present invention: CEO is a cinnamon essential oil group, SAEO is an anise essential oil group, SCEO is a compound essential oil group, blank is a blank control, and Tween 80 is a Tween 80 control;

[0027] Figure 5The following are SEM images of the morphological observation of Salmonella in each treatment group in Test Example 3 of the present invention: A1: blank control group 1000×; B1: culture medium control containing Tween-80 1000×; C1: CEO group 1000×; D1: SAEO group 1000×; E1: SCEO group 1000×; A2: blank control group 5000×; B2: culture medium control containing Tween-80 5000×; C2: CEO group 5000×; D2: SAEO group 5000×; E2: SCEO group 5000×. DETAILED DESCRIPTION

[0028] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Unless otherwise defined, all professional terms used hereinafter have the same meaning as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the present invention, etc. can be purchased from the market or can be prepared by existing methods.

[0029] Example 1

[0030] The invention discloses a composite plant essential oil for antagonizing bacterial biofilm, which is composed of cinnamon essential oil and star anise essential oil in a volume ratio of 1:80.

[0031] Example 2

[0032] The invention discloses a composite plant essential oil for antagonizing bacterial biofilm, which is composed of cinnamon essential oil and star anise essential oil in a volume ratio of 1:40.

[0033] Example 3

[0034] The invention discloses a plant essential oil emulsion for antagonizing bacterial biofilm. The plant essential oil emulsion is composed of the following raw materials by volume percentage: 0.158% of a composite plant essential oil, 0.8% of Tween-80, and the remainder of water; the composite plant essential oil is obtained by mixing cinnamon essential oil and star anise essential oil in a volume ratio of 1:80.

[0035] The preparation method of the plant essential oil emulsion for antagonizing bacterial biofilm of this embodiment comprises the following steps:

[0036] (1) Extraction of cinnamon essential oil: Cinnamon is crushed by a wall breaking machine and passed through a No. 4 sieve. 100 g of cinnamon powder is added with 700 ml of water and heated for 2 h by steam distillation to obtain an essential oil-water mixture. NaCl powder is added at a ratio of 0.1 g / ml, mixed, and poured into a separatory funnel to stand overnight. After the oil and water are separated, the lower water layer is discarded, and the upper light yellow liquid is retained and placed in an EP tube. An appropriate amount of anhydrous sodium sulfate is added to remove water overnight, and then the upper liquid is transferred to a new EP tube and stored at 4°C in the dark.

[0037] (2) Extraction of star anise essential oil: Star anise is crushed by a wall breaking machine and passed through a No. 2-3 sieve. 100 g of star anise powder is added with 1000 ml of water. The essential oil-water mixture is obtained by steam distillation and heated for 2 h. NaCl powder is added at a ratio of 0.1 g / ml, mixed, and poured into a separating funnel and left to stand overnight. After the oil and water are separated, the lower water layer is discarded, and the upper light yellow liquid is retained and placed in an EP tube. An appropriate amount of anhydrous sodium sulfate is added to remove water overnight, and then the upper liquid is placed in a new EP tube and stored in the dark at 4°C.

[0038] (3) Cinnamon essential oil and star anise essential oil are mixed in proportion, Tween-80 is added and mixed evenly, and then dispersed in water and ultrasonically dispersed to obtain a plant essential oil emulsion.

[0039] Example 4

[0040] A plant essential oil emulsion for antagonizing bacterial biofilms is provided. The plant essential oil emulsion is composed of the following raw materials by volume percentage: 0.31% of a composite plant essential oil, 1% of Tween-80, and the remainder of water; the composite plant essential oil is obtained by mixing cinnamon essential oil and star anise essential oil in a volume ratio of 1:80. The preparation method of the plant essential oil emulsion for antagonizing bacterial biofilms in this embodiment is the same as that in Example 3.

[0041] Example 5

[0042] A plant essential oil emulsion for antagonizing bacterial biofilms is provided. The plant essential oil emulsion is composed of the following raw materials by volume percentage: 0.633% of a composite plant essential oil, 1% of Tween-80, and the remainder of water; the composite plant essential oil is obtained by mixing cinnamon essential oil and star anise essential oil in a volume ratio of 1:80. The preparation method of the plant essential oil emulsion for antagonizing bacterial biofilms in this embodiment is the same as that in Example 3.

[0043] Test Example 1 Identification of BF Formation Ability of Multidrug Resistant (MDR) Salmonella Isolates

[0044] Strain: Salmonella Thompson serotype 8, isolated from randomly collected edible snails, Figure 1Numbered from left to right (C6272, C6273, C6277, C6304, C6458, C6465, C6469, C42). The specific separation method is as follows:

[0045] Randomly collect field snails from different local waters, preserve them at low temperature and transport them back to the laboratory. Take out the snail meat from the shell, cut it into pieces, and culture Salmonella in buffered peptone water medium at a ratio of 1:10, at 37 °C for 24 hours; then inoculate the bacterial liquid into selenite cystine enrichment broth at a ratio of 1:10, at 37 °C for 24 hours; then use an inoculation loop to inoculate the bacterial liquid onto lysine deoxycholate agar plate. After incubating at 37 °C for 24 hours, pick suspected Salmonella colonies from the plate; conduct biochemical identification, inoculate into triple sugar iron and urea agar, and then incubate at 37 °C for 24 hours; finally, use Salmonella antiserum to determine the serotype of all strains by serum agglutination typing for the colonies that meet the Salmonella biochemical identification results.

[0046] The strains were activated by culturing in LB broth medium (Solarbio, Beijing, China) at 37 °C in a constant temperature shaker at 150 rpm for 24 h. To screen for strong biofilm-forming strains, the 96-well microplate crystal violet staining method was used as shown in Figure 1 , and the specific steps are as follows:

[0047] Inoculate the activated bacterial liquid into a 96-well microplate with a final concentration of 1×10 6 CFU / mL, and then continue to culture for 48 h until the biofilm matures; pour out most of the bacterial liquid and wash twice with PBS. Add pure methanol to fix for 15 min, discard the methanol and let it dry. Then add crystal violet to stain for 5 min, discard the crystal violet, wash with water until the effluent is colorless, and finally add absolute ethanol for decolorization. Measure the absorbance at 570 nm with an enzyme-linked immunosorbent assay (ELISA) reader.

[0048] The average OD value of the negative control group is denoted as ODc. The classification of biofilm formation ability is as follows: strong biofilm formation (4ODc < OD), moderate biofilm formation (2ODc < OD ≤ ODc), weak biofilm formation (ODc < OD ≤ 2ODc), no biofilm formation (OD ≤ ODc). The Salmonella strain with the highest OD value in the strong biofilm-producing group was reserved for the subsequent experiments of this study. The experimental results are shown in Table 1, and the results show that foodborne Salmonella Thompson (C6304) is a strong biofilm type.

[0049] Table 1 Crystal violet staining method for screening strong biofilm-forming Salmonella

[0050]

[0051] Experimental Example 2

[0052] 2.1 Minimum inhibitory concentration test of cinnamon essential oil and star anise essential oil

[0053] Used bacteria: Foodborne Salmonella Thompson (strong biofilm type C6304), Escherichia coli ( 25922), Staphylococcus aureus ( 25923) were used in this experiment, Escherichia coli (ATCC25922), Staphylococcus aureus ( 25923) was purchased from Guangdong Microbiological Culture Collection Center, and levofloxacin was used as a quality control drug.

[0054] The chessboard method was used to test the minimum inhibitory concentration of cinnamon essential oil and star anise essential oil. The specific test method includes the following steps:

[0055] (1) Preparation of drug solution: Add Tween-80 to MH broth culture medium at a ratio of 1% as diluent; use a pipette to draw 100 μL of essential oil into 10 mL of diluent to make a 10 μL / mL mother solution and mix thoroughly. Add 500 μL of diluent to the EP tube, and use the gradient dilution method to dilute the cinnamon essential oil mother solution to 10 μL / mL, 5 μL / mL, 2.5 μL / mL, 1.25 μL / mL, 0.625 μL / mL, 0.31 μL / mL, 0.16 μL / mL, and 0.08 μL / mL, with the diluent as the blank; the dilution method of star anise essential oil is the same as above, and the final concentration is 100 μL / mL, 50 μL / mL, 25 μL / mL, 12.5 μL / mL, 6.25 μL / mL, 3.12 μL / mL, 1.56 μL / mL, and 0.78 μL / mL;

[0056] (2) Inoculate 50 μL of the test bacterial solution (1×10 6 CFU / mL), shaker 150 rpm, 37 °C for 20 h;

[0057] (3) Pipette 180 μL from each EP tube into a 96-well plate and add 20 μL of diluted 0.1% red tetrazolium saline solution to each well. After 4 h of incubation, use an ELISA reader to measure the absorbance at 485 nm or the minimum drug concentration at which the bacterial solution does not turn red as the MIC value.

[0058] The results are shown in Table 2. Cinnamon essential oil and star anise essential oil have good bactericidal activity against strong biofilm bacteria Salmonella, and also have good bactericidal effects on Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli), and Salmonella enteritidis.

[0059] Table 2 Antibacterial activity of cinnamon essential oil and star anise essential oil against four common bacteria

[0060]

[0061] 2.2 Determination of synergistic antibacterial index of star anise and cinnamon essential oils

[0062] Experimental strain: Foodborne Salmonella Thompson (strong biofilm type C6304)

[0063] The test method is as follows:

[0064] (1) Preparation of broth dilution: Add Tween-80 at a ratio of 1% to sterile MH broth, and then vortex ultrasonically to obtain a uniform solution.

[0065] (2) Preparation of essential oil emulsion: The two essential oils were added to MH broth at a ratio of 4 times the MIC, and then ultrasonically vortexed to obtain a milky white emulsion.

[0066] (3) Addition method: Mix the two essential oil emulsions in order according to the chessboard method (see Table 3), and add 300uL to each EP tube;

[0067] (4) Culture method: Salmonella cultured overnight was diluted to 1×10 7 CFU / mL, add 50uL to each EP tube, so that the final concentration is 1×10 6 CFU / mL. Incubate at 37°C for 20 h at 150 rpm in a constant temperature shaker.

[0068] (5) Detection method: Pipette 180ul from each EP tube into a 96-well plate, and add 20uL of diluted 0.1% red tetrazolium saline solution to each well. After incubation for 4h, use an ELISA reader to detect the absorbance at 485nm or the minimum drug concentration at which the bacterial solution does not turn red as the MIC value, and calculate the fractional inhibitory concentration index (FIC).

[0069] The test results in Table 3 show that the ratios of 1 / 16:1 / 4 group, 1 / 4:1 / 8 group, 1 / 8:1 / 8 group, 1 / 16:1 / 8 group, 1 / 4:1 / 16 group, 1 / 8:1 / 16 group, and 1 / 16:1 / 16 group have no antibacterial activity, and the volume ratio of cinnamon essential oil to star anise essential oil of 1:40-1:100 has a synergistic effect; the volume ratio of cinnamon essential oil to star anise essential oil (cinnamon essential oil at 0.078 μL / mL and star anise essential oil at 6.25 μL / mL) is 1:80, which produces the best synergistic effect, and the synergistic coefficient is 0.375.

[0070] Table 3. Mixture of essential oil emulsions with different MIC ratios by chessboard method

[0071]

[0072] Test Example 3

[0073] 3.1 In vitro inhibition test of star anise cinnamon essential oil on Salmonella biofilm

[0074] Experimental strain: Foodborne Salmonella Thompson (strong biofilm type C6304)

[0075] The experimental method includes the following steps:

[0076] (1) Preparation of broth dilution: Add 1% Tween-80 to sterile MH broth and vortex ultrasonically to obtain a uniform solution;

[0077] (2) Preparation of essential oil emulsion: The two essential oils were sequentially prepared with a 1 / 2 MIC concentration as the initial maximum concentration, and the composite essential oil was separately prepared with a 1 / 2 synergistic concentration;

[0078] (3) Addition method: Add 180 μL of drug solution in a gradient manner to a 96-well plate, and add bacterial solution to each well so that the initial bacterial solution volume is 1×10 6 CFU / mL;

[0079] (4) Culture method: Place a sterilized PP screw of 3 mm × 8 mm in each well and culture at 37 °C for 48 h;

[0080] (5) Detection method: Each screw was washed once with sterile saline, then immersed in 0.1% crystal violet for 1 h. The screw was taken out and washed again with sterile saline, placed in a new 96-well plate, and eluted with anhydrous ethanol for 30 min. The screw was discarded and the absorbance at 570 nm was detected with an ELISA reader, and the blank well value was subtracted.

[0081] Results Figure 2 , the MIC concentrations of essential oils in the figure refer to their respective corresponding MIC concentrations, the MIC concentration of cinnamon essential oil (CEO) is 0.62μL / mL, the MIC concentration of star anise essential oil (SAEO) is 25μL / mL, and the total MIC concentration of the composite essential oil (SCEO) of 6.25μL / mL star anise essential oil and 0.078μL / mL cinnamon essential oil is 6.328μL / mL. 1 / 4MIC and 1 / 2MIC refer to concentrations that are one quarter and one half of their respective MIC concentrations.

[0082] The results show that the ability of cinnamon essential oil (CEO) alone to inhibit biofilm is weak, only 30%, and is greatly affected by concentration. After being combined with star anise essential oil, the composite essential oil has an inhibitory effect of nearly 80% on biofilm formation at 1 / 4MIC. The two essential oils have a synergistic effect on inhibiting biofilm.

[0083] 3.2 In vitro inhibition test of star anise and cinnamon essential oil on mature Salmonella biofilm

[0084] Experimental strain: Foodborne Salmonella Thompson (strong biofilm type)

[0085] The test method includes the following steps:

[0086] (1) 1×10 7 CFU / mL Salmonella suspension was placed in a 96-well cell plate and cultured for 72 hours; the suspended bacteria were aspirated and washed twice with sterile PBS;

[0087] (2) Cinnamon and star anise compound essential oil was prepared with the concentrations of 4MIC, 2MIC, 1MIC, 1 / 2MIC and 1 / 4MIC according to the essential oil emulsion preparation method, added to a 96-well plate, cultured at a speed of 30 r / min for 24 h, the bacterial solution in the well plate was dried, and then washed twice with PBS;

[0088] (3) Wash once with methanol, fix with methanol again for 30 min, remove methanol and wash once with PBS, stain with 0.1% freshly prepared crystal violet for 15 min, rinse with running water until colorless, evaporate as much water as possible and add anhydrous ethanol, which can be decolorized completely with the aid of ultrasound, and detect the absorbance at 570 nm with an enzyme marker.

[0089] The experimental results are shown in Figure 3 As shown in the figure, after cultivation, when the Salmonella biofilm matures, the compound essential oil at a concentration of 1 / 4MIC can still remove the vast majority (>80%) of the bacterial biofilm.

[0090] 3.3 Effect of star anise and cinnamon essential oil on the morphology of adherent MDR Salmonella in vitro

[0091] Experimental strain: Foodborne Salmonella Thompson (strong biofilm type)

[0092] The test method includes the following steps:

[0093] (1) Preparation of broth dilution: Add Tween-80 at a ratio of 1% to sterile MH broth, and then vortex ultrasonically to obtain a uniform solution.

[0094] (2) Preparation of essential oil emulsions: The two essential oils were sequentially prepared to a 1 / 2 MIC concentration as the initial maximum concentration, and the composite essential oil was separately prepared at a sub-synergistic concentration (1 / 2 composite MIC concentration);

[0095] (3) Add 2 mL of drug solution in a gradient manner to a 6-well cell culture plate, and add bacterial solution to each well so that the initial bacterial solution volume is 1×10 6CFU / mL; set up blank control group, culture medium control group containing Tween-80, cinnamon essential oil group (CEO), star anise essential oil group (SAEO) and compound essential oil group (SCEO);

[0096] (4) After 24 h of culture, the cell slides were removed and washed with 40%, 60%, 80%, 90%, 95%, and 100% ethanol in sequence. The ethanol was replaced by adding ethyl acetate, and the slides were air-dried, sprayed with gold, and observed under a scanning electron microscope. Figure 5 .

[0097] ImageJ software was used to count the bacterial clumps in 6 fields of view. Figure 4 .

[0098] The results showed that cinnamon essential oil (CEO) alone had a poor effect in controlling biofilm formation, close to that of the blank group. When combined with star anise essential oil (SAEO) to make a composite essential oil (SCEO), while exerting an antibacterial effect, it significantly reduced the aggregation of Salmonella, reduced the formation of biofilm agglomerates, and significantly reduced the dosage of star anise essential oil.

[0099] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A composite plant essential oil for antagonizing bacterial biofilm, characterized in that: The composite plant essential oil consists of cinnamon essential oil and star anise essential oil.

2. The composite plant essential oil according to claim 1, characterized in that The volume ratio of the cinnamon essential oil to the star anise essential oil is 1:40-100.

3. The composite plant essential oil according to claim 2, characterized in that The volume ratio of the cinnamon essential oil to the star anise essential oil is 1:

80.

4. A plant essential oil emulsion for antagonizing bacterial biofilm, characterized in that: The plant essential oil emulsion comprises the composite plant essential oil according to any one of claims 1 to 3.

5. The plant essential oil emulsion according to claim 4, characterized in that: Calculated by volume percentage, the plant essential oil emulsion is composed of the following raw materials: 0.05-0.8% of composite plant essential oil, 0.5-2% of Tween-80, and the balance of water.

6. A method for preparing the plant essential oil emulsion according to any one of claims 4 to 5, characterized in that: The following steps are involved: (1) Extraction of cinnamon essential oil: cinnamon powder is added with 6 to 8 times water for steam distillation to obtain an oil-water mixture, sodium chloride is added and allowed to stand for stratification, and the upper layer of liquid is collected to obtain cinnamon essential oil; (2) Extraction of star anise essential oil: add 8 to 10 times water to star anise powder and perform steam distillation to obtain an oil-water mixture, add sodium chloride and allow to stand for stratification, collect the upper layer of liquid, and obtain star anise essential oil; (3) Cinnamon essential oil and star anise essential oil are mixed in proportion, Tween-80 is added and mixed evenly, and then dispersed in water and ultrasonically dispersed to obtain a plant essential oil emulsion.

7. The preparation method according to claim 6, characterized in that: In the step (1), the steam distillation is performed for 1.5 to 3 hours, and the sodium chloride is added in an amount of 0.08 to 0.12 g / ml; in the step (2), the steam distillation is performed for 1.5 to 3 hours, and the sodium chloride is added in an amount of 0.08 to 0.12 g / ml.

8. Use of the composite plant essential oil as claimed in claims 1 to 3 in the preparation of medicines or daily chemicals for resisting bacteria or antagonizing bacterial biofilm.

9. The use according to claim 8, characterized in that: The bacteria are Salmonella, Escherichia coli or Staphylococcus aureus.

10. Application of the plant essential oil emulsion as claimed in claim 4 or 5 in preparing daily chemicals for antagonizing bacterial biofilm or removing bacterial biofilm.

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