Lactobacillus plantarum for controlling bacterial and fungal diseases of fruits and vegetables and application thereof

Abstract

The application discloses a plant Lactiplantibacillus plantarum Yi-BC5 with a preservation number of GDMCC No: 67799, which shows strong inhibition on Pectobacterium carotovorum and Penicillium digitatum in vitro and in vivo, can significantly reduce the incidence and lesion diameter of pepper bacterial soft rot and citrus green mold; the Lactiplantibacillus plantarum Yi-BC5 can produce extracellular polysaccharide and other antibacterial metabolites, and the bacterial body and / or bacterial metabolite can be used for preparing products for inhibiting Pectobacterium carotovorum and / or Penicillium digitatum, and can be used for preparing products for preventing and treating bacterial diseases (including but not limited to pepper bacterial soft rot) and / or fungal diseases (including but not limited to citrus green mold) of fruits and vegetables. The Lactiplantibacillus plantarum Yi-BC5 can simultaneously control bacterial diseases and fungal diseases of fruits and vegetables after harvesting, has excellent disease control performance, provides an excellent antagonistic bacterial resource for postharvest preservation of fruits and vegetables, and lays a foundation for subsequent development of a new type of microbial bactericide.

Description

Technical Field

[0001] This invention belongs to the field of microbial technology and relates to an antagonistic bacterium that can simultaneously control bacterial and fungal diseases of fruits and vegetables and its application. Background Technology

[0002] Diseases caused by pathogenic microorganisms are called infectious diseases. The main pathogens of postharvest infectious diseases of fruits and vegetables are fungi and bacteria. Diseases during fruit storage and transportation are almost entirely caused by fungi. For leafy vegetables, bacteria are the primary pathogen causing rot.

[0003] Bacterial soft rot is a significant bacterial disease worldwide, primarily caused by bacteria of the genera *Pectobacterium* and *Dickeya*. *Pectobacterium carotovorum*, in particular, has a wide host range and can cause fruit and vegetable rot, leading to severe post-harvest losses. *Pectobacterium carotovorum* typically infects pre-harvest latently or directly invades the host post-harvest through natural openings or mechanical damage. In the early stages of infection, water-soaked lesions are clearly visible, which then rapidly expand, eventually leading to rotting of the infected area. my country, as a major chili-producing country and the world's largest producer, has an annual chili production exceeding 60 million tons. Soft rot, caused by *Pectobacterium carotovorum*, is one of the most devastating bacterial diseases affecting chili peppers after harvest.

[0004] Penicillium digitatum is an important pathogenic fungus that primarily causes green mold disease in citrus fruits. After infection, the fruit surface is rapidly covered with a bluish powdery substance, leading to fruit rot. my country is one of the world's largest producers of citrus fruits. However, green mold disease caused by Penicillium digitatum can result in losses of up to 90% during the post-harvest storage and transportation stage of citrus fruits.

[0005] Chemical fungicides are currently one of the main methods for controlling fruit and vegetable diseases. However, long-term use of chemical fungicides not only increases the drug resistance of pathogens and reduces their preservative and antiseptic effects, but also pollutes the environment and poses potential health risks. Therefore, new alternative methods are particularly important. Currently, biological control methods show great application potential. Yeasts and lactic acid bacteria are being studied as antagonists for postharvest biological control of fruits and vegetables. Although some antagonistic lactic acid bacteria have been reported to control postharvest bacterial or fungal diseases in fruits and vegetables, few antagonistic lactic acid bacteria can simultaneously control both bacterial and fungal diseases. Summary of the Invention

[0006] The purpose of this invention is to provide an antagonistic lactic acid bacteria that can simultaneously control bacterial and fungal diseases of fruits and vegetables, in order to provide a new solution for the prevention and control of fruit and vegetable diseases.

[0007] Based on research, the present invention provides the following technical solution:

[0008] 1. Lactiplantibacillus plantarum Yi-BC5, accession number GDMCCNo: 67799. Deposited on February 3, 2026 at Guangdong Provincial Center for Microbial Culture Collection (GDMCC, address: 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou).

[0009] 2. Extracellular polysaccharides produced by Lactobacillus plantarum Yi-BC5.

[0010] Furthermore, the extracellular polysaccharide produced by *Lactobacillus plantarum* Yi-BC5 can be prepared by the following method: *Lactobacillus plantarum* Yi-BC5 is inoculated into MRS liquid medium and cultured at 37°C. The supernatant is collected by centrifugation, trichloroacetic acid is added, and the mixture is allowed to stand overnight at 4°C. The supernatant is collected by centrifugation, anhydrous ethanol is added, and the mixture is allowed to stand overnight at 4°C. The precipitate is collected by centrifugation to obtain the crude extract of extracellular polysaccharide.

[0011] 3. Application of extracellular polysaccharides produced by *Lactobacillus plantarum* Yi-BC5 and / or *Lactobacillus plantarum* Yi-BC5 in the preparation of products for the prevention and control of bacterial and / or fungal diseases of fruits and vegetables.

[0012] The bacterial diseases of fruits and vegetables include, but are not limited to, pepper soft rot, and the fungal diseases of fruits and vegetables include, but are not limited to, citrus green mold.

[0013] 4. Application of *Lactobacillus plantarum* Yi-BC5 and / or the extracellular polysaccharide produced by *Lactobacillus plantarum* Yi-BC5 in the preparation of products that inhibit *Pectinobacterium carotenoides* and / or *Penicillium fingernail*.

[0014] The beneficial effects of this invention are as follows: This invention isolates *Lactobacillus plantarum* Yi-BC5 from the tissue slurry of fresh spinach leaves. Using *Pectinobacillus carotenoides* causing pepper soft rot as a representative bacterial disease of fruits and vegetables, and *Penicillium digitatum* causing citrus green mold as a representative fungal disease of fruits and vegetables, the in vitro antibacterial effect of *Lactobacillus plantarum* Yi-BC5 and its disease control effect in pepper and citrus fruits were investigated. The results showed that *Lactobacillus plantarum* Yi-BC5 exhibited strong inhibitory effects on both *Pectinobacillus carotenoides* and *Penicillium digitatum* both in vitro and in vivo, significantly reducing the incidence and lesion diameter of pepper soft rot and citrus green mold. Furthermore, *Lactobacillus plantarum* Yi-BC5 can produce antimicrobial metabolites such as extracellular polysaccharides. Its cells and / or contained metabolites can be used not only to prepare products that inhibit *Pectinobacillus carotenoides* and / or *Penicillium fingernail*, but also to prepare products for the prevention and control of bacterial diseases (including but not limited to pepper soft rot) and / or fungal diseases (including but not limited to citrus green mold) in fruits and vegetables, maintaining fruit and vegetable quality and reducing spoilage losses during storage and transportation. The *Lactobacillus plantarum* Yi-BC5 of this invention can simultaneously control postharvest bacterial and fungal diseases in fruits and vegetables, exhibiting excellent disease control performance. It provides an excellent antagonistic bacterial resource for postharvest preservation of fruits and vegetables, laying the foundation for the subsequent development of novel microbial fungicides. Attached Figure Description

[0015] Figure 1 This is the result of an in vitro antibacterial experiment on *Bacillus carotenoides* by the antagonistic bacterium Yi-BC5.

[0016] Figure 2 The results of the in vitro antibacterial experiment of antagonistic bacterium Yi-BC5 against Penicillium fingerling are presented.

[0017] Figure 3 This is a complete genome map of the antagonistic bacterium Yi-BC5.

[0018] Figure 4 The study aimed to investigate the disease control effects of the antagonistic bacterium Yi-BC5 and its metabolites on pepper soft rot.

[0019] Figure 5 To investigate the disease control effect of the antagonistic bacterium Yi-BC5 containing its metabolites on citrus green mold. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0021] In a preferred embodiment of the present invention, pepper soft rot caused by *Pectinobacillus carotensis* is used as a representative bacterial disease of fruits and vegetables, and citrus green mold caused by *Penicillium digitatum* is used as a representative fungal disease of fruits and vegetables. Both *Pectinobacillus carotensis* and *Penicillium digitatum* are preserved in the Food Storage and Logistics Laboratory of the College of Food Science, Southwest University.

[0022] Example 1: Screening and identification of antagonistic bacteria against *Carotene soft rot*

[0023] Antagonistic bacteria were screened using fresh fruits and vegetables sourced from Beibei District, Chongqing. The fruit and vegetable samples used and their codes are as follows: Small red chili pepper (XML), eggplant (QZ), Shanghai bok choy (SHQ), sweet potato leaves (SJ), bird's eye chili pepper (CTJ), red small red chili pepper (HM), taro (Y), tomato (XHS), bean sprouts (DY), green bell pepper (LJ), orange (CZ), apple (PG), grape (PU), lettuce tips (wsj), cilantro (X), green beans (DJ), Malabar spinach (MU), celery (QC), bok choy (XB), endive (KJ), romaine lettuce (YMC), scallion (CO), garland chrysanthemum (TH), fennel (HX), spinach (BC), red chili pepper (HL), Chinese cabbage (HC), spring sprouts (CY), daylily (H), and chives (JIU).

[0024] 1. Strains Isolation

[0025] Select fresh fruits and vegetables free from mechanical damage and disease. Vegetable sample: Take 10-50 g of leafy parts, grind them in a mortar and pestle until tissue fluid seeps out, and take 2-3 mL of tissue fluid as 10 g of sample. 0 Original sample solution; Fruit sample: After brushing the bacteria on the surface of the fruit into sterile physiological saline with a toothbrush or cotton swab, filter through a 0.22 μm filter membrane, then soak and wash the filter membrane in 2 mL of sterile physiological saline to resuspend the bacteria on the filter membrane in sterile physiological saline. The resulting bacterial suspension is used as 10. 0 The original sample solution was then diluted with sterile physiological saline. 0 The original sample solution was serially diluted 10-fold. 100 μL of each diluted sample solution was plated onto MRS agar plates and incubated at 37°C for 24–48 h. Based on colony morphology, color, and size, suspected single colonies were picked and streaked onto new MRS agar plates for purification. The purified strains were inoculated into MRS liquid medium and cultured at 37°C with shaking, then preserved in glycerol tubes at -40°C for subsequent screening and identification. A total of 168 strains were isolated.

[0026] 2. Screening of antagonistic bacteria

[0027] The isolated strains were first screened using an in vitro double-layer plate method to identify antagonistic bacteria with inhibitory activity against *Pectinobacterium carotene*. The resulting antagonistic bacteria were then re-screened using an in vivo disease resistance experiment on pepper fruits.

[0028] Initial screening: The strains to be screened were streaked onto MRS agar plates and incubated at 37°C for 48 h; a single colony was picked up with an inoculation loop and two parallel straight lines, each about 2 cm long and 1.5 cm apart, were drawn in the middle of the MRS agar plate, and then the plate was incubated at 37°C for 48 h; the freshly cultured *Pectinobacter carotene* was first prepared to a bacterial concentration of OD0.05 using sterile physiological saline. 600 nm The bacterial suspension with a concentration of 0.5 was further diluted 10,000 times to obtain a bacterial suspension of carrot soft rot pathogen. The bacterial suspension of carrot soft rot pathogen was mixed with LB medium that had not solidified under heat and immediately poured 10 mL onto the above streak plate. After incubation at 37°C for 48 h, the antibacterial data were recorded. Three parallel experiments were performed for each strain to be screened.

[0029] Secondary screening: Remove the stems from fresh, intact chili peppers, soak them in a 2% sodium hypochlorite solution for 5 minutes, wash them three times, and air dry. Make two holes on the surface of each chili pepper using a sterile punch. Add 20 µL of the antagonistic bacterial suspension with antibacterial activity (screened out in the initial screening) to each hole, and air dry. Then add another 20 µL of the above-mentioned carrot soft rot pathogen suspension to each hole and air dry. Place the chili peppers in a perforated container and store them in a constant temperature and humidity incubator (25℃, 85% humidity) for 4 days, observing disease development daily. Perform three parallel experiments for each strain, with five chili peppers per parallel experiment. A control group was also set up, using 20 µL of sterile physiological saline instead of the bacterial suspension for the screening.

[0030] Results: Of the 168 isolated strains, 64 showed antibacterial activity against *Pectinobacterium carotenoides* in in vitro antibacterial experiments. Of these 64 strains, 21 showed antagonistic effects against *Pectinobacterium carotenoides* in in vivo disease resistance experiments on pepper fruits. The in vitro antibacterial results of these 21 antagonistic strains are shown in Table 1. The in vitro antibacterial effect of strain BC5 is shown in... Figure 1 As shown in the figure. Among them, the three strains with the best antibacterial effect against *Pectinobacterium carotene* in vitro and in vivo are numbered H2, BC5, and SJ1, respectively.

[0031] Table 1. Results of in vitro antibacterial experiments against *Pectinobacterium carotene*.

[0032]

[0033] 3. Identification of antagonistic bacteria

[0034] The 21 antagonistic bacteria strains were amplified with 16S rDNA using universal primers 27F and 1492R. The PCR products were sequenced by Shanghai Sangon Biotech Co., Ltd. The sequencing results were submitted to NCBI (www.ncbi.nlm.nih.gov) for BLAST comparison analysis to determine the strain species.

[0035] The results showed that among the 21 antagonistic bacteria, strain BC4-1 was Leuconostoc lactis, strain BC5 was Lactiplantibacillus plantarum, strain SJ1 was Weissella cibaria, strain H2 was Leuconostoc lactis, strain PG4 was Weissella confuse, and the remaining strains all belonged to the Burkholderia genus.

[0036] Example 2: Screening and identification of antagonistic bacteria between *Carotene soft rot pectinobacterium* and *Penicillium fingernail*

[0037] 1. Screening of antagonistic bacteria

[0038] Sixty-four strains that showed certain in vitro antibacterial activity against *Pectinobacterium carotenoides*, initially screened in Example 1, were screened using an in vitro double-layer plate method to identify antagonistic bacteria with antibacterial activity against *Penicillium digitatum*. The strains to be screened were streaked onto MRS agar plates and incubated at 37°C for 48 h. Single colonies were picked with an inoculation loop and two parallel lines approximately 2 cm long were drawn along the center of the MRS agar plate, with a spacing of approximately 1.5 cm between the two lines. The plates were then incubated at 37°C for 48 h. A spore suspension of freshly cultured *Penicillium digitatum* was prepared and mixed with incubated, non-solidified PDA medium (final spore concentration 1 × 10⁻⁶). 5 (CFU / mL), immediately pour 10 mL onto the above streak plate, incubate at 25℃ for 72 h and record the antibacterial data; perform 3 parallel experiments for each strain to be screened.

[0039] Results: Among the 64 strains that showed certain in vitro antibacterial activity against *Pectinobacterium carotenoides*, 14 strains also showed some antibacterial activity against *Penicillium digitatum* in in vitro antibacterial experiments. The results of these 14 strains' in vitro antibacterial experiments are shown in Table 2 and... Figure 2 As shown.

[0040] Table 2 Results of in vitro antibacterial experiments against Penicillium digitatum

[0041]

[0042] 2. Identification of antagonistic bacteria

[0043] The 14 antagonistic bacteria strains were amplified with 16S rDNA using universal primers 27F and 1492R. The PCR products were sequenced by Shanghai Sangon Biotech Co., Ltd. The sequencing results were submitted to NCBI (www.ncbi.nlm.nih.gov) for BLAST comparison analysis to determine the strain species.

[0044] The results showed that among the 14 antagonistic bacteria, strains CTJ-5, wsj-1, SHQ-1-2, and SHQ-2 were all Weissella cibaria; strains LJ-4, CTJ-4, SHQ-1-1, and QZ-2 were all Weissella confusa; strains LJ-1, LJ-5, and LJ-6 were all Weissella fermenti; strain CTJ-2 was Leuconostocmesenteroides subsp. Dextranicum; and strain wsj-5 was Leuconostoc mesenteroides.

[0045] As shown in Tables 1 and 2, only strain BC5 exhibited antagonistic effects against both *Pectinobacterium carotenoides* and *Penicillium fingernail* in both in vitro antibacterial and in vivo disease resistance experiments. Its 16S rDNA, analyzed by BLAST, showed a similarity of 97.80% (>97%) with *Lactiplantibacillus plantarum*, thus identifying it as *Lactiplantibacillus plantarum*. Strain BC5 was named *Lactiplantibacillus plantarum* Yi-BC5 and deposited on February 3, 2026, at the Guangdong Provincial Microbial Culture Collection Center (GDMCC, address: 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou), with accession number GDMCC No: 67799.

[0046] Example 3: Identification of antimicrobial metabolites of antagonistic bacterium Yi-BC5

[0047] The antagonistic bacterium Yi-BC5 was inoculated into MRS liquid medium and cultured to the logarithmic phase. The bacterial cells were centrifuged and then subjected to Illumina HiSeq next-generation genome sequencing by Beijing Novogene Technology Co., Ltd. The obtained genome sequences were used to predict bacteriocins in the BAGEL4 database (http: / / bagel4.molgenrug.nl / index.php) and to analyze and identify antimicrobial secondary metabolites in the antiSMASH database (https: / / antismash.secondarymetabolites.org / #! / start).

[0048] The whole genome circle of the antagonistic bacterium Yi-BC5 is as follows: Figure 3 As shown, the genome size is 643,839 bp, and the GC content is 52%. Based on the antiSMASH database prediction (Table 3), this antagonistic bacterium can produce exopolysaccharides (EPS) but not bacteriocins. Furthermore, the EPS product prediction shows higher similarity compared to other secondary metabolites such as fatty acids. Extracellular polysaccharides from lactic acid bacteria have been shown to have antitumor, antioxidant, and antibacterial effects; therefore, it is predicted that the antagonistic bacterium Yi-BC5 exerts its antagonistic effect through extracellular polysaccharides.

[0049] Table 3. Prediction results from the antiSMASH database

[0050]

[0051] Example 4: The control effect of antagonistic bacterium Yi-BC5 cells and its metabolites on pepper soft rot.

[0052] After culturing the antagonistic bacteria Yi-BC5 overnight in MRS liquid medium, centrifuging at 8000 rpm for 10 min, resuspending in sterile physiological saline, and adjusting the bacterial concentration to OD0.05 600nm =1.0, to obtain an antagonistic bacterial suspension; inoculate the antagonistic bacteria Yi-BC5 at a 3% inoculum into MRS liquid medium, incubate at 37℃ for 48 h, centrifuge at 5000 rpm for 20 min to collect the supernatant, add trichloroacetic acid to a final concentration of 4%, let stand overnight at 4℃, centrifuge again at 5000 rpm for 20 min to collect the supernatant, add three volumes of anhydrous ethanol, let stand overnight at 4℃, centrifuge again at 5000 rpm for 20 min to collect the precipitate, to obtain crude extracellular polysaccharide extract, add sterile water at a ratio of 100:1 to dissolve, to obtain an extracellular polysaccharide solution; mix the obtained antagonistic bacterial suspension and the obtained extracellular polysaccharide solution at a volume ratio of 1:1 to obtain a solution containing bacterial metabolites.

[0053] Remove the stems from fresh, intact chili peppers, soak them in a 2% sodium hypochlorite solution for 5 minutes, rinse, and air dry. Make two holes on the surface of each chili pepper using a sterile punch. Add 20 µL of antagonistic bacterial suspension to each hole in the BC5 group, 20 µL of bacterial metabolite solution to each hole in the BC5+ polysaccharide group, and 20 µL of physiological saline to each hole in the control group. After air drying, add a 10% sodium hypochlorite solution to each hole in all three groups. 4 20 µL of CFU / mL *Pectinobacterium carotene* suspension was air-dried and then placed in a perforated container in a constant temperature and humidity incubator (25℃, 85% humidity) for 4 days. The disease incidence on the pepper fruits was observed daily. Three parallel experiments were conducted in each group, with 10 pepper fruits in each parallel experiment.

[0054] See results Figure 4 On day 1 of storage, all three treatment groups developed the disease. The incidence rates in the control group, BC5 group, and BC5+polysaccharide group were 88±16%, 30±18%, and 38±16%, respectively. The incidence rates in the BC5 group and BC5+polysaccharide group were significantly lower than those in the control group (p<0.001). On day 2 of storage, the incidence rates in the control group, BC5 group, and BC5+polysaccharide group were 95±9%, 67±8%, and 62±10%, respectively. The incidence rates in the BC5 group (p<0.05) and BC5+polysaccharide group (p<0.01) were significantly lower than those in the control group. The lesion diameters in the control group, BC5 group, and BC5+polysaccharide group were 5.83±0.59, 2.89±0.89, and 3.01±1.32 cm, respectively. The lesion diameters in the BC5 group (p<0.001) and BC5+polysaccharide group (p<0.01) were significantly lower than those in the control group. On the third day of storage, the incidence rates of the control group, BC5 group, and BC5+polysaccharide group were 93±12%, 57±18%, and 52±15%, respectively, with the incidence rate in the BC5+polysaccharide group being significantly lower than that in the control group (p<0.05). The lesion diameters in the control group, BC5 group, and BC5+polysaccharide group were 9.60±0.68, 5.99±1.29, and 6.03±0.99 cm, respectively, with the lesion diameters in the BC5 group and BC5+polysaccharide group being significantly lower than those in the control group (p<0.001). On the third day of storage, most of the pepper fruits in the control group were infected with rot, with soft, yellow, and difficult-to-pick tissue, yellow juice oozing out, and a foul odor. In contrast, only some pepper fruits in the BC5 group and BC5+polysaccharide group showed signs of rot, and the overall fruit remained firm. Therefore, the antagonistic bacterium Yi-BC5 and its metabolites have a certain inhibitory effect on *Pectinobacillus carotenoides*, significantly reducing the incidence and lesion diameter of pepper soft rot.

[0055] Example 5: Disease control effect of antagonistic bacteria Yi-BC5 containing metabolites on citrus green mold.

[0056] Freshly cultured Penicillium finger mold was prepared to a concentration of 1×10⁻⁶. 7 A spore suspension of *Penicillium digitatum* was prepared by dispersing spores at CFU / mL. Fresh, disease-free citrus fruits were destemmed, soaked in a 2% sodium hypochlorite solution for 5 minutes, washed, and air-dried. The equatorial surface of each fruit was disinfected by wiping with 75% alcohol. Two symmetrical holes (3 mm in diameter and 3 mm deep) were then punched at the equatorial region of each fruit using a sterile punch. 20 µL of the bacterial metabolite solution prepared in Example 4 was added to each hole in the BC5+ polysaccharide group, while 20 µL of sterile water was added to each hole in the control group (CK). After air-drying, 10 μL of *Penicillium digitatum* suspension was added to each hole in both groups. Once the fruit had fully absorbed the solution, all fruits were individually packaged in plastic bags and stored at 25°C and 95% relative humidity for 5 days. Disease incidence was observed daily. Three parallel experiments were conducted for each group, with 10 citrus fruits in each parallel experiment.

[0057] See results Figure 5 No disease was observed in the citrus fruits of either group on days 1 and 2 of storage. On day 3 of storage, disease developed in both groups. The incidence rates in the control group and the BC5+ polysaccharide group were 98±6% and 65±5%, respectively, and the lesion diameters were 3.38±0.21 and 1.31±0.28 cm, respectively. The incidence rate and lesion diameter in the BC5+ polysaccharide group were significantly lower than those in the control group (p<0.0001). On day 4 of storage, the incidence rates in the control group and the BC5+ polysaccharide group were 98±3% and 90±5%, respectively, and the lesion diameters were 6.12±0.34 and 3.03±0.27 cm, respectively. The lesion diameter in the BC5+ polysaccharide group was significantly lower than that in the control group (p<0.0001). On day 5 of storage, the lesion diameters in the control group and the BC5+ polysaccharide group were 8.80±0.65 and 5.11±0.32 cm, respectively. The lesion diameter in the BC5+ polysaccharide group was significantly lower than that in the control group (p<0.0001). On the fifth day of storage, almost all citrus fruits in the control group were infected by the pathogen. Numerous visible hyphae and spores were present at the wound sites, and water-soaked lesions appeared on most parts of the fruit. The fruit was soft and difficult to handle. In contrast, while the citrus fruits in the BC5+polysaccharide group showed water-soaked lesions near the wounds, no hyphae or spores were present. The entire fruit was free of mold and was firmer and easier to handle. This indicates that the metabolites of the antagonistic bacterium Yi-BC5 have a certain inhibitory effect on Penicillium fingering, significantly reducing the incidence and lesion diameter of citrus green mold.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described with reference to preferred embodiments, those skilled in the art should understand that various changes in form and detail can be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. Lactiplantibacillus plantarum Yi-BC5, preservation number GDMCC No:67799.

2. The extracellular polysaccharide produced by *Lactobacillus plantarum* Yi-BC5 as described in claim 1.

3. The extracellular polysaccharide produced by *Lactobacillus plantarum* Yi-BC5 according to claim 2, characterized in that... The following method was used to prepare the product: Yi-BC5 of *Lactobacillus plantarum* was inoculated into MRS liquid medium and cultured at 37°C. The supernatant was collected by centrifugation, and trichloroacetic acid was added. The mixture was allowed to stand overnight at 4°C. The supernatant was collected by centrifugation, and anhydrous ethanol was added. The mixture was allowed to stand overnight at 4°C. The precipitate was collected by centrifugation to obtain the crude extract of extracellular polysaccharides.

4. The use of the extracellular polysaccharide produced by *Lactobacillus plantarum* Yi-BC5 as described in claim 1 and / or *Lactobacillus plantarum* Yi-BC5 as described in claim 2 or 3 in the preparation of products for the prevention and control of bacterial and / or fungal diseases of fruits and vegetables.

5. The application as described in claim 4, characterized in that, The bacterial disease of fruits and vegetables is pepper soft rot, and the fungal disease of fruits and vegetables is citrus green mold.

6. The use of the extracellular polysaccharide produced by *Lactobacillus plantarum* Yi-BC5 as described in claim 1 and / or *Lactobacillus plantarum* Yi-BC5 as described in claim 2 or 3 in the preparation of products that inhibit *Pectobacterium carotovorum* and / or *Penicillium digitatum*.

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