Space probiotic microbial agent with bacteriostatic, preservative and fresh-keeping functions and application of space probiotic microbial agent

Abstract

The invention provides a space probiotic microbial agent with bacteriostatic, preservative and fresh-keeping functions and application thereof, and the space probiotic microbial agent comprises space probiotics, fermentation products thereof and plant extracts, the space probiotics are selected from one or more of space lactobacillus plantarum SS18-119, space lactobacillus reuteri Fullarton-9-35 and space lactobacillus plantarum SS18-5 which are carried by Tiangong-2 and Shenzhou 11 spacecrafts, are subjected to space mutagenesis for 63 days and then return to the ground, and the space probiotics are selected from one or more of space lactobacillus plantarum SS18-119, space lactobacillus reuteri Fullarton-9-35 and space lactobacillus plantarum SS18-5. The microbial agent can effectively inhibit the growth of harmful microorganisms such as escherichia coli, bacillus and mould and reduce the inhibitory concentration, can be widely applied to corrosion prevention and fresh keeping of baked food, fruits and vegetables, meat, low-temperature prepared food, instant food, prefabricated vegetables and fermented food, has the advantages of natural sources, high safety and the like, and has wide application prospects. And the bacterial agent can become the most potential bacterial agent in the field of biological preservation and fresh-keeping.

Description

Technical Field

[0001] This invention belongs to the field of food biological preservation and freshness protection, and in particular relates to a space probiotic agent with antibacterial, preservative and freshness protection functions and its application. Background Technology

[0002] Food is highly susceptible to microbial contamination during storage and transportation, with harmful microorganisms such as Escherichia coli, Bacillus, and molds being the main spoilage factors. These microorganisms not only cause rapid deterioration of food flavor, color, and texture but can also trigger foodborne illnesses such as diarrhea and gastrointestinal infections, posing a threat to public health. Especially under fluctuating conditions such as room temperature or cold chain, Bacillus, due to its ability to form heat-resistant spores, has become one of the most difficult contaminants to control in the food industry. Existing food preservation systems mainly rely on chemical preservatives and antibiotic-based antimicrobial agents, such as potassium sorbate, sodium benzoate, and ampicillin (with sodium dehydroacetate having limited use). However, these substances present problems such as the emergence of drug-resistant strains, food safety controversies, and low consumer acceptance. There is an urgent need to develop novel antimicrobial and preservation solutions derived from natural sources, possessing broad-spectrum antimicrobial activity and high safety.

[0003] In recent years, plant extracts and probiotic metabolites, characterized by high safety and natural origin, have been considered important alternatives to chemical preservatives. Polyphenolic plant extracts such as chlorogenic acid, ellagic acid, and EGCG (epigallocatechin gallate) have known antioxidant and antibacterial activities, but they suffer from low solubility in food systems and their antibacterial efficiency is significantly affected by the antibacterial environment, making them difficult to use alone as highly effective preservatives.

[0004] On the other hand, lactic acid bacteria, as recognized as GRAS strains, can produce lactic acid, organic acids, bacteriocins and other metabolically active substances during fermentation. These metabolites not only have antibacterial effects, but can also cause stress to the target bacteria by lowering pH and disrupting cell membrane structure.

[0005] Space microorganisms, due to the mutagenic effects of microgravity, high vacuum, extreme temperature differences, weak magnetic fields, and radiation from high-energy particles (electrons, protons, and heavy ions), can undergo gene mutations with a significantly increased mutation frequency. This leads to changes in their biological traits (such as individual morphology, colony characteristics, physiological and biochemical properties, and immunogenicity) and fermentation production performance (such as biomass, product yield, enzyme activity, potency, and fermentation rate). Using space-mutated strains returned to Earth aboard the Tiangong-2 and Shenzhou-11 spacecraft, and comparing them with the original ground-based strains as controls, strains exhibiting positive mutations were selected.

[0006] Chinese invention patent CN108165512B discloses a *Lactobacillus plantarum* SS18-119 strain that produces extracellular polysaccharides and its application in enhancing the antioxidant activity of organisms. The *Lactobacillus plantarum* SS18-119 strain has the accession number CGMCC No. 15150 at the China General Microbiological Culture Collection Center. This patent optimizes the fermentation conditions for high extracellular polysaccharide production by *Lactobacillus plantarum* SS18-119. The extracellular polysaccharides extracted from the fermentation broth exhibit DPPH scavenging ability, superoxide anion radical (O2-·) scavenging ability, Fe2+ chelating ability, and total reducing capacity or total antioxidant capacity for providing hydrogen atoms to block peroxide formation. Furthermore, this strain also possesses gastrointestinal adverse environment tolerance characteristics, providing practical evidence for the application of extracellular polysaccharides in enhancing the antioxidant activity of organisms.

[0007] Chinese invention patent CN107828703B discloses a type of *Lactobacillus reuteri* Fullarton-9-35 and its applications, with accession number CGMCC No. 14939. Compared with the ground control strain, this patented strain exhibits shorter curdling time, higher viscosity of fermented skim milk, higher bile salt tolerance, higher hydrophobicity, more extracellular polysaccharides, stronger antibacterial activity against various bacteria, and higher reuterin production capacity. Furthermore, safety evaluation experiments indicate that it is safe and possesses potential and value for further development.

[0008] Chinese invention patent CN108004171B discloses a space-borne Lactobacillus plantarum SS18-5 strain that reduces α-glucosidase activity. Its accession number is CGMCC NO.14917. This patent uses the terrestrial native Lactobacillus plantarum GS18 as a control and screens out space-borne Lactobacillus plantarum Fullarton-SS18-5 strain, which has a high inhibition rate of α-glucosidase activity (i.e., high α-glucosidase inhibitor production). It has a strong ability to withstand adverse gastrointestinal environments and can pass through the gastrointestinal tract smoothly to exert health benefits. It can become the most promising strain for the prevention and treatment of diabetes.

[0009] However, single lactic acid bacteria are insufficient to achieve rapid, broad-spectrum, and stable food preservation effects. Furthermore, existing research largely focuses on the individual antibacterial effects of lactic acid bacteria or plant extracts, with limited research on the synergistic antibacterial mechanisms of lactic acid bacteria and polyphenolic plant active substances. In particular, there is a lack of technical systems that combine lactic acid bacteria with different types of polyphenols to achieve synergistic antibacterial effects for food preservation. Therefore, developing natural probiotic agents with high-efficiency antibacterial activity and safety has significant application prospects and industrial value. Summary of the Invention

[0010] In view of this, the present invention aims to propose a space probiotic agent with antibacterial, antiseptic and preservation functions and its application, so as to improve the antibacterial and antiseptic effects and improve food safety through the synergistic effect of space probiotics and plant extracts.

[0011] To achieve the above objectives, the technical solution of the present invention is implemented as follows: In a first aspect, the present invention provides a space probiotic agent with antibacterial, antiseptic, and preservation functions. The space probiotic agent comprises space probiotics and their fermentation products and plant extracts. The space probiotics are selected from one or more of Lactiplantibacillus plantarum SS18-119 (accession number: CGMCC No. 15150), Limosilactobacillus reuteri Fullarton-9-35 (accession number: CGMCC No. 14939), and Lactiplantibacillus plantarum SS18-5 (accession number: CGMCC No. 14917). The plant extracts are selected from one or more of chlorogenic acid, ellagic acid, and epigallocatechin gallate (EGCG).

[0012] Furthermore, the concentration of space probiotics in the space probiotic agent is ≥1×10⁻⁶. 8 CFU / mL, for example, can be 1.25 × 10⁻⁶. 8 CFU / mL, 1.5×10 8 CFU / mL, 2.0×10 8 CFU / mL.

[0013] Furthermore, the concentration of plant extracts in the space probiotic agent is 0.0625~2 mg / mL, for example, 0.0625 mg / mL, 0.1 mg / mL, 0.125 mg / mL, 0.15 mg / mL, 0.2 mg / mL, 0.25 mg / mL, 0.3 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL, 1.0 mg / mL, 1.5 mg / mL, and 2 mg / mL.

[0014] Furthermore, the space probiotics and their fermentation products are obtained by inoculating the space probiotics into a culture medium and fermenting them in shake flasks at 37°C.

[0015] Furthermore, the space probiotic agent is composed of *Lactobacillus plantarum* SS18-119 and its fermentation products, and ellagic acid, wherein the concentration of *Lactobacillus plantarum* SS18-119 is ≥1×10⁻⁶. 8 The concentration of ellagic acid is 0.1~2 mg / mL, for example, 0.1 mg / mL, 0.125 mg / mL, 0.15 mg / mL, 0.2 mg / mL, 0.25 mg / mL, 0.3 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL, 1.0 mg / mL, 1.5 mg / mL, or 2 mg / mL.

[0016] Furthermore, the extraction method of the plant extract is not limited, and any method used in the art to extract chlorogenic acid, ellagic acid, and epigallocatechin gallate is applicable to this invention.

[0017] Furthermore, the harmful microorganisms targeted by the antibacterial agents include, but are not limited to, Escherichia coli, Bacillus, molds, and other microorganisms that can cause food spoilage.

[0018] In a second aspect, the present invention provides a method for preparing the space probiotic agent as described in the first aspect, the method comprising the following steps: S1. Inoculate space probiotics into a culture medium and culture at 37-42℃ to obtain fermentation liquid; S2. Mix the fermented bacterial liquid with plant extracts to obtain the space probiotic agent.

[0019] Furthermore, in step S1, the incubation time is 24~48h.

[0020] Furthermore, in step S1, the culture medium is liquid MRS culture medium.

[0021] Thirdly, the present invention provides a food preservative, the food preservative comprising the space probiotic agent as described in the first aspect.

[0022] Furthermore, the food preservative can be a coating preservative, a spray antibacterial agent, a food cleaning liquid, or a liquid / solid food preservative additive.

[0023] Fourthly, the present invention provides a method for preserving food, which uses the space probiotic agent as described in the first aspect. The preservation method includes the following steps: mixing space probiotics and their fermentation products with plant extracts and spraying the mixture onto the surface of the food.

[0024] Furthermore, the food products include, but are not limited to, baked goods, fruits and vegetables, meats, chilled foods, ready-to-eat foods, pre-prepared dishes, and fermented foods.

[0025] Fifthly, the present invention provides the application of space probiotic agents as described in the first aspect or food preservatives as described in the third aspect in food preservation.

[0026] Furthermore, the application is in the preparation of food preservation products.

[0027] Compared with existing technologies, the space probiotic agent with antibacterial, antiseptic, and preservation functions described in this invention and its application have the following advantages: (1) The space probiotic agent described in this invention is a combination of space probiotics and plant extracts. The synergistic effect of the two effectively reduces the antibacterial concentration, improves the antibacterial and preservative effects, effectively reduces the risk of the target bacteria developing tolerance to a single antibacterial component, and enhances the safety and stability of food preservation.

[0028] (2) The space probiotic agent described in this invention uses space probiotics, which have the effect of antagonizing the growth of harmful microorganisms. The fermentation products of probiotics, such as lactic acid, organic acids, bacteriocins and other metabolites, can destroy the cell membrane permeability of harmful microorganisms, which is conducive to improving the penetration and efficiency of plant extracts to cell membranes. Probiotics and their fermentation products and plant extracts work synergistically on bacterial cell membranes to interfere with bacterial physiological processes, thereby inhibiting bacterial growth and reducing food spoilage.

[0029] (3) The synergistic antibacterial system constructed by the space probiotic agent described in this invention can be widely used for the preservation and freshness of different foods. It has the advantages of natural source, high safety and no change in food flavor, which is in line with the current trend of the food industry to develop natural biological preservation technology. Attached Figure Description

[0030] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram illustrating the effect of a combination of *Lactobacillus plantarum* SS18-119 and ellagic acid on *Escherichia coli* in Example 1 of the present invention. Figure 2 This is a schematic diagram illustrating the effect of a compound bacterial agent of *Lactobacillus reuteri* Fullarton-9-35 and ellagic acid on *Escherichia coli* in Example 2 of the present invention. Figure 3 This is a schematic diagram illustrating the effect of a combination of *Lactobacillus plantarum* SS18-5 and ellagic acid on *Escherichia coli* in Example 3 of the present invention. Figure 4 This is a schematic diagram illustrating the effect of the combination of *Lactobacillus plantarum* SS18-119 and chlorogenic acid on *Escherichia coli* in Example 4 of the present invention. Figure 5 This is a schematic diagram illustrating the effect of Lactobacillus plantarum SS18-119 alone on Escherichia coli, Bacillus, and mold in Comparative Example 1 of the present invention. Figure 6 This is a schematic diagram illustrating the effect of Comparative Example 2 of the present invention using Lactobacillus reuteri Fullarton-9-35 alone on Escherichia coli, Bacillus, and mold. Figure 7 This is a schematic diagram illustrating the effect of Lactobacillus plantarum SS18-5 alone on Escherichia coli, Bacillus, and mold in Comparative Example 3 of the present invention. Figure 8 This is a schematic diagram illustrating the effect of ellagic acid alone on Escherichia coli, Bacillus, and mold in Comparative Example 4 of the present invention. Figure 9 This is a schematic diagram illustrating the effect of chlorogenic acid alone on Escherichia coli, Bacillus, and mold in Comparative Example 5 of the present invention. Figure 10 This is a schematic diagram illustrating the effect of EGCG alone on Escherichia coli, Bacillus, and mold in Comparative Example 6 of the present invention. Figure 11 This is a schematic diagram illustrating the antibacterial effect of the products prepared in the embodiments and comparative examples of the present invention on Escherichia coli; Figure 12 This is a schematic diagram illustrating the antibacterial effect of the products prepared in the embodiments and comparative examples of the present invention against Penicillium.

[0031] Figure 13 This is a schematic diagram illustrating the antibacterial effect of the products prepared in the embodiments and comparative examples of the present invention on Bacillus subtilis. Detailed Implementation

[0032] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0033] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0034] The *Lactobacillus plantarum* SS18-5, *Lactobacillus plantarum* SS18-119, and *Lactobacillus reuteri* Fullerton-9-35 used in the following examples were all derived from commercially available lyophilized bacterial powders. They were purified and preserved after gradient dilution plate separation. The preservation method is as follows: mix well in 40% (v / v) glycerol and store at -80°C for a long time.

[0035] The formula for calculating the FICI (Inhibitory Concentration Index) in the following examples is as follows: FICI=

[0036] Among them, MIC_LAB_comb is the lowest concentration of probiotics that inhibits the growth of harmful microorganisms under combined action, and MIC_Extract_comb is the lowest concentration of plant extracts that inhibits the growth of harmful microorganisms under combined action (MIC_Extract_comb); MIC_LAB_alone is the minimum inhibitory concentration of probiotics acting alone, and MIC_Extract_alone is the minimum inhibitory concentration of plant extracts acting alone.

[0037] Judgment criteria: FICI ≤ 0.5: Synergistic effect; 0.5 < FICI ≤ 1: Partial synergistic effect; 1 < FICI ≤ 4: No relevant effect; FICI > 4: Antagonistic effect.

[0038] Example 1 The method for preparing the space probiotic agent in this example includes the following steps: (1) Preparation of probiotic fermentation broth and its fermentation products: Inoculate the freeze-dried and preserved Lactobacillus plantarum SS18-119 in liquid MRS medium, and statically culture it at 37°C for 24 h, then collect the fermentation broth. Determine the concentration of probiotics in the fermentation broth to be 1×10 9 CFU / mL by measuring the OD600nm value with an enzyme-labeled instrument and the plate counting method; (2) Preparation of harmful microorganisms: Take 100 μL of Escherichia coli or Bacillus subtilis and inoculate them into 2 mL of LB and NA liquid media respectively, shake and culture them at 37°C and 160 r / min for 16 - 18 h, dilute the bacterial liquid with sterile physiological saline, and adjust the bacterial liquid concentration to 1×10 6 CFU / mL.

[0039] (3) Evaluation of antibacterial ability: Add the fermentation broth and ellagic acid prepared in step (1) to a sterile microplate in the order of low concentration to high concentration. The probiotic concentration gradient is set as the original solution, 1 / 2, 1 / 4, 1 / 8, 1 / 16 dilution multiples of the original solution, and the ellagic acid gradient is set as 2, 1, 0.5, 0.25, 0.125, 0.0625 mg / mL. Then add Escherichia coli or Bacillus subtilis in step (2), and culture it at 37°C for 12 h to evaluate the antibacterial effect.

[0040] The antibacterial rate of the combined agent of the space Lactobacillus plantarum SS18-119 and ellagic acid used in this example against Escherichia coli is 97.85%; the antibacterial rate against Penicillium is 88.42%; the antibacterial rate against Bacillus subtilis is 88.17%.

[0041] Example 2 The difference from Example 1 is that step (1) is as follows: Freeze-dried *Lactobacillus reuteri* Fullarton-9-35 is inoculated into liquid MRS medium and cultured statically at 37°C for 24 hours. The fermentation broth is then collected. The concentration of probiotics in the fermentation broth is determined to be 1×10⁻⁶ by measuring the OD600nm value using an enzyme-linked immunosorbent assay (ELISA) reader and by plate counting. 9 CFU / mL.

[0042] The other steps are the same as in Example 1.

[0043] The combined bacterial agent of Lactobacillus reuteri Fullarton-9-35 and ellagic acid used in this embodiment showed an inhibition rate of 96.07% against Escherichia coli, 88.00% against Penicillium, and 87.71% against Bacillus.

[0044] Example 3 The difference from Example 1 is that step (1) is as follows: Freeze-dried *Lactobacillus plantarum* SS18-5 is inoculated into liquid MRS medium, and the fermentation broth is collected. The concentration of probiotics in the fermentation broth is determined by measuring the OD600nm value using an enzyme-linked immunosorbent assay (ELISA) reader and by plate counting (1×10⁻⁶). 9 CFU / mL.

[0045] The other steps are the same as in Example 1.

[0046] The combined bacterial agent of *Lactobacillus plantarum* SS18-5 and ellagic acid used in this embodiment showed an inhibition rate of 92.88% against *Escherichia coli*, 85.63% against *Penicillium*, and 80.86% against *Bacillus*.

[0047] Example 4 The difference from Example 1 is that ellagic acid is replaced with chlorogenic acid in step (3), while the other steps are the same as in Example 1.

[0048] The combined bacterial agent of *Lactobacillus plantarum* SS18-119 and chlorogenic acid used in this embodiment showed an inhibition rate of 95.27% against *Escherichia coli*, 87.58% against *Penicillium*, and 86.55% against *Bacillus*.

[0049] Example 5 The difference from Example 1 is that ellagic acid is replaced with EGCG in step (3), while the other steps are the same as in Example 1.

[0050] The combined bacterial agent of *Lactobacillus plantarum* SS18-119 and EGCG used in this embodiment showed an inhibition rate of 93.21% against *Escherichia coli*, 87.57% against *Penicillium*, and 85.71% against *Bacillus*.

[0051] Comparative Example 1 The difference between this comparative example and Example 1 is that ellagic acid was not added, and only *Lactobacillus plantarum* SS18-119 was used; the other steps were the same as in Example 1. The probiotic preparation in this comparative example showed an inhibition rate of 89.21% against *Escherichia coli*, 87.25% against *Penicillium*, and 86.87% against *Bacillus*.

[0052] Comparative Example 2 The difference between this comparative example and Example 2 is that ellagic acid was not added, and only Lactobacillus reuteri Fullarton-9-35 was used; the other steps were the same as in Example 2. The probiotic preparation in this comparative example showed an inhibition rate of 89.06% against Escherichia coli, 85.52% against Penicillium, and 82.93% against Bacillus.

[0053] Comparative Example 3 The difference between this comparative example and Example 3 is that ellagic acid was not added, and only *Lactobacillus plantarum* SS18-5 was used; the other steps were the same as in Example 3. The probiotic agent in this comparative example showed an inhibition rate of 83.95% against *Escherichia coli*, 81.15% against *Penicillium*, and 80.00% against *Bacillus*.

[0054] Comparative Example 4 The difference between this comparative example and Example 1 is that *Lactobacillus plantarum* SS18-119 was not added; only ellagic acid was used. All other steps were the same as in Example 1. In this comparative example, the minimum inhibitory concentration (MIC) of ellagic acid against *Escherichia coli* was 2 mg / mL, achieving an inhibition rate of 85.48%; against *Penicillium*, the MIC was 2 mg / mL, achieving an inhibition rate of 83.17%; and against *Bacillus*, the MIC was 2 mg / mL, achieving an inhibition rate of 77.08%.

[0055] Comparative Example 5 The difference between this comparative example and Example 4 is that *Lactobacillus plantarum* SS18-119 was not added; only chlorogenic acid was used. The other steps were the same as in Example 1. In this comparative example, the minimum inhibitory concentration (MIC) of chlorogenic acid against *Escherichia coli* was 2 mg / mL, achieving an inhibition rate of 82.90%; against *Penicillium*, the MIC was 2 mg / mL, achieving an inhibition rate of 76.33%; and against *Bacillus*, the MIC was 2 mg / mL, achieving an inhibition rate of 75.93%.

[0056] Comparative Example 6 The difference between this comparative example and Example 5 is that *Lactobacillus plantarum* SS18-119 was not added; only EGCG was used. The other steps were the same as in Example 1. In this comparative example, the minimum inhibitory concentration (MIC) of EGCG against *Escherichia coli* was 2 mg / mL, achieving an inhibition rate of 81.51%; against *Penicillium*, the MIC was 2 mg / mL, achieving an inhibition rate of 73.92%; and against *Bacillus*, the MIC was 2 mg / mL, achieving an inhibition rate of 73.90%. (See Table 1 and...) Figure 1-12 As shown, in Example 1, the combined bacterial agent of *Lactobacillus plantarum* SS18-119 and ellagic acid yielded a FICI value of 0.3125 < 0.5, indicating a synergistic antibacterial effect. Compared to Comparative Examples 1 and 4, Example 1 used 0.125 mg / mL ellagic acid and a probiotic concentration of 1.25 × 10⁻⁶. 8 When fermentation broth with CFU / mL is used in combination, the antibacterial rate is higher than that achieved by using ellagic acid and Lactobacillus plantarum SS18-119 alone, thus improving the antibacterial effect.

[0057] Example 2 used a combination of *Lactobacillus reuteri* Fullerton-9-35 and ellagic acid as a probiotic agent, achieving a FICI value of 0.5625, indicating a partial synergistic effect. Compared to Comparative Examples 2 and 4, Example 2 used 0.125 mg / mL ellagic acid and a probiotic concentration of 2.5 × 10⁻⁶. 8 When fermentation broth at CFU / mL is used in combination, the inhibition rate is higher than that achieved by using ellagic acid or Lactobacillus reuteri Fullarton-9-35 alone.

[0058] Example 3 used a combination of *Lactobacillus plantarum* SS18-5 and ellagic acid as a bacterial agent, achieving a FICI value of 0.625, indicating a partial synergistic effect. Compared to Comparative Examples 3 and 4, Example 3 used 0.25 mg / mL ellagic acid and a probiotic concentration of 2.5 × 10⁻⁶. 8 When fermentation broth at CFU / mL is used in combination, the inhibition rate is higher than that achieved by using ellagic acid or Lactobacillus plantarum SS18-5 alone.

[0059] Example 4 used a combination of *Lactobacillus plantarum* SS18-119 and chlorogenic acid, achieving a FICI value of 1.0, indicating a partial synergistic effect. Compared to Comparative Examples 1 and 5, Example 4 used 1 mg / mL of chlorogenic acid and a probiotic concentration of 2.5 × 10⁻⁶. 8 When fermentation broth at CFU / mL is used in combination, the inhibition rate is higher than that achieved by using chlorogenic acid or Lactobacillus plantarum SS18-119 alone.

[0060] Example 5 used a combination of *Lactobacillus plantarum* SS18-119 and EGCG, achieving a FICI value of 1.0, indicating a partial synergistic effect. Compared to Comparative Examples 1 and 6, Example 5 used 1 mg / mL of chlorogenic acid and a probiotic concentration of 2.5 × 10⁻⁶. 8 When fermentation broth at CFU / mL is used in combination, the inhibition rate is higher than that achieved by using EGCG or Lactobacillus plantarum SS18-119 alone.

[0061] In summary, the present invention uses the aforementioned space probiotic agent to combine space probiotics with plant extracts. The synergistic effect of the two effectively reduces the antibacterial concentration, improves the antibacterial and preservative effects, effectively reduces the risk of target bacteria developing tolerance to a single antibacterial component, and enhances the safety and stability of food preservation.

[0062] Table 1. Minimum inhibitory concentration and inhibition rate of products obtained in the examples and comparative examples.

[0063] Application Example 1 The inoculation concentration on beef was 1×10 6 Harmful microorganisms at CFU / mL, using 0.125 mg / mL ellagic acid and a probiotic concentration of 1.25 × 10⁻⁶ CFU / mL as in Example 1. 8 A microbial agent, prepared by combining CFU / mL of *Lactobacillus plantarum* SS18-119, was sprayed onto beef. After the beef surface was air-dried, it was refrigerated at 4°C for 5 days. Harmful microorganisms on the beef surface were then washed off, and the beef was inoculated into a culture medium for counting. Compared to the untreated group, the combined microbial agent, through the combined action of *Lactobacillus plantarum* SS18-119 and ellagic acid, reduced the number of *Escherichia coli* by 99%, *Penicillium* by 90%, and *Bacillus* by 90%.

[0064] Application Example 2 The inoculation concentration on lettuce was 1×10⁻⁶. 6 Harmful microorganisms at CFU / mL, using 0.125 mg / mL ellagic acid and a probiotic concentration of 1.25 × 10⁻⁶ CFU / mL as in Example 1. 8 A microbial agent, prepared by combining CFU / mL of *Lactobacillus plantarum* SS18-119, was sprayed onto lettuce. After the lettuce surface was air-dried, it was refrigerated at 4°C for 5 days. Harmful microorganisms on the lettuce surface were then washed off, and the lettuce was inoculated onto a culture medium for counting. Compared to the untreated group, the combined effect of *Lactobacillus plantarum* SS18-119 and ellagic acid reduced the number of *Escherichia coli*, *Penicillium*, and *Bacillus* by 99.9%, 99%, and 99%, respectively.

[0065] The embodiments described above are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

Claims

1. A space probiotic agent with antibacterial, antiseptic, and preservation functions, characterized in that: The space probiotic agent includes space probiotics and their fermentation products and plant extracts. The space probiotics are selected from one or more of Lactobacillus plantarum SS18-119, Lactobacillus reuteri Fullarton-9-35 and Lactobacillus plantarum SS18-5. The plant extracts are selected from one or more of chlorogenic acid, ellagic acid and epigallocatechin gallate.

2. The space probiotic agent according to claim 1, characterized in that: The concentration of space probiotics in the space probiotic agent is ≥1×10⁻⁶. 8 CFU / mL.

3. The space probiotic agent according to claim 1, characterized in that: The concentration of plant extracts in the space probiotic agent is 0.0625~2mg / mL.

4. The space probiotic agent according to claim 1, characterized in that: The space probiotics and their fermentation products are obtained by inoculating the space probiotics into a culture medium and culturing them at 37°C.

5. The space probiotic agent according to claim 1, characterized in that: The space probiotic agent is composed of *Lactobacillus plantarum* SS18-119 and its fermentation products, and ellagic acid, wherein the concentration of *Lactobacillus plantarum* SS18-119 is ≥1×10⁻⁶. 8 The concentration of ellagic acid is 0.1~2 mg / mL, and the concentration of ellagic acid is CFU / mL.

6. The method for preparing the space probiotic agent as described in any one of claims 1-5, characterized in that, The preparation method includes the following steps: S1. Inoculate space probiotics into a culture medium and culture at 37-42℃ to obtain fermentation liquid; S2. Mix the fermented bacterial liquid with plant extracts to obtain the space probiotic agent.

7. The preparation method according to claim 6, characterized in that: In step S1, the incubation time is 24~48h.

8. A food preservative, characterized in that, The food preservative includes the space probiotic agent as described in any one of claims 1-5.

9. A method for preserving food, comprising using the space probiotic agent as described in any one of claims 1-5, characterized in that, The preservation method includes the following steps: mixing space probiotics and their fermentation products with plant extracts and spraying them onto the surface of the food.

10. The application of the space probiotic agent as described in any one of claims 1-5 or the food preservative as described in claim 8 in food preservation.

Images