Lactobacillus plantarum expressing signal molecule AI-2 and application thereof

Abstract

The present invention discloses a Lactobacillus plantarum expressing a signal molecule AI-2 and its application, and belongs to the field of microbial technology. The present invention is to provide a new lactic acid bacteria that can produce diamine oxidase in high yield and has a strong degradation ability for putrescine, cadaverine and histamine in air-dried sausages, Lactobacillus plantarum expressing the quorum sensing signal molecule AI-2. The present invention discloses a Lactobacillus plantarum expressing the signal molecule AI-2, and the Lactobacillus plantarum is named Lactobacillus plantarum SH7, with a preservation number of CGMCC NO.28113, and is deposited in the China General Microbiological Collection Center on August 7, 2023. Lactobacillus plantarum SH7 has significant amine-reducing properties, and the extracellular diamine oxidase activity is 615.24U / g protein, which can be used as a starter to reduce the content of biogenic amines in the production of fermented meat products.

Description

Technical Field

[0001] The invention belongs to the technical field of microorganisms, and in particular relates to a plant lactobacillus expressing a signal molecule AI-2 and an application thereof. Background Art

[0002] Biogenic amines are low molecular weight nitrogen-containing organic compounds that are widely found in fermented foods. According to the amount of ammonia in them, biogenic amines can be divided into monoamines, diamines and polyamines; according to the chemical structure of biogenic amines, they can be divided into fatty amines, aromatic amines and heterocyclic amines. Biogenic amines widely found in food include tryptamine, phenylethylamine, putrescine, cadaverine, histamine, tyramine, spermine and spermidine, among which putrescine, cadaverine and histamine are the main biogenic amines in fermented air-dried sausages. Usually, the intake of a small amount of biogenic amines will not affect human health, and biogenic amines can be degraded by amino oxidases in the human intestine; however, when foods with high biogenic amine content are consumed or the body's detoxification ability is inhibited or interfered with, it will have a serious impact on human health. Biogenic amines in food are inseparable from the quality and safety of food, and it is also one of the important indicators for judging food spoilage.

[0003] Biogenic amines are low molecular weight nitrogen-containing organic compounds that are widely found in fermented foods. In fermented foods, biogenic amines are mainly formed through the second pathway. Usually, consuming a small amount of biogenic amines will not affect human health, as biogenic amines can be degraded by amino oxidases in the human intestine; however, consuming foods high in biogenic amines or when the body's detoxification ability is inhibited or interfered with can have serious effects on human health. After degradation, biogenic amines produce low-toxic products such as aldehydes, ammonia, and hydrogen peroxide, which are transferred to cellular metabolism, thereby completing the degradation of biogenic amines. Summary of the invention

[0004] The purpose of the present invention is to provide a new lactic acid bacteria strain SH7 expressing the quorum sensing signal molecule AI2, which can produce diamine oxidase in high yield and has strong degradation ability for putrescine, cadaverine and histamine in air-dried intestines.

[0005] The present invention provides a Lactobacillus plantarum (Lactobacillus Plantarum) expressing a signal molecule AI-2. The Lactobacillus plantarum is named as Lactobacillus plantarum SH7, has a preservation number of CGMCC NO.28113, is deposited in the China General Microorganism Collection Center, and the preservation time is August 7, 2023.

[0006] The present invention provides the above-mentioned microbial preparation of Lactobacillus plantarum.

[0007] The present invention provides the use of the above-mentioned Lactobacillus plantarum or the above-mentioned microbial preparation in highly expressing the signal molecule AI-2.

[0008] The present invention provides the use of the above-mentioned Lactobacillus plantarum or the above-mentioned microbial preparation in degrading biogenic amines.

[0009] It is further defined that the biogenic amines are putrescine, cadaverine and histamine.

[0010] The present invention provides the use of the plant lactobacillus or the microbial preparation in degrading biogenic amines and in producing diamine oxidase.

[0011] The diamine oxidase is further defined as an intracellular diamine oxidase or an extracellular diamine oxidase.

[0012] The present invention provides application of the above-mentioned Lactobacillus plantarum or the above-mentioned microbial preparation in preparing fermented sausage products.

[0013] The present invention provides a method for degrading biogenic amines. The method comprises reacting the above-mentioned Lactobacillus plantarum in a reaction solution containing biogenic amines at 37° C. for 3 days.

[0014] The present invention provides a method for producing diamine oxidase, wherein the plant lactobacillus is cultured in an MRS culture medium at 37° C. for 16 hours.

[0015] Beneficial effects: The expression level of AI-2, a quorum sensing signal molecule of Lactobacillus plantarum SH7, is high, and it has the ability to significantly reduce biogenic amines (P<0.05). It has different degrees of degradation effects on eight biogenic amines, among which the degradation rates of putrescine, cadaverine and histamine are more significant, at 70.46%, 61.11% and 51.41% respectively, and the total biogenic amine degradation rate is 46.40%. It has significant amine reduction characteristics, and the intracellular diamine oxidase activity is 615.24U / g protein. It can be used as a fermentation agent to reduce the content of biogenic amines in the production of fermented meat products.

[0016] [Proof of Biological Deposit] The plant lactobacillus SH7 of the present invention is deposited in the General Microbiology Center (CGMCC) of the China Microbiological Culture Collection Administration, address: Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. Its strain deposit number is: CGMCC NO.28113, and the deposit date is August 7, 2023.

[0017] Sake Lactobacillus MDJ6 was isolated from traditional fermented air-dried sausage by the College of Food Science and Engineering of Northeast Agricultural University and deposited in the General Microbiology Center (CGMCC) of the China Culture Collection Administration, located at the Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. Its strain collection number is: CGMCC No.25287, and the storage date is July 13, 2022. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1This is the result diagram of relative fluorescence intensity value of lactic acid bacteria;

[0019] Figure 2 The results of intracellular and extracellular diamine oxidase activity of the strain are shown in the figure;

[0020] Figure 3 This is the result diagram of the degradation rate of putrescine, cadaverine and histamine by Lactobacillus plantarum SH7;

[0021] Figure 4 This is the result of the biogenic amine content in the air-dried intestines on the 9th day of fermentation;

[0022] Figure 5 This is the result of the extracellular diamine oxidase activity of Lactobacillus plantarum SH7 after adding AI-2 precursor;

[0023] Figure 6 This is a graph showing the degradation rate of putrescine, cadaverine and histamine by adding AI-2 precursor Lactobacillus plantarum SH7. DETAILED DESCRIPTION

[0024] MRS broth medium: peptone 10.0 g, beef extract powder 8.0 g, yeast extract powder 4.0 g, glucose 20.0 g, dipotassium hydrogen phosphate 2.0 g, diammonium hydrogen citrate 2.0 g, sodium acetate 5.0 g, magnesium sulfate 0.2 g, manganese sulfate 0.04 g, Tween 80 1.0 g, distilled water 1000 mL, pH = 5.7 ± 0.2.

[0025] Example 1. Method for isolating Lactobacillus plantarum that produces high-yield quorum sensing signal molecule AI-2

[0026] 1. Screening process of lactic acid bacteria with high production of quorum sensing signal molecule AI-2: V. harveyi BB170 (purchased from Shanghai Collection Biotechnology Center, number SHBCC D24812) was inoculated into AB medium (17.5 g sodium chloride, 12.3 g magnesium sulfate and 2.0 g acid hydrolyzed casein per liter) at 2%, and cultured at 30°C and 120 r / min with shaking until the second generation (OD600 nm value between 0.7-1.2), and the V. harveyi BB170 culture medium was diluted with fresh AB medium at 1:5000 (v / v), mixed and set aside.

[0027] Two strains of lactic acid bacteria (L. plantarum SH7, Latilactobacillus sakeie MDJ6) isolated from air-dried sausage were inoculated into MRS medium and activated for 3 generations to prepare lactic acid bacteria culture solution, V. harveyi BB170 culture solution, AB culture medium and MRS liquid culture medium. After centrifugation at 8000r / min (4°C) for 5min, the bacterial mud was discarded and filtered with a 0.22μm sterile membrane to remove impurities, and the sterile supernatant of the test strain culture solution, the positive control (sterile supernatant of V. harveyi BB170 culture solution), the negative control (sterile supernatant of AB culture medium), and the medium control (sterile supernatant of MRS liquid culture medium) were obtained. The sample to be tested, the positive, negative, and medium controls were mixed with the diluted V. harveyi BB170 bacterial solution at 1:100 (v / v) and continued to shake and culture. The fluorescence intensity value was measured every 30min within 0-6h. The fluorescence intensity of each sample was measured when the fluorescence intensity value of the negative control reached the lowest point (at 3.0 hours), and the relative fluorescence intensity was calculated to represent the activity of the signal molecule AI-2.

[0028] Relative fluorescence intensity calculation formula:

[0029] Formula (1) Relative fluorescence intensity of the Vibrio positive control group = fluorescence intensity value of the positive control / fluorescence intensity value of the negative control;

[0030] Formula (2): relative fluorescence intensity of lactic acid bacteria = fluorescence intensity value of the sample to be tested / fluorescence intensity value of the medium control.

[0031] Three strains (MDJ6 and SH7) with higher relative fluorescence intensity than V. harveyi BB170 were screened.

[0032] Identification of high-yield quorum sensing signal molecule AI-2 lactic acid bacteria: The strain was subjected to 16S rRNA molecular biological identification, and the primers were 27F (5'-AGAGTTTGATCCTGGCTCAG-3', SEQ ID NO.1) and 1492R (5'-GGTTACCTTGTTACGACTT-3', SEQ ID NO.2). Sequence alignment was performed on the website of the National Center for Biotechnology Information (NCBI) (https: / / blast.ncbi.nlm.nih.gov / Blast.cgi) to obtain the identification results.

[0033] 2. Determination of diamine oxidase activity in culture medium: Two strains of aminogen-reducing lactic acid bacteria (Lactobacillus plantarum SH7 and Lactobacillus plantarum MDJ6) with strong signal molecule AI-2 production were respectively subjected to extracellular and intracellular diamine oxidase activity determination (using diamine oxidase DAO kit, Nanjing Jiancheng Bioengineering Institute). After the two strains of aminogen-reducing lactic acid bacteria were activated for 3 generations in MRS culture medium, they were centrifuged at 4°C and 8000r / min for 10min, and the supernatant was salted out with 70% ammonium sulfate to extract protein. After being placed at 4°C for 1h to fully extract, the supernatant was discarded and the obtained protein was dissolved in an equal volume of phosphate buffer to determine the protein concentration and extracellular diamine oxidase activity; the above centrifuged bacterial sludge was washed twice with phosphate buffer and resuspended in an equal volume of phosphate buffer, and 0.02mmol / L of protease inhibitor phenylmethylsulfonyl fluoride was added, and the cells were broken on an ultrasonic disruptor under ice bath, 3s on, 3s off, and the alternating breaking cycle was 15min in total. The broken cells were centrifuged at 4°C and 13,000 r / min for 10 min, and the protein concentration and intracellular diamine oxidase activity were determined using the Bradford protein content detection kit (Shanghai Jingkang Bioengineering Co., Ltd.).

[0034] 3. Determination of the degradation ability of Lactobacillus plantarum SH7 on putrescine, cadaverine and histamine in culture medium: After Lactobacillus plantarum SH7 was inoculated into MRS culture medium for activation for 3 generations, it was inoculated into MRS culture medium containing biogenic amines (putrescine, cadaverine and histamine were added to MRS culture medium at a volume ratio of 2%), and cultured at 37°C for 3 days. The four bacterial solutions were centrifuged at 4°C and 6000r / min for 10min, 1mL of the centrifuged bacterial solution was taken into a test tube, and 9mL of 20% TCA solution was added for extraction. The biogenic amine content was determined in accordance with the first method of liquid chromatography in GB 5009.208-2016 "Determination of biogenic amines in food" for alcoholic beverages and condiments (vinegar and soy sauce).

[0035] Calculation method of biogenic amine degradation rate:

[0036]

[0037] Where: C0 is the concentration of biogenic amines in the control culture medium (mg / L); C1 is the concentration of biogenic amines in the test strain culture medium (mg / L).

[0038] Production of air-dried sausage

[0039] Ingredients: 9.0kg lean meat (pork tenderloin), 1.0kg fat (pork back fat), 0.30kg koji wine, 0.20kg salt, 0.0090kg sodium nitrite, 0.5kg granulated sugar, 0.15kg MSG, 0.05kg mixed seasoning (Shiyitang dry sausage material).

[0040] Preparation of starter culture: Lactobacillus plantarum SH7 was subcultured twice in MRS medium and then cultured at 37°C for 18 h. ×g After centrifugation for 5 minutes, set aside. When adding fermentation agent, the amount of lactic acid bacteria added is 10 6 CFU / g minced meat.

[0041] Process flow: raw meat (remove connective tissues such as lymph, tendons, and blood vessels) → dicing (1cm3 of diced meat) → marinating (adding salt and seasonings, etc.) → adding leavening agent and DPD → mixing stuffing → filling (length 20cm, diameter 3cm) → fermentation and air drying (temperature 25±2℃, humidity 65±5%).

[0042] Determination of biogenic amine content in air-dried sausage: The biogenic amine content in air-dried sausage was determined in accordance with the first method of liquid chromatography for aquatic products and meat in GB 5009.208-2016 "Determination of biogenic amines in food". BA content is expressed in mg / kg.

[0043] Results: From Figure 1 It can be seen that one of the two lactic acid bacteria strains has a higher ability to produce the signal molecule AI-2 than the positive control V.harveyi BB170. One lactic acid bacteria strain SH7 has a significantly higher ability to produce the signal molecule AI-2 than the other lactic acid bacteria (P<0.05).

[0044] Results: Figure 2 As shown in the data and Table 1, both lactic acid bacteria strains have amine oxidase activity both inside and outside the cells, especially Lactobacillus plantarum SH7, whose extracellular diamine oxidase activity (615.24U / g protein) was significantly higher than that of Lactobacillus sakei MDJ6 (P<0.05), and its intracellular diamine oxidase activity was also higher than that of Lactobacillus sakei MDJ6 (72.39U / g protein; P>0.05), indicating that this strain has a strong ability to reduce cadaverine, putrescine and histamine and has a certain potential for reducing amines in air-dried sausage.

[0045] Table 1 Intracellular and extracellular diamine oxidase activities of strains

[0046] Diamine oxidase (U / g protein) Intracellular Extracellular Lactobacillus sakei MDJ6 <![CDATA[63.28±5.04 b ]]> <![CDATA[425.17±11.25 b ]]> Lactobacillus plantarum SH7 <![CDATA[72.39±5.96 a ]]> <![CDATA[615.24±17.32 a ]]>

[0047] Note: Different letters in the same column indicate significant differences among samples (P<0.05).

[0048] Results: From Figure 3 It can be seen and shown in Table 2 that Lactobacillus plantarum SH7 has a strong ability to degrade putrescine, cadaverine and histamine, among which the highest degradation abilities for putrescine, cadaverine and histamine are 86.71%, 51.56% and 63.12%, respectively, indicating that the strain has a strong ability to degrade amines and has a certain potential for degrading amines in air-dried sausages.

[0049] Table 2 The ability of Lactobacillus plantarum SH7 to degrade putrescine, cadaverine and histamine

[0050] Cultivation time (h) Putrescine Cadaverine histamine 12 <![CDATA[81.54±0.79 Da ]]> <![CDATA[30.64±2.15 Dc ]]> <![CDATA[50.41±0.52 Cb ]]> 24 <![CDATA[63.67±0.58 Ca ]]> <![CDATA[37.38±2.98 Cc ]]> <![CDATA[53.24±0.67 Cb ]]> 36 <![CDATA[84.54±0.75 BCa ]]> <![CDATA[44.24±0.60 Bc ]]> <![CDATA[58.96±0.95 Bb ]]> 48 <![CDATA[84.60±0.82 BCa ]]> <![CDATA[48.73±1.10 ABc ]]> <![CDATA[60.00±1.68 ABb ]]> 60 <![CDATA[86.71±1.53 Aa ]]> <![CDATA[48.14±1.59 ABc ]]> <![CDATA[60.56±3.97 ABb ]]> 72 <![CDATA[85.90±0.38 ABa ]]> <![CDATA[51.56±1.39 Ac ]]> <![CDATA[63.12±1.10 Ab ]]>

[0051] Note: Different lowercase letters indicate significant differences among different biogenic amines, and different uppercase letters indicate significant differences among different culture times for the same biogenic amine (P<0.05).

[0052] Example 2. Preparation of microbial preparation of Lactobacillus plantarum SH7

[0053] 1. Activation of Lactobacillus plantarum:

[0054] Take 100-300 μL of the Lactobacillus plantarum SH7 bacterial solution in the glycerol tube and inoculate it into 500-1000 mL of MRS broth medium. Incubate at 37°C for 24-48 hours. Repeat this step 2-4 times to obtain the activated Lactobacillus plantarum bacterial solution. Centrifuge the activated bacterial solution, discard the supernatant, wash with sterile saline and resuspend, centrifuge and discard the supernatant, repeat this step 2-3 times to obtain a bacterial concentration of 10 6 -10 7 CFU / g of active bacterial sludge.

[0055] 2. Preparation of bacterial powder biological preparations:

[0056] Skim milk was selected as a freeze-drying protective agent, and the bacterial sludge obtained in the previous step and the skim milk were mixed at a mass ratio of 1:10 to obtain a bacterial cell concentration of 10 5 -10 6 CFU / mL skim milk suspension of Lactobacillus plantarum SH7 was pre-cultured at 37°C for 2 hours and then pre-frozen in a -40°C refrigerator for about 5-7 hours. After pre-freezing, it was freeze-dried in a vacuum freeze dryer. 5 -10 7 CFU / g of freeze-dried Lactobacillus plantarum SH7 biological preparation.

[0057] Directly press the plant lactobacillus biological preparation for 10 6 The added amount of CFU / g is added to the raw meat filling, mixed, enema, and fermented at 25±2°C until mature, so as to obtain a fermented sausage product containing plant lactobacillus biological preparation.

[0058] Example 4. Application of Lactobacillus plantarum SH7

[0059] 1. Production of air-dried sausage

[0060] Ingredients: 9.0kg lean meat (pork tenderloin), 1.0kg fat (pork back fat), 0.30kg koji wine, 0.20kg salt, 0.0090kg sodium nitrite, 0.5kg granulated sugar, 0.15kg MSG, 0.05kg mixed seasoning (Shiyitang dry sausage material).

[0061] Preparation of starter culture: Lactobacillus plantarum SH7 was subcultured twice in MRS medium and then cultured at 37°C for 18 h. ×g After centrifugation for 5 minutes, set aside. When adding fermentation agent, the amount of lactic acid bacteria added is 10 6 CFU / g minced meat.

[0062] Process flow: raw meat (remove connective tissues such as lymph, tendons, and blood vessels) → dicing (1cm3 of diced meat) → marinating (adding salt and seasonings, etc.) → adding leavening agent → mixing stuffing → filling (length 20cm, diameter 3cm) → fermentation and air drying (temperature 25±2℃, humidity 65±5%).

[0063] Determination of the content of biogenic amines in air-dried sausages: The content of biogenic amines in air-dried sausages was determined in accordance with the first method of liquid chromatography for aquatic products and meat in GB 5009.208-2016 "Determination of biogenic amines in food".

[0064]

[0065] Wherein: C2 is the concentration of biogenic amines in the air-dried intestines of the control group (mg / kg); C3 is the concentration of biogenic amines in the air-dried intestines of the test strain (mg / kg).

[0066] result: Figure 4 The present invention is a comparison of the contents of eight biogenic amines in air-dried sausages inoculated with Lactobacillus plantarum SH7 and air-dried sausages not inoculated with Lactobacillus plantarum SH7 (control group) on the 9th day of fermentation. The experimental results show that Lactobacillus plantarum SH7 has the ability to significantly reduce biogenic amines (P<0.05), and has different degrees of degradation effects on the eight biogenic amines, among which the degradation rates of putrescine, cadaverine and histamine are more significant, which are 70.46%, 61.11% and 51.41% respectively, and the total biogenic amine degradation rate reaches 46.40%. It has significant amine reduction characteristics and can be used as a fermentation agent to reduce the content of biogenic amines in the production of fermented meat products.

[0067] 2. Lactobacillus plantarum SH7 produces signal molecule AI-2

[0068] After Lactobacillus plantarum SH7 was inoculated into MRS medium for activation for 3 generations, lactic acid bacteria culture solution, V.harveyiBB170 culture solution, AB culture medium and MRS liquid culture medium were prepared. After centrifugation at 8000r / min (4°C) for 5min, the bacterial mud was discarded and filtered with a 0.22μm sterile membrane to remove impurities, and the test strain CFS, positive control, negative control and medium control were obtained. The sample to be tested, positive, negative and medium controls were mixed with the diluted V.harveyi BB170 bacterial solution at 1:100 (v / v) and continued to be shaken and cultured. Within 0-6h, the fluorescence intensity value was measured every 30min. The fluorescence intensity of each sample was measured when the fluorescence intensity value of the negative control reached the lowest point (about 3.0 hours), and the relative fluorescence intensity was calculated to represent the activity of the signal molecule AI-2.

[0069] Relative fluorescence intensity calculation formula:

[0070] Formula (1): Relative fluorescence intensity of positive control group = fluorescence intensity value of positive control / fluorescence intensity value of negative control;

[0071] Formula (2): relative fluorescence intensity of the test group = fluorescence intensity value of the test sample / fluorescence intensity value of the medium control.

[0072] Identification of high-yield AI-2 lactic acid bacteria: The strain was identified by 16S rRNA molecular biology, with primers 27F (5'-AGAGTTTGATCCTGGCTCAG-3') and 1492R (5'-GGTTACCTTGTTACGACTT-3'). Sequence alignment was performed on the website of the National Center for Biotechnology Information (NCBI) (https: / / blast.ncbi.nlm.nih.gov / Blast.cgi) to obtain the identification results.

[0073] from Figure 1 It can be seen that the ability of Lactobacillus plantarum SH7 to produce signal molecule AI-2 is 9.75, and the ability of Lactobacillus sakei MDJ6 to produce signal molecule AI-2 is 4.46.

[0074] 3. Diamine oxidase produced by Lactobacillus plantarum SH7

[0075] Take 200 μL of plant lactobacillus SH7 glycerol bacteria producing signal molecule AI-2 in 10 mL MRS medium, culture at 37 ° C for 16 hours, centrifuge twice at 4 ° C, 8000 r / min for 10 min, extract protein from supernatant with 70% ammonium sulfate, place at 4 ° C for 1 hour to fully extract, discard the supernatant, dissolve the obtained protein in an equal volume of phosphate buffer, and determine the protein concentration and extracellular diamine oxidase activity; the above centrifuged bacterial mud is washed twice with phosphate buffer and resuspended in an equal volume of phosphate buffer, add 0.02 mmol / L of protease inhibitor phenylmethylsulfonyl fluoride, and break the cells on an ultrasonic disruptor under ice bath, 3s on, 3s off, alternating the breaking cycle for a total of 15 minutes. The broken cells are centrifuged at 4 ° C, 13000 r / min for 10 min, protein concentration and intracellular diamine oxidase activity. The protein content is determined using the Bradford protein content detection kit (Shanghai Jingkang Bioengineering Co., Ltd.).

[0076] like Figure 2 As shown, both lactic acid bacteria strains had amine oxidase activity both inside and outside the cells, especially Lactobacillus plantarum SH7, whose intracellular diamine oxidase activity (615.24 U / g protein) was significantly higher than that of the other lactic acid bacteria (P<0.05), and its intracellular diamine oxidase activity was also higher than that of the other lactic acid bacteria (72.39 U / g protein; P>0.05), indicating that this strain has a strong ability to reduce cadaverine, putrescine and histamine and has a certain potential to reduce amines in air-dried sausage.

[0077] In summary, the amine reduction effect and diamine oxidase activity of Latilactobacillus sakeie MDJ6 were significantly lower than those of L. plantarum SH7. At the same time, Lactobacillus plantarum SH7 had the ability to produce high signal molecule AI-2. The expression of AI2 in Lactobacillus plantarum strain SH7 was related to the ability to produce diamine oxidase and the ability to reduce biogenic amines.

[0078] The AI-2 signal molecule precursor 4,5-dihydroxy-2,3-pentanedione (4,5-dihydroxy-2,3-pentanedione) was exogenously added at 0, 300, 600 and 900 nmol / L. The specific steps were as follows: Lactobacillus plantarum SH7 was inoculated into MRS medium and cultured for 2 generations, and then inoculated into MRS medium containing AI-2 signal molecule precursor (4,5-dihydroxy-2,3-pentanedione) at concentrations of 0, 300, 600 and 900 nmol / L and cultured for 72 hours. Lactic acid bacteria culture fluid, V. harveyi BB170 culture fluid, AB culture medium and MRS liquid culture medium were prepared every 12 hours. After centrifugation at 8000 r / min (4°C) for 5 minutes, the bacterial mud was discarded, and 0.22 μL of sterile membrane was used to filter and remove impurities to obtain the sterile supernatant of the test strain culture fluid and the positive control (V. harveyi BB170 culture medium sterile supernatant), negative control (AB culture medium sterile supernatant), medium control (MRS liquid culture medium sterile supernatant). The sample to be tested, positive, negative, medium control and diluted V.harveyi BB170 culture medium are mixed at 1:100 (v / v) and continued to shake and culture. Within 0-6h, the fluorescence intensity value is measured every 30min. The fluorescence intensity of each sample is measured when the fluorescence intensity value of the negative control reaches the lowest point (at 3.0 hours), and the relative fluorescence intensity is calculated to represent the activity of the signal molecule AI-2.

[0079] Effect of Lactobacillus plantarum SH7 on the diamine oxidase production capacity ( Figure 5 ) and the ability to degrade putrescine, cadaverine and histamine ( Figure 6 ) and its effect on the production of signal molecule AI-2 by Lactobacillus plantarum SH7 are shown in Table 3.

[0080] Table 3 Effects of exogenous addition of AI-2 precursors on the production of signal molecule AI-2 by Lactobacillus plantarum SH7

[0081]

[0082] Note: Lowercase letters indicate significant differences among different treatment groups at the same culture time (P<0.05).

[0083] Capital letters indicate significant differences among different culture times in the same treatment group (P<0.05).

Claims

1. A Lactobacillus Plantarum expressing a signal molecule AI-2, characterized in that: The plant lactobacillus is named as Lactobacillus plantarum SH7, with a preservation number of CGMCC NO.28113, and is deposited in the China General Microorganism Collection Center on August 7, 2023.

2. A microbial preparation containing the plant lactobacillus according to claim 1.

3. Use of the plant lactobacillus according to claim 1 or the microbial preparation according to claim 2 in degrading biogenic amines.

4. The use according to claim 3, characterized in that: The biogenic amines are putrescine, cadaverine and histamine.

5. Use of the plant lactobacillus according to claim 1 or the microbial preparation according to claim 2 in degrading biogenic amines or in producing diamine oxidase.

6. The use according to claim 5, characterized in that: The diamine oxidase is an intracellular diamine oxidase or an extracellular diamine oxidase.

7. Use of the plant lactobacillus according to claim 1 or the microbial preparation according to claim 2 in the preparation of fermented sausage products.

8. A method for degrading biogenic amines, characterized in that: The plant lactobacillus according to claim 1 is reacted in a reaction solution containing biogenic amines at 37° C. for 3 days.

9. A method for producing diamine oxidase, characterized in that: The plant lactobacillus according to claim 1 is cultured in MRS medium at 37° C. for 16 hours.

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